Ferromagnetic coupling in d¹–d³ linear oxido-bridged heterometallic complexes: ground-state models of metal-to-metal charge transfer excited states

Abstract

Convenient strategies have been developed to synthesize heterobi/trimetallic oxido complexes containing V(IV)-O-Cr(III), V(IV)-O-Cr(III)-O-Ti(IV) and V(IV)-O-Cr(III)-O-V(IV) cores. These compounds can serve as ground state models for probing the magnetic properties of metal-to-metal charge transfer excited states. Each of these complexes represents the first experimental demonstration of ferromagnetic coupling in a d(1)-d(3) oxido bridged compound, which confirms a long standing theoretical prediction for such a linkage. Structural characterization reveals a similar structure for each of the bi/trimetallic complexes with identical V[double bond, length as m-dash]O bond lengths (∼1.644 Å) and a linear V-O-Cr geometry. The Cr-O distances (1.943-1.964 Å) are significantly influenced by the ligands in the trans axial positions. Ferromagnetic coupling between the V(IV) and Cr(III) of V-O-Cr is measured by temperature-dependent magnetic susceptibility, showing J = +42.5 to +50.7 cm(-1) (H = -2JŜVŜCr). This is further supported by variable temperature X-band EPR. The values of J are found to be consistent with the function J = Ae(βr) (A = 9.221 × 10(8) and β = 8.607 Å(-1)), where r is the Cr-O bond distance. We propose a model that links either ferromagnetic or antiferromagentic exchange coupling with long excited state lifetimes in metal-to-metal charge transfer (MMCT) chromophores.

Phosphorescent heterobimetallic complexes involving platinum(iv) and rhenium(vii) centers connected by an unsupported μ-oxido bridge

“…The 1 H, 13 C and 31 P NMR spectra were recorded on a Bruker Avance DRX 400 MHz spectrometer. The chemical shifts and coupling constants are in ppm and Hz, respectively.…”

“…3 J HH = 6.5, 1H, CH group adjacent to the ligating C atom of bhq), 7.1 (d, 3 J PtH = 8.9 Hz, 3 J HH = 4.8 Hz, 1H, CH group adjacent to the ligating N atom of bhq). 13 3 J HH = 4.9 Hz, the CH group adjacent to the ligating N atom, 1H). 13 3 J PH = 7.5 Hz, 3H, the Me ligand trans to the ligating P atom), 1.60 (d, 2 J PtH = 67.6 Hz, 3 J PtH = 7.5 Hz, 3H, the Me ligand trans to the ligating N atom), 7.12 (d, 3 J PtH = 15.5 Hz, 3 J HH = 1.7, the CH group adjacent to the ligating C atom), 7.71 (d, 3 J PtH = 8.7 Hz, 3 J HH = 4.8 Hz, the CH group adjacent to the ligating N atom).…”

“…13 3 J PH = 7.5 Hz, 3H, the Me ligand trans to the ligating P atom), 1.60 (d, 2 J PtH = 67.6 Hz, 3 J PtH = 7.5 Hz, 3H, the Me ligand trans to the ligating N atom), 7.12 (d, 3 J PtH = 15.5 Hz, 3 J HH = 1.7, the CH group adjacent to the ligating C atom), 7.71 (d, 3 J PtH = 8.7 Hz, 3 J HH = 4.8 Hz, the CH group adjacent to the ligating N atom). 13…”

“…These observations encourage chemists to synthesize heterobimetallic compounds involving two different metal centers connected by an unsupported oxido bridge, the idea being that such a system will be more efficient than the one involving the individual metal centers for various fundamental reactions. [11][12][13][14] The synthesis of advanced multifunctional materials can also be envisaged through the combination of metal centers with catalytic and optical properties.…”

Solventless Coupling of Epoxides and CO2 in Compressed Medium Catalysed by Fluorinated Metalloporphyrins

“…The metalloporphyrin 7, previously reported in [42][43][44][45] was synthesised, in high yields, by the reaction of equimolar amounts of pyrrole with 4-(trifluoromethyl)benzaldehyde in a The metalloporphyrin 7, previously reported in [42][43][44][45] was synthesised, in high yields, by the reaction of equimolar amounts of pyrrole with 4-(trifluoromethyl)benzaldehyde in a nitrobenzene/acetic acid mixture, using NaY zeolite as solid catalyst [39], followed by the complexation of p-CF 3 TPP with CrCl 2 and in situ air oxidation [40] in refluxing DMF (Scheme 1).…”