View in EDS

Pyrrolyl-Silicon Compounds as Precursors for Donor-Acceptor Systems Stabilized by Noncovalent Interactions.

Saved in:
Bibliographic Details
Title: Pyrrolyl-Silicon Compounds as Precursors for Donor-Acceptor Systems Stabilized by Noncovalent Interactions.
Authors: González-Santana, Susana1, Morera-Boado, Cercis1, Montero-Cabrera, Luis A.1, Trueba, Monica2 monica.trueba@unimi.it, Trasatti, Stefano P.2
Source: Journal of Physical Chemistry A. Jul2015, Vol. 119 Issue 27, p7038-7051. 14p.
Subjects: Silicon compounds, Chemical precursors, Chemical stability, Molecular interactions, Substituents (Chemistry), Chemical structure
Abstract: Pyrrolyl-silicon compounds were investigated by different theoretical approaches. Model monomers consisted of a pyrrole ring N-substituted with silylmethoxy and silylhydroxy end groups through a propyl chain spacer, designated as PySi and PySiOH. Geometrical, vibrational, and electronic properties, as well as chemical reactivity, are discussed and compared with pyrrole (Py) and N-propylpyrrole (N-PrPy) that were studied in parallel for reference purposes and methods validation. The electronic distribution between PySi and PySiOH differs importantly, the former being an electron donor, as Py and N-PrPy. Conversely, PySiOH presents donor-acceptor character with the LUMO energy level localized on the silanol end group. Global and local reactivity descriptors predict PySiOH more reactive than PySi with two preferential reactive sites: electron-rich Py ring and electron-deficient silanol group. On the basis of experimental studies, oligomers of PySiOH linked α-α′ via Py rings (α-α′PynSiOH, n = 2, 3) were considered as model molecules of hydrolyzed PySi. The most stable structures were derived from randomly generated α-α′PynSiOH that were optimized at semiempirical AM1 and refined with M05-2X/6-31G(d,p). Conformational analysis of dimer and trimer structures points to stability enhanced by molecular packing. Nonetheless, NBO and RDG results indicate that oligomer stability is dictated by the cooperative contribution of hydrogen bonding between silanol end groups and dispersive vdW interactions between silanol and the π system of the Py ring. The latter interaction resulting from electron delocalization induced by an electron-deficient silanol group seems to determine the smaller gap energy of T-shaped OH−π arrangements. The theoretical findings support the peculiar chemical behavior revealed by experiment. [ABSTRACT FROM AUTHOR]
Copyright of Journal of Physical Chemistry A is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
Description
Abstract:Pyrrolyl-silicon compounds were investigated by different theoretical approaches. Model monomers consisted of a pyrrole ring N-substituted with silylmethoxy and silylhydroxy end groups through a propyl chain spacer, designated as PySi and PySiOH. Geometrical, vibrational, and electronic properties, as well as chemical reactivity, are discussed and compared with pyrrole (Py) and N-propylpyrrole (N-PrPy) that were studied in parallel for reference purposes and methods validation. The electronic distribution between PySi and PySiOH differs importantly, the former being an electron donor, as Py and N-PrPy. Conversely, PySiOH presents donor-acceptor character with the LUMO energy level localized on the silanol end group. Global and local reactivity descriptors predict PySiOH more reactive than PySi with two preferential reactive sites: electron-rich Py ring and electron-deficient silanol group. On the basis of experimental studies, oligomers of PySiOH linked α-α′ via Py rings (α-α′PynSiOH, n = 2, 3) were considered as model molecules of hydrolyzed PySi. The most stable structures were derived from randomly generated α-α′PynSiOH that were optimized at semiempirical AM1 and refined with M05-2X/6-31G(d,p). Conformational analysis of dimer and trimer structures points to stability enhanced by molecular packing. Nonetheless, NBO and RDG results indicate that oligomer stability is dictated by the cooperative contribution of hydrogen bonding between silanol end groups and dispersive vdW interactions between silanol and the π system of the Py ring. The latter interaction resulting from electron delocalization induced by an electron-deficient silanol group seems to determine the smaller gap energy of T-shaped OH−π arrangements. The theoretical findings support the peculiar chemical behavior revealed by experiment. [ABSTRACT FROM AUTHOR]
ISSN:10895639
DOI:10.1021/acs.jpca.5b04167