Synthesis And Chemiluminescence Study Of Symmetrically Phenylethynyl Substituted Fused Aromatic Hydrocarbons

ChemiLuntinescence (CL) is the emission of light after excitation of a fluorescent molecule by a chemical reaction. Among a variety of CL's, PeroxyOxalate ChemiLuminescence (POCL) is well noted for its high efficiency and large intensity, and therefore is widely used and intensively studied. Among its applications are: manufacture of CL light source, post-column detector for HPLC, biochemical engineering, medical diagnosis, immunoassay, etc. A series of 9,10-Bis(PhenylEthynyl)Anthracence's (BPEA's) are among the most frequently used fluorescers in POCL system. However, the classic synthesis of these compounds employs lithium phenylethynyl, which is a highly reactive agent and requires harsh reaction conditions, making industrialization of this method difficult. Consequently, it is necessazy to develop a new route, which employs readily available raw material, enables easy operation, and meets the demand of industrialization. Considering that magnesium phenylethynyl bromide requires milder conditions than lithium phenylethynyl, and is more readily available, a synthetic route was developed in which BPEA was obtained by reacting anthraquinone with magnesium phenylethynyl bromide. Influence of reaction conditions on yields was studied and after-treatment procedure was investigated in detail to give an optimized synthetic route, which is described as following. Under N2 protection, 0.OlO3mol magnesium reacts with 0.01 lmol ethyl bromide in 20m1 THE at 45-50 t to give ethyl magnesium bromide, which is transformed into phenylethynyl magnesium bromide by adding a solution of 0.01 OSmol phenylacetylene in lOml THE at 35 C. Then add 0.OOSmol anthmquinone and 2Oml TI-IF, followed by 24h refluxing. The resulted mixture is separated into two phases, among which oil phase is treated with stannous chloride, being reduced at 20～25 C for 30～0min. A crude product of orange or yellow oil is obtained, which is then purified by a series of after-treatment procedure of extracting, solidizing, filtering, washing, second extracting, and reciystalization to give 0.0028mo1 BPEA as long orange needles, m.p.258.3～259.6C, with an overall yield 55%. Through the above-mentioned method 11 BPEA's substituted by fluorine, chlorine, bromine, methoxy and phenoxy were synthesized, among which 6 compounds have not been reported. The overall yields of these compounds range between 3 3～55%, approaching those of the lithium phenylethynyl route. The absorption spectra, fluorescence excitation spectra and fluorescence emission spectra of the synthesized BPEA's were recorded, the fluorescence quantum yield also determined. The absorption maxima of the 12 BPEA's range between 457～497nni, the fluorescence excitation maxima between 459-.SOOnm, the fluorescence emission maxima between 476?22nm, with thestOkes shift ranging betWee lM4nm. The nuorescence q-- yield of the l2 BPEA's is ashigh as 0.72ro.87, excePt for l-iodo-BPEA at 0.47 and l,8-diphenoxy-BPEA at 0'5l'There are still a few problems worth inveedgating in CL bohavior at presenL e.g., detalledCL sPecthe have never ben I'ePOrte4 nor has the relallonShip betWee CL SPeCtra andfiuorescence SPeCtra of the fiuorecer been illuStrated. The CL sPeCthe dependence on vallousconditions is also tmclear In this paPer, the method to determine the CL SPeCus was firstestablished by modifying a fl u ore scence -speCthemeteL with thi s method, th e C L behavi or of l 2BPEA's in POCL system was StUdied. The ialluence of the concendon of fluorescer, oxalate,H:O,, Catalyst edion time and solven on the shgu and mnda of CL sPecbe was aisoresearched. It was found that as the conceboon of the fiuorescer rises...