Structural and Photophysical Studies of Cu(NN)2+ Systems in the Solid State. Emission at Last from Complexes with Simple 1,10-Phenanthroline Ligands

For a variety of reasons, relating the photophysical properties of a copper phenanthroline to a structure in solution is problematic. To elucidate some of the issues involved, in this paper we describe the crystal and molecular structures of a series of Cu(NN)2+-containing systems along with spectral data obtained from the solids themselves. The NN ligands investigated are tmp (3,4,7,8-tetramethyl-1,10-phenanthroline), dpdmp (2,9-diphenyl-4,7-dimethyl-1,10-phenanthroline), dptmp (2,9-diphenyl-3,4,7,8-tetramethyl-1,10-phenanthroline), and dipp (2,9-diisopropyl-1,10-phenanthroline). The results show that a flattening distortion can have a large impact on the spectroscopic properties of a Cu(NN)2+ system, whereas a typical rocking distortion has comparatively little effect. The reflectance spectra of orange or orange-red salts that have approximately perpendicular phenanthroline ligands exhibit absorption bands in the neighborhood of 460 nm along with a shoulder at longer wavelength. In the other limit, when...