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Keywords:

  • Coordination polymers;
  • Copper;
  • Chiral ligands;
  • Magnetic properties

Abstract

Reaction of CuCl2·2H2O with chiral Schiff bases and sodium dicyanamide led to the formation of two chiral copper(II) coordination polymers, namely [Cu4(L1)2(dca)4]n (1) and [Cu2(L2)(μ-Cl)(dca)(H2O)]n·nH2O (2) {H2L1 = (1R, 3S)-N′,N′′-bis[salicylidene]-1,3-diamino- 1,2,2-trimethylcyclopentane, H2L2 = (1R, 3S)-N′,N′′-bis[3-ethoxysalicylidene]-1,3-diamino- 1,2,2-trimethylcyclopentane, dca = dicyanamide}. Both complexes were structurally characterized by elemental analyses, IR spectroscopy and single-crystal X-ray diffraction. Complex 1 exhibits a two-dimensional polymeric structure formed by single dca bridging tetranuclear Cu4 units. Complex 2 displays a left-handed helical chain structure constructed from Cu2 dimers with single dca bridges. The chirality of 1 and 2 was confirmed by circular dichroism (CD) measurements in solution. Both complexes exhibit strong antiferromagnetic couplings with J = –308(4) cm–1 for 1 and J = –123(1) cm–1 for 2 in 2–300 K.