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The photooxidation of ferrocene in CCl 4 ethanol and CHCl 3 ethanol solutions has been investigated at several wavelengths of irradiation in the range 313-472 nm. No photoreaction was detected when the irradiation was carried out in the intramolecular ferrocene band with maximum at 440 nm. Irradiation in the spectral region where the ferrocene-to-halocarbon solvent charge transfer bands overlap the intramolecular ferrocene bands caused the oxidation of ferrocene to ferricenium cation. In this spectral region, only the light intensity absorbed by the charge-transfer to solvent band was active. The photooxidation reaction was found to involve a primary photochemical process was the dissociation of the charge-transfer-to-solvent excited state into a ferricenium cation, a chloride ion, and a radical (CCl 3 or CHCl 2 in the case of CCl 4 and CHCl 3 , respectively). In both acceptor solvents the primary photoprocess occurred with unitary efficiency with respect to the light absorbed by the charge-transfer-tp-solvent band. The secondary thermal oxidation of ferrocene was initiated by the radical species produced in the primary photoprocess. The efficiency of the secondary oxidation depended on concentrations of ferrocene, dissolved oxygen and radical scavengers.

The photochemical behaviour of some cyanide complexes has been investigated at various wavelengths, with particular reference to irradiation in the ligand field spectral region. [Co(CN)6]3− in acid or in aqueous solutions undergoes a photoaquation reaction with quantum yield 0·31 independently of the wavelength of irradiation (254, 313 and 365 mμ), of the concentration of the complex (2 × 10−2−3 × 10−3 F) and of the pH of the solution (2–7·5). The complicated processes that follow the irradiation at 254, 313 and 404 mμ of [Fe(CN)6]3− both in aqueous and in acid solutions have been investigated in detail and a reaction mechanism involving a primary photoaquation reaction is proposed. [Cr(CN)6]3− undergoes a photoaquation reaction when irradiated at 313 and 365 mμ. Irradiation of [Ni(CN)4]2− (254, 313 and 365 mμ), [Pd(CN)4]2− (254 mμ) and [Pt(CN)4]2− (254 mμ) does not cause any reaction. The results obtained in this investigation and in the previous ones concerning the photochemical behaviour of [Mo(CN)8]3−, [W(CN)8]3−, [Mo(CN)8]4−, [W(CN)8]4−, [Mn(CN)6]3− and [Fe(CN)6]4− have been correlated as far as d-d irradiation is concerned; the primary step in the photoreaction appears to be always related to the nature of the electronic state obtained by irradiation even when the overall photochemical reaction is conditioned by non-spectrocopic factors.

The excitation of azide-to-platinum charge-transfer transitions in the azidodiethylenetriamine-platinum(II) complex ion causes the formation of N3 radicals.