Russian Journal of Coordination Chemistry, Vol. 30, No. 2, 2004, pp. 110–114. Translated from Koordinatsionnaya Khimiya, Vol. 30, No. 2, 2004, pp. 120–124. Original Russian Text Copyright © 2004 by Dudnik, Ivanov, Tomilova, Zefirov.

Synthesis and Study of Ruthenium Phthalocyanine Complexes A. S. Dudnik*, A. V. Ivanov**, L. G. Tomilova**, and N. S. Zefirov* *Moscow State University, Vorob’evy gory, Moscow, 119899 Russia **Institute of Physiologically Active Substances, Chernogolovka, Moscow oblast Russia Received December 30, 2002

Abstract—Methods of synthesis of ruthenium tetra-tert-butylphthalocyaninate (PctRu) were developed. The synthesis performed in both autoclave and in open system (in isoamyl alcohol in the presence (1,8-diazabicyclo[5,4,0]undecene) resulted in PctRu(ëé) containing CO as axial ligand. When quinoline was used in the synthesis of PctRu, the PctRu(Iqnl)2 complex was obtained with two isoquinoline molecules (Iqnl) as axial ligands, which were detached consecutively in the course of thermogravimetric analysis. The compounds formed were studied by different physicochemical methods: electron, IR, and 1H NMR spectroscopies, MALDI-TOF mass spectroscopy, thermogravimetric and elemental analyses.

Metal phthalocyaninates (PcM) have been studied widely in recent decades. An interest in these compounds is explained by the fact that phthalocyanines, which are synthetic analogs of frequently encountered natural porphyrins, have unique physicochemical properties. Complexes of ruthenium with phthalocyanine and its derivatives exhibit semiconducting properties [1]. The ruthenium phthalocyaninate complexes are promising catalysts in the reactions of hydrocarbon oxidation [2–5]. The analysis of data reported shows that the studies mainly dealt with unsubstituted ruthenium phthalocyaninate (PcRu). The low solubility of the complexes formed prevented their isolation as individual compounds, which was responsible for publication of numerous contradictory data on their structures. Different procedures have been developed for synthesizing ruthenium complexes with phthalocyanine: synthesis by fusion [6–8], synthesis in high-boiling solvents [9–11], synthesis in coordinating solvents [12, 13], synthesis in alcohol solvent in the presence of organic base [14], and synthesis with the use of a free ligand [12]. The ruthenium phthalocyaninate complexes synthesized by different methods were found to have different structures and physicochemical properties [1, 12]. The introduction of bulky tert-butyl groups into phthalocyanine ring significantly increases solubility of the complexes in common organic solvents. However, the synthesis of tetra-tert-butyl-substituted phthalocyanine of ruthenium is described only in few works, while the reported data are contradictory [1, 15].

The aim of this work was to synthesize ruthenium tetra-tert-butylphthalocyaninate (PctRu) by different methods and to compare the structures and properties of the complexes formed depending on the method used. EXPERIMENTAL The starting reagents in the synthesis of the PctRu complexes were RuCl3 · 3H2O and 4-tert-butyl-o-phthalodinitrile. All solvents and starting reagents were purified directly before use following standard procedures. Synthesis of PctRuII(CO) (I). (a) A mixture of 4-tert-butyl-o-phthalodinitrile (1.50 g, 8.20 mmol) and RuCl3 · 3H2O (0.15 g, 0.57 mmol) was placed in autoclave and 1,8-diazabicyclo[5,4,0]undecene (DBU) (0.30 ml) and ethyl alcohol (5 ml) were added. Autoclave was tightly closed and the reaction mixture was heated at 250°ë under 4560 kPa for 2 h. After the reaction was over, the excess of dinitrile was removed in vacuum (130°ë, 20 mmHg), while the residue was dissolved in chloroform and purified by colon chromatography (50 × 5 cm colon, silica gel 70–230 (Lancaster); first, with the CHCl3 eluent and then Et2O). After the removal of the solvent, complex I formed as dark blue powder in the yield of 75% (0.36 g). MALDI-TOF/DHB mass spectrum: for [PctRu]+, found m/z = 838.580, calcd. m/z = 838.019; for +

[PctRu ] 2 , found m/z = 1676.971, calcd. m/z = 1676.038.

1070-3284/04/3002-0110 © 2004 åÄIä “Nauka /Interperiodica”

SYNTHESIS AND STUDY OF RUTHENIUM PHTHALOCYANINE COMPLEXES

The electronic absorption spectrum in C6H6, λ, nm (ε, l mol–1 cm–1): 298 (7.21 × 104), 345 sh, 588 (2.49 × 104), 625 sh, 651 (1.17 × 105). NMR (500 MHz, DMSO-d6, SiMe4 standard; δ, ppm): 1.74 s (36H, C(CH3)3); 8.17 dd (4H, PcH3, J3–4 = 8.5 Hz, J3–1 = 2.0 Hz); 9.14–9.22 d (4H, PcH1, J1–3 = 2.0 Hz); 9.27 d (4H, PcH4, J 4–3 = 8.5 Hz). 1H

IR spectrum (CsI, ν, cm–1): 2956.94, 2922.80, 2850.98, 1959.14 ν(C=O), 1712.64, 1614.57, 1492.11, 1462.61, 1393.21, 1363.80, 1321.23, 1282.45, 1257.11, 1234.95, 1215.06, 1191.98, 1154.96, 1122.57, 1095.70, 1051.67, 939.76, 830.36, 755.51, 693.89, 669.39. (b) A two-necked 50-ml flask equipped with fractionating column (containing calcium chloride) and gas-supplying tube was filled with argon. Then, 4-tertbutyl-o-phthalodinitrile (0.53 g, 2.90 mmol) and RuCl3 · 3H2O (0.15 g, 0.57 mmol) were placed in the flask and DBU (0.40 g) and isoamyl alcohol (30 ml) were added. The reaction mixture was boiled for 12 h, cooled to 20°C, and the solvent was distilled off in the rotary evaporator. All procedures were carried out in the atmosphere of argon. The residue formed was dissolved in chloroform and purified using column chromatography method (a 50 × 5 cm column, aluminium oxide 5–40 (Lachema), CHCl3 eluent). According to the electronic absorption and IR spectra, the fraction (formed in the yield of 0.05 g, 9.33%) was identified as complex I. Synthesis of PctRuII(Iqnl)2 (II), where Iqnl—isoquinoline. (c) A two-necked 50-ml flask equipped with fractionating column (containing calcium chloride) and gas-supplying tube was filled with argon. Then, 4-tertbutyl-o-phthalonitrile (0.89 g, 4.80 mmol) and RuCl3 · 3H2O (0.25 g, 0.96 mmol) were placed in the flask and quinoline (25 ml) was added. The mixture was boiled in the atmosphere of argon for 4 h and cooled to 20°C in the stream of argon; quinoline was distilled off in vacuum. The remaining residue was dissolved in benzene and purified by the column chromatography method (a 30 × 3 cm column, silica gel 70–230 (Lancaster), C6H6 eluent). After the solvent was removed, complex II (the yield 0.50 g, 48%) and [PctRuII(Iqnl)]2 (III) (the yield 0.05 g, 5%) were obtained as blue-green powders. Complex II: Rf = 0.76 (C6H6). For C66H62N10Ru anal. calcd. (%): C, 72.31; Found (%): C, 72.07;

H, 5.70; H, 6.22;

N, 12.78. N, 12.17.

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1H NMR (300 MHz, CDCl , SiMe standard; δ, 3 4 ppm): 1.70–1.80 s (36H, C(CH3)3); 2.40 d (H, IqnlH3, J3–4 = 7.0 Hz); 3.17 s (2H, IqnlH1); 5.51 d (2H, IqnlH4, J4–3 = 7.0 Hz); 6.50 d (2H, IqnlH8, J8–7 = 8.0 Hz); 6.65 d (2H, IqnlH5, J5–6 = 8.0 Hz); 6.80 ddd (2H, IqnlH6, J6– 8 = 1.0 Hz, J6–5 = 8.0 Hz); 6.95 ddd (2H, IqnlH , J7–5 = 7 1.0 Hz, J7–8 = 8.0 Hz); 7.95 dd (4H, PcH3, J3–4 = 8.5 Hz, J3–1 = 2.0 Hz, PcH1, J1–3 = 2.0 Hz); 9.05–9.15 d (4H, PcH1, J1–3 = 2.0 Hz); 9.20 d (4H, PcH4, J4–3 = 8.5 Hz). +

MALDI-TOF/DHB mass spectrum: for [PctRu ] 2 , found m/z = 1678.8, calcd. m/z = 1676.038. The electronic absorption spectrum in C6H6, λ, nm (ε, l mol–1 cm–1): 314 (1.03 × 105), 370 sh, 437, 575 sh, 630 (5.97 × 104). IR spectrum (KRS-5, ν, cm–1): 2961.5, 2923.33, 2863.34, 1613.72, 1492.89, 1392.77, 1363.32, 1317.07, 1279.48, 1258.72, 1191.17, 1151.85, 1127.52, 1114.05, 1091.39, 1051.62, 1022.84, 958.60, 941.34, 915.42, 894.90, 861.00, 822.10, 801.26, 756.74, 695.28, 669.59, 640.42, 533.02, 473.01, 401.11. Complex III: Rf = 0.41 (C6H6). The electronic absorption spectrum in C6H6 (λ, nm): 339, 444, 567, 630. MALDI-TOF/DHB mass spectrum: for [PctRu(Iqnl)]+, found m/z = 965.6, calcd. m/z = 967.2; for [Pc tRu]2(Iqnl)+, found m/z = 1799.8, calcd. m/z = +

1805.2; for [PctRu(Iqnl) ] 2 , found m/z = 1927.7; calcd. m/z = 1933.3. IR spectrum (KRS-5, ν, cm–1): 3062.15, 2957.58, 2924.78, 2858.18, 1773.59, 1722.42, 1615.18, 1594.95, 1558.52, 1504.30, 1463.66, 1402.30, 1392.35, 1363.51, 1317.60, 1281.97, 1256.99, 1198.98, 1152.23, 1130.44, 1117.36, 1097.74, 1057.65, 940.46, 917.54, 894.88, 827.78, 782.23, 754.14, 694.29, 669.47, 640.43, 609.03, 589.67, 536.23, 473.14, 444.89, 412.56, 362.84, 352.24, 340.09, 323.29, 307.91, 301.21, 286.76, 280.13. The electronic absorption spectra in UV and visible regions were recorded on a Heλios-α (Thermo Spectronic Company) with quartz cells 5 and 10 mm thick. IR spectra were taken on a Nexus IR-Fourier spectrometer (Nicolet Company) with samples as thin films and recorded on KRS-5 and CsI plates. Thermograms were registered on a Q-1500D derivatograph (with the heating rate 5°C/min, 0–500°C, N2). 1H NMR spectra were recorded on Bruker AM-300 and Bruker DRX500 spectrometers. MALDI-TOF spectra were taken on Reflex III instrument with 2,5-dihydroxybenzoic acid used as matrix. The thin-layer chromatography was carried out on Silufol UV-254 plates. Vol. 30

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RESULTS AND DISCUSSION Compounds I–III were synthesized by the following scheme: CO

t-Bu

t-Bu

N N

N

t-Bu

CN

N

N (I) Iqnl

t-Bu

+ RuCl3 · 3H2O

N N

N ‡, b

CN

Ru

c

t-Bu t-Bu

N N

N

Ru

N N N

N N t-Bu

t-Bu

Iqnl (II) + Iqnl

t-Bu

t-Bu

N N N N

Ru

N

N

N

t-Bu t-Bu

N t-Bu t-Bu

N N N N

Ru

N

N

N N

t-Bu

t-Bu

Iqnl (III)

The synthesized metal complexes have high solubilities in standard organic solvents and thus were chromatographically purified and isolated as individual compounds. The most suitable method of preparing PctRu in high yields is the synthesis in autoclave. The electronic absorption spectra in UV and visible regions (Fig. 1a) and the data of thin-layer chromatography confirm that the synthesized complex I is an individual compound. MALDI-TOF mass spectra revealed molecular ions + with masses corresponding to [PctRu]+ and [PctRu ] 2 . The laser irradiation of complex I in the course of mass spectrometric analysis induces dimerization. Paper [1] reports the synthesis of PctRuII containing no axial ligands. It should be noted that the question whether the molecule of the synthesized metal complex contains CO is often ignored by many authors. We synthesized

PctRuII under conditions similar to those used in [1] and obtained the complex whose electronic absorption spectrum typical of the classic phthalocyanine (with the Q band at 651 nm). However, IR data confirm that the complex synthesized contains the CO molecule (ν = 1959.14 cm–1), which makes possibility of producing a complex free of CO as the axial ligand under the indicated conditions doubtful. Moreover, the spectral characteristics reported in [1] make the purity of the PctRu complex obtained by these authors questionable, since its absorption spectrum has no definitely pronounced shoulder (λ = 625 nm) or vibration satellite (λ = 588nm), whereas its IR spectrum contains a band ν(C≡N) at 2233 cm–1. One should note that the presence of the CO in the molecule does not change the electronic absorption spectrum typical of PcM, although two similar axial ligands of the amine type induce hypsochromic shift of the Q-band [16].

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We synthesized PctRu(Iqnl)2 with isoquinoline molecules as axial ligands using analogous procedure as in the synthesis of unsubstituted PctRu in quinoline [12].The NMR data confirmed the presence of Iqnl as an impurity in commercial quinoline, rather than the presence of quinoline as axial ligand, which agrees with the data [12] obtained for unsubstituted complex. The upfield shift of signals from protons of isoquinoline ring IqnlH1 and IqnlH3 can be explained by cone shielding of the 18-electron aromatic π-system of phthalocyanine [13]. The data obtained agree with the data for unsubstituted Ru phthalocyaninate [17]. The MALDITOF mass spectrometrical analysis showed the molecule ionization is attended by its dimerization and elimination of isoquinoline molecules: 2PctRu(Iqnl)2 t-Bu

t-Bu

–4Iqnl

N

N

Ru N N

N

N

N Ru

N N

N

1.5 298

1.0 345

0.5

588

0 1.0

314

(b)

0.8 630

0.6

0.2 N

437

0 t-Bu t-Bu

0.7

339

(c)

0.6 0.5

N

0.4 630

0.3

N t-Bu

651

575

N

t-Bu t-Bu

(‡)

0.4

N N

A 2.0

113

t-Bu (IV)

which is in conformity with the data reported in [16, 18]. The molecular ion peak corresponds particularly to structure IV. The absorption spectra of complex II (Fig. 1b) also suggest the ligands in axial positions, which is confirmed by a noticeable broadening of the Q-band and reduction of its intensity as was also observed in [16]. IR spectrum of complex II contains two absorption bands at 533 and 473 cm–1 due to the stretching vibrations of the Ru–N(Pc) and Ru–N(Iqnl) bonds, respectively. The thermogravimetric analysis in the atmosphere of nitrogen showed that the first isoquinoline molecule is eliminated at 365°ë, while the second molecule is detached at 488°ë. The total mass loss is 22% (the calculated value is 22.5%). When PctRu(Iqnl)2 is heated in a high vacuum for 6–8 h, isoquinoline is removed completely, as confirmed by 1H NMR data. This means that the obtained PctRu contains four isomers that differ in position of the tert-butyl group in the phthalocyanine ring. It should be mentioned that one more ruthenium complex was obtained in a low yield (that was not discovered by the authors of [12]). Its electronic absorption, IR, and mass spectra, as well as Rf measured in different solvents differ from those of the main product. IR RUSSIAN JOURNAL OF COORDINATION CHEMISTRY

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0.2

444

0.1 0 300

400

500 600 λ, nm

700

800

Fig. 1. Electronic absorption spectra of (a) complex I, (b) complex II, and (c) complex III.

and mass spectrometry data suggest that this compound has composition [PctRu(Iqnl)]2, although the final conclusion about the structure of this complex requires Raman spectra that could confirm the Ru=Ru bond. The absorption spectra of complex III confirm that the ligands are in axial positions (Fig. 1c). Mass spectra of complex III showed that the ionization process requires three molecular ions, namely, + [PctRu(Iqnl)] 2 , [PctRu(Iqnl)]+, and [PctRu=RuPct(Iqnl)]+. In order to synthesize complex I, we used the procedure of boiling the starting reagents (RuCl3 · 3H2O and 4-tert-butyl-o-phthalodinitrile) in isoamyl alcohol in the presence of DBU. The chosen procedure provides mild conditions of synthesis (which is important for the applied phthalogens that are destroyed at high temperVol. 30

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atures), but in the case of the Ru complexes, it affords the target product in low yield. The electronic absorption spectra of the obtained compounds are typical of classic phthalocyanine and do not confirm the axial ligands. However, IR data showed that the synthesized complex contains the CO molecules (absorption bands at 1981.77 and 1964.32 cm–1). The results of this work indicate that it is rather difficult to synthesize PctRu with a square-planar structure, whose ligands are not axial. The most suitable method of synthesizing PctRu is the decomposition of the PctRuL2 complexes (L = NH3 [1], Iqnl, Py [12], etc) at high temperature and vacuum. However, none of the methods of synthesizing PctRu with no axial ligands (CO, phthalonitrile, etc) and electronic absorption spectrum typical of phthalocyanines has been reported in the literature. Since in the temperature interval 130–250°ë the yield of the complex being synthesized increases, we made an attempt to synthesize compound I and replace isoamyl alcohol by a solvent with a higher boiling point (Ó-dichlorobenzene, Ó-DCB). The replacement of alcohol by a solvent free of hydroxyl groups results in a sharp reduction in the yield and in an increase in the number of forms obtained in the synthesis that cannot be isolated as individual compounds. This is likely to occur due to the catalytic participation of alcoholate ion in the formation of phthalocyanine ring [19], which is impossible in the case of Ó-DCB. This work made it possible to develop methods of synthesizing different Ru phthalocyanine complexes. As a result, new method was suggested that can be used to obtain ruthenium tetra-tert-phthalocyanine in isoamyl alcohol in the presence of organic base (DBU). The coordinatively unsaturated ruthenium in phthalocyanine complexes was found to be bound to the axial ligands that eliminate in succession on heating. We established that the ruthenium phthalocyanine complexes can be obtained under optimal conditions when they are synthesized in autoclave with boiling of the starting reagents in quinoline. ACKNOWLEDGMENTS The authors are thankful to Yu.G. Gorbunova (Institute of General and Inorganic Chemistry) for recording IR spectra.

This work was supported by the Russian Foundation for Basic Research, (project no. 00-03-32658) and ISTC (project no. 1526). REFERENCES 1. Hanack, M., Kamenzin, S., Kamenzin, C., and Subramanian, L.R., Synth. Met., 2000, vol. 110, no. 2, p. 93. 2. Capobianchi, A., Paoletti, A.M., Pennesi, G. et al., Inorg. Chem., 1994, vol. 33, no. 21, p. 4635. 3. Balkus. K.J., Eissa, M., and Levado, R. J. Am. Chem. Soc., 1995, vol. 117, no. 43, p. 10753. 4. Kropf, H., Tetrahedron Lett., 1967, vol. 18, no. 7, p. 659. 5. Alt, H., Binder, H., and Sandstede, G., J. Catalysis, 1973, vol. 28, no. 1, p. 8. 6. Berezin, B.D. and Sennikova, G.V., Dokl. Akad. Nauk SSSR, 1964, vol. 159, no. 1, p. 117. 7. Berezin, B.D. and Sennikova, G.V., Dokl. Akad. Nauk SSSR, 1962, vol. 146, no. 3, p. 604. 8. Krueger, P.C. and Kenny, M.E., J. Inorg. Nucl. Chem., 1963, vol. 25, no. 3, p. 303. 9. Rossi, G., Gardini, M., Pennesi, G., et al., J. Chem. Soc., Dalton. Trans., 1989, no. 1, p. 193. 10. Capobianchi, A., Pennesi, G., Paoletti, M., et al., Inorg. Chem., 1996, vol. 35, no. 16, p. 4643. 11. Rihter, B.D., Kenney, M.E., Ford, W.E., and Rodgers, A.J., J. Am. Chem. Soc., 1990, vol. 112, no. 22, p. 8064. 12. Hanack, M., Osio-Barcina, J., Witke, E., and Pohmer, J., Synthesis, 1992, nos. 1–2, p. 211. 13. Hanack, M., Knecht, S., and Polley, R., Chem. Ber., 1995, vol. 128, no. 9, p. 929. 14. Eberhardt, W. and Hanack, M., Synthesis, 1998, no. 12, p. 1760. 15. Hanack, M. and Vermehren, P., Chem. Ber., 1991, vol. 124, no. 9, p. 1733. 16. Hanack, M. and Kang, Y-G., Chem. Ber., 1991, vol. 124, no. 7, p. 1607. 17. Polley, R. and Hanack, M., Synthesis, 1997, no. 3, p. 295. 18. Farrel, N., Dolphin, D.H., and James, B.R., J. Am. Chem. Soc., 1978, vol. 100, no. 1, p. 324. 19. Tomoda, H., Saito, S., Ogawa, S., and Shiraishi, S., Chem. Lett., 1980, p. 1277.

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