ESR study of the molecular orientation and dynamics of stable organic radicals included in the 1‐D organic nanochannels of 2,4,6‐tris‐4‐(chlorophenoxy)‐1,3,5‐triazine

Abstract

The molecular orientation and dynamics of the organic stable radicals such as 2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPO) or 4-hydroxy-TEMPO (TEMPOL) included in the one-dimensional (1-D) organic nanochannels of 2,4,6-tris-4-(chlorophenoxy)-1,3,5-triazine (CLPOT) were investigated by examining the inclusion compounds (ICs) diluted by the co-inclusion of non-radicals using ESR spectroscopy. Spectral simulation showed that the axial rotation of TEMPO or TEMPOL molecules is excited in the nanochannels with activation energies of 8 and 7 kJ mol(-1) , respectively. The rotation axis was estimated to be tilted towards the principal x direction in the axis system of the g-tensor of the respective radicals. This is quite different from that for similar ICs in the nanochannels of tris(o-phenylenedioxy)cyclotriphosphazene (TPP), in which the radicals are axially rotating around the principal axis y of the g-tensor. The difference is attributed to the larger nanospace of the CLPOT nanochannels.