Chiral Cyanide-Bridged Cr<sup>III</sup>–Mn<sup>III</sup> Heterobimetallic Chains Based on [(Tp)Cr(CN)<sub>3</sub>]<sup>−</sup>: Synthesis, Structures, and Magnetic Properties
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By the reactions of MnIII Schiff-base complexes with the tricyanometalate building block, [(Tp)Cr(CN)3]− (Tp = Tris(pyrazolyl) hydroborate), two couples of enantiomerically pure chiral cyano-bridged heterobimetallic one-dimensional (1D) chain complexes, [Mn((R,R)-Salcy)Cr(Tp)(CN)3·1/4H2O·1/2CH2Cl2]n (1) and [Mn((S,S)-Salcy)Cr(Tp)(CN)3·1/4H2O·1/2CH2Cl2]n (2) (Salcy = N,N′-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion), [Mn((R,R)-Salphen)Cr(Tp)(CN)3]n (3) and [Mn((S,S)-Salphen)Cr(Tp)(CN)3]n (4) (Salphen = N,N′-1,2-diphenylethylene-bis(salicylideneiminato) dianion), have been successfully synthesized. Circular dichroism (CD) spectra confirm the enantiomeric nature of the optically active complexes. Structural analyses reveal the formation of neutral cyano-bridged zigzag single chains in 1 and 2, and neutral cyano-bridged zigzag double chains in 3 and 4. Magnetic studies show that antiferromagnetic couplings are operative between CrIII and MnIII centers bridged by cyanide. Complexes 1 and 2 are the rare examples of chiral ferrimagnets; while complexes 3 and 4 exhibit a coexistence of chirality and spin-glass behavior in a 1D chain.
