Open AccessHeavy-Atom Tunneling in the Covalent/Dative Bond Complexation of Cyclo[18]carbon–Piperidine
Author(s) -
Ashim Nandi,
Jan M. L. Martin
Publication year - 2022
Publication title -
the journal of physical chemistry. b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 392
eISSN - 1520-6106
pISSN - 1520-5207
DOI - 10.1021/acs.jpcb.2c00218
Subject(s) - piperidine , chemistry , covalent bond , van der waals force , adduct , atom (system on chip) , quantum tunnelling , computational chemistry , stereochemistry , molecule , physics , quantum mechanics , organic chemistry , computer science , embedded system
Recent quantum chemical computations demonstrated the electron-acceptance behavior of this highly reactive cyclo[18]carbon (C 18 ) ring with piperidine (pip). The C 18 -pip complexation exhibited a double-well potential along the N-C reaction coordinate, forming a van der Waals (vdW) adduct and a more stable, strong covalent/dative bond (DB) complex by overcoming a low activation barrier. By means of direct dynamical computations using canonical variational transition state theory (CVT), including the small-curvature tunneling (SCT), we show the conspicuous role of heavy atom quantum mechanical tunneling (QMT) in the transformation of vdW to DB complex in the solvent phase near absolute zero. Below 50 K, the reaction is entirely driven by QMT, while at 30 K, the QMT rate is too rapid ( k T ∼ 0.02 s -1 ), corresponding to a half-life time of 38 s, indicating that the vdW adduct will have a fleeting existence. We also explored the QMT rates of other cyclo[ n ]carbon-pip systems. This study sheds light on the decisive role of QMT in the covalent/DB formation of the C 18 -pip complex at cryogenic temperatures.