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Orientation Dependence of Electron Spin Phase Memory Relaxation Times in Copper(II) and Vanadyl Complexes in Frozen Solution
Author(s) -
Du JingLong,
More Kundalika M.,
Eaton Sandra S.,
Eaton Gareth R.
Publication year - 1992
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.199200041
Subject(s) - chemistry , electron paramagnetic resonance , relaxation (psychology) , orientation (vector space) , magnetic field , copper , electron , spin (aerodynamics) , condensed matter physics , field (mathematics) , phase (matter) , crystallography , nuclear magnetic resonance , molecular physics , analytical chemistry (journal) , physics , thermodynamics , geometry , psychology , social psychology , mathematics , organic chemistry , quantum mechanics , chromatography , pure mathematics
The orientation dependence of the electron spin phase memory relaxation time (T ) was measured for vanadyl 5‐(4‐carboxyphenyl)‐10, 15, 20‐tritolylporphyrin at 22, 50, and 100 K, copper(II) bis(diethyldithiocarbamate) at 50 and 100 K, and copper(II) 5, 10, 15, 20‐tetratolylporphyrin at 50, 70, and 100 K in frozen solution. T m was determined by fitting a single exponential to two‐pulse electron spin echo data. The values of T m were strongly dependent on the orientation of the molecule in the magnetic field. Longer values were obtained when the magnetic field was along a principal axis or along a non‐canonical turning point in the spectrum. Shorter values of T m were observed at intermediate orientations. The orientation dependence of T m is attributed to molecular motion. The EPR spectra for the three systems examined are approximately axial, so the relevant motion is motion of the molecular z axis with respect to the external magnetic field. Longer values of T m (slower relaxation) occur for orientations at which the resonant condition is less sensitive to a change in orientation of the molecular z axis. Shorter values of T m (faster relaxation) occur at orientations for which the resonant condition is more sensitive to a change in orientation of the molecular z axis.