ULTRAFAST PHOTON-MODE RECORDING AND SWITCHING BY PHOTOINDUCED ELECTRON-TRANSFER

Ultrafast photon-mode recording and switching based on photoinduced el ectron transfer was proposed using ion-pair charge-transfer (IPCT) com plexes of 4,4'-bipyridinium salts. Specific IPCT complexes were formed with tetrakis[3,5(trifluoromethyl)phenyl]borate. Ultrafast colour cha nges (< 1 ps) were observed upon excitation of IPCT absorption. Such e xtremely fast colour changes were due to the fact that the IPCT absorp tion band is associated with the electronic transition from a partiall y charge-transferred ground state to an almost completely charge-separ ated excited state. The decay was controlled over a very wide range fr om ps to infinity by counter anions, the temperature, or the microenvi ronment. Molecular orientation of photogenerated radical cations and h ighly sensitive detection of colour changes even in a single monolayer film were also achieved.