Inorg. Chem. zyxwvut 1995,34, zyxwvut 3385-3395 3385 Synthesis and Photophysical Properties of Mono(2,2’,2’’-terpyridine) Complexes of Ruthenium(I1) Benjamin J. Coe, David W. Thompson, Christopher T. Culbertson, Jon R. Schoonover, and Thomas J. Meyer* Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290 Received March 16, zyxwvutsr 1994@ A series of [Ru(tpy)(X)(Y)(Z)]”+ complexes have been synthesized (tpy zyxw = 2,2’,2”-terpyridine: X = tri- phenylphosphine (PPh3); trans Y = Z = trifluoroacetate (CF3CO2-), n = 0 (1); trans Y = Z = 4-ethylpyridine (4-Etpy), n = 2 (2); trans Y = Z = 4-(dimethylamino)pyridine (DMAP), n = 2 (3); Y = 4-Etpy, Z = chloride (Cl-), n = 1 zyxwvutsr (4); cis Y = Z = 4-Etpy, n = 2 (5); X = C1-; trans Y = Z = 4-Etpy, n = 1 (6); X = Y = Z = 4-Etpy, n = 2 (7)) and isolated as their PF6- salts. UV-visible spectroscopic and electrochemical studies have been conducted and photochemical and photophysical properties of representative examples determined. Emission, absorption, and electrochemical properties depend on the nonchromophoric ligands and the coordination geometry. The complexes investigated emit in 4:l (vlv) EtOWMeOH glasses at 77 K and have lifetimes which range from 1.1 to 11 zyxwvuts .O ,us depending on the ancillary ligands. Through a combination of emission spectral fitting and resonance Raman measurements on [Ru(tpy)z](PF6)2, the acceptor characteristics of tpy as a chromophoric ligand have been analyzed. At room temperature the Ru(I1) mono-tpy complexes are short-lived, weak emitters. Emission quantum yields and lifetimes for [Ru(tpy)(4-Etpy)3](PF6)2 (7) and [Ru(tpy)z](PF& in 4: 1 (vlv) EtOWMeOH are strongly temperature dependent from T = 90-270 K. These results are consistent with the existence of low- lying dd states which are responsible for the short excited state lifetimes at room temperature and the appearance of ligand-loss photochemistry for 7. Introduction The metal to ligand charge transfer (MLCT) excited states of polypyridine complexes have been used extensively as a chromophoric basis for the study of photoinduced electron and energy transfer in molecular assemblies.’ Many of these assemblies have resulted from coordination chemistry which allows only a limited degree of control over molecular structure. Further development requires more complete control over structure by using precisely d e f i e d synthetic strategies. Recent reports featuring such an approach concem Ru(I1) and Os(I1) bis(terpyridine) complexes,2 Ru(II) functionalized amino acid @ Abstract published in Advance ACS Abstracts, February 1, 1995. (1) (a) Meyer, T. J. Acc. Chem. Res. 1989,22, 163. (b) Belser, P. Chimia 1990,44, 226. (c) Meyer, T. J. Pure Appl. Chem. 1990,62, 1003. (d) Balzani, V.; Scandola, F. Supramolecular Photochemistry; Ellis Horwood: Chichester, U.K., 1991. (2) (a) Collin, J.-P.; Guillerez, S.; Sauvage, J.-P.; Barigelletti, F.; De Cola, L.; Flamigni, L.; Balzani, V. Inorg. Chem. 1991,30,4230. (b) Collin, J.-P.; Guillerez, S.; Sauvage, J.-P.; Barigelletti, F.; De Cola, L.; Flamigni, L.; Balzani, V. Inorg. Chem. 1992, 31, 4112. (3) (a) Mecklenburg, S. L.; Peek, B. M.; Erickson, B. W.; Meyer, T. J. J. Am. Chem. SOC. 1991, 113, 8540. (b) Mecklenburg, S. L.; Peek, B. M.; Schoonover, J. R.; McCafferty, D. G.; Wall, C. G.; Erickson, B. W.; Meyer, T. J. J. Am. Chem. SOC. 1993, 115, 5479. (4) (a) Campagna, S.; Denti, G.; Serroni, S.; Ciano, M.; Balzani, V. J. Am. Chem. SOC. 1992, 114, 2944. (b) Belser, P.; von Zelewsky, A.; Frank, M.; Seel, C.; Vogtle, F.; De Cola, L.; Barigelletti, F.; Balzani, V. J. Am. Chem. SOC. 1993, 115, 4076. 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SOC., Dalton Trans. 1994, 1409. 0020- 166919511 334-3385$09.O0/0 as~emblies,~ and oligometallic mays containing bridging ligands based on both bipyridines4 and terpyridine~.~ There are numerous studies on the photochemistry and photophysics of ruthenium@) complexes with 2,2‘-bipyridine (bpy) as the acceptor ligand6but relatively few reports concem- ing related 2,2’,2”-terpyridine (tpy) This is largely because [Ru(tpy)~]~+ and its derivatives exhibit very short excited state lifetimes at room temperature in solution (for (a) Bryant, G. M.; Ferguson, J. E.; Powell, H. K. J. Aust. J. Chem. 1971, 24, 257. (b) Kalyanasundaram, K. Coord. Chem. Rev. 1982, 46, 159. (c) Watts, R. J. J. Chem. Educ. 1983,60, 834. (d) Meyer, T. J. Pure Appl. Chem. 1986, 58, 1193. (e) Juris, A.; Balzani, V.; Barigelletti, F.; Campagna, S.; Belser, P.; von Zelewsky, A. Coord. Chem. Rev. 1988, 84, 85. (fl DeArmond, M. K.; Myrick, M. L. Acc. Chem. Res. 1989, 22, 364. (g) Krausz, E.; Fergusoh, J. Prog. Inorg. 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