6533b7d1fe1ef96bd125d867

RESEARCH PRODUCT

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

subject

description

Two new Cu(II) coordination polymeric neutral chains of formula [Cu 2 (1,4-tpbd)(μ-A) 2 (H 2 O) 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 [Cu 2 (μ-tpbd)] 4+ dinuclear units (with Cu⋯Cu distances of 8.2233(3) for 1 and 8.2454(7) A for 2 ) connected through double cyanocarbanion bridges (Cu(NCCCN) 2 Cu with Cu⋯Cu distances of 7.4226(6) A for 1 and 7.4605(3) A 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 .