Unconventional Radical and Radical-Hole Site-Based Interactions in Halogen-Bearing Dimers and Trimers: A Comparative Study

Mahmoud A A Ibrahim; Heba S M Abd Elhafez; Mohammed N I Shehata; Nayra A M Moussa; Shaban R M Sayed; Mahmoud E S Soliman; Muhammad Naeem Ahmed; Mohamed Khaled Abd El-Rahman; Tamer Shoeib

doi:10.1021/acsomega.4c04620

Unconventional Radical and Radical-Hole Site-Based Interactions in Halogen-Bearing Dimers and Trimers: A Comparative Study

ACS Omega. 2024 Sep 5;9(37):38743-38752. doi: 10.1021/acsomega.4c04620. eCollection 2024 Sep 17.

Authors

Affiliations

¹ Computational Chemistry Laboratory, Chemistry Department, Faculty of Science, Minia University, Minia 61519, Egypt.
² School of Health Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4000, South Africa.
³ Basic and Clinical Medical Science Department, Faculty of Dentistry, Deraya University, New Minya 61768, Egypt.
⁴ Department of Botany and Microbiology, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
⁵ Molecular Bio-Computation and Drug Design Research Laboratory, School of Health Sciences, University of KwaZulu-Natal, Westville Campus, Durban 4000, South Africa.
⁶ Department of Chemistry, The University of Azad Jammu and Kashmir, Muzaffarabad 13100, Pakistan.
⁷ Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States.
⁸ Department of Chemistry, The American University in Cairo, New Cairo 11835, Egypt.

Abstract

Radical (R^•) and R^•-hole site-based interactions are comparatively studied, for the first time, using ab initio methods. In this regard, R^•-bearing molecules ^•XO₃ (where X = Cl, Br, and I) were subjected to direct interaction with NH₃ within dimeric and trimeric forms in the form of NH₃···^•XO₃/^•XO₃···NH₃ and NH₃···^•XO₃···NH₃ complexes, respectively. As confirmed by electrostatic potential analysis, the studied R^•-bearing molecules ^•XO₃ had the outstanding potentiality to interact as Lewis acid centers via two positive sites dubbed as R^• and R^•-hole sites. Such an observation proposed the potentiality of the considered ^•XO₃ molecules to engage in unconventional R^• and well-established R^•-hole site-based interactions with Lewis bases. This was confirmed by negative interaction (E _int) energies, ranging from -4.93 to -19.89 kcal/mol, with higher favorability for R^• site-based interactions over the R^•-hole site-based ones. MP2 energetic features furnished higher preferability for the R^• site-based interactions than the R^•-hole site-based ones in the case of chlorine- and bromine-bearing complexes, and the reverse was true for the iodine-bearing complexes. Moreover, elevated E _int values were recorded for the NH₃···^•XO₃···NH₃ trimers over the NH₃···^•XO₃ and ^•XO₃···NH₃ dimers, outlining the higher preference of the ^•XO₃ molecules to engage in R^• and R^•-hole site-based interactions in the trimeric form over the dimeric one. These results might be considered a requisite linchpin for numerous forthcoming supramolecular chemistry and crystal engineering studies.