关键词: 苯乙烯 P, 光致发光, 构象, 缔合物, 聚集体

A new chromophore tetrakis-(4,4',4",4"'-N,N-diethylamino) tetraphenyl ethylene (abbreviated as TDETE) has been synthesized and characterized by mass spectrum, elemental analysis, 'H NMR spectrum and X-ray diffraction. To understand the influence of molecular conformation upon the photoluminescence properties, absorption/ emission spectra and fluorescence quantum yield (Φ_f) as well as the emission dynamics in solution and in PMMA have been investigated. Fluorescence spectrum shows that there are three luminescent bands locating at ～ 354 nm (band I), ～434 nm (band II), and ～534 nm (band III), respectively, in toluene (1 * 10~(-6) mol·dm~(-3)) under the excitation of 308 nm. Based on a comparative study of the molecular absorption/emission spectra and of molecular structures by X-ray diffraction and computer simulation, we have confirmed that band I and band II can be assigned to two different conformations resulting from the molecular single bond rotation. Meanwhile band III is attributed to the excimer since its fluorescence intensity is directly proportional to the solution concentration, moreover, its fluorescence intensity becomes much higher in PMMA film and in PMMA rod. Since the free rotation of molecular single bonds is limited and the interaction between molecules is strengthened in the rigid medium, the luminous band II in combination with band III becomes strong and the resultant fluorescence quantum yield is increased from 0.055 in solution to 0. 855 in PMMA rod. In addition, the luminescence of molecular aggregation locating at 626 nm in PMMA rod and in PMMA film has been observed (band IV) , and it induces the intense photoluminescence with a bathochromic shift to 650 nm in powder state.

Key words: STYRENE P, PHOTOLUMINESCENCE, CONFORMATION, ASSOCIATES, AGGREGALES