Pyridine aldoxime ligation to iridium(III) centre: An innocent ancillary ligand in a series of organometallic complexes

Orange/red light emitting iridium(III) organometallic complexes containing 2,3‐di(pyridine‐2‐yl)quinoxaline as ancillary ligand and their anticancer properties

“…The two 2‐phenylpyridines tethered the metal centre through C and N with a trans orientation of two N's (N1A, N2A and N1B, N2B) with N1A−Ir(1A)−N2A and N1B−Ir(2B)−N2B angles at 173.7(2)° and 172.64(2)° respectively, whereas coordinated carbons (C1A, C12A & C1B, C12B) were in cis orientation. The trans orientation of ppy‐N's is consistent with the similar structured bis‐heretoleptic Ir(III) complexes reported in the literature [30,31] . This is in support of the mild reaction condition employed in the preparation of Ir1 , which maintained the ppy coordination unchanged as found in the stating material SM1 (Figure 1).…”

“…These bands with very low extinction coefficients were assigned to the spin‐forbidden electronic transitions, which might have originated from 3 MLCT, 3 LLCT and 3 ILCT [35] absorptions. The appearances of the absorption bands were quite similar with the reported bis‐heteoleptic Ir(III) complexes [30,35,36] …”

“…The trans orientation of ppy-N's is consistent with the similar structured bis-heretoleptic Ir(III) complexes reported in the literature. [30,31] This is in support of the mild reaction condition employed in the preparation of Ir1, which maintained the ppy coordination unchanged as found in the stating material SM1 (Figure 1). Apart from ppy ligand, the Ir(III) coordination sphere consisted of cis oriented two N's ( N3A,N4A and N3B,N4B) emanated from pyrquinox ligand.…”

“…The ppy origined Ir(1A)−N1A and Ir(1A)−N2A bond lengths [2.054(5), 2.044(5)Å] were found shorter than the Ir(1A)−N3A and Ir(1)−N4A [2.208(5)Å, 2.125(5)] bond distances linked to pyrquinox ligand. A very same Ir−N bond lengths anomaly around Ir(1B) centre also could be linked to the very same explanation [30] . Inspection of the structures revealed that the coordinated 2,3‐di(pyridine‐2‐yl)quinoxaline (pyrquinox) was non‐planar, where the coordinated part of pyrquinox bent like an arch along with a pendant pyridine ring remain non‐coordinated.…”

“…A very same IrÀ N bond lengths anomaly around Ir(1B) centre also could be linked to the very same explanation. [30] Inspection of the structures revealed that the coordinated 2,3-di(pyridine-2-yl)quinoxaline (pyrquinox) was non-planar, where the coordinated part of pyrquinox bent like an arch along with a pendant pyridine ring remain noncoordinated. A host of hydrogen bond sourced through PF 6 À ion produced a hydrogen bonded network structure as depicted in Fig.…”