The Interface Assembly Of Molecular Aggregate Material And Its Electrochemical Studies

Organized molecular aggregates formed by non-covalent interactions between molecules have attracted growing attention in the past. Organic or inorganic small molecules, macromolecules and macrocyclic compounds can be used as units to build such kinds of molecular aggregates which resulting in on new materials having potentia l applicationsin the fields of catalyst,magnetism,molecular devices and so on. Generally, the materialscan be prepared by Langmuir-Blodgett (LB), self-assembly and layer-by-layer assembly techniques.The thesis is divided into two parts. Firstly, Coordination polymers (CPs) can encapsulate small molecules within their nanosized coordination cages to form hybrid supramolecular materials. We reported here assembly of Pd(Ⅱ)-mediated CP multilayers on the substrate surfaces by layer-by-layer method with six kinds of multidentate ligands as linkers, which included 4,4'-bipyridyl (Bpy), binaphthylbis(amidopyridyl) (BNBAPy), tris(4-pyridyl)-1,3,5-triazine (TPyTa), tetra(4-pyridyl)porphyrin (TPyP), ligand-like complex of Fe(pyterpy)2 (pyterpy: 4'-(4-pyridyl)-2,2':6',2"-terpyridine), and poly(4-vinylpyridine) (PVP). The multilayer assembly process was characterized by using UV-vis absorption spectra and X-ray photoelectron spectra. Electrochemical behaviors of the as-prepared CPs-modified electrodes were investigated in hexacyanoferrate solution, which revealed well-reversible redox waves of Fe(CN)63-/4- ions for the electrode covered with the Pd-TPyTa or Pd-Fe(Pyterpy)2, while irreversible ones for the electrode covered with the Pd-BPy or Pd-PVP. The results indicated that Fe(CN)63-/4- ions could reach electrode surface across the CP multilayers of TPyTa or Pd-Fe(Pyterpy)2, which was attributed to that their coordination cages were larger enough for the Fe(CN)63-/4- ions to penetrate through. The present methodology provides a facile way to construct three-dimensional supramolecular materials on the solid surfaces, which may be used to study the charge transfer behaviors in artificial membranes.Secondly, Hydrogenase (H2ase)-cationic electrolyte biohybrids were assembled at the air-water interface via intermolecular electrostatic interaction. The H2ase used was purified from the phototropic bacterium of Thiocapsa roseopersicina. Two kinds of cationic electrolyte compounds (CECs) were used, the difference of which was whether they contained viologen substituent or not. Surface pressure-area isotherms indicated that these CECs were co-existed with the H2ase in the monolayers, which were then transferred to substrate surfaces to form H2ase-CECs hybrid films by the Langmuir-Blodgett (LB) method. Uniform film was formed when polyelectrolyte was used as the subphase. Cyclic voltammograms (CVs) of the LB films showed a couple of redox waves in the potential range of -0.4～-0.65 V vs Ag/AgCl, which was ascribed to one electron process of either [4Fe-4S] clusters of H2ase or viologens of the CECs. A direct electron transfer between the H2ase and electrode surface was achieved in the LB films. Stronger current intensity was recorded when the CV measurements were done in H2 saturated electrolyte solution than that in Ar. It was confirmed that the H2ase biocatalytic activity remained in the LB films. Thus, we suggest that the present H2ase-CECs biohybrids could act as potential materials for the studies of interconversion reaction of H2 and protons.