[DBU‐H]+ and H2o as effective catalyst form for 2,3‐dihydropyrido[2,3‐d]pyrimidin‐4(1H)‐ones: A DFT Study

DFT investigations are carried out to explore the effective catalyst forms of DBU and H₂O and the mechanism for the formation of 2,3‐dihydropyrido[2,3‐d]‐pyrimidin‐4(1H)‐ones. Three main pathways are disclosed under unassisted, water‐catalyzed, DBU and water cocatalyzed conditions, which involves concerted nucleophilic addition and H‐transfer, concerted intramolecular cyclization and H‐transfer, and Dimroth rearrangement to form the product. The results indicated that the DBU and water cocatalyzed pathway is the most favored one as compared to the rest two pathways. The water donates one H to DBU and accepts H from 2‐amino‐nicotinonitrile ( 1 ), forming [DBU‐H]⁺‐H₂O as effective catalyst form in the proton migration transition state rather than [DBU‐H]⁺‐OH^?. The hydrogen bond between [DBU‐H]⁺···H₂O··· 1 ^? decreases the activation barrier of the rate‐determining step. Our calculated results open a new insight for the green catalyst model of DBU‐H₂O. © 2015 Wiley Periodicals, Inc.     

Ein ungewöhnliches H-Brückenbindungssystem in Rubidium-hydroxiddihydrat,RbOH · 2 H2O

An Unusual System of Hydrogen Bonds in Rubidium Hydroxide Dihydrate, RbOH · 2 H₂O RbOH · 2H₂O was obtained by the reaction of Rb with H₂O and dehydration of the resulting solution by concentrated sulfuric acid. The compound melts at 310 K. The structure was determined by X-ray single crystal methods: The H positions of H₂O were found. The structure consists of a threedimensional H-bonded network of H₂O molecules and OH^?ions. Hydroxide ions are acceptors for four protons of four adjacent water molecules with d(O? O) = 2×2.59 Å and 2×2.82 Å. Oxygen of OH-ions is disordered over a distance of 1.27 Å. Rb has 8 H₂O molecules as nearest neighbours, d(Rb? O) = 3.03 Å to 3.07 Å, OH^?ions are further removed with d(Rb? O) ≥ 3.45 Å.     

Ungewöhnliche H-Brückenbindungen in Natriumhydroxidmonohydrat: Röntgen- und Neutronenbeugung an NaOH · H2O bzw. NaOD · D2O

Unusual H-Bonds in Sodium Hydroxide Monohydrate: X-Ray and Neutron Diffraction on NaOH · H₂O and NaOD · D₂O, respectively X-ray data revealed the structure of NaOH · H₂O including the H positions. Neutron diffraction on microcrystalline NaOD · D₂O was used for comparison of H with D positions: The compound crystallizes in a layer-type structure with the sequence …? /O Na O O Na O/ …? closely related to that of hydrargillite Al(OH)₃ with …? /O 2/3 Al O O 2/3 Al O/ …?. Between OH^? ions as acceptors and H₂O molecules mäandric, one-dimensional infinite strong H-bonds occur with d(O…?O) = 2.66 Å and 2.69 Å. These lie within O-layers that coordinate Na⁺ ions. Bridge-bonds between OH^? ions as donors and H₂O molecules as acceptors connect the /O Na O/-layers with d(O…?O) = 3.18 Å.     

Tetrakis(chloromethyl)phosphonium chloride monohydrate

Tetrakis­(chloro­methyl)­phospho­nium chloride monohydrate, C₄H₈Cl₄P⁺·Cl^?·H₂O or P(CH₂Cl)₄⁺·Cl^?·H₂O, is the first crystal structure determination of a tetrakis­(halogeno­methyl)­phospho­nium compound to date. The only comparable structures known so far are of phospho­nium ions containing just one halogeno­methyl group. The solvent water mol­ecule interacts with the Cl^? anion via hydrogen bonds, with O?Cl distances of 3.230 (2) and 3.309 (2) Å. The structure also contains several C—H?Cl^? and C—H?O contacts, though with longer D?A distances [D?A 3.286 (3)–3.662 (2) Å] or bent D—H?A angles. For these reasons, the C—H?Cl^? and C—H?O interactions should not be considered as strong hydrogen bonds.     

Determination of the acid dissociation constants of p-benzohydroquinone by the INDO method

The stepwise acid dissociation constants for p-benzohydroquinone (QH₂) in aqueous media have been explicitly calculated for the first time, with the INDO parametrized SCF –MO method. We have optimized the geometries of QH₂, QH^?, and Q^2? and of the QH₂ · 6H₂O, QH^? · (H₃O⁺) · 5H₂O, and Q^2? · (H₃O⁺)₂ · 4H₂O systems that model the solvated species. The presence of the associated water molecules (and hydronium ions) account for the stabilization due to hydrogen bonding as well as for a part of the effect of interaction of these molecules with the respective reaction fields in an aqueous medium. To simulate the first solvation shell in a more complete manner, four more water molecules have been considered to be placed above and below the quinonoid ring and the optimized geometries of the resulting hydrated species, QH₂ · 10H₂O, QH^? · (H₃O⁺) · 9H₂O, and QH^? · (H₃O⁺) · 8H₂O, have been determined. The standard free-energy changes calculated for the dissociation of QH₂ into QH^? and H⁺ is 0.0251 Hartree (65.9 kJ mol^?1) and that of QH^? into Q^2? and H⁺ is 0.0285 Hartree (74.8 kJ mol^?1). Experimentally observed dissociation constants for these two steps correspond to free-energy changes of 0.0214 Hartree (56.2 kJ mol^?1) and 0.0248 Hartree (65.1 kJ mol^?1), respectively. © 1995 John Wiley & Sons, Inc.     

Hydrogen‐bonded bilayers in ­piperazinium(2+) bis(mandelate) bis(methanol) solvate

In the title compound, C₄H₁₂N₂²⁺·2C₈H₇O₃^?·2CH₄O, the cations lie across centres of inversion and are disordered over two orientations with equal occupancy; there are equal numbers of (R)‐ and (S)‐mandelate anions present (mandelate is α‐hydroxy­benzene­acetate). The anions and the neutral water mol­ecules are linked by O—H?O hydrogen bonds [O?O 2.658 (3) and 2.682 (3) Å, and O—H?O 176 and 166°] into deeply folded zigzag chains. Each orientation of the cation forms two symmetry‐related two‐centre N—H?O hydrogen bonds [N?O 2.588 (4) and 2.678 (4) Å, and N—H?O 177 and 171°] and two asymmetric, but planar, three‐centre N—H?(O)₂ hydrogen bonds [N?O 2.686 (4)–3.137 (4) Å and N—H?O 137–147°], and by means of these the cations link the anion/water chains into bilayers.     

Two cadmium(II) addition compounds with 3-hydroxy-2,7-naphthalenedisulfonate containing aromatic diamines and their 3-D net

{[CdCl(2,2′-bipy)₂(H₂O)]⁺·[Cd(3-O^?-2,7-NDS)(2,2′-bipy)₂]^?·3H₂O} (1) and {[Cd(phen)₃]²⁺·2[Cd(3-O^?-2,7-NDS)(phen)₂]^?·8.5H₂O} (2) (3-OH-2,7-NDS?=?3-hydroxy-2,7-naphthalenedisulfonate, phen?=?1,10-phenanthroline, and 2,2′-bipy?=?2,2′-bipydine) were prepared and characterized by X-ray single-crystal diffraction. Compound 1 contains a discrete coordination cation [CdCl(2,2′-bipy)₂(H₂O)]⁺ and a coordination anion [Cd(3-O^?-2,7-NDS)(2,2′-bipy)₂]^?; 2 contains a discrete coordination cation [Cd(phen)₃]²⁺ and two coordination anions [Cd(3-O^?-2,7-NDS)(phen)₂]^?. There are numerous weak interactions among the coordination cation, coordination anion, and free water molecules, such as O–H?···?O hydrogen bonds, π?···?π stacking, and Cl^??···?π interactions in 1 and π?···?π stacking and C–H?···?π interactions in 2. The cations and anions as building blocks are connected to construct different 3-D supramolecular architectures via weak intermolecular interactions. Particularly, the capsule structure of 1 was observed.     

Synthesis,spectroscopic properties,and antimicrobial activity of some new 5-phenylazo-6-aminouracil-vanadyl complexes

Six complexes, [VO(L¹-H)₂]?·?5H₂O (1), [VO(OH)(L^2,3?H)(H₂O)]?·?H₂O (2,3), [VO(OH)(L^4,5?H)(H₂O)]?·?H₂O (4,5), [VO(OH)(L⁶?H)(H₂O)]?·?H₂O (6), were prepared by reacting different derivatives of 5-phenylazo-6-aminouracil ligands with VOSO₄?·?5H₂O. The infrared and ¹H NMR spectra of the complexes have been assigned. Thermogravimetric analyses (TG, DTG) were also carried out. The data agree quite well with the proposed structures and show that the complexes were finally decomposed to the corresponding divanadium pentoxide. The ligands and their vanadyl complexes were screened for antimicrobial activities by the agar-well diffusion technique using DMSO as solvent. The minimum inhibitory concentration (MIC) values for 1–4 and 6 were calculated at 30°C for 24–48?h. The activity data show that the complexes are more potent antimicrobials than the parent ligands.     

Supramolecular architecture built of Co(II) and a tripodal ligand containing 1-D water tapes with (H2O)16 cluster units

The reaction of Co(NO₃)₂?·?6H₂O with a tripodal ligand leads to a new complex {[Co(L)]?·?2NO₃?·?8H₂O} (1) confirmed by single-crystal X-ray diffraction, infrared spectroscopy, and elemental analysis. The particular interest of 1 is in the formation of a 1-D water tape consisting of (H₂O)₁₆ cluster units, the neighboring water tapes are connected by free nitrate anions via hydrogen bonds into a 2-D guest layer. These guest layers are alternately packed face-to-face with the 2-D host layers along the a-axis to form a 3-D supramolecular architecture. There exist C–H?···?N and C–H?···?O weak hydrogen bonds between the guest layer and host layer. These weak hydrogen bonds and water–nitrate, water–water hydrogen bonds are important for the stability of the overall structure.     

Self-assembly of copper(II) complexes with substituted aroylhydrazones and monodentate N-heterocycles: synthesis,structure and properties

Two ternary copper(II) complexes [Cu(L¹)(py)] (1) and [Cu(L²)(Himdz]?·?CH₃OH (2) with substituted aroylhydrazones, 5-bromo-salicylaldehyde-3,5-dimethoxy-benzoylhydrazone (H₂L¹) and 5-bromo-salicylaldehyde-p-methyl-benzoylhydrazone (H₂L²), pyridine (py) and imidazole (Himdz), have been synthesized. Their crystal structures and spectroscopic properties have been studied. In each complex, the metal is in a square-planar N₂O₂ coordination formed by the phenolate-O, the imine-N and the deprotonated amide-O atoms of L^2?, and the sp²?N atom of the neutral heterocycle. In the solid state, 1 exists as a centrosymmetric dimer due to very weak apical coordination of the metal bound phenolate-O. Complex 2 has no such apical coordination and exists as a monomer. Self-assembly via C–H?···?O, N–H?···?O and O–H?···?N interaction leads to a one-dimensional chain arrangement; other non-covalent interactions such as C–H?···?π and π?···?π are not involved.     

A tetradentate bisoxime and its supramolecular nickel(II) cluster: synthesis,crystal structure,and spectral properties

Salen-type bisoxime 5,5′-dimethoxy-2,2′-[(ethylenedioxy)bis(nitrilomethylidyne)]diphenol (H₂L) and its trinuclear Ni(II) cluster {[(NiL)(n-BuOH)]₂(μ-OAc)₂Ni}?·?n-BuOH have been synthesized and structurally characterized. The structure of H₂L adopts an L-shape conformation where the two salicylaldoxime moieties are well separated. In the trinuclear Ni(II) cluster, two acetates coordinate to three Ni(II)'s through Ni–O–C–O–Ni bridges, four μ-phenoxos from two [NiL(n-BuOH)] units also coordinate to Ni(II), and two n-butanols coordinate to two terminal Ni(II)'s forming a distorted octahedral geometry. The Ni–O–C–O–Ni and μ-phenoxo bridges play important roles in assembling Ni(II) and the ligands. H₂L forms a rectangle-like large cave structure through O–H?···?N, C–H?···?O, and C–H?···?π hydrogen-bond interactions, whereas its trinuclear Ni(II) cluster exhibits a 3-D supramolecular network structure through intermolecular O–H?···?O, C–H?···?O, and C–H?···?π hydrogen-bond interactions.     

Polarographic waves of tri-n-butyl phosphate and polarographic determination of uranium in the presence of tri-n-butyl phosphate

The results of a study on the polarographic behaviour of TBP and its influence on the determination of uranyl ions is presented. The half-wave potential of the adsorption wave of TBP depends on the concentration of TBP, type of supporting elec trolyte and its concentration. In the presence of TBP the polarographic wave of U(VI) ion is changed. Below 7·10^?5 M TBP the polarographic wave of U(VI) is not affected, between 7·10^?5 and 2·10^?4 M TBP the shape, height and half-wave potential of U(VI) waves are changed and above 2·10^?4 M, up to saturated solution of TBP, the waves of U(VI) do, not change further. The bes supporting electrolytes for the determination of U(VI) are KNO₃ or NaClO₄ in concentrations of 0.1 to 0.5 M, pH 1–2 and TBP concentrations from 3·10^?4 to 1.2·10^?3 M.     

The C—H⃛O hydrogen bond in (di­cyano­methyl)­ammonium p‐toluene­sulfonate

In the title compound, C₃H₄N₃⁺·C₇H₇O₃S^?, the activated C—H group of the cation forms a short but bent C—H?O hydrogen bond with a sulfonate O atom of the anion; C?O = 3.075 (5) Å and C—H?O = 130°.     

Supramolecular networks constructed by cationic copper(II) complexes incorporating hybrid water–anionic polymeric assemblies

Two complexes, [Cu₂(TFSA)(2,2′-bpy)₄]?·?TFSA?·?8H₂O (1) and {[Cu(4,4′-bpy)(H₂O)₂]?·?TFSA?·?6H₂O} _n (2) (H₂TFSA?=?tetrafluorosuccinic acid, 2,2′-bpy?=?2,2′-bipyridine, and 4,4′-bpy?=?4,4′-bipyridine), have been synthesized and structurally characterized by X-ray structural analyses. Complex 1 is a binuclear molecule bridged by TFSA ligands; 2 is a 1-D chain bridged by 4,4′-bpy ligands. The asymmetric units of the two complexes are composed of cationic complexes [Cu₂(TFSA)(2,2′-bpy)₄]²⁺ (1) and [Cu(4,4′-bpy)(H₂O)₂]²⁺ (2), free TFSA anion, and independent crystallization water molecules. A unique 2-D hybrid water–TFSA anionic layer by linkage of {[(H₂O)₈(TFSA)]^2?} _n fragments consisting of 1-D T6(0)A2 water tape and TFSA anionic units by hydrogen bonds in 1 was observed. Unique 2-D hybrid water–TFSA anionic layer generated by the linkage of {[(H₂O)₆(TFSA)]^2?} _n fragments consisting of cyclic water tetramers with appended water molecules and TFSA anionic units, and 1-D metal–water tape [Cu–H₂O?···?(H₂O)₆?···?H₂O^?] _n in 2 were found. 3-D supramolecular networks of the two complexes consist of cationic complexes and water–TFSA anionic assemblies connected by hydrogen bonds.     

Piperazine‐1,4‐diium–2,4‐dinitrophenolate–water (1/2/2)

In the title 1/2/2 adduct, C₄H₁₂N₂²⁺·2C₆H₃N₂O₅^?·2H₂O, the dication lies on a crystallographic inversion centre and the asymmetric unit also has one anion and one water mol­ecule in general positions. The 2,4‐di­nitro­phenolate anions and the water mol­ecules are linked by two O—H?O and two C—H?O hydrogen bonds to form molecular ribbons, which extend along the b direction. The piperazine dication acts as a donor for bifurcated N—H?O hydrogen bonds with the phenolate O atom and with the O atom of the o‐nitro group. Six symmetry‐related molecular ribbons are linked to a piperazine dication by N—H?O and C—H?O hydrogen bonds.     

Syntheses and crystal structures of two Co(II) coordination polymers based on 4,6-bis(4-methylbenzoyl)isophthalic acid and 4,4′-bipyridine

Two coordination complexes, [Co₂L₂(4,4′-bpy)₂(H₂O)₄]?·?6H₂O (1) and [CoL(4,4′-bpy)] (2) (H₂L?=?4,6-bis(4-methylbenzoyl)isophthalic acid and 4,4′-bpy?=?4,4′-bipyridine), have been synthesized with the same starting materials under conventional and hydrothermal condition, respectively. Their structures have been characterized by X-ray diffraction, elemental analysis, IR spectra, and thermogravimetric analysis. Complex 1 features a 2-D sheet structure (space group C2/c) with (4,4) grid units. The non-covalent interactions (O–H?·?·?·?O, C–H?·?·?·?π, and weak π??·?·?·?π interactions) extend 1 into a 3-D supramolecular network. Complex 2 displays a (3,5)-connected network (space group P 1) with a (4²?·?6)(4²?·?6⁸) topology.     

Zinc(ΙΙ) complexes with 5,6-dihydro-1,4-dithiin-2,3-dicarboxylic anhydrate and different N-donors: syntheses,crystal structures,and emission properties

Two new Zn^II complexes, {[Zn(L)(phen)(H₂O)]?·?H₂O}_∞ (1) and {[Zn(L)(4bpy)(H₂O)]?·?H₂O}_∞ (2) (L?=?5,6-dihydro-1,4-dithiin-2,3-dicarboxylate, phen?=?1,10-phenanthroline, and 4bpy?=?4,4′-bipyridine), have been prepared by in situ reaction of Zn(ClO₄)₂?·?6H₂O with 5,6-dihydro-1,4-dithiin-2,3-dicarboxylic anhydrate in the presence of lithium hydroxide, together with incorporating chelating phen or bridging 4bpy as co-ligands. Their structures were determined by single-crystal X-ray diffraction. Complex 1 takes a 1-D helical structure that is further assembled into a 2-D network by O–H?···?O, C–H?···?O hydrogen bonds, and weak S?···?S interactions, and then an overall 3-D supramolecular framework was formed by π?···?π stacking interactions. Complex 2 possesses a 2-D (4,4)-layered structure. The structural difference between 1 and 2 can be attributed to the different N-donor auxiliary co-ligands. Both 1 and 2 are photoluminescent materials whose emission properties are closely related to their intrinsic structure.     

Chlor­amine‐B sesquihydrate

In the title compound, sodium N‐chloro­benzene­sulfon­amide sesquihydrate, Na⁺·C₆H₅ClNO₂S^?·1.5H₂O, the sodium ion exhibits octahedral coordination by O atoms from three water mol­ecules and by three sulfonyl O atoms of three different N‐­chloro­benzene­sulfon­amide anions. A two‐dimensional polymeric layer consists of units, each comprising two face‐sharing octahedra which share four corners with four other such units, the layer running parallel to the ab plane. The water mol­ecules participate in hydrogen bonds of the types O—H?O, O—H?N and O—H?Cl.     

Hydro­gen bonding in ethyl­ene­di­ammonium bis­(hydrogen malonate) mono­hydrate

In the title compound, C₂H₁₀N₂²⁺·2C₃H₃O₄^?·H₂O, the hydrogen malonate anion has an intramolecular O—H?O hydrogen bond of 2.430 (2) Å. The water mol­ecule lies on a twofold axis and connects the anions into pairs through hydrogen bonds of 2.734 (1) Å. The ethyl­enedi­ammonium cation lies across an inversion centre. Each of the ammonium protons is involved in hydrogen bonding to an anion or a water mol­ecule [N?O 2.815 (2)–2.875 (2) Å].     

π–π Stacking,hydrogen bonding and anti-ferromagnetic coupling mechanism on a mononuclear Cu(II) complex

Weak anti-ferromagnetic coupling is observed in a mononuclear copper(II) complex, [Cu(Pid)(OSO₃)(H₂O)]?·?(H₂O) (Pid?=?2,2′-(1,10-phenanthrolin-2-ylimino)diethanol). The Cu(II) complex is a distorted square pyramid. Analysis of the crystal structure indicates that there are two types of magnetic coupling pathways, where one pathway involves π–π stacking between adjacent complexes and the second one involves the O–H?···?O hydrogen bonds between adjacent complexes. The variable-temperature magnetic susceptibilities show that there is a weak anti-ferromagnetic coupling between adjacent Cu(II) ions with Curie–Weiss constant θ?=??13.71?K?=??9.93?cm^?1. Theoretical calculations reveal that the π–π stacking resulted in anti-ferromagnetic coupling with 2J?=??6.30?cm^?1, and the O–H?···?O hydrogen-bonding pathway led to a weaker anti-ferromagnetic interaction with 2J?=??3.38?cm^?1. The theoretical calculations also indicate that anti-ferromagnetic coupling sign from the π–π stacking accords with the McConnell I spin-polarization mechanism.