EXCITED-STATE DISTORTIONS IN DROTRIS(3,5-DIMETHYL-1-PYRAZOLYL)BORATO]COPPER(II) DETERMINED FROM RESONANCE RAMAN INTENSITIES AND A NORMAL-COORDINATE ANALYSIS

Resonance Raman spectra, a normal coordinate analysis, and calculation of excited-state bond lengths and angles of drotris(3,5-dimethyl-1-py razolyl)borato]copper(II) are reported. Raman spectra are obtained in resonance with a ligand field state and the lowest ligand-to-metal cha rge transfer (LMCT) excited state. A normal coordinate analysis is car ried out using Raman and IR frequencies and resonance Raman intensitie s to assist in the assignment of the symmetric modes. Potential energy distributions (FED) and force constants are reported. The individual bend length changes are calculated by using the resonance Raman intens ities and the FED. Bond length and angle changes throughout the entire three-dimensional skeleton are reported. The signs of the bond length changes in the pyrazolyl berate ring are interpreted in conjunction w ith the results of a molecular orbital calculation. The N-N bond lengt h decreases by 0.02 Angstrom, the C=N bond lengths increase by 0.05 an d 0.08 Angstrom, the Cu-N bond increases by 0.10 Angstrom and the N-B- N angle decreases by 2 degrees in the LMCT excited state.