N-[Amino(imino)methyl]uronium tetrafluoroborate

In the title compound, C2H7N4O+·BF4 −, inter­molecular N—H⋯O hydrogen bonds connect the cations into chains parallel to the c axis, with graph-set motif C(4). These chains are in turn connected into a three-dimensional network by inter­molecular N—H⋯F hydrogen bonds. The B—F distances distances in the anion are not equal

2-(2-Hydroxy­ethyl)-3-[(2-hydroxy­ethyl)imino]isoindolin-1-one

In the crystal structure of the title compound, C12H14N2O3, mol­ecules are packed into layers parallel to (100). Each layer contains centrosymmetric dimers formed by a pair of strong O—H⋯N hydrogen bonds with an R 2 2(10) motif, while strong O—H⋯O hydrogen bonds forming C(10) chains connect mol­ecules into a two-dimensional network. Additional stabilization is supplied by weak C—H⋯O hydrogen bonds and weak π–π stacking inter­actions with centroid–centroid distances in the range 3.4220 (7)–3.9616 (7) Å

Dipotassium zinc tetra­iodate(V) dihydrate

The title compound, K2Zn(IO3)4·2H2O, contains two symmetry-independent K and I atoms. These atoms, as well as the Zn atom, are coordinated by shared O atoms and, moreover, the Zn atom is coordinated by two water mol­ecules in trans positions. The K, Zn and water O atoms atoms are situated in special positions on twofold symmetry axes. The hydrogen atoms are involved in strong O—H⋯O hydrogen bonds and O—H⋯I inter­actions also occur. The crystals of the title compound are, in general, twinned, but the sample used for this experiment was free of twinning

(Tetra­oxidoselenato-κO)tris­(thio­urea-κS)zinc(II)

The title structure, [Zn(SeO4)(CH4N2S)3], is isomorphous with sulfatotris(thio­urea)zinc(II). In both structures, the Zn2+ cation is coordinated in a tetra­hedral geometry. The corresponding intra­molecular distances are quite similar except for the Se—O and S—O distances. Although the hydrogen-bonding patterns are similar, there are some differences; in the title structure all the H atoms are involved in the hydrogen-bond pattern, in contrast to the situation in sulfatotris(thio­urea)zinc(II). No reproducible anomalies were detected by differential scanning calorimetry in the range 93–463 K until decomposition started at the higher temperature

Tris(2-carbamoylguanidinium) hydrogen fluoro­phospho­nate fluoro­phospho­nate monohydrate

The title structure, 3C2H7N4O+·HFPO3 −·FPO3 2−·H2O, contains three independent 2-carbamoylguanidinium cations, one fluoro­phospho­nate, one hydrogen fluoro­phospho­nate and one water mol­ecule. There are three different layers in the structure that are nearly perpendicular to the c axis. Each layer contains a cation and the layers differ by the respective presence of the water mol­ecule, the hydrogen fluoro­phospho­nate and fluoro­phospho­nate anions. N—H⋯O hydrogen bonds between the guanylurea mol­ecules that inter­connect the mol­ecules within each layer are strong. The layers are inter­connected by strong and weak O—H⋯O hydrogen bonds between the anions and water mol­ecules, respectively. Inter­estingly, the configuration of the layers is quite similar to that observed in 2-carbamoylguanidinium hydrogen fluoro­phospho­nate [Fábry et al. (2012). Acta Cryst. C68, o76–o83]. There is also present a N—H⋯F hydrogen bond in the structure which occurs quite rarely

A redetermination from the original data of the crystal structure of 2-amino-4,6-dimethoxypyrimidin-1-ium 4-aminobenzoate

The title structure, C6H9.5N3O20.5+·C7H6.5NO20.5−, which might be named schematically as 2-amino-4,6-dimethoxypyrimidine-(μ2-hydrogen)-4-aminobenzoate to indicate a bridging H atom, has been redetermined from the data published by Thanigaimani, Muthiah & Lynch [Acta Cryst. (2006), E62, o2976–o2978]. The improvement of the present redetermination consists in a released geometry of the primary amine groups, which were originally assumed to be planar, as well as in a redetermination of the position of the hydroxy H atom. This H atom, whose parameters were originally constrained, turns out to be situated about the centre of the O...N hydrogen bond in two disordered positions with occupancies of 0.5 each

Dynamic Vehicle Routing Problems

Současné konkurenční prostředí nutí distribuční firmy zajišťovat bezprostřední obsluhu svých zákazníků. Zatímco statická verze okružních a rozvozních úloh nepřipouští možnost akceptovat dodatečné požadavky zákazníků, dynamická verze umožňuje dispečerovi měnit naplánované trasy vozidel, jakmile se objeví nový požadavek. Pro řešení dynamických úloh jsou navrženy optimalizační matematické modely a heuristické vkládací algoritmy. V některých úlohách jsou zahrnuty podmínky s časovými okny. V práci jsou analyzovány speciální distribuční úlohy: dynamická úloha kurýrní služby, dynamická úloha obchodního cestujícího s apriorní informací a dynamická rozvozní úloha s dělenou dodávkou. Řešení většiny úloh je demonstrováno na vygenerovaných datech za použití programu LINGO jako řešitele a VBA v MS Excel jako uživatelského rozhraní a výstupního prostředí. Jsou prezentovány výsledky počítačových experimentů

A resonance-assisted intramolecular hydrogen bond in compounds containing 2-hydroxy-3,5-dinitrobenzoic acid and its various deprotonated forms: redetermination of several related structures

A large number of structural determinations of compounds containing 2-hydroxy-3,5-dinitrobenzoic acid (I) and its various deprotonated forms, 2-hydroxy-3,5-dinitrobenzoate (II) or 2-carboxy-4,6-dinitrophenolate (III), are biased. The reason for the bias follows from incorrectly applied constraints or restraints on the bridging hydrogen, which is involved in the intramolecular hydrogen bond between the neighbouring carboxylic/carboxylate and oxo/hydroxy groups. This hydrogen bond belongs to the category of resonance-assisted hydrogen bonds. The present article suggests corrections for the following structure determinations that have been published in Acta Crystallographica: DUJZAK, JEVNAA, LUDFUL, NUQVEB, QIQJAD, SAFGUD, SEDKET, TIYZIM, TUJPEV, VABZIJ, WADXOR, YAXPOE [refcodes are taken from the Cambridge Structural Database [CSD; Groom et al. (2016). Acta Cryst. B72, 171–179]. The structural features of the title molecules in all the retrieved structures, together with structures that contain 3,5-dinitro-2-oxidobenzoate (IV), are discussed. Attention is paid to the localization of the above-mentioned bridging hydrogen, which can be situated closer to the O atom of the carboxylate/carboxylic group or that of the hydroxy/oxo group. In some cases, it is disordered between the two O atoms. The position of the bridging hydrogen seems to be dependent on the pKa(base) although with exceptions. A stronger basicity enhances the probability of the presence of a phenolate (III). The present article examines the problem of the refinement of such a bridging hydrogen as well as that of the hydrogen atoms involved in the hydroxy and primary and secondary amine groups. It appears that the best model, in many cases, is obtained by fixing the hydrogen-atom position found in the difference electron-density map while refining its isotropic displacement parameter

Bis(3-carbamoylpyridin-1-ium) phosphite monohydrate

Two of the constituent molecules in the title structure, 2C6H7N2O+·HPO32−·H2O, i.e. the phosphite anion and the water molecule, are situated on a symmetry plane. The molecules are held together by moderate N—H...O and O—H...N, and weak O—H...O and C—H...Ocarbonyl hydrogen bonds in which the amide and secondary amine groups, and the water molecules are involved. The structural features are usual, among them the H atom bonded to the P atom avoids hydrogen bonding

A long symmetric N...H...N hydrogen bond in bis(4-aminopyridinium)(1+) azide(1−): redetermination from the original data

The structure of the title molecular salt, C10H13N4+·N3−, has been redetermined from the data published by Qian & Huang [Acta Cryst. (2010), E66, o3086; refcode WACMIY (Groom et al., 2016)]. The improvement of the present redetermination consists in a correction of the site-occupancy parameter of the bridging H atom between the pyridine rings, as well as of its position. The present study has shown that the bridging H atom (site symmetry 2) is involved in a symmetric N...H...N hydrogen bond, which is one of the longest ever observed [N...N = 2.678 (3) Å]. In addition, there are also present weaker Nam—H...Naz hydrogen bonds (am = amine and az = azide) of moderate strength and π-electron pyridine...π-electron interactions in the structure. All the azide N atoms also lie on a twofold axis