CA2142117A1 - Chromogenic reagents - Google Patents

Abstract

Chromogenic reagents, and more particularly compounds which function as selective cation-sensitive dyes are disclosed. The compounds are of formula (II) wherein X is a chromophore; Y and Z are -CH2(CHR-O-CHR)nCH2- in which n is an integer from 1 - 10 (which may be different for Y and Z) and each R independently is hydrogen or a substituent for hydrogen or when n is an integer from 2-10 at least one -CHR-CHR- group may additionally represent a substituted or unsubstituted arylene group; W indicates one or more optional substituents on the benzene ring; and A is a group imparting acidity to the molecule. Preferred compounds are those in which n = 2 for Z and n = 1 or 2 for Y; X is 4-nitrophenylazophenol and R is hydrogen or additionally when n is 2 at least one -CHR-CHR- group may represent a substituted or unsubstituted arylene group.

Description

.~
`--' W094/04539 PCT/GB93/01713 DESCRIPTION
CHROMOGENIC REAGENTS
The present in~ention relates to chromogenic reagents and more particularly to compounds which function a~ selective cation-sensitive dye~ (referred to hereafter as chromoionophore~). These chromoionophores are based upon chromophores which are linked to cation-selecti~e ionophores.
Chromoionophores based upon chromophores which are linked to cation-selective ionophore3 are described in the publications listed below:-J.F.Alder, D.C.Ashworth~ R. Narayanaswamy,R.E.Mocs and I.O.Sutherland, Analyst, 1987, 112, 11~1;
I.P.Danks and I.O.Sutherland, J.Inclusion Phenomena and Mol. Recognition in Chemistry, 199~, 12, 223;
A.M.Ring, C.P.Moore, K.R.A.S.Sandanayake, and I.O.Sutherland, J.Chem. Soc., Chem. Commun., 1992, 582.
In the first of these papers an optical fibre pro~e is reported to respond to potassium ions in a~ueous solution with a X+/Na+ se~ectivity ratio of 6.4 and in the other two papers new chromoionophores are described which show much greater K+/Na+
selecti~ity.
A series of modified cryptands has also been prepared as reagents for detecting potassium. These 2142117 t, ~, compounds are described in a patent and a recent publication which are, respectively;-R . Kli~ r D.Bodar, J.M.Lehn r ~ . ~elfert, and R.Bitsch, DE-A- 3,202,779 filed on 4 August l9B3 in the name of Merck Gmb~ tChem.Abs., 1984, 100, 34574p) and E.Chapoteau, B.P.Czech, C.R.Gebauer, A.Kumsr, K~Leong, - D.T. Mytych, W.Zazulak, D.H.Desai, E.Luboch, J.Xrzykawski and R.A.Bartsch, J.~rg. Chem., 1991, 56, ` 2575.
They have the general formula:
R

~ )n '- ~O

'I' ' ~0~_/0 i5 p 02~C6H4N=N, 3-phenyl-5-isothiazol l '`I 5-isothiazolylazo~ 5-thiazolylazo, 2,4,6-(02N)3--~ C6~2N=N, 4-oxo-2,5-cyclohexen-1-ylidenamino, or (p-'",1 Me22~C6~4 ) 2CO~;
m and; n are O or l; and , ;,~
X is N or C0~.
All of the documents above however relate to chromoionophores which are, to varying degrees, , "

,,,,~

~;~ 2 1 gL 2 iL 1 7 ~ r ~W094/04539 PCT/GB93/01713 selective for potassium ion~. These chromoionophores show relatively poor selectivity for other cations of physiological importanee, such as sodium, magnesium and calcium. There is also poor selectivity f or lithium, which has been widely used in the treatment of mental illne~s for aDout 40 years. Since the blood-3erum concentration of lithium is important in such treatments, it is important to be able to mea~ure this concentration accurately. ~owever, to date the best Li+~Na+ selectivity that has been reported (D.Parker and co-workers, J.Chem. Soc., Perkin Trans.

2, l990, 321) is about l500 which is still significantly short of the value of about 30000 re~uired for the measurement of serum conc0ntrations of therapeutic Li+ (O.5-2.0 mM) in the presence of normal serum concentrations of Na+ (~40 mM).
The present invention aims to overcome or at least alleviate the above-mentioned disadvantages.
According to the pre~ent invention there is provided a compound of the formula:
~ X

(II) , (~A N

,~
, "

--2 1 ~ 2 1 ~ ; ~ `

wherein X is a chromophore;
Y and Z are -C~I2 ( C~IR-O C~R) nCH2- in which n is an ' integer from 1 to 10 (which may be different for Y and Z), and each R independently is hydrogen or a substituent for hydrogen or when n is an integer f rom 2 to 1~ at least one -C~R-C~R- group may additionally repreqent a substituted or unsubstituted arylene group;
W indicates one or more optional substituents on the benzene ring; and A is a group imparting acidity to the molecule.
A preferably in~ludes an oxygen atom which is attached ~ to the benzene ring. A particular preferred A group -~ is -0~. A may be a cation binding group, for example, , methoxy.
The chromophore represented by X helps to impart colour to the molecule. X may be, for example, -N-NAr wherein Ar is a substituted or unsubstituted aryl ~i group.
The group Ar in X is preferably a substituted or unsubstituted ph~nyl group. Ex~mples of suitable Ar } groups include 4-nitrophenyl,2-nitrophenyl and 2,4-dinitrophenyl.
In Y andJor Z, n is preferably an integer from 1 , to 3 more preferably n is 1 or 2 in Y and 2 in Z. The . .

r,l ' \, r, t' ~ ~ ~
~ ,` 21~21 ~ 7 ~':'J .
W O 9~/0453g PCT/GB93/01713 R groups may al~o be different for Y and Z. ~he substituent may be, for ex,~mple, a hydrocarbyl group. The hydrocar~yl group may be, for example, an aryl, alkyl or alkenyl group which may itsel~ be sub~ti~uted. In addition to the case where R i9 an aryl group Y a~d z may also compri3e other group~ in~Luding an aromatic ri~g. For example, in the case where at least one -CaR-C~R- group i8 an arylan~ group Y and/or z ~ay be:

--C~2CH20 CKHCH~ _ (III) W

, .
. w~rein W is as defined above.

Thusj for example, in the ca~e where for Z, n=2 ,~ and -CER-CER- is a phenylane group z will be:

;~ C~? CH~
\
~, CH~ _ o O _ CH~
\ / (IV) ..;-' ' !

In ~he ca~e where for Z, n=4 and one -CER-CER- is a phenylene group, z cou1d be:

;, -, -CH~-CHR-O-CnR-CHR-O O CHR-CHR-O~CHR-Cr~_ (V) , ~! \=~
, ' , ., ;'i . ~

W094/0453g PCT/GB93/01713 -6-~
W may be, for example, an alkyl or alkenyl group which may itself be substituted, or a functional qroup such as, for.example, nitro, amino or substituted amino, or al~oxy.
Preferred compounds for use as a cryptand for lithium are those in which n represents l in Y and 2 in Z and R is hydrogen or alkyl or the -C~R-CHR- group i3 a su~tituted or unsuhstituted arylene group and the arylene group is preferably phenylene.
~ Preferred compounds for us~ as a cryptand for.
sodium are those in which n represents 2 in Y and Z
- and R is hydrogen or alkyl or the -C~R C~R- group is a substituted or unsubstituted arylene group and the ` arylene group is preferably phenylene.
The cryptands of the present invention are however suitable for complexing cations other than .~; xodium or lithium. Such cations include potas~ium, .~.1 calcium and magnesium-The ion-sensitive dyes represented by the above formul~ (II) form molecular complexes with certain cations at surprisingly high levels of selectivity. This is accompanied by a change in the absorption spectrum which makes these dyes ~, particularly suitable for use in an optical fibre ,,, ' sensor based upon a probe in which the ion-sensitive compound is immohilised at the tip of the fibre.

, , .

, ,...

_ 21~2~
``- W094/04539 PCT/GB93/01713 According to a further aspect of the present invention there is provided an optical fibre sensor comprising a probe in which an ion sensiti~e co~pou~d of the type illus~rated in formula II is immohilised at a tip of a fibre of the optical sensor.
Optical fibre sensors are discussed in the Alder et al Analyst 1987 Article referred to above ~nd consist of an optical probe and appropriate instrumentation. Referring to figure 4 of the accompanying drawings an optical fi~re tip is sensitised to cations by placing about lmg of Amberlite XAD2 resin (4~ on to the tip of the optîcal f ibre ( lmm diameter cor~ 3 ( 1 ) and encapsulating it in ~, ~
a porous PTFE membrane (such a~ ~illipore F~UP 50~ or the like) (2). The mem~rane is held in place by a heat ~hrinkable piece of tubing (3). The probe is ~; sencitised by immersion over~ight in a methanolic ....~
solution of the cryptand reagent followed by washing with distilled water. This probe can be used in an instrument of the type that has been described by .~
J.F.Alder and co-worke~s (Analyst, l987, ll2, ll9l) ~,7 (see above~.
To be useful in an optical fibre sensor a chromoionophore should be highly selective for a particular cation, should function in the physiological p~ range (typical of from p~ 6 to p~

8), and respond to a me~àl'ion in its normal concentration range ln biological fluids such as plasma. This invention provides chromoionophores which meet one or more of the above requiremen~s and in particular show surprisingl y high sele~tivity for lithium and sodium cations. In particular the .. chromoionophores (2a) and ~3) show higher selectlvity for lithium in extraction experLments, as compared with sodium, than any other chromoionophore that has - been repor~ed and the chromoinophores (2b) and (4) show better selectlYlty for so~ium, as compared wi.th lithium and potassium, than a compound which has recently been described, as showing 'potential for the i colorLmetric determination of sodium using procedures ~3i allowing the extraction mode', (in E.Chapoteau, M~S.Chowdhary, B . P . Czech, A. Rumar, nd W.Zazulak, J.Orq_Chem., 1992, 57, 2804-2808).
Indeed, the compounds of the present invention have many applicatlons in optical ~nd electronic .~
~ devices which are controlled at least to some extent -~ by cations (e.g. in switching by cations).
The compounds of the invention may be prepared ' J~ by, for example, (i) the reaction between an aryldiazonium salt of the formula ArN2+B (where B is an anion) and a phenolic cryptand having the general formula (VI) in SUBSTITUTE SHEET
ISIVEP
.~ .

~ 21~21~7 ^ W094/04~39 RCT/GB93/01713 . which R=H and in which Y and Z are as defined above, or (ii) by the prior formation of a quinonoid cryptand by oxidation of the phenolic cryptand shown below in which R=0~ followed by reacting the quinone with an arylhydrazine of the formula ArNHN~2.
Phenolic cryptands of the type ~W

~ (VI) +NH OH N
~yJ) _ can be prepared as their hydrobromide salts by heating a macrocyclic diamine with a suitable deri~ati~e of 2,6-bisbromomethyl-methoxybenzene in acetonitrile at . 80C for 18-24h according to the reaction:-' R
~ ~ (VII) ~ (VIII) NH~ ~NH ! +
~ J Br OMe Br :

) ' - 21~2117 ~ ~
WO 94/04~39 pcr/GB93/o17l3 : R

~q Br ~~~
~NH O~ ~N -~

--_ , +

C~Br They are described in a paper by A.F.Sholl and ~ IØSutheriand J.Chem.Soc., Chem. Co~mun, 1992, 1716-.- 1718 entitled ~selecti~e chromogenic reagents ~ased upon phenolic cryptands".
Compounds of the type illustrated in figure 2 - wherein Y and/or Z are illustrated in figures III, IV
:~ or V can be prepared as illustrated by the following reaction scheme.

f~II' -~ H,N N~, ~ ~ ~
~ OH N

'-' J \--O ~ ~~
., ~o>=< ~ .

,,, SUBSmUTE SHEET
-~ ISA/EP

, .
~;

W094l04539 214 21 ~ 7 PCT/GB93/01713 No.
(XIV) ,N
N' N OH N
~~
. ~

In which X and Xl are heated in the pre3ence of B~6 or B~3.S.Me2 in T~F to produoe XII which is in tu~rn reacted with 2,6, bis brQmomethylanisole and MeCN to produce XIII. This is then reacted with p-nitrophenyldiazonium choloride to produce XIV. When n=l, XIV is 4-nitropheynlazophenoldiaza 15-crown-5 modified ~y the addition of a benz~pe ring fu~ed to the macrocycle (see example ~) and when n=2 XIV is 4-n~trophenylazophenoldiaza 18-crown-6 modified by the addition of a be~zene ring fused to the ~acrocycle (see example 4).
The prasent invention also provides a method for i~, sensing cations, comprising complexing a compound of the present invention with a cation and determining the change in spectroscopic properties brought abo~t by the complexing. Spectroscopic method~ for determining the change in properties include ~, , , ' 2142117 ~ PCT/GB93/017l3 ~

mQasurement of absorbance at the absorption maxima of the chromoionophore and of the appropriate chromoinophore cat on complex aq illu~trated by the spectra shown in Figs. 1, 2 and 3 ' of the accompanying Drawings.
Fig. 1 show3 the absorption spectrum (300-700nm) of cryptand (2a) in C~C13 (~.14x10-5 mol dm-3) after equilibration - with an equal volume of aqueous ~iCl at p~ 7.0 (trishydroxymethylmethylamine/~cl buffer) at concentrations of 0~01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.50, and 1.0 mol dm-3.
The ab~orbance at 406 nm corre~pond3 to the free cryptand and at , 534 nm to the lithium complex.
-~ Fig. 2 ~hows ~he a~sorption spectrum (300-800 nm) o~
cryptand (2a) in C~C13 ~5.15x10-5 mol d~-3) after equilibratlon wi~h e~ual volumes of aqueous LiCL (1.0 mol dm-3~, NaC1 (1.0 mol dm-3)f and KCl ~1.0 mol dm-3 at p~ 9.0 (trishydroxymethy}methylamine/UCl ~uffer). Under these conditions there is no detectable response to either Na+ or ~+.
~:' Fig. 3 shows the absorption spectru~ (300-800 nm) of cryptand (2b) in CUC13 (2.79x10-5 mol dm-3) after equilibration .~
with equal volumes or aqueous LiCl (1.0 ~ol dm-3), NaCl (O.005 ~ mol dm-3), and ~Cl (1.0 mol dml3) at pU 9.0 ,~ (trishydroxymethylmethylamine/ucl ~uffer). Uuder these conditions the relative responses for (a) Na+ (b) ~+, and (c) , ,~
Li+ are ca 1 : 2 : 500 ba~ed upon absorbance in the 500-600 nm region.
,, .,~

"''''~:
SUBSmUTE SHEET
ISAIEP
,,'~

~ 2142117 -l3-: The present in~ention will now be described by way of example only, with reference to the preparation and testing of certain compounds.
In the Examples, compounds are identified by reference numerals la), lb), 2a), 2b), 3) and 4).
- These compounds have the general formula:
X
., ~
' ' 11 1 (XV) _/

in the case of examples la), lb), 2a) and 2b).
wherein for la) n=l and X-H
for lb) n=~ and X=H
for 2a) n=l ànd X=

,,~
~ ~ ~ N ~
~0-, ; ~
:' ,. ,, .1 ' , ~,~
~' ~:
~ " .
i ,~
SUBSmUTE SHEET
ISA/EP

, ~ `

WO 94/04539 PCI/GB93/0l713 water (7ml) and coo~ed~in ice. Sodium nitrite (0.1029g, 0.15mmol) dissolved in water (3ml) was then added to this solution to form the diazonium salt. An aliquot (2ml) of the solution of the ~iazonium salt was added to the phenolic cryptand solution which ~mmediately turned a red brown colour. The reaction mixture was stirred for a further 2hours and allowed to warm to room temperature before };~eing basified with NaOH ~3M~ to pEI 11 to produce a deep blue solution.
The blue aqueous solution was extracted with CE~2C12 (3x50ml) and the combined organic extracts were ovaporated to gi~Te a deep blue residue which was purified by flash column chromatography on neutral alumina (elue~t CH2C12 and 2% MeO~I/9a% C~I2C12) to give the azophenol (2a) as a red film (0.0614g, 8596) MS
(FAB) mtz 486 (M+}I)+; maX (C~ICl3) 406 nm(~ 13000);
H N~R 400 MHZ ~ DCl3 10.37 (lII, s br, ArOH), 8.34-8.31 (2H, d, J 9.0 Hz, ArEI), 7.92-7.90 (2H, d, J 8.9 ~Iz, Ar~l), 7.69 (2~, s, ArE~), 4.12 (2H, d, J 12.8Hz, ArC}lHN), 3.80-3.76 (2EI, m, OC~12), 3.68 (4H, s, OC:~2C~I2O)~ 3.60 (2H, d JAB--12.6Hz, ArC~N), 3.34 (2H, ~ ! ' : , i s br, OC~2), 3.16-3~12 (6H, m, OCH2 and NCH2), 2.79 ~j~ (2H, s br, NC~2), 2.56-2.51 (4H, m, NCH2); 13~ NMR 100 M~Iz ~ (CDC13) 164.7, 156.5, 147.6, 144.8, 129.3, substituted aromatic carbons, C-OH, C-N02, C-N=N, C-N=N, C-CH2, 124.7, 124.6, 122.7, aromatic C-~l, 71.2, '.~7 ~

W094/04539 214 ~117 PCT/GB93~01713 70.7, 68.5, OCH2, 57.9, 57.7, 54.4, NCH2.
Lithium comPlex - max (CHC13) 534 nm (~ 22000); 1~
NMR 400 M~z ~ CDCl3) 8.27 (2~, d, J 9.0 ~z, Ar~), 7.83 (2~, d J 9.2 Hz, Ar~), 7.69 (2~, s, ArH), 4a30 (2~ d, J 11.4 ~z, ArC~N), 3.93-3.89 (2H, m, OC~2), 3.86-3.81 (2~ m, OC~2), 3.69 3.64 (2~, m, OC~2), 3.4?-3.42 (2~, m, OC~2), 3.15 (2~9 d, J 11.4Hz, ArCHEN), 3.15-3.11 (2~, m, OCH2), 2.~8-2.93 2~, m, OC~2, 2.73-2.64 (6~, m, NC~2), 2.37-2.31 (2~, m, NC~2~. 13C NMR 100 M~z ~ (CDC13) 180.1, 158.1, 145.5, 13~.8, 130.8, substituted aromatic carbons, C-O , C-N02, C-N=N, C-~--N, C-C~2, 124.7, 121.4, aromatic C-H, 68.6, 68.3, 67,5, OCH2, 59.3, ~C~2Ar, 56.2, 51.1, NC~2.
.:
~ he extraction of lithium fro~ aqueous solutions of-LiCl by the chromoionophore (2a) was examined by absorption spectroscopy in the range 300-800 nm using a solution of (2a) in C~C13 and buf ered aqueous solutions of LiCl, typical spectra are shown in Figure 1. Even at pH 9.0 there was no detectable extraction of sodium and patassium from aqueous solutions of their chloride salts as indicated by the spectra shown in Figure 2, the sensiti~ity for lithium is at least 104 times greater than that for sodium or potassium~
Details of extraction coefficients for lithium in the p~ range 7-9 are given in Table 1.

W094/04539 PCT/GB~3/01713 d Example 2 Pre~aration and testin~ of 4-nitrophenylazo~henol diaza-18 crown~ L~
- Phenolic cryptand (lb) (0.0375g, 0.099 mmol) was dissolved in an aqueous solution of~sodium hydroxide . (0.0395g, 0.99 mmol in 2ml water) and stirred in an ice bath at 0C~ 4-Nitroaniline (0.1390g, 1.01mmol) was di~solved in hot conc. ~C1 (2ml), diluted with watsr (4.8 ml) and cooled in ice. 5Odium nitrite (0.0704g, 1.02mmol) dissolved in water (2ml) was then added to form the diazonium salt. An aliquot (4ml~ of the solution of the diazonium salt was added to the solution of the phenolic cryptand which imm~diately turned a red brown colour. The reaction mixture was stirred for a further 2hrs and allowed to warm to room temperature before being ba~ified wi~h NaO~ (3M) to p~
.~
11 to give a deep blue solution. The product was extracted into CH2C12 (3x~0ml) and the combined organic extracts were evaporated to gi~e a deep blue r~idue which was purified by flash column chromatography on neutral alumina (eluent C~2C12 followed ~y 1% MeOH/9~ CH~C12) to give the sodium complex of the azophenol 2b) as a deep blue film (yield 0.0419g, 80%). The sodium complex had ~S (FAB) 552 (M ); max (C~C13) 554nm (~ 20000), 1H NMR 400 ~z ~ (CDC13) 8.21 (2H, d, J9.0~z, ArH), 7.77 (2H, d, ,~

~' .~

21421~7 W094~04539 PCT/GB93/01713 J 9.0~z, Ar~), 7.70 (2H, s, ArH), 4.67 (2~, t, J
9.75Hz, OCH2), 4.17 (2~, d, J ll.9Hz, ArC~EN), 3.93-; 3.88 (2H, m, OCH2), 3.73-3.66 (4~, m, OC~2), 3.36-3.34 -(2H, m, OC~2), 3.27-3.22 t4H, m; OC~2), 3.09-3.06 t2~, m, OC~2), 2.36-2~89 (2~, m, NC~2), 2.88-2.81 (2~, m, ~C~2), 2.74 (2~, d, J 12~z, ArC~EN), 2.47-2.43 (2~, m, NCH2), 2.18-2.15 (2H, m, ~CH2)~ 13C NMR 100 M~z ~
(CDCl3) 179.4, 158.7, 144.1, 139.2, 129.7, su~stituted aro~atic carbons C-O , C-NO~, C-N=N, C-N=N, C-C~, 124.8, 121.0, aromatic C-~, 68.9, 67.8, 6700, O-C~2, 56.8,NC~2Ar, 52.9,N-C}i2.
The free azophenol (2b) was generated by shaking a chloroform solution of the sodium salt with an aqueous solution buffered at p~ 7. ~vaporation of the dried or~anic layer gave the azophenol as an ora~ge film. MS (FAB) m/z 530 (M+H)+; ~x (C~Cl3) 400 nm t~ 15000); 1~ NMR 400 M~z ~ (CDCl3) 8.35 (2~, d, J 9.1 ~z, Ar~), 7.94 t2H, d, J 9.1 ~z, Ar~), 7.71 (2~, s, ArH), 3.78-3.69 (8~, m), 3O61-3. (4~, m), 3.49-3.44 (B~, m), 2.79 (8~, s br, NC~2); 13C NMR 100 MHz ~
(CDCl3) 162.8, 156.4, 147.8, 145.0, 128.5, substituted aromatic carbons C-O~,- ¢-N02, C-N=N, C-N=N, C-C~2N, ,, 124.7, 122.8, aromatic C-~, 70.6, 68.3 (br), O-C~2, :~ 58.2, NC~2Ar, 56.2, N-C~2~
The extraction of sodium, potassium, lithium, calcium and magnesium from aqueous solutions of their .~

~ -~"~
.,~
:,~

,. ~"~ , . ... . -~.
W094/04~39 PCT/GB93/01713 -la-chloride salts by the chromoionophore (2b) was - ex~mined by absorption spe~troscopy in the range 300-800 nm using a solution of (2b) in C~C13 and buffered aqueous solutions of the salts, typical spectra are shown in Figure 3. At p~ 9.0 there was significant extraction of lithium and potassium as indicated by the spectra shown in Figure 3, and also of calcium ~ut the sensitivity for sodium is ca 400 times greater tha~ that for potassium and 800 tLmes greater than that for lithium at this p~. The sensitivity for sodium is ca 16 times greater than that for calcium but in this ca~e the calclum complex has an absorption mzximum at 500nm (orange solution) whereas the sodium complex hac an absorption maximum at 554 nm. (purple solution). Details of extraction coefficients for sodium in the p~ range 7-9 and for lithium, pota~sium and calcium at p~ 9 are given in the ~able 1.

~ , W094/04539 21 ~ 21 1 7 PCT/GB9~/01713 Table 1 Extraction coefficients a for chromoionophores (2a) and (2~) (d) Compound pH~.l cation 1OgloKel~o~2 (~) ,.7 ~+ ~9 8.2 ~+ -70 9.3 ~ -,.2 (c) 6.9 i~a~ -6.~
8.1 ~a- -o.b .3 ~a+ -6.7 ~ 9.~ K+ -9.3 9.~ ~+ -9.6 9.1 - Ca~+ -7.9 a For a solution of (2a) or (2b) at C2 10 5 to 19 4 mol dm~3 in C~C13 and solutionq of M+ at lO 4 to 1 mol dm ~ in water using a tris(hydroxymethyl)-methylamlne-C~l buffer. Ke is based upon changes in ab~orption at 406 and 534 nm for (2a) and Li+, 402 and 554 nm for (2b) and Li+, Na+ an~ K+, and 402 and 500 nm for (2b) and Ca2+
b No measurable response for Na+, K+, Mg2+, a~d Ca2+
in the pH range 7-9 up to 1 mol dm~3 concentration of the metal salts.
c No mea~urable response for Mg2+ in the p~ range 7-9 up to l mol dm~3 concentration of the metal salts.
dKe = ~+]aq.[M~CI ]org/~M+]aq.[CIH]org (where the WO 94/04~39 PCI`/GB93/01713 ~ i-1, subscripts aq and org refer to the aqueous and organic phases respectively and CI~ refers to the ionisable chromoionophore).
It will be appreciated f rom the above that compound (2a) in particular has a remarkable high selecti~ity for lithium, far greater than anything previously known.
Furthermore, when examples 2a and 2b were compared to two further examples, 3 & 4, in which Z
had been modified by the fusion of a benzene ring to the macrocycle as illustrated in formula IV even better results were o~tained.
Thus, example 3 was 4 nitrophenyl azophenol diaza 15-crown-~ modified by the addition of a benzene ring fu~ed to the macrocycle and example 4 was 4 nitrophenyl azophenol diaza la-crow~-6 modified by the addition of a benzene ring fused to the macrocycle.
The~e chromogenic reagents 3 and 4 show higher selectivity in cation extraction experiments than the related compounds 2a and 2b.
The extraction coefficients for the chromogenic reagents 3 and 4 (as compared to 2a and 2b) are listed in Table 2. For lithium extraction the colour change on the formation of the Li~ complex formula XVI is from yellow to pink and for the Na+ complex formula - XVI from yellow to purple.

~ WO 94/04539 2 1 4 2 1 1 7 Pl ~/GB93/()1713 2 1 ~

( XVI ) N,N

N ~M~N
~ ~

n = 1 or 2 M~ , N.~ `. c. G~

Compound 3 responds to Li+ in the p~ range 7-9 and to no other cation of physiological importance (K~,Na~, Mg2+, and Ca2+) with a selectivity ratio for Li+:Na+
of >104. Co~pound 4 responds only to Na+ at pH 7 and at higher pH the selectivity for Na+:Li+ is ca 5000, for Na+:K+ is ca 6000, and for Na+:Ca~+ is ca 4000~ no response is observed for Mg~+. The two compounds 3 and 4 are more lipophilic than 2a and 2b and show no extraction int~ water in the p~ range 7-9 and show salecti~ity for Li+ and Na+ that is higher than that reported for any other reagents. They should thus prove ideal for use in optical fibre sensors for Li~
and Na+ and, in modified form, their exceptionally high 21~2117 s~lectivity could provide suitable reagents for detecting Li~ and Na+ in, for example, microscopic examination of biological samples. The re~pon~e of the reagents is pH dependent so that a p~ sensitive reagent must also be used in the optical fibre probe or in the biological sample. If the cation sensing and p~ sensing reagents respond in a different wavelength range it should be possible to make both measurements sLmultaneously.
Table 2 2a,2b, 3 and 4 Extraction coe~ficients a~e and Selectivitie~ for Chromoionophores logloKe (iO.2)b Host Compound 2a Compound 3 Cation Li+ li+
pH 7 ~.9 ~.9 pH 8 -7.0 ~-7.3 pH 9 -7.2 -7.3 ~cd 534 52 logl~)Ke (iQ2)b logloKe (:~:0.2)b Host Compound ~b Compound 4 CationLif Na+ K ' Ca2+ Li+ Na+ K+ Ca2+
pH 7 ~.5 ` -5.8 pH 8 ~.6 -5.8 pH 9 -9.6 ~.7 -9.3 -7.9 -9.5 -5.8 -9.6 -9.4 ~c,d 554 554 554 500 5~ 546 560 500 ~ 21 4 21 1 7 PCT/GB93/01713 a. For a solution of the chromoionophore at ca 10 5 to 10 4 mol dm~3 in CHCL3 and solutions of M+ at 10 4 to 1 mol dm 3 in water using a tris(hydroxy methyle)methylamine-~Cl buf f e~ ~
b. Ke = [~+]aq.[M+Cl ~org/~M+~aq.~Cl~]org (where the su~scripts aq and org refer to aqueous and organic pha~es re~pectively and ClH refers to the ionisable chromoionophore.
c. ~ Inm) u~ed for calculating ~M+Cl ]org, in general ~=1i gives/~mBX ca 530 nm, M=Na gives ~maX ca 550 nm, M-K gives ~ mzx ca 560 nm, and M=Ca give~ ~ maX ca 500 nm.
d. ~ max ca 400 nm used for calculating [Cl~] org.
e. Compound~ 2a and 3 give no measurable respon~e to Na+, R+, Mg2+, and Ca2+ in the p~ range 7-9 up to 1 mol dm~3 concentrations of the metal salts.
Compounds 2b and 4 give no measurable respon~e to Mg2+
-in the p~ range 7-9 up to 1 mol dm~3 concentrations of the metal salts.

Claims (27)

-24-

1. A compound of the formula:

(II) wherein X is a chromophore;
Y and Z are - CH2 (CHR-O-CHR)nCH2 - in which n is an integer from 1 - 10 (which may be different for Y
and Z) and each R independently is hydrogen or a substituent for hydrogen or when n is an integer from 2-10 at least one -CHR-CHR- group may additionally represent a substituted or unsubstituted arylene group ;
W indicates one or more optional substituents on the benzene ring; and A is a group imparting acidity to the molecule.

2. A compound as claimed in claim 1 in which A
is a cation binding group.

3. A compound as claimed in claim 1 or 2 in which A indicates an oxygen atom which is attached to the benzene ring.

4. A compound as claimed in claim 1, 2, or 3, in which A is a hydroxy group or methoxy group.

5. A compound as claimed in claim 4, in which A
is -OH.

6. A compound as claimed in any of the preceding claims wherein the chromophore X is H.

7. A compound as claimed in any of claims 1 to 5, wherein the chromophore X is -N=NAr, wherein Ar is a substituted or unsubstituted aryl group.

8. A compound as claimed in claim 7 wherein the aryl group is 4-nitrophenyl, 2-nitrophenyl or 2,4 dinitrophenyl.

9. A compound as claimed in claim 8 wherein the aryl group is 4-nitrophenyl.

10. A compound as claimed in claim 6 or 9, in which in Y and/or Z, each R independently is hydrogen or a substituent comprising a hydrocarbyl group.

11. A compound as claimed in claim 10 wherein the hydrocarbyl group is an aryl, alkyl or alkenyl group which may itself be substituted.

12. A compound as claimed in claim 10 in which each R is hydrogen.

13. A compound as claimed in claim 6 or 9 wherein Y and/or Z comprises a group including an aromatic ring.

14. A compound as claimed in claim 13 in which Y

and/or Z are of the formula:

(III) wherein W is as defined in claim 1.

15. A compound as claimed in claim 14 wherein there is no substituent W.

16. A compound as claimed in claim 12 or 13 wherein n = 2 for Z.

17. A compound as claimed in claim 16 wherein: n =
1 for Y.

18. A compound as claimed in claim 16 wherein: n =
2 for Y.

19. A compound as claimed in claim 12 or 15 wherein: n = 3 or Z.

20. A compound as claimed in claim 19 wherein: n =
1 for Y.

21. A cryptand for lithium comprising a compound as claimed in claim 17.

22. A cryptand for sodium comprising a compound as claimed in claim 18.

23. A cryptand comprising a compound as claimed in claim 20.

24. An optical fiber sensor comprising a probe in which an ionsensitive compound as claimed in claims 17 or 18 is immobilized a tip or fibre of the optical sensor.

25. A method or sensing cations comprising complexing a compound as claimed in claims 17 or 18.

with a cation and determining the change in spectroscopic properties brought about by the complexing.

26. A method as claimed in claim 25 in which the cation is selected from the group comprising sodium, and lithium.

27. A compound substantially as hereinbefore described with reference to formula XIV, XV, and XVI.