Theoretical studies of hydrogen-bonded complexes using semiempirical methods

COMPLEJOS

HIDROGENO

BIBLIOGRAFIA NACIONAL QUIMICA

URUGUAY

1990

Recently proposed modified MNDO methods (MNDO/M and MNDO-PM3) for the study of hydrogen-bonded complexes are tested in four simple systems: (H2O)2, NH4+ · H2O, formamide water and formamide-methanol dimers. A comparison is made with AM1 since this method, intended to be a general improvement of MNDO, was already shown to fail in the former two dimers. Bifurcated hydrogen-bonded structures were always preferred over linear ones. AM1 also shows this artifact in the formamide-water dimer but not in the formamide-methanol one. This is due to the inability of -CH3 to bind to the carbonyl oxygen. In this case the AM1 optimized global minimum is in excellent agreement with the Hartree-Fock ab initio DZP optimized structure. Moreover, when it is physically impossible to form bifurcated hydrogen bonds, AM1 is in good agreement with ab initio results. MNDO/M and MNDO-PM3 (an improvement on AM1 ) do not give any bifurcated structure either in the former two dimers or in the formamide complexes. MNDO/M and MNDO-PM3 structures are in agreement with ab initio and experimental ones in almost all cases, except for the global minima in both the formamide-water and the formamide- methanol dimers. Singly hydrogen-bonded structures are predicted instead of the experimentally determined and ab initio calculated correct doubly hydrogen-bonded ones. MNDO-PM3, although not entirely correct, gives structures which are more correct than the MNDO/M ones. In conclusion, neither of these semiempirical methods is entirely correct. Overall, MNDO-PM3 seems to be more trustworthy than AM1 or MNDO/M, although these methods may be used when no bifurcated hydrogen bonds (AM1) or cycles (MNDO//M) exist. Failures of MNDO-PM3 indicate that a better semiempirical method is still needed for studies of solvation and hydrogen- bonded clusters.

Journal of Molecular Structure (THEOCHEM) v. 69, 1990. p. 405-426

Elsevier

1992

Información sobre Derechos de Autor

(Por favor lea este aviso antes de abrir los documentos u objetos)

La legislación uruguaya protege el derecho de autor sobre toda creación literaria, científica o artística, tanto en lo que tiene que ver con sus derechos morales, como en lo referente a los derechos patrimoniales con sujeción a lo establecido por el derecho común y las siguientes leyes (LEY 9.739 DE 17 DE DICIEMBRE DE 1937 SOBRE PROPIEDAD LITERARIA Y ARTISTICA CON LAS MODIFICACIONES INTRODUCIDAS POR LA LEY DE DERECHO DE AUTOR Y DERECHOS CONEXOS No. 17.616 DE 10 DE ENERO DE 2003, LEY 17.805 DE 26 DE AGOSTO DE 2004, LEY 18.046 DE 24 DE OCTUBRE DE 2006 LEY 18.046 DE 24 DE OCTUBRE DE 2006)

ADVERTENCIA - La consulta de este documento queda condicionada a la aceptación de las siguientes condiciones de uso: Este documento es únicamente para usos privados enmarcados en actividades de investigación y docencia. No se autoriza su reproducción con fines de lucro. Esta reserva de derechos afecta tanto los datos del documento como a sus contenidos. En la utilización o cita de partes debe indicarse el nombre de la persona autora.

PDF

Inglés

Artículo

DOI:10.1016/0166-1280(90)80065-V

PDF