Molecules and ions in a donor acceptor complex

This paper reports the results of an x-ray analysis, electron spin resonance, electrical conductivity, u.v. and visible spectroscopic measurements on TMPD-chloranil. The results can be explained by assuming a molionic lattice, i.e. a crystal lattice built up of neutral TMPD and chloranil molecules together with bi-valent positive TMPD ions and bi-valent negative chloranil ions. Elementary excitations creating (chloranil- … TMPD++ … chloranil-) are presumed to be responsible for the measured paramagnetism. It was found that two modifications of TMPD-chloranil exist, which at room temperature are only distinguishable by the anisotropy of their E.S.R. linewidth. At low temperature both modifications suffer a phase transition, as observed on x-ray Weissenberg photographs and confirmed by E.S.R. measurements.