Synthesis And Properties Study Of Pentamethine Pyrylium Dyes

Methine cyanine dye is one of the most important organic synthetic dyes. Due totheir high molar extinction coefficient and special maxima absorption which extendsfrom visible region to infrared, methine cyanine dyes have been found wideapplication in the fields of biological detection, collide-pulse mode-locking dyes, laserdyes and so on. In this thesis, a serie of pentamethine pyran cynaine dyes wasdesigned and synthesized and their synthetic process and spectra were studied indetail to accumulate data for further application in infrared region.Firstly, benzopyran-salt-type heterocyclic groups were synthesized viacross-aldol reaction, micheal reaction and cyclization reaction with benzaldehyde andacetophenone as the starting materials. One benzothiapyran-salt-type heterocyclicgroup was obtained from benzopyran–salt-type heterocyclic group was used viareplacement reaction. Then N-[5-（Phenylamino）-2,4-pentadienylidene]anilinemonohydrochloride and2-chloro-1-formyl-3-hydroxymethylene cyclohexene weresynthesized as Condensing the condensing agent. Finally, six pentamethine pyrancyanine dyes were produced by reacting heterocyclic groups and the condensing agent.Three of them have not been reported before.Secondly, the transmission absorption spectra of the synthesized dyes were testedby UV-3600. Results show that the maximum absorption wavelength of all six dyes isabove900nm. When hydrogen atom on the4-phenyl was substituted by Methoxygroup, the maximum absorption wavelength of straight-chain pentamethine cyaninedyes increases by10nm, while that of the bridged pentamethine cyanine dyesincreases by75nm. However, if the chlorine atom was replaced with hydro gen, ablue-shift of the maximum absorption wavelength was found.In addition, the reflective spectra of the synthesized dyes were also investigated.No any characteristic peaks appear in the spectra for the powder dye samples and thedye-dispersed polymeric membranes. Only when dye-in-CH₂Cl₂solutions were used,the obtained spectra exhibit similar characteristic absorption in comparison with thetransmission absorption spectra.In the last, microcapsules were prepared with the1,2-dichloroethane solution ofpentamethine cyanine dye6-4as the core and urea resin as the shell. The reflection spectrum of the microcapsules shows characteristic absorption of dye6-4. Thisindicates that microencapsulation method could maintain the infrared-absorptioncharacter of pentamethine cyanine dyes, which extends its applications.