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Six new thiophene oligomers, here designated as tripodal-like oligothienyl imidazoles, were synthesized and have been investigated in ethanol solution at room and low temperature. The oligomers bear a common core where two or more thiophenes are linked to one or more imidazole unit which further links through its alpha position to a different number of incremental thiophene units. The study involves a comprehensive spectral and photophysical investigation where the properties of the singlet and triplet states have been investigated regarding absorption, fluorescence and phosphorescence, transient triplet-triplet absorption together with all relevant quantum yields (fluorescence, internal conversion, intersystem crossing and singlet oxygen) and lifetimes. In addition, DFT quantum chemical calculations were performed to gain a detailed understanding of the molecular geometry and optical properties of the investigated oligomers. From the overall data, the radiative (kF) and radiationless (kNR, kIC and kISC) rate constants have been determined and it is shown that, in contrast with the parent oligothiophenes, the radiative competes with the radiationless deactivation channels. The results show that, by comparison with the oligothiophene counterparts, there is an augment of the relative contributions of the internal conversion and fluorescence processes relative to the S1~~T1 intersystem crossing. Phosphosphorescence emission was found for the simplest member of the investigated compounds, with a low quantum yield and a lifetime of 8 picos. The data also show that the introduction of a 4,5-dithienyl-imidazole moiety in a bi- or terthiophene oligomer results in, respectively, a 20-fold and a 3-fold increase of the fluorescence quantum yield relative to their oligothiophene counterparts., Fundação para a Ciência e a Tecnologia (FCT)

A new optical-fiber-based spectrofluorometer for in vivo or in vitro detection of delayed fluorescence is presented and characterized. This compact setup is designed so that it can be readily adapted for future clinical use. Optical excitation is done with a nitrogen laser-pumped, tunable dye laser, emitting in the UV-vis part of the spectrum. Excitation and luminescence signals are carried to and from the biological tissues under investigation, located out of the setup enclosure, by a single optical fiber. These measurements, as well as measurements performed without a fiber on in vitro samples in a thermostable quartz cell, in a controlled-atmosphere enclosure, are possible due to the efficient collection of the laser-induced luminescence light which is collected and focused on the detector with a high aperture parabolic mirror. The detection is based on a gated photomultiplier which allows for time-resolved measurements of the delayed fluorescence intensity. Thus, relevant luminescence lifetimes, typically in the sub-microsecond-to-millisecond range, can be measured with near total rejection of the sample's prompt fluorescence. The instrument spectral and temporal resolution, as well as its sensitivity, is characterized and measurement examples are presented. The primary application foreseen for this setup is the monitoring and adjustment of the light dose delivered during photodynamic therapy. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3558846]

Immobilization of [60]fullerene onto gamma-Al(2)O(3) surface provides new heterogeneous photocatalysts for the oxidation of organic Compounds under oxygen atmosphere. These catalysts have been prepared by simple or Successive incipient wetness impregnation (using an organic solvent) followed by air-heating at 180 degrees C. In the C(60)/Al(2)O(3) system. C(60) loading was varied in the range of 1-4% (w/w). Several experimental techniques including BET. XRD, DRS, TGA, microelectrophoresis, photoluminescence and kinetic extraction, have been used to characterize these catalytic materials. It was found that the quite high surface exposed by the supported C(60) increases with the amount of the supported C(60), while the dispersion of the supported C(60) decreases. The quite stable supported [60]fullerene phase is comprised from C(60) clusters, small and large aggregates. This non-uniform size distribution is reflected to a non-uniform distribution concerning the 'supported phase-support' interactions. These interactions decrease with the amount of the supported C(60). The photocatalysts prepared may be safely used Lip to 200 degrees C. Above this temperature the supported C(60) is sublimated/combusted in air. The photocatalytic activity of the so-obtained catalytic systems has been evaluated in terms of substrate conversion in the singlet oxygen 'ene' reaction of alkenes. The photooxygenation of 2-methyl-2-heptene has been examined as a probe reaction. It was round that the catalytic activity increases with the increasing amount of the supported C(60) up to the value of 3% (w/w) and then decreases. The intrinsic activity expressed as TON or TOF decreased monotonically with C(60). In all cases, however. the photocatalytic activity of the Al(2)O(3)-supported C(60) catalysts was substantially increased compared to the unsupported C(60) precursor, exhibiting quantitative conversion yields after short reaction times. The catalytic behavior was attributed to the aforementioned opposite trends which follow the surface exposed by the supported C(60) on one hand and the 'supported C(60)-support' interactions and the C(60) dispersion on the other hand. The easy separation of these solid catalysts from the reaction mixture, the high activity and stability as well as the retained activity in subsequent catalytic cycles. make these supported catalysts suitable for a small-scale synthesis. (C) 2009 Elsevier B.V. All rights reserved. Journal of Molecular Catalysis a-Chemical