Synthesis and characterization of heterobimetallic coordination polymers containing chiral nickel(II) macrocycle and silver(I) cyanide

Chiral coordination polymers [Ni(L^R,R)Ag(CN)₂ ](ClO₄)·CH₃CN (3) and [Ni(L^S,S)Ag(CN)₂](ClO₄)-CH₃CN (4) were prepared by the reaction of K[Ag(CN)₂] with [Ni(L^R,R)](ClO₄)₂ (1) and [Ni(L [Ni(L^S,S)](ClO₄)₂ (2), respectively (L^R,R/S,S = 1,8-di((R/S)-α-methylbenzyl)-1,3,6,8,10,13-hexaazacyclotetradecane). The polymers were characterized by elemental analysis, spectroscopy, magnetic measurement and single crystal X-ray diffraction. In 3, the nickel(II) macrocyclic complexes link two Ag(CN)^-₂ ions in axial position and each Ag(CN)^-₂ ion binds two adjacent nickel(II) ions to form a 1-D chain structure. The structure of 4 is nearly same to that of 3, except for chirality. 3 and 4 exhibit very weak antiferromagnetic couplings through the bridged Ag(CN)^-2₂ ions within the 1-D chains (g = 2.20 and J/k_B = -0.55 K for 3 and 4). The circular dichroism spectra of 3 and 4 show an enantiomeric pattern and have bisignate Cotton effects.