Cryogenic matrix photolysis of 3,5-dichloro-2,4,6-triazidopyridine, 3-chloro-5-cyano-2,4,6-triazidopyridine, 3,5-dicyano-2,4,6-triazidopyridine, and 3,5-difluoro-2,4,6-triazidopyridine (1-4) gives rise to ESR spectral peaks of various triplet mononitrene, quintet dinitrene, and septet trinitrene species. The quintet 2,4-dinitrenes derived from 1-2 and 3 have zero-field splittings (zfs) of \D/hc\ similar to 0.22-0.24 cm(-1), similar to values observed elsewhere for m-phenylene dinitrenes. 3,5-Dicyano-2,4,6-triazidopyridine (3) photolysis gives only a weak ESR signal corresponding to a mononitrene with a zfs of \D/hc\ similar to 1.22 cm(-1). The spectrum from 1 also shows a 2,6-dinitrene with \D/hc\ = 0.283 cm(-1), \E/hc\ = 0.036 cm(-1), which illustrates the effects of heteroatom perturbation upon the zfs of a geometrically rigid m-arylene dinitrene. Spectral peaks for unusual septet 2,4,6-trinitrenopyridines derived from complete deazetation of 1-2 were also identified by simulation of the septet spectra. The zfs parameters for the trinitrenes were estimated to be \D/hc\ similar to 0.1 cm(-1), with small E-values in both cases. Experimental and computational results support high spin ground states for the dinitrene and trinitrene species.