ESR and NMR study on the charge-transfer complexes of N-Ssalicylideneanilines containing NHO hydrogen bond as a dynamic function

Abstract

Summary form only given. N-Salicylideneaniline derivatives have intramolecular NHO hydrogen bond. We have found that the barrier height for the proton transfer in the NHO hydrogen bond of these compounds is relatively small in the crystalline state and the proton transfer is accompanied by a configurational change of the /spl pi/-electron system, showing thermochromism in some cases. Thus in the charge transfer complexes of these N-salicylideneaniline derivatives (NN, NPY and DNP shown in the figure) with TCNQ and with F/sub 4/-TCNQ, a dynamic interaction between the hydrogen bond and the electronic state of the mixed stacking column of donor and acceptors may be expected. The ESR line shape of (NPY)/sub 2//F/sub 4/-TCNQ and NN/(TCNQ)/sub 2/ was simple lorentzian near 20 K and the line width decreased remarkably as temperature increased up to 300 K. This behavior is similar to that of t-polyacetylene and suggests a motion of the spin. A deuteration of the hydrogen bond of NN/(TCNQ)/sub 2/ led to a reduction of ESR line width. Delocalization of the proton in the hydrogen bond in the NPY and NN complexes was suggested by X-ray structure analysis. NMR measurements were also performed on the complexes.