Molecular structure of cobalt(II) etioporphyrin-II determined by combined gas-phase electron diffraction/mass-spectrometry and quantum chemical calculations: Searching a ruffling and saddling effects

Abstract

The structure of a free cobalt (II) etioporphyrin-II (CoEP-II) molecule was investigated for the first time by combined gas-phase electron diffraction and mass spectrometry (GED/MS) method. Selected experimental parameters are as follows: rh1(Co-N) = 1.976(5) Å, rh1(N-Cα) = 1.383(4) Å, rh1(Cα-Cβ) = 1.455(4) Å, rh1(Cα-Cm) = 1.388(3) Å, rh1(Cβ-Cβ) = 1.371(3) Å. Despite the significant shortening of the internuclear distance between metal and nitrogen atoms compared to CuEP-II and ZnEP-II, the macrocycle of CoEP-II was determined to be quasiplanar. The ground state of CoEP-II is of the low spin and possesses 2A symmetry. These results correlate with the structural features of cobalt (II) porphyrin (CoP) molecule which is planar in the ground state (2A1g).