Synthesis and properties of lipophilic phosphazene-based indicator molecules
Date
2019-07-08
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Käesoleva doktoritöö peamiseks eesmärgiks oli luua grupp uudseid fosfaseenidel baseeruvaid indikaatormolekule, mille vaba aluse ja protoneeritud vormi spektrid oleksid võimalikult erinevad ja asuksid nähtavas spektrialas või fluorestseeruksid. Lisaks töötati doktoritöö raames välja uudne meetod lipofiilsete molekulide happelisuse/aluselisuse kvantiseerimiseks kahefaasilistes süsteemides. Eesmärgiks on pakkuda alternatiivset pH määramise meetodit traditsioonilisele elektrokeemilisele pH määramise meetodile, sest elektrokeemilisel meetodil on teatavaid puudujääke. Sobiv alternatiivne meetod on optiline pH määramine. Optilise pH-sensori ehitamiseks on vaja rakendada ühte või mitut erinevat niinimetatud “töölooma”, korrektsemalt öeldes, indikaatormolekuli. Inimkond tunneb mitmeid kümneid erinevaid indikaatormolekule, tuntumad neist on näiteks fenoolftaleiin, metüüloranž, tümoolsinine, alisariinkollane jne. Nende kasutamisel optilises pH sensoris on üks suur „aga“: suurem osa tuntud indikaatoritest on hüdrofiilsed (polaarsed, vees lahustuvad) ja nende protoneeritud või deprotoneeritud vormis esineb selgelt väljendunud laeng. Kirjeldatud omadustega indikaatormolekulid ei ole enamasti rakendatavad optiliste pH sensorite disainimisel, sest tavaliselt sensori ehitamisel “istutatakse” indikaatormolekul madala polaarsusega polümeermembraani. Lihtsalt öeldes, polaarsed molekulid ei istu just meeleldi madala polaarsusega polümeermembraanis. Võimaluse tekkides, sensori rakendamisel vesilahuse pH määramiseks, leostub indikaatormolekul polümeermembraanist vesilahusesse, jättes sensori “tööloomata”.
Töö käigus valmistati ja karakteriseeriti 16 uudset fosfaseenidel baseeruvat indikaatormolekuli. Näidati, et valmistatud indikaatormolekulid on sobivate omadustega, et neid rakendada optiliste pH-sensorite loomisel. Sünteesitud molekulid on tundlikud keskkonna pH suhtes, sobivad rakendamiseks keskkondades pH ˃ 7, mõlemad vormid on kõrge lipofiilsusega ja sobilikud erinevate madala polaarsusega süsteemide happelisuse/aluselisuse monitoorimiseks, sest käituvad sellistes süsteemides kui “vaiksed pealtvaatajad”.
The aim of this thesis was to design and synthesize a family of novel lipophilic phosphazene-based indicators – active both via visible absorption and fluorescence – and to create an original method for quantifying acidity/basicity of lipophilic molecules in practically water-immiscible solvents (biphasic pKa values). It is all about the purpose to offer an alternative pH determination method to the electrochemical pH sensing, since there are some drawbacks related to the electrochemical method. The appropriate alternative pH determination method is optical pH sensing. Optical pH sensor requires one or several different “work-horses”, to be more specific, the indicator molecules. There are many different pH indicators known to mankind, common examples are phenolphthalein, methyl orange, thymol blue, alizarin yellow etc. There is one big “but”: these known indicators are usually hydrophilic and have localized charges in their protonated/deprotonated forms. Therefore these indicators are not perfect for designing an optical pH sensor, since indicators are generally embedded in a non-polar polymer media. To put it simply, hydrophilic molecules do not sit very happily in a non-polar media and they leave it as soon as possible, leaving the sensor without its “work-horse”. 16 novel phosphazene-bases have been synthesized and fully characterized in this work. It is shown that these molecules have all the desired and suitable properties to employ them in the design of optical pH sensors. These molecules are sensitive to the pH, suitable to use in environments with pH ˃ 7, the both forms are highly lipophilic and can act as "silent spectators" in monitoring the acidity/basicity of different low-polarity systems.
The aim of this thesis was to design and synthesize a family of novel lipophilic phosphazene-based indicators – active both via visible absorption and fluorescence – and to create an original method for quantifying acidity/basicity of lipophilic molecules in practically water-immiscible solvents (biphasic pKa values). It is all about the purpose to offer an alternative pH determination method to the electrochemical pH sensing, since there are some drawbacks related to the electrochemical method. The appropriate alternative pH determination method is optical pH sensing. Optical pH sensor requires one or several different “work-horses”, to be more specific, the indicator molecules. There are many different pH indicators known to mankind, common examples are phenolphthalein, methyl orange, thymol blue, alizarin yellow etc. There is one big “but”: these known indicators are usually hydrophilic and have localized charges in their protonated/deprotonated forms. Therefore these indicators are not perfect for designing an optical pH sensor, since indicators are generally embedded in a non-polar polymer media. To put it simply, hydrophilic molecules do not sit very happily in a non-polar media and they leave it as soon as possible, leaving the sensor without its “work-horse”. 16 novel phosphazene-bases have been synthesized and fully characterized in this work. It is shown that these molecules have all the desired and suitable properties to employ them in the design of optical pH sensors. These molecules are sensitive to the pH, suitable to use in environments with pH ˃ 7, the both forms are highly lipophilic and can act as "silent spectators" in monitoring the acidity/basicity of different low-polarity systems.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
molekulid, indikaatorid (keemia), keemiline süntees, pH määramine