F. Partal Ureña

A new insight into the vibrational analysis of pyridine

A new proposal of vibrational assignment for pyridine is reported. Infrared spectra for the liquid and gas phases as well as Raman spectra for the liquid have been recorded and analyzed for -d(0), -d(5) and, for the first time to our knowledge, for 15N isotopomers as well. The proposal of assignment has been assessed by the calculation of a number of force fields, theoretical (ab initio, density functional theory) approaches as well as by a set of simple valence internal coordinates force constants transferred from benzene using the pure vibrational force field approximation. In all cases, the root mean square (rms) for the wavenumbers turn out to be lower than the best obtained so far, i.e. 6.6 cm(-1), as stated by Wiberg et al.

ASTROPHYSICAL MOLECULES AlD AND CaH: TRANSITION PROBABILITIES AND DISSOCIATION ENERGY

The Franck-Condon (FC) factors and r-centroids for the bands systemC1Σ+→ X1Σ+ of AlD and E2Π → X2Σ+ of CaH have been evaluated by means of a reliable numerical integration procedure by using a suitable potential. The dissociation energy, De, for the electronic ground states of AlD and CaH have been estimated by the curve fitting method to the RKRV experimental potential curve turning out to be 3.01 eV and 2.32 eV, respectively.

Vibrational Analysis of the in-Plane Normal Modes of the S — Tetrazine Molecule

In this work we propose to study the transferability of the force constants for a molecular serie which present the same bond groups, by using the pure vibrational form [1, 2]. The study of this transferability has special interest into a chemical family, in particular organics chemicals. So, on this ocassion. we have chosen the azabenzenes family, whose more representative members are: We have chosen this family due to they constituent structural bases of several important biological compounds such as, for example, nucleotides thymine and cytosine are substituted pyridines. Several reverse transcriptase inhibitors, use against the AIDS virus, have pyridine (Nevirapine) or pyrimidine (AZT). Fused rings of them are present into compounds of great importance in the life. like B12 and B2 vitamines. etc.