56 research outputs found
Crystallographic coincidence of two bridging species in a dinuclear CoIII ethynylbenzene complex
In the title compound, trans,trans-[μ-(m-phenylene)bis(ethyne-1,2-diyl)]bis[chlorido(1,4,8,11-tetraazacyclotetradecane)cobalt(III)]–trans,trans-[μ-(5-bromo-m-phenylene)bis(ethyne-1,2-diyl)]bis[chlorido(1,4,8,11-tetraazacyclotetradecane)cobalt(III)]–tetraphenylborate–acetone (0.88/0.12/2/4), [Co2(C12H4)Cl2(C10H24N4)2]0.88[Co2(C10H3Br)Cl2(C10H24N4)2]0.12(C24H20B)2·4C3H6O, with the exception of the acetylene and bromine groups, all atomic postitions are the same in the two compounds and are modeled at full occupancy. The CoIII ions are six-coordinate with acetylide and chloride ligands bound to the axial sites and the N atoms from the cyclam rings coordinated at the equatorial positions. N—H⋯O and N—H⋯Cl hydrogen-bonding interactions help to consolidate the crystal packing
Structural and Electronic Comparison of 1st Row Transition Metal Complexes of a Tripodal Iminopyridine Ligand
We report the preparation and characterization of a series
of divalent
3d transition metal complexes (Cr to Zn, <b>1</b>–<b>7)</b>, featuring the multidentate, tripodal iminopyridine Schiff-base
ligand trimethyl 6,6′,6″-((1E,1′E,1″E)-((nitrilotris(ethane-2,1-diyl))tris(azanylylidene))tris-(methanylylidene))trinicotinate
(<b>L</b><sup><b>5‑OOMe</b></sup>). X-ray structural
studies carried out on <b>1</b>–<b>5</b> and <b>7</b> reveal complex geometries ranging from local octahedral
coordination to significant distortion toward trigonal prismatic geometry
to heptacoordinate environments. Regardless of coordination mode,
magnetic and spectroscopic studies show the ligand to provide moderately
strong ligand fields: the Fe complex is low-spin, while the Co and
Mn complexes are high-spin at all temperatures probed. Cyclic voltammograms
exhibit multiple reversible ligand-based reductions, which are relatively
consistent throughout the series; however, the electrochemical behavior
of the Cr complex <b>1</b> is fundamentally different from those
of the other complexes. Time-dependent (TD) density functional theory
(DFT) and natural transition
orbital (NTO) computational analyses are presented for the ligand,
its anion, and complexes <b>1</b>–<b>7</b>: the
computed spectra reproduce the major differential features of the
observed visible absorption spectra, and NTOs provide viable interpretations
for the observed features. The combined studies indicate that all
complexes contain neutral ligands bound to M(II) ions, except for
the Cr complex <b>1</b>, which is best described as a Cr(III)
species bound to a radical anionic ligand
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