ИСТИНА

Cyclometalated Ir(III) complexes have attracted particular attention as more stable analogs of Ru(II) dyes in dye-sensitized solar cells (DSSC). Still, poor light-harvesting properties of Ir(III) photosensitizers prevent their widespread application in DSSC. Up to now, there have been many efforts to enhance the absorptivity of Ir(III) dyes either by varying cyclometalated (C^N or ‘antenna’) ligands or by changing the substituents in 2,2’-bipyridine-based ‘anchoring’ ligands. However, a substantial improvement of photophysical characteristics of the complexes has not been achieved. Based on our previous study of Ir(III) dyes, we have assumed that the desired significant increase of their light-harvesting properties can be achieved by drastic change in the chemical nature of the ‘anchoring’ ligand. Specifically, aromatic β-diketones acting as negatively charged chelating ligands are anticipated to be very promising for constructing efficient Ir(III) dyes. Herein, we present a comprehensive study (X-ray, NMR, MS, UV-Vis, CVA, LS, DFT / TDDFT) of several series of iridium (III) complexes with 2-arylbenzimidazoles/2- arylphenantroimidazoles and different “anchoring” ligands: 4,4′-dicarboxy-2,2′- bipyridine (H2dcbpy), dibenzoylmethane (dbm), 1-(3-methoxycarbonylphenyl)-3- phenyl-propane-1,3-dione (dbmCOOMe) and 1-(3-methoxycarbonylphenyl)-3- tiophene-propane-1,3-dione (mtpd). We systematically studied the effect of the ligands structure on the optical and redox properties of the complexes as well as their electronic structures. Appropriate oxidation potentials, an optimal ground and excited states localization along with good lightharvesting characteristics of the complexes make them suitable candidates as photosensitizers in DSSC.