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Ladder-like [CrCu] coordination polymers containing unique bridging modes of [Cr(C2O4)3]3− and Cr2O72−

Three heterometallic one-dimensional (1D) coordination polymers {; ; ; A[CrCu2(bpy)2(C2O4)4]·H2O}; ; ; n [A = K+ (1) and NH4+ (2) ; bpy = 2, 2’-bipyridine] and [(Cr2O7)Cu2(C2O4)(phen)2]n (3 ; phen = 1, 10- phenanthroline) with uncommon topology have been synthesized using a building block approach and characterized by single-crystal X- ray diffraction, IR and impedance spectroscopies, magnetization measurements, and DFT calculations. Due to the partial decomposition of the building block [Cr(C2O4)3]3−, all three compounds contain oxalate-bridged [Cu2(L)2(μ-C2O4)]2+ units [L = bpy (1 and 2) and phen (3)]. In compounds 1 and 2 these cations are mutually connected through oxalate groups from [Cr(C2O4)3]3−, thus forming ladderlike topologies. Unusually, three different bridging modes of the oxalate ligand are observed in these chains. In compound 3 copper(II) ions from cationic units are bridged through the oxygen atoms of Cr2O72− anions in a novel ladder-like mode. Very strong antiferromagnetic coupling observed in all three compounds, determined from the magnetization measurements and confirmed by DFT calculations (J = −343, −371 and −340 cm−1 for 1, 2 and 3, respectively), appears between two copper(II) ions interacting through the oxalate bridge.

coordination polymers ; bridging oxalate ; bridging dichromate ; ladder-like topology ; antiferromagnetic interaction

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