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Through‐Space Spin–Spin Coupling in van der Waals Dimers and CH/π Interacting Systems. An Ab Initio and DFT Study
Author(s) -
Bagno Alessandro,
Saielli Giacomo,
Scorrano Gianfranco
Publication year - 2002
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 - 10.1002/1521-3765(20020503)8:9<2047::aid-chem2047>3.0.co;2-z
Subject(s) - van der waals force , chemistry , ab initio , spin (aerodynamics) , intermolecular force , van der waals strain , fermi contact interaction , molecular physics , atomic physics , computational chemistry , physics , van der waals radius , molecule , hyperfine structure , organic chemistry , thermodynamics
The through‐space J HH and J CH spin–spin coupling constants of model van der Waals dimers (involving methane, ethylene, and benzene), and of selected compounds showing the CH/π interaction, have been investigated by means of DFT and ab initio calculations. In the range of intermolecular separations for which the interaction is stabilizing, weak couplings (0.1–0.3 Hz) are predicted for J CH , while the corresponding J HH couplings are much smaller. The relative contributions (Fermi‐contact, spin–orbit, and spin–dipole) are strongly dependent on the geometry of the dimers and on the distance; the non‐negligible values of J CH for π systems stem largely from an incomplete cancellation of spin–orbit terms. The results obtained for the larger molecules, that is, acetonitrile@calix[4]arene 5 , the imine 6 , and the aryl ester 7 are consistent with those on the model dimers. For 7 , the occurrence of a through‐space mechanism for the transmission of coupling is established by examining trends in the magnitude of couplings as a function of the number of intervening covalent bonds.