Synthesis, Photophysics and Tunable Reverse Saturable Absorption of Bis-Tridentate Iridium(III) Complexes via Modification on Diimine Ligand

Abstract

Five novel bis-tridentate Ir(III) complexes (Ir-1–Ir-5) incorporating versatile N^N^C ligands and a N^C^N ligand (1,3-di(2-pyridyl)-4,6-dimethylbenzene) were synthesized. With the combination of experimental and theoretical methods, their steady and transient state characteristics were researched scientifically. The UV-visible absorption spectra show that the broadband charge transfer absorbance of those bis-tridentate Ir(III) complexes can reach 550 nm, all of these complexes reveal the long-lasting phosphorescent emission. Because the excited-state absorption is more powerful than the ground-state absorption, a sturdy reverse saturable absorption (RSA) process can ensue in the visible and near-infrared regions when the complexes are exposed to a 532 nm laser. Therefore, the optical power limiting (OPL) effect follows the trend: Ir-5 > Ir-4 ≈ Ir-3 > Ir-2 > Ir-1. Generally speaking, the expansion of π-conjugation and the introduction of electron donating/withdrawing groups on the N^N^C ligand could effectively elevate the OPL effect. Therefore, these octahedral bis-tridentate Ir(III) complexes might be exploited as potential OPL materials.

[4,6-Di-tert-butyl-N-(2,6-Dimethylphenyl)-o-Amidophenolato][4,6-Di-tert-butyl-N-(2,6-Dimethylphenyl)-o-Iminobenzosemiquinolato](2,2′-Bipyridyl)Indium(III)

“…Plenty of chromophore systems include rich classes of intramolecular charge transfer dyes represented by organic [1][2][3][4], polymer [5,6], organometallic [7], and coordination compounds [8]. A design of metal complexes, which contains both donor and acceptor organic parts coordinated to the metal center and can act as ligand-to-ligand charge-transfer (LL CT) chromophores, is one of the actual trends in modern chemistry [9][10][11][12][13]. Since the structure and therefore absorption profile, redox potentials, and molecular polarity of LLCT complexes can be tuned easily, these compounds can find application in photochemical charge-transfer and nonlinear optics [14][15][16][17][18][19][20].…”