Theorectical Investigation On The Organic Metal Complexes Light-Emitting Materials

Photoluminescent complexes, especially for organic metal complexes have been used in almost all fields due to their merits of high efficiency of luminescence, high stability and high brightness. Rescentlly, new demands for color and lifetime of these complexes are push forward. Experimental chemistries have done a lot to develop new photoluminescent materials, but they lack sufficient support of theory which results in the empirical understanding of the mechanism of luminescence and there is no exact direction for experimental work. In this paper, density functional theory is used to investigate these organic metal photoluminescent complexes. The ground-state geometries are optimized to obtained the steady gtructuries. The compositions of molecular orbitals, energy gaps, absorption spectra, ionization potentials, electronic affinities, and the excited stated geometries are calculated on the basis of the optimized ground state geometries. Emission spectra are calculated at the optimited excited stated geometries. From these results the interrelationship between structure and property are abtained. The theorecal results show that by modification of chemical structrure could tune and control its electronic and optical properties which can lead to the development of superior photoluminescent materials. Also, experimental chemitrists have done a lot on mechanism of firefly luminescence, now, we will investigate the reason from theorecal point of view.1. The effects of electronic and optical properties of a series of Ir complexes with the incressing conjugation of substituents are studied. The results show that with the increasing conjugation of substituents, the HOMO-LUMO gaps decrease which leads to the red-shift of absorption and emission spectra. At the same time, the increasing of conjugation can benefit the formation of hole which makes the complex with the greastest conjugation suitable for hole-transport materials.2. The electronic and optial properties of Pt(Ⅱ) complexes with 8-quionline and quinoline-8-thiol ligand are studied. Many simple PtⅡcomplexes are either nonemissive or only very weakly luminescent at room temperature, owing to the presence of low-lying metal-centered d-d excited states which are severely distorted compared with the ground state and hence subject to efficient nonradiative decay. The calculated results show that through introducting electron-releasing groups can effectively prohibit the non-radiative deactivation through the pathways of d-d transitions.3. The effects of electronic and optical properties of complexes with B as center are studied with the incressing conjugation of substituents. By introducing the ethenyl-based group as an indispensable component of theπ-conjugation system between ligand quinoline ring and substituted-phenyl ring can amplify the conjugation and the addition of NO2 group can further strengthen this effect which results in the rigid, planar structure. The increasing conjugation effect narrows the HOMO-LUMO gap which makes the spectra bands red-shifted. At the same time, this effect can both strengthen the electron- and hole-transport abilities.4. The mechanism of dioxetanone intermediate through ring-opening reaction to keto-form luciferin during bioluminescence progress is studied. The calculated results show that two reaction pathways are found about this ring-opening reaction. Path 1 proceedes in one step via a singlet transition structures with lower activation barrier, while path 2 via two transition structures with one intermediate. Path 2 is more exothermic, thus the two reaction pathways may occur at the same time when obtaining some energy.