REMOTE ACTIVATION OF AN AROYL AZIDE BY LONG-DISTANCE INTRAMOLECULAR ELECTRON-TRANSFER - IRRADIATION OF AN AMINE STEROID AZIDE SYSTEM

Bichromophoric compounds cis- and trans-3xi-(N-(p-methoxyphenyl)-N-methylamino)-5alpha-androstan-17beta-yl 4-(azidocarbonyl)benzoate (1 and 2, respectively) were synthesized and studied. Steady-state photophysical measurements indicate that the singlet excited state of the aryl amine (donor) is quenched by the remote aroyl azide (acceptor) group. These findings reveal that it is possible to activate this functional group separated in space from an absorbing ''antenna'' group. The mechanism of this long-distance interaction is shown by time-resolved spectroscopic measurements and by analysis of the reaction products to be through-bond and, perhaps in one case, through-space electron transfer. The triplet excited state of the donor chromophore also plays a role in the remote activation. It may participate either by long-distance electron or long-distance energy transfer. Intramolecular electron transfer in 1 or 2 generates an aryl amine radical cation and the azide radical anion. The azide radical anion exhibits unique chemical reactions dominated by protonation or by loss of nitrogen to form the nitrene radical anion.