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Why are the Elemental Nonmetals (F 2 , Cl 2 , Br 2 , I 2 , S 8 , P 4 ) of so Many Hues or of Any Hues and Where is the Chromophore? Insight into Intera ‐X–X Bonds
Author(s) -
Jabeen Shakeela,
Greer Alexander,
Edwards Kathleen F.,
Liebman Joel F.
Publication year - 2020
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.13270
Subject(s) - homo/lumo , halogen , ionization energy , chemistry , electron affinity (data page) , chromophore , electron , ionization , crystallography , lone pair , analytical chemistry (journal) , photochemistry , physics , molecule , ion , alkyl , organic chemistry , quantum mechanics , chromatography
Abstract A unique approach is used to relate the HOMO‐LUMO energy difference to the difference between the ionization potential (IP) and electron affinity (EA) to assist in deducing not only the colors, but also chromophores in elemental nonmetals. Our analysis focuses on compounds with lone pair electrons and σ electrons, namely X 2 (X = F, Cl, Br, I), S 8 and P 4 . For the dihalogens, the [IP – EA] energies are found to be: F 2 (12.58 eV), Cl 2 (8.98 eV), Br 2 (7.90 eV), I 2 (6.78 eV). We suggest that the intera halogen X–X bond itself is the chromophore for these dihalogens, in which the light absorbed by the F 2 , Cl 2 , Br 2 , I 2 leads to longer wavelengths in the visible by a π → σ* transition. Trace impurities are a likely case of cyclic S 8 which contains amounts of selenium leading to a yellow color, where the [IP – EA] energy of S 8 is found to be 7.02 eV. Elemental P 4 with an [IP – EA] energy of 9.09 eV contains a tetrahedral and σ aromatic structure. In future work, refinement of the analysis will be required for compounds with π electrons and σ electrons, such as polycyclic aromatic hydrocarbons (PAHs).