The molecular structure, bonding, and energetics of oxovanadium phthalocyanine: an experimental and computational study

A mass spectrometric study of saturated vapor over oxovanadium phthalocyanine showed the thermal stability and monomeric vapor composition of this compound. The molecular structure of oxovanadium phthalocyanine (VOPc) was determined using a combination of gas-phase electron diffraction (GED), mass spectrometry, and quantum chemical calculations. According to GED, the VOPc molecule has C_4v symmetry. Experimental structural parameters are in good agreement with the parameters obtained by UB3LYP/cc-pVTZ calculations. The vanadium atom has a five-coordinated square-pyramidal geometry, being shifted above the plane of the four isoindole nitrogen atoms by 0.576(14) Å. The parameters of the square pyramid VN₄ are r _h1(V–N) = 2.048(7) Å, r _h1(N···N) = 2.780(12) Å. The vanadium–oxygen bond length is r _h1(V–O) = 1.584(11) Å. NBO analysis shows polar character of coordination bonds with significant covalent contribution and pronounced direct donation. X-ray crystallography and GED give different coordination bond lengths according to the different physical meaning of the parameters obtained by these methods. The enthalpy of sublimation [?H _s ^o (593–678 K)] is 53.3 ± 0.8 kcal/mol.