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How Does a Container Affect Acidity of its Content: Charge‐Depletion Bonding Inside Fullerenes
Author(s) -
Jaroš Adam,
Badri Zahra,
Bora Pankaj Lochan,
Bonab Esmaeil Farajpour,
Marek Radek,
Straka Michal,
ForoutanNejad Cina
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201706017
Subject(s) - fullerene , hydrogen bond , chemistry , lone pair , crystallography , molecule , cage , computational chemistry , chemical physics , organic chemistry , mathematics , combinatorics
A recent study ( Sci. Adv . 2017 , 3 , e1602833) has shown that FH ⋅⋅⋅ OH 2 hydrogen bond in a HF ⋅ H 2 O pair substantially shortens, and the H−F bond elongates upon encapsulation of the cluster in C 70 fullerene. This has been attributed to compression of the HF ⋅ H 2 O pair inside the cavity of C 70 . Herein, we present theoretical evidence that the effect is not caused by a mere compression of the H 2 O ⋅ HF pair, but it is related to a strong lone‐pair–π (LP–π) bonding with the fullerene cage. To support this argument, a systematic electronic structure study of selected small molecules (HF, H 2 O, and NH 3 ) and their pairs enclosed in fullerene cages (C 60 , C 70 , and C 90 ) has been performed. Bonding analysis revealed unique LP–π cage interactions with a charge‐depletion character in the bonding region, unlike usual LP–π bonds. The LP–π cage interactions were found to be responsible for elongation of the H−F bond. Thus, the HF appears to be more acidic inside the cage. The shortening of the FH ⋅⋅⋅ OH 2 contact in (HF ⋅ H 2 O)@C 70 originates from an increased acidity of the HF inside the fullerenes. Such trends were also observed in other studied systems.