Journal of Molecular Structure 1265 (2022) 133232 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstr Unexplored σ -hole and π -hole interactions in (X 2 CY) 2 complexes (X = F, Cl; Y = O, S) Mahmoud A.A. Ibrahim a,∗ , Rehab R.A. Saeed a , Mohammed N.I. Shehata a , Esraa E.B. Mohamed a , Mahmoud E.S. Soliman b , Jabir H. Al-Fahemi c , H.R. Abd El-Mageed d , Muhammad Naeem Ahmed e , Ahmed M. Shawky f , Nayra A.M. Moussa a a Computational Chemistry Laboratory, Chemistry Department, Faculty of Science, Minia University, Minia 61519, Egypt b Molecular Bio-Computation and Drug Design Research Group, School of Health Sciences, University of KwaZulu-Natal, Durban, Westville 4000, South Africa c Chemistry Department, Faculty of Applied Sciences, Umm Al-Qura University, Makkah 21955, Saudi Arabia d Micro-Analysis, Environmental Research and Community Affairs Center (MAESC), Faculty of Science, Beni-Suef University, Beni-Suef 62511, Egypt e Department of Chemistry, The University of Azad Jammu and Kashmir, Muzaffarabad 13100, Pakistan f Science and Technology Unit (STU), Umm Al-Qura University, Makkah 21955, Saudi Arabia a r t i c l e i n f o Article history: Received 26 June 2021 Revised 28 December 2021 Accepted 4 May 2022 Available online 5 May 2022 Keywords: σ -hole π -hole Halogen bond Chalcogen bond Tetrel bond SAPT-EDA a b s t r a c t The potentiality of the X 2 CY molecules (X = F, Cl; Y = O, S) to engage in σ -hole···σ -hole, di-σ -hole, σ -hole···π -hole, and π -hole···π -hole interactions was assessed. In that spirit, potential energy surface (PES) scan was devoted to thoroughly characterize the features of the (X 2 CY) 2 complexes within a series of configurations, including halogen···halogen, halogen···chalcogen, chalcogen···chalcogen, halogen···tetrel, chalcogen···tetrel, and tetrel···tetrel. In most instances, the strength of the inspected interactions de- clined according to the order: tetrel···tetrel (staggered) > tetrel···tetrel (eclipsed) > chalcogen···tetrel > halogen···tetrel > chalcogen···chalcogen > halogen···chalcogen > halogen···halogen configurations. The strength of the explored complexes within tetrel···tetrel configurations was found to be dominated fur- ther by the contributions of the three planar substituents rather than those of the π -hole center. Bench- marking of the binding energies emphasized an approximate similarity between the resulted energetic features that were evaluated at the MP2/aug-cc-pVTZ and CCSD/CBS levels of theory. Quantum theory of atoms in molecules (QTAIM) critically unveiled the closed-shell nature of the halogen-, chalcogen-, and tetrel-bonding interactions within the adopted configurations. Symmetry-adapted perturbation theory- based energy decomposition analysis (SAPT-EDA) demonstrated the domination of the σ -hole interactions by the dispersion forces (E disp ). In addition to the dominant E disp , preferential contributions of the elec- trostatic (E elst ) and induction (E ind ) forces were detected for the π -hole bonded complexes within all the scouted configurations. The emerging findings from the current work would be a fruitful underpinning for the forthcoming studies in materials science and crystal engineering. © 2022 Elsevier B.V. All rights reserved. 1. Introduction In recent years, the “like attracting like” phenomenon has been increasingly accentuated within the umbrella of noncovalent inter- actions as having important applications in a number of versatile areas pertinent to materials and crystal design [1–4]. As a point of departure, the di-hydrogen bonds were crucially unveiled be- tween two hydrogen atoms, in which an acidic hydrogen atom in proton donor was disposed to interact with an alkaline hydrogen atom in electron donor [5,6]. Further understanding of the vari- ∗ Corresponding author. E-mail address: m.ibrahim@compchem.net (M.A.A. Ibrahim). ant interactions between similar species was also conducted within anion···anion and cation···cation bonded complexes [7,8]. Within parallel brain areas, a great interest has been dedi- cated towards the so-called σ -hole interactions between similar molecules [9–12]. The σ -hole concept was announced to describe an electron-depletion region that occurred on the molecular sur- face along the extension of a covalently bonded group IV-VII ele- ment in the periodic table [13–16]. As earlier reported, group IV- VII elements were explored with a protrusive penchant to interact with Lewis bases attractively, giving tetrel [17,18], pnicogen [19– 21], chalcogen [22–25], and halogen [26–28] bonds, respectively. Basically, the study of σ -hole···σ -hole and di-σ -hole interactions of the covalently bonded halogen atoms elucidated a subtle under- standing of the nature and significance of these interactions [29]. https://doi.org/10.1016/j.molstruc.2022.133232 0022-2860/© 2022 Elsevier B.V. All rights reserved.