Synthesis, crystal structure and magnetic properties of the new Cu(II)/Mn(II) coordination polymer [{Cu(cyclam)MnCl3(H2O)2}Cl]n

Abstract The synthesis, characterization and crystal structures of the copper complex [Cu( cyclam )Cl 2 ]·H 2 O ( 1 ) and bimetallic compound [{Cu( cyclam )MnCl 3 (H 2 O) 2 }Cl] n ( 2 ), where cyclam  = 1,4,8,11-tetraazacyclotetradecane, are reported. The crystal structure of 1 consists of complexes where Cu(II) is hexacoordinated and has elongated tetragonal-bipyramidal coordination, axial positions are occupied by the oxygen atoms from coordinated water molecules and the basal ones by the nitrogen atoms from the macrocyclic ligand. The reaction of 1 with manganese(II) chloride gives compound 2 with an ionic structure consisting of polymeric cation where Mn(II) and Cu(II) ions are bridged by chlorido ligands. Both central atoms are hexacoordinated and have distorted octahedral coordination environment. In the crystal structure, the formation of two types of chains is observed, one of them contains Cu(II) and Mn(II) ions arranged in alternating manner and perpendicular to them another type of chains consisting of chlorido-bridged Mn(II) atoms is formed. The magnetic properties are characterized by the dominant antiferromagnetic interaction forming Mn(II) chains along c -axis with J Mn /k B  = −3.38 K. A long-range magnetic order is formed at 4.23 K in zero magnetic field through the interaction with the Cu(II) subsystem. The analysis of the Arrott plots and critical exponent n describing the field dependence of the entropy change during adiabatic magnetization of the system revealed that the application of a weak magnetic field changes the order of the phase transition from second to the first order.