Spectroscopic and density functional theory studies of 1,10-phenanthroline, its radical anion, and [Cu(Phen)(PPh3)2]+

The vibrational spectra (Raman and IR) of 1,10-phenanthroline (phen), its perdeuterated analogue (d(8)-1,10-phenanthroline, d(8)-phen), and the copper(I) complexes [Cu(phen)(PPh3)(2)](+) and [Cu(d(8)-phen)(PPh3)(2)](+) have been measured. These spectra may be modeled using DFT calculations (B3LYP/6-31G(d)). The calculated structure compares favorably with crystallographic data. The time-resolved resonance Raman spectra of the copper(I) complexes were used to provide spectral signatures of phen(.-) and d(8)-phen(.-). Geometries and vibrational spectra of the radical anions may be calculated in two ways: first as phen(.-), which has been previously shown to be a B-2(1) state. Calculations with B3LYP require the 6-311 +G(d,p) basis set in order to predict this state correctly for the radical anion, rather than the close-lying (2)A(2) state, therefore giving a reasonable prediction of the geometry and spectra. Second, using [Cu(phen(.-))(PH3)(2)] it is possible to model the radical anion at the B3LYP/6-31G(d) level because the metal center stabilizes the b(1) singly occupied ligand MO. The calculated spectra of [Cu(phen(.-))(PH3)(2)] and its perdeuterated analogue compare favorably with experimental data for the excited state of the complexes.