Pyridine-2-azo-p-phenyltetramethylguanidine (PAPT) and 4,4'-bis(tetramethylguanidine)azobenzene (BTA) were synthesized and investigated by osmometric measurements and by FT-IR spectroscopy. The two bases exist in acetonitrile as monomers whereas the monoprotonated and Li+ complexes (ratio 1:1) are dimers. In the N+H...N reversible N...H+N hydrogen bonds as well as in the N+Li...N reversible N...Li+N bonds the cations fluctuate. The charge fluctuation due to the cation fluctuation is, however, compensated by the electron fluctuation in the conjugated pi-electron systems. Thus, the transition moments of the proton or Li+ transitions, respectively, are very small and hence, these bonds show almost no proton or Li+ polarizability.
Leffek, Kenneth T.; Jarczewski, Arnold, Canadian Journal of Chemistry, 1991, vol. 69, # 8, p. 1238 - 1244