Mixed ligand copper(II) coordination polymers constructed by Cu-bpm-Cu dimer unit (bpm = 2,2′-bipyrimidine) as a building block.: Crystal structures and magnetic properties of {[Cu(bpm)(SO4)]( H2O)}n, [Cu2(bpm)(suc)0.5(ClO4)2(OH)(H2O)2]n and {[Cu(bpm)1.5(suc)0.5](ClO4)(H2O)2}n (suc = succinate)

New 2,2'-bipyrimidine (bpm)-based copper(II) coordination polymers have been synthesized and characterized. The structure of {[Cu(bpm) (SO4)] (H2O)}(n) (1) contains zigzag chains which are constructed of Cu-bpm-Cu units, sulfate ions and additional bridging bpms. Sulfate ions coordinate to copper(II) ions, and link the chains to form a three-dimensional bundle structure. The crystal structure of [Cu,(bpm) (suc)(0.5)(ClO4)(2)(OH) (H2O)(2)](n) (2) consists of a chain of bpm-bridged dinuclear copper(II) units linked by a carboxylate group from the succinate anion and a hydroxo group. Coordinated perchlorate ions also bridge the adjacent chains. The chain structure of {[Cu(bpm)(1.5)(suc)(0.5)] (ClO4) (H2O)(2)}(n) (3) consists of the bpm-bridged dinuclear copper(II) units, amphimonodentate succinate dianions and terminal bpms. The succinate dianion acts as a bridging ligand between the dimers to yield a one-dimensional zigzag chain in the crystal. The terminal bpm stacks with a nearest-neighbor terminal bpm on an adjacent chain to form a linkage for a two-dimensional sheet. The present work affords a new strategy to build multi-dimensional coordination polymers, which is based on the use of [Cu-bpm-Cu](4+) copper(II) dinuclear units as 'building blocks'. The geometries around the pyrimidyl rings of bpm are similar to each other, whereas the geometry of the copper atoms is different. The additional linking ligand as a peripheral ligand coordinates to the dimer unit to control the plasticity of the coordination sphere of copper(II); this makes the modification of the symmetry of its magnetic orbital easy. The magnetic susceptibilities were measured from 2 to 300 K and analyzed as antiferromagnetic Heisenberg S = 1/2 alternating chains to yield J= -38.8 cm(-1), alpha = 0.93 (1), J= -132.2 cm(-1), alpha = 0.22 (2) and J= -4.5 cm(-1), alpha = 0.60 (3). (C) 1998 Elsevier Science S.A. All rights reserved.