Synthesis,Self-assembly And Photophysics Of Platinum (?) Complexes With Bipyridyl And Beta-diketonato Ligands

The family of platinum(?) complexes containing bipyridyl ligand is commonly observed in platinum complexes. These complexes have square-planar geometry, which allows them to form platinum-platinum interaction and ?-? interaction more efficiently. These interactions made the complexes to show rich photophysical properties. Platinum complexes could aggregate and undergo self-assembly through non-covalent interactions, such as hydrophobic-hydrophobic interaction, electrostatic interaction, host-guest interaction and hydrogen bonding, resulting in interesting photophysical properties and formation of nano-structures. Beta-diketonato ligands have been studied for more than one century, as the ligands coordinate with transition metals. The ease of forming single crystal of these complexes allows them to be widely used in optical devices. It was found that the transition metal complexes with beta-diketonato ligands showed liquid crystal properties. These complexes consisted of centralmetallomesogen and modified by long alkyl chains, so that they could form discoid liquid crystal and show column phase. Although platinum complexes with bipyridyl or beta-diketonato ligands have been widely studied, the researches on the system with both of ligands are scarce.Based on the aforementioned scenario and research background, the thesis started with the design and synthesis of the platinum(?) complexes with bipyridyl and and beta-diketonato ligands. Their photophysical, self-assembly properties in solution as well as liquid crystalline properties were also studied.At first, we synthesized the diketonato ligand L1 with six dodecyl chains according to the reported literature. After that, platinum(?) complexes with different bipyridyl ligands, such as 2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine and 1,10-phenanthroline were synthesized. Finally we connected them and got three different complexes, complexes 1-3. Their structures have been confirmed by NMR spectroscopy, MALDI-TOF mass spectroscopy and elemental analyses.Secondly, the photophysical properties of target platinum(?) complexes was studied. Compared with L1, MLCT and LLCT transitions were observed in UV-vis spectrum and the emissions of target complexes were assigned as originating from MLCT transition. Their self-assembly properties were studied in THF-water mixture. The solution became turbid and then clear as the water fraction increased. The absorption tails at 450 nm appeared in their UV-vis spectra of target complexes. As the water increases further, the absorption decreased obviously in 300-425 nm and showed red shift from 425 nm. That means there was J-aggregation of platinum complexes. According to emission spectra of target complexes in THF-water, the emission of platinum complexes changed from 540 nm(yellow light) to 605-631 nm(red-orange light). Unlike complex 2, complex 1 and complex 3 have a more planar structure, so that the complexes could aggregate more efficiently, then the emission wavelength originated from MMLCT of Pt-Pt interaction could become longer. According to the photophysical data, SEM and TEM experiments were performed to observe the assembly structure. It was found that complex 1 could form regular rod-like structure in the solution of THF/H2O=1:1, and complex 2 could form irregular rod-like structure, while complex 3 could not form any nano-structure. SAED experiments were also used to reveal the amorphous nature of the aggregation.At last, their liquid crystal properties were also studied. It was found that complex 2 does not show any peaks from room temperature to 220 ? in its DSC spectra, while complex 1 and complex 3 showed peaks from 154.8 ? to 21.3 ? and from 190.3 ? to 9.9 ?, respectively. Pesudo-leaf stucture of these complexes in their POM images, could be observed and supported the formation of column mesophase. In variabletemperature powder XRD data, the mesophase changed from hexagonal column phase to rectanglar column phase in cooling process. We also see there was platinum-platinum interaction in XRD data.In summary, a series of platinum(?) complexs with bipyridyl and diketonato ligands was synthesized. Their photophysical and self-assembly behavior was studied by UV-vis absorption, fluorescence, SEM, TEM and SAED experiments. It was found that Pt-Pt interaction existed in the mixture solution and showed rod-like structure. And finally, the liquid crystalline behavior was also studied and they showed column phase in their liquid crystalline behavior.