Studies On Design, Synthesis, And Properties Of Functionalized Alkynylferrocene Conjugated Molecules

Conjugated organic molecules are widely applied in molecular wires, photoelectric conversion, molecular recognition, and other fields because of their easy tuning performance by means of structural modification. The design and assembly of molecular wires are the focus of molecular electronics. Hybrid composites of π-conjugated organic molecules and nanoparticles are of great current interest in the research of functional materials. The incorporation of alkynylferrocene, featured by its rigid three-dimensional structure, electrochemical activity, and π-electrons delocalization, into traditional functional molecules is expected to provide optoelectronic functional materials with novel structures and properties.In this dissertation, aiming to the property studies of ruthenium(II) terpyridine complexes, self-assembled monolayers and organic-inorganic hybrid composites, the design and synthesis of a series of 1,2- and 1,1’-disubstituted ferrocenes based on the alkynylferrocene building block are described. The cyclopentadienyl ring or alkynyl moiety was functionalizd by terminal groups, including terpyridine, dithiazepane, and benzoic acid, via Krohnke pyridine synthesis and Sonogashira cross-coupling reaction. The new compounds were characterized by NMR spectroscopy, MS, elemental analysis, IR spectroscopy, single crystal X-ray diffraction, and UV-vis spectroscopy.The solution redox properties of the ferrocene derivatives were investigated by cyclic and differential pulse voltammetry. The room temperature photophysical properties of alkynyl-bridged Ru(II) 4’-diferrocenyl(ethynyl)-2,2’:6’,2"-terpyridine complexes were studied by luminescence spectroscopy. The studies of the self-assembly behavior of dithiazepane-functionalized alkynylferrocenyl terpyridine ligand and its ruthenium complexes on gold substrate were performed by contact angle and ellipsometric thickness measurements and X-ray photoelectron spectroscopy. The influence of molecular structure on the surface coverage and electron transfer rate of the self-assembled film on gold electrode was investigated using cyclic voltammetry and electrochemical impedance spectroscopy. During the preparation of alkynyl-bridged carboxyl group-containing conjugated molecules, an unusual intramolecular heteroannular cyclization reaction of methyl 4-(((1’-(trimethylsilyl)ethynyl)ferrocenyl)ethynyl)benzoate yielded 1,3-disubstituted 1,3-butadienyl heteroannular bridged [4]ferrocenophane under basic desilylation condition was found. The structure of the ferrocenophane was confirmed by single crystal X-ray diffraction and the substituent effect on the stability of the resulting ferrocenophanes was investigated. Hybrid composites of carboxyl-terminated alkynylferrocene molecular wires and semiconductor nanoparticles were prepared in two steps. First, the preparation of Cd or Pb salts via ion exchange reaction of the potassium carboxylates. Subsequently, conversion of the metal salts into CdS or PbS nanoparticles embedded in carboxyl acids by a topotactic solid/gas reaction with H2S gas. The topotactic reaction was monitored by IR and X-ray photoelectron spectroscopies. The influence of length of conjugated molecules on the morphology and distribution of the nanoparticles in the hybrid composites was inspected by transmission electronic microscopy. Primary studies of the electrochemical behavior of two polyferrocenylalkynes with up to four ferrocenyl moieties were also conducted.