Synthesis of europium and terbium complexes as fluorescent thermosensors

Fotoluminescenca je pojav spontanega oddajanja svetlobe, potem, ko je snov pred tem absorbirala foton. Tako zajema pojava fluorescence, emisije iz singletnega vzbujenega stanja, kakor fosforescence, emisije iz tripletnega vzbujenega stanja. Na intenziteto luminescence med drugim vpliva tudi temperatura, zato se fluorofori uporabljajo tudi kot termosenzorji. Najbolj poznani so organski fluorofori, vendar na emisijo teh poleg temperature vpliva tudi koncentracija fluorofora, ki je navadno ne poznamo ali pa se zaradi fotobledenja fluorofora spreminja. Luminescenčne lastnosti pa izražajo tudi lantanidni kompleksi, med drugim evropijevi in terbijevi kompleksi. Emisijski spektri evropijevih in terbijevih kompleksov izražajo več relativno ostrih vrhov, katerih intenziteta emisije je različno odvisna od temperature, zaradi česar so boljši kandidati za pripravo termosenzorjev kot organski fluorofori. Namreč razmerje intenzitete emisij dveh vrhov ni odvisno od koncentracije, ampak le od temperature. V magistrski nalogi smo najprej pripravili ustrezne ligande, ki smo jih nato vezali na trivalentne evropijeve in terbijeve ione ter tako pripravili komplekse oziroma fluorescenčne sonde, s katerimi bi lahko merili temperaturo. Pripravili smo 1,3-diketo tipe ligandov, ki so že poznani, pa tudi ligande z iminsko in sulfonamidno funkcionalno skupino. S pripravljenimi ligandi smo nato tvorili komplekse z evropijevimi in terbijevimi ioni. Pri sintezi smo bili uspešni, kajti kar 11 izmed 16 kompleksov, ki smo jih pripravili, je izkazovalo izrazito emisijo po ekscitaciji z UV svetilko (366 nm). Terbijevi kompleksi so emitirali značilno zeleno svetlobo, medtem ko je bila za evropijeve značilna rdeča svetloba. Iz izbranih kompleksov smo poskušali pripraviti monokristale, ki smo jih nato poslali na analizo z rentgensko difrakcijo, da bi jim potrdili predvideno strukturo. Na koncu smo na izbran kompleks pripeli še sililni reagent za vezavo na steklo. Poleg tega smo pripravili sondo na osnovi evropijevega kompleksa za označevanje ogljikovih nanocevk in visoko fluoriran evropijev kompleks, ki se meša s perfluoriranimi topili in bo uporaben za označevanje perfluoriranih spojin za meritve temperature le teh.Photoluminescence is the phenomenon of spontaneous emission of light after a substance has absorbed a photon and it includes fluorescence, i.e. emission from excited singlet state, and phosphorescence, i.e. emission from excited triplet state. The intensity of luminescence is influenced by temperaturetherefore, fluorophores can also be used as thermosensors. The most well-known are organic fluorophores, the emission of these is also affected by temperature, however the concentration of the fluorophore is often not known or the concentration changes with time because of e.g., photobleaching. Besides organic fluorophores, lanthanide complexes, such as europium and terbium complexes, also emit light upon excitation. The emission spectra of europium and terbium complexes have many relatively sharp peaks with different sensitivity of emission intensity to temperature. Therefore, the ratio of emission intensity of two peaks is dependent solely on temperature, making them better candidates for development of thermosensors than organic fluorophores. In this master\u27s thesis, we first prepared the appropriate ligands, which were then bound to trivalent europium and terbium ions. We prepared already known 1,3-diketo type of ligands, as well as ligands with imine and sulfonamide functional groups. In the case of terbium complexes, ligands with less π electrons exhibited better fluorescence, while in the case of europium complexes those with more π electrons were better. We were successful in the synthesis, since as many as 11 of the 16 complexes exhibited strong emission upon excitation with UV lamp (366 nm). Terbium complexes emit green light and europium complexes emit red. We tried to prepare single crystals for the selected complexes, which were then analyzed by X-ray diffraction in order to accurately characterize their structure. Finally, a silyl reagent was attached to the selected terbium complex for coating of silica surfaces. In addition, we have prepared a probe based on a europium complex for labeling carbon nanotubes and a highly fluorinated europium complex, which is miscible with perfluorinated solvents and will be useful for measuring their temperature