JP5392746B2 - Novel water-soluble iridium complex compound and oxygen concentration measuring reagent using the same - Google Patents

Description

  The present invention relates to a novel water-soluble iridium complex compound and a reagent capable of visualizing and quantifying the oxygen concentration in real time using the compound.

さらに、酸素濃度に依存して近赤外光領域にりん光を発する化合物も開発した（(btq)₂Ir(acac)、(btiq)₂Ir(acac)、(btph)₂Ir(acac)）（特許文献２）。 Iridium (III) complexes (Non-Patent Documents 1 to 4) are known to emit phosphorescence, and are expected to be applied to organic EL displays and the like.
On the other hand, at room temperature of the present inventors, an iridium complex discovered _{((btp) 2 Ir (acac} )) to emit the phosphorescent depending on the oxygen concentration, the iridium complex _{((btp) 2 Ir (acac} )) A method for measuring oxygen concentration in living tissue using phosphorescence (intensity, life) was developed (Patent Document 1). In addition, from the measurement of phosphorescence intensity and lifetime of (btp) ₂ Ir (acac), we succeeded in quantifying the oxygen concentration in the liposome membrane, visualizing the oxygen concentration in cancer cells, and visualizing the tumor in tumor-bearing mice ( Patent Document 1).

Furthermore, compounds that emit phosphorescence in the near-infrared region depending on the oxygen concentration were also developed ((btq) ₂ Ir (acac), (btiq) ₂ Ir (acac), (btph) ₂ Ir (acac)) (Patent Document 2).

  However, since these compounds do not dissolve in water, when administered to a living body, it is necessary to dissolve once in an organic solvent such as dimethyl sulfoxide (DMSO) and dilute with physiological saline. The possibility of effect cannot be denied. Until now, there are ruthenium complexes and metal porphyrin complexes as water-soluble phosphorescent compounds. These compounds have low phosphorescence quantum yields (less than 0.1) compared to iridium complexes, and ruthenium complexes have been shown to be cytotoxic. Using these compounds, oxygen in cells and tissues It is difficult to quantify the concentration.

In general, it is known that polyethylene glycol (PEG) is bound as a method for solubilizing an organic compound having low solubility in water. However, although PEG is said to be low in toxicity to living bodies, it has been regarded as a problem that the molecular weight (generally 5000 or more) becomes too large.
Shunji Tobita, Toshitada Yoshihara, Toshiyuki Takeuchi, Masahiro Hosaka, “Oxygen Concentration Reagent and Oxygen Concentration Method”, Japanese Patent Application 2007-126518 Satoshi Tobita, Toshitada Yoshihara, Toshiyuki Takeuchi, Masahiro Hosaka, Japanese Patent Application 2008-185151 S. Lamansky, P. Djurovich, D. Murphy, F. Abdel-Razzaq, H. Lee, C. Adachi, PE Burrows, SR Forrest, and ME Thompson, J. Am. Chem. Soc., 123, 4303 (2001 ). H. Konno, Chem. Times, 199, 13 (2006). M. Nonoyama, Bull. Chem. Soc. Jpn., 47, 767 (1974). S. Sprouse, KA King, PJ Spellane, and RJ Watts, J. Am. Chem. Soc., 106, 6647 (1984).

  An object of the present invention is to provide a novel iridium complex that can be used even in an aqueous solution and emits phosphorescence depending on the oxygen concentration, and to provide an oxygen concentration measuring reagent using the same.

  The present inventor has intensively studied to solve the above problems. As a result, we succeeded in synthesizing a water-soluble iridium complex maintaining phosphorescence properties by changing acetylacetone, which is a ligand of iridium complex, to a water-soluble ligand containing amino acid residues or peptide residues. Furthermore, the inventors have found that the phosphorescence depends on the oxygen concentration, and have completed the present invention.

That is, the present invention is as follows.
(1) A compound represented by any one of the following general formulas (I) to (IV) (n represents a natural number of 1 to 5, and R represents an amino acid residue or a peptide residue).
(2) The compound of (1), wherein the amino acid residue or peptide residue is a residue of an amino acid having a hydroxyl group, a carboxyl group or an amino group in the side chain, or a residue of a peptide comprising the amino acid.
(3) The compound according to (1), wherein the amino acid residue or peptide residue is an amino acid residue selected from tyrosine, aspartic acid, glutamic acid, lysine and arginine or a peptide residue comprising the amino acid.
(4) The compound of (1), wherein the amino acid residue or peptide residue is a residue of a peptide comprising aspartic acid residue or aspartic acid.
(5) A compound represented by the following formula (V) or (VI).
(6) An oxygen concentration measurement reagent containing the compound according to any one of (1) to (5).

Since the iridium complex of the present invention emits phosphorescence depending on the oxygen concentration, the oxygen concentration in the aqueous solution can be monitored, and the oxygen concentration can be determined from the value of the phosphorescence lifetime. Thereby, it can be used in fields such as analytical chemistry, life science, bioimaging field, medical diagnosis, and cell biology. Specifically, it can be used as an oxygen concentration determination reagent, a hypoxic cell imaging reagent, a hypoxic tumor diagnostic reagent, and the like.
The Ir complex of the present invention is a water-soluble iridium complex that maintains the phosphorescent properties of (btp) ₂ Ir (acac), and can reduce the proportion of organic solvents in living organisms. It is also useful as an oxygen sensor that can be used in water.

  The present invention is described in detail below.

The compound of the present invention is a compound represented by any one of the following general formulas (I) to (IV).

Here, n represents a natural number of 1 to 5, preferably 1 to 3, and particularly preferably 2.
R represents an amino acid residue or a peptide residue, and is preferably an amino acid residue having a hydroxyl group, a carboxyl group or an amino group in the side chain, or a peptide residue comprising the amino acid.
The “amino acid residue and peptide residue” refers to a residue when an amino acid or peptide is amide-bonded via its amino group.
Examples of amino acids having a hydroxyl group in the side chain include tyrosine, serine, and threonine, and tyrosine is more preferable.
Examples of amino acids having a carboxyl group in the side chain include aspartic acid and glutamic acid, and examples of amino acids having an amino group in the side chain include lysine and arginine. The amino acid may be L-form, D-form, or non-natural amino acid.
Examples of peptide residues include peptide residues composed of one or more of the above amino acids, and the length is preferably 2 to 10, more preferably 2 to 5.

More specifically, examples include compounds represented by the following formula (V) or (VI), wherein R is an aspartic acid residue or an aspartic acid dipeptide residue. However, the compounds of the present invention are not limited to the following compounds as long as they exhibit water solubility and emit phosphorescence depending on the oxygen concentration.

  The iridium complex of this invention is compoundable according to the method as described in the below-mentioned Example. In the examples, synthesis examples of compounds of the above formula (V) or (VI) in which R is a residue of aspartic acid or aspartic acid dipeptide are shown, but other examples can be obtained by changing the type of amino acid or peptide to be amide-bonded. The compound which the amino acid or peptide of this couple | bonded can be obtained.

  The iridium complex as described above dissolves in an aqueous medium and emits stronger phosphorescence when the oxygen concentration in the aqueous solution is low. Therefore, the oxygen concentration can be measured based on the intensity of phosphorescence. That is, it can be determined that the oxygen concentration is low when phosphorescence is strong. It is also possible to quantitatively measure the oxygen concentration by obtaining the relationship between the oxygen concentration and the phosphorescence intensity in advance.

In addition, an iridium complex can be administered to a laboratory animal such as a mouse or rat or a human to detect a site where the oxygen concentration is lowered. Since the cancer tissue lacks oxygen supply, it can be used as a diagnostic agent for cancer by specifically staining the cancer tissue by detecting the site where the oxygen concentration is lowered.
When detecting the oxygen concentration in the living body, after adding and incubating the iridium complex to the living body, use a fluorescence microscope, a fluorescence measuring apparatus, a fluorescence imaging apparatus, etc. that can excite the iridium complex and observe phosphorescence. Phosphorescence can be observed.

  The following examples illustrate the present invention more specifically. However, the present invention is not limited to the following examples.

Synthesis of (btp) ₂ Ir (sa)
2-Ethoxyethanol (90 ml) and water (30 ml) were added to 2-benzothienylpyridine (1175.4 mg, 3.0 mmol) and iridium chloride trihydrate (purity: 90%, 1373.6 mg, 6.5 mmol) and refluxed for 16 hours. did. The solution was cooled to room temperature and the resulting solid was filtered. Dehydrated acetone (120 ml) was added to the obtained solid (859 mg, 0.66 mmol) and silver trifluoromethanesulfonate (377.2 mg, 1.47 mol) and refluxed for 3 hours, and the solution was filtered. Succinyl acetone (308.8 mg, 1.95 mol) and triethylamine (1 ml) were added to the obtained filtrate, and the mixture was stirred at room temperature for 20 hours. The solution was evaporated to dryness, and the resulting solid was generated using column chromatography (developing solvent: chloroform: methanol (9: 1, v / v)) (yield: 993.5 mg, yield: 97.5%).
¹ H HNR (300 MHz, d-DMSO, TMS, RT): δ 8.60-8.51 (2H, m), 8.01-7.98 (2H, d), 7.78-7.74 (2H, q), 7.70-7.62 (2H, q), 7.23-7.21 (2H, q), 7.10-7.08 (2H, q), 6.83-6.77 (2H, t), 6.30-6.24 (2H, t), 5.43 (1H, s), 2.37-2.22 ( 4H, m), 1.76 (3H, s)

Synthesis of (btp) ₂ Ir (sa-NH ₂ )
(btp) ₂ Ir (sa) (100.5 mg, 0.130 mol), Fmoc ethylenediamine (46.2 mg, 0.145 mol), diisopropylethylamine (49 μl, 0.288 mol) in DMF (5 ml) and HATU (56.2 mg, 0.148 as a condensing agent) mol) and stirred for 3 hours in an ice bath. Water was poured into the solution to precipitate a solid and filtered. The obtained product was produced using column chromatography (developing solvent: chloroform) (yield: 42.1 mg, yield: 31%). To the obtained solid (42 mg, 0.041 mol), a 2% DBU / DMF (8 ml) solution was added and stirred at room temperature for 3 hours. Water was added to the solution, extraction was performed using chloroform, the chloroform solution was dried over sodium sulfate, and after filtration, the filtrate was dried under reduced pressure. A small amount of chloroform was added to the obtained oil, and then a large amount of hexane was added to precipitate a solid, followed by filtration (yield: 16.7 mg, yield: 51%).
¹ H HNR (300 MHz, CDCl ₃ , TMS, RT): δ 8.45-8.32 (2H, m), 7.82-7.75 (2H, d), 7.68-7.62 (4H, m), 7.10-7.02 (4H, m ), 6.83-6.77 (2H, m), 6.22-6.20 (2H, d), 6.15 (1H, s), 5.29 (1H, s), 2.65-2.45 (4H, m) 2.32-2.25 (2H, m) , 2.15-2.08 (2H, m), 1.80 (3H, s)

Synthesis of (btp) ₂ Ir (sa-Asp)
(btp) ₂ Ir (sa) (171 mg, 0.22 mol), L-aspartic acid (97.8 mg, 0.20 mol) protected with a carboxy group at the Z group, and DMF (5 ml) were added to diisopropylethylamine (85 μl, 0.50 mol) Using HATU (84 mg, 0.22 mol) as a condensing agent, the mixture was stirred for 3 hours in an ice bath. Water was poured into the solution to precipitate a solid and filtered. The obtained product was produced using column chromatography (developing solvent: chloroform) (yield: 74 mg, yield: 35%). (Btp) ₂ Ir (sa-Asp) (70 mg, 0.066 mol) protected with a Z group was dissolved in tetrahydrofuran, an appropriate amount of 5% PdC was added, the container was filled with hydrogen, and the mixture was stirred at room temperature. The reaction was followed by TLC, and when the raw material disappeared, the solution was filtered and the filtrate was dried under reduced pressure (yield: 28 mg, yield: 49%).
¹ H HNR (300 MHz, d-DMSO, TMS, RT): δ 12.5 (2H, br), 8.45-8.37 (2H, d), 8.12 (1H, s), 8.01-7.98 (2H, d), 7.79 -7.71 (4H, q), 7.23-7.21 (2H, t), 7.10-7.08 (2H, t), 6.83-6.77 (2H, t), 6.10-6.02 (2H, d), 5.38 (1H, s) , 4.50-4.45 (2H, m), 2.37-2.22 (4H, m), 1.76 (3H, s)

Synthesis of (btp) ₂ Ir (sa-Asp-Asp)
(btp) ₂ Ir (sa) (148.3 mg, 0.193 mol), L-Asp-L-Asp (100.2 mg, 0.193 mol) protected with a carboxy group at the Z group, diisopropylethylamine (73 μl, 0.429 mol) in DMF ( 5 ml) was added, and HATU (82 mg, 0.216 mol) was used as a condensing agent, followed by stirring in an ice bath for 3 hours. Water was poured into the solution to precipitate a solid and filtered. The obtained product was produced using column chromatography (developing solvent: chloroform) (yield: 192.2 mg, yield: 78.2%). (Btp) ₂ Ir (sa-Asp-Asp) (192 mg, 0.151 mol) protected with a Z group was dissolved in tetrahydrofuran, an appropriate amount of 5% PdC was added, and the container was filled with hydrogen and stirred at room temperature. The reaction was followed by TLC, and when the raw material disappeared, the solution was filtered, and the filtrate was dried under reduced pressure (yield: 70.2 mg, yield: 46%).
¹ H HNR (300 MHz, d-DMSO, TMS, RT): δ 12.5 (3H, br), 8.43-8.37 (2H, d), 8.20 (1H, s), 8.01-7.98 (2H, d), 7.81 -7.73 (4H, q), 7.23-7.21 (2H, d), 7.10-7.08 (2H, t), 6.83-6.77 (2H, t), 6.10-6.02 (2H, t), 5.38 (1H, s) , 4.50-4.45 (2H, m), 4.12 (1H, s), 2.20-2.10 (4H, m), 1.75 (3H, s)

Table 1 shows (btp) ₂ Ir (sa), (btp) ₂ Ir (sa-NH ₂ ), (btp) ₂ Ir (sa-Asp), and (btp) ₂ Ir (sa-Asp-Asp) Tris-HCl buffer (pH = 7.0): shows solubility in DMSO (95: 5) and Tris-HCl buffer (pH = 7.0). (btp) ₂ Ir (acac) hardly dissolves in Tris-HCl buffer (pH = 7.0): DMSO (95: 5), but (btp) ₂ Ir (sa), (btp) ₂ Ir (sa- It can be seen that about 23 mgL ^{−1 is} dissolved in NH ₂ ). On the other hand, (btp) ₂ Ir (sa-Asp) and (btp) ₂ Ir (sa-Asp-Asp) dissolve in Tris-HCl buffer (pH = 7.0). In particular, (btp) ₂ Ir (sa-Asp-Asp) is 340 μM in terms of molar concentration, and has almost reached a practical level. From this result, water solubility can be remarkably improved by introducing a water-soluble amino acid.

FIG. 1 shows the absorption and phosphorescence spectra of each iridium complex. As a result, (btp) ₂ Ir (sa-Asp) and (btp) ₂ Ir (sa-Asp-Asp) were converted into (btp) ₂ Ir (acac) in acetonitrile in Tris-HCl buffer (pH = 7.0). ) Showed almost the same absorption and phosphorescence spectrum as that of), and it was found that modification of the acac site with an amino acid or peptide did not affect phosphorescence properties. Table 2 shows the phosphorescence quantum yield of each compound during nitrogen substitution. (btp) ₂ Ir (sa-Asp) and (btp) ₂ Ir (sa-Asp-Asp) decrease the phosphorescence quantum yield in water, but they are large compared to conventional water-soluble phosphorescent compounds. is there.

In FIG. 2, the oxygen dependence of the phosphorescence intensity of (btp) ₂ Ir (sa-Asp-Asp) in Tris-HCl buffer (pH = 7.0) was examined. As a result, the phosphorescence intensity increased 5.3 times under Ar (argon) substitution compared to under air saturation, and the phosphorescence intensity changed depending on the oxygen concentration in water. Expansion can be expected.

Reference example 1
Synthesis of bis [2- (2'-benzothienyl) -quinolinato-N, C ^{3 '} ] iridium (acetylacetone) ((btq) ₂ Ir (acac))

Synthesis of 2-benzothienylquinoline Benz [b] thiophen-2-ylboronic acid (990 mg, 5.6 mmol) and 2-chloroquinoline (937 mg, 5.7 mmol) dissolved in toluene (20 ml) and ethanol (10 ml), palladium catalyst (200 mg, 0.17 mmol) and 2M aqueous sodium carbonate solution (20 ml) were added, and the mixture was refluxed for 5 hours under N ₂ substitution. The reaction solution was poured into water, extracted with chloroform, the chloroform solution was dried over sodium sulfate, filtered, and the filtrate was dried under reduced pressure. The obtained solid was washed with toluene (yield: 888 mg, yield: 61%).
¹ H HNR (300 MHz, CDCl ₃ , TMS, RT): δ 8.20-8.17 (1H, d), 8.15-8.12 (1H, d), 7.98 (1H, S), 7.96-7.93 (1H, d), 7.91-7.88 (1H, q), 7.86-7.83 (1H, q), 7.82-7.79 (1H, d), 7.75-7.70 (1H, t), 7.55-7.50 (1H, t), 7.39-7.36 (2H , q)

Synthesis of bis [2- (2'-benzothienyl) -quinolinato-N, C ^{3 '} ] iridium (acetylacetone)
2-Ethoxyethanol (30 ml) and water (10 ml) were added to 2-benzothienylquinoline (581 mg, 2.2 mmol) and iridium chloride trihydrate (purity: 90%, 392 mg, 1.0 mmol), and the mixture was refluxed for 16 hours. The solution was cooled to room temperature and the resulting solid was filtered. To the obtained solid (304 mg, 0.20 mmol), 2-methoxyethanol (25 ml), acetylacetone (1 ml) and sodium carbonate (170 mg) were added and refluxed for 2 hours. The solution was cooled to room temperature and the resulting solid was filtered. The obtained solid was produced using column chromatography (developing solvent: chloroform) (yield: 262 mg, yield: 79%).
¹ H HNR (300 MHz, CDCl ₃ , TMS, RT): δ 8.17-8.14 (2H, d), 8.01-7.98 (2H, d), 7.85-7.83 (2H, d), 7.75-7.73 (2H, d ), 7.71-7.68 (2H, d), 7.37-7.32 (2H, t), 7.73-7.23 (2H, t), 7.02-6.97 (2H, t), 6.57-6.52 (2H, t), 6.32-6.30 (2H, d), 4.63 (1H, s), 1.55 (6H, s)

Reference example 2
Synthesis of bis [1- (2'-benzothienyl) -quinolinato-N, C ^{3 '} ] iridium (acetylacetone) ((btiq) ₂ Ir (acac))

Synthesis of 1-benzothienylisoquinoline Benz [b] thiophen-2-ylboronic acid (997mg, 5.6mmol), 1-chloroisoquinoline (946mg, 5.8mmol) dissolved in toluene (20ml), ethanol (10ml), palladium catalyst (220 mg, 0.19 mmol) and 2M aqueous sodium carbonate solution (20 ml) were added, and the mixture was refluxed for 5 hours under N ₂ substitution. The reaction solution was poured into water, extracted with chloroform, the chloroform solution was dried over sodium sulfate, filtered, and the filtrate was dried under reduced pressure. The obtained solid was produced using column chromatography (developing solvent: chloroform) (yield: 1.16 g, yield: 79%).
¹ H HNR (300 MHz, CDCl ₃ , TMS, RT): δ 8.62-8.60 (2H, d), 7.96-7.87 (3H, m), 7.84 (1H, s), 7.78-7.73 (1H, d), 7.71-7.67 (1H, d), 7.65-7.63 (1H, d), 7.42-7.39 (2H, m)

Synthesis of bis [1- (2'-benzothienyl) -quinolinato-N, C ^{3 '} ] iridium (acetylacetone)
2-Ethoxyethanol (30 ml) and water (10 ml) were added to 1-benzothienylisoquinoline (574 mg, 2.2 mmol) and iridium chloride trihydrate (purity: 90%, 398 mg, 1.0 mmol), and the mixture was refluxed for 16 hours. The solution was cooled to room temperature and the resulting solid was filtered. To the obtained solid (250 mg, 0.17 mmol), 2-methoxyethanol (30 ml), acetylacetone (1 ml) and sodium carbonate (150 mg) were added and refluxed. The solution was cooled to room temperature and the resulting solid was filtered. The obtained solid was produced using column chromatography (developing solvent: chloroform) (yield: 50 mg, yield: 18%).
¹ H HNR (300 MHz, CDCl ₃ , TMS, RT): δ 8.92-8.88 (2H, d), 8.22-8.19 (2H, d), 7.88-7.84 (2H, m), 7.68-7.64 (4H, m ), 7.56-7.54 (2H, d), 7.32-7.27 (2H, m), 6.94-6.91 (2H, d), 6.56-6.53 (2H, m), 6.18-6.14 (2H, d), 5.12 (1H , s), 1.63 (6H, s)

Reference example 3
Synthesis of bis [9- (2'-benzothienyl) -phenanthrinate-N, C ^{3 '} ] iridium (acetylacetone) ((btph) ₂ Ir (acac))

Synthesis of 9-chlorophenanthridine To phenanthridinone (2.0 g) was added phosphorus oxychloride (15 ml) and dimethylaniline (0.63 ml), and the mixture was refluxed for 3 hours. The solution was poured into water and extracted with chloroform. The chloroform solution was dried over sodium sulfate, filtered, and the filtrate was dried under reduced pressure. The obtained solid was produced using column chromatography (developing solvent: chloroform) (yield: 2.1 g, yield: 96%).
¹ H HNR (300 MHz, CDCl ₃ , TMS, RT): δ 8.63-8.60 (1H, d), 8.55-8.52 (1H, d), 8.50-8.48 (1H, d), 8.11-8.09 (1H, d ), 7.94-7.92 (1H, t), 7.79-7.66 (3H, m)

Synthesis of 9-benzothienylphenanthridylline Benzo [b] thiophen-2-ylboronic acid (884 mg, 5.0 mmol), 9-chlorophenanthridylline (1.0 g, 4.8 mmol) in tetrahydrofuran (30 ml), palladium catalyst ( 160 mg, 0.14 mmol) and 2M aqueous sodium carbonate solution (20 ml) were added, and the mixture was refluxed for 5 hours under N ₂ substitution. The reaction solution was poured into water, extracted with chloroform, the chloroform solution was dried over sodium sulfate, filtered, and the filtrate was dried under reduced pressure. The obtained solid was produced using column chromatography (developing solvent: chloroform) (yield: 1.15 g, yield: 78%).
¹ H HNR (300 MHz, CDCl ₃ , TMS, RT): δ 8.74-8.71 (1H, d), 8.67-8.65 (1H, d), 8.62-8.59 (1H), 8.26-8.23 (1H, d), 7.97-7.88 (3H, m), 7.86 (1H, s), 7.80-7.67 (3H, m), 7.44-7.41 (2H)

Synthesis of bis [9- (2'-benzothienyl) -phenanthrinate-N, C ^{3 '} ] iridium (acetylacetone)
2-Ethoxyethanol (30 ml) and water (10 ml) were added to 9-benzothienylphenanthridylline (706 mg, 2.3 mmol) and iridium chloride trihydrate (purity: 90%, 398 mg, 1.0 mmol) for 16 hours. Refluxed. The solution was cooled to room temperature and the resulting solid was filtered. To the obtained solid (343 mg, 0.20 mmol), 2-methoxyethanol (20 ml), acetylacetone (1 ml) and sodium carbonate (180 mg) were added and refluxed for 2 hours. The solution was cooled to room temperature and the resulting solid was filtered. The obtained solid was produced using column chromatography (developing solvent: chloroform) (yield: 293 mg, yield: 80%).
¹ H HNR (300 MHz, CDCl ₃ , TMS, RT): δ 9.35-9.33 (2H, d), 8.72-8.70 (2H, d), 8.46-8.44 (2H, d), 7.98-7.87 (4H, m ), 7.85-7.82 (2H, d), 7.73-7.70 (2H, d), 7.43-7.38 (2H, t), 7.20-7.15 (2H, t), 7.04-6.99 (2H, m), 6.52-6.51 (4H, d), 4.50 (1H, s), 1.39 (6H, s)

Table 3 shows phosphorescence spectra of (btq) ₂ Ir (acac), (btiq) ₂ Ir (acac), and (btph) ₂ Ir (acac) in 1,2-dichloroethane. The phosphorescence of these compounds was dependent on oxygen concentration (data not shown).

In each of Reference Examples 1 to 3, by reacting succinylacetone (sa) instead of acetylacetone (acac), (btq) ₂ Ir (sa), (btiq) ₂ Ir (sa), (btph) ₂ Ir (sa) can be obtained. Then, (btq) ₂ Ir (sa), (btiq) ₂ Ir (sa), (btph) ₂ Ir (sa) are reacted with an amino acid or peptide to form a water-soluble iridium complex ((btq) ₂ Ir ( sa-asp), (btiq) ₂ Ir (sa-asp), (btph) ₂ Ir (sa-asp), (btq) ₂ Ir (sa-asp-asp), (btiq) ₂ Ir (sa-asp- asp), (btph) ₂ Ir (sa-asp-asp), and the like.
From Table 3, since (btq) ₂ Ir (acac), (btiq) ₂ Ir (acac), (btph) ₂ Ir (acac) emits phosphorescence, (btq) ₂ Ir (sa-asp), (btiq ) ₂ Ir (sa-asp), (btph) ₂ Ir (sa-asp), (btq) ₂ Ir (sa-asp-asp), (btiq) ₂ Ir (sa-asp-asp), (btph) ₂ It can be understood that iridium complexes such as Ir (sa-asp-asp) are also water-soluble phosphorescent compounds.

  According to the oxygen concentration detection reagent of the present invention, the oxygen concentration in an aqueous solution can be quantified with high sensitivity and in real time, and is useful as an intracellular oxygen concentration quantification reagent, a hypoxic cell imaging agent, and the like.

(btp) ₂ Ir (sa), (btp) ₂ Ir (sa-NH ₂ ), (btp) ₂ Ir (sa-Asp), (btp) ₂ Ir (sa-Asp-Asp) and control (btp) FIG. 2 is a graph showing absorption and phosphorescence spectra of ₂ Ir (acac). Ar replacement solution, shows the phosphorescence spectrum of air saturated solution _{(btp) 2 Ir (sa-} Asp-Asp).

Claims (4)

A compound represented by any one of the following general formulas (I) to (IV) (n represents a natural number of 1 to 5, R represents an amino acid selected from tyrosine, serine, threonine, aspartic acid, glutamic acid, lysine and arginine ) Represents a residue or a peptide residue comprising the amino acid ).

The compound according to claim 1, wherein the amino acid residue or peptide residue is a residue of a peptide consisting of aspartic acid residue or aspartic acid. A compound represented by the following formula (V) or (VI).

An oxygen concentration measurement reagent comprising the compound according to any one of claims 1 to 3 .

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