The stereochemistry of hydrazides makes them especially interesting as building blocks for molecular design. An exhaustive conformational analysis of three model hydrazides was conducted in a conformer-selective approach by using a combination of high-level quantum chemistry calculations and vibrational spectroscopy in the gas phase and in solution. The NH stretch frequency was found to be high...

Many natural products of biological interest contain [6,5]- and [6,6]-spiroketal moieties that can adopt various configurations, benefiting or not from anomeric conformation stabilizing effects. The spiroketal fragments are often important for the biological activity of the compounds containing them. Most stable spiroketal stereoisomers, including those benefiting from conformational anomeric e...

The low frequency vibrations of the ethylamino backbone of six conformers of tryptamine have been studied in the ground and excited states using dispersed fluorescence spectroscopy, rotationally resolved laser induced fluorescence, and ab initio calculations. Four low frequency vibrational modes of the backbone, which involve torsional and librational motions of the ethylamino group, have been ...

Quantum dynamical simulations of vibrational spectroscopy have been carried out for glycine dipeptide (CH(3)-CO-NH-CH(2)-CO-NH-CH(3)). Conformational structure and dynamics are modeled in terms of the two Ramachandran dihedral angles of the molecular backbone. Potential energy surfaces and harmonic frequencies are obtained from electronic structure calculations at the density functional theory ...

the nitrite ® nitro isomerization in nitritopentaamine cobalt (iii) halides has been known. in this paper, the effect of the size of the counter ions (noncoordinated groups) on the rate of isomerization in nitritopentaamine cobalt (iii) halides, is reported. the rate of isomerization is decreased by increasing the size of the counter ions. this decrease is explained on the basis of steric inter...

In recent years, fluorescent supramolecular materials have received significant attention due to their wide application prospects. However, the relationship between conformation of supramolecules and photophysical properties remains an open question. this study, two rhomboidal metallacycle isomers, SA SB, self-assembled with trans- cis-isomers tetraphenylethylene-based ditopic pyridyl ligands (...

The 5-hydroxytryptamine receptors (5HTn) are optimized for 5-hydrotryptamine molecules, resulting in a significantly enhanced psychoactive response compared with the 4-, 6-, 7-isomers. This is despite their relatively similar energetic stabilities, excited state lifetimes and emission characteristics. In this work we investigate the conformational space of serotonin (5-hydroxytryptamine) using ...

Ionization of equatorial and axial conformational isomers of the chair-bromocyclohexane is investigated with use of the vacuum ultraviolet mass-analyzed threshold ionization (MATI) spectroscopic technique. Two distinct ionization energies of 9.8308 ± 0.0025 and 9.8409 ± 0.0025 eV are determined for equatorial or axial conformers, respectively. From the conformer-selective vibrational analysis, ...