Although synthesis and substitution reactions of chlorido chromium(III) porphyrins Cr-III(TPP)(Cl)(L) (H2TPP = 5,10,15,20-tetraphenyl porphyrin, L = pyridine, H2O, ROH, etc.), have been well-established in coordination chemistry for decades, an unexpected dichotomous reactivity of Cr-III(TPP)(Cl)(H2O) (1) toward amines is disclosed here. This reactivity leads to the application of 1 as highly sensitive substoichiometric and irreversible ON switch for amine detection by an autocatalytic pathway. The concomitant activation of O-2 by the 1/amine system is furthermore exploited in an electrochemically driven epoxidation of norbonene using O-2 as initial oxidant.