Post Hartree–Fock and DFT Studies on Pyrrole···Nitrogen and Pyrrole···Carbon Monoxide Molecules

Abstract

Abstract:The hydrogen bonded and van der Waals isomers of pyrrole···nitrogen and pyrrole···carbon monoxide have been studied using ab initio and density functional theory methods. Complex geometries and total energies of the isomers have been determined at HF, MP2, B3LYP and B3PW91 levels of theory employing 6-31G* basis set. For pyrrole···nitrogen complex, only two isomers have stable structure and the more stable one is found to be the hydrogen bonded isomer. Among the five isomers of pyrrole···carbon monoxide complex, the hydrogen bonded isomer is found to be the most stable form. The interaction energy for all these isomers have been calculated after eliminating the basis set superposition errors by using the full counterpoise correction method. Chemical hardness, chemical potential have been calculated and are used to study the stability of the molecules.

Self-Aggregation in Pyrrole: Matrix Isolation, Solid State Infrared Spectroscopy, and DFT Study

“…1 This widespread appearance of the pyrrole moiety among biological molecules is mainly due to both its facility to polymerize and capacity to form N-H‚‚‚π hydrogen bonds with neighboring molecules. [2][3][4][5][6][7] The gaseous phase of pyrrole has been studied long time ago by means of microwave spectroscopy 8, 9 and electron diffraction. 10 Very interestingly, Wilcox and Goldstein, the authors of the first microwave study on pyrrole (published in 1952), mainly addressed the question of whether the pyrrole molecule is completely coplanar or not (doubts existed at that time regarding the precise position of the hydrogen atom bonded to the nitrogen 11 ).…”

“…Monopyrrolic natural products include porphobilinogen, the precursor of all natural pyrrole pigments based on the porphyrin or corrin nuclei, and a number of antibiotics, including the tripyrrolic prodigiosins, which have an entirely different biosynthetic origin . This widespread appearance of the pyrrole moiety among biological molecules is mainly due to both its facility to polymerize and capacity to form N−H···π hydrogen bonds with neighboring molecules. − …”

Effect of GTP and GDP nucleotides on vinblastine binding affinity to tubulin: a DFT study

“…DFT is very appealing due to its excellent performance-to-cost ratio, and DFT methods are widely employed in the computational chemistry community [10,11]. Convergence in the self-consistent field (SCF) procedure was typically achieved using geometry optimisations, which used default convergence criteria [12].…”

Incremental NH stretching downshift through stepwise nitrogen complexation of pyrrole: a combined jet expansion and matrix isolation study

“…In any molecular nitrogen solvation environment, the simple aromatic pyrrole (C 4 H 4 NH) ring offers the possibility of competition between more directional NHÁ Á ÁN 2 hydrogen bonds and less directional aromatic pÁ Á ÁN 2 interactions. 11 The NH stretching vibration provides a sensitive indicator for complex formation even with the weakly interacting nitrogen binding partner. Observable effects such as spectroscopic shifts and infrared intensity enhancements are much less pronounced in most other fundamental modes of the symmetric pyrrole molecule and therefore more difficult to judge experimentally.…”