Synthesis and Properties of the Heterospin (S1=S2=1/2) Radical-Ion Salt Bis(mesitylene)molybdenum(I) [1,2,5]Thiadiazolo[3,4-c][1,2,5]thiadiazolidyl

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With cyclic voltammetry (CV) and DFT calculations, it was found that electron acceptor ability of the 2,1,3-benzochalcogenadiazoles 1-3 (chalcogen: S, Se and Te, respectively) increases with the atomic number of chalcogen. This trend is nontrivial since it contradicts the electronegativity and atomic electron affinity of the chalcogens. In contrast to radical anions (RAs) [1]*- and [2]*-, RA [3]*- was not detected by EPR under the CV conditions. Chemical reduction of 1-3 was performed and new thermally-stable RA salts [K(THF)]+[2]*- (8) and [K(18-crown-6)]+[2]*- (9) were isolated in addition to known salt [K(THF)]+[1]*- (7). Upon contact with air, RAs [1]*- and [2]*- underwent fast decomposition in solution with the formation of anions [ECN]- isolated in the form of salts [K(18-crown-6)]+[ECN]- (10, E = S; 11, E = Se). In the case of 3, RA [3]*- was detected by EPR to be the first representative of tellurium-nitrogen π-heterocyclic RAs but not isolated. Instead, salt [K(18-crown-6)]+2[3-Te2]2- (12) featuring a new anionic complex with the coordinate bond Te-Te was obtained. Upon contact with air, salt 12 transformed into salt [K(18-crown-6)]+2[3-Te4-3]2- (13) revealing an anionic complex with two coordinate bonds Te-Te. The structures of 8-13 were confirmed by X-ray diffraction and the nature of the coordinate bonds Te-Te in [3-Te2]2- and [3-Te4-3]2- was studied with DFT calculations and QTAIM analysis.

Section: Discussionmentioning

confidence: 99%

Radical Anions, Radical‐Anion Salts, and Anionic Complexes of 2,1,3‐Benzochalcogenadiazoles

Pushkarevsky

Chulanova

Shundrin

et al. 2018

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“…According to the DFT calculations,t he addition is am ultistep process, featuring diradical intermediates and hydrogen atom intramolecular migration between Da nd Am oieties over four positions. All of these findings create new possibilities in the field beyondt he recently described CT processes covering reduction of 1,2,5-chalcogenadiazoles into radicala nions isolated in the form of thermally stable salts [12,19,31] and D-A hypercoordinationo fa nions to heavierc halcogen centers of these heterocycles. [11a,b,d,e, 40] Moreover,o ur discovery of hydrogen atom transfer from formal D to formal Af or 1,2,5-chalcogenadiazoles, which leads to D-A cross-coupled products,i sw orth further investigation.…”

Section: Discussionmentioning

confidence: 99%

New Charge‐Transfer Complexes with 1,2,5‐Thiadiazoles as Both Electron Acceptors and Donors Featuring an Unprecedented Addition Reaction

Chulanova

Pritchina

Malaspina

et al. 2016

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The design and synthesis of novel charge-transfer (CT) complexes are of interest for fundamental chemistry and applications to materials science. In addition to the recently described first CT complex with both electron acceptor (A) and donor (D) groups belonging to the 1,2,5-thiadiazole series (1; A: 4-nitro-2,1,3-benzothiadiazole; D: 4-amino-2,1,3-benzothiadiazole), herein novel CT complexes 2 and 3 with 1,2,5-thiadiazoles as both A (4,6-dinitro-2,1,3-benzothiadiazole and [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole) and D (4-amino-2,1,3-benzothiadiazole) were synthesized. The series is completed by complex 4 with [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole as A and phenoxatellurine as D. Structures of complexes 2-4 were characterized by single-crystal X-ray diffraction (XRD), as well as solution and solid-state UV/Vis spectroscopy. Thermodynamics of their formation were obtained by density functional theory (DFT) calculations, their bonding situations were analyzed by quantum theory of atoms in molecules (QTAIM) calculations and dimer model energies of interactions quantified in the framework of the Hirshfeld surface (HS) analysis. With DFT calculations, the largest value of CT between D and A was found for complex 2, with 0.027 e in the XRD structure and 0.150 e in the optimized structure in MeCN. In the UV/Vis spectra, the λ of the CT bands of 2-4 varied in the range λ=517-705 nm. Model energy calculations for 1-4 revealed the importance of both dispersion interactions and hydrogen bonding between D and A as contributors to CT in the crystalline state. In an attempt to enlarge the CT value with bis[1,2,5-thiadiazolo][3,4-b;3',4'-e]pyrazine as A and 4-amino-2,1,3-benzoselenadiazole as D, an unprecedented 1:1 addition reaction was observed upon formation of a C-N bond between atom C7 of D and pyrazine atom N4 of A, accompanied by hydrogen atom transfer from C7 to another pyrazine atom N8 (compound 5). According to DFT calculations, the reaction is a multistep process featuring diradical intermediates and hydrogen atom intramolecular migration over four positions. Molecular and crystal structures of 5 (solvate with toluene) were elucidated by XRD and the crystal structure revealed a rather unusual porous framework.

“…For 2,1,3-benzochalcogenadiazoles, EA 1 can be furthere nlarged by fluorination of their carbocycles and, in contrastt op olyfluorinated arenes, the (RAs) of theseh eteroarenes are long-lived and can be detected by conventional EPR spectroscopy. [27][28][29] The electron-acceptor properties of 1,2,5chalcogenadiazolesc an be used in the design and synthesis of magnetically-active RA salts, [30] charge-transfer complexes, [31,32] and hypercoordinate complexesw ith Lewis bases. [33] In the case of polyfluorinated 2,1,3-benzodiazoles they can also be used for analytical determination of Se at ultratrace levels by gas chromatography with electron-capture detection.…”

Section: Dft Structures and Electron Affinities Of The Rasmentioning

confidence: 99%

Fused 1,2,3‐Thiaselenazoles Synthesized from 1,2,3‐Dithiazoles through Selective Chalcogen Exchange

Konstantinova

Baranovsky

Pritchina

et al. 2017

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A new approach to the synthesis of fused 1,2,3-thiaselenazoles-rare five-membered heterocycles that contain two different chalcogens-from the corresponding 1,2,3-dithiazoles and SeO was accomplished by selective exchange of S and Se atoms. The fused carbo- and heterocyclic units were indene, naphthalenone, cyclohexadienone, cyclopentadiene, benzoannulene, and benzoxazine. The molecular structures of two of the thiaselenadiazole products and one of the dithiazole precursors were confirmed by single-crystal X-ray diffraction. The reaction is highly solvent selective; it only takes place in solvents that contain a C=O group (e.g., DMF or tetramethylurea). According to DFT calculations, the reaction is thermodynamically favorable. Based on the DFT calculations and Se NMR spectroscopy, two tentative mechanisms that feature isomeric transition states and intermediates are suggested for the reaction via ring-opening addition of SeO to the S-X dithiazole bond (X=N or S). The DFT-calculated first adiabatic electron affinities of the compounds were chalcogen independent and positive in all cases, which assumes formation of thermodynamically stable radical anions (RAs). These calculated RAs featured either normal or abnormal elongation of the S1-X2 (X=S or Se) bond relative to their neutral precursors and possessed π* or σ* SOMOs, respectively.