Premium
Proton in a Confined Space: Structural Studies of H + ⊂Crypt‐111 Iodide and Some Halogen‐Bonded Derivatives
Author(s) -
Kumar Vijith,
Pilati Tullio,
Quici Silvio,
Chierotti Michele R.,
Nervi Carlo,
Gobetto Roberto,
Resnati Giuseppe
Publication year - 2017
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.201701699
Subject(s) - halogen , intramolecular force , crystallography , proton , chemistry , iodide , covalent bond , hydrogen bond , hydrogen , materials science , molecule , stereochemistry , inorganic chemistry , organic chemistry , physics , alkyl , quantum mechanics
Experimental observations and modeling data are reported on the solid‐state structural features of crypt‐ 111⋅HI ( 1 ) and the three‐component co‐crystals that 1 forms with α,ω‐diiodoperfluoroalkanes 2 a – d . X‐ray analyses indicate that, in all five systems and at low temperature, the caged proton is covalently bonded to a single nitrogen atom and is involved in a network of intramolecular hydrogen bonds. In contrast, room‐temperature, solid‐state 15 N NMR spectroscopy suggests magnetic equivalency of the two N atoms of crypt‐111 in both 1 and co‐crystals of 1 with diiodoperfluoroalkanes. Computational modelling confirms that the acidic hydrogen inside the cavity preferentially sits along the internitrogen axis and is covalently bonded to one nitrogen. The computed energy barriers suggest that the hopping of the encapsulated proton between the two N atoms of the cage can occur in the halogen‐bonded co‐crystals of 1⋅2 , but it is hardly possible in the pure H + ⊂crypt‐111 iodide 1 . These different pictures of the proton position and dynamics obtained by using different techniques and conditions confirm the unique characteristics of the confined space within the cavity of crypr‐111 and the distinctive features of processes occurring therein.