Search results for "PHOTOCHEMISTRY"

Electrolyte-driven electrochemical amplification by poly(thienylacetylene) encapsulated within Zeolite Y

2006

Electrochemical oxidation and reduction of poly(thienylacetylene) encapsulated inside zeolite Y (PTA@Y) exhibit with large anodic and cathodic doping currents with a significant reversibility. Thienyl groups lower the redox potential of polyacetylene chain whereas encapsulation stabilizes the resulting charged radical species blocking undesired post electron-transfer cross-link reactions. Size-exclusion effects associated produces an electrolyte-dependent amplification of currents recorded at PTA@Y-modified electrodes for electrochemical processes involving selected substrates in solution, namely, dinitrobiphenyl and benzidine. Keywords: Poly(thienylacetylene), Zeolite Y, Electrochemistry, …

Influence of spatial arrangements of π-spacer and acceptor of phenothiazine based dyes on the performance of dye-sensitized solar cells

2013

Abstract Three phenothiazine based organic dyes PTA , PDTA and PTDA with D– π –A, π –D– π –A and A– π –D– π –A frameworks were designed and synthesized for the dye sensitized solar cells (DSSCs). Phenothiazine with octyloxyphenyl moiety acts as donor while thiophene and cyanoacetic acid units act as a π -spacer and an acceptor, respectively. The effects of the molecular structures of the dyes on the performance of the DSSCs were investigated systematically along with their photophysical and photoelectrochemical properties. The dye PTDA with A– π –D– π –A framework exhibited a better light harvesting capacity and an effective electron extraction pathway from the electron donor to the TiO 2 s…

Strong donor–acceptor couplings in a special pair-antenna model

2010

A special pair model composed of two cofacial zinc porphyrins (acceptor) linked to a free base (donor) acts as an energy transfer dyad. Despite the absence of conjugation, ππ*/charge transfer excited states and ultrafast energy transfer (∼5 ps) are noted.

Ultraviolet luminescence of ScPO4, AlPO4 and GaPO4 crystals.

2013

The luminescence of self-trapped excitons (STEs) was previously observed and described for the case of tetragonal-symmetry ScPO4 single crystals. The subject band in this material is situated in the UV spectral range of ?210?nm or ?5.8?eV. In the present work, we are both expanding this earlier luminescence study and seeking to identify similar luminescence phenomena in other orthophosphate crystals, i.e., AlPO4 and GaPO4. These efforts have proven to be successful?in spite of the structural differences between these materials and ScPO4. Specifically we have found that for AlPO4 and GaPO4, in addition to an ?-quartz-like STE, there is a UV luminescence band that is similar in position and d…

Cover Feature: Visible Light‐Induced Sulfonylation/Arylation of Styrenes in a Double Radical Three‐Component Photoredox Reaction (Chem. Eur. J. 38/20…

2019

Understanding the mechanism of the Povarov reaction. A DFT study

2014

The molecular mechanism of the Povarov reaction in acetonitrile has been studied at the MPWB1K/6-311G** level of theory. This reaction follows a domino process that comprises two sequential reactions: (i) a Lewis acid catalysed aza-Diels–Alder (A-DA) reaction between a N-aryl imine and a nucleophilic ethylene yielding a formal [4 + 2] cycloadduct; (ii) a stepwise 1,3-hydrogen shift at this intermediate affording the final tetrahydroquinoline. At this computational level, the Lewis acid catalysed A-DA reaction presents a two-step mechanism as a consequence of the large stabilisation of the corresponding zwitterionic intermediate. Our study allows establishing that the N-aryl substituent has …

Molecular Stark-effect spectroscopy of Prodan and Laurdan in different solvents and electric dipole moments in their equilibrated ground and Franck–C…

2007

Abstract The results from electrooptical absorption measurements (EOAM) on the ground and excited Franck–Condon state dipole moments of Prodan and Laurdan in 1,4-dioxane and cyclohexane are presented. The ground and excited Franck–Condon state electric dipole moments as well as the respective transition moment of both probes are parallel. The electric dipole moments of Prodan and Laurdan in the ground state in cyclohexane and 1,4-dioxane have values within the range (15.7–16.5) × 10 −30  C m. On optical excitation the dipole moments increase by (42.1–49.5) × 10 −30  C m. The obtained results are compared with the values of the dipole moments of Prodan and Laurdan determined by other methods.

Innentitelbild: An Unusually Small Singlet-Triplet Gap in a Quinoidal 1,6-Methano[10]annulene Resulting from Baird’s 4nπ-Electron Triplet Stabilizati…

2015

ChemInform Abstract: On-Surface Reactions

2015

Photochemical window mechanism for controlled atom release in carborane endohedral boxes: Theoretical evidence

2006

Abstract On the basis of high-level quantum chemical calculations, closed-cage carboranes are shown to be prospective nanoscale mass selective conveyors via a photochemical switch. A mechanism is evidenced in which stable carborane boxes with lithium as endohedral atom, Li@CB 11 H 12 , can be photoinduced to sequentially evolve opening the cage, releasing the internal atom through a window in the box structure, and closing the cage toward either ionic or neutral channels where the charge or spin of the fragments may be controlled.