Cyclometalated Iridium(III) Complexes as Two‐Photon Phosphorescent Probes for Specific Mitochondrial Dynamics Tracking in Living Cells

Abstract

Five cyclometalated iridium(III) complexes with 2-phenylimidazo[4,5-f][1,10]phenanthroline derivatives (IrL1-IrL5) were synthesized and developed to image and track mitochondria in living cells under two-photon (750 nm) excitation, with two-photon absorption cross-sections of 48.8-65.5 GM at 750 nm. Confocal microscopy and inductive coupled plasma-mass spectrometry (ICP-MS) demonstrated that these complexes selectively accumulate in mitochondria within 5 min, without needing additional reagents for membrane permeabilization, or replacement of the culture medium. In addition, photobleaching experiments and luminescence measurements confirmed the photostability of these complexes under continuous laser irradiation and physiological pH resistance. Moreover, results using 3D multicellular spheroids demonstrate the proficiency of these two-photon luminescent complexes in deep penetration imaging. Two-photon excitation using such novel complexes of iridium(III) for exclusive visualization of mitochondria in living cells may substantially enhance practical applications of bioimaging and tracking.

The use of organolithium reagents for the synthesis of 4-aryl-2-phenylpyridines and their corresponding iridium(iii) complexes

“…The structure shows a hydroxy-group and a mes-ring attached to C3 of the Boc-protected piperidine and is consistent with the NMR, mass-spectrometry and elemental analyses. The rings in the cation [7] are also almost perpendicular to the torsion angle (C4-C3-C6-C7) of 72.98 (17)°. 2) shows that the tertiary hydroxy-group in 3 has been dehydrated to form an alkene bond between C3 and C4, and the corresponding bond length is 1.392(2) Å.…”

“…Significantly, this allows for the harvesting of both singlet and triplet excitons within an OLED, theoretically allowing 100% internal quantum, and since their first deployment in these devices by Forrest et al, they have been the subject of numerous patents and papers. [12][13][14][15][16][17][18][19][20][21] Their emission spectra can be readily tuned by altering either the ancillary or 2-phenylpyridine ( ppy) ligand. [12][13][14][15][16][17][18][19][20][21] Their emission spectra can be readily tuned by altering either the ancillary or 2-phenylpyridine ( ppy) ligand.…”

A novel multifunctional cyclometallated iridium(III) complex with interesting second-order nonlinear optical properties and two-photon absorption activity

“…In this way, the charge-transfer property and the extended π-conjugation over the whole molecule results in good TPA properties of 5 compared to the previously reported complexes of similar structures. Besides, it is worth pointing out that some iridium(III) complexes bearing two cyclometallated unsubstituted 2-phenylpyridines and a 2-phenylimidazo[4,5-f] [1,10]phenanthroline, characterized by two-photon absorption crosssections in the range 48.8-65.5 GM at 750 nm, were utilized as efficient agents for mitochondrial imaging and tracking in living cells under two-photon (750 nm) excitation [21].…”

Cyclometalated Iridium (III) complexes: Recent advances in phosphorescence bioimaging and sensing applications

“…reported seven new Ir (III) complexes 57–63 having imidazole and phenanthroline moiety to have mitochondrial image . The same research group also reported few more complexes 64–68 for mitochondrial imaging in living cell . (Scheme A‐4C).…”