Hysteretic Room-Temperature Magnetic Bistability of the Crystalline 4,7-Difluoro-1,3,2-Benzodithiazolyl Radical.

The title radical R⋅, synthesized by reduction of the corresponding cation R, is thermally stable up to ~380 K in the crystalline state under anaerobic conditions. With SQUID magnetometry, single-crystal and powder XRD, solid-state EPR and TG-DSC, reversible spin-Peierls transition between diamagnetic and paramagnetic states featuring ~10 K hysteretic loop is observed for R⋅ in the temperature range ~310-325 K; ΔH=~2.03 kJ mol and ΔS=~6.

1,2,3,4-Tetrafluorobiphenylene: A Prototype Janus-Headed Scaffold for Ambipolar Materials.

The title compound was synthesized by Ullmann cross-coupling in low yield as the first representative of [n]phenylene containing hydrocarbon and fluorocarbon rings. Stille/Suzuki-Miyaura cross-coupling reactions, as well as substitution of fluorine in suitable starting compounds, failed to give the same product. The geometric and electronic structures of the title compound were studied by X-ray diffraction, cyclic voltammetry and density functional theory calculations, together with Hirshfeld surface and reduced density gradient analyses.

Halide Complexes of 5,6-Dicyano-2,1,3-Benzoselenadiazole with 1 : 4 Stoichiometry: Cooperativity between Chalcogen and Hydrogen Bonding.

The [M -Hal] (M=the title compound; Hal=Cl, Br, and I) complexes were isolated in the form of salts of [Et N] cation and characterized by XRD, NMR, UV-Vis, DFT, QTAIM, EDD, and EDA. Their stoichiometry is caused by a cooperative interplay of σ-hole-driven chalcogen (ChB) and hydrogen (HB) bondings. In the crystal, [M -Hal] are connected by the π-hole-driven ChB; overall, each [Hal] is six-coordinated.

Tuning Molecular Electron Affinities against Atomic Electronegativities by Spatial Expansion of a π-System.

2,1,3-Benzochalcogenadiazoles C R N E (E/R; E=S, Se, Te; R=H, F, Cl, Br, I) and C H R N E (E/R'; E=S, Se, Te; R=Br, I) are 10π-electron hetarenes. By CV/EPR measurements, DFT calculations, and QTAIM and ELI-D analyses, it is shown that their molecular electron affinities (EAs) increase with decreasing Allen electronegativities and electron affinities of the E and non-hydrogen R (except Cl) atoms. DFT calculations for E/R+e⋅ →[E/R]⋅ electron capture reveal negative ΔG values numerically increasing with increasing atomic numbers of the E and R atoms; positive ΔS has a minor influence.

Acid-Base and Anion Binding Properties of Tetrafluorinated 1,3-Benzodiazole, 1,2,3-Benzotriazole and 2,1,3-Benzoselenadiazole.

The influence of fluorination on the acid-base properties and the capacity of structurally related 6-5 bicyclic compounds - 1,3-benzodiazole 1, 1,2,3-benzotriazole 2 and 2,1,3-benzoselenadiazole 3 to σ-hole interactions, i. e. hydrogen (1 and 2) and chalcogen (3) bondings, is studied experimentally and computationally.

Bis(2,1,3-benzotelluradiazolidyl)2,1,3-benzotelluradiazole: a pair of radical anions coupled by TeN chalcogen bonding.

Reduction of 2,1,3-benzotelluradiazole (3) yielded a crystalline solid that features a trimeric dianion formally composed of two [3]˙- and one 3 bridged by unusually asymmetric TeN chalcogen bonds. The solid is diamagnetic due to strong antiferromagnetic coupling, as revealed by CASSCF/CASPT2 and BS-DFT.

Chemistry of Herz radicals: a new way to near-IR dyes with multiple long-lived and differently-coloured redox states.

A new synthetic methodology based on the self-condensation of 1,2,3-benzodithiazolyl diradicals (Herz radicals) produces unprecedented 5-6-6-6-5 and 5-6-7-6-5 pentacyclic sulfur-nitrogen near-IR dyes featuring up to five multiple long-lived and differently coloured redox-states.

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

By means of cyclic voltammetry (CV) and DFT calculations, it was found that the electron-acceptor ability of 2,1,3-benzochalcogenadiazoles 1-3 (chalcogen: S, Se, and Te, respectively) increases with increasing atomic number of the 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 spectroscopy under CV conditions.

3D molecular network and magnetic ordering, formed by multi-dentate magnetic couplers, bis(benzene)chromium(i) and [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazolidyl.

The reaction between bis(benzene)chromium(0), Cr0(C6H6)2, and [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (abbreviated as TDTD) formed single crystals of the 1 : 1 salt, [CrI(C6H6)2]+[TDTD]-. The crystal structure of [Cr(C6H6)2][TDTD] belongs to the monoclinic P21/c space group, and involves a CdSO4-type network (or quartz dual net), which is formed by CHN hydrogen bonds between [Cr(C6H6)2]+ (S = 1/2) and [TDTD]- (S = 1/2). In addition to this network, the two components form an alternating chain crystal with a π-π overlap along the [110] and [11[combining macron]0] directions.

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

Donor-acceptor (D-A) complexes between 3,4-dicyano-1,2,5-chalcogenadiazoles [chalcogen=Te (1 a), Se (1 b), S (1 c)] and the pseudohalides CN and XCN (X=O, S, Se, Te) were studied experimentally and theoretically. For 1 a, they were isolated as [K(18-crown-6)][1 a-CN] (2), [K(18-crown-6)][1 a-NCO] (3), [K(18-crown-6)][1 a-SCN] (4), [K(18-crown-6)][1 a-SeCN] (5), and [K][1 a-NCSe] (6) and characterized by X-ray diffraction (XRD), UV/Vis and NMR spectroscopy, and DFT and QTAIM calculations. For 1 b and 1 c, the complexes were not isolated due to unfavorable thermodynamics.

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

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.

Nature of Bonding in Donor-Acceptor Interactions Exemplified by Complexes of N-Heterocyclic Carbenes with 1,2,5-Telluradiazoles.

Comprehensive structural, spectroscopic, and quantum chemical analyses of new donor-acceptor complexes between N-heterocyclic carbenes and 1,2,5-telluradiazoles and a comparison with previously known complexes involving tellurenyl cations showed that the dative C-Te bonds cannot be solitarily described with only one Lewis formula. Canonical Lewis formulas that denote covalency and arrows emphasizing ionicity complement each other in varying extents. Evaluation of the relative weights of these resonance forms requires proper bonding description with a well-balanced toolbox of analytical methods.

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

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.

The First Lanthanide Complexes with a Redox-Active Sulfur Diimide Ligand: Synthesis and Characterization of [LnCp* (RN=) S], Ln=Sm, Eu, Yb; R=SiMe.

The first lanthanide complexes with a redox-active sulfur diimide ligand, [LnCp* (Me SiN=) S] (Ln=Sm, Eu, Yb; Cp*=η -C Me ), are reported. The complexes were synthesized by using [LnCp* (THF) ] and (Me SiN=) S and have been thoroughly characterized by single-crystal X-ray diffraction, EPR spectroscopy, UV/Vis/NIR electronic absorption spectroscopy and SQUID magnetometry. The results, as interpreted by CASSCF/SOC-RASSI calculations providing a non-perturbative treatment of spin-orbit coupling, indicate that these paramagnetic complexes are best described as Ln and [(Me SiN=) S] adducts.

Fused 1,2,3-Dithiazoles: Convenient Synthesis, Structural Characterization, and Electrochemical Properties.

A new general protocol for synthesis of fused 1,2,3-dithiazoles by the reaction of cyclic oximes with S₂Cl₂ and pyridine in acetonitrile has been developed. The target 1,2,3-dithiazoles fused with various carbocycles, such as indene, naphthalenone, cyclohexadienone, cyclopentadiene, and benzoannulene, were selectively obtained in low to high yields. In most cases, the hetero ring-closure was accompanied by chlorination of the carbocyclic moieties.

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.

Low-temperature interaction of [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (1) with MoMes2 (Mes = mesitylene/1,3,5-trimethylbenzene) in tetrahydrofuran gave the heterospin (S1 = S2 = (1)/2) radical-ion salt [MoMes2](+)[1](-) (2) whose structure was confirmed by single-crystal X-ray diffraction (XRD). The structure revealed alternating layers of the cations and anions with the Mes ligands perpendicular, and the anions tilted by 45°, to the layer plane. At 300 K the effective magnetic moment of 2 is equal to 2.

New NIR-emissive tetranuclear Er(III) complexes with 4-hydroxo-2,1,3-benzothiadiazolate and dibenzoylmethanide ligands: synthesis and characterization.

New tetranuclear heteroleptic complexes [Er4(dbm)6(O-btd)4(OH)2] (1) and [Er4(dbm)4(O-btd)6(OH)2] (2) (O-btd = 4-hydroxo-2,1,3-benzothiadiazolate and dbm = dibenzoylmethanide) and their solvates with toluene, THF and CH2Cl2 were prepared using two synthetic approaches. The structures of the products were confirmed by single-crystal X-ray diffraction. Magnetic properties of 1 and 2 are in good agreement with X-ray data.

Breathing some new life into an old topic: chalcogen-nitrogen π-heterocycles as electron acceptors.

Recent progress in the design, synthesis and characterization of chalcogen-nitrogen 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.

Bis(toluene)chromium(I) [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazolidyl and [1,2,5]thiadiazolo[3,4-b]pyrazinidyl: new heterospin (S1 = S2 = ½) radical-ion salts.

Bis(toluene)chromium(0), Cr(0)(η(6)-C7H8)2 (3), readily reduced [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (1) and [1,2,5]thiadiazolo[3,4-b]pyrazine (2) in a tetrahydrofuran solvent with the formation of heterospin, S1 = S2 = ½, radical-ion salts [3](+)[1](-) (4) and [3](+)[2](-) (5) isolated in high yields. The salts 4 and 5 were characterized by single-crystal X-ray diffraction (XRD), solution and solid-state electron paramagnetic resonance, and magnetic susceptibility measurements in the temperature range 2-300 K. Despite the formal similarity of the salts, their crystal structures were very different and, in contrast to 4, in 5 anions were disordered.

Experimental and computational study on the structure and properties of Herz cations and radicals: 1,2,3-benzodithiazolium, 1,2,3-benzodithiazolyl, and their Se congeners.

Salts of 1,2,3-benzodithiazolium (1), 2,1,3-benzothiaselenazolium (3), and 1,2,3-benzodiselenazolium (4) (Herz cations), namely, [1][BF4], [1][SbCl6], [3][BF4], [3][GaCl4], [3][SbCl6], and [4][GaCl4], were prepared from the corresponding chlorides and NaBF4, GaCl3, or SbCl5. It was found that [1][SbCl6] and [3][SbCl6] spontaneously transform in MeCN solution to [1]3[SbCl6]2[Cl] and [3]3[SbCl6]2[Cl], respectively. [1][BF4], [1]3[SbCl6]2[Cl], [3][BF4], [3]3[SbCl6]2[Cl], and [4][GaCl4] were structurally characterized by X-ray diffraction (XRD).

Interaction of 1,2,5-chalcogenadiazole derivatives with thiophenolate: hypercoordination with formation of interchalcogen bond versus reduction to radical anion.

According to the DFT calculations, [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (4), [1,2,5]selenadiazolo[3,4-c][1,2,5]thiadiazole (5), 3,4-dicyano-1,2,5-thiadiazole (6), and 3,4-dicyano-1,2,5-selenadiazole (7) have nearly the same positive electron affinity (EA). Under the CV conditions they readily produce long-lived π-delocalized radical anions (π-RAs) characterized by EPR. Whereas 4 and 5 were chemically reduced into the π-RAs with thiophenolate (PhS(-)), 6 did not react and 7 formed a product of hypercoordination at the Se center (9) isolated in the form of the thermally stable salt [K(18-crown-6)][9] (10).

Interaction of 1,3,2,4-benzodithiadiazines and their 1-Se congeners with Ph3P and some properties of the iminophosphorane products.

Interaction between Ph(3)P and 1,3,2,4-benzodithiadiazine (1); its 6,7-difluoro (2), 5,6,8-trifluoro (3) and 5,6,7,8-tetrafluoro (4) derivatives; and 5,6,8-trifluoro-3,1,2,4-benzothiaselenadiazine (5) proceeded via a 1:1 condensation to give Ph(3)P═N-R iminophosphoranes (1a-5a, R = corresponding 1,2,3-benzodichalcogenazol-2-yls), which are inaccessible by general approaches based on the Staudinger and Kirsanov reactions. In contrast, neither Ph(3)As nor Ph(3)Sb reacted with 1 and 4. Molecular structures of 1a-5a and 5 were confirmed by X-ray diffraction (XRD).

Heterospin pi-heterocyclic radical-anion salt: synthesis, structure, and magnetic properties of decamethylchromocenium [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazolidyl.

Decamethylchromocene, Cr(II)(eta(5)-C(5)(CH(3))(5))(2) (2), readily reduced [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazole (1) in a tetrahydrofuran solvent at ambient temperature with the formation of radical-anion salt [2](+)[1](-) (3) isolated in 97% yield. The heterospin salt 3 ([2](+), S = 3/2; [1](-), S = 1/2) was characterized by single-crystal X-ray diffraction as well as magnetic susceptibility measurements in the temperature range 2-300 K. The experimental data together with theoretical analysis of the salt's magnetic structure within the CASSCF and spin-unrestricted broken-symmetry (BS) density functional theory (DFT) approaches revealed antiferromagnetic (AF) interactions in the crystalline 3: significant between anions [1](-), weak between cations [2](+), and very weak between [1](-) and [2](+).

Photochemical study on the reactivity of tetrasulfur tetranitride, S4N4.

To elucidate the multifaceted but poorly understood chemistry of the pivotal polysulfur-nitrogen heterocycle, tetrasulfur tetranitride (S(4)N(4), 1), its photochemistry was studied in Ar matrices. Thereby two primary intermediates and a secondary one (2-4) were detected, and their UV-vis and IR spectra were identified through specific interconversions of 1-4 that can be induced by selective irradiations. The structures associated with these spectra were assigned with the help of DFT calculations.

Matrix isolation and computational study of the photochemistry of 1,3,2,4-benzodithiadiazine.

Photolysis of 1,3,2,4-benzodithiadiazine (1) at ambient temperature yields stable 1,2,3-benzodithiazolyl radicals. In order to reveal the mechanism of this unusual transformation, the photochemistry of 1 was studied in argon matrices using IR and UV-vis spectroscopy. A series of intermediates, including four- and five-membered heterocyclic and o-quinoid acyclic species, were characterized spectroscopically with the help of quantum chemical calculations.