Accurate molecular structure of nickel phthalocyanine (NiN8C32H16): Gas-phase electron diffraction and quantum-chemical calculations

Abstract The molecular structure of the nickel phthalocyanine (NiPc) was determined using the combination of gas-phase electron diffraction (GED), mass spectrometry and quantum chemical calculations. The DFT calculations with employing different functionals and basis sets found the molecular structure with D 4h symmetry that agrees satisfactorily to the one found in experiment at 776 ± 5 K. The important bond lengths and bond angles according to GED (total errors in parentheses) are: r h 1 (Ni–N) = 1.913(5) A, r h 1 (N–C p ) = 1.385(4) A, r h 1 (C p –N m ) = 1.327(5) A, r h 1 (C p –C p ) = 1.462(6) A, r h 1 (C p –C) = 1.399(3) A, r h 1 (C–C) = 1.395(3) A, ∠ NiNC p  = 126.6(2)°, ∠ NC p N m  = 128.4(4)°, ∠ C p N m C p  = 120.1(5)°, ∠ NC p C p  = 110.0(4)°, ∠ C p C p C = 121.2(1)°. The nickel–nitrogen bond distance obtained is by 0.04 A longer than the one found for this compound in the literature. The structures of the crystalline and gaseous NiPc complex are compared. The effect of the metal (Ni, Cu, Zn) on structural features of the MPc complexes is discussed. Using NBO-analysis, the correlation between the metal–ligand bond distance and the total energy of donor–acceptor orbital interactions per one M–N bond was found in the MPc complexes.