Studies On Single Molecular Conductivity Of Mo₂ Complexes And Intramolecular Electron Transfer In Square Mo₂ Clusters

With the continuous acceleration of information science and technology in modern society,our demand for information is also growing.But silicon-based electronic devices can no longer meet our daily needs,and in order to solve such problems,the emerging discipline-molecular electronics came into being.It is hoped that the exploration of molecular electronics will produce devices with efficient and stable performance.The key to fabricating such devices is to understand the charge transport in molelulars and to identify the factors that affect the transport propertities..Recently,metal centers are found to be able to increase the functionality of molecular wires.Introduction of metal centers to the molecules increases their long distant conductance with low attenuation factors in comparison with pure organic systems having similar backbones..In view of this,in the first part,two linear trans-dimolybdenumcomplexes,[Mo₂?DAniF?₂?C₅H₄NCO₂?₂]?DAniF=N,N?-di?p-anisyl?formamidiante,and C₅H₄NCO₂=nicotinate or isonicotinate?were synthesized and characterized by single-crystal X-ray diffraction.These compounds possess meta and para connected pyridyl groups and thus,are denoted as m-Mo2 and p-Mo2,respectively.Their single-molecule conductance was measured by using STM break junction technique?STM-BJ?.Significantly,complex are measured conductance is both high conductance greater than 10^-3 G₀.Interestingly,the cross-conjugated m-Mo2 exhibits appreciably larger conductance than the linearly conjugated p-Mo2.These results are rationalized by DFT calculations.The second part of this thesis,we synthesed three dimolybdenum squares[Mo₂?DAniF?₂]₄??-O₂CCO₂?₄?DAniF=N,N?-di?p-anisyl?formamidiante??[Mo2-OO]₄?,[Mo₂?DAniF?₂]₄??-OSCCOS?₄?[Mo2-OS]₄?,and[Mo₂?DAniF?₂]₄??-S₂CCS₂?₄?[[Mo₂-SS]₄]?by assembling[Mo₂?DAniF?₂]²⁺building blocks with the oxalate or thiooxalate bridging ligand,[E₂C–CE₂]^2-?E=O or S?.These compounds are characterized by ¹H-NMR and single crystal diffraction.The mixed-valence compounds are prepared by single-electron oxidation and by two-electron oxidation with NOPF₆.EPR spectroscopy and electronic spectra of MV compounds determine that two unpaired electrons reside s at counterpoint position of the dimetal center.Based on the classical Marcus theory,the electronic coupling effect(H_ab)is calculated in the range of 1100-1800 cm^-1,and the electron transfer rate(k_et)is in the range of 1.2×10¹¹-3.7×10¹².