Theory of electron transfer reactions: insights and hindsights

The synthetic system of Fe(SO3CF3)2 and one or two TPA ligands (TPA = tris(2-pyridylmethyl)amine) affords a series of complexes that demonstrate the complexities of the solid-state and solution coordination chemistry of labile iron(II) even with a multidentate ligand. The low-spin [Fe(TPA)(CH3CN)2](SO3CF3)2 (1-OTf) complex forms in acetonitrile, but the high-spin complex Fe(TPA)(SO3CF3)2 (2) forms in chloroform. The methanol-bound complex [Fe(TPA)(CH3OH)2](BPh4)2 (3) forms in the presence of the noncoordinating anion, BPh4-, and six-coordinate [Fe(TPA)2](SO3CF3)2 (4-OTf) and eight-coordinate [Fe(TPA)2](BPh4)2 (4-BPh4) form in the presence of excess ligand. Their behavior in solution is explored by studying their magnetic properties and NMR spectra, which indicate the presence of spin and coordination equilibria. The crystal structures of these complexes are reported. Crystallographic parameters are as follows. 1-OTf·CH3CN:  C26H27F6FeN7O6S2, monoclinic, P21/n, a = 12.418(2) A, b = 16.192(4) A, c = 15.855(...

Iron(II) Polyamine Chemistry: Variation of Spin State and Coordination Number in Solid State and Solution with Iron(II) Tris(2-pyridylmethyl)amine Complexes

A one-step and energy-saving method was proposed to synthesize hierarchical and hollow Co(VO3)2-Co(OH)2 composite leaf arrays on carbon cloth, which expressed high capacitance (522 mF cm–2 or 803 F g–1 at the current density of 0.5 mA cm–2), good rate capability (79.5% capacitance retention after a 30-fold increase of the current density) and excellent cycling stability (90% capacitance retention after 15 000 charge–discharge cycles) when tested as a supercapacitor electrode.

Energy-Saving Synthesis of MOF-Derived Hierarchical and Hollow Co(VO3)2-Co(OH)2 Composite Leaf Arrays for Supercapacitor Electrode Materials.

Quantum rate theory, molecular dynamics simulations, and semiempirical electronic structure calculations are used to fully investigate electron transfer mediated by a solvated polypeptide for the first time. Using a stationary-phase approximation, the nonadiabatic electron-transfer rate constant is calculated from the nuclear free energies and the electronic coupling between the initial and final states. The former are obtained from quantum path integral and classical molecular dynamics simulations; the latter are calculated using semiempirical electronic structure calculations and the generalized Mulliken−Hush method. Importantly, no parameters are fit to kinetic data. The simulated system consists of a solvated four-proline polypeptide with a tris(bipyridine)ruthenium donor group and an oxypentamminecobalt acceptor group. From the simulation data entropy and energy contributions to the free energies are distinguished. Quantum suppression of the barrier, including important solvent contributions, is demo...

A. Mueller

Papers

Skeletal vibrational spectra, force constants, and bond properties of transition metal ammine complexes