The Series Of Cyclic Quinacridone Derivatives: Synthesis, Structures And Luminescent Properties

H. Liebermann and co-workers synthesized 5, 12-Dihydro-quino[2, 3-b]acridone-7, 14-dione in 1935 firstly. Quinacridone (Pigment Violet 19) is the most important pigment for orange–violet shades that display excellent fastness properties, including high melting temperature, excellent optical, physical and chemical stability. Over the past decades, quinacridone and its derivatives have been investigated and known more and more, which application including dye and pigments, crystal engineering, photoelectric devices, biology probe, metal ionic sensor and supramolecular tunable self-assembly etc. Especially, high photoluminescent efficiency in dilute solution combined with good electrochemical stability in the solid state has allowed the fabrication of high performance OLEDs based on QA. A great deal of effort has been invested in the optimization of QA based devices in terms of efficiency and lifetime. Moreover, some studies on QA have been devoted to investigate the assembly and structure properties of this class of pigments. Müllen and co-workers have carefully studied the phase-formation behavior and aggregation properties of some soluble quinacridones. Nakahara and co-workers have synthesized quinacridone derivatives with alkyl chains and used them in Langmuir-Blodgett films to control the orientation and packing of the chromophores. Armstrong, McGrath and co-workers have demonstrated that dendrimerization of QA could efficiently inhibit the aggregation and self-absorption between core molecules in the solid state. We have reported that highly ordered 2-D structures based on quinacridone derivatives could be obtained at highly oriented pyrolytic graphite (HOPG). Recently, we have carried out studies aimed at understanding how supramolecular structures in the solid state and aggregation states in the solution system affect the photoluminescent (PL) and electroluminescent (EL) properties of quinacridone derivatives. It is demonstrated that molecular aggregation characteristics have dramatic effect on the spectroscopic properties of the quinacridone derivative solutions.To fully exploit the potential applications of this kind of functional compounds, it is necessary to design and synthesize some model QA compounds with special molecular structures and to understand the relationship between molecular structures and spectroscopic properties. These will enable the development of new strategies for the preparations of high performance organic optical and electronic materials. Our studies mainly focus on the four aspects:1. The spectroscopic properties of the QA dimmer aggregate is very important for understanding how the assembly structure effects the optical properties of the QA derivative systems. However, it is very difficult to measure the unadulterated spectra of the QA dimmers due to the fact that we can only obtain the mixture of monomers, dimmers and oligomers of common QA derivatives. So we designed and synthesized two cyclic dimmer quinacridone derivatives C-10C-TMQA and C-12C-TMQA, which are two typical model compounds for the spectroscopic investigations ofπ-dimeric organic compounds. The single crystal structure studies revealed that intramolecular QA-core interactions exist for the compounds C-10C-TMQA and C-12C-TMQA. The detail 1H NMR, UV-vis absorption and emission spectra studies demonstrated that in the solution systems, the intramolecular QA-core interactions dominate the spectroscopic properties of C-10C-TMQA and C-12C-TMQA. Even in dilute solutions, C-10C-TMQA and C-12C-TMQA still obviously display the intramolecular QA-core interactions, which could induce strong emission quenching and reduce the photoluminescent quantum yields. The experimental results demonstrated that the formation of the quinacridone core dimmers with enough short aromatic interaction distance could produce remarkable effect on the spectroscopic properties of the quinacridone compounds.2. We designed and synthesized six novel Basket-quinacridones, investigated their photophysical and thermochemical properties. The supramolecular structures of 1 and 5 are reported. These results indicate that the presence of the bridge alkyl chain completely inhibit the propagation of theπ…πinteraction, and there are noπ…πinteractions between dimmers due to the isolation effect of the bridge alkyl chain. Basket-quinacridones can successfully inhibit the aggregation and self-absorption between quinacridone chromophores and greatly enhance the luminescence efficiency in the condensed phases. The differential scanning calorimetry (DSC) measures indicate the good thermal properties of compounds. Based on above results, these Basket-quinacridones are a class of promising excellent photoluminescence materials.3. The new chemistry of the cyclophane-shaped quinacridone system comprising macrocyclization reaction of the versatile building block 9 to yield a new series of cyclophane derivatives 11a-d and 12 has been developed. In the whole series of quinacridone cyclophanes, the absorption and emission spectra in the visible parts are dominated by the typical quinacridone chromophore. Obviously there in no interference of the quinacridone with the spacers due to their orthogonal orientation to the quinacridone plane. With regard to the fluorescence intensity, however, a strong dependence on the different type and size of the spacers in observed.4. We have designed and synthesized the Schiff-base boron complex substituted quinacridone derivative 4. The Schiff-base of boron moieties have been introduced into quinacridone derivatives for the following reasons: (i) suppress the aggregation of quinacridone derivatives; (ii) promote the charge-transfer from boron moieties to quinacridone cores due to the overlap between the emission spectrum of Schiff-base of boron moieties and the absorption spectrum of quinacridone core. The spectroscopic studies demonstrated that the introduction of Schiff-base boron complex could increase the steric hindrance and reduce the aggregation tendency of quinacriodone chromospheres in solution. The compound 4 exhibits higher photoluminescent quantum yield in concentrated solutions than the compound 5 without Schiff-base boron moieties. The energy transfer from Schiff-base boron moieties to quinacriodone core exists for compound 4.