The inner filter effect due to self-quenching dominates the normal emission of dyes at higher concentrations, which would limit their applications. Since normal emission was also observed with aggregation induced emission enhancement (AIEE) active excited state intramolecular proton transfer (ESIPT) exhibiting molecules, two new molecules are synthesized and studied to obtain normal emission fr...

The fluorescence spectra of 10-(4,6-dichloropyrimidin-5-yl)-5,15-dimesitylcorrole have been studied in the temperature range from 4.2 to 332 K. For the first time, the individual fluorescence profiles of the two corrole NH tautomers have been assigned over the whole temperature range. The pronounced temperature dependence of the fluorescence spectra of the meso-pyrimidinylcorrole under study wa...

We characterized anionic states of thymine using various electronic structure methods, with the most accurate results obtained at the CCSD(T)/aug-cc-pVDZ level of theory followed by extrapolations to complete basis set limits. We found that the most stable anion in the gas phase is related to an imino-oxo tautomer, in which the N1H proton is transferred to the C5 atom. This valence anion, aT(c5...

The conformations of eight neo-confused porphyrin (neo-CP) structures and seven related benzo-neo-confused porphyrins (B-neo-CPs) were minimized using DFT-B3LYP/6-311++G(d,p). In addition, in order to provide contrasts to the B-neo-CP tautomers, a series of twelve benzoporphyrin (BP) tautomers and twelve benzocarbaporphyrins (BCPs) were also analyzed, and two N-confused porphyrin (NCP) tautomer...

The armaticity of 5 methylcytosine tautomers in the gas phase has been studied and the chemical structures of related tautomers are investigated . The electronic energy, enthalpy and free energy of each tautomer are also estimated at the B3LYP/6-31 G* // B3LYP/6-31 G* and MP2 / 6-31 G* // MP2 / 6-31 G* Levels

This paper is a density functional theory (DFT) calculation of intramolecular proton transfer (IPT) in 6-hydroxypicolinic acid (6HPA, 6-hydroxypyridine-2-carboxylic acid) tautomeric forms. The transition state for the enol-to-keto transition is reported in the gas phase and in four different solvents. The planar and non-planar dimer forms of 6HPA keto and enol, respectively, were also studied i...

Schiff bases derived from hydroxyl naphthaldehydes and o-substituted anilines have been prepared and their tautomerism assessed by spectroscopic, crystallographic, and computational methods. Tautomeric equilibria have also been studied and reveal in most cases a slight preference of imine tautomers in solution; a fact supported by DFT calculations in the gas phase as well as incorporating solve...

The 2-carbene tautomer of pyridine (I), azacyclohexanetriene2-ylidene (II), was first proposed by Hammick1 70 years ago to explain the facile decarboxylation of 2-picolinic acid. Recent theoretical calculations2 have shown that II has energy about 4550 kcal‚mol-1 higher than I and that the transition state for the I to II rearrangement lies ca. 85 kcal‚mol-1 above I. Accordingly, the I to II ta...

Cystathionine beta-synthase (CBS) plays a central role in homocysteine metabolism, and malfunction of the enzyme leads to homocystinuria, a devastating metabolic disease. CBS contains a pyridoxal 5'-phosphate (PLP) cofactor which catalyzes the synthesis of cystathionine from homocysteine and serine. Mammalian forms of the enzyme also contain a heme group, which is not involved in catalysis. It ...

The title compound C(7)H(5)N(3)S(2), occurs as the thione tautomer in the solid state; the dihedral angle between the pyridine and thia-diazole ring planes is 2.08 (6)°. In the crystal, mol-ecules are linked by N-H⋯N hydrogen bonds, generating C(8) chains propagating in [010].