Copper(II) Clusters of Two Pairs of 2,3-Dihydroxybutanedioyl Dihydrazones: Synthesis, Structure, and Magnetic Properties

Condensation reactions of (2R,3R)- and (2S,3S)-2,3-dihydroxybutanedihydrazide with salicylaldehyde and 3-methoxysalicylaldehyde gave two enantiomeric pairs, (2R,3R)/(2S,3S)-2,3-dihydroxybutanedioylbis(salicylaldehydehydrazone) [(2R,3R)-BSH and (2S,3S)-BSH] and (2R,3R)/(2S,3S)-2,3-dihydroxybutanedioyl bis(3-methoxysalicylaldehydehydrazone) [(2R,3R)-MBSH and (2S,3S)-MBSH]. Their reactions with Cu-II salts provided two chiral hexanuclear clusters [Cu6L2(C5H5N)(10)](2)[C5H6N](3)(ClO4)(7)center dot(CH3OH)center dot(C5H5N) [L = (2R,3R)-BSH; (2S,3S)-BSH] and four chiral tridecanuclear clusters [Cu13L3(OH)(2)(CH3COO)(6)(C5H5N)(6)(DMF)(3)]center dot 6DMF center dot 3H(2)O [L = (2R,3R)-BSH; (2S,3S)-BSH] and [Cu13X3(OH)(2)-CH3COO)(6)(C5H5N)(2)(DMF)(8)]center dot 6H(2)O [X = (2R,3R)-MBSH, (2S,3S)-MBSH]. Their structures were determined by single-crystal X-ray diffraction analysis. All six compounds are enantiomers of each other. The two hexanuclear clusters exhibit two orthogonal linear trinuclear units. The two pairs of tridecanuclear clusters display esthetic structures with different symmetries; they feature rare heptanuclear vertexsharing dicubane cores and their six unshared Cu-II vertexes are linked to another six Cu-II ions. These represent the first examples of chiral clusters bearing dicubane cores. Magnetic studies revealed the presence of overall antiferromagnetic interactions in these compounds.