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

International audienceNew 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) Å 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 ( 2-Cl) 2 bridges are significantly shorter (4.021(2) and 4.125(2) Å for 1 and 2, respectively). For both compounds, magnetic measurements exhibit a maximum in the m vs. 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.