Synthesis, Electrochemical And Fluorescence Studies Of 1,2,4,5-tetrazine Derivatives: Towards Molecular Sensors For Anions And Electron-rich Compounds And Synthesis And Electrochemical Study Of Ferrocene-containing Pyridinium Salts.

This thesis consists of two parts. The first one deals with the synthesis and electrochemical and fluorescence studies of new 1,2,4,5-tetrazine derivatives as molecular sensors for anions and electron-rich compounds, and the second one with the synthesis and preliminary electrochemical studies of ferrocene-containing pyridinium salts.In part I, a short overview of 1,2,4,5-tetrazine chemistry (s-tetrazine) is presented. s-Tetrazines have already found applications in many fields, but their ability to bind anions or electron-rich compounds through anion-π interaction or π-π stacking has not been noticed until very recently. In this context, a series of novel molecular sensors containing tetrazine moieties as both binding units and sensing units are designed, including tweezer-tetrazines, tripod-tetrazines, cyclophane-tetrazines, and calycular tetrazines. Among them, a tripod-tetrazine (86), two cyclophane-tetrazines (90, 93) and two calycular tetrazines (94, 95) have been successfully synthesized based on S_nAr reactions of 3,6-dichlorotetrazine (23). Fluorescence studies show that the fluorescence of 86, 90, 94 and 95 can be efficiently quenched by electron-rich compounds such as triphenylamine (TPA), tris(4-bromophenyl)amine, pyrrole, tetrathiafulvalene (TTF) and 1,3,5-trimethoxybenzene. Electrochemical studies also indicate the interactions between the tetrazine sensors and these electron-rich compounds. The fluorescence quenching mechanisms are investigated in some cases, and calculations on molecular obitals are carried out to investigate the relationship between molecular structures and fluorescence properties.In part II, the synthesis of a dibranched ferrocene-containing pyridinium salt (45j) and two tri-branched ones (46h, 46j) through the condensations of 1,2,6-trimethyl pyridinium or 1,2,4,6-tetramethyl pyridinium with aromatic aldehydes will be presented. A new synthetic route is also developed for the two important intermediates, trans-5-(2-ferrocenyl-vinyl)-2-carbaldehyde-thiophene (47), and ferrocenylethenyl-bithiopheneyl aldehyde (48). Preliminary electrochemical studies show that bithiophene units influence greatly the redox behaviors of the molecules.