Hemicryptophanes And Beyond:Synthesis,Recognition,Molecular Machines And Supramolecular Catalysis

In the wide area of host-guest chemistry,hemicryptophanes,a type of molecular cages,combining a cyclotriveratrylene(CTV)unit with another different Cs symmetrical moiety,have received increasing attention.In the first part of this PhD thesis(Part ?),the advances in hemicryptophane chemistry have been thoroughly reviewed in Chapter 1.This includes a brief history of its development,the synthetic methods,and applications in recognition,molecular machines and supramolecular catalysis.In Chapter 2,the objectives of this thesis have been postulated.This PhD work outlines my efforts to design and synthesize new hemicryptophanes for more efficient molecular recognition and supramolecular catalysis.The works in Part ? mainly describe the targeted molecular recognition by rational design of hemicryptophanes.Hence in each chapter,the synthesis has been included.In Chapter 3,a fluorescent hemicryptophane cage combining a CTV unit,three naphthalene rings,and a Zn(?)metal center has been developed as the first fluorescent sensor for choline phosphate in competitive media.The heteroditopic character of the host that leads to strong guest encapsulation has been systematically investigated by both fluorescence and NMR spectroscopy.In Chapter 4,two new hemicryptophanes bearing fluorinated aromatic linkers have been synthesized,and their complexation properties toward ion pairs have been investigated and compared to that of the host without fluorine atoms.We anticipate that the introducing of fluorine atoms around the aromatic linkers could improve the anion binding abilities of the host due to the enhanced anion-? interactions,therefore affecting their ion pair binding performance.Chapter 5 has introduced the synthesis of two new heteroditopic hemicryptophanes bearing tris(2-pyridylmethyl)amine(TPA)units,one with phenyl rings as linkers and the other with naphthalene rings.The racemate of each hemicryptophane can be resolved by chiral HPLC to obtain their enantiopure forms.These enantiopure cages are expected to show interesting stereorecognition properties after metal complexation of TPA.In Chapter 6,we have designed and synthesized eight enantiopure cages combining three classes of chirality on seven stereogenic units.A chemical correlation strategy has been used to determine the absolute configuration of the eight hemicryptophane stereoisomers.The stereoselective recognition properties toward carbohydrates have been investigated.In Part ?,the only chapter,Chapter 7,describes the breathing motion of a series of enantiopure cages obtained in Chapter 6,complementing the rare application of hemicryptophanes in molecular machines.The breathing motion is initiated by vanadium coordination to a series of imploded cages,which inflates the cages to globular forms.The resulting vanadium cores can also be removed from the inner cavity according to external coordination with triethanolamine.Thus,the system is capable of switching between the imploded and expanded bistable states via external inputs,simulating breathing molecules.In Part ?,three works related to hemicryptophanes for supramolecular catalysis have been discussed.In Chapter 8,the hemicryptophane vanadium(V)complexes,obtained in Chapter 7,have been developed as efficient supramolecular catalysts for sulfoxidation.The specific shape of the confined hydrophobic space above the metal center induced by the bulky binaphthol linkers leads to strong improvement of the yield,the selectivity and also the catalytic activity.Chapter 9 deals with the catalytic lignin oxidation by these vanadium(V)hemicryptophane catalysts.Compared to the model catalyst with an open structure,an improvement of the catalytic activity associated with a diastereoselective conversion of substrates has been observed.In Chapter 10,we have attempted to develop the azaphosphatrane-functionalized hemicryptophanes as hydrogen-bonding organocatalysts for the ring-opening polymerization of lactide.However,a low reactivity has been observed.Nevertheless,the model catalysts have shown satisfied catalytic behavior.In Part V,my attention has opened to a more prospective view focusing on cages constructed by self-assembly.In Chapter 11,we have demonstrated the feasibility of introducing azaphosphatranes,the units mentioned in Chapter 10,into tetrahedron capsules using subcomponent self-assembly,and also proved for the first time the utility of azaphosphatranes as anion binding moieties.Except Chapter 2,which outlines the objectives of this thesis,all the other chapters have been prepared as manuscripts for journals,in which Chapters 1,3,4,5,6,7,8,10 and 11 have been published,and Chapter 9 is being prepared.Therefore,each chapter is based partially on the corresponding manuscript.