Journal
ACS OMEGA
Volume 4, Issue 17, Pages 17160-17170Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsomega.9b01575
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Funding
- JSPS Core-to-Core Program, A. Advanced Research Networks, CResCent (Chirality Research Center) in Hiroshima University (MEXT program for promoting the enhancement of research universities, Japan) [25220803]
- Ministry of Science and Education of the Russian Federation
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Reaction of Cu(hfac)(2) with methyl- and bromo-3-pyridyl-substituted nitronyl nitroxides (L-R) leads to assemble a diverse set of coordination complexes: mononuclear [Cu(hfac)(2)L2-Me], binuclear [{Cu(hfac)(2)}(2)(H2O)L2-Me], trinuclear [{Cu(hfac)(2)}(3)(L6-Br)(2)], pentanuclear [{Cu(hfac)(2)}(5)(L2-Me)(2)], and [{Cu(hfac)(2)}(5)(L2-Me)(4)], cocrystals [Cu(hfac)(2)(L2-Br)(2)]center dot[Cu(hfac)(2)(H2O)(2)] and [Cu(hfac)(2)(L2-Br)(2)]center dot 2[Cu(hfac)(2)H2O], one-dimensional polymers [Cu(hfac)(2)L2-Br](n) and [Cu(hfac)(2)L6-Br](n), and cyclic dimers [Cu(hfac)(2)L5-Me](2), [Cu(hfac)(2)L5-Br](2), and [Cu(hfac)(2)L6-Me](2). The molecular structures of the obtained complexes are strongly affected by the substituent type and its location in the pyridine heterocycle. Occupation of the second position of the pyridine ring increases the steric hindrance of both imine and nitroxide coordination sites of L2-R, which is favorable for the formation of various conformers and precipitation of complexes with different molecular structures. The pentanuclear [{Cu(hfac)(2)}(5)(L2-Me)(2)] and [{Cu(hfac)(2)}(5)(L2-Me)(4)] complexes do not have prior analogues and are valuable model objects for investigation of the mechanism of formation of various coordination polymers. The arrangement of long Cu-ONO bonds in {CuO6} square bipyramids due to the weakening nitroxide donor site in complexes, based on L2-Me, L2-Br, and L6-Br ligands, results in ferromagnetic exchange interactions between spins of Cu2+ ions and nitroxides. Complexes with substituents that do not considerably affect the coordination ability of ligands (L5-Me, L5-Br, and L6-Me) exhibit strong antiferromagnetic exchange interactions between spins of Cu2+ ions and nitroxides.
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