An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

[1,2,5]Thiadiazolo[3,4-c][1,2,5]thiadiazole (1) is synthesized in 62% yield by fluoride ion-induced condensation of 3,4-difluoro-1,2,5-thiadiazole with (Me(3)SiN=)(2)S. The reversible electrochemical reduction of 1 leads to the long-lived [1,2,5]thiadiazolo[3,4-c][1,2,5]thiadiazolidyl radical anion (2) and further to the dianion (3). The radical anion 2 is also obtained by the chemical reduction of the precursor 1 with t-BuOK in MeCN. The radical anion 2 is characterized by ESR spectroscopy in solution and in the crystalline state. The stable salts [K(18-crown-6)][2] and [K(18-crown-6)][2].MeCN (8 and 9, respectively) are isolated from the spontaneous decomposition of the [K(18-crown-6)][PhXNSN] (6, X = S; 7, X = Se) salts in MeCN solution followed by XRD characterization. The radical anion 2 acts as a bridging ligand in 8 and as chelating ligand in 9. The structural changes observed by XRD in going from 1 to 2 are explained by means of DFT/(U)B3LYP/6-311+G calculations.

Attempts to prepare the bicyclic sulfur-nitrogen heterocycle t-BuCN5S3 via (NSCl)(3) and the corresponding silylated amidinates and amidines failed because of the inaccessibility of the silylated intermediates. Reactions of MN(SiMe3)(2) (M = Li, Na) with t-BuCN did not yield the expected amidinates t-BuC(NSiMe3)(2)M, instead the adducts [t-BuCN center dot MN(SiMe3)(2)](2) were isolated. The attempted synthesis of t-BuCN5S3 from t-BuCN(SiMe3)(2)M, prepared in situ from t-BuLi and Me3SiNCNSiMe3, and (NSCl)(3) unexpectedly resulted a mixture of S4N5Cl and S5N6. The crystal structure determination for S4N5Cl showed a new covalent modification of S4N5Cl (monoclinic, P2(1)/c, a = 1005.0(4) pm, b = 1193.5(8) pm, c = 1152.5(6) pin, beta = 93.67(3)degrees), different from the known ionic S4N5Cl (orthorhombic, Pnma, a = 1738.90(10) pm, b = 781.50(10) pm, c = 483.03(5)). The unsuccessful attempts to prepare t-BuCN5S3, the unexpected formation of S4N5Cl and S5N6, and the bonding properties of the new covalent modification of S4N5Cl are discussed.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The interaction of two flavonoid species (resorcinolic and fluoroglucinolic) with the 20 essential amino acids was studied by the multiple minima hypersurface (MMH) procedures, through the AM1 and PM3 semiempirical methods. Remarkable thermodynamic data related to the properties of the molecular association of these compounds were obtained, which will be of great utility for future investigations concerning the interaction of flavonoids with proteins. These results are compared with experimental and classical force field results reported in the available literature, and new evidences and criteria are shown. The hydrophilic amino acids demonstrated high affinity in the interaction with flavonoid molecules; the complexes with lysine are especially extremely stable. An affinity order for the interaction of both flavonoid species with the essential amino acids is suggested. Our theoretical results are compared with experimental evidence on flavonoid interactions with proteins of biomedical interest. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005

In order to reproduce the solvation effects on the monomers and dimers of naturally occurring flavonoid structures, a complete screening of their multiple minima hypersurfaces (MMH) was done by a semiempirical Hamiltonian. Such hypersurfaces corresponded to several solute–solvent supermolecules. This searching confirms some NMR results reported in the available literature and provides new theoretical evidences of these structures. The reaction energy of the flavonoid dimerization was calculated in this study, adding the corresponding terms related with the association process due to the presence of different solvents in the system. We are reporting the energetic and conformational analysis of all the possibilities of dimeric structures in different phases. The most important results of this work are related with the structural changes suffered by the monomeric and dimeric structures due to the presence of water and/or acetone molecules, the preferential position of interactions between solvent molecules and monomeric and dimeric structures, and the thermodynamic stability of dimeric structures in these phases.

The bicyclic sulfur-nitrogen heterocycle F3CCN5S3 (1) was investigated as a donor and acceptor toward H+, metal cations, and F−. Whereas the protonated species F3CCN5S3H+ AsF6 − (2) can be isolated, the product of the reaction with F− is unstable and decomposes among other products to TAS+ F3CCN5S3NC(NH2)CF3 − (3), which is isolated from this reaction in small amounts.

Some general guidelines for the generation of salts with high fluoride ion donor ability are discussed. A preliminary scale for a limited number of fluoride ion donors is presented, cations are classified according to their anion-cation interaction properties. Examples for fluoride ion transfer reactions are given and the influence of anion-cation interaction on the stabilisation of reactive anions is discussed. In our work mainly TAS fluoride (Me2N)(3)S+Me3SiF2- has been used as fluoride ion source: (a) for fluoride ion transfer to coordinatively unsaturated sulfur species, to SN and SO multiple bond systems, to SN, PN and CN heterocycles, (b) for the stabilisation of primary products of nucleophilic attacks and of intermediates in isomerisation processes or of intermediates in polymerisation processes, (c) for the generation of "naked" anions by silicon-element bond cleavage, and (d) for the activation of element-fluorine bonds by anion formation. (C) 2004 Elsevier B.V. All rights reserved.

With AsF5 F3CCN5S3 (1a) forms a 1:1 adduct F3CCN5S3.AsF5 (2), which slowly decomposes in CDCl3 solution to give [F3CCN4S3](+) [AsF6](-) (3) a salt with an cationic eight membered heterocycle. AsF5 attacks the bridging nitrogen atom, the nitrogen carrying the highest negative charge. By contrast, in the protonated compound [F3CCN5S3H](+) [AsF6](-) (6) one of the nitrogen atoms adjacent to the ring-carbon atom is attacked, which can be explained by different basicities of the nitrogen atoms. PPh3 and AsPh3 open the bicycles RCN5S3 (1) forming phosphanimino- and arsaniminotetrazocine derivatives RCN4S3N=EPh3 (R = F3C, E = P (endo), 4a; E = As (endo), 5a; R = Me2N, E = P (endo), 4c), respectively. The mechanism proposed for this reaction in the literature, is confirmed by the preparation of [TAS](+) [F3CCN5S3NC(NH2)CF3](-) (7). The structures of 2, 3, 4a, 4c, 5a, 6 and 7, determined by X-ray diffraction, will be discussed.(1))

One of the most interesting compounds in sulfur nitrogen fluorine chemistry is NSF2NS(O)F2 (3) (reported by Glemser and Höfer 30 years ago): in the NS backbone a triple and a double bond are connected by a single bond. Electrophiles (metal cations, fluoro Lewis acids, “CH3+”) attack this multifunctional system exclusively at the thiazyl nitrogen of the triple bond. [M(NSF2NS(O)F2)4][AsF6]2 (M=Ni (4b), Cu (4c)), [Re(CO)5(NSF2NS(O)F2)][AsF6]− (5), F5A·NSF2NS(O)F2 (A=As (6), Sb (7)), F3B·NSF2NS(O)F2 (8) and [H3CNSF2NS(O)F2]+[AsF6]− (9) were isolated. The X-ray structures of 4c, 6, 8 and 9 are reported, bonding in these complexes is compared with the recently reported related NSAr2NS(X)Ar2 (X=O, NH) species.

Flavonoids are polyphenolic compounds found in all land plants and in plant-related foods. These compounds have many positive effects, and the interaction with proline aminoacid is one of the most important characteristics. The present work shows the results of the application of the multiple minima hypersurfaces procedures, in the study of the interactions of flavonoid monomers (catechin and robinetinidin) with proline. These results are compared with experimental and classical theoretical results reported in the available literature. The most important results of this work are related with the conformations of monomers in these interactions, the preferential position of interactions and the thermodynamic stability of these complexes. All the results are successfully compared in both, gas and aqueous phases.

The series of bis(azolyl)sulfur derivatives OxS(az)(2) (x = 0,1,2; az = pyrazolyl (pz), 1,2,4-triazolyl (trz)) (1-6) is completed by the synthesis of S(pz)(2) (1) and O2S(pz)(2). The structures of compounds 1-6 and the structure of the co-crystallisate (C3N2H4+SbF6-.21) (7) were determined. In 1-6 the not S-bonded ring nitrogen atoms N2 are arranged in an anti position to each other, in 7 in a syn-position. These experimental findings agree with the results of RHF and B3LYP calculations. Both the experiments and the calculations show in the series S(az)(2)- OS(az)(2) - O2S(az)(2) for the sulfinyl derivatives a priori unexpected small NSN-angles and unexpected long SN-distances.

The syntheses of the title compounds RCN5S3 with electron-withdrawing aryl substituents [R = 2-FC6H4 (1m), 4-FC6H4 (1n), 2,6-F2C6H3 (1o), C6F5 (1p), 4-NCC6H4 (1q) and Cl3C (1r)] are described. The X-ray structures of 1n, 1o, 1q and 1r, together with those of Me2NCN5S3 (1b) and 4CH(3)C(6)H(4)CN(5)S(3) (1f), are reported. The experimentally determined dependence of the bond lengths on the substituents R within the bicyclic system RCN5S3 is well-reflected in the results of the theoretical calculations (RHF, MP2, B3LYP). The bonding model developed shows that acceptor substituents do not influence bonding within the bicycle. In the solid state, two fundamentally different primary interactions of the RCN5S3 molecules are observed; "stacking" and "dimerisation", which can be rationalised by electrostatic interactions between the CN5S3 units. However, secondary effects - the interactions between the R substituents - may be even more dominant.

In the OSF(4)/Me(2)NSiMe(3) system besides the long known Me(2)NS(O)F(3) only the trisubstituted derivative is isolated as (Me(2)N)(3)SO(+)Me(3)SiF(2)(-) (3). Similar to (Me(2)N)(3)S(+)Me(3)SiF(2)(-) compound 3 is an excellent fluoride ion donor. With AsF(5) and HF the corresponding hexafluoroarsenate (Me(2)N)(3)SO(+)AsF(6)(-) (4) and the hydrogen bifluoride (Me(2)N)(3)SO(+)HF(2)(-) (5) are formed in almost quantitative yield. X-ray structure determinations of 3-5 surprisingly showed two different types of structures for the cation. In 3 and 5 this cation has C(3) symmetry, while in the hexafluoroarsenate 4 a (Me(2)N)(3)S(+)-like structure with C(s)() symmetry is determined. The experimental results for (Me(2)N)(3)SO(+) and (Me(2)N)(3)S(+) are compared with theoretical calculations for these cations and their isoelectronic neutral counterparts, the phosphorus amides (Me(2)N)(3)PO and (Me(2)N)(3)P, respectively.

Air-sensitive, thermally unstable tris(dimethylamino)sulfonium (TAS) salts (3) of the title anions [ArNSN]- have been prepared from corresponding sulfurdiimides Ar-N=S=N-SiMe3 (2) by Si-N bond cleavage with [(Me2N)3S]-[Me3SiF2]- (TASF). They are characterized by low-temperature X-ray crystallography as Z isomers. Because of the very short terminal S-N distance (144.2 (3h)-147.9 (3i)pm) and the relatively long internal S-N distance (158.3 (3i)-160.3 (3c) pm) the [ArNSN]- ions should be regarded as thiazylamides 1b, rare species containing a S triple bond N triple bond. A bonding model is developed and the experimental results are compared with those of restricted Hartree-Fock (RHF), density functional theory (DFT), and Møller-Plesset second-order (MP2) calculations.

The syntheses of Az2S(O)F2 (AZ=pyrazole (7d), imidazole (7e), 1,2,4-triazole (7f) from OSF4 and the corresponding trimethylsilylazoles AzSiMe3 and the structures of 7d and f as well as those of [C6H5(CH3)N]2SF2 (3b) and CF3S(azole)SF2 (AZ=1,2,4-triazole) (3f) are reported, the structure of [(CH3)2N]2SF2 (3a) was re-determined at −100°C. The steric influence of the different substituents (F, CF3, NR2, azolide), of the oxidation state and of the lone pair (LP) in comparison with the doubly bonded oxygen is discussed.