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Chalcogen–mercury bond formation and disruption in model Rabenstein's reactions: A computational analysis
Author(s) -
Madabeni Andrea,
Dalla Tiezza Marco,
Omage Folorunsho Bright,
Nogara Pablo Andrei,
Bortoli Marco,
Rocha João Batista Teixeira,
Orian Laura
Publication year - 2020
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.26371
Subject(s) - chemistry , chalcogen , ligand (biochemistry) , electrophile , mercury (programming language) , thiol , reactivity (psychology) , computational chemistry , reaction mechanism , kinetics , stereochemistry , catalysis , organic chemistry , biochemistry , medicine , physics , receptor , alternative medicine , pathology , quantum mechanics , computer science , programming language
Abstract Methylmercury is a highly toxic compound and human exposure is mainly related to consumption of polluted fish and seafood. The inactivation of thiol‐based enzymes, promoted by the strong affinity binding of electrophilic mercuric ions to thiol and selenol groups of proteins, is likely an important factor explaining its toxicity. A key role is played by the chemistry and reactivity of the mercury–chalcogens bond, particularly HgS and HgSe, which is the focus of this computational work (level of theory: (COSMO)‐ZORA‐BLYP‐D3(BJ)/TZ2P). We analyze nine ligand‐exchange model reactions (the so‐called Rabenstein's reactions) involving an entering ligand (methylchalcogenolate) and a substrate (methylchalcogenolatemethylmercury). Trends in reaction and activation energies are discussed and a change in mechanism is reported for all cases when going from gas phase to water, that is, from a single‐well potential energy surface (PES) to a canonical S N 2‐like mechanism. The reasons accounting for the biochemically challenging and desired displacement of methylmercury from a seleno/thiol protein can be found already in these model reactions, as can be seen from the similarities of the ligand exchange reactions in solution in thermodynamics and kinetics.