Synthesis, Crystal Structure, Thermal Behavior, and Magnetic Properties of a Tetranuclear Mn(II) Complex Bridged by End-to-End Dicyanamide

Abstract

A new tetranuclear compound [Mn4(o-vanilin)6(N(CN)2)2(MeOH)2] (1) has been synthesized under reflux and structurally characterized by elemental analysis, IR, conductance measurement, variable temperature magnetic measurement and single crystal. The complex (1) crystallizes in the triclinic space group P-1 with unit cell dimensions a = 9.1014 (4) Å, b = 11.1169 (4) Å, c = 14.8923 (4) Å, \(\alpha\) = 93.698 (3)°, \(\beta\) = 96.960 (3)°, \(\gamma\) = 107.165 (3)°, V = 1421.07 (9) Å3, Z = 1, R1 = 0.0345 and wR2 = 0.0798. The compound consist of two units [Mn2(o-Vanilin)3(MeOH)] with double \(\mu\)1,5-\(\eta\)1,-\(\eta\)1- dicyanamide (\(\mu\)1,5-\(\eta\)1,-\(\eta\)1- DCA) bridges between neighboring manganese(II) atoms. Two Mn(II) are situated in an O4N inner, while the two others Mn(II) are encapsulated by an O5N inner. The two pentacoordinated Mn(II) ions are situated in square pyramidal environment, while the hexacoordinated Mn(II) ions environment is best described as octahedral geometry. Thermogravimetric analyze of the complex were carried out at 20–800 °C and showed that the complex were decomposed into three steps. Variable-temperature (5-300 K) magnetic susceptibility data reveal the existence of weak antiferromagnetic interaction in complex 1. The magnetic behavior is explained by considering the exchange coupled manganese-radical system, which is subjected to the MnII-O-MnII intradimer interactions. The least-squares fitting of the data results J = -0.8. Negligible interdimer exchange via Mn-DCA-Mn (Mn∙∙∙Mn of 8.4530(5) Å) was observed.