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NTIS 바로가기Transition metal chemistry, v.24 no.2, 1999년, pp.224 - 232
Ward, Matthew S. (Department of Chemistry, University of Pittsburgh, Pittsburgh. PA 15260, USA) , Borisenko, Grigory (Department of Chemistry, University of Pittsburgh, Pittsburgh. PA 15260, USA) , Shepherd, Rex E. (Department of Chemistry, University of Pittsburgh, Pittsburgh. PA 15260, USA)
ZnII and CuII complexes of the ligand edampda2− [N,N′-bis(pyridylmethyl)-ethylenediamine-N,N′-diacetate] have been studied in solution by 1H n.m.r. and e.p.r. spectroscopies, respectively. [ZnII(edampda)] exists in solution in a major octahedral isomer (ca. 83%) in which the two carboxylate donors and two pyridylmethyl donors remain stereochemically rigid up to 333K at pD=6.0. The major octahedral complex has equivalent glycinato and pyridyl donors as shown by equivalent AB quartets for each type of chelate. By contrast, the [ZnII(edta)]2− analogue complex is known to have processes which rapidly equilibrate the coordinated carboxylates leading to coalesced, broad singlets instead of AB quartets down to 273K (freezing point of the sample). The minor [ZnII(edampda)] species has one pendant pyridylmethyl arm. The complex does not increase in abundance up to 333K via dissociation of the major species, suggesting that it possesses a different five-coordinate geometry (approximate trigonal bipyramid). The [CuII(edampda)] complex exhibits an e.p.r. spectrum that is intermediate between rhombic or tetragonal CuII complexes (near D4h) and the “reversed-e.p.r.” type of trigonal bipyramidal CuII complexes (ca. D3h). The single g value of 2.079 for g∥≅g⊥>2.03 identifies the [CuII(edampda)] complex as distorted toward trigonal bipyramidal whereas its [CuII(edtaH2)(H2O)] analogue is known to be distorted toward square pyramidal. A binuclear CuI complex of edampda2− is formed only as a transient, and it rapidly disproportionates into [CuII(edampda)] and Cu metal. A mononuclear [CuI(edampda)]− complex persists for up to 8 h, but is oxidized within 3 min by O2 to the CuII complex. [CuII(edampda)] oxidizes to CuIII with a highly irreversible wave on glassy-carbon at +1.09V compared to the [NiII/III(edampda)] wave at +1.32V.
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