Chemical bonding in Period 2 homonuclear diatomic molecules: a comprehensive relook

Das, A and Arunan, E (2019) Chemical bonding in Period 2 homonuclear diatomic molecules: a comprehensive relook. In: JOURNAL OF CHEMICAL SCIENCES, 131 (12, SI).

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Abstract

Theoretical and experimental studies of bonding in the main group homonuclear diatomic molecules have been pursued for many years, and they possess serious challenges for scientists. Most of the early experimental work have been carried out by Herzberg.1,2 We take a relook at the bonding motifs of Period 2 homonuclear diatomic molecules (from Li-2 to Ne-2) using varieties of quantum chemical tools, commonly used for intermolecular bonding/interactions now. The methods employed include Atoms in Molecules (AIM), Non-covalent Index plot (NCI), Electrostatic potential (ESP), and Potential Acting on one Electron in a Molecule (PAEM). The spectroscopic constants i.e., equilibrium bond distances (r(e)), harmonic frequencies (omega), bond dissociation energies (D-e) have all been evaluated using high-level ab initio methods and critically compared with the experimental results. Multi-reference calculations (CASSCF) on B-2 and C-2 have been carried out as they have a large number of low lying electronic states. Bonding within these homonuclear diatomic molecules show all the diversities that are encountered in inter/intra-molecular bonding in chemistry. Based on the AIM analysis, these 8 homonuclear diatomic molecules could be divided into three different groups, based on the correlation between binding energy and the electron density at the bond critical point. However, PAEM/ESP analysis allows us to analyse all eight of them as one group having a good correlation between binding energy and the PAEM/ESP at the critical point between the two atoms. Our results highlight the arbitrariness in relying on some computational tools to characterize a bond as covalent (shared) or ionic/electrostatic (closed). In contrast, they also show the usefulness of the various methods in exploring similarities and differences in bonding. We propose that from Li-2 to Ne-2, all homonuclear diatomic molecules are bound by `chemical bonds'.

Item Type:	Journal Article
Publication:	JOURNAL OF CHEMICAL SCIENCES
Publisher:	INDIAN ACAD SCIENCES
Additional Information:	Copyright of this article belongs to INDIAN ACAD SCIENCES, C V RAMAN AVENUE, SADASHIVANAGAR, P B #8005, BANGALORE 560 080, INDIA
Keywords:	Covalency; Iconicity; van der Waals interaction; Atoms in molecules; electrostatic potential
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	07 Jan 2020 11:41
Last Modified:	07 Jan 2020 11:41
URI:	http://eprints.iisc.ac.in/id/eprint/64298

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