Photochemical Properties Of The Cyclopentadienyliron Complex Of Phenothiazine

Photolysis of [(eta(6)-phenothiazine) (eta(5)-cyclopentadienyl)]iron(II) hexafluorophosphate (1) has been examined in various solvents such as MeOH, DMSO, THF, MeCN, furan, CH2Cl2, CF3CH2OH and (CF3)2CHOH. 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(2), are independent of concentration in the range of 1 x 10(-4)-1 x 10(-2) mol dm-3, wavelength of excitation and light intensity and in MeOH, MeCN, furan and THF, phi(1) = phi(2) = ca. 1. The quantum yields are lower in solvents of lower nucleophilicity and in CH2Cl2, CF3CH2OH and (CF3)2CHOH the phi(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 3E1, with a lifetime of tau(3E1) < 10(-8) s and leads to formation of 2.