New heterobimetallic Cu(II)/Mn(II) complexes with trans-1,8-cyclam derivatives: Synthesis, characterization, magnetic properties and crystal structures of (µ2-Chloro)-(dpc)-copper(II)-trichloro-manganese(II) and two polymorphs of (µ2-Chloro)-(dac)-copper(II)-trichloro-manganese(II)

Abstract

Two derivatives of cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) with propyl- or allyl- (prop-2-en-1-yl) substituents on nitrogen atoms in trans positions, namely 1,8-dipropyl-1,4,8,11-tetraazacyclotetradecane (dpc) and 1,8-diallyl-1,4,8,11-tetraazacyclotetradecane (dac) were prepared and characterized by IR, 1H NMR and 13C NMR spectroscopy. Reaction of dpc and dac with copper(II) chloride gives compounds [Cu(dpc)(H2O)2]Cl2 (1) and [Cu(dac)(H2O)2]Cl2 (3) with similar crystal structures. Compounds 1 and 3 were used as precursors in the synthesis of Cu(II)/Mn(II) complexes 2, 4a and 4b. Prepared complexes were characterized by IR spectroscopy, elemental analysis and their crystal structures were determined using single crystal X-ray analysis. Compounds 4a and 4b are polymorphs, both crystallize in the monoclinic crystal system and the main difference in their crystal structures is in steric arrangement of metal centres within a chain. Moreover, measurements of magnetic susceptibility and Broken Symmetry DFT calculations (BS DFT calculations) carried out for bimetallic complexes 2 and 4a showed that a ferromagnetic exchange interaction J/kB = 2.28 K and J/kB = 2.34 K, respectively, exists within the dinuclear units.