Breathing Some New Life into an Old Topic: Chalcogen-Nitrogen π-Heterocycles as Electron Acceptors

Abstract

Recent progress in the design, synthesis and characterization of chalcogennitrogen π-heterocycles, mostly 1,2,5-chalcogenadiazoles (chalcogen: S, Se and Te) and their fused derivatives, possessing positive electron affinity is discussed together with their use in preparation of charge-transfer complexes and radical-anion salts-candidate building blocks of molecule-based electrical and magnetic functional materials.

Design and theoretical study of D–A–pi–A' organic sensitizers with [1,2,5]oxa-, thia- or selenadiazoloazine fragment

“…In our study we use both traditional building blocks reviewed previously by us and by other authors and extended list of donor groups that includes some new previously unexplored fragments. Based on our recent investigations and the works of other researchers 7,[14][15][16][17][18][19][20][21][22][23][24] six variants of A-fragments (A-block) which have showed good characteristics were selected for the present study: [1,2,5]thiadiazolo [3,4-c] [3,4-c]pyridazine. The general formula for these derivatives is represented in Scheme 1.…”

[1,2,5]Selenadiazolo[3,4‐b]pyrazines: Synthesis from 3,4‐Diamino‐1,2,5‐selena­diazole and Generation of Persistent Radical Anions

“…According to the gas-phase (U)B3LYP/6-31+G(d) calculations, the first adiabatic electron affinity (EA) of compounds 5g and 5c are 1.55 and 1.93 eV, respectively, as compared with 0.22 eV for 1,2,5-selenadiazole and 1.06 eV for 2,1,3-benzoselenadiazole (10). [7] In the potential range 0 --2 V, the cyclic voltammogram (CV) of 5g contains three reduction peaks Ep Ep 1C = −1.40 V. [30] For both 5g and 5c the first reduction peak is H decoupling during acquisition. Spectra were acquired with recycle intervals of between 5 and 55 s, depending on the longitudinal relaxation time of the samples.…”

“…[1][2][3][4][5][6][7][8][9] Amongst 1,2,5-chalcogenadiazoles the best studied are the sulfur derivatives [1][2][3][4]7,10,11] though there are scattered reports on the selenium analogues, [2,4,7,[12][13][14] whereas chemistry of 1,2,5-telluradiazoles is only emerging. [4][5][6][7]15,16] Very recent interest to these compounds, especially fused with benzene and heterocyclic rings, is due to their actual or potential applications as building blocks in organic functional materials such as light emitters, solar cells, synthetic metals, as well as drugs for preventive and therapeutic medical treatment and fluorescent imagine probes. [1,4,7,13,14,17] Recently, it was shown that many classes of chalcogennitrogen π-heterocycles possess positive electron affinity (EA) making them suitable precursors for thermodynamically stable radical anions (RAs) which are possible building blocks for magnetically-active functional materials.…”

“…[4][5][6][7]15,16] Very recent interest to these compounds, especially fused with benzene and heterocyclic rings, is due to their actual or potential applications as building blocks in organic functional materials such as light emitters, solar cells, synthetic metals, as well as drugs for preventive and therapeutic medical treatment and fluorescent imagine probes. [1,4,7,13,14,17] Recently, it was shown that many classes of chalcogennitrogen π-heterocycles possess positive electron affinity (EA) making them suitable precursors for thermodynamically stable radical anions (RAs) which are possible building blocks for magnetically-active functional materials. [7][8][9] Whereas some 1,2,5-thiadiazolidyl RAs, including [1,2,5]thiadiazolo [3,4-b]pyrazinidyl, have already been isolated in the form of thermally stable salts, [7][8][9]18] investigation of their Se congeners is restricted by synthetic accessibility.…”

“…[1,4,7,13,14,17] Recently, it was shown that many classes of chalcogennitrogen π-heterocycles possess positive electron affinity (EA) making them suitable precursors for thermodynamically stable radical anions (RAs) which are possible building blocks for magnetically-active functional materials. [7][8][9] Whereas some 1,2,5-thiadiazolidyl RAs, including [1,2,5]thiadiazolo [3,4-b]pyrazinidyl, have already been isolated in the form of thermally stable salts, [7][8][9]18] investigation of their Se congeners is restricted by synthetic accessibility. There is a lack of suitable preparative approaches to many interesting and potentially useful derivatives with enlarged EA including, for example, [1,2,5]selenadiazolo [3,4-b]pyrazines.…”