Ferromagnetic and antiferromagnetic polymeric complexes with the macrocyclic ligand 1,4,7-triazacyclononane

Three novel copper polymers, {[Cu-4(tacn)(4)(o-bda)(2)]- (ClO4)(4)(H2O)(2)}(n) (1), {[Cu(tacn)(m-bda)](CH3OH)(0,5)(H2O)(0.5)}(n) (2), and {[Cu-2(tacn)(2)(p-bda)](ClO4)(2)}(n) (3) (tacn = 1,4,7-triazacyclononane, bda = benzenedicarboxylic acid) have been synthesized and structurally characterized. Compound 1 belongs to the monoclinic space group C2, while 2 and 3 crystallize in the orthorhombic space group Pmc2(l) and the monoclinic space group P2(1)/n, respectively. They are all 1D zigzag polymers, which can be considered as Cu(tacn)21 building units linked by isomers of benzenedicarboxylic acid. The variable-temperature (2-300 K) magnetic behavior revealed the existence of ferromagnetic interactions in 1 and 2. The best fittings of the experimental magnetic susceptibilities gave J = 4.0 cm(-1) and g = 2.04 for 1, J = 1.2 cm(-1), zJ' = -0.18 cm(-1) and g = 2.07 for 2, whereas the exchange coupling between Cu-II ions in 3 is antiferromagnetic with J = -13.1 cm(-1) and g = 2.05. The transformation of interactions between copper ions from ferromagnetic to antiferromagnetic is closely related to the variations in the isomeric benzenedicarboxylic acids. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.