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Seven nondisjoint dinitrenes were produced in order to determine the length of chain conjugation that would still allow effective inter-nitrene exchange communication. The dinitrenes were generated in frozen matrices of 2-methyltetrahydrofuran by photolysis of appropriate diazides by a 1000-Watt xenon arc lamp and studied by electron spin resonance (ESR) spectroscopy. Conjugation lengths varied from 17 to 29 atoms between spin sites. In each case, it was determined by variable temperature analysis that the high-spin quintet state was the ground state. Six other dinitrenes were also produced which surprisingly exhibited quintet state spectra at 77 K, despite having possible quinoid biradical resonance structures. Possible reasons for the latter observation include conformational torsion effects, combined with a preference to retain benzenoid sextet resonance structures. In addition to the molecules produced in this lab, numerous samples of mono-, di-, and tri-azidopyridines were jointly studied with Dr. Sergei Chapyshev of the Russian Institute of Chemical Physics. These systems were studied by ESR spectroscopy. The effect of the pyridine heteroatom upon the ESR spectroscopy of these systems was found to be considerable, relative to simpler aryl nitrenes. Several of the triazide of systems were deemed to be ground state septet systems. |
