Solid-State Structure Dependence of the Molecular Distortion and Spectroscopic Properties of the Cu(I) Bis(2,9-dimethyl-1,10-phenanthroline) Ion Andrey Yu. Kovalevsky, Milan Gembicky, Irina V. Novozhilova, and Philip Coppens* Chemistry Department, UniVersity at Buffalo, State UniVersity of New York, Buffalo, New York 14260 Received July 25, 2003 The relation between the geometry and spectroscopic properties of a series of salts of the Cu(I) bis(2,9-dimethyl- 1,10-phenanthroline) ion, (Cu (I) (dmp) 2 ) + , is explored. The distortions from the idealized D 2d geometry, which include flattening, rocking of the dmp ligands, and displacement of the Cu atoms out of the dmp planes, show considerable variation, indicating the importance of packing forces in the crystalline environment. The change in the absorption spectra upon flattening of the complex, expressed as the variation of the angle between the dmp planes, which varies from 88° in the BF 4 and tosylate salts to 73° in the picrate, agrees qualitatively with parallel DFT calculations. No correlation is found between ground state geometry and luminescence lifetimes, recorded both at room temperature and at 16 K. The low temperature lifetimes vary by a factor of 8 among the (Cu (I) (dmp) 2 ) + salts examined, the longest lifetime (2.4 µs at 16 K) being observed for the tosylate salt. Introduction A fundamental understanding of photoinduced electron transfer requires knowledge of the geometry changes ac- companying the transfer process. As part of our time-resolved diffraction studies on the geometry of molecular excited states, 1 we have, as a necessary first step, examined the variation in the ground state structure and spectroscopic behavior of Cu (I) bisphenanthroline complexes, which un- dergo photoinduced metal-to-ligand charge transfer (MLCT). 2,3 They absorb light in the visible spectral region and show phosphorescence with nanosecond to microsecond scale lifetimes. The current paper concerns the relation between the structural variation and spectroscopic changes of a series of salts of the Cu (I) bis(2,9-dimethyl-1,10 phenanthroline) ion, (Cu (I) (dmp) 2 ) + . This is the first time that a series of solids with an identical Cu (I) cation but different molecular environ- ment has been systematically explored by both crystal- lographic and spectroscopic methods. Experimental Section Preparation of the Copper(I) Complexes. Starting Materials. CuBr, Cu(BF 4 ) 2 ‚6H 2 O, Cu(NO 3 ) 2 ‚6H 2 O, [Cu(NCCH 3 ) 4 ]PF 6 , [Cu(CNCH 3 ) 4 ]BF 4 , copper metal powder, 1,10-dimethyl-2,9- phenanthroline (dmp), tetramethylammonium tosylate (TMATos), sodium 9,10-anthraquinone-2-sulfonate (NaAQSO 3 ), and L-ascorbic acid are commercially available from Aldrich and were used without further purification. Tetramethylammonium calix[4]arenate (TMACalix) was synthesized by a method of Harrowfield et al. 4 Tetramethyl- ammonium picrate (TMAPic) was prepared with quantitative yield by combining a saturated solution of picric acid (Aldrich, Inc.) in water and an equimolar amount of tetramethylammonium hydroxide (25% in water) (Aldrich, Inc.). The yellow crystalline precipitate of TMAPic was filtered and dried overnight over molecular sieves. [Cu(dmp) 2 ]BF 4 (1), [Cu(dmp) 2 ]BF 4 ‚0.5Acetone (2), and [Cu(dmp) 2 ]BF 4 ‚0.5dmp (3). The [Cu(dmp) 2 ]BF 4 complex was prepared by the method described previously. 5 Crystals of 1 were obtained by slow evaporation of an acetonitrile solution, while crystals of 2 were prepared by diethyl ether vapor diffusion into * To whom correspondence should be addressed. E-mail: coppens@ buffalo.edu. (1) (a) Kim, C. D.; Pillet, S.; Wu, G.; Fullagar, W. K.; Coppens, P. Acta Crystallogr., Sect. A 2002, 58, 133-137. (b) Novozhilova, I.; Volkov, A. V.; Coppens, P. J. Am. Chem. Soc. 2003, 125, 1079-1087. (c) Coppens, P.; Novozhilova, I. Faraday Discuss. 2002, 122,1-11. (d) Coppens, P. Chem. Commun. 2003, 1317-1320. (e) Coppens, P.; Graber, T.; Vorontsov, I.; Wu, G.; Kovalevsky, A. Yu.; Gembicky, M.; Chen, Y.-S. To be published. (2) Scaltrito, D. V.; Thompson, D. W.; O’Callaghan, J. A.; Meyer, G. J. Coord. Chem. ReV. 2000, 208, 243-266. (3) Armaroli, N. Chem. Soc. ReV. 2001, 30, 113-124. (4) Harrowfield, J. M.; Ogden, M. I.; Richmond, W. R.; Skelton, B. W.; White, A. H. J. Chem. Soc., Perkin Trans. 1993, 2, 2183-2190. (5) McMillin, D. R.; Buckner, M. T.; Ahn, B. T. Inorg. Chem. 1977, 16, 943-945. Inorg. Chem. 2003, 42, 8794-8802 8794 Inorganic Chemistry, Vol. 42, No. 26, 2003 10.1021/ic0348805 CCC: $25.00 © 2003 American Chemical Society Published on Web 11/26/2003