New quintet carbenonitrene system formed in the photolysis of 2,6-bis(4,5-dimethoxycarbonyl-1H-1,2,3-triazolo)-4-azido-3,5-dichloropyridine

New triplet pyridyl-4-nitrene, triplet pyridyl-2-imidoylcarbene and quintet 4-nitrenopyridyl-2-imidoylcarbene have been detected by EPR spectroscopy after photolysis of 2,6-bis(4,5-dimethoxycarbonyl-1H-1,2,3-triazolo)-4-azido-3,5-dichloropyridine at 77 K.