| Autor: |
Merino-García MDR; Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Carretera Toluca-Atlacomulco, km. 14.5, Toluca, Estado de México C.P. 50200, México., Soriano-Agueda LA; Universidad Nacional Autónoma de México, Instituto de Química, Ciudad Universitaria, Circuito Exterior s/n, Ciudad de México 04510, México., Guzmán-Hernández JD; Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Carretera Toluca-Atlacomulco, km. 14.5, Toluca, Estado de México C.P. 50200, México., Martínez-Otero D; Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Carretera Toluca-Atlacomulco, km. 14.5, Toluca, Estado de México C.P. 50200, México.; Universidad Nacional Autónoma de México, Instituto de Química, Ciudad Universitaria, Circuito Exterior s/n, Ciudad de México 04510, México., Landeros Rivera B; CNRS, Laboratoire de Chimie Théorique, LCT, Sorbonne Université, Paris 75005, France., Cortés-Guzmán F; Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Carretera Toluca-Atlacomulco, km. 14.5, Toluca, Estado de México C.P. 50200, México.; Universidad Nacional Autónoma de México, Instituto de Química, Ciudad Universitaria, Circuito Exterior s/n, Ciudad de México 04510, México., Barquera-Lozada JE; Universidad Nacional Autónoma de México, Instituto de Química, Ciudad Universitaria, Circuito Exterior s/n, Ciudad de México 04510, México., Jancik V; Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Carretera Toluca-Atlacomulco, km. 14.5, Toluca, Estado de México C.P. 50200, México.; Universidad Nacional Autónoma de México, Instituto de Química, Ciudad Universitaria, Circuito Exterior s/n, Ciudad de México 04510, México. |
| Abstrakt: |
Although benzene and borazine are isoelectronic and isostructural, they have very different electronic structures, mainly due to the polar nature of the B-N bond. Herein, we present an experimental study of the charge density distribution obtained from the multipole model formalism and Hirshfeld atom refinement (HAR) based on high-resolution X-ray diffraction data of borazine B 3 N 3 H 6 ( 1 ) and B , B ', B ″-trichloroborazine ( 2 ) crystals. These data are compared to those obtained from HAR for benzene ( 4 ) and 1,3,5-trichlorobenzene ( 5 ) and further compared with values obtained from density functional theory calculations in the gas phase, where N , N ', N ″-trichloroborazine ( 3 ) was also included. The results confirm that, unlike benzene, borazines are only weakly aromatic with an island-like electronic delocalization within the B 3 N 3 ring involving only the nitrogen atoms. Furthermore, delocalization indices and interacting quantum atom energy for bonded and non-bonded atoms were found to be highly suitable indicators capable of describing the origin of the discrepancies observed when the degree of aromaticity in 2 and 3 is evaluated using common aromaticity indices. Additionally, analysis of intermolecular interactions in the crystals brings further evidence of a weakly aromatic character of the borazines as it reveals surprising similarities between the crystal packing of borazine and benzene and also between B , B ', B ″-trichloroborazine and 1,3,5-trichlorobenzene. |
