Photochemical and photophysical properties of ion-pair charge transfer complexes for all-optical information processing |
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Institution: | 1. Department of Physics, University of Punjab, Lahore, Pakistan;2. Institute of Bio-Sensing Technology, UWE, Bristol, UK;3. Department of Physics, NED University of Engineering & Technology, Karachi, Pakistan |
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Abstract: | The photochemical and photophysical properties of ion-pair charge transfer (IPCT) complexes comprising of 4,4′-bipyridinium and various counter ions have been reviewed. Quantum chemical and thermodynamic properties of IPCT complexes are summarized. IPCT complexes of 4,4′-bipyridinium with tetraphenylborate derivatives showed specific absorption and fluorescence properties. The photoinduced electron transfer from a counter anion to 4,4′-bipyridinium cation occurred within less than 100 fs upon excitation of IPCT complexes. The back electron transfer was controlled by changing counter anions and/or microenvironments. The transient absorption spectroscopy showed the ultrafast back electron transfer between 4,4′-bipyridinium and iodide in less than 2 ps. The absorption spectra of reduced 4,4′-bipyridinium derivatives were controlled over a broad range covering from visible to optical telecommunication wavelength. This phenomenon was applied to all-optical light modulation based on the guided wave mode devices composed of a photoresponsive polymer layer and a low-refractive-index polymer layer. |
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