Synthesis And Ion Sensing Properties Of Novel Linear And Cyclic Oligopyrroles And Polypyridyl Ligands

The detection of ions such as Zn2+and CN is a subject of great importance in the areas of biochemistry and environmental science. Fluorescent probes have the advantages of low cost, ease of performance and high sensitivity, thus attracting increasing interests in recent years. The chromophores of fluorescent probes are usually constructed from simple five-or six-membered heterocyclic units. Pyrrole is a five-membered heterocycle, which can react with aldehydes to form dipyrromethanes, tripyrromethanes and other linear oligopyrroles, which have been used as intermediates in porphyrins synthesis. However, their applications as fluorescent probes have not caused much attention. In consideration of their potential emission capacity, coordination ability and ease of modification, this thesis is focused on the systematic investigations of the novel oligopyrroles that can be applied as practical Zn2+and CN-probes. Furthermore, considering the fact that polypyridyl ligands are also widely used in metal chelation, their applications as fluorescent probes were also investigated.In Chapter1, common sensing principles of fluorescent probes are briefly introduced and the recent progresses in zinc and cyanide probes are also reviewed.In Chapter2, meso-pentafluorophenyl substituted dipyrrins D1-D3and tripyrrin D4were readily synthesized and developed as fluorescence turn on Zn2+probes with emission colors varying from green to red. The fluorescence enhancement can be ascribed to the formation of corresponding zinc complexes, which show the "CHEF" type fluorescence. D1～D4can be applied to selectively detect Zn2+in aqueous systems, with the best detection limits of4.6×10-8M. In addition, D4was also successfully applied to image Zn2+in living KB cells.In Chapter3, we tried to improve the sensing behavior of the dipyrrin probes by changing the substituents at the pyrrolic a-position. During the acylation of5-pentafluoro-phenyldipyrromethane by a Friedel-Crafts reaction using p-anisoyl chloride as the acylating agent, an a-, β’-diacylated product PS2was unexpectedly obtained in high yield accompanied with ordinary a-substituted mono-and diacylated products PS1and PS3. After oxidation of PS1-PS3to dipyrrins S1-S3with DDQ, they show fluorescence "turn on" upon addition of Zn2+in water-containing systems. Compared with D1-D3, the novel a-,β’-diacylated dipyrrin S2show a longer emission wavelength and higher sensitivity for Zn2+detection.In Chapter4, three novel meso-hydroxyl substituted dipyrromethanes DPMOH1-DPMOH3were unexpectedly obtained during the oxidation of dipyrromethanes bearing electron rich substituents at the meso position. Due to the interruption of the conjugated π system by an sp3carbon between the two pyrrolic units, they were found to be colourless and nonfluorescent. Interestingly, upon addition of Zn2+to their solutions, bright orange fluorescence was observed due to the oxidation of DPMOH1-DPMOH3to corresponding dipyrrins followed by the formation of zinc complexes.In Chapter5, for the detection of CN-, three dipyrrins DCN1-DCN3were designed and synthesized. In pure organic solvents, the addition CN-induced a color change from light yellow to pink, while the color changed to orange upon addition of F-. In water-containing systems, DCN1-DCN3showed no response to F-, but the addition of CN-changed their solution color from light yellow to red. These observations can be rationalized by the fact that the hydrogen-bonding interactions between F-and the hosts was greatly suppressed in water-containing systems, but the nucleophilic addition of CN-was not obviously affected.In Chapter6, three highly fluorescent compounds ACN1-ACN3were synthesized by linking strongly emissive anthracene unit to a Cu2+chelating2.2’-dipyridylamine moiety. The fluorescence of ACN1and ACN2can be easily quenched by the formation of non-fluorescent ACN1-Cu2+and ACN2-Cu2+ensembles, which can be applied as reversible and sensitive fluorescence turn on cyanide probes, with the best detection limit of2×10-1M. In contrast, a large molar excess of Cu2+is required to quench the fluorescence of ACN3. which is unsuitable for the detection of CN-. These results demonstrate that the linking modes between anthracene and2,2’-dipyridylamine have a great influence on their sensing properties, offering a designing strategy for relevant fluorescent CN-probes.In Chapter7, with the purpose to realize multilple stable states, a relatively unsymmetrical novel dioxoporphyrin named DPH22was synthesized, which show a phenolic form (DPH22) in CHCl3with a nearly planar arrangement of the macrocyclic moiety, and transformed into the quinoidal form (DPH40) by adding a small amount of DMSO. accompanied with the distortion of the macrocyele to a nonplanar conformation. Besides, the interactions between DPH22and acid/base lead to reversible protonation and deprotonation processes. Based on these transformations, two half subtractors and a comparator were successfully constructed by using the addition of TFA and TBAF as the inputs, and the absorption values at412.510.562and603nm as the outputs.Chapter8summarized the utilization of oligopyrroles as ion probes with an outlook on their further applications in related areas.