Linear and Multi-Photon Fluorescence of Thiophene Based Copolymer with Electron-Accepting Side Chains.

A novel copolymer poly(thiophene-2,5-diyl-2,5-di-n-octyloxycarbonyl-1,4-phenylene), denoted as P33, is introduced as potential material for photovoltaics, polymer light-emitting diodes, and/or organic transistors. P33 dissolved in chloroform is investigated by steady-state absorption, linear/non-linear fluorescence spectroscopies and time-resolved fluorescence spectroscopy. Molar extinction coefficient, fluorescence quantum yield, and singlet fluorescence lifetime of P33 are determined to be 18,315 M cm, 0.

Fluorescence Dynamics of Monocyclodextrin- and Bis(thiol-cyclodextrin)-Coumarin C153 Complexes.

The solvation and confinement of coumarin C153 within supramolecular host/guest complexes based on β-cyclodextrin (β-CD) and 6-deoxy-6-thio-β-cyclodextrin (β-CD-SH) in water are studied by fluorescence spectroscopy. For β-CD/C153, the 1:1 complex is proposed, and for β-CD-SH/C153 both the 1:1 and 2:1 complexes are believed to be formed. The 2:1 β-CD-SH/C153 complex has an association constant of 4.

7-(Dimethylamino)coumarin-3-carbaldehyde and its phenylsemicarbazone: TICT excited state modulation, fluorescent H-aggregates, and preferential solvation.

The photophysical properties of 7-(dimethylamino)coumarin-3-carbaldehyde 3 and its phenylsemicarbazone 4 were investigated in solvents of various polarity and in differing solvent mixtures. The different fluorescent quantum yield (ΦF) behavior of 3 and 4 in highly polar solvents is discussed in terms of Twisted Intramolecular Charge-Tranfer (TICT) state formation and the specific solute-solvent interactions. Because of the weak intermolecular hydrogen bonding ability of both the radiative ICT and nonradiative TICT excited state of 3 and the linear steep decrease in ΦF from a medium to high polarity region, coumarin 3 could be a useful polarity probe for microenvironments containing hydrogen bonding groups.

Fluorescence dynamics of coumarin C522 as a function of micelle confinement along with cyclodextrin supramolecular complex formation.

Our aim is to doubly confine a molecule of coumarin C522 in a host-guest supramolecular complex with β-cyclodextrin in a reverse sodium dioctyl sulfosuccinate (AOT) micelle using nonpolar n-heptane and polar water solvents. Varying the volumes of coumarin C522 and β-cyclodextrin dissolved in water allows us to control the water-pool diameters of the reverse micelle in n-heptane with values of w=3, 5, 10, 20, and 40, where w is the ratio of water concentration to AOT concentration in n-heptane. To study the fluorescence dynamics of coumarin C522, the spectral steady-state and time-resolved dependences are compared for the two systems coumarin C522(water)/AOT(n-heptane), denoted C522/micelle, and coumarin C522/β-cyclodextrin(water)/AOT(n-heptane), referred to as C522/CD/micelle.