Three molecular metals containing bis(maleonitriledithiolate)nickel(III) anion and 2-substituted benzyl triphenylphosphonium: Syntheses, crystal structures and magnetic properties

Abstract

Three new molecular metals, [2RBzTPP][Ni(mnt)2] (mnt2−=maleonitriledithiolate; [2RBzTPP]+=1-(2′-R-benzyl)triphenylphosphonium, R=F(1), Br(2), NO2(3)) have been synthesized and characterized by elemental analyses, IR, UV, single crystal X-ray diffraction and magnetic measurements. The single-crystal structure analysis indicates that 1 crystallizes in the triclinic space group P−1, while both 2 and 3 crystallizes in the monoclinic space group P21/n. The Ni(III) ions of 1, 2, and 3 form a 1D non-uniform magnetic chain within a [Ni(mnt)2]− anions column through Ni⋯Ni, Ni⋯S or S⋯S interactions. The effect of weak intramolecular interactions such as CH⋯N, CH⋯F, CH⋯Br, CH⋯π or CH⋯O hydrogen bonds in these molecular solids 1, 2 or 3 generate a 3D network structure. Magnetic measurements have shown that 1 exhibits a characteristic of spin-gap (Δ/kb=249.5K) around 128K, while 2 and 3 showed a very strong antiferromagnetic coupling feature with J=−875.6 and −820.3cm−1 when the temperature is lowered.