| Metal-organic complexes become a hot topic in modern scientific research becauseof their excellent luminous performance. When synthesis the metal-organic complexes,various nitrogen-bidentate ligand has been widely used, what’s more, the d10metals arealso widespreadly used as they can enhance the fluorescence quantum yield and lifetime.Therefore, in this thesis, three ligands are successfully synthesized with the materils ofp-phenylenediamine and2-carboxaldehyde,2-acetyl-pyridine,6-methoxy-pyridine-for-maldehyde. The three ligands are N,N’-bis(2-pyridylimino)-p-phenylenediamine(L1),N,N’-bis(2-acetylpyridineimino)-p-phenylenediamine(L2), N,N’-bis(6-methoxy-2--pyridyl imino)-p-phenylenediamine(L3). Then, eight metal-organic complexes (1~8)are systhesized with the three ligands and d10metals. After synthises, the11compoundsstructure are characterized by the way of NMR, IR and elemental analysis, in which L2,7and8are obtained crystal structure. The steady-state spectroscopy/transientspectroscopy of ligands and their complexes are tested and discussed in the condition ofsolid state and solution.At298K solid state, compared to L1, the maximum emission spectra of1,2and3are blue-shifted. It is due to the emitted energy of ligand-to-metal charge transfer(LMCT) is greater than Ï€*â†'Ï€ transition, but when they are in methanol solution at298K, the maximum emission spectra are almost the same. Comparing to L2,4~6arered-shifted when they are at298K solid state and in methanol solution. As to L3and7~8, at298K solid state the phenomenon is the same, which is attributed to the LMCTrearrangs the energy level. For L3and complexes7~8, their fluorescence spectra weretested in different solvents (C6H6, CH2Cl2, CH3OH, CH3CN, DMSO and DMF) at298Kand77K solid state, methanol solution. The same compound in different solvents at298K, the result shows that it is red-shift with the increase of solvent polarity for themaximum emission spectrum, which is ascribed to the polarity of the excited state islarger than the ground state. When in larger polar solvent, the energy of fluorescentmolecules decreases between excited state and the ground state. At298K, the differentcompounds in same solvent, the maximum emission spectrum is red-shifted for L37and8, but in DMF, it is blue-shifted, the special phenomenon is that the polar of DMF istoo large to make compounds impossible to rearrange the molecules in the excited statelifetime, so the energy of excited state can’t decrease for the compounds, which increasethe energy gap between excited state and ground state. At77K solid state, Compared toL3,8is blue-shifted, as it is almost unlimited for the interaction of the energy levelwhich increasing the energy gap between excited state and ground state. It is red-shiftedfor L3,7and8when they at the condition of77K methanol solution in contrast to thecondition of298K methanol. The fluorescent lifetime of L3,7and8are longer at77K solid state and methanol than that at298K solid state and methanol. It arises from thereducing of the nonradiative transitions energy. For all the compounds, the fluorescentlifetime at solid state is longer than that in solution. It is the environment polar issmaller at solid state which contributes to the fluorescence, therefore the lifetimes arelonger.The calculation results of quantum yield show that the luminous intensity ofcomplexes is better than ligands. It is because the metals increase the rigidity of ligand,Resulting in not only the non-radiative transition energy loss decreased between theexcited state and the ground state, but also good for the transition of the Ï€ electron... |
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