Structural and EPR studies of pyrophosphate-bridged dinuclear CuII complexes
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2014
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Two new pyrophosphate-bridged copperII complexes, [Cu(dpa)(H2O7P2)]2 1 and [Cu2(terpy)2(HO7P2)·(H2O4P)·(H3O4P)·(H2O)] 2 (dpa = 2,2′-dipyridylamine and terpy = 2,2′:6′,2″-terpyridine) were isolated and their crystal structures determined by single-crystal X-ray diffraction. The compounds are triclinic and contain dinuclear copperII units bridged by pyrophosphate anions. The EPR spectra observed in three planes of single crystal samples as a function of field orientation at 293 K for compounds 1 and 2, and also for two other pyrophosphate compounds already reported, [Cu(bipy)(cis-H2O7P2)]2·3(H2O) 3 and [Cu(bipy)(trans-H2P2O7)]2 4 display a single resonance for any field orientation and temperatures T between 4 and 293 K, as in mononuclear spin systems, without hyperfine structure, and their g-factors and line widths were measured. The relations between the principal directions of the g-matrices and the molecular structures are discussed and compared with related compounds. The temperature dependences of the intensity of the EPR signals observed for 1–4 above 4 K indicate a paramagnetic Curie behavior, with no indication of intradinuclear exchange interactions (so, |J| < 2 K). The absence of dinuclear splitting and of hyperfine structure of the dinuclear units is explained in terms of averaging out by the interdinuclear interactions, allowing to set a lower limit of their magnitudes.
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Copper, Pyrophosphates, Structure, Magnetic interactions, EPR
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SARTORIS, Rosana P.; CALVO, Rafael ; SANTANA, Ricardo C.; NASCIMENTO, Otaciro R.; PEREC, Mireille; BAGGIO, Ricardo F. Structural and EPR studies of pyrophosphate-bridged dinuclear CuII complexes. Polyhedron, Amsterdam, v. 79, p. 178-185, 2014. DOI: 10.1016/j.poly.2014.05.002. Disponível: https://www.sciencedirect.com/science/article/pii/S0277538714002988. Acesso em: 25 maio 2023.