Electrochromic films with high optical contrast prepared by oxidative electropolymerization of a novel multi-functionalized cyclometalating ligand and its neutral-charged Pt(II) complexes

Abstract A novel multi-functionalized cyclometalating ligand (H L ) and its two neutral-charged Pt(II) complexes, i.e., [( L )PtCl] ( C1 ) and [( L )Pt(C CC 6 H 5 )] ( C2 ) (H L  = 4-{ p -[N-(4-(9-carbazole))butyl-N-phenyl]anilino}-6-phenyl-2,2′-bipyridine), have been successfully synthesized and verified by 1 H NMR, 13 C NMR, elemental analysis and/or X-ray crystallography. The introduction of the electron-donating arylamino unit at the 4-position of the electron-withdrawing 6-phenyl-2,2′-bipyridine ligand forms the D–A system, resulting in the enhanced 1 MLCT bands in the absorption spectra and intense orange emissions in the PL spectra of C1 and C2 . The carbazole units grafted through alkyl chain in H L , C1 and C2 electrochemically trigger the efficient cross-linking reaction to form polymer films, which have been characterized by AC impedance, SEM and spectroelectrochemistry. Each of the poly-H L and poly- C1 films exhibits reversible oxidation with significant color change having a high contrast ratio (81.8% for poly-H L film and 67.3% for poly- C1 film), a reasonable coloration response time (6.3 s for poly-H L film and 3.1 s for poly- C1 film) and a comparable coloration efficiency (158 C −1  cm 2 for poly-H L film and 132 C −1 cm 2 for poly- C1 film) that can be switched by modulation of the applied potential.