The Research On The Stimuli-Responsive Molecular Recognition Of Several Bridged Compounds

Molecular recognition has been widely found in living matter and nature,which plays fundamentally roles in biological functions.Inspired by nature,the artificial molecular recognition system has developed rapidly in last years and has endowed unique application potential in wide fields of adsorption and separation,drug solubilization,drug delivery,and disease diagnosis and treatment.The driving force of molecular recognition is mainly non-covalent bond interactions,so it has a unique stimulus-responsive behavior.At present,the stimuli-responsive molecular recognition mainly depends on the change of the configuration and/or chemical properties of the host and/or guest molecules.Among them,2,2’-bipyridine and azobenzene can undergo significant configuration transformation under external stimulation.In this paper,a series of bridged host and guest molecules were designed and synthesized,in which 2,2-bipyridine and azobenzene were chosen as the functional bridge groups.Thereafter,their stimulus-responsive molecular recognition behaviors were investigated.The main contents of this paper are as follows.1.The development of supramolecular chemistry is briefly introduced and the principle of molecular recognition is summarized.Thereafter,the stimuli-responsive molecular recognition system including porphyrin,2,2’-bipyridine,azobenzene are reviewed.2.A series of 2,2’-bipyridine bridge porphyrin molecules were designed and synthesized,which were fully characterized by NMR and MS.The bonding behaviors of the above bridged prophyrins with fullerene C₆₀/C₇₀ were investigated by UV-vis fluorescence spectroscopy and NMR spectroscopy.Taking advantage of the configuration changes of 2,2’-bipyridine and the strongπ-πinteractions of porphyrin with fullerene,the selective bonding and release of C₆₀/C₇₀ was achieved by ion-modulated configuration changes of 2,2’-bipyridine,which will provide a preliminary model for fullerene transport.3.Diaminocyclohexane bridged zinc porphyrin and three azobenzene-bridged pyridine molecules of the same configuration were designed and synthesized,which were characterized by NMR and MS.The molecular recognition behaviors of the above two chiral porphyrin with three azobenzene-bridged pyridines were investigated.The bonding behavior of the above chirality porphyrin molecule pincers to three azobenzene-bridged pyridine molecules of the same configuration was investigated by UV,CD and NMR.The experimental results indicated that the bridged porphyrin have stronger bonding properties to the para-substituted pyridine:light modulation of the azobenzene cis-trans conformation leads to the modulation of the bonding properties and the modulation of the circular dichroism signal of the porphyrin.The chirality optical switch for light modulation was successfully constructed by simple molecular recognition,which provides a new avenue for the preparation of dynamic chiroptical switch.4.The azobenzene-bridged para-pyridine salt molecules were designed and synthesized,and their molecular recognition behaviors with cucurbituril were investigated by UV-vis,fluorescence and NMR spectroscopy.Taking advantage of the molecular recognition of cucurbituril with pyridinium,pseudo[3]rotaxane polypseudorotaxane were successfully constructed from CB[7]and CB[8]pyridinium derivatives.Subsequently,the photoisomerization behavior of the above pseudo[3]rotaxane polypseudorotaxanewere investigated,the results indicated that the pseudo[3]rotaxane can undergo photoisomerization efficiently via light irradiation at various wavelengths,while the polypseudorotaxane cannot isomerize due to the site resistance of inclusion complex formed with CB[8].Then,the N=N breakage and fluorescence behavior under spent oxygen conditions were subsequently investigated.This study provides a simple model for the monitoring of depleted oxygen conditions and the labeling of tumors.