| Dendrimers are regularly and hierarchically branched macromolecules with numerous chain ends all emanating from a single core. The unique architecture of dendrimer makes it as a host to encapsulate guest molecules, which developed lots of applications in host-guest chemistry and molecular catalysis. Molecular encapsulated in dendrimers offen show some different behaviores.In this dissertation, carboxylic acid terminated poly (aryl ether)dendrimers Gn (n = 1-4) were synthesized by Fréchet's method. The microenvironment polarity of these dendrimers in basic aqueous solution (PH > 9) were studied by pyrene, anthracene and nile red as the fluorescence probes. The alkene photosensitized oxygenation, theα-cleavage reaction of asymmetric dibenzyl ketone and the photo-dimerization of 9-substituted anthracene were investigated with these dendrimers as microreactors.1. Synthesis of dendrimers Gn and substrate molecules used in phopysical or photochemical studies. Carboxylic acid terminated poly (aryl ether)dendrimers Gn (n = 1-4) were synthesized by a convergent method. All the intermediates and the target compounds were characterized by IR, 1H-NMR and MS (EI or MALTI-TOF). Substrate molecules, 1-phenyl-3-(p-tolyl)-propanones (CH3-DBK), anthracene cation derivative An, 9-methylanthracene, and 9-anthracenemethanol were also synthesized and characterized. 2. Studies of dendrimer microenvironment by fluorescence probes. Pyrene, nile red and An were used as fluorescence probes to investigate the microenvironment polarity of dendrimer Gn potassium aqueous solution, the effect on the solubility enhancement for hydrophobic molecules, and the encapsulation of An. It is indicated that the microenvironment polarity of Gn is lower than water, G2-G4 have similar microenvironment polarity, and the polarity of G1 inner cavity is obviously lower than others. The solubility of nile red increases 3, 35, 47 and 215 times than that in water for generations 1-4, respectively, which demonstrates that G4 takes a more close spherical shape with a much better encapsulation capability. Dendrimer G2 can encapsulate more than two An molecules, and the hydrophobic anthracene moiety and the hydrophilic cation portion of An encapsulated within G2 prefer to locate in the interior and the exterior of dendrimer, respectively.3. Selective control on the photosensitized oxidation of alkenes with dendrimers as microreactor. Dendrimers Gn were used as microreactors to successfully control the pathways of the photooxidation of trans-stilbene (TS) and trans,trans- 1,4-diphenyl-1,3-butadiene (DPB) sensitized by 9,10-dicyanoanthracene (DCA). Only the products via the electron transfer pathway were produced, while the product via the energy transfer process for the photosensitization oxidation of DPB is exclusively suppressed within higher generation dendrimers.4. Cage effect of dendrimers in aqueous solution. The cage effect of Gn potassium aqueous solution calculated by theα-cleavage photoreaction product distribution of substituted dibenzyl ketone was 14%, 18%, 22% and 42% for generations 1-4, respectively, which indicates that G4 takes a more close spherical shape with strong confine ability. The cage effect of PAMAM dendrimers with 12 carbon alkyl core PGn (n = 1-3) was 8%, 8% and 12%respectively, which is only a little higher than in water solution 6%. The more flexible backbone of PAMAM may be responsible for this difference.5. Regioselectivity control of the photocycloaddition of 9-substituted anthracenes in dendrimer microreactor. Photocycloaddition of 9-anthracenemethanol resulted in ~4% head to head (H-H) dimer in water, G1 and G2 potassium aqueous solutions, and 35% and 52% in G3 and G4 potassium aqueous solutions, respectively. Photocycloaddition products distribution of 9-methylanthracene in Gn potassium aqueous solutions has no difference with that in water. We infer that the regularly arrangement of 9-anthracenemethanol driving by the polar substitute group enhances the photodimerization regioselectivity in G3 and G4.
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