Photochemical properties of the cyclopentadienyliron complex of phenothiazine

Abstract

Photolysis of [([eta superscript 6]-phenothiazine)([eta superscript 5]-cyclopentadienyl)]iron(II) hexafluorophosphate (1) has been examined in various solvents such as MeOH, DMSO, THF, MeCN, furan, CH[subscript 2]Cl[subscript 2], CF[subscript 3]CH[subscript 2]OH and (CF[subscript 3])[subscript 2]CHOH. Photoreactions are induced by excitation at [lambda] = 254, 313, 337, 366, 514.5 and 647.5 nm. The major reaction leads to the photorelease of phenothiazine (2) which does not react further under the reaction conditions. Quantum yields of photolysis of 1, [phi](1), and photorelease of 2, [phi]([subscript 2]), are independent of concentration in the range of 1 × 10[superscript –4]–1 × 10[superscript–2] mol dm[superscript–3], wavelength of excitation and light intensity and in MeOH, MeCN, furan and THF, [phi]([subscript 1]) = [phi]([subscript 2]) = ca. 1. The quantum yields are lower in solvents of lower nucleophilicity and in CH[subscript 2]Cl[subscript 2], CF[subscript 3]CH[subscript 2]OH and (CF[subscript 3])[subscript 2]CHOH the [phi]([subscript 1]) values are 0.45, 0.26 and 0.03, respectively. In some solvents ferrocene formation is also observed. Applying oxygen as a quencher it is found that photochemical decay of 1 takes place from the excited state [superscript 3]E[subscript 1], with a lifetime of [tau][subscript 3][Epsilon][subscript 1] < 10[superscript –8]s and leads to formation of 2.