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Carbon‐13 spin–lattice relaxation times as a probe for the study of electron donor–acceptor complexes
Author(s) -
Blackburn Barry J.,
Friesen Kenneth J.
Publication year - 1977
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270090213
Subject(s) - chemistry , acceptor , electron , relaxation (psychology) , lattice (music) , lattice constant , electron donor , electron acceptor , viscosity , electron paramagnetic resonance , analytical chemistry (journal) , thermodynamics , condensed matter physics , nuclear magnetic resonance , physics , organic chemistry , quantum mechanics , psychology , social psychology , acoustics , diffraction , catalysis
13 C spin–lattice relaxation times ( T 1 's) are reported for C‐3 of 2‐methylindole (methyl,3‐ 13 C 2 ) as a function of the concentration of added 1,3,5‐trinitrobenzene at 35°C in 1,2‐dichloroethane. The observed decreases in T 1 , with increasing concentrations of 1,3,5‐trinitrobenzene, are interpreted in terms of longer time‐averaged correlation times which result from (a) the formation of increasing amounts of electron donor–acceptor complex and (b) increases in viscosity. An equation is derived which makes it possible to obtain estimates of the equilibrium constant for complex formation, and the spin–lattice relaxation time of the complex, from the observed T 1 's and viscosity measurements. From the data obtained, values of 6.4 × 10 −12 and 14.1 × 10 −12 s rad −1 were calculated for the effective correlation times (at 35°C and 0.686 centipoise) and 0.21 and 0.28 nm for the effective radii of free and complexed donor respectively.