Synthesis, crystal structure, photophysical property and electropolymerization of Pt(II) complexes with carbazole-grafting 2-(2-pyridyl)benzimidazole

Two neutral-charged Pt(II) complexes, i.e., [(PBC)PtCl2] (5) and [(PBC)Pt(C ≡ CC6H5)2] (6) (PBC = N-[4-(9-carbazole)butyl]-2-(2-pyridyl)benzimidazole) have been synthesized and verified by 1H NMR and X-ray crystallography. In each of them, the coordinate geometry of Pt atom is a distorted square planar configuration with bond distances and angles in the normal range. Complex 6 shows an intense metal-to-ligand charge transfer (1MLCT) (dπ(Pt) → π*(L)) transition at 412 nm in the UV-Vis absorption spectrum and a strong phosphorescence at 593 nm in CH2Cl2 solution at ambient temperature. By selective optical-stimulation at 320 nm, an incomplete intramolecular energy transfer process from the carbazole unit to the [(PB)Pt(C ≡ CC6H5)2] center results in unbalanced dual-emissive bands of a quenched carbazole-based luminescence in deep blue region and an orange 3MLCT emission with increasing intensity. The introduction of carbazole unit also triggers the electropolymerization of ligand PBC and complexes 5 and 6. The as-formed polymer film from complex 5 has good conductivity, stability and clear anodic coloration effect.

Functionalized Pt(II) complexes: The neutral-charged Pt(II) arylacetylide and chloride complexes with N-[4-(9-carbazole)butyl]-2-(2-pyridyl)benzimidazole (PBC) show an enhanced orange 3MLCT emission induced by an intramolecular energy transfer process and the promising electropolymerization activity to form an anodic coloration film, respectively.Figure optionsDownload as PowerPoint slideResearch highlights
► Carbazole unit as the high triplet energy donor.
► Bi-chromophoric system with an intramolecular energy transfer process.
► Carbazole unit as the electro-active moiety.
► Conductive metallopolymer film with a clearly electrochromic behaviour.