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 Cs and D4h symmetries for compounds 1 and 2, respectively. The results are compared with those available for other MnIII fluorides.