Substituent group tuned tri- and binuclear porphyrin-based cyanide-bridged bimetallic complexes: synthesis, crystal structures and magnetic properties

Abstract

A series of six cyanide-bridged heterobimetallic complexes including {[M(L)₂]₂[Mn(TPP)]}[Mn(TPP)(MeOH)₂]·xH₂O·yMeOH {L = 1,2-bis(pyridine-2-carboxamido)-4-methylbenzenate (bpb²⁻), M = Cr (1), Co (2); L = 1,2-bis(pyridine-2-carboxamido)benzenate (bpmb²⁻), M = Cr (3), Co (4); TPP = meso-tetra(phenyl)porphyrin} and {[M(bpb)(CN)₂][Mn(TClPP)(MeOH)]}·xH₂O·yMeOH {M = Cr (5), Co (6), TClPP = meso-tetra(4-chlorophenyl)porphyrin} were designed and synthesized with two manganese(III)–porphyrin compounds and four pyridinecarboxamide dicyanidemetalates as building blocks. X-ray diffraction analysis reveals that compounds 1–4 containing the [Mn(TPP)]⁺ ion connect two dicyanide-containing [M(L)(CN)₂]⁻ anions to form the anionic trinuclear sandwich-like M^III–Mn^III–M^III molecular moiety with the one [Mn(TPP)(CH₃OH)₂]⁺ segment as a balance cation. The M^III–Mn^III complexes 5 and 6 show a dinuclear molecular conformation comprised of [M(bpb)(CN)₂]⁻ and [Mn(TClPP)(MeOH)]⁺ ions bridged by one cyanide group linking the Mn^III ion. Investigation of magnetic properties of the cyanide-bridged Cr–Mn complexes reveals the weak antiferromagnetic interaction between Mn^III and Cr^III magnetic centers with J_MnCr = −0.116(2), −0.092(2) and −0.86(2) cm⁻¹ for 1, 3, and 5, respectively.