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New fluorinated dibenzo-1,2,5,6-tetrathiocines 1 and 2 were synthesized by a novel condensation of 1,2-disulfenyl chlorides under the influence of elemental Cu, and structurally defined in the solid state, solution, and gas phase by single-crystal XRD, variable-temperature 19F NMR and NOESY, and DFT calculations. Crystalline 1 and 2 exhibited the C2h chair and C2 twist molecular conformations, respectively. Unlike 1 displayed only C⋯S shortened intermolecular contacts, crystal structure of 2 featured F⋯π, F⋯F, F⋯S and S⋯S contacts. In toluene solutions at 296 K, both twist and chair conformers were observed in the ∼1 : 1 and ∼7 : 1 ratios for 1 and 2, respectively. For 1, the twist ↔ chair conformer interconversion was practically temperature-independent, and for 2 revealed ΔH ∼3.5 kJ mol−1 and ΔS ∼4.4 J K−1 mol−1. With DFT, the PESs for twist–chair transformation and twist–twist racemization were analyzed and the TSs exhibiting twist–halfchair and boat conformations, respectively, were found. Several additional stationary points on the PESs, corresponding to hidden intermediates and bifurcation points and featuring twistboat and halfchair conformations were detected. In chloroform solution under sunlight, 1 underwent 1,2,5,6-tetrathiocine → 1,2,3,6-tetrathiocine isomerization whose product was characterized by XRD. [ABSTRACT FROM AUTHOR]

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−1 and ΔS=~6.23 J mol−1 K−1. The transition is accompanied by mechanical movement of the crystals, i. e. by thermosalient behavior. The low‐temperature diamagnetic P‐1 polymorph of R⋅ consists of R⋅2 π‐dimers arranged in (...R⋅2...)n π‐stacks; whereas the high‐temperature paramagnetic P21/c polymorph, of uniform (...R⋅...)n π‐stacks. With the XRD geometries, CASSCF and broken‐symmetry DFT jointly suggest strong antiferromagnetic (AF) interactions within R⋅2 and weak between R⋅2 for the (...R⋅2...)n stacks; and moderate AF interactions between R⋅ for the (...R⋅...)n stacks. The fully hydrocarbon archetype of R⋅ does not reveal the aforementioned properties. Thus, the fluorinated 1,3,2‐benzodithiazolyls pave a new pathway in the design and synthesis of metal‐less magnetically‐bistable materials. [ABSTRACT FROM AUTHOR]

By X-ray diffraction analysis and IR spectroscopy, it was established here that vinyl carbocations C3H5+/C4H7+ with carborane counterion CHB11Cl11− form stable monosolvates C3H5+⋅C3H6/C4H7+⋅C4H8 with molecules of alkenes C3H6/C4H8. They contain molecular group =C+⋯Hδ−–Cδ+= with a new type of bond formed by the H atom of the H–C= group of the alkene with the C atom of the C+=C group of the carbocation. The short C+----Cδ+ distance, equal to 2.44 Å, is typical of that of X----X in proton disolvates (L2H+) with an quasi-symmetrical X–H+⋯X moiety (where X = O or N) of basic molecule L. The nature of the discovered bond differs from that of the classic H–bond by an distribution of electron density: the electron–excessive Hδ− atom from the (=)C–H group of the alkene is attached to the C+ atom of the carbocation, on which the positive charge is predominantly concentrated. Therefore, it can be called an inverse hydrogen bond. [ABSTRACT FROM AUTHOR]

Introduction of Cl and O atoms into C4-vinyl carbocations was studied by X-ray diffraction analysis and IR spectroscopy. Chlorine atoms are weak electron acceptors in ordinary molecules but, within vinyl carbocations, manifest themselves as strong electron donors that accept a positive charge. The attachment of a Cl atom directly to a C=C bond leads to an increase in the e-density on it, exceeding that of the common double bond. The positive charge should be concentrated on the Cl atom, and weak δ− may appear on the C=C bond. More distant attachment of the Cl atom, e.g., to a C atom adjacent to the C=C bond, has a weaker effect on it. If two Cl atoms are attached to the Cγ atom of the vinyl cation, as in Cl2CγCδHCαHCH3, then the cation switches to the allyl type with two practically equivalent and almost uncharged CγCδCα bonds. When such a strong nucleophile as the O atom is introduced into the carbocation, a protonated ester molecule with a C–O(H+)–C group and a C=C bond forms. Nonetheless, in the future, there is still a possibility of obtaining carbocations with a non-protonated C–O–C group. [ABSTRACT FROM AUTHOR]

X-ray diffraction analysis and IR spectroscopy were used to study the products of the interaction of vinyl cations C3H5+ and C4H7+ (Cat+) (as salts of carborane anion CHB11Cl11−) with basic molecules of water, alcohols, and acetone that can crystallize from solutions in dichloromethane and C6HF5. Interaction with water, as content increased, proceeded via three-stages. (1) adduct Cat+·OH2 forms in which H2O binds (through the O atom) to the C=C+ bond of the cation with the same strength as seen in the binding to Na in Na(H2O)6+. (2) H+ is transferred from cation Cat+·OH2 to a water molecule forming H3O+ and alcohol molecules (L) having the CH=CHOH entity. The O- atom of alcohols is attached to the H atom of the C=C+-H moiety of Cat+ thereby forming a very strong asymmetric H–bond, (C=)C+-H⋅⋅⋅O. (3) Finally all vinyl cations are converted into alcohol molecule L and H3O+ cations, yielding proton disolvates L-H+-L with a symmetric very strong H-bond. When an acetone molecule (Ac) interacts with Cat+, H+ is transferred to Ac giving rise to a reactive carbene and proton disolvate Ac-H+-Ac. Thus, the alleged high reactivity of vinyl cations seems to be an exaggeration. [ABSTRACT FROM AUTHOR]

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 SeO2 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 77Se NMR spectroscopy, two tentative mechanisms that feature isomeric transition states and intermediates are suggested for the reaction via ring-opening addition of SeO2 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. [ABSTRACT FROM AUTHOR]

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 λmax 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. [ABSTRACT FROM AUTHOR]

Abstract: According to the results of quantum chemical calculations at various levels of theory, an isolated molecule of the title compound prefers a non-planar Z,Z configuration, which is very similar to the configuration observed in the crystal. This is in contrast to its previously studied hydrocarbon analogue which features a planar Z,Z configuration, both in the crystal and as a calculated structure. Thus, the gas-phase molecular structures of these flexible compounds are resistant to the numerous intermolecular interactions in the solid state. The results obtained for the different molecular configurations and conformations of these compounds are in line with the qualitative bonding model suggested earlier for the isoelectronic [RNSN]− anions, taking into account of the anomeric interactions and the electron-acceptor strength of R. A number of additional factors operating on the molecular conformations of the title compound and its hydrocarbon analogue, such as the van der Waals volume of the ortho-substituents X (X=H,F) and improper H…O hydrogen bonds, are also discussed. [ABSTRACT FROM AUTHOR]

Abstract: New polyfluorinated Arph name="sbnd" />Se:glyph name="sbnd" />Se:hsp sp="0.25" />=4-RC6F4-1-yl, 5-HC5F3N-3-yl), non-symmetric Arph name="sbnd" />Ar′ (Ar=4-RC6F4-1-yl, Ar′=4-NC5F4-1-yl) and non-symmetric, i.e. chiral, Aryph name="dbnd" />O); (Ar=Ar=4-RC6F4-1-yl, Ar′=4-NC5F4-1-yl) derivatives, as well as (4-NC5F4-1-yl)SeNa, were prepared and characterized by single-crystal X-ray diffraction and multinuclear NMR (1H, 13C, 14N, 19F, 77Se). [Copyright &y& Elsevier]

A new general procedure for the selective synthesis of 1,2,5-thiadiazole 2-oxides (including fused derivatives) 8a,b,c,g,h from the reaction of vic-glyoximes with S2Cl2 and pyridine in acetonitrile was elaborated together with general procedure for the synthesis of 1,2,5-thiadiazoles 7a-i, 10, 12, and 14 from the same starting materials and reagents. Molecular structures of 3,4-dimethyl-1,2,5-thiadiazole 2-oxide 8a and [1,2,5]thiadiazolo[3,4-b]quinoxaline 10 were confirmed by single-crystal X-ray diffraction. Electrochemical properties of 1,2,5-thiadiazole 2-oxides 8 were studied by cyclic voltammetry and different behavior was observed for monocyclic and benzo-fused derivatives. With compounds 8g and 17, previously unknown deoxygenation of 2,1,3-benzothiadiazole 1-oxides was discovered by electrochemical reduction, and resulted 2,1,3-benzothiadiazoles 7g and 19 were detected in the forms of their radical anions by EPR spectroscopy combined with DFT calculations. [ABSTRACT FROM AUTHOR]

Interaction between Ph3P 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 Ph3P-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 Ph3As nor Ph3Sb reacted with 1 and 4. Molecular structures of 1a-5a and 5 were confirmed by X-ray diffraction (XRD). The crystals formed by chiral molecules of 2a-5a were racemic, whereas the crystal of 1a was formed by a single enantiomer. In all of the Ph3P-N-R derivatives, one of the Ph rings is oriented face-to-face to the hetero ring, R. Upon heating to 120 °C in squalane (1a, 3a, 4a) or dissolving in chloroform at ambient temperatures (1a, 2a, 4a), the Ph3P-N-R derivatives generated the 1,2,3-benzodithiazolyls (1b-4b, respectively) whose identity was confirmed by electron paramagnetic resonance (EPR). 2,1,3-Benzothiaselenazolyls 5b and 6b were detected by EPR as the main paramagnetic products of solution thermolysis of 5 and its 5,6,7,8-tetrafluoro congener (6), respectively. Passing a chloroform solution of 4a through silica column unexpectedly gave 5-6-6-6 tetracyclic (9) and 6-10-6 tricyclic (10) sulfur-nitrogen compounds, which were characterized by XRD. [ABSTRACT FROM AUTHOR]