Design And Molecular Recognitions Of Novel Porphyrin Hosts

Solar energy can be utilized as a suitable and clean alternative to rapidly depleting fossil fuels. Artificial photosynthesis is an important basic research of solar energy utilization. Numerous artificial photosynthetic system is achieved by constructing various donor-acceptor (D-A) type devices first, and then studying photoinduced electron transfer property. Porphyrins, which are the naturally occurring dyes in photosynthesis, have been widely established as donors while fullerenes, such as C6o and C70, due to their unique electron accepting properties, have been considered as acceptors. Porphyrin-fullerene system is widely used to mimic electron transfer device photosynthesis. However, it’s difficult and time consuming synthesis of the porphyrin-fullerene system by covalent bonding. Moreover the fixed structure of covalent porphyrin-fullerene system makes it hard to be controlled. Therefore the development of this system has been limited. To overcome this limitation, the way of porphyrin and fullerene via supramolecular assembly has emerged.In this dissertation, a new type of porphyrin molecules containing urea structure was designed and synthesized, and systematiclly study of fullerenes and mercury ions recognition. The first part of the dissertation discusses three main aspects to the design and synthesis of porphyrin-type tripod structure of the receptor and its role in fullerene supramolecular inclusion. Then we discuss the control behaviour of such inclusion complexes by introducing H2PO4-and Ca2+, and its practical application in fullerene separation and purification. At the last part of the dissertation, we study a new Hg(II) chemosensor-β-urea-dipicolylamine substituted porphyrin Zn(II) as a Hg2+ion sensor with a high selectivity and sensitivity.1. A practical method for the preparation of novel tripodal tris(porphyrinato-urea) la (tri(2-(5,10,15-triphenyl-20-ureidoporphyrin))ethylamine, figure2.1) was readily achieved by tris(2-aminoethyl)amine bridge. This porphyrin trimer host was found to have high affinity towards fullerenes to form stable inclusion complexes in solution. A120-fold binding selectivity towards C70(Kassoc=1.81×107M-1) over C60(Kassoc=1.51×105M-1) was further achieved in toluene, which provides a theoretical guidance for fullerene separation and purification. To further investigate the nature of fullerene inclusion, UV-vis spectra, Fluorescence spectra,1H and13C NMR,2D NMR spectroscopy, IR, electrochemical measurement and DFT theoretical calculations were conducted. The appreciable pre-organized triangular cone-shaped cavity resulted from the intramolecular hydrogen bonds of tripodal trisurea backbone, was the key factor of binding fullerenes.2. Moreover, the trisurea structure is apt to recognize anions with intermolecular hydrogen bonds, which results in adjustment of cavity according to the size of anions. Therefore, the dissociation of such inclusion complexes can be easily realized by introducing H2PO4-, and a recapture of fullerene can be achieved after withdrawing H2PO4-by Ca2+. A recyclable process for inclusion and release of fullerene was therefore built by alternately feeding H2PO4-and Ca2+. This reversible process is fast and highly efficient, which indicates an ion-controlled inclusion and release of fullerenes was facilely achieved, and would be used as an ion-controlled on-off switch.3. Benefit from above facts, TP31was sequentially applied to successfully isolate C70from the C60-enriched fullerene mixture (the C70abundance up to95%can be obtained for the second circle). It is noteworthy that the easy preparation of starting material (amino porphyrin), along with the efficient synthesis of the receptor in high yield under mild conditions, make it available for accumulating TP31on a gram scale. Hence this approach should be a fast and cost-efficient way to purify C70and C60from fullerene mixtures.4. A new Hg(Ⅱ) chemosensor-β-urea-dipicolylamine substituted porphyrin Zn(Ⅱ), has been designed and synthesized. It prefers chelating Hg2+ion with a high selectivity and sensitivity to other metal ions. We also preliminary validated that the DPA group and its connection site are vitally important for the sensing and selectivity. The design stragegy of DPA (2,2’-dipicolylamine)-assisted coordination of pyrrolic nitrogen with Hg(Ⅱ) center that causes distortion of porphyrin plane, provides a new way of designing a probe for metal ion.