Chiral Photomagnets Based on Copper(II) complexes of 1,2-Diaminocyclohexane and Octacyanidomolybdate(IV) Ions.

Abstract

Chiral photomagnets compose a class of multifunctional molecule-based materials with light-induced alteration of magnetization and chiral properties. The rational design and synthesis of such assemblies is a challenge, and only few such systems are known. Herein, the remarkable octacyanide-bridged enantiomeric pair of 1-D chains [Cu((R,R)-chxn)2]2[Mo(CN)8]·H2O (1R) and [Cu((S,S)-chxn)2]2[Mo(CN)8]·H2O (1S) exhibiting enantiopure structural helicity, which results in optical activity in the 350-800 nm range as confirmed by natural circular dichroism (NCD) spectra, is reported. The photomagnetic effects of 1R, 1S, and 1rac result from the blue light excitation (436 nm) of the photomagnetically active octacyanidomolybdate(IV) ions. In the excited state MoIVHS centers with S = 1 couple antiferromagnetically with the neighboring CuII centers with JCuMo values of -1.3, -1.0, and -1.1 cm-1 for 1R, 1S, and 1rac, respectively. The values of thermal relaxation energy barriers have been estimated as 142 and 356 K for 1R and 1S, being comparable with the energy range of the thermal bath. The value for 1rac reveals a significantly lower value of 75 K. On the basis of these results the value of gMoHS has been estimated to be in the range 4.8-5.8.