A neutral mononuclear rhenium(I) complex with a rare -generated triazolyl ligand for the luminescence "turn-on" detection of histidine.

A rare -generated mononuclear rhenium complex [Re(bpt)(CO)(NH)] (1, bpt = 3,5-bis(2-pyridyl)-1,2,4-triazolate) can be used as a "turn-on" luminescent probe for selectively sensing L-histidine against other amino acids. Compound 1 was prepared by reacting Re(CO), 2-cyanopyridine and hydrazine with an formed bpt ligand through cyclization C-N and N-N couplings with its single-side chelating mode arrayed with respect to the Re center. Compound 1 was highly stable and showed a green light MLCT emission in DMF solution at 507 nm upon excitation at 360 nm. Interestingly, the emission from 1 could be quenched by the addition of metal ions such as Ni and Cu but the emission efficiently recovered with the introduction of histidine. However, histidine could only be selectively detected when a combination of compound 1 and Ni was used. Therefore, the luminescence response of the Ni-modified compound 1 could be utilized as a "turn-on" probe for the selective detection of histidine. This work provides a simple method for developing new sensing platforms of a discrete metal complex based on rare generation.