Synthesis Of Novel Azobenzene Derivatives And The Study Of Anion Recognition Properties

Molecular recognition is the process that host molecular binds with guest molecularselectively and result in some special functions, which is an important field of researching insupramolecular chemistry. Supramolecular chemistry due to the closely related to the lifesciences has become a new inter-subject, is a discipline of structure and function ofsupramolecular systems. It included the recognition for neutral molecules, biologicalmacromolecules, anion and cation. The anion recognition chemistry, as an important part ofmolecular recognition, has been given considerable attention from lots of specialists bothhome and abroad. Anions play an important role in a wide range of chemical, biological,environmental and medical applications. The key is to synthesize artificial hosts with highselectivity for particular anions so as to sense special anions selectively in competive mediasuch as water. A series of novel selective colorimetric hosts containing Schiff Base,Azobenzene derivatives had been designed and synthesized and studied the essence of anionrecognition. The content of the thesis mainly includes three parts:Chapter one: reviewed literature of various kinds of anion recognition, briefly introducedall kinds of sensors research status and progress of study on anion recognition.Chapter two: The studies of anion host1and2bearing Schiff base, azophenol and2-phenoxyacetohydrazide. The novel selective cyanide anion host2based on azophenol and2-phenoxyacetohydrazide had been designed and synthesized. Host2behaves a singleselectivity and sensitivity in the recognition for CN anion over other anions such as F^-, Cl^-,Br^-, I^-, H₂PO₄^-, AcO^-, HSO₄and ClO₄by naked-eyes and UV-vis spectra changes inaqueous solutions （H₂O/DMSO,5:5, v/v）. The color of the solution containing host2had anobvious change from colorless to yellow only after the addition of CN in aqueous solutionswhile other anions did not cause obvious color change. The¹H NMR titration experimentsand MS data indicated the formation of1∶1addition compound between the sensor and CN,which due to the nucleophilic addition reaction of cyanide. The association constant Kawas2.5×10⁴. The detection limitation of CN with the host2was5.0×10^-6M.Chapter three: The development of anion recognition properties hydrazinecar-bothioamide hosts3in DMSO. The development of anion recognition properties ofN⁴-nitrophenylthiosemicarbazone of salicylaldehyde host3was studied in DMSO solution,behaves with a good selectivity and sensitivity in the recognition for F^-anions by naked eyeobservations and UV–Vis spectral changes. The color of the solution containing the sensorhad an obvious change from colorless to purple only after the addition of F^-in DMSO whileother anions did not cause obvious color changes.¹H NMR titration results revealed that the binding process includes two steps:（i） hydrogen bonding interactions;（ii） proton transferbetween the host3and the coordinated anion.