Polypyridyl-based Cu(II) coordination polymers: Synthesis, structural and magnetic characterizations

Abstract New Cu(II) coordination polymeric neutral chains of formula [Cu 2 (1,4-tpbd)Cl 2 L 2 ] (1,4-tpbd =  N,N,N ′ N ′-tetrakis(2-pyridylmethyl)benzene-1,4-diamine, L = 1,1,3,3-tetracyano-2-ethoxypropenide (tcnoet) − ( 1) or 1,1,3,3-tetracyano-2-propoxypropenide (tcnopr) − ( 2 )) have been synthesized and characterized by infrared spectroscopy, X-ray diffraction and magnetic measurements. The crystal structure determinations of 1 and 2 reveal in both cases a one-dimensional structure in which the 1,4-tpbd acts as a bis-chelating ligand and the two chloride anions as asymmetrical bridging ligands. The Cu⋯Cu distances through the bis-chelating 1,4-tpbd ligand (8.194(1) and 8.245(3) A for 1 and 2 respectively) are in the range of the corresponding distances observed for parent complexes involving similar bridges; and as expected, the Cu⋯Cu distances through the asymmetrical (μ 2 -Cl) 2 bridges are significantly shorter (4.021(2) and 4.125(2) A for 1 and 2 , respectively). For both compounds, magnetic measurements exhibit a maximum in the χ m versus T plot (at 50 K for 1 , and at 48 K for 2 ), characteristic of antiferromagnetic exchange interactions occurring mainly through the tbpd organic ligand that can be very well reproduced with a S  = ½ dimer model with g  = 2.114, J  = −41.2 cm −1 for 1 and g  = 2.105 and J  = −39.3 cm −1 for 2 .