Outer-sphere Charge Transfer Excitation Research Articles

ChemInform Abstract: Photochemistry of Transition Metal Complexes Induced by Outer-Sphere Charge Transfer Excitation

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Photochemical oxidative addition of hydrazinium cations to tetracyanoplatinate(II) induced by OSCT excitation

The hydrazinium cations N2H62+/N2H5+ form ion pairs with [Pt(CN)4]2−. Outer-sphere charge transfer excitation (PtII→N2H62+/N2H5+) induces an oxidative addition: N2H62+/N2H5+Pt(CN)42-→[PtIV(CN)4(NH3)2] and [Pt(CN)4(NH3)(NH2)], respectively.

Photolysis of the ion pair [Pt IV(NH 3) 5Cl] 3+S 2O 82−: reduction of platinum(IV) induced by outer-sphere charge transfer excitation

The ion pair [Pt IV(NH 3) 5Cl] 3+S 2O 8 2− shows a S 2O 8 2− → [Pt(NH 3) 5Cl] 3+ outer-sphere charge transfer (OSCT) absorption at λ max=267 nm. OSCT excitation leads to the reduction of Pt(IV) by S 2O 8 2− to Pt(II) with φ=3×10 −3 at λ irr=280 nm.

Photolysis of the ion pair triphenylsulfonium thiophenolate induced by outersphere charge transfer excitation

Abstract The ion pair Ph3S+PhS− can be viewed as a sulfur-based mixed-valence system which is characterized by a PhS− to Ph3S+ outersphere charge transfer (OSCT) absorption at λmax=390 nm (in CHCl3). OSCT excitation leads to the radical pair Ph3S/PhS which undergoes subsequent elimination and radical coupling processes with the final formation of Ph2S. The photolysis proceeds with a quantum yield of φ=0.23 at λirr=436 nm.

Charge transfer interaction between bis(triphenylphosphine)copper(I) borohydride and 9,10-phenanthrenequinone.: Absorption spectrum and photoreactivity of the donor–acceptor adduct

The complex (PPh 3) 2CuBH 4 and 9,10-phenanthrenequinone form a weak adduct in CH 2Cl 2 which dissociates into its components in DMSO. The adduct is characterized by (PPh 3) 2CuBH 4→phenanthrenequinone outer sphere charge transfer (OSCT) absorptions at λ max=707 and 514 nm. The coordinated BH 4 − ligand reduces the quinone to hydroquinone thermally and photochemically by OSCT excitation with φ=0.05 at λ irr=700 nm.

Notizen: Optical Outer-Sphere Charge Transfer and Photoreactivity of the Ion Pair Tetrabutylammonium Tetrabutylborate

Abstract The ion pair [N(n-butyl)4]+[B(n-butyl)4]- in CCl4 shows a BR4 - → NR4 + outer-sphere charge transfer (OSCT) absorption at λ = 306 nm (sh, ε = 420 dm3 M-1 cm-1). OSCT excitation of the ion pair in CH2Cl2 (λirr > 275 nm) leads to a photo­ lysis with ∅ = 1.5 x 10-3 at λirr = 280 nm. Octane is formed as photoproduct.

Photoreduction of aqueous ferrioxamine B by oxalate induced by outer-sphere charge transfer excitation

The Fe(III) siderophore cation [ ferrioxamine B ] + and oxalate form an ion pair which shows an outer-sphere charge transfer (OSCT) absorption at λ max=262 nm. While ferrioxamine B is not light-sensitive the aqueous ion pair [ ferrioxamine B ] + C 2 O 4 2− undergoes a photoreduction to Fe(II) upon OSCT excitation.

Outer-Sphere Charge-Transfer Excitation in the Ion Pair [Co(NH3)6]3+[B12H12]2-

The aqueous ion pair [Co(NH3)6]3+[B12H12]2- displays an UV absorption at λmax = 250 nm which is assigned to an outer-sphere charge-transfer (OSCT) transition from [B12H12]2- to [Co(NH3)6]3+. OSCT excitation leads to photoredox reaction with the formation of Co2+ (Φ = 0.03 at λirr = 313 nm).

Photochemical reduction of 1-methyl-3-carbamoyl-pyridinium by cyanoborohydride induced by outer-sphere charge transfer excitation

The NAD + subunit 1-methyl-3-carbamoyl pyridinium cation (or 1-methyl nicotinamide cation, MNA +) forms an ion pair with BH 3CN − which shows a new absorption ( λ max=453 nm) which is assigned to an outer-sphere charge transfer (OSCT) transition from BH 3CN − to MNA +. At r.t. this ion pair is not stable and undergoes a hydride transfer from BH 3CN − to MNA + with the formation of MNAH. At −77°C this ion pair is persistent but the hydride transfer occurs as a photoreaction which is induced by OSCT excitation.

Photochemical reduction of 1-methyl-3-carbamoyl-pyridinium by hexacyanoferrate(II) induced by outer-sphere charge transfer excitation

The NAD+ subunit 1-methyl-3-carbamoyl pyridinium cation (or 1-methyl nicotinamide cation, MNA+) forms an ion pair with [Fe(CN)6]4− which shows a new absorption (λmax=392 nm) in the electronic spectrum. This band is assigned to an outer-sphere charge transfer (OSCT) transition from [Fe(CN)6]4− to MNA+. In aqueous solution OSCT excitation leads to a photoredox reaction with the formation of [Fe(CN)6]3− and the radical MNA which undergoes a dimerization or, more likely, a further reduction to MNAH.

Photolysis of the ion pair [ η7-C 7H 7Mo(CO) 3] +BPh 4− induced by outer sphere charge transfer excitation

The electronic spectrum of the ion pair [ η 7-C 7H 7Mo(CO) 3] +BPh 4 − in CH 2Cl 2 shows an outer sphere charge transfer (OSCT) absorption at λ max=370 nm. OSCT excitation yields [( η 6-C 7H 7Ph)Mo(CO) 3] with φ=0.02 at λ=405 nm.

Photochemical hydrogen transfer from bis(i-propylcyclopentadienyl) tungsten dihydride to 9,10-phenanthrenequinone induced by outer sphere charge transfer excitation

The electronic spectrum of the addition compound (i-C 3H 7C 5H 4) 2WH 2 · 9,10-phenanthrenequinone displays a longest-wavelength absorption at λ max = 530 nm which is assigned to an outer sphere charge transfer (OSCT) transition from the hydride complex to the quinone. OSCT excitation of the complex leads to hydrogen transfer from the hydride to the quinone. This photoreaction which yields 9,10-phenanthrenediol proceeds with φ = 0.01 at λ irr = 546 nm.

Notizen: Photoredox Reaction of [Hg(cyclam)]2+[Co(CO)4]⁻ Induced by Outer Sphere Charge Transfer Excitation

The ion pair [Hg(cyclam)]2+[Co(CO)4]- displays a Co(–I) to Hg(II) metal-to-metal charge transfer (MMCT) band at 288 nm. Upon MMCT excitation the ion pair undergoes a photoconversion to [HgCO2(CO)8].