Derivation Of Oxacalixarene And Study Of Host-guest Recognition Properties

Oxacalixarene is the change of subgroup of bridge link to oxygen atoms and introducing pyrimidine to replace a class of cup aromatic hydrocarbons constructed by the benzene ring.The modification of calixarenes into structures with oxygen atoms and pyrimidine not only increases the active sites that calixarenes can chemically modify,but also shows excellent selectivity in the recognition of guest molecule(e.g.fullerene neutral molecules and metal anion).Fullerene C₆₀ has low recombination energy,high electron affinity and easy to form interpenetrating grid structure with electronic donor materials.It has been widely used in solar cells and organic superconductors.At present,fullerene materials are mainly modified by covalent bond connection to improve the efficiency of charge and energy transmission.However,it is found that the internal filtration effect at high concentration and the energy reverse transfer in covalent bond connection can reduce the transmission efficiency.If supramolecular materials are constructed by noncovalent bonding,excellent energy transfer groups are introduced into calixarenes,and fullerenes are used as energy receptors,which can significantly improve the charge transport efficiency of the system.At the same time,the application of supramolecular materials in optoelectronic field is expanded.According to the above reasons,the research of this paper will focus on the supramolecular self-assembly system constructed by oxacalixarene derivatives and fullerenes.We mainly carry out the following works:1.Synthesis and purification of precursor molecules were carried out.Homologues of oxacalix[m]arene[n]pyrimidines with different pore sizes were synthesized simultaneously(4OA,6OA,8OA).2.The homologues of naphthalene-substituted oxacalix[m]arene[n]pyrimidines(4OA-N,6OA-N,8OA-N)were prepared by Liebeskind-Srogl reaction and the crystal structures of 8OA and 8OA-N were successfully obtained.Spectroscopic tests and single crystal analysis showed that the fluorescence intensity target molecule 4OA-N,6OA-N,8OA-N was significantly increased((37)_4OA-N=27.50%,(37)_6OA-N=28.93%,(37)_8OA-N=24.31%)relative to the precursor molecule,and all three molecules had similar LE double emission behavior.Target molecule and C₆₀ can form a stable 1:1 host-guest complex with complexation constants 4.10×10⁴ to 6.68×10⁴ M^-1 through fluorescence titration,and taking 4OA-N as an example,it is found that its effective complexation with C₇₀ can also occur.In the frontier molecular orbits theoretical calculations,the HOMO of 4OA-N@C₆₀ distributes on 4OA-N and the LUMO localize on fullerene,which indicates that the charge transfer(CT)occurs between the host and guest molecules,and also proves the interaction between the host and guest molecules.The quantum yield of the other8OA-N molecules and their complexation constants with the C₆₀ are the lowest among the three molecules,due to their distorted spatial configuration and the blocking of S₀-S₁excited state transitions.3.The structure of the BODIPY substituted oxacalixarene supramolecular host molecule 4OA-BDP,characterized by ¹H NMR and HRMS was prepared.Spectroscopic tests and single crystal analysis showed that the fluorescence intensity target molecule4OA-BDP was significantly increased((37)_4OA-BDP=33.60%)relative to the precursor molecule and showed LE behavior.The complexation ratios of 4OA-BDP to C₆₀,C₇₀ and compound 2 were 2:1,4:1,2:1,respectively.The complexation constants K_a from3.01×10⁴ to 1.05×10⁵M^-1,indicating that the interaction between 4OA-BDP and fullerene is not only related to the size and configuration of the main molecule,but also to the size and configuration of the receptor molecule.In the frontier molecular orbits theoretical calculations,the HOMO distributes on 4OA-BDP and the LUMO localize on fullerene,which indicates that the charge transfer(CT)occurs between the host and guest molecules,and also proves the interaction between the host and guest molecules.The theoretical calculation results are in good agreement with the experimental results.