Search

A new green procedure has been applied for the synthesis and purification of asymmetric monomethine cyanine dyes. The photophysical properties of the newly synthesized compounds have been examined by combined application of spectroscopic and theoretical methods. The structural characteristics of the molecules and dimer formation were characterized by quantum chemical computation and juxtaposed to the aggregachromism in UV/Vis spectra. The applicability of the dyes as fluorogenic nucleic acid probes has been proven by fluorescence titration, and their binding constants have been calculated. The mode of ligand–dsDNA/RNA interaction was rationalized by means of CD spectroscopy, molecular docking analysis, and fluorescent intercalator displacement experiments. [ABSTRACT FROM AUTHOR]

The potential of E–Z photoisomerization in molecular organic light-to-thermal conversion and storage in an E–styryl merocyanine system was studied in a polar acidic medium. A photoswitchable styryl merocyanine dye (E)-2-(2-(2-hydroxynaphthalen-1-yl)vinyl)-3,5-dimethylbenzo[d]thiazol-3-ium iodide was synthesized for the first time. The reversible E–Z photoisomerisation of the dye was investigated using UV-Vis spectroscopy and DFT calculations. E–Z isomerization was induced through the use of visible light irradiation (λ = 450 nm). The obtained experimental and theoretical results confirm the applicability of the Z and E isomers for proton-triggered light harvesting. [ABSTRACT FROM AUTHOR]

The reactivity of a series of N-arylacetamides, R--C(sub 6)H(sub 4)--NHCOCH(sub 3), with respect the alkaline hydrolysis reaction is studied. The electrostatic potential at the nuclei is recommended as an accurate local reactivity index.

The feasibility of molecular electrostatic potential measurements at atomic sites as reactivity descriptor for the mechanism of hydrogen bonding is evaluated for a range of complexes consisting of acetylene and diacetylene derivatives as proton donors and ammonia as an acceptor. A distinct linear relation between the molecular electrostatic potential with the energy of hydrogen-bond formation is observed.

Research has been conducted on the amide carbon-nitrogen bond. The role of the polar substituents in the internal rotation barrier around this bond has been investigated via the use of the density functional theory and the linear dependence between the rotation barriers and frequency shifts has been discovered.

We find high multireference character for abstraction of H from the OH group of ethenol (also called vinyl alcohol); therefore we adopt a multireference approach to calculate barrier heights for the various possible reaction channels of OH+C2H3OH. The relative barrier heights of ten possible saddle points for reaction of OH with ethenol are predicted by multireference Mo\ller–Plesset perturbation theory with active spaces based on correlated participating orbitals (CPOs) and CPO plus a correlated π orbital (CPO+π). Six barrier heights for abstracting H from a C[Single_Bond]H bond range from 3.1 to 7.7 kcal/mol, two barrier heights for abstracting H from an O[Single_Bond]H bond are both 6.0 kcal/mol, and two barrier heights for OH addition to the double bond are -1.8 and -2.8 kcal/mol. Thus we expect abstraction at high-temperature and addition at low temperature. The factor that determines which H is most favorable to abstract is an internal hydrogen bond that constitutes part of a six-membered ring at one of the abstraction saddle points; the hydrogen bond contributes about 3 kcal/mol stabilization. [ABSTRACT FROM AUTHOR]

A study was conducted to examine the kinetics of the aminolysis process for a series of seven parasubstituted phenyl acetate derivatives containing both electron-withdrawing and electron-donating groups. The electrostatic potentials observed at the carbon atom of the carbonyl reaction center provide insight into both the theoretical barrier heights and experimental rate constants.

Density functional theory (DFT) computations are carried out for a series of 15 monosubstituted benzene derivatives in order to study dependencies between electronic structure parameters and experimental reactivity constants. The results have emphasized the reliability of electrostatic potential values (EPN) as a local reactivity descriptor and have indicated that the relative values of the [sigma.sup.D] constants are predominantly determined by intramolecular influences.

The possible mechanistic pathways for the reaction of methyl benzoate with ammonia are examined by density functional and ab initio methods and transition state structures and energies are determined for concerted and neutral stepwise mechanisms. Theoretical results show that the two possible pathways have similar activation energies and predictions reveal that the catalytic process results in energy savings and a general-base-catalyzed neutral stepwise mechanism is favorable.

The variations of barrier heights for rotation around the amide C-N bond in para-substituted thioacetanilides was studied in a comparative context with data for a series of acetanilides by applying density functional theory. The results obtained were consistent with the views for a classical amide resonance as being the origin of higher rotational barriers in thioamides than in amides.

Research has been conducted on 2-benzoxazolinone. The authors have investigated the mechanisms of ring-opening reaction of this compound upon aminolysis with methylamine via the use of quantum mechanical methods, and have discussed the results.

Research has been conducted on ester aminolysis. The possible mechanistic pathways of ester aminolysis reaction have been investigated, and the results are reported.