Coordination polymers based on bridging cyanocarbanions and bis-tridentate p-phenylenediamine ligands

International audienceTwo new Cu(II) coordination polymeric neutral chains of formula [Cu2(1,4-tpbd)(μ-A)2(H2O)2](A)2 with A = tcnoet− (1) and tcnopr− (2) (1,4-tpbd = N,N,N′N′-tetrakis(2-pyridylmethyl)benzene-1,4-diamine, tcnoet− = 1,1,3,3-tetracyano-2-ethoxypropenide and tcnopr− = 1,1,3,3-tetracyano-2-propoxypropenide) have been synthesized and characterized by infrared spectroscopy, X-ray diffraction and magnetic measurements. 1 and 2 show alternating chains where the 1,4-tpbd and the cyanocarbanion units (tcnoet− for 1 and tcnopr− for 2) alternate as bridging ligands. The molecular structure can be viewed as [Cu2(μ-tpbd)]4+ dinuclear units (with Cu⋯Cu distances of 8.2233(3) for 1 and 8.2454(7) Å for 2) connected through double cyanocarbanion bridges (Cu(NCCCN)2Cu with Cu⋯Cu distances of 7.4226(6) Å for 1 and 7.4605(3) Å for 2) leading to alternating zig-zag chains running along the [0 1 0] direction. Both compounds exhibit a maximum in the thermal variation of the magnetic susceptibility (at ca. 30 K in both cases), characteristic of antiferromagnetic exchange interactions occurring mainly through the 1,4-tbpd organic ligand that can be very well reproduced with a S = ½ dimer model with g = 2.119, J = −35.0 cm−1 for 1 and g = 2.070 and J = −35.2 cm−1 for 2