What makes molecular iodine solid? Not London dispersion forces, but halogen bonds
Fan H. Vaganova T. Malykhin E. Benassi E.
5 February 2026Elsevier B.V.
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
2026#346
The nature of intermolecular interactions in iodine (I₂) crystals has long been a subject of interest, traditionally attributed to London dispersion (LD) forces. Herein, we systematically investigate I₂⋯I₂ interactions through quantum mechanical calculations combined with spectroscopic and theoretical analyses. Focusing on three I2⋯I2 dimers extracted from the crystal structure, the nature of these interactions was further clarified using electron localization function (ELF) analysis and topological atoms-in-molecules (AIM). The results confirm XB is dominated in dimer 1, the most stable dimer. Comparisons of experimental Raman spectra with calculated spectra for dimer 1 and crystal fragments revealed frequency splitting of I[sbnd]I stretching modes, directly linked to XB-induced weakening of specific I[sbnd]I bonds. Collectively, these results provide the first systematic evidence that the intrinsic intermolecular interaction in I₂ crystals is halogen bonding, rather than LD forces. This work redefines our understanding of iodines solid-state structure and the nature of the intermolecular interactions.
Halogen bonding , Intermolecular interactions , Molecular topology , Raman spectroscopy
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Department of Chemistry, School of Sciences and Humanities, Nazarbayev University, Qabanbay Batyr 53, Astana, 010000, Kazakhstan
Laboratory of Heterocyclic Compounds, N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, 9 Lavrentiev Avenue, Novosibirsk, 630090, Russian Federation
Infochemistry Scientific Center, ITMO University, Saint-Petersburg, 191002, Russian Federation
Department of Chemistry
Laboratory of Heterocyclic Compounds
Infochemistry Scientific Center
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Книга Публикация научной статьи Волощук 2026 Book Publication of a scientific article 2026