Palladium(II)-directed layer-by-layer assembly of chiral metal–organic complex multilayers with bidentate ligands of hydroquinine anthraquinone-1,4-diyl diether as linkers on substrate surfaces

Palladium(II)-directed chiral metal–organic complex multilayers have been prepared on substrate surfaces through a layer-by-layer (LBL) assembly using hydroquinine anthraquinone-1,4-diyl diether bidentate ligands as linkers. The assembling process was monitored by measuring UV–vis absorption and X-ray photoelectron spectra, as well as scanning electron and atomic force microscopy after each layer. It was shown that the molecular chirality of the ligands was retained in the metal–organic complex multilayers. The LBL multilayer fluorescence spectrum showed a broad band at approximately 365 nm corresponding to the emission from the excited hydroquinine substituents. Cyclic voltammograms revealed a quasi-reversible redox wave couple with cathodic and anodic potentials of −0.35 and −0.05 V (vs. Ag/AgCl) at a potential scan rate of 0.05 V/s, which could be assigned to the redox reaction of metal–organic complexes in the multilayers. Further, the redox potential and the potential separation between cathodic and anodic peaks closely depended on the potential scan rate due to the strong film resistance caused by the closely packed arrangement of the metal–organic complexes in the LBL multilayers.