Organometallic iridium(III) complexes have seen increased application over the past two decades in fields such as photoredox catalysis, photodynamic therapy, biological sensing, and as phosphors for organic light-emitting diodes. Interest in the non-linear optical applications of these materials has also increased due to recent reports of two photon absorption and reverse saturable absorption (RSA) characteristics. RSA is a property where the excited state of a molecule absorbs more light than the ground state. The goal of this research is to develop an organometallic chromophore with absorption bands and RSA properties throughout the visible spectrum. Iridium was chosen as the transition metal center for the organometallic chromophore because of its strong spin-orbit coupling, which allows for multiple excited states, thereby increasing the compound’s ability to absorb light at various wavelengths. In order to systematically alter a series of complexes, a brominated derivative of [Ir(pbt)2(acac)], where pbt is 2-phenylbenzothiazole and acac is acetylacetonate, was designed, synthesized, and characterized. The iridium metallocyclic dimer, [Ir(bpb)2(Cl)]2, was synthesized using the 2-(4-bromophenyl)benzothiazole (bpb) ligand. Without further purification, the intermediate was collected and washed for subsequent synthesis to form the iridium acetylacetonate (acac), [Ir(bpb)2(acac)], complex. The resulting product was purified by flash column chromatography using hexane:dichloromethane solvent eluent and exhibited an Rf of 0.70. The isolated product was characterized by proton NMR in CDCl3 and DMSO, confirming the intended product was synthesized. The [Ir(bpb)2(acac)] complex was bright orange, similar to the parent complex. The yield over both reactions was 48%. The photophysical properties of this complex will be further characterized and examined for its RSA properties.

Synthesis of organometallic chromophores to investigate novel materials for reverse saturable absorption

ACS Spring Meeting 2021

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