Kinetics of unusual photoinduced currents in the solid state of some ferrocene derivatives

Kinetics of change in photoinduced currents (during illumination and after switching off light source) in the solid state of some ferrocene derivatives, namely, ferrocenecarboxylic acid, acetylferrocene, ferrocenecarbaldehyde, hydroxymethyl ferrocene have been studied in dry nitrogen gas atmosphere. Unusual/ anomalous photocurrent versus time profiles were observed in some ferrocene derivatives at certain cell temperatures. The kinetics of current changes under photoexcitation and after switching off the light source have been observed to be complicated in nature. Temperature-dependent behavior of the studied kinetics indicates that charge carrier trapping/ detrapping and recombination processes are significantly temperature dependent. These processes have an important role in causing the temperature dependent unusual/ anomalous photocurrent versus time profiles in the ferrocene derivatives studied.Kinetics of unusual photoinduced currents in the solid state of some ferrocene derivatives Aloke Kumar Chakraborty and Biswanath Mallik* Department of Spectroscopy, Indian Association for the Cultivation of Science, 2A & 2B, Raja S. C. Mullick Road, Jadavpur, Kolkata-700 032, India E-mail : [email protected] of Spectroscopy, Indian Association for the Cultivation of Science, 2A & 2B, Raja S. C. Mullick Road, Jadavpur, Kolkata-700 032, Indi

Photooxidation of Some Metallocenes in a Polymer Matrix

Abstract: The changes in the electronic absorption spectra (UV-Vis) of some metallocene-doped poly(methyl methacrylate) (PMMA) thin films containing chloroform molecules as impurities were studied after photoexcitation in the nitrogen atmosphere. Photoexcitations were made by monochromatic radiation (using a Xe-lamp source and a monochromator) at an interval of few nanometers in the spectral range 210-750 nm. The changes in spectra were studied as a function of photoexcitation time (duration), amount of metallocene in the film and the amount of chloroform molecules present in the film. Occurrence of photoinduced charge-transfer between some metallocenes and chloroform molecules confined in the PMMA thin films was observed, which indicated photooxidation of the metallocenes in the polymer matrix. Photoresponse in the case of ferrocene derivatives was observed to decrease with the increase in the value of para-Hammett constant for the substituent attached to the ferrocene unit and also with increasing half-wave potential for the ferrocene derivatives. Photoeffects on the metallocenes having different central metal atom were studied and it was noticed that the photoeffects on the metallocenes with "18 valence electrons", as in ferrocene and ruthenocene, favored the occurrence of photoinduced charge-transfer between the metallocene and chloroform molecules present in a PMMA film. The photooxidation of a metallocene in a PMMA thin film resulted in an enhanced photoconductivity of the polymeric film