A heterogeneous catalyst, nanosized MCM-41-Pd, was used to catalyze the Sonogashira coupling of aryl and heteroaryl halides with terminal alkynes in the presence of CuI and triphenylphosphine. The coupling products were obtained in high yields using low Pd loadings to 0.01 mol%, and the nanosized MCM-41-Pd catalyst was recovered by centrifugation of the reaction solution and re-used in further runs without significant loss of reactivity.

Sonogashira Reaction of Aryl and Heteroaryl Halides with Terminal Alkynes Catalyzed by a Highly Efficient and Recyclable Nanosized MCM-41 Anchored Palladium Bipyridyl Complex

The present work focuses on the current interest in diyne bridged chromophores necessitating a clearer understanding of the photophysics of such molecules. The significance of the diyne moiety in the photophysics has been investigated by synthesizing simple substituted diphenyl butadiynyl derivatives following a quick and efficient microwave assisted Eglinton coupling of terminal alkynes. Emission of the fluorophores is observed from the usual locally excited (LE) state and intramolecular charge transfer (ICT) state. Separation of pure ICT emission from pure LE emission has been carried out by Gaussian/Lorentzian curve fitting. The vibronic coupling in the local transitions appears to be confined to the normal mode involving the C–C triple bond stretching of the diyne moiety. This implies that the LE transition involves the diyne moiety, a conclusion supported by quantum chemical calculations. The resolved ICT emission follows double linear dependence on ET(30) solvent polarity scale. The important role o...

Deciphering the Photophysical Role of Conjugated Diyne in Butadiynyl Fluorophores: Synthesis, Photophysical and Theoretical Study

Poly(2,5-thienylene ethynylene) and related oligomers

Tin ethyl etiopurpurin is a promising second generation photosensitizer for photodynamic treatment of cancer. This compound is only poorly soluble in aqueous media and, therefore, needs a delivery system for administration to animals. Successful tumor eradication has previously been reported, following light exposure of rats previously administered with the purpurin formulated as a Cremophor El emulsion, in dipalmitoyl-phosphatidyl-choline liposomes or with gamma cyclodextrins. In this paper, we describe some absorbance and fluorescence studies of tin ethyl etiopurpurin in homogeneous and heterogeneous systems. In general, absorption and emission maxima were found to be red shifted as the environment changed from polar to non-polar. The viscosity and dielectric constant of the medium affected the purpurin fluorescence intensity. The liposome preparations were characterized by particle size determination, differential scanning calorimetry and by sensitizer fluorescence quenching studies. Photobleaching studies also showed variation owing to changes in the environment in which the dye was located.

Spectroscopic studies of tin ethyl etiopurpurin in homogeneous and heterogeneous systems.

Synthesis and spectroscopic characterization of (CO)6Fe2{μ-EC(H)=C(2-Th)E′)(E,E′=S, Se, Te; Th=C4H3S) structural characterization of (CO)6Fe2{μ-SeC(H)=C(2-Th)Se}

A convenient method for the preparation of thienylacetylnes

1,4-Bis(3′-quinolyl)-1,3-butadiyne (3DQ) and 1,4-bis(2′-pyridyl)-1,3-butadiyne have been found to be fluorescent. The fluorescence spectra, quantum yields φf, fluorescence lifetimes τf, fluorescence rate constants kf in different solvents and low temperature emission spectra are reported. The pH dependence and iodine and iodide quenching behaviour of 3DQ emission have been analysed. Monoprotonated 3DQH+ and diprotonated 3DQH22+ species were found to be fluorescent. The emission behaviour of 3DQ in a solvent mixture and in the presence of β-cyclodextrin is reported.

P. Sekher

Papers

A convenient method for the preparation of thienylacetylnes

Emission studies of 1,4-bis(heteroary)-1,3-butadiynes

A Convenient Method for the Preparation of Thienylacetylenes.