Iridium(III) complexes of 1,2,4-triazines as potential bioorthogonal reagents: metal coordination facilitates luminogenic reaction with strained cyclooctynes

In this paper we describe unprecedented Ir(III) complexes of 5-(2-pyridyl)-1,2,4-triazine and their reactivity towards the strained cyclooctyne BCN. The coordination of a 1,2,4-triazine ring to an iridium(III) ion drastically increases the speed of the reaction, showing the second order rate constant of 8 M−1 s−1, the record value to date for a triazine-BCN reaction.