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Titolo:
AB-INITIO SCF-MO CALCULATIONS ON TRIAZA AND TETRAAZA CYCLIC AMINES
Autore:
RIBEIROCLARO PJA; AMADO AM; MARQUES MPM; TEIXEIRADIAS JJC;
Indirizzi:
UNIV COIMBRA,DEPT QUIM,UNIDADE I&D QUIM FIS MOL P-3049 COIMBRA PORTUGAL UNIV COIMBRA,DEPT BIOQUIM P-3049 COIMBRA PORTUGAL
Titolo Testata:
Perkin transactions. 2
fascicolo: 6, , anno: 1996,
pagine: 1161 - 1167
SICI:
0300-9580(1996):6<1161:ASCOTA>2.0.ZU;2-1
Fonte:
ISI
Lingua:
ENG
Soggetto:
NUCLEAR MAGNETIC-RESONANCE; EFFECTIVE POTENTIALS; METAL-COMPLEXES; BASIS-SETS; PROTONATION; NICKEL(II); COPPER(II); TRIAMINES; ZINC(II); ABINITIO;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
26
Recensione:
Indirizzi per estratti:
Citazione:
P.J.A. Ribeiroclaro et al., "AB-INITIO SCF-MO CALCULATIONS ON TRIAZA AND TETRAAZA CYCLIC AMINES", Perkin transactions. 2, (6), 1996, pp. 1161-1167

Abstract

Molecular orbital ab initio calculations have been performed on some triaza and tetraaza cyclic amines aiming at the determination of theirminimum energy geometries and of the relative conformational energiesin different protonation states. The results clearly show two factorsgoverning the conformational preferences in these systems: the formation of intramolecular hydrogen bonds and the repulsions between two nitrogen protons or two nitrogen lone pairs. For each protonation state there are distinct conformers depending on the number of NH bonds pointing 'inwards' relative to the macrocyclic cavity and on their abilityto form intramolecular hydrogen bonds. All the systems display a marked preference for a helical geometry, with the ethylenediamine bridgesin a gauche conformation. The triaza systems having propylenediamine bridges display an additional conformational freedom due to the large number of configurations available for these bridges. The calculated structures and energies are in good agreement with the experimental X-ray and NMR spectroscopy data available.

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Documento generato il 12/07/20 alle ore 03:23:28