Calculated and experimental geometries and infrared spectra of metal tris-acetylacetonates: vibrational spectroscopy as a probe of molecular structure for ionic complexes. Part II

Following on from our previous work on Sc, Fe, Cr, and Al (Part 1; see J. Phys. Chem. A, 105 (2001) 238), the geometries and infrared spectra of the trivalent metal tris-acetylacetonate complexes (M[O2C5H7](3); M = Ti, V, Mn, Co) have been studied both experimentally and theoretically using nonlocal hybrid density functional theory with a split-valence plus polarization basis for the ligand and valence triple-xi for the metal. Unlike the D-3 complexes studied in Part 1, those of Ti, V and Mn are candidates for Jahn-Teller distortion due to fractional d-shell occupancy. Using scale factors transferred from Part 1, our calculated frequencies are in very good agreement with experimentally observed fundamentals. Our investigation shows that the V and Mn complexes distort to C-2 ground states, but D3 Ti trisacetylacetonate is stable. Further investigation of the weak band observed around 800 cm(-1) in the Fe complex (and present in almost all studied first-row transition metal tris-acetylacetonates), which we were unable to assign theoretically in Part 1, supports the argument that this band is not a fundamental but is due to Fermi resonance. (C) 2002 Elsevier Science B.V. All rights reserved.