2551-53-3

We describe the charge transfer interactions between photoexcited CdS nanorods and mononuclear water oxidation catalysts derived from the [Ru(bpy)(tpy)Cl]+ parent structure. Upon excitation, hole transfer from CdS oxidizes the catalyst (Ru2+ → Ru3+) on a 100 ps to 1 ns timescale. This is followed by 10-100 ns electron transfer (ET) that reduces the Ru3+ center. The relatively slow ET dynamics may provide opportunities for the accumulation of multiple holes at the catalyst, which is necessary for water oxidation.

The molecular mechanism of precursor evolution in the synthesis of colloidal group II-VI semiconductor nanocrystals was studied using 1H, 13C, and 31P NMR spectroscopy and mass spectrometry. Tri-n-butylphosphine chalcogenides (TBPE; E = S, Se, Te) react with an oleic acid complex of cadmium or zinc (M-OA; M = Zn, Cd) in a noncoordinating solvent (octadecene (ODE), n-nonane-d20, or n-decane-d22), affording ME nanocrystals, tri-n-butylphosphine oxide (TBPO), and oleic acid anhydride ((OA)2O). Likewise, the reaction between trialkylphosphine selenide and cadmium n-octadecylphosphonic acid complex (Cd-ODPA) in tri-n-octylphosphine oxide (TOPO) produces CdSe nanocrystals, trialkylphosphine oxide, and anhydrides of n-octadecylphosphonic acid. The disappearance of tri-n-octylphosphine selenide in the presence of Cd-OA and Cd-ODPA can be fit to a single-exponential decay (kobs = (1.30 ± 0.08) × 10-3 s-1, Cd-ODPA, 260 °C, and kobs = (1.51 ± 0.04) × 10-3 s-1, Cd-OA, 117 °C). The reaction approaches completion at 70-80% conversion of TOPSe under anhydrous conditions and 100% conversion in the presence of added water. Activation parameters for the reaction between TBPSe and Cd-OA in n-nonane-d20 were determined from the temperature dependence of the TBPSe decay over the range of 358-400 K (ΔH? = 62.0 ± 2.8 kJ·mol-1, ΔS? = -145 ± 8 J·mol-1·K-1). A reaction mechanism is proposed where trialkylphsophine chalcogenides deoxygenate the oleic acid or phosphonic acid surfactant to generate trialkylphosphine oxide and oleic or phosphonic acid anhydride products. Results from kinetics experiments suggest that cleavage of the phosphorus chalcogenide double bond (TOP=E) proceeds by the nucleophilic attack of phosphonate or oleate on a (TOP=E)-M complex, generating the initial M-E bond.