Ferrocene-Alkynyl Conjugated Molecular Wires:Synthesis,Characterization And Conductance Properties

The design and synthesis of functional molecular wires which show response to light,PH and electrochemistry is the most essential and challenging aspects in the field of molecular electronics.Among them,the development of molecular wires with electrochemical response has drawn much attention.In particular,ferrocene as an outstanding redox molecule,plays an quite important role in this respect.Many 1,1-substituted ferrocene molecular wires have been designed in purpose of reducing the intermolecular ?-? stacking during the electrical properties measurement.However,due to the rotation of the cyclopentadienyl rings aroud the iron,the anchoring groups of 1,1'-substituted ferrocene wires are able to bind on the gold surface with both side,which leads to a difficulty of forming the metal-molecular-metal junctions.Therefore,thiol(-SH),pyridine(-PY)and ferrocene-alkynyl are carried out in this project as the anchor groups and the molecular backbone respectively in order to analyse their photoelectrical properties.1,1-substituted ferrocene moiety is replaced with 1,2,3-substituted ferrocene,gold is selected as electrode material and the approach of Scanning Tunneling Microscope Break Junction(STM-BJ)is carried out to form the metal-molecule-metal molecular junctions.We expect that 1,2,3-substituted ferrocene molecular wires can both reduce the intermolecular ?-?stacking in traditional OPE wires and prevent the rotation problem in 1,1-substituted ferrocene molecular wires.The main contents include the following three aspects:1.A brief review of research on molecular electronics in recent years.In particular,this chapter introduces the concept of molecular wires,three components of molecular junctions(anchoring groups,molecular backbone and electrode material),the method for measuring molecular conductance(STM-BJ and MCBJ),two transmission mechanism of electron(tunneling and hopping mechanism)and factors affecting the molecular conductance.2.Synthesis and conductance measurement of 1,2,3-substituted ferrocene molecular wires.Synthesis of wire-1 and wire-2 using Sonogashira coupling reaction and the crystal structure of wire-2 obtained as well.The properties of self-assembled monolayers and the single-molecular conductance were tested on EIS and STM-BJ,respectively.The results indicate that the 1,2,3-substituted ferrocene molecular wires can not only reduce the the intermolecular ?-? stacking,but also solve the rotation problem in 1,1-substituted ferrocene molecular wires.3.Synthesis and electrochemical analysis of butadiyne-bridged dinuclear ferrocene derivatives.Synthesis of wire-5 and wire-6 was conducted by Sonogashira coupling and the target molecules were characterized by 1H-NMR?3C{H}-NMR?MS and HR-MS.The photoelectrical properties of the target molecules were tested by cyclic voltammetry(CV)and UV-vis absorption spectra.In conclusion,the butadiyne is an outstanding bridging group according to the result of CV and UV-vis,which provides a good interaction between the two separated ferrocene units,paving the way for the further study in spectroelectrochemistry.