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Hyperfine Interactions in the Lowest Triplet State of Pyridine
Author(s) -
Groenen E.J.J.,
Buma W.J.,
Schmidt J.
Publication year - 1989
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198900014
Subject(s) - chemistry , hyperfine structure , triplet state , electron paramagnetic resonance , pyridine , lone pair , molecule , deuterium , atomic physics , atom (system on chip) , molecular orbital , crystal (programming language) , ground state , crystallography , nuclear magnetic resonance , physics , organic chemistry , medicinal chemistry , computer science , programming language , embedded system
Results are reported of nitrogen and deuterium hyperfine studies of the triplet state of pyridine‐d 5 as a guest in a single crystal of benzene at 1.2 K. Through the use of electron spin echo (ESE) techniques complete hyperfine tensors have been obtained: for nitrogen from the ESE detected EPR spectra and for the para‐deuterium atom from the modulations of the ESE envelope. These tensors unambiguously show that the molecule is no longer planar in the lowest triplet state T 0 . Pyridine's structure considerably changes upon excitation, but the mirror plane perpendicular to the molecule is preserved. Experimental and theoretical evidence is presented for the fact that this deformation is an intrinsic property of T 0 and is not induced by the crystal field. About fourty percent of the triplet electron spin density is found to be localised in the π‐orbital of nitrogen, about ten percent in the lone pair orbital of nitrogen and somewhat more than thirty percent in the π‐orbital of the para‐carbon atom.