Synthesis, structure and polarized optical spectroscopy of two new fluoromanganese(III) complexes†

Abstract

The syntheses and crystal structures of two new fluoromanganese(III) complexes are reported; [MnF₃(H₂O)(2,2′-bipy)] 1 and 4,4′-bipyH₂[MnF₄(H₂O)₂]·2H₂O 2, where 2,2′-bipy and 4,4′-bipy are 2,2′-bipyridyl and 4,4′-bipyridyl, respectively. Compound 1: monoclinic, space group P2₁/n, a = 1973.7(4), b = 749.0(2), c = 903.1(3) pm, β = 95.22(3)°, Z = 4, R1 = 0.051. Compound 2: monoclinic, space group P2₁, a = 516.4(2), b = 1851.9(4), c = 986.3(3) pm, β = 99.07(2)°, Z = 2, R1 = 0.028. The manganese co-ordination environment was found to be octahedral in both compounds, but strongly distorted by the Jahn–Teller effect as a result of the high-spin d⁴ configuration of Mn³⁺. A very extensive intermolecular hydrogen-bond framework is present in both compounds. For compound 1 the octahedra are linked through hydrogen bridges resulting in octahedral manganese chains. For compound 2, the octahedra [MnF₄(H₂O)₂]^– are associated via hydrogen bonds into chains, which in turn are connected by interchain hydrogen bridges. The polarized optical spectra of single crystals are presented and explained in terms of intraconfigurational d⁴ transitions split by ligand fields of nearly C_s and D_4h symmetries for compounds 1 and 2, respectively. The results are compared with those available for other Mn^III fluorides.