Synthesis and photophysical properties of a new two-photon absorbing chromophor containing imidazo[4,5-f][1,10]phenanthroline

A new two-photon absorption compound, 2-{4-[(dicyanomethylidene-5,5-dimethylcyclohexl)vinyl]phenyl}imidazo[4,5-f][1,10]phenanthroline (DDVPIP), was synthesized and characterized. Its two-photon absorption (TPA) cross-section is obtained as 62 GM (1 GM = 1 × 10−50 cm4 photon−1 molecule−1) with 200 fs laser pulses at 800 nm. The one-photon excited fluorescence (OPEF) and two-photon excited fluorescence (TPEF) of DDVPIP are sensitive to the acid/base of the solution, which are enhanced in the basic solution but weakened in acidic solution. Charge-transfer (CT) states of DDVPIP were calculated through theory methods to explain its acid-base-sensitive fluorescent properties.