Chiral cyanido-bridged Mn–Nb magnets including halogen-bonds

Abstract

Three-dimensional cyanido-bridged bimetallic assemblies [Mn^II(4-Xpy)₄]₂[Nb^IV(CN)₈]·nH₂O (4-Xpy: 4-halopyridine; X = I and n = 0, (1); X = Cl and n = 0.5, (2)) are synthesized. 1 and 2 have chiral and achiral structures, respectively. The chiral structure of 1 is composed of achiral building blocks, which lead to an enantiopure compound through a spontaneous resolution process. In the crystal structure of 1, the halogen bonds between 4-Ipy and cyanide distort the structure, lowering the crystal symmetry. Both 1 and 2 show ferrimagnetism with Curie temperatures (T_C) of 22 K and 28 K, respectively. Due to the chiral and polar structure in the I4₁ space group, 1 exhibits SHG phenomena, while such nonlinear optical phenomena are quenched in 2 due to its centrosymmetry.