1,12-Diazaperylene and 2,11-dialkylated-1,12-diazaperylene iridium(iii) complexes [Ir(C^N)2(N^N)]PF6: new supramolecular assemblies

Abstract

A series of new monocationic iridium(III) complexes [Ir(C^N)₂(N^N)]PF₆ with “large-surface” α,α′-diimin ligands N^N (dap = 1,12-diazaperylene, dmedap = 2,11-dimethyl-1,12-diazaperylene, dipdap = 2,11-diisopropyl-1,12-diazaperylene) and different cyclometalating ligands C^N (piq = 1-phenylisoquinoline, bzq = benzo[h]quinoline, ppz = 1-phenylpyrazole, thpy = 2-(2-thienyl)pyridine, ppy = 2-phenylpyridine, meppy = 2-(4-methylphenyl)pyridine, dfppy = 2-(2,4-difluorophenyl)pyridine) were synthesized. The solid structures of the complexes [Ir(piq)₂(dap)]PF₆, [Ir(bzq)₂(dap)]PF₆, [Ir(ppy)₂(dipdap)]PF₆, [Ir(piq)₂(dmedap)]PF₆, [Ir(ppy)₂(dap)]PF₆ and [Ir(ppz)₂(dap)]PF₆ are reported. In [Ir(piq)₂(dap)]PF₆, the dap ligand and one of the piq ligands of each cationic complex are involved in π–π stacking interactions forming supramolecular channels running along the crystallographic c axis. In the crystalline [Ir(bzq)₂(dap)]PF₆ π–π stacking interactions between the metal complexes lead to the formation of a 2D layer structure. In addition, CH–π interactions were found in all compounds, which are what stabilizes the solid structure. In particular, a significant number of them were found in [Ir(piq)₂(dap)]PF₆ and [Ir(bzq)₂(dap)]PF₆. The crystal structures of [Ir(ppy)₂(dipdap)]PF₆ and [Ir(ppy)₂(dmedap)]PF₆ are also presented, being the first examples of bis-cyclometalated iridium(III) complexes with phenanthroline-type α,α′-diimin ligands bearing bulky alkyl groups in the neighbourhood of the N-donor atoms. These ligands implicate a distorted octahedral coordination geometry that in turn destabilized the Ir–N_N^N bonds. The new iridium(III) complexes are not luminescent. All compounds show an electrochemically irreversible anodic peak between 1.15 and 1.58 V, which is influenced by the different cyclometalated ligands. All of the new complexes show two reversible successive one-electron “large-surface” ligand-centred reductions around −0.70 V and −1.30 V. Electrospray ionisation mass spectrometry (ESI-MS) and collision induced decomposition (CID) measurements were used to investigate the stability of the new complexes. Thereby, the stability agreed well with the order of the Ir–N_N^N bond lengths.