| Summary: | 博士 === 國立清華大學 === 化學系 === 103 === Benziporphodimethenes with different functional groups (-H, -COOMe, and -NO2) on the para position of the meso-phenyl rings were inserted with a d10 metal ion in order to tune the metal-arene interaction. According to the 1H NMR study, the strength of the metal-arene interaction can be correlated to the acidity of the central metal ion: an increased electron withdrawing ability resulted in stronger metal-arene interaction. Although all of the reported solid state crystal structures of the metal complexes show a syn conformation, a crystal containing mixture of syn- (about 90%) and anti-conformation (about 10%) was obtained from the zinc complex of meso-methylbenzoate substituted benziporphodimethene. It is confirmed that the syn-anti conformational exchange for these metal complexes goes through the axial ligand dissociation and re-association. Theoretical calculations revealed that the anti conformation can be stabilized by intermolecular hydrogen bonding interactions between the axial chloride and solvent molecules.
These benziporphodimethenes can specifically turn on fluorescence at 672 nm upon coordination with Zn2+. The detection limit is 48 nM. In vitro zinc ion sensing in Zn2+ enriched Hela cells was performed using a water soluble benziporphodimethene. Confocal images demonstrated that the water soluble benziporphodimethene stains the whole cell including the cytoplasm and nucleus.
The water soluble benziporphodimethene was found gradually to undergo a water addition reaction to transform into an amino nitrogen protonated and meso-carbon hydroxylated species in aqueous solution. This newly formed species and the original benziporphodimethene are in equilibrium in solution with equilibrium constants of 0.84 at 298 K and 0.16 at 348K. The newly formed species was found showing low affinity and having no fluorescence in contact with the zinc ion. Dehydration back to the original benziporphodimethene can be readily achieved by subsequent treatment with acid and base.
Tripyrrinone was synthesized to provide a Zn2+ sensor with higher binding affinity and a 30-fold enhancement on the binding affinity toward Zn2+ than benziporphodimethene has been detected. For the cellular zinc ion sensing, tripyrrinones only showed fluorescence turn-on in the cytoplasm without penetrating into the nucleus. Fluorescence quantum yield of the tripyrrinone dyes were found strongly dependent on the dynamic motion of the meso-substituent. The dynamic rotation of the meso-phenyl rings seriously quenches the fluorescence quantum yield to 4%; while replacing the phenyl rings with bulky mesityl or 2,6-dichlorophenyl rings, the fluorescence quantum yields increase to about 90%. Besides, in a non-coordinating solvent, the tripyrrinone zinc complexes assemble to form a dimmer or a tetramer structure with weak fluorescence. While in coordinating solvents, the monomer geometry exhibits much stronger fluorescence.
The 14-benzoyl-tripyrrinone cobalt complex is designed for nitric oxide (NO) sensing. The coordination of NO to the cobalt center has been proved by the IR, 1H NMR, and UV-Vis spectroscopy; however, there was no fluorescence turn-on observed. Another lysosome targeting NO sensing dye, 3,4-diamino-N-(2-morpholin-4-yl-ethyl)-benzamide, was developed based on the sensing of the diaminoaryl to the NO derivative, N2O3. This probe shows strong emission at 387 nm in THF, and the fluorescence will be quenched upon the reaction of the dye with NO in aerobic condition. While in aqueous solution, a blue shift of fluorescence from 443 to 376 nm is observed from the same reaction.
We have also developed a lysosome-targeting-naphthalimide-based Roussin’s red ester as a NO donor. The NO can be released upon irradiation with blue or green light. After NO releasing from the diiron center, further irradiation will promote the oxidation of the naphthalimide-thiolate to form disulfide dimmer and turn on the fluorescence. The fluorescence turn-on phenomenon is proved to be the signal for the releasing of NO.
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