The main photophysical properties of a series of recently synthetized 1,2- and 1,3-squaraines, including absorption electronic spectra, singlet-triplet energy gaps, and spin-orbit matrix elements, have been investigated by means of density functional theory (DFT) and time-dependent DFT approaches. A benchmark of three exchange-correlation functionals has been performed in six different solvent ...

Intermediates (trimethylenes) formed upon bond cleavage of three-membered rings are usually too unstable for direct characterization. They may. however. he stabilized by substitution and by incorporation into a cyclic system where the ring closed form is strained and conrotatory closure of the trimethylene is inhibited. These principles have been applied to two heterobicyclo[2.l .O]pentane syst...

A large solvent polarity effect on the rate of singlet to triplet intersystem crossing (ksT) has been observed in the carbenes, diphenylcarbene (DPC) and dicycloheptadienylidene (DCHD)it is found that both ksT and the energy splitting (A&T) separtaing the singlet and triplet states decrease as the solvent polarity increases for the aromatic carbenes. This “inverse” gap effect, i.e. the time for...

The interpretation of the ultrafast luminescence decay in [Re(Br(CO)3(N^N)] complexes as a new group of chromophoric imidazo[4,5-f]-1,10-phenanthroline ligands, including 1,2-dimethoxy benzene, tert-butyl benzene (L4) and 1,2,3-trimethoxy benzene, tert-butyl benzene (L6), was studied. Fac-[Re(Br(CO)3L4 and L6] with different aryl groups were calculated in singlet and triplet excited states. The...

Photolysis of N-benzoyl-S,S-diphenylsulfilimine or N-benzoyl dibenzothiophene sulfilimine produces PhNCO and also benzoylnitrene. Direct observation of the triplet nitrene, energetic differences between the singlet and triplet state of the nitrene, and oxygen quenching experiments suggest that the triplet nitrene derives from the triplet excited state of the sulfilimine precursors, rather than ...

The geometries and relative stabilities of the singlet and triplet states of phenyl- (Cs), diphenyl- (C2), 1-naphthyl- (Cs), di(1-naphthyl)- (C2), and 9-anthryl-substituted (Cs) carbenes were investigated at the B3LYP/6-311+G(d,p) + ZPVE level of density functional theory. The singlet-triplet energy separations (DeltaEST), 2.7, 2.9, 3.4, 3.7, and 5.7 kcal/mol, respectively, after including an e...

The reaction pathways for the photochemical formation of cyclobutane thymine dimers in DNA are explored using hybrid density functional theory techniques. It is concluded that the thymine-thymine [2 + 2] cycloaddition displays favorable energy barriers and reaction energies in both the triplet and the singlet excited states. The stepwise cycloaddition in the triplet excited state involves the i...

Using pulse radiolysis and triplet energy transfer has enabled us to measure the triplet energies in a broad range of different pi-conjugated polymers. In all cases we find that the 1 (3)B(u) is of order 0.6 to 1 eV below the 1 (1)B(u), indicative of localized triplet states with strong electron-electron correlation. We also observe that the 1 (1)A(g)-1 (3)B(u) gap decreases linearly as the 1 (...