[1,2,5]Selenadiazolo[3,4‐c][1,2,5]thiadiazole and [1,2,5]Selenadiazolo[3,4‐c][1,2,5]thiadiazolidyl – A Synthetic, Structural, and Theoretical Study

Abstract

Dedicated to Professor Neil Bartlett on the occasion of his 75th birthday IntroductionChalcogen-nitrogen chemistry [1] has begun to play an increasingly important role in the design and synthesis of [a]

Donor–Acceptor Complexes between 1,2,5‐Chalcogenadiazoles (Te, Se, S) and the Pseudohalides CN−and XCN−(X=O, S, Se, Te)

“…The reason might be that the counter cation was not included in the thermodynamics calculations. Like in previously described D–A complexes– and in [ 1 a ‐CN] − , in the anions of 3 – 6 the D–A Te−X bonds (X=N, S, Se) are by 0.28–0.66 Å longer than the sum of the covalent radii and by 0.82–1.36 Å shorter than the sum of the van der Waals radii of the Te and X atoms. The DFT‐optimized gas‐phase geometries of the anions of 3 – 6 are in reasonable agreement with the corresponding XRD data although, as with [ 1 a ‐CN] − , the calculations underestimate (up to 0.2 Å) the D–A Te−X bond lengths (Table ; for some putative complexes, see the Supporting Information).…”

Redox properties and radical anions of fluorinated 2,1,3‐benzothia(selena)diazoles and related compounds

“…In most of the cases, the experiments were performed in MeCN which is more suitable for the chemical reduction of neutral precursors and isolation of the RAs in the form of salts planned for further research ( cf . previous work) 25–31. According to the half‐life times (Table 2, τ 1/2 ), the RAs of fluorinated derivatives, especially 4 and 9 , are long‐lived under the CV conditions in MeCN at 295 K. In the studied cases of RAs of 5 and 8 , τ 1/2 values in DMF were even bigger than in MeCN.…”

“…Coordination numbers of transition metal cations allow coordinating more than one RA to the same metal center which favors higher Curie temperatures 68. Furthermore, one can expect coordination of these soft cations to the soft S (Se) centers of the RAs whereas previously studied hard Na + and K + cations were coordinated to the hard N centers of the RAs 25–31…”

“…The DFT approach at the (U)B3LYP/6‐31+G(d)39, 40 level of theory was used for the calculations since it performs well for molecular structures and properties of main‐group compounds including electron affinities and hyperfine coupling constants 20, 41, 42. Previously, the (U)B3LYP method was successfully employed to reproduce the properties of a series of both closed‐ and open‐shell chalcogen–nitrogen cycles and cages including RAs 25–31, 43–50. Quantum chemical calculations on RAs and their neutral precursors were carried out with full geometry optimization using the GAMESS51 and GAUSSIAN‐0352 programs.…”

“…Being interested in stable π ‐heterocyclic RAs as the promising building blocks for magnetically active molecular materials,25–31 we performed the verification of the aforementioned hypothesis. In this study we report on the redox properties and radical anions of fluorinated heteroaromatics 3 and 4 and related derivatives 5 – 11 (Chart ).…”