4,7‐Dimethyl‐4,7‐dihydro[1,2,5]thiadiazolo‐[3,4‐b]pyrazine, a Novel Electron Donor with a 12π‐Electron Ring System

Abstract

Angew. C'hem. 1111. Ed. Engl. 29 (1990) No. 6 0 VCH Verlag.sgesell.schafi mbH, 0-6940 Weinheim, 1990 0570-0833/90j0606-0643 S 03.50+ .25/0 Angew. Chem. Inl. Ed. Engl. 29 (1990) No. 6 Q VCH Verlugsgesell.~chuji mbH. 0-6940 Weinheim, 1990 0570-0833~9~~0606-ocs4s S 03.50i .2S!O

1-(4-Methylamino-1,2,5-thiadiazole-3-carbonyl)thiosemicarbazide

“…Molecules of (I) in neighbouring sheets are uniformly stacked along the a axis, with centroid±centroid separations of 4.660 (1) A Ê (the a-axis cell length). A similar stacking arrangement of the thiadiazole rings has been found in 4,7dimethyl-4,7-dihydro-1,2,5-thiadiazolo[3,4-b]pyrazine (plane± plane distance = 3.35 A Ê ; Yamashita et al, 1990), in the thiadiazole derivative of tetracyanoquinodimethane (3.48 A Ê ; Suzuki et al, 1992) and in the naphtho derivative of bis-1,2,6-thiadiazine (3.794 A Ê , which is equal in length to the c axis; Gieren et al, 1979).…”

“…Thiosemicarbazides and their derivatives are widely used as ligands for the sensing of metal cations (Busev, 1972). In addition, the close intermolecular NÁ Á ÁS contacts that have been observed in a variety of compounds containing thiadiazole or thiadiazine rings (Daley et al, 1984;Yamashita et al, 1990;Suzuki et al, 1992Suzuki et al, , 1997 are an interesting feature of the NÐSÐN linkage. These contacts may be due to an intermolecular electrostatic interaction between ±NÐS + N± dipoles and/or weak intermolecular bonding involving a partial rehybridization at the S atom, with d-orbital participation (Gieren et al, 1979).…”

Synthesis and characterization of new electron donors containing 1,2,5-thiadiazole and 1,1′-dihydro-4,4′-bi(pyridylidene) units

“…1 Introduction of this electron-withdrawing heterocycle to strong electron-donating skeletons leads to novel highly-polarized electron donors. [2][3][4] In some cases, interesting molecular networks are formed by intermolecular interactions between the heteroatoms of the thiadiazoles. For example, 4,7-dimethyl-4,7-dihydro- [1,2,5]thiadiazolo [3,4-b]pyrazine 1 is a highly-polarized strong electron donor which forms a sheet-like network in the crystal.…”

“…[2][3][4] In some cases, interesting molecular networks are formed by intermolecular interactions between the heteroatoms of the thiadiazoles. For example, 4,7-dimethyl-4,7-dihydro- [1,2,5]thiadiazolo [3,4-b]pyrazine 1 is a highly-polarized strong electron donor which forms a sheet-like network in the crystal. 2 On the other hand, viologens 2 are widely used as electrontransfer reagents since they are easily prepared and show welldefined redox processes.…”

“…For example, 4,7-dimethyl-4,7-dihydro- [1,2,5]thiadiazolo [3,4-b]pyrazine 1 is a highly-polarized strong electron donor which forms a sheet-like network in the crystal. 2 On the other hand, viologens 2 are widely used as electrontransfer reagents since they are easily prepared and show welldefined redox processes. 5 Although viologens are stable in air, their cation radical and neutral states are unstable toward oxygen due to their very low oxidation potentials.…”