Design, Synthesis And Luminescent Properties Of Organic Small Molecules/Organometallic Complexes

Organic luminescent materials have a wide range of applications in many emerging areas, suchas fluorescent probes, organic light-emitting materials, field-effect transistors, logic gates, lightharvesting system and so on. It is of great significance to develop organic luminescent functionalmaterials. In this dissertation, the main task is to design and synthesize organic small molecules andorganometallic complexes to meet the requirements as fluorescent probes, pH-induced luminescenceswitch or light-emitting materials. The specific contents of this dissertation are presented as follows:Two new Schiff base derivatives{2,2’-diphenyl-N,N’-bis（2-pyridylmethylene）biphenyl-4,4’-diamine}（1） and{2,2’-diphenyl-N,N’-bis（salicylidene） biphenyl-4,4’-diamine}（2） have been synthesized andcharacterized by means of elemental analysis,1H NMR, FT-IR. The molecular structure of the secondcompound has been determined by X-ray single crystal analysis. The analyses of fluorescenceproperties of the compounds revealed that both of them are poorly fluorescent and displayed sensitivefluorescence responses to24kinds of monovalent, divalent, and trivalent metal ions inCH3CN–DMSO （9:1, v/v）. Results with compound1showed that Fe³⁺, Cu²⁺, Zn²⁺, Cd²⁺, Mn²⁺, Zr⁴⁺,Hg²⁺, Cr²⁺, Pb²⁺, Sn²⁺, Bi²⁺, Al³⁺, Ce³⁺, La³⁺, Sm³⁺, Gd³⁺, Nd³⁺, Eu³⁺and Dy³⁺yielded red shifts inemission and increases in intensity. And the greatest spectral changes for compound2includedenhancements in emission intensity coupled with red shifts (Zr⁴⁺, Sn²⁺, Al³⁺and Zn²⁺). Thefluorescence enhancement mechanism of the compounds for metal ions has been studied as well.Five new transition metal complexes, formulated as [Zn（DMBPIP）₃]（PF₆）₂（3a）,[Ni（DMBPIP）₃]（PF₆）₂（3b）,[Co（DMBPIP）₃]（PF₆）₂（3c）,[Fe（DMBPIP）₃]（PF₆）₂（3d）,[Ru（DMBPIP）₃]（PF₆）₂（3e）{where DMBPIP=2-（3’,5’-dimethoxybiphenyl-4-yl）-1H-imidazo[4,5-f][1,10]phenanthroline,3} have been synthesized and characterized by means of elemental analysis,FT-IR,1H NMR,13C{1H} NMR. The pH effects on UV-vis absorption and luminescence spectra ofthe Zn（Ⅱ） and Ru（Ⅱ） complexes have been studied, and ground-and excited-state ionization constantsof the two complexes have been derived. The two complexes acting as pH-induced “off–on–off”luminescence switches through protonation and deprotonation in buffer solution at room temperaturehave been studied and discussed as well.N,N′-di（quinolin-8-yl）pyridine-2,6-dicarboxamide （H₂L,4） and its complex Zn₂L₂（4a）, havebeen synthesized and structurally characterized by elemental analysis,1H-,13C{H}-NMR, FT-IR and UV-vis spectroscopy, respectively. X-ray crystallography revealed that4a is a dinuclear doublehelical complex, in which partitioning of the ligand into two tridentate domains allows each ligand tobridge both metal centres. Fluorescence spectra measurements revealed that the ligand H₂L exhibits abroad emission band at406nm and the complex4a shows stronger emission at468nm, indicating4amay be a potential blue-emmiting material.Three novel ligands5-（3,5-dimethoxyphenyl）-1,10-phenanthroline （DMPP,5）5-[4-（9H-carbazol-9-yl）phenyl]-1,10-phenanthroline （CPP,6）5-[4-（naphthalen-1-yl）phenyl]-1,10-phenanthroline （NPP,7） and relative transition metal complexeshave been synthesized and characterized by means of FT-IR,1H NMR,13C{1H} NMR, elementalanalysis. UV-vis and luminescence spectra at room temperature revealed that the Zn（Ⅱ） complexesemit cyan fluorescence in the range of412547nm, the Ru（Ⅱ） complexes emit orange luminescencein the range of582605nm, the emission of the complexes are red shifted compared with the freeligands, and the complexes [Zn（DMPP）₃]（PF₆）₂（5a） and [Ru（DMPP）₃]（PF₆）₂（5f） exhibit significantsolvatochromism.On the basis of the above researches, a series of organic small molecules/organometalliccomplexes that can be used as fluorescent probe, pH-induced luminescence switch, or organiclight-emitting materials were obtained.