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Anion⋅⋅⋅Anion Attraction in Complexes of MCl 3 − (M=Zn, Cd, Hg) with CN −
Author(s) -
Wysokiński Rafał,
Zierkiewicz Wiktor,
Michalczyk Mariusz,
Scheiner Steve
Publication year - 2020
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.202000206
Subject(s) - chemistry , dimer , ion , crystallography , dissociation (chemistry) , intermolecular force , exothermic process , binding energy , atom (system on chip) , ab initio , ab initio quantum chemistry methods , aqueous solution , molecule , atomic physics , adsorption , physics , organic chemistry , computer science , embedded system
High‐level ab initio calculations show that the MCl 3 − anions comprising Group 2B M atoms Zn, Cd, and Hg form a stable complex with the CN − anion, despite the like charge of the two ions. The complexation occurs despite a negative π‐hole region above the M atom of MCl 3 − . The dimerization distorts the planar geometry of MCl 3 − into a pyramidal shape which reduces the negative potential above the M atom, facilitating a close approach of the two anions, with R(M⋅⋅⋅C)∼2 Å, and an overall attractive electrostatic attraction within the dimer. In the gas phase, this dimer is less stable than the pair of separated ions by some 30 kcal/mol. However, the dissociation must surmount an energy barrier of roughly 25 kcal/mol which occurs at an intermolecular distance of 4 Å. In aqueous solution, the dimerization process is exothermic and barrier‐free, with a binding energy in the 11–18 kcal/mol range.