Tetra(n-butyl)ammonium Dicyanotetraphenyl-porphyrinatomanganate(III); Crystal Structure and Electronic Resonance Raman and Absorption Spectra

Abstract

The title complex salt has been isolated from a solution of chlorotetraphenylporphyrinatomanganese(III) and tetra(n-butyl)ammonium cyanide in dichloromethane. The complex salt crystallizes as a hydrate-dichloromethane solvate in the orthorhombic space group Pbca (no. 61) with cell parameters as follows: a = 21.491(5) Å, b = 21.706(5) Å, c = 28.489(5) Å, V = 13 290(5) Å3, Z = 8. The structure is that expected for a hexa-coordinated low-spin Mn ( III ) tetraphenylporphyrinate (magnetic moment: μ eff = 3.1 ± 0.2 μ B at 273 K). The Mn atom is in the centre of the slightly ruffled porphyrinato core. The Mn - C CN distance of 2.01(2)/2.02(2) Å and the Mn - N p distance, varying between 1.972(13) and 2.016(14) Å, are normal values. The Mn - C CN - N group is bent (171(2)/174(2) °). At low temperatures, a molecular electronic resonance Raman effect is detected at 198 and 344 cm−1. It is attributed to intraconfigurational transitions Γ 1g → Γ 4g and Γ 1g → Γ 3g Γ 5g , respectively, arising from the spin-orbit split 3 T 1g ground state of low-spin Mn ( III ), assuming pseudo-octahedral symmetry. Weak Q and intense B (Soret) transitions at 17 300 and 23 200 cm−1, respectively, as well as four weak trip–multiplet transitions are observed at 8650, 12 000, 14 900 and 19 900 cm−1.