Syntheses and Characterizations of Copper(II) Polymeric Complexes Constructed from 1,2,4,5-Benzenetetracarboxylic Acid

Four polymeric complexes with rectangular grids or channels, [Cu2(btec)(H2O)4·2H2O]n (2), [Cu2(btec)4/4{Cu(Hbtec)2/2(4,4‘-Hbpy)(H2O)2}2·4H2O]n (3), [Cu2(btec)(hmt)(H2O)4·8H2O]n (4), and [Cu3(btec)(OH)2]n (5), were designed and
constructed from Cu(II) ion and 1,2,4,5-benzenetetracarboxylic acid along with auxiliary ligands (where H4btec =
1,2,4,5-benzenetetracarboxylic acid, 4,4‘-Hbpy = monoprotonated 4,4‘-bipyridine, and hmt = hexamethylenetetramine). Complexes 2, 3, and 4 have rectangular pores with the size of 6.5 Å × 4.5 Å, 6 Å × 7 Å, and 10.1 Å ×
11.8 Å, respectively, while 5 has a channel of 7.4 Å × 9.6 Å. The complexes show interesting magnetic properties
due to the different coordination modes of the carboxylate groups and the presence of auxiliary ligands. On lowering
the temperature, the magnetic interactions in 2 are changed from antiferromagnetic to ferromagnetic. For 3, the
antiferromagnetic interactions weaken sharply at low temperature. Complex 4 shows ferromagnetic interactions
while 5 is antiferromagnetic.