Theoretical Study Of The Stability And Electronic Spectrum Property Of Organometallic Complex With 2-(2-pyridyl) Imidazole Ligand

Luminescent organometallic compounds have been becoming the most active research focus in recent years because of their applications in electroluminescent(EL) display. Most organometallic complexes with ligands containing imidazole, benzimidazole and pyridylimidazole exhibit fine photoluminescent and electroluminescent properties, they have been paid more and more widely attention in research fields relative to photoelectric functional materials. Our group has synthesized systematically this kind of complexes and their derivatives, interestingly, crystal water can often be found existing in Zn, Cd complexes. It is well known that the prerequisite for an organometallic compound to be useful in EL devices is that it must be thermally stable and photoluminescent. While coordinated water is one of the main factors which result in low quantum efficiency in photoluminescent material. Therefore both the stability of coordinated water and the effect of coordinated water on spectral properties of Zn, Cd complexes with pyridylimdazole ligand are interesting questions.The geometry structures of twelve selected model Systems [Zn(PIm)2(H2O)], [Zn(PImH)2(H2O)]2+ ), [Cd(PIm)2(H2O)2] and [Cd(PImH)2(H2O)2]2+ etc. ( PImH= (2-(2'-pyridyl) imidazole) , PIm= deprotonated (2-(2'-pyridyl) imidazole)) are optimized by means of ab initio methods with 6-31G* basis set at HF and B3LYP level. Starting from their stable structures, the possibility of coordinated water existing in complexes is qualitatively analyzed and the interaction between metal andH2O is calculated systematically. Considering intramolecular hydrogen bond (O-H-N), binding energy of deprotonated system is close to that of protonated system, which indicates coordinated water is stable enough in complexes. Spectroscopic properties of selected systems have been investigated by time dependent density functional theory (TD-DFT). The calculation results show that coordinated water can cause blue shift in absorption spectrum and change intraligand charge transfer into inteligand charge transfer when S0-S1.