Photolysis of Ar matrix isolated trifluoromethyl-substituted 2-pyridyl azides/tetrazolo [1, 5-a] pyridines at 12-18 K causes rapid and mostly clean conversion to the corresponding 1, 3- diazacyclohepta-1, 2, 4, 6-tetraenes (4D, 5D, 5, 6D, and 4, 6D) absorbing near 2000 cm-1 in the IR. In the latter case, the intermediate 3, 5-bis (trifluoromethyl)-2-pyridylnitrene (4, 6N) was observed by both ESR and IR spectroscopy and converted to the ...