胺类对α-溴代萘/β-环糊精体系流体室温燐光的影响

Effects of Amines on Room Temperature Phosphorescence α -Bromonaphthalene/β-Cyclodextrin System

首次研究了不同的胺对α-溴代萘(α-BrNp)/β-环糊精(β-CD)体系RTP发射的影响.发现胺能显著增强α-BrNp/β-CD体系的RTP,发射,RTP强度随着胺的烷基链的增长和支链的增加而增加,且当胺的用量是β-CD用量的一倍时,RTP强度最大.由此认为、胺的影响主要应归因于胺分别从β-CD的二端接近,胺的-NH_2基与β-CD的-OH基形成氢键,而其烷基从CD二端折向空腔,封住了CD的上、下端口.这不仅提高了CD腔内的疏水性,增大了发光体与CD间的包结常数,同时,对外部氧向CD腔内的扩散起着隔离作用,显著减小了三线态氧对腔内发光体激发态的猝灭作用.从而可在不除氧的条件下观察到发光体强的RTP,发射,且体系清澈透明.胺的作用属于超分子化学中的分子调控作用.

β-Cyclodextrin (β-CD) can induce directly α-Bromonaphthalene (α-BrNp) to emit room temperature phosphorescence(RTF) due to protective action of CD, the maximum wavelength λex/λem = 282/500,526 nm. When t-butylamine(t-BuNH2) is presented as a third component, the RTP intensity of the system is enhanced obviously. Effect of different amines (ethyl, n-propyl, n-butyl and t-butyl amine) on RTP emitting of system was studied and the enhanced effect of t-butyl amine was the highest. The results suggested that the amine bonded to the rim of the CD cavities by hydrogen bonding and the alkyl end of amine fliped over the two tops of CD due to hydrophobic interaction force. Accordingly, the amine acted as a lid for CD cup, there by shielding luminophor from oxygen and decreasing the collision quenching of oxygen. At the same time, the hydrophobicity of the CD cavity was enhanced so the formation constant of inclusion complex was more bigger. As a whole result, the RTP of the system was enhanced. The results also showed that α-BrNp/β-CD/t-BuNH2 was transparent and the RTP intensity without deoxygenating was linear to the α-BrNp concentration in the range of 2.0 × 10-6 - 2.0 - 10-5 and 2.0 × 10-5 - 2.0 × 10-4 mol/L respectively. The detection limit was 8.3 × 10-8 mol/L. We can see that the system studied is a typical supramolecular assembly one and the amine acts as a molecular regulation for RTP emitting.