CA2065415A1

CA2065415A1 - Magnetic resonance imaging agents

Info

Publication number: CA2065415A1
Application number: CA002065415A
Authority: CA
Inventors: Raghavan Rajagopalan; Muthunadar P. Periasamy
Original assignee: Individual
Current assignee: Mallinckrodt Inc
Priority date: 1989-09-05
Filing date: 1990-03-05
Publication date: 1991-03-06
Also published as: AU646393B2; JPH04507401A; EP0490897A1; WO1991003261A1; AU5535190A

Abstract

ABSTRACT OF THE DISCLOSURE

Novel magnetic resonance imaging agents comprise complexes of paramagnetic ions with a m i n o a 1 k y 1 a m i d e d e r i v a t i v e s o f diethylenetriaminepentaacetic acid ("DTPA") or ethylenediaminetetraacetic acid ("EDTA") or other polyaminocarboxylic or cyclic polyaminocarboxylic chelating agents. These novel imaging agents are characterized by excellent NMR image-contrasting properties and by high solubilities in physiological solutions. A
novel method of performing an NMR diagnostic procedure involves administering to a warm-blooded animal an effective amount of a complex as described above and then exposing the warm-blooded animal to an NMR imaging procedure, thereby imaging at least a portion of the body of the warm-blooded animal.

Description

~'~91~03261 '~ PCT/~S90/01196 NOVEL MAGNETIC RESONANCE IMAGING AGENTS

Backaround of the Invention This invention relates to nuclear magnetic resonance (NMR) imaging and, more particularly, to methods and compositions for enhancing NMR imaging.
The recently developed technique of NMR imaging encompasses the detection of certain atomic nuclei utilizing magnetic fields and radio-frequency radiation. It is similar in some respects to x-ray computed tomography (CT) in providing a cross-sectional display of the body organ anatomy with excellent resolution of soft tissue detail. As currently used, the images produced constitute a map of the proton density distribution and/or their relaxation times in organs and tissues. The technique of NMR imaging is advantageously non-invasive as it avoids the use of ionizing radiation.
While the pheno~enon of NMR was discovered in 1945, it is only relatively recently that lt has found application as a means of mapping the internal structure of the body as a result of the original suggestion of Lauterbur (Nature, 242, l90-l9l (1973)).
The funda~ental lack of any known hazard associated with the le ^l of the magnetic and radio-frequency fields that -e e~ployed renders it possible to ~ake repeated scans on vulnerable individuals. In additional to standard scan planes (axial, coronal, and sagittal~, oblique scan planes can also be selected.

W~91/03261 2 ^ PCTtUS90/01196 In an NMR experiment, the nuclei under study in a sample (e.g. protons) are irradiated with the appropriate radio-frequency (RF) energy in a highly uniform magnetic field. These nuclei, as they relax, subsequently emit RF at a sharp resonance frequency.
The resonance frequency of the nuclei depends on the applied magnetic field.
According to known principles, nuclei with appropriate spin, when placed in an applied magnetic field (B, expressed generally in units of gauss or Tesla (lO' gauss)) align in the direction of the field.
In the case of protons, these nuclei precess at a frequency, f, of 42.6 MHz at a field strength of 1 Tesla. At this frequency, an RF pulse of radiation will excite the nuclei and can be considered to tip the net magnetization out of the field direction, the extent of this rotation being determined by the pulse duration and energy. After the RF pulse, the nuclei "relax" or return to equilibrium with the magnetic field, emitting radiation at the resonant frequency.
The decay of the emitted radiation is characterized by two relaxation times, i.e., T1, the spin-lattice relaxation time or longitudinal relaxation time, that is, the time taken by the nuclei to return to equilibrium along the direction of the externally applied magnetic field, and T" the spin-spin rslaxstion time associated with the dephasing of the initially coherent precession of individual proton spine. These relaxation 1:imes have been established for various fluids, organs and tissues in different species of mammals.
In NMR imaging, scanning planes and slice thicknesses can be selected. This selection permits hiqh quality transverse, coronal and sagittal images to be obtained directly. The absence of any moving parts in NMR imaging equipment promotes a high reliability.
It is believed that NMR imaging has a greater potential ` ~9l/0326l PCT/~!S90/01196 than CT for the selective examination of tissue characteristics in view of the fact that in CT, x-ray attenuation coefficients alone determine image contrast, whereas at least five separate variables (T~, T2, proton density, pulse sequence and flow) may contribute to the NMR signal. For example, it has been shown (Damadian, Science, 171, 1151 (1971)) that the values of the T, and T2 relaxation in tissues are generally longer by about a factor of 2 in excised specimens of neoplastic tissue compared with the host tlssue.
By reason of its sensitivity to subtle physicochemical differences between organs and/or tissues, it is believed that NMR may be capable of differentiating different tissue types and in detecting diseases which induce physicochemical changes that may not be detected by x-ray or CT which are only sensitive to differences in the electron density of tissue.
As noted above, two of the principal imaging parameters are the relaxation times, T, and T,. For protons (or other appropriate nuclei), these relaxation times are influenced by the environment of the nuclei (e.g., viscosity, temperature, and the like). These two relaxation phenomena are essentially mechanisms whereby the initially impsrted radio frcquency energy is dissipated to the surrounding environment. The rate of this energy loss or relaxation can be influenced by certain other nuclei which are paramagnetic. Chemical compounds incorporating these paramagnetic nuclei may substantially alter the T, and T2 values for nearby protons. The extent of the paramagnetic effect of a given chemical compound is a function of the environment within which it finds itself.

9l/0326l ~ pCT/~S~01l~

In general, paramagnetic divalent or trivalent ions of elements with an atomic number of 21 to 29, 42 to 44 and 58 to 70 ha~e been found effective as NMR
image contrasting agents. Suitable such ions include chromium (III), manganese (II), manganese (III), iron (III), iron (II), cobalt (II), nickel (II), copper (II), praseodymium (III), neodymium (III), samarium (III) and ytterbium (III) Because of their very strong magnetic moments, gadolinium (III), terbium (III), dysprosium (III), holmium (III) and erbium (III) are preferred. Gadolinium (III) ions have been particularly preferred as NMR image contrasting agents.
Typically, the divalent and trivalent paramagnetic ions have been administered in the form of complexss with organic complexing agents. Such complexes provide the paramagnetic ions in a soluble, non-toxic form, and facilitate their rapid clearance from the body following the imaging procedure. Gries et al., U.S.
patent 4,647,447, disclose complexes of various paramagnetic ions with conventional aminocarboxylic acid complexing agents. A preferred complex disclosed by Gries et al. is the ~omplex of gadolinium (III) with diethylenetriaminepentaacetic acid ("DTPA"). ~his complex may be represented by the formula:

~091/03261 ~ P CT/ US90/01196 CH2-CH.-N
CH~-CO0--OOC-CH2-N Gd' CH2-cH2-N

15 _ Paramagnetic ions, such as gadolinium (III), have been found to form strong complexes with DTPA. These complexes do not dissociate substantially in physiological aqueous fluids. The complexes have a net charge of -2, and generally are administered as soluble salts. Typical such salts are the sodium and N-methylglucamine salts.
The administration of ionizable salts is attended by certain disadvantages. These salts can raise the ~n 25 ViVQ ion concentration and cause localized disturbanc~s in osmolality, which in turn, can lead to edema and other undesirable reactions.
Effort:s have been made to design non-ionic paramagnet~c ion complexes. In general, this goal has been achieved by converting one or more o~ the free carboxylic acid groups of the complexing agent to neutral, non-ionizable groups. For example, S.C. Quay, in U.S. patents 4,687, 658 and 4,687,659, discloses alkylester and alkylamide derivatives, respec:ively, of DTPA complexes. Similarly, published West German applications P 33 24 235.6 and P 33 24 236.4 disclose mono- and polyhydroxyalkylamide derivatives of DTPA and their use as complexing agents for paramagnetic ions.

~ -91/03261 ~r~ P~T/US90/01196 Published Australian Patent Application No. 78995j87 also describes amide complexing agents useful in N~R
and x-ray procedures.
The nature of the derivative used to convert carboxylic acid groups to non-ionic groups can have a significant impact on tissue specificity. Hydrophilic complexes tend to concentrate in the interstitial fluids, whereas lipophilic complexes tend to associate with cells. Thus, differences in hydrophilicity can lead to different applications of the compounds. See, for example, Weinmann et al., A~R, l~, 679 (Mar. 1984) and ~rasch et al., AJR, l~, 625 (Mar. 1984).
Thus, a need continues to exist for new and structurally diverse non-ionic complexes of paramagnetic ions for use as NMR imaging agents.

Summary of the Invention The present invention provides novel complexing agents and complexes of complexing agents with paramagnetic ions. The complexes are represented by either of the following formulae:

I. O O
~ R'-l-CH C~,- C-R
O N~A-N O M
11 / \ 11 R'-C-CH, CH,- C-R1 _ _ wherein A is -CHR'-CHR'- or ~'~91/03261 PCT/US9OtO1196 CH2-C-R' -CHzCH NCH.CH2-M-Z is a paramagnetic ion of an element with an atomic number of 21-29, 42-44 or 58-70, and a valence, Z, of +2 or +3, Rl groups may be the same or different and are selected from the group consisting of -O~and 1 0 Rs ~N(CH2)n~ N
R~ R6 wherein R', R5 and R" may be the same or different and are hydrogen, alkyl, hydroxy, alkoxy, mono- or poly-hydroxyalkyl, alkoxyalkyl, aminoalkyl or acylaminoalkyl wherein the carbon-containing portions contain from 1 to about 6 carbon atoms or R5 and R6, together with the adjacent nitrogen, can form a heterocyclic rinq of five, six or seven members wherein O to 1 members other than the nitrogen are O
-O-, -S-, -S- or -N-O R~
and which members are unsubstituted or substituted by hydroxy, alkyl, aryl, hydroxyalkyl, aminoalkyl, 30 aminoaryl, alkylamino, or carbamoyl wherein the substituents contain from 1 to about 6 carbon atoms, n is between l and 6;
R2 and R' nay be the same or different and are hydrogen, alkyl having from 1 to abo~t 6 carbon atoms, 35 phenyl or benzyl or R2 and R' together with the ~ `91~03261 ~ PCT/~'S90/01196 intervening carbon can form a hydrocarbon ring of 5, 6 or 7 members;
and wherein Z of the Rl groups are -O~and the remainder of the R' groups are Rs ~N(CH2)n~ N

Alternatively, the complexes are represented by the following formula:
II.
O O
R' -CH2C CH2-CH2 CH2C-R' \/ \/
N N
CH2 (CH-R').
l l M' CHz CH2 N N
R' -CH2C CH2-( fH)~ CH2C-R' 0 R' O

wherein M' is a paramagnetic ion of an element w1th an atomic number of 21-29, 42-44 or 5E3~70, and a valence Z
of ~2 or +3, r and s are integers between l and 6 and can be ; the same or different, J the R' groups can be the same or di~ferent and are selected from the group consisting of hydrogen, alkyl having from l to 6 carbon atoms and mono or poly-hydroxyalkyl, the alkyl portion having from l to 6 carbon atoms, )91/03261 ~ ;r~ PCr~l~S90/01196 the R groups can be the same or different and are selected from the group consisting of -O- and ~R2 ~
- N
R-wherein R2 is selected from th,e group consisting of (CH2CH20)p- R3 and (CH2)q- N and R4 is selected from the group consisting of H, R2 and R' , wherein R' , R5 and R6 can be the same or different and are selected from the group consisting of hydrogen, alkyl, hydroxy, alkoxy, ~ono- or poly-hydroxyalkyl, alkoxyalkyl, aminoalkyl or acylamino-alkyl, wherein the carbon-containing portions contain from 1 to about 6 carbon atoms or Rs and R6 , together with the adjacent nitrogen, can for~ a heterocyclic ring of five, six or seven memhers wherein 0 to 1 members other than the nitrogen are -O-, -S-, -S- or -N- and which members are unsubstituted or Il ]1., substituted by hydroxy, alkyl, aryl, hydraxyalkyl, aminoalky:l, aminoaryl, alkylamino, or carbamoyl wherein the subst:ituents contain from 1 to about 6 carbon atoms, p and q can be the same or different and represent integers between 1 and 6, 3s and wherein z of the R' groups a,re -0- and the remainder of the R' groups are -N

~9l/0326l ~ ~ J ~ J ~ ~5 PCT/US90/01196 Also disclosed is a method of performing an NMR
diagnostic procedure which involves administering to a warm-blooded animal an effective amount of one of the above-described complexes and then exposing the warm-blooded animal to an NMR imaging procedure, therebyimaging at least a portion of the body of the warm-blooded animal.

Detailed Description of the Invention The complexing agents employed in this invention are derivatives of well-known polyaminocarboxylic acid chelating agents, such as DTPA and ethylenediamine-tetraacetic acid ("EDTA") and cyclic polyaminocarboxylic acid chelating agents such as 1,4,7,10-tetraazacyclododecane N,N',N'',N'''-tetra acetic acid ("DOTA"). In one class of these derivatives, free carboxylic acid qroups of the chelating agent (those not involved in bond formation with the paramagnetic ion) are converted to aminoalkylamide groups of the formula:

Il /
-C-N-(CH,)~ -N
R~ R' For exampl~e, if the polyaminocarboxylic acid chelating agent is DTPA, and the paramagnetic ion is trivalent, two of the carboxylic acid groups will be derivatized to the aminoalkylamide form. Likewise, if the paramagnetic ion is divalent, three of the carboxylic acid groups of DTPA or two of the carboxylic acid groups of EDTA will be derivatized to the aminoalkylamide form. When these complexing agents are reacted with a divalent or trivalent paramagnetic ion, '91/03261 ~ PCT/~'S90/01196 the resulting complexes are substantially non-ionic as evidenced by very low electrical conductivity.
Examples of types of aminoalkylamide derivatives useful 2S complexes include those wherein the aminoalkylamide group is O O
Il 11 -CNH(CH2) n~ N(CH3)2, - CNH(CH2)n-N(CH2CH2OH)2 or O
11 / \
-CNH(CH2)n -N X , wherein X is O, S or N, \_/
unsubstituted or substituted. In a preferred embodiment, the aminoalkylamide group is a morpholinoalklylamide.
An alternative class of compounds encompassed by this invention, includes cyclic polyamino carboxylic acid chelating agents, such as DOTA and TRITA and represented by the general formula:

O O
R' -CHzC CH2-CH2 CH2C-R' \ / \ /
N N
1~! (CH-R').
CH, CHz N N
R1 -CH,C CH2-(CH) r CH2C-R' Il l 11 O R' O
In these agents, free carboxylic acid groups are 91/03261 ~ r.~ PCI/IIS9O/01196 O R2' converted to -C-N , wherein R- is either R~ /
(CHzCHzO)p-R' or (CHz)~- N . As with the first ~R6~

class of agents described above, if the paramagnetic ion is trivalent, one of the carboxylic acid groups will be derivatized to the aminoalkylamide form, and if the paramagnetic ion is divalent, two of the carboxylic acid groups will be derivatized.
Examples of types of derivatives useful as 15 complexes include those wherein the amino alkylamide group is:
O O
-C-NH-(CHz)p- N O or ~C~N~(CH2)qOCH~
\ _ / I
CH, In a preferred embodiment, the aminoalkylamide group is morpholinoalkylamide.
The aminoalkylamide derivatives of the chelatinq agents may be prepared by conventional amide-forming reactions. In general, they are prepared by reacting a stoichiomel:ric amount of an aminoalkylamine with a reactive derivative of the polyaminocar~oxylic acid chelating agent or cyclic polyamlnocarboxylic acid chelating agent under amide-forming conditions. Such reactive derivatives include, for example, anhydrides, mixed anhydrides and acid chlorides. To make complexing agents represented by formula I above, the aminoalkylamine has the general formula:
R~
HN(CH,)~ -N
R- R~

03261 ~ r;~ r~ PCT/~'S90/01196 To make complexin~ agents represented by formula II
above, the aminoalkyla~lde has the general for~ula:
Rs HN~(CH~)q~ N or HN-(CH.CH.O)p-R' R' \R6~ R' In one embodiment for making any of these complexing agents, the reaotions are conducted in an organic solvent at an elevated temperature. Suitable solvents include those in which the reactants are sufficiently soluble and which are substantially unreactive with the reactants and products. Lower aliphatic ketones, ethers, esters, chlorinated hydrocarbons, benzene, toluene, xylene, lower aliphatic hydrocarbons, som~ lower aliphatic alcohols and the like may advantageously be used as reaction solvents.
Examples of such solvents are isopropanol, acetone, methylethyl ketone, diethylketone, methyl acetate, ethyl acetate, chloroform, methylene chloride, dichloroethane, hexane, heptane, octane, decane, and the like. If an acid chloride derivative of the polyaminocarboxylic acid is used as the starting material, t:hen the reaction solvent advantageously is one which does not contain reactive functional groups"
such as hydroxyl groups, as these solvents can react with the acid chlorldes, thus producing unwanted by-products.
The reaction temperature may vary widely, depending upon the starting materials employed, the nature of the reaction solvent and other reaction conditions. Such reaction temperatures may range, for example, fro~ about 25 C to about 80 C, preferably from about 25 C to about 50 C.

~'~91/03261 ~ ,3~ PCT/US90/01196 Following reaction of the reactive polyaminocarboxylic acid derivative with the aminoalkylamide, any remaining anhydride or acid chloride groups can be hydrolyzed to the carboxylate S groups by adding a stoichiometric excess of water to the reaction mixture and heating for a short time.
The resulting aminoalkylamide compound is recovered from the reac~ion mixture by conventional procedures. For example, the product may be precipitated by adding a precipitating solvent to the reaction mixture, and recovered by filtration or centrifuqation.
The paramagnetic ion is combined with the aminoalkylamide compound under complex-forming conditions. In general, any of the paramagnetic ions referred to above can be employed in making the complexes of this invention. The complexes can conveniently be prepared by mixing a suitable oxide or salt of the paramagnetic ion with the complexing agent in aqueous solution. To assure complete complex formation, a slight stoichiometric excess of the complexing agent ~ay be used. In addition, an elevated temperature, e.g., ranging from about 20 C to about lO0 C, preferably from about 40 C to about 80 C, may be employed to insure complete co~plex ~ormatian.
Generally, complete complex formation will accur within a period from a few minutes to a few hours after mixing. The complex may be recovered by precipitation using a precipitating solvent such as acetone, and further purified by crystallization or chromatography, if desired.
The novel complexes of this invention can be formulated into diagnostic compositions for enteral or parenteral administration. These compositions contain 91/03261 ,~ fl ~ PCT/~IS90/01196 an effective amount of the paramagnetic ion complex along with conventional pharmaceutical carriers and excipients appropriate for the type of administration contemplated. For example, parenteral formulations advantageously contain a sterile aqueous sclution or suspension of from about 0.05 to l.OM of a paramagnetic ion complex according to this invention. Preferred parenteral formulations have a concentration of paramagnetic ion complex of O.lM to 0.5M. Such solutions also may contain pharmaceutically acceptable buffers and, optionally, electrolytes such as sodium chloride. The compositions advantageously can contain one or more physiologically acceptable, non-toxic cations in the form of a gluconate, chloride or other suitable organic or inorganic salt, including suitable soluble complexes with a chelant/liqand, to enhance safety. The chelant/ligand desirably is derived from DTPA or EDTA. Such ligands include the ligands set forth above used to complex the paramagnetic and or heavy metals to provide the complex formulations of this invention. Advantageously, the cation-ligand complex is provided in amounts ranging from about 0.1 mole % to about 15 mole % of the ligand-metal complex.
Such physiologically acceptable, non-toxi~ c~tions include sodium ions, calcium ions, magnesium ions, copper ions, zinc ions and the like. Calcium ions are preferred. A typical single dosage formulation for parenteral administration has the followinq composition:

Gadolinium DTPA-di(morpholinoethylamide) 330mg/ml Calcium DTPA-tri(morpholinoethylamidej 14mg/ml Distilled Water q.s. to l ml pH 7.3 + O.l Parenteral compositions can be injected directly or mixed with a large volume parenteral composition for systemic administration.
For~ulatians for enteral administration may vary widely, as is well-known in the art. In general, such formulations are liquids which include an effective amount of the paramagnetic ion complex in aqueous solution or suspension. Such enteral compositions may optionally include buffers, surfactants, thixotropic agents, and the like. Compositions for oral administration may also contain flavoring agents and other ingredients for enhancing their organoleptic qualities.
The diagnostic compositions are administered in doses effective to achieve the desired enhancement of the NMR image. Such doses may vary widely, depending upon the particular paramagnetic ion complex employed, the organs or tissues which are the subject of the imaging procedure, the NMR imaging equipment being used, etc. In general, parenteral dosages will range fr~m about O.Ol tn about l.0 m~ol of paramagnetic ion complex per kg of patient body weight Preferred parenteral dosages range from about 0.05 to about 0.5 mmol of paramagnetic ion complex per kg of patient body J weight. Enteral dosages generally range from about O.S
to about lO0 mmol, preferably from about l.0 to about 20 mmol of paramagnetic ion complex per kg of patient body weight.
The novel NMR i~age contrasting agents of this invention possess a unique combination of desirable 91/03261 ~ P ~ /US90/01196 features. The paramagne~ic ion complexes exhibit an unexpectedly high solubility in physiological fluids, notwithstanding their substantially non-ionic character. This high solubility allows the preparation of concentrated solutions, thus minimizing the amount of fluid required to he administered. The non-ionic character of the complexes also reduces the osmolality of the diagnostic compositions, thus preventing undesired edema and other side effects.
As illustrated by the data presented below, the compositions of this invention have very low toxicities, as reflected by their high LD~o values. The low toxicity of these complexes is thought to result, in part, from the high stability constant of the complexes. The aminoalkyl moieties provide additional sites for the formation of coordination bonds with the paramagnetic metal ion, thus strengthening the coordination complex. Therefore, the aminoalkyl groups not only neutralize the free carboxylic acid groups of the complexing agent, but they also participate in the formation of the complexes.
~ he diagnostic compositions of this invention are used in the conventional manner. The compositions may be adminis,tered to a warm-blooded animal e~ther systemically or locally to the organ or tissue to be imaged, and the animal then subjected to the NM~
imaging procedure. The compositions have been found to enhance the magnetic resonance images obtained by these procedures. In addition to their utility in magnetic resonance imaging procedures, the complexin~ agents of this invention may also be employed for delivery of radiopharmaceuticals or heavy metals for x-ray contrast into the body.

~v~ 91/0326~ P~r/US90/01196 The invention is further illustrated by the followin~ examples, which are not intended to be limiting.

Example 1 Preparation of a DTPA-Morpholinoethylamide Gd Complex A DTPA morpholinoethylamide Gd complex was prepared in two steps as shown below:
_ O
/ \
_ N O
\_/
----N O iPrOH
\_ O -- >
CO~H \ / \ +
N O N
\_/ I
O

N
- CONH N O
\_/
r----N
I Gd,O, CO2H - CO,H
N
- CONH N O
\ _/

w- 91/03261 ,~ 3 PCr/l,'S90/01 19fi -Co, _ N
r - CONH N O
CO N Gd' --COz N
- CONH N O
_ \_/ _ The preparation of [N,N"-bis[N-2((4-morpholino)-ethyl)carbamoyl~ diethylenetriamine-N,N',N"-triacetlc acid specifically was carried out by the following steps:
A mixture of DTPA-dianhydride (36g) and aminoethyl-morpholine (27g) in isopropanol (250mL) was stirred at ambient temperature for 16 hours. The orange solution was filtered through a fine porosity sintered glass funnel to remove undissolved impurities.
The clear Eiltrate was poured onto ether (2L) and the mixture stirred vigorously for 1 hour. The granular precipitate was collected by filtration, washed with ether (3XlL), and dried. The pale tan solid thus obtained was sufficiently pure for the next step.
Yield 60g (85%). Anal. Calcd. for C~6~l~7N~0lo x O.3H2O:
C, 50.13; H, 7.64; N, 15.74. Found: C, 50.46; H, 7.80; N, 15.69. The preparation of [N,N"-bis[N-2((4-morpholino)ethyl)-carbamoylmethyl]diethylene triamine-N,N',N"-triaceto]-gadolinium(III) ~onohydrate was carried out as follows:
A mixture of the ligand (13.8g) and gadolinium oxide (3.6g) in deionized water (70mL) was heated at 65-70 C (water bath) for 4 hours and stirred at ambient temperature for 16 hours. The orange solution ~91/03261 PCT/US90/Oll96 was then filtered through a fine porosity sintered glass funnel to remove undissolved impurities. The clear filtrate was then poured onto acetone (2L) and the mixture stirred vigorously for 30 minutes. Acetone was decanted off and the gummy residue was further treated with acetone (lL). The gu~ began to solidify and after 4 hours, the precipitate was collected by filtration, washed well with acetone (3XlL), dried, and recrystallized from methanol/tetrahydrofuran to afford the complex. Yield, lOg. (59%). Anal. Calcd. for C26H..H,O,oGd x 1 H~0: C, 39.54; H, 5.83; N, 12.42; Gd, 19.89. Found: C, 39.51; H, 5.76; N, 12.47; Gd. 19.79.

F,xamDle 2 Preparation of 1.17-~is~N.N-di~ethvl~-4.14-dioxo-3.6.9,12.15-pentaaza-6.9.1Z-tris~carboxyethyl)heptadecane (1) A stirred suspension of DTPA-dianhydride (7.0g., 19.6 mmol) in isopropanol (35 mL) was treated with N,N-dimethylethylenediamine (3.8g, 43.1 ~mol). The entire mixture was stirred at a~bient temperature for about 18 hours. The reaction mixture was filtered to remove insoluble impurities. The clear filtrate was poured into anhydrous ether (2L) and the mixturc ~stirred vigorously for 1 hour. 'rhe ~'ine so]id was collected by ~iltration, washed with ether (3x200 mL), and dried at 50 C to constant weight to yield a colorless solid, 9.0g (82.0%).
Anal. Calcd. for C2,H1,N70,Ø5H2O (MW 542.63);
C,48.71%; H,8.12~; N,18.08%. Found: C,48.50%; H,8.4%, N,18.09%.

WO91/03261 ~ PCT/~'S~0/01196 Example 3 Preparation of ~N.N"-Bis r N-2(~dimethylamino~ethyl~ bamoylmethyl]-diethylenetriamine-N.N'N"-triaceto~aadoliniu~

A mixture of the ligand (11.50g, 0.021 mol) and Gd~0, (3.62g., 0.01 mol) in deionized water (50 mL) was heated. After the reaction was over, the filtrate was poured into acetone (lL). The solvent was decanted off and the residue was further treated with fresh acetone (lL). The precipitate was collected by filtration and it was recrystallized from tetrahydrofuran/methanol to yield the complex as a colorless solid, 3.8g (30.0~).
Anal. Calcd. for C,~H,oN7O~GdØ5H2O (MW 697.87):
C,3~.21%: H,5.79%; N,14.18%; Gd.22.72%. Found:
C,38.54%; H,6.19%; N,13.99%; Gd,21.79~o.

Example 4 Preparation of 1,17-Bis~4-thiomorpholino)-4,14,dioxo-3.6.9.12.15-pentaaza-6.9.12-tris~carboxymethyl~heptadecane ~4) A stirred suspension of DTPA-dianhydride (7.14g, 0.02 mol) in isopropanol ~50 mL) was treated with freshly distilled aminoethylthiomorpholine (6.3g, 0.044 mol). The entire mixture was stirrad at ambient temperature for about 16 hours. The reaction mixtur~
2S was filtered to remove insoluble impurities. Tha clear filtrate was taken to dryness. The gummy residue was purified by flash chromatography over reverse phase (C-18) column. This material was used as such for metal complexation.

~'~9l/03261 ~ PCT/US9n/01196 Example 5 Preparation o~ (N.N"-~isrN-2(~4-thiomorpholino)ethyl~car~amoylmethyll-diethylenetriamine-N.N'.N"-triaceto~qadolinium(III) A mixture of the ligand (7.0g, 10.8 mmol) and Gd.O, (1.86g, 5.1 mmol) in deionized water (35 mL) was heated at 67-70C for 18 hours. After the reaction was over, the filtrate was poured into acetone (2L) and the mixture stirred vigorously for 30 minutes. After 1 hour, acetone was decanted off and the gummy residue was further treated with acetone (lL). The precipitate was collected, washed with acetone and recrystallized twice from acetone/water to give 4.5g of colorless solid.
Anal. Calcd. for C2~H"N7ORS,Gdx1.5H2O: C,37.54, H,5.66; N,11.79; S,7.70; Gd.1~.89. Found: C,37.80;
H,5.51; N,11.90; S,7.52; Gd,19.92 Example 6 ~i5i~determination of ~TPA-morPh~linoethylamide Gd co~plex The ac:ute intravenous toxicity of the compound of Example l was determinqd as follows: ICR mice, at 1 to 4 per dose level, received single lntravenous injections of the test substance via a lateral tail vein at the rate of approximately 1 ml~minute. The test substances were at concentrations chosen to result in dose volumes of S to 75 ml/kg body weight. Dosing began at a volume of 10 ml/kg. Dose adjustments up or down were made to closely bracket the estimated LD50 with 4 animals per qroup (2 males and 2 females).
Observations of the mice were recorded at times 0, 0.5, l, 2, 4 and 24 hours and once daily thereafter for up ~'~91/03261 PCT/US90/011~6 to 7 days post injection. On the 7th day post injection, the mice were euthanized, weighed and necropsied. Abnormal tissues were noted. At this time a decision was made as to whether any histopathology was to be performed and whether or not the tissues should be retained. Necropsies were also performed on mice expiring after 24 hours post-injection, except for dead mice found on the weekends. The LD50 values, along with 95% CI were calculated using a modified Behrens-Reed-Meunch method. The results for the complex of Example l are reported below:

LD~o: lO.O mmol/kg (no excess ligand, 0.5M solution) LD,o: 17 . 3 mmol/lkg (5% excess ligand as calcium salt, 0.5M solution) Example 7 T,-Relativity Determinations.

T, or longitudinal relaxation times were measured at 90MHz for the complex in 25%D20/75%H20 mixture at 20mM down to 0.65mM. The T1 is obtained using the spin-echo sequence on the JEOL FX9OQ FT-NMR spectrometer.
The relaxivities were determined by applying linear least-squares fit to the l/T1 versus conc~ntration data.
The target correlation coefficiQnt (r~) is about O.g990.
All 1'C NMR spectra were taken on a JEOL EX90QQ FT-NMR Spectr-ometer and all 1H NMR Spectra were taken on a Varian Gemini 300 FT-NMR Spectrometer at room temperature. The IR spectrum was done on a Perkin-Elmer IR 'ipectrophotometer 727. Elemental analyses were performed by Galbraith Laboratories of Knoxville, TN, and Atlantic Microlab of Norcros, GA. pH
measurements were made on a Corning Ion Analyzer 250 meter using a Corning combination electrode. All W~91/03261 ~ PCT/VS90/01196 spectrophotometric measurements were made on a varian CARY 2215 uv/vis spectrophotometer at room temperature.
All computer calculations were done on an I~M Personal System 2 or an IBM-compatible PC Kaypro.
The relaxation rate for the cnmplex of Example 1 was 5.13 + O.07 mM~'sec~' at 90 MHz and 25 C. The correlation coefficient (r2) was 0.9993.

Exa~le 8 Preparation of l-rN-~2-methoxy)ethyl-N-methyllcarbamoylmethyl-4.7.10-tris(carboxymethyl)-1,4.7,10-tetrazacyclododecane The title ligand is synthesized from DOTA and C~l,OC~,CH,NHCH, by following the general method reported by Krejearek and Tucker (Bioch~ Biophys. Res. Commun.
77 581 (1977)).

~xaTn~le 9 PreDaration of Gadolinium ~III) 1- r N-(2-mç~hoxY~ethyl-N-~ethyl1 carbamoylmethvl-4,7,10-tris(carboxyTnethvl~-1.4.7.10-tetra-azacvclododecane A mixt:ure of the ligand from Example 8 (10 gr.
0.021 mol. and Gd2OI (3.6 gr, 0.01 mol) in deionized water (50 ml) is heated at 100 C until most of the solid is dissolved. The mixture is cooled and filtered through a 0.2 micron filter to remove insolubles present. The filtrate is passed through an ion exchange column and the fractions containing the product are concentrated. The product may be further purified, if necessary, in acccrdance with conventional procedures. The procedure produces the title compound in good yield.

WO91/03261 2~ PCT/~S90/01196 Example l0 Preparation o~ l- r N-2-(4-morpholino)ethyll-carbamoylmethyl 4,7.l0-tris(carboxymethyl)-l.4,7,l0-tetraazacyclododecane The title ligand is synthesized from DOTA and 4-(2-aminoethyl)morpholine by following the method reported by Krejearek and Tucker (Biochem. Biophys.
Res Co~mun. 77 581 (1977).

Example ll Preparation of Gadolinium ~III) l(-rN-2-imorpholino~ethyl carbamovlmethyl 4.7.l0-tri5~carboxymethyll-l.4,7.l0-tetra2acyclododecane The procedure of Example 9 is repeated in all essential details except that the ligand used here is the mono 4-morpholinoethylamide of DOTA, synthesized in Example l0. The procedure produces the title compound in good yield.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A complex having the following formula:

wherein A is -CHR2-CHR3- or M-Z is a paramagnetic ion of an element with an atomic number of 21-25, 27-29, 42-44 or 58-70, and a valence, Z, of +2 or +3, R1 groups may be the same or different and are selected from the group consisting of -0- and wherein R4, R5 and R6 may be the same or different and are hydrogen, alkyl, hydroxy, alkoxy, mono- or poly-hydroxyalkyl, alkoxyalkyl, aminoalkyl and acylaminoalkyl wherein the carbon-containing portions contain from 1 to about 6 carbon atoms or R5 and R6 can together with the adjacent nitrogen form a heterocyclic ring of five, six or seven members wherein 0 to 1 members other than the nitrogen are and which members are unsubstituted or substituted by hydroxy, alkyl, aryl, hydroxyalkyl, aminoalkyl, aminoaryl, alkylamino, or carbamoyl wherein the substituents contain from l to about 6 carbon atoms, and n is between l and 6;
R2 and R3 may be the same or different and are hydrogen, alkyl having from l to about 6 carbon atoms, phenyl or benzyl, or R2 and R' together form a ring of 5, 6 or 7 members;
and wherein Z of the R1 groups are -O- and the remainder of the R1 groups are .

2. The complex of claim l, wherein A is .

3. The complex of claim l, wherein A is -CHR2CHR3-and R2 and R3 are both hydrogen.

4. The complex of claim l, wherein M-z is chromium (III), manganese (II), manganese (III), cobalt (II), nickel (II), copper (II), praseodymium (III), neodymium (III), samarium (III), ytterbium (III), gadolinium (III), terbium (III), dysprosium (III), holmium (III) or erbium (III).

5. The complex of claim 4, wherein M-z is gadolinium (III), terbium (III), dysprosium (III), holmium (III) or erbium (III).

6. The complex of claim 1 wherein n is 2.

7. A complex having the following formula:

wherein A is -CHR2-CHR3- or M-z is a paramagnetic ion of an element with an atomic number of 21-25, 42-44 or 58-70, and a valence, Z, of +2 or +3; R3 groups may be the same or different and are selected from the group consisting of -O- and wherein R', Rs and R6 may be the same or different and are hydrogen, alkyl, hydroxy, alkoxy, mono- or poly-hydroxyalkyl, alkoxyalkyl, aminoalkyl or acylaminoalkyl provided that R4, R5 and R6 are not all hydrogen, wherein the carbon-containing portions contain from 1 to about 6 carbon atoms or R5 and R6 can together with the adjacent nitrogen form a heterocyclic ring of five, six or seven members wherein 0 to l members other than the nitrogen are and which members are unsubstituted or substituted by hydroxy, alkyl, aryl, hydroxyalkyl, aminoalkyl, aminoaryl, alkylamino, or carbamoyl wherein the substituents contain from l to about 6 carbon atoms, and n is between l and 6:
R2 and R3 may be the same or different and are hydrogen, alkyl having from l to about 6 carbon atoms, phenyl, benzyl, or together R2 and R3 form a ring of 5, 6 or 7 members, and wherein Z of the R1 groups are -O- and the remainder of the Rl groups are .

8. The complex of claim 7, wherein A is .

9. The complex of claim 7, wherein A is -CHR2CHR3-and R2 and R3 are both hydrogen.

10. The complex of claim 7, wherein M-z is chromium (III), manganese (II), manganese (III), iron (III), iron (II), cobalt (II), nickel (II), copper (II), praseodymium (III), neodymium (III), samarium (III), ytterbium (III), gadolinium (III), terbium (III), dysprosium (III), holmium (III) or erbium (III).

11. The complex of claim 10, wherein M-z is gadolinium (III), terbium (III), dysprosium (III), holmium (III) or erbium (III).

12. The complex of claim 7, wherein n is 2.

13. The complex of claim 8, wherein n is 2.

14. A diagnostic composition suitable for enteral or parenteral administration to a warm-blooded animal, which comprises an NMR imaging-effective amount of a complex of a paramagnetic ion having the following formula:

wherein A is -CHR2-CHR3- or M-z is a paramagnetic ion of an element with an atomic number of 21-25, 27-29, 42-44 or 58-70, and a valence, Z, of +2 or +3; R1 groups may be the same or different and are selected from the group consisting of -O- and wherein R4, R5 and R6 may be the same or different and are hydrogen, alkyl, hydroxy, alkoxy, mono- or poly-hydroxyalkyl, alkoxyalkyl, aminoalkyl or acylaminoalkyl provided that R4, R5 and R6 are not all hydrogen, wherein the carbon-containing portions contain from 1 to about 6 carbon atoms or R5 and R6 can together with the adjacent nitrogen form a heterocyclic ring of five, six or seven members wherein 0 to 1 members other than the nitrogen are and which members are unsubstituted or substituted by hydroxy, alkyl, aryl, hydroxyalkyl, aminoalkyl, aminoaryl, alkylamino, or carbamoyl wherein the substituents contain from l to about 6 carbon atoms, and n is between 1 and 6;
R2 and R3 may be the same or different and are hydrogen, alkyl having from l to about 6 carbon atoms, phenyl or benzyl, or together R2 and R3 form a ring of 5, 6 or 7 members;
and wherein Z of the R1 groups are -O- and the remainder of the R1 groups are ;

and a pharmaceutically acceptable carrier.

15. The composition of claim 14, wherein A is .

16. The composition of claim 14, wherein A -CHR2CHR3- and R2 and R3 are both hydrogen.

17. The composition of claim 10, wherein M-z is chromium (III), manganese (II), manganese (III), cobalt (II), nickel (II), copper (II), praseodymium (III), neodymium (III), samarium (III), ytterbium (III), gadolinium (III), terbium (III), dysprosium (III), holmium (III) or erbium (III).

18. The composition of claim 17, wherein M-z is gadolinium (III), terbium (III), dysprosium (III), holmium (III) or erbium (III).

19. The composition of claim 18, wherein R1 is and M-z is gadolinium (III).

20. The composition of claim 14, which further contains a pharmaceutically acceptable buffer.

21. The composition of claim 20, which further contains a pharmaceutically acceptable electrolyte.

22. The composition of claim 14, which further comprises a complexing agent of the formula wherein A and R1 are as defined as in claim 14 and said complexing agent is complexed with one or more physiologically acceptable, non-toxic cations.

23. The composition of claim 22, wherein said complexing agent is employed in an amount ranging from about 0.1 to about 15 mole % of the paramagnetic ion-containing complex and is complexed with one or more cations selected from the group consisting of sodium ions, calcium ions, magnesium ions, copper ions, zinc ions and mixtures thereof.

24. The composition of claim 23, wherein said complexing agent is complexed with calcium ions.

25. A method of performing an NMR diagnostic procedure, which comprises administering to a warm-blooded animal an effective amount of a complex of the formula wherein A is -CHR2-CHR3- or M-z is a paramagnetic ion of an element with an atomic number of 21-29, 42-44 or 58-70, and a valence, Z, of +2 or +3; R1 groups may be the same or different and are selected from the group consisting of -0-and wherein R', R' and R6 may be the same or different and are hydrogen, alkyl, hydroxy, alkoxy, mono- or poly-hydroxyalkyl, alkoxyalkyl, aminoalkyl and acylaminoalkyl wherein the carbon-containing portions contain from 1 to about 6 carbon atoms or R5 and R6 can together with the adjacent nitrogen form a heterocyclic ring of five, six or seven members wherein 0 to 1 members other than the nitrogen are -O-, -S-, or and which members are unsubstituted or substituted by hydroxy, alkyl, aryl, hydroxyalkyl, aminoalkyl, aminoaryl, alkylamino, or carbamoyl wherein the substituents contain from 1 to about 6 carbon atoms, and n is between 1 and 6;

R2 and R3 may be the same or different and are hydrogen, alkyl having from 1 to about 6 carbon atoms, phenyl or benzyl or R2 and R3 together can form a 5, 6 or 7 membered ring;
and wherein Z of the R1 groups are -O- and the remainder of the R1 groups are and then exposing the animal to an NMR imaging procedure, thereby imaging at least a portion of the body of the warm-blooded animal.

26. The method of claim 25, wherein A is .

27. The method of claim 25, wherein A is -CHR2CHR3- and R2 and R3 are both hydrogen.

28. The method of claim 25, wherein M-2 is chromium (III), manganese (II), manganese (III), iron (III), iron (II), cobalt (II), nickel (II), copper (II), praseodymium (III), neodymium (III), samarium (III), ytterbium (III), gadolinium (III), terbium (III), dysprosium (III), holmium (III) or erbium (III).

29. The method of claim 28, wherein M-z is gadolinium (III), terbium (III), dysprosium (III), holmium (III) or erbium (III).

30. The method of claim 25, wherein the pharma-ceutically acceptable carrier contains a pharmaceutically acceptable buffer.

31. The method of claim 30, wherein the pharma-ceutically acceptable carrier contains a pharmaceutically acceptable electrolyte.

32. The method of claim 25, wherein the pharma-ceutically acceptable carrier contains a complexing agent of the formula wherein A and R1 are as defined as in claim 25 and said complexing agent is complexed with one or more physiologically acceptable, non-toxic cations.

33. The method of claim 32, wherein said complexing agent is employed in an amount ranging from about 0.1 to about 15 mole % of the paramagnetic ion-containing complex and is complexed with one or more cations selected from the group consisting of sodium ions, calcium ions, magnesium ions, copper ions and zinc ions and mixtures thereof.

34. The method of claim 33, wherein said complexing agent is complexed with calcium ions.

35. A complexing agent of the formula:

wherein A is -CHR2-CHR3- or R1 groups may be the same or different and are selected from the group consisting of -O- and wherein R4 is hydrogen, alkyl, hydroxyalkyl, alkoxyalkyl, aminoalkyl and acylamino wherein the carbon-containing portions contain from l to about 6 carbon atoms;
n is between l and 6;

X is -O-, -S-, , or and which members are unsubstituted or substituted by hydroxy alkyl, aryl, hydroxy-alkyl, aminoalkyl, aminoaryl, alkylamino, or carbamoyl, wherein the substituents contain from l to about 6 carbon atoms; and R2 and R3 may be the same or different and are hydrogen, alkyl having from l to about 6 carbon atoms, phenyl or benzyl or R2 and R3 together can form a ring having 5, 6 or 7 members.

36. The complexing agent of claim 35, wherein A
is .

37. The complexing agent of claim 35, wherein A
is -CHR2CHR3- and R2 and R3 are both hydrogen.

38. The complexing agent of claim 36 wherein n is 2.

39. The complexing agent of claim 35, wherein X
is O.

40. A complex having the following formula:

wherein M-z is a paramagnetic ion of an element with an atomic number of 21-29, 42-44 or 58-70, and a valence Z
of +2 or +3, r and s are integers between 1 and 6 and can be the same or different, the R' groups can be the same or different and are selected from the group consisting of hydrogen, alkyl having from 1 to 6 carbon atoms and mono or poly-hydroxyalkyl, the alkyl portion having from 1 to 6 carbon atoms, the R1' groups can be the same or different and are selected from the group consisting of -O- and , wherein R2' is selected from the group consisting of (CH2CH2O)p-R3' and and R4' is selected from the group consisting of H, R2' and R3', wherein R3', R5' and R6' can be the same or different and are selected from the group consisting of hydrogen, alkyl, hydroxy, alkoxy, mono- or poly-hydroxyalkyl, alkoxyalkyl, aminoalkyl or acylamino-alkyl, wherein the carbon-containing portions contain from 1 to about 6 carbon atoms or R5 and R6 can, together with the adjacent nitrogen, form a heterocyclic ring of five, six or seven members wherein O to l members other than the nitrogen are -O-, -S-, or and which members are unsubstituted or substituted by hydroxy, alkyl, aryl, hydroxyalkyl, aminoalkyl, aminoaryl, alkylamino, or carbamoyl wherein the substituents contain from 1 to about 6 carbon atoms, p and q can be the same or different and represent integers between 1 and 6, and wherein z of the R' groups are -O- and the remainder of the R1 groups are .

41; The complex of claim 40, wherein R2' is (CH2CH2O)p-R2'.

42. The complex of claim 40, wherein R2' is .

43. The complex of claim 41 or 42, wherein each R' group is hydrogen or alkyl having from 1 to 6 carbon atoms.

44. The complex of claim 42, wherein M-z is chromium (III), manganese (II), manganese (III), cobalt (II), nickel (II), copper (II), praseodymium (III), neodymium (III), samarium (III), ytterbium (III), WO9l/03261 PCT/US90/01196 gadolinium (III), terbium (III), dysprosium (III), holmium (III), or erbium (III).

45. The complex of claim 43, wherein M-z is gadolinium (III), terbium (III), dysprosium (III), holmium (III) or erbium (III).

46. The complex of claim 42, wherein R' is hydrogen, R2' is , R4' is hydrogen and r and s are each 1.

47. The complex of claim 42, wherein R' is hydrogen, R2 is (CH2CH2O)p-CH3, R4' is hydrogen or alkyl having from 1 to 6 carbon atoms and r and s are each 1.

48. A diagnostic composition suitable for enteral or parenteral administration to a warm-blooded animal which comprises an NMR imaging-effective amount of a complex of a paragnetic ion having the following formula:

wherein M-' is a paramagnetic ion of a- element with an atomic number of 21-29, 42-44 or 58-? , and a valence of +2 or +3, r and s are integers between 1 and 6 and can be the same or different, the R' groups can be the same or different and are selected from the group consisting of hydrogen, alkyl having from 1 to 6 carbon atoms and mono or poly-hydroxyalkyl, the alkyl portion having from 1 to 6 carbon atoms, the R2' groups can be the same or different and are selected from the group consisting of -O- and wherein R2' is selected from the group consisting of (CH2CH2O)p- R3 and and R4' is selected from the group consisting of H, R2' and R3' , wherein R3', R5' and R6' can be the same or different and are selected from the group consisting of hydrogen, alkyl, hydroxy, alkoxy, nono- or poly-hydroxyalkyl, alkoxyalkyl, aminoalkyl or acylamino-alkyl, wherein the carbon-containing portions contain from 1 to about 6 carbon atoms or R5' and R4' , together with the adjacent nitrogen, can form a heterocyclic ring of five, six or seven members wherein 0 to 1 members other than the nitrogen are -O-, -S-, or and which members are unsubstituted or substituted by hydroxy, alkyl, aryl, hydroxyalkyl, aminoalkyl, aminoaryl, alkylamino, or carbamoyl wherein the substituents contain from 1 to about 6 carbon atoms, p and q can be the same or different and represent integers between 1 and 6, and wherein z of the R1' groups are -O- and the remainder of the R1' groups are ; and a pharmaceutically acceptable carrier.

49. The composition of claim 48, wherein R2' is (CH2CH2O)p-R3'.

50. The composition of claim 49, wherein R2' is .

51. The composition of claim 49 or 50, wherein each R' group is hydrogen or alkyl having from l to 6 carbon atoms.

52. The composition of claim 48, wherein M-z is chromium (III), manganese (II), manganese (III), cobalt (II), nickel (II), copper (II), praseodymium (III), neodymium (III), samarium (III), ytterbium (III), gadolinium (III), terbium (III), dysprosium (III), holmium (III), or erbium (III).

53. The composition of claim 52, wherein M-z is gadolinium (III), terbium (III), dysprosium (III), holmium (III) or erbium (III).

54. The composition of claim 48, wherein R2' is , R' is hydrogen, R4' is hydrogen, r and s are each l and M-z is gadolinium (III).

55. The composition of claim 49, wherein R2' is CH2CH2OCH3, R' is hydrogen, R4' is methyl, r and s are each l and M-z is gadolinium (I.I).

56. The composition of claim 48, which further contains a pharmaceutically acceptable buffer.

57. The composition of claim 56, which further contains a pharmaceutically acceptable electrolyte.

58. The composition of claim 48, which further comprises a complexing agent of the formula wherein R' and R1' are as defined as in claim 48 and said complexing agent is complexed with one or more physiologically acceptable, non-toxic cations.

59. The composition of claim 58, wherein said complexing agent is employed in an amount ranging from about 0.1 to about 15 mole % of the paramagnetic ion-containinq complex and is complexed with one or more cations selected from the group consisting of sodium ions, calcium ions, magnesium ions, copper ions, zinc ions and mixtures thereof.

60. The composition of claim 59, wherein said complexing agent is complexed with calcium ions.

61. A method of performing an NMR diagnostic procedure, which comprises administering to a warm-blooded animal an effective amount of a complex of the formula:

wherein M-z is a paramagnetic ion of an element with an atomic number of 21-29, 42-44 or 58-70, and a valence Z
of +2 or +3, r and s are integers between 1 and 6 and can be the same or different, the R' groups can be the same or different and are selected from the group consisting of hydrogen, alkyl having from 1 to 6 carbon atoms and mono or poly-hydroxyalkyl, the alkyl portion having from 1 to 6 carbon atoms, the R1' groups can be the same or different and are selected from the group consisting of -0- and wherein R2' is selected from the group consisting of (CH2CH20)p- R3' and and R4' is selected from the group consisting of H, R2' and R3' , wherein R3', R5' and R6 can be the same or different and are selected from the group consisting of hydrogen, alkyl, hydroxy, alkoxy, mono- or poly-hydroxyalkyl, alkoxyalkyl, aminoalkyl or acylamino-alkyl, wherein the carbon-containing portions contain from 1 to about 6 carbon atoms or R5' and R6' can, together with the adjacent nitrogen, form a heterocyclic ring of five, six or seven members wherein 0 to l members other than the nitrogen are -O-, -S-, or and which members are unsubstituted or substituted by hydroxy, alkyl, aryl, hydroxyalkyl, aminoalkyl, aminoaryl, alkylamino, or carbamoyl wherein the substituents contain from l to about 6 carbon atoms, p and q can be the same or different and represent integers between l and 6, and wherein z of the R2' groups are -O- and the remainder of the R1' groups are and then exposing the animal to an NMR procedure, thereby imaging at least a portion of the body of the warm-blooded animal.

62. The method of claim 61, wherein R2' is (CH2CH20)p-R3'

63. The method of claim 61, wherein R2' is ,

64. The method of claim 61, wherein M-z is chromium (III), manganese (II), manganese (III), cobalt (II), nickel (II), copper (II), praseodymium (III), neodymium (III), samarium (III), ytterbium (III), gadolinium (III), terbium (III), dysprosium (III), holmium (III), or erbium (III).

65. The complex of claim 64, wherein M-z is gadolinium (III), terbium (III), dysprosium (III), holmium (III) or erbium (III).

66. The method of claim 61, wherein the pharma-ceutically acceptable carrier contains a pharmaceutically acceptable buffer.

67. The method of claim 66, wherein the pharma-ceutically acceptable carrier contains a pharmaceutically acceptable electrolyte.

68. The method of claim 61, wherein the pharma-ceutically acceptable carrier contains a complexing agent of the formula wherein R' and R1' are as defined as in claim 61 and said complexing agent is complexed with one or more physiologically acceptable, non-toxic cations.

69. The method of claim 68, wherein said complexing agent is employed in an amount ranging from about 0.1 to about 15 mole % of the paramagnetic ion-containing complex and is complexed with one or more cations selected from the group consisting of sodium ions, calcium ions, magnesium ions, copper ions and zinc ions and mixtures thereof.

70. The method of claim 69, wherein said complexing agent is complexed with calcium ions.

71. A complexing agent having the following formula:

wherein M-2 is a paramagnetic ion of an element with an atomic number of 21-29, 42-44 or 58-70, and a valence Z
of +2 or +3, r and s are integers between 1 and 6 and can be the same or different, the R2' groups can be the same or different and are selected from the group consisting of hydrogen, alkyl having from 1 to 6 carbon atoms and mono or poly-hydroxyalkyl, the alkyl portion having from 1 to 6 carbon atoms, the R1' groups can be the same or different and are selected from the group consisting of -O- and wherein R2' is selected from the group consisting of (CH2CH2O)p-R3' and and R4' is selected from the group consisting of H, R2' and R3', wherein R3' , R5' and R6' can be the same or different and are selected from the group consisting of hydrogen, alkyl, hydroxy, alkoxy, mono- or poly-hydroxyalkyl, alkoxyalkyl, aminoalkyl or acylamino-alkyl, wherein the carbon-containing portions contain from 1 to about 6 carbon atoms or R5' and R6' can, together with the adjacent nitrogen, form a heterocyclic ring of five, six or seven members wherein 0 to 1 members other than the nitrogen are -O-, -S-, or and which members are unsubstituted or substituted by hydroxy, alkyl, aryl, hydroxyalkyl, aminoalkyl, aminoaryl, alkylamino, or carbamoyl wherein the substituents contain from 1 to about 6 carbon atoms, p and q can be the same or different and represent integers hetween 1 and 6, and wherein z of the Rl groups are -O- and the remainder of the groups are .

72. The complexing agent of claim 71, wherein R2' is (CH2CH2O)p-R3'.

73. The complexing agent of claim 71, wherein R2' is .

74. The complexing agent of claim 72 or 73, wherein each R' group is hydrogen or alkyl having from 1 to 6 carbon atoms.