Installing an additional emission quenching pathway in the design of iridium(III)-based phosphorogenic biomaterials for bioorthogonal labelling and imaging

Bioorthogonal Conjugation of Transition Organometallic Complexes to Peptides and Proteins: Strategies and Applications

“…Again more pronounced enhancement effects were observed with nitrone than sydnone complexes ( I/I 0 = 292.8 for 30b compared to 24.9 29b , and 618.0 for 30c compared to 5.2 for 29c , with BCN‐BSA). Furthermore, emission enhancements are higher with BCN‐modified proteins than with BCN‐OH, which is attributed to increased hydrophobicity and rigidity brought by the protein in the proximal environment of cyclometalated iridium (III) polypyridine complexes, and this behavior is an additional asset when developing bioorthogonal imaging agents.…”

“…In another study, BCN‐modified BSA was bioorthogonally labeled with phosphorogenic tetrazine labels derived from cyclometalated iridium(III) complexes 41 . The emission of these complexes was efficiently quenched by FRET and/or PET process and turned on while the reaction of BCN‐BSA occurred with extremely large emission enhancement factors.…”

“…Complex 41 was applied to image azide‐modified N ‐glycans in live cells. Labeling was achieved by a two‐step procedure: a bis ‐BCN homobifunctional cross linker was treated with azido‐modified N ‐glycans, followed by reaction with complex 41 …”

Inverse electron‐demand Diels‐Alder (iEDDA) bioorthogonal conjugation of half‐sandwich transition metallocarbonyl entities to a model protein

“…Recently, Lo and coworkers reported a series of phosphorogenic dipyridyl rhenium(I) tricarbonyl complexes carrying a tetrazine handle on one of the ligands . The same team also reported cyclometalated iridium (III)‐based phosphorogenic complexes including a tetrazine group either appended to one of the ligands or directly involved in metal coordination …”

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

“…The longlived emission of these complexes provides an opportunity for the time-delayed elimination of background luminescence and for phosphorescent lifetime imaging. [15][16][17][18][19][20][21][22][23] In this paper we report unprecedented Ir(III) complexes of 1,2,4-triazines as luminogenic bioorthogonal reagents that react with BCN much faster than the uncoordinated 1,2,4-triazine ligand approaching the kinetic values of widely used tetrazines. However, the relatively high toxicity of the complexes imposes some limitations to bioorthogonality and further studies are necessary to address this problem.…”