二(2-苯基-8-羟基喹啉)锌和喹啉锌的合成和荧光性质

Synthesis and Fluorescence Properties of Bis(2-phenyl-8-hydroxyquinolato)zinc and Bis(8-hydroxyquinolato)zinc

合成了一种新型二 (2 苯基 8 羟基喹啉 )锌配合物。利用元素分析、红外吸收光谱等方法表征了结构 ,并对比研究了二 (2 苯基 8 羟基喹啉 )锌和喹啉锌的荧光性质 ,前者的激发光谱在 4 6 5nm处出现了较强的吸收 ,并且发射峰位置发生了明显的红移 ,由喹啉锌的 4 95nm移至 2 苯基 8 羟基喹啉锌和喹啉锌的 5 2 1nm处。对有关的吸收峰的归属进行了讨论 ,初步认为苯环的取代增加了有机配体π π键的共轭程度 ,使HOMO LUMO之间能隙变小 。

Since the first reports of efficient electroluminescence from an organic thin film device using the metal chelate tris(8-hydroxyquinoline)aluminum (Alq_3) as the emissive layer materials, some efforts have been devoted not only to tailor emission wavelength by a functional group introduced onto the quinolinolato ligand, but also to synthesize the new metal chelating compound. However, there is no report on the relationship between the substituent of phenyl moiety in the 2-position of 8-quinolinol and an emission property. Therefore, a systematic study to clarify a relationship between a molecular structure and emission property is evidently necessary for developing a more useful emissive compound. Bis(2-phenyl-8-hydroxyquinolato)zinc and bis(8-hydroxyquinolato)zinc were synthesized firstly according to the relating reference. The melting point, composition and structure were also determined by a series test methods. The substituent of phenyl group dependence of luminescence band of the 8-quinolinolato anions was systematically investigated with excitation spectra and emission spectra of prepared samples. The luminescence band at 495 nm for bis(8-hydroxyquinolato)zinc is presented under 225, 283, 348, 395 nm excitations, respectively. The luminescence band at 521 nm for bis(2-phenyl-8-hydroxyquinolato)zinc is presented under 225, 283, 348, 395, 465 nm excitation, respectively, which showed to exhibit strong photoluminescence efficiency. It is suggested that the assignment of absorption bands at 225, 283, 348 nm of the above mentioned two samples could be ascribed to the β,ρ and α band of π→π~* transition in the quinolinolato ring. The absorption bands at 395 nm existing in the above mentioned two samples have been probably attributed to the charge transfer between the d orbital on zinc ion and vacant π orbital on the ligand. The new absorption band of 465 nm presented in bis(2-phenyl-8-hydroxyquinolato)zinc chelate is a new energy level ascribed to the intramolecular charge transfer between the different conjugating π systems existed in the quinolinolato ring and in the substituent of phenyl moiety in the 2-position of 8-quinolinol, which also means that this new chelate exhibits photostimulated luminescence not only with ultraviolet radiation, but also visible light at room temperature. It is suggested that introducing the substituent of phenyl moiety in the 2-position of 8-quinolinol is an effective way for red shifted emission, which changes the energy level of the highest occupied molecular orbital (HOMO) through π orbital interactions. Further, insight into the detailed mechanism of photostimulated luminescence from bis(2-phenyl-8-hydroxyquinolato)zinc chelate requires additional experimental and theoretical studies. Industrially the photostimulated luminescence phenomenon of the detailed mechanism of photostimulated luminescence from bis(2-phenyl-8-hydroxyquinolato)zinc could have use as a new type fluorescent material for optical memories and organic light emission devices.