Synthesis, Molecular Packing, Luminescent Properties Of Quinacridone Derivatives

Organic light emitting devices (OLEDs) are of growing interest in displayapplications because they are able to emit colors throughout the visible spectrumwith high luminous efficiency. There have been extensive studies on usingmolecular organic materials to make OLEDs in order to achieve high brightness,multicolor emission, improved durability, and desired efficiency. It is well knowthat the physical and chemical properties of a molecular organic material insolid-state depend directly upon the relative orientations and spacing of theconstituent molecules. Organic molecular materials do not often reflect theproperties of individual molecules. In contrast, the molecules may form strongintermolecular interactions and the properties of these materials will be governedby the whole collective rather than by individual molecules. A fine-tuning of theperformance of molecular based devices depends on the special arrangement ofthe molecules. Therefore, it is a fundament goal to drive the molecularself-assembly toward highly ordered in solid state, reproducible, and stablesupramolecular structures. The increasing demand of new molecular organic iJilin University Ph. D. Thesis Abstractelectroluminescent (EL) materials with high performance requires the elucidationof the relationship existing between molecular packing characteristics and opticaland electronic properties. Although considerable progress has been made inorganic EL materials with different molecular structures, there is still offundamental need to understand at the molecular level the relationships betweenthe molecular packing characteristics of organic materials and the resulting opticaland electronic properties. This means designing molecular systems capable oforganizing according to well-defined supramolecular architecture in the solid statethat can be related to given optical and electronical properties. Establishing suchrelationship would open the development of new strategies towards highperformance OLEDs. Quinacridone and its derivatives (QA) are widely used organic pigments thatdisplay excellent fastness properties as well as pronounced photovoltaic andphotoconductive activity. High photoluminescent efficiency in dilute solutioncombined with good electrochemical stability in solid state has allowed thefabrication of high performance OLEDs based on the dopant emitting materials ofquinacridone derivatives. A great deal of effort has been invested intooptimization of Alq3:QA based devices in terms of efficiency and lifetime. Bycontrast, there are few of the fundament studies directed toward the molecularstructure, molecule packing, PL, aggregate properties of QA derivatives.Jones andco-workers have reported the single crystal structure of quinacridone. Recently,we reported the aggregation behavior of a series of N, N'-dialky-substitutedquinacridones at the highly oriented pyrolytic graphite (HOPG). To fully exploitthe potential of these molecules in organic materials based devices, it is necessaryto understand and if possible, to control, the supramolecular packing of a given iiThesis Abstract Jilin University Ph. D.chromophore. Recently, we have carried out the study aimed at understandinghow the supramolecular organization in the solid-state affects thephotoluminescent and electroluminescnet properties of quinacridone derivatives.Nevertheless, information on this point is crucial to tailor and eventually optimizethe PL and EL properties by altering the molecular packing modalities. These quinacridone derivatives are synthesized in this dissertation: R4 O R1 R3 N R2 R2 N...