Synthesis Of Novel Gallium And Indium Coordination Polymers Containing Multiple Ligands For Luminescence Characteristics

In order to achieve the objective of design and synthesize, we have mainly studied the syntheses, crystal structures and the luminescent properties of gallium and indium blue light emitting materials. In this work, different types of aromatic carboxylic acids are selected as main ligands, phenanthroline and bipyridine containing nitrogen are employed as auxiliary ligands. In these mixed ligands systems, two organic small molecular crystals, five mononuclear or binuclear indium complexes, five gallium and indium coordination polymers have been hydrothermally synthesized. They are structurally analysized by X-ray single crystal diffraction, elemental analyses, IR spectrum and powder X-ray diffraction. Their performances have been measured by thermal gravimetric(TG) analyses, solution and solid fluorescent analyses. The influence of synthetic conditions on the crystal structures has been analysized, also the relationship between crystal structures and luminescent properties has been studied.In the preliminary experiment, 4-(1H-Imidazol-1-yl) benzoic acid(HIBA) and 3,3’,4,4’-benzophenonetetracarboxylate(H4bptc) are selected as main ligands, 2-hydroxyl-1,3,5-tricarboxylic acid(H4OTBA) and phenanthroline(phen) are employed as auxiliary ligands, two organic molecular crystals(HIBA)(H4OTBA)(1) and(H4bptc)(phen)(2) have been synthesized under hydrothermal conditions. These two crystal structures are stabilized by hydrogen bonds and π–π interactions, forming a three dimentional supramolecular net and a two dimentional layer structure, respectively. Compound 1 exhibits intense green luminescence in solid state at 298 K(λem = 546 nm), and 2 displays unusual white fluorescence(420–566 nm).In the following research, 3,3’,4,4’-benzophenonetetracarboxylate(H4bptc) and 2,6-pyridine dicarboxylic acid(2,6-H2pydc) are selected as main ligands. Five new complexes with multiple-ligand formulated as [In(phen)2Cl2](H4bptc)(NO3)(H2O)(3), [In(Hbptc)(phen)(H2O)]2(4), In(2,6-pydc)(phen)(H2O)Cl(5), and {[In(2,6-pydc)(Ox)0.5(H2O)2](H2O)}2(6), In3(2,6-pydc)3(1,4-bda)1.5(H2O)6(7) have been synthesized under hydrothermal conditions. Complexes 3–7 have strong blue fluorescent in solutions, the maximum emission peaks are in the range of 398–435 nm. The quantum yields of complexes 3–6 in dimethylformamide, acetonitrile, methanol and chloroform are enhanced with the increase of solvent polarity, the maximum values reach 0.174, 0.207, 0.155 and 0.193, respectively. In the solid state, binuclear complex 4 possesses strong green emission, and complexes 3, 5, 6, 7 still show blue emission. The thermogravimetric curves show that complexes 3–7 are stable with the temperatures up to 117 °C, 190 °C, 174 °C, 272 °C and 250 °C, respectively.The introduction of linear 1,4-benzenedicarboxylic acid(1,4-H2bda) in the reaction system leads to form two new one-dimensional indium coordination polymers(CPs) formulated as {[In(1,4-bda)1.5(phen)]·2H2O}n(8) and {In(1,4-bda)(2,2’-bipy)Cl}n(9)(1,4-H2 bda = 1,4-benzenedicarboxylic acid; phen = 1,10-phenanthrolin; 2,2’-bipy = 2,2’-bipyridine). Coordination polymer 8 exhibits one-dimensional ladder chain, and produces blue emission in the solid state at 298 K. As the solvent polarity increases, the maximum emission peaks of 8 are blue shift(434â†'370 nm), exhibiting the characteristics of solvatochromism. It is noted that there is unusual vertical cross configuration in coordination polymer 9. Compared to 8, this fascinating cross architecture leads to much compact structure. The different polarities of solvents do not alter the PL peak position of 9.Two rare Ga(III) and In(III)-based two-dimensional CPs {M[(2,2’-bpda)(1,4-bda)0.5(phen)]·0.5H2O}n(M = Ga, 10; In, 11) are synthesized with 1,4-benzenedicarboxylic acid(1,4-H2bda), 2,2’-biphenyldicarboxylic acid(2,2’-H2bpda) and phenanthroline(phen). The CPs 10 and 11 exhibit strong blue light emission, with emission peaks at 413 nm and 401 sh,413,436 sh nm. The CPs exhibit tunable fluorescence from blue, green, white to yellow light by varying the temperatures and solvents. The quantum yields of 10 and 11 in methanol are 0.273 and 0.257, respectively, and their fluorescence lifetimes in deuterated solvent increase significantly. To gain insights into the nature of photophysical properties, TD–DFT theoretical calculations on their energy levels are performed. It suggests that the emissions observed in CPs 10 and 11 originate exclusively from ligand-to-ligand charge transfer(LLCT).The dinuclear complex 7 is used as a precursor to form the 3D MOF {[In4/3(μ2-OH)(2,6-pydc)(1,4-bda)0.5(H2O)]·2H2O}n(12). 12 exhibits blue light emission at 351 sh, 421 nm, and generates stable blue emission in different suspensions with nearly invariable maximum emission peaks(432–436 nm). Due to the rare compact 3D structure formed from 2D+3Dâ†'3D, the crystals of 12 exhibits exceptional chemical stability. The thermogravimetric curve and variable-temperature X-ray powder diffraction(VT-XRPD) show that 12 starts to undergo phase transition on 450 °C. Such a high thermal stability is mainly due to the compact and stable 3D coordination framework. Adding DMSO into H2 O suspension of 12 leads to a decrease of fluorescent intensity, which almost disappears at the DMSO content 25 vol%.