Synthesis, Structure, Optical, and Electrochemical Properties of Iridium(III) Complexes with 2-Arylphenantroimidazoles and Dibenzoylmethane

Aromatic β‐Diketone as a Novel Anchoring Ligand in Iridium(III) Complexes for Dye‐Sensitized Solar Cells

“…In complex [Ir(cpbi) 2 (CH 3 CN)Cl] (cpbi = 1‐phenyl‐2‐(4‐chlorophenyl)benzimidazole), the Ir III ion adopts a slightly distorted octahedral geometry with both monodentate ligands (Cl – and CH 3 CN) lying opposite the metallated carbon atoms (Figure ). The Ir–Cl and Ir–N(acetonitrile) distances in this adduct (2.4850(10) and 2.109(4) Å, respectively) are consistent with those in the reported analog with the Ir–Cl bond length being just a little shorter than the average Ir–Cl distance in known µ‐chloro‐bridged dimers (2.514(3) Å) according to the Cambridge Structural Database (CSD, Ver. 5.39, Aug 2018).…”

“…UV/Vis absorption spectra of complexes 1–5 measured in CH 2 Cl 2 at 25 °C. The band assignment is based on ref …”

“…So, it seems reasonable that the desired significant decrease in the redox potentials of the complexes, while maintaining a high Ir d‐orbitals participation in the HOMO, can be achieved by drastic change in the chemical nature of the anchoring ligand. Specifically, β‐diketones acting as negatively charged chelating ligands are anticipated to be very promising for constructing efficient Ir III dyes , . Surprisingly, metal complexes with aromatic β‐diketones bearing anchoring acid groups have not been explored for DSSC.…”

Tailoring the π-system of benzimidazole ligands towards stable light-harvesting cyclometalated iridium(iii) complexes

“…However, this gets further complicated by the fact that the enlargement of the π-system can also be accompanied by increase of steric hindrance exerted by the ligands negatively affecting the stability of the iridium octahedron. 55 For example, the combination of bulky phenanthroimidazole-based ligands (containing two additional fused rings as compared to the parent benzimidazole system) and an ancillary aromatic β-diketone or pyridylphenanthroimidazole around the iridium(III) ion did not lead to the improvement of absorption in the visible region, [56][57][58] but surprisingly enhanced the reactivity of the complexes, which dissociated on the surface of the standard titania photoanodes. 59 Based on these studies, we have concluded that phenanthroimidazole is the edge case (at least for imidazole-based cyclometalating ligands) and further extension of the conjugated π-system in this part of the ligands can only lead to a further decrease in the stability of the octahedral complexes.…”

A Panchromatic Cyclometalated Iridium Dye Based on 2-Thienyl-Perimidine

“…Though the vast majority of C^N-cyclometalated iridium(III) chlorides are μ-chloro-bridged dimers [ 27 ], it is well documented that the increase in the steric pressure (for example, induced by phenanthroimidazole-based cyclometalated ligands) destabilizes the iridium octahedron and rare monomeric trigonal–bipyramidal chlorides can be isolated [ 28 , 29 , 30 , 31 , 32 , 33 ]. Given that the perimidine core is sterically more bulky than nitrogen-containing parts of cyclometalated ligands commonly used in iridium(III) chemistry (in most cases, pyridine ring in 2-phenylpyridines), and is rather similar to the phenanthroimidazole unit, the formation of the above monomeric species becomes possible.…”