Construction And Properties Of Carbazole-Based Metal-Organic Supramolecules

Coordination driven self-assembled metal-organic supramolecules are widely used in molecular recognition,selective catalysis and enzymatic chemistry,due to the well-defined cavity and good host-guest performance.Taking advantage of directionality and reversibility of the coordination bond,the controllable transformation of the self-assembly can be achieved.How to introduce sutiable functional groups such as photochemical and redox sites that can interact with substrates and distribute them reasonably is the key to achieve the functionalization of metal-organic supramolecules.As a result of rigid conjugated structure,good fluorescence properties and easy modification,carbazole has become an ideal building block for constructing metal-organic supramolecules.In this thesis,a series of carbazole-based ligands were designed and synthesized for the construction of various controllable metal-organic supramolecules by self-assembling with specific metal ions to investigate the relationship between the structure of carbazole-based metal-organic supramolecules and the geometry of ligands.By introducing specific functional sites,the application of the supramolecular system in photocatalytic reduction of protons and CO2,molecular recognition and allosteric catalysis is realized.A series of two-arms carbazole-based ligands LA and LB with different lengths and steric hindrance were designed and synthesized to coordimaite with Ni2+ ions for the construction of various metal-organic macrocycles.The configuration transformation of the macrocycles was investigated by electrospray ionisation mass spectrometry and ion mobility-mass spectrometry.For ligands LA with less steric hindrance,as the length of ligands and the configuration transformation ability of the coordination unit gradually increased,the size of metal-organic macrocycles became larger and the species coexisting simultaneously also became more diverse.However,the configuration transformation of Ni2+ ions were limited by the triphenylphosphine groups with larger steric hindrance,so that ligands LB with different lengths were assembled with Ni2+ ions to form metal-organic macrocycles Ni-LB with a fixed configuration.Through the suitable modification of carbazole-based ligands,the controllable construction of metal-organic macrocycles with different sizes and configurations can be achieved.A carbazole-based metal-organic macrocycle Ni-SSC with planar four-coordinated configuration of Ni2+ was designed and synthesized,and the coordinated S atoms were used to adjust the redox potential of the metal center.A supramolecular host-guest system for photocatalytic reduction of protons and CO2 was constructed by encapsulating an organic dye molecule into the pocket of Ni-SSC,and the turnover number of photocatalytic reduction of protons was approximately 1,250 per mole of catalyst.In addition,the coordination of rigid carbazole-based ligands with Ni2+ ions enforced the distortion of the square planar coordinated configuration,which favored axial activation of CO2 and reduction of CO2 to HCOOH.Ni-SSC and fluorescein could form a 1:1 host-guest complexation through π-π stacking interactions to accelerate the electron transfer rate between the catalyst and the photosensitizer,which was beneficial to photocatalytic reduction of protons and CO2.A carbazole-based ligand H6BETA containing amide groups as hydrogen bonding sites was designed and synthesized to coordinaite with Ce3+ ions for the conUUollable construction of two fluorescently active metal-organic polyhedrons,which were tetrahedral Ce-BETA[4+4]and octahedral Ce-BETA[6+6].Meanwhile,the transformation from octahedron to tetrahedron could be relized by heating.The Ce-BETA with different cavity microenvironments could be matched with different nucleoside molecules,which could achieve differential selective recognition of nucleoside molecules.At the same time,Ce-BETA could work as molecular flask for prompting cyanosilylation reactions of aromatic aldehydes,showing the selective catalytic behavior based on the size of cavity.Both structures had a higher catalytic yield for the smaller substrate molecules 2,3,4-NBA.When the size of substrates increased,the catalytic yield of Ce-BETA[4+4]with a relatively small volume of cavity decreased significantly,while that of Ce-BETA[6+6]with larger windows and cavity still remained a high yield,reflecting the allosteric catalytic properties of the enzyme.