Ab initio calculations, Natural Bond Orbital (NBO) and Atoms-in-Molecules (AIM) analyses, and Fourier transform Raman (3200e350 cm
1) and infrared (4000e200 cm
1) spectral measurements have been made for bis(a-cyanoacetylacetonato)Cu(II), Cu(CNacac)2. The molecular structure and vibrational spectra of Cu(CNacac)2 is compared with those of bis(acetylacetonato)Cu(II), Cu(acac)2. The molecular electronic energies and the equilibrium geometries for all theoretically possible conformations are calculated. A normal coordinate analysis of the vibrational modes has been computed for the most stable conformation of Cu(CNacac)2, D2h symmetry. A complete assignment of the observed band frequencies has been proposed. The metaleO bond strength was investigated by geometry calculations, NBO, AIM, and spectroscopic results to realize the effect of cyano substitution at a-position. All theoretical and vibrational spectroscopic studies confirm stronger metaleligand bond in Cu(CNacac)2 than that in Cu(acac)2.

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