Solid-State Structure Dependence of the Molecular Distortion and Spectroscopic Properties of the Cu(I) Bis(2,9-dimethyl-1,10-phenanthroline) Ion

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 D2d 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 BF4 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.