with BCN derivatives compared to corresponding uncoordinated ligands. The second order rate constants (in M -1 s -1 ) are shown in brackets. Reaction conditions: for 1 and 2, CH3CN:H2O (1:1, v/v) at 25°C, BCN-OH; for 2 and 6, MeOH at 25°C, BCN-OH; for 3 and 7 MeOH at 25°C, BCN-C10. All IEDDA reactions are strongly luminogenic. Complex 8 was isolated for detailed analysis of the photophysical properties of the IEDDA reaction of complex 4 with BCN.