Cobalt(II) Polypyridine Complexes and Their Reversible Reactivity with Dioxygen

The Coordination Chemistry of the Pentadentate 2,2,6,6‐Tetrakis(aminomethyl)‐4‐azaheptane (ditame)

“…In agreement with our findings, dinuclear, monobridged Co III (pentaamine)(superoxo) complexes reported to date are centrosymmetric [7,15,40Ϫ42] or nearly centrosymmetric [43] (τ ϭ 175°). For (pentaamine)Co III (peroxo) complexes, both planar transoid [6,23,34,35,37,38] and bent [8,9,15,36,39] structures have been described, examples with τ ϭ 180°predominat-ing. The known non-centrosymmetric, bent structures have torsional angles τ of 146Ϫ177.5°.…”

“…The pH dependence was interpreted in terms of a deprotonation of the coordinated water ligand. (Figure 11), [24] [7,15,35,48,64] In aqueous solutions of [Ni(ditame)] 2ϩ (0.1  KNO 3 ), cyclic voltammetry indicated formation of an Ni III species. A quasi-reversible one-electron transfer was observed, with E 1/2 obs ϭ 0.95 V vs. NHE (∆E P ϭ 79 mV, v ϭ 5 mV/s, Au electrode).…”

Characterization of dioxygenated cobalt(II)–carnosine complexes by Raman and IR spectroscopy

“…In fact, the Raman spectra of several -superoxo-bicobalt complexes with principally amine donor ligands in other coordination sites exhibit a similar band in the 1075 Ϯ 5 cm Ϫ1 spectral region. 21,23,31 Although some Raman bands were identified as markers of the oxygenated state and the geometry of the OOO bond, the IR spectra did not reveal any bands attributable to OOO vibrations (Fig. 4 and Table III), presumably because the molecular symmetry is such that dipole changes, due to the stretching motions, are small.…”

“…20 A similar band at Ϸ810 cm Ϫ1 was also observed in the Co(II)-histidine aqueous solutions when a peroxo-bridged complex was formed 15 and upon the dioxygenation reaction of Co(II) polypyridine complex solutions. 21 ESR studies suggested that the oxygenation reaction of the Co(II)-Carnos complex involves dimerization of two Co(II) complexes to form a binuclear one. In fact, it was found that over a period of about 2 h, a paramagnetic [O 2 -Co(II)(Carnos) 2 ] complex is replaced by a diamagnetic [(Carnos) 2 Co(II)-O 2 -Co(II)(Carnos) 2 ] complex.…”

Sonochemical synthesis of tri-nuclear lead(II)-azido nano rods coordination polymer with 3,4,7,8-tetramethyl-1,10-phenanthroline (tmph): Crystal structure determination and preparation of nano lead(II) oxide

“…3,4,7,8-tetramethyl-1,10-phenanthroline (tmph) is a kind of bidentate N/N phenanthroline derive ligands with abilities of combining with metal and forming p-p stacking interactions between the parallel aromatic rings, and its interesting structures of supramolecular metal coordination compounds have been built [10][11][12][13][14][15][16][17][18][19]. As a heavyp-block metal ion, lead(II), with its large radius, flexible coordination environment, and variable stereochemical activity, is suitable for formation of unusual network topologies with interesting properties [20][21][22][23][24][25].…”