Structural,electrochemical, and adsorption studies of Ni and Zn benzylimidazole coordination polymers with terephthalate linkers

Two coordination polymers, [Ni(bim)₂(L1)(H₂O)₂] _n (CP-1) and [Zn(bim)(L1)(Cl)] _n (CP-2) (bim = 1-benzylimidazole, L1 = terephthalic acid), were synthesized and characterized by physicochemical and spectroscopic methods. The Ni(II) center in CP-1 is octahedral, while the Zn(II) center in CP-2 is tetrahedral. CP-1 and CP-2 were used to modify carbon paste electrodes to assess their effect on the electrochemical behavior of ferricyanide. The redox reactions of ferricyanide on both electrodes proved to be reversible and diffusion controlled, with ferricyanide diffusion coefficients for CP-1 and CP-2 of 1.88 × 10⁵ and 3.44 × 10⁵ cm² s^?1, respectively. These coordination polymers were also investigated for their adsorption behavior toward two dyes: Chicago sky blue and methylene blue. CP-1 and CP-2 both rapidly adsorbed the anionic Chicago sky blue dye by different intermolecular interactions; in contrast, the cationic methylene blue dye was adsorbed to a lesser extent. The adsorption of these CPs depends on the charge but not the size of the dye. Addition of methanolic potassium nitrate solution caused the release of the adsorbed dyes.     

Syntheses,structures, and catalytic activity in Friedel–Crafts acylations of substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes

Reactions of the substituted tetramethylcyclopentadienes [C₅HMe₄R] [R =  ^t Bu, Ph, CH₂CH₂C(CH₃)₃] with Mo(CO)₃(CH₃CN)₃ in refluxing xylene gave a series of dinuclear molybdenum carbonyl complexes [(η⁵-C₅Me₄R)Mo(CO)₃]₂ [R =  ^t Bu (1), Ph (2), CH₂CH₂C(CH₃)₃ (3)], [(η⁵-C₅Me ^t Bu)Mo(μ-CO)₂]₂ (4)], and [(η⁵-C₅Me₄) ^t Bu]₂Mo₂O₄(μ-O) (5)], respectively. Complexes 1–5 were characterized by elemental analysis, IR, ¹H NMR, and ¹³C NMR spectroscopy. In addition, their crystal structures were determined by X-ray crystal diffraction analysis. The catalytic activities of complexes 1–3 in Friedel–Crafts acylation in the presence of o-chloranil has also been investigated; the reactions were achieved under mild conditions to give the corresponding products in moderate yields.     

Synthesis,crystal structures and catalytic properties of three-dimensional nickel(II) and manganese(II) coordination polymers with dicarboxylate and semi-rigid bis(imidazole) ligands

Two coordination polymers (CPs), namely [Ni(L)(chdc)] _n (1) and [Mn(L)(ndc)(H₂O)] _n (2) (L = 4,4′-bis(imidazol-1-ylmethyl)biphenyl, H₂chdc = 1,2-cyclohexanedicarboxylic acid, H₂ndc = 2,6-naphthalenedicarboxylic acid), have been hydrothermally synthesized and characterized by physicochemical and spectroscopic methods and also by single-crystal diffraction. Both CPs feature 3D-diamond-like networks with point symbol of 6⁶; CP-1 displays a 2-fold interpenetrated net, while CP-2 presents a non-interpenetrated framework. The thermal stabilities, solid-state luminescence properties and catalytic activities of both CPs for degradation of methyl orange in a Fenton-like process were investigated.     

Thermal properties and crystallization of MgO–FeO<Subscript>x</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript> glasses

Five novel bridged heptaphenyl polyhedral oligomeric silsesquioxanes (POSSs), in which two identical silicon cages R₇(SiO_1.5)₈ (with R = Phenyl) are linked to various aliphatic [(CH₂) _n with n = 2, 6 and 10] and aromatic (Ar–Ar and Ar–O–Ar, where Ar = p-C₆H₄) bridges, were synthesized. The obtained compounds were characterized by elemental analysis and ¹ H NMR spectroscopy, and the results were in very good agreement with those of expected products. The synthesized heptaphenyl POSSs were thermally degraded, in dynamic heating conditions (25–700 °C), in both flowing nitrogen and static air atmosphere. The temperatures at 5% mass loss (T _5%) and residues at 700 °C were thus determined to evaluate their resistance to thermal degradation, but no substantial difference was found between the values in the two studied environments. The obtained T _5% values were much higher than those of the corresponding isobutyl and cyclopentyl POSSs we investigated in the past. Also, the T _5% values of the phenyl POSSs with aliphatic bridges decreased quite linearly on increasing the number of bridge carbon atoms (n _C). This behaviour was interpreted and attributed to the presence of the external corona formed by voluminous phenyl groups. The residue at 700 °C, which was largely higher than those of the corresponding isobutyl and cyclopentyl POSSs, was a further confirmation of the better thermal stability of the compounds here studied.     

Synthesis and catalytic activity of rhenium carbonyl complexes containing alkyl-substituted tetramethylcyclopentadienyl ligands

A series of six alkyl-substituted tetramethylcyclopentadienyl mononuclear metal carbonyl complexes [(η ⁵-C₅Me₄R)Re(CO)₃] [R = allyl (1), i-Pr (2), n-butyl (3), t-butyl (4), benzyl (5), CH(CH₂)₄ (6)] have been synthesized by treating the corresponding ligands (C₅Me₄R) [R = allyl, i-Pr, n-butyl, t-butyl, benzyl, CH(CH₂)₄] with Re₂(CO)₁₀ in refluxing xylene. The six new complexes were characterized by elemental analysis, IR, ¹H NMR and ¹³C NMR spectroscopy. The crystal structures of all six complexes were determined by X-ray crystal diffraction analysis, showing that they have similar molecular structures, being mononuclear carbonyl complexes. In each of these complexes, the Re atom is η ⁵ -coordinated to the cyclopentadienyl ring. Complexes 1–5 have significant catalytic activity in Friedel–Crafts reactions of aromatic compounds with alkylation reagents. Compared with traditional catalysts, these mononuclear rhenium carbonyl complexes have obvious advantages such as lower amounts of catalyst, mild reaction conditions and environmentally friendly chemistry.     

Influence of solvent environment using the CPCM model on the H-bond geometry in the complexes of phosphorus acids with DMSO

Quantum chemical calculations of structure and energies of various H-bonded complexes of phosphoric, phosphorous and methylphosphonic acids and their dimers with dimethylsulfoxide (DMSO), i.e., (acid) _n –DMSO and acid–(DMSO) _m for n = 1, 2 and m = 2, 3 have been carried out. The polar solvent effect is taken into account by using the CPCM model. It has been found that in DMSO environment the H-bonds in all complexes of investigated acid with DMSO are sizably stronger than the ones in the gas phase. At B3LYP-CPCM computation, the H-bonds between all investigated acid dimers and DMSO are significantly shorter than those found for complexes of corresponding acids with other compositions. The H-bonding interaction in acid–(DMSO) _m for m = 1–3 becomes slightly weaker with increasing number DMSO molecules. The strength of the H-bond in all investigated complexes increases in the series of acids: (HO)₂MePO < (HO)₂P(O)H < H₃PO₄. Additionally, quantum theory of ‘atoms in molecules’ and natural bond orbitals method have been applied to analyze H-bond interactions.     

Preparation,crystal structure and characterization of 2,4,6-trinitro-3,5-dimethylbenzoic acid monohydrate

In the present work, we synthesized 2,4,6-trinitro-3,5-dimethylbenzoic acid (TNDMBA). Single crystal of TNDMBA·H₂O was cultured from aqueous solution using a slow evaporation method at 30°C. The crystal structure was determined by X-ray single-crystal diffraction analysis. The crystal belongs to the monoclinic system with space group P2(1)/c having unit cell parameters of a = 17.24(3) Å, b = 6.032(1) Å, and c = 16.359(4) Å. There are two kinds of intermolecular H-bond interactions between H₂O and TNDMBA, which is different from typical carboxylic acids that form H-bond dimers across crystallographic centers of inversion. The title compound was characterized by FT-IR, DSC, and TG-DTG technologies, and calculated by using density functional theory (DFT) method. The calculated results show that the structural parameters from the theory are close to those of the crystal structure from the experiments. The compound is composed of three nitro groups and one carboxyl group, and it can be used as a potential energetic combustion catalyst in industry.     

An azide-bridged copper(II) 1D-chain with ferromagnetic interactions: synthesis,structure and magnetic studies

A coordination polymer of formula [Cu(μ _1,3-N₃)₂(imH)₂] _n (1) has been synthesized by reaction of Cu(NO₃)₂ with imidazole and sodium azide in CH₃OH/CH₃CN. The complex was characterized by FTIR, elemental analysis, powder diffraction, thermogravimetric analysis, magnetic measurements, and single-crystal X-ray diffraction. The X-ray crystal structure shows that the Cu(II) centers have a distorted octahedral coordination geometry, being coordinated by two imidazole ligands at the trans positions. Each azide links two [Cu(imH)₂]²⁺ units to form 1D zigzag chains. Variable-temperature magnetic susceptibility studies at low field reveal dominant intrachain ferromagnetic/antiferromagnetic interactions. Using a model with n = 10, the coupling parameters J _AF = ?2.95 and J _F = 17.99 with g = 2.12 have been determined.     

Preparation,characterization, and structural analysis of d8 palladium and platinum compounds containing amino acid ester derivatized diimine ligands. Observation of liquid crystal behavior

Eight new compounds, M(pyca(CH₂)_xCOOR)Cl₂, M = Pd, Pt; R = Me, Et; x = 2, 3, 5, 11, were prepared. The resulting new complexes were characterized by ¹H and ¹³C NMR spectroscopy and each was also structurally elucidated by X-ray crystallography. The compounds share general structural features, but there are differences in the alignment of the alkyl chain; as the chain lengthens, the chain straightens relative to the plane of the metal complex. For the dodecanoic ester derivatives, a nearly linear alkyl chain was observed. These longer alkyl derivatives show mesogenic behavior.     

Effect of alkali metal salts on decomposition of ionic liquid like organic salt

N ¹,N ¹,N ²,N ²-tetramethylethane-1,2-diamine-based ionic salts (TMEDA), N ¹,N ¹,N ¹,N ²,N ²,N ²-hexamethylethane-1,2-diaminium dicyanamide (HMEDA-(DCA)₂) were prepared following the quaternization and subsequent ion exchange. The chemical structure of the HMEDA-(DCA)₂ was confirmed using ¹³C NMR spectrum and elemental analysis. The corresponding viscosity of its 60 wt% solution was found to be lower than 5 cP at room temperature, which was critical for propellant application. The ignition delay of 40 wt% HMEDA-(DCA)₂ solution was decreased to 20–30 ms dramatically using alkali metal salts, Li(CH₃COO), Mg(CH₃COO)₂, and Ca(CH₃COO)₂ as a co-catalyst when white fume nitric acid was utilized as an oxidizer.     

Synthesis of Polyfluorinated Ethers

Procedures for preparing polyfluorinated ethers H(CF₂CF₂) _n CH₂OR by alkylation of the corresponding telomeric alcohols H(CF₂CF₂) _n CH₂OH (n = 1–3) with alkyl halides and alkyl tosylates were examined.     

Effect of mixed thiols on the adsorption,capacitive and hybridization performance of DNA self-assembled monolayers on gold

In this article, we investigated the effect of mixed thiols (HS(CH₂)₅CH₃, HS(CH₂)₆OH and HS(CH₂)₂NH₂) on the adsorption, capacitive and hybridization performance of thiol-modified probe DNA self-assembled monolayers on gold by chronocoulometry (CC) and cyclic voltammetry (CV). Co-assembly of HS(CH₂)₅CH₃ with probe DNA availed DNA surface adsorption on gold more than HS(CH₂)₆OH and HS(CH₂)₂NH₂. With the increase of the assembly concentration ratio of probe DNA and mixed thiols (C _DNA/C _thiols), DNA surface coverage (Γ _m) was almost constant for DNA/HS(CH₂)₅CH₃ mixed SAMs and increased gradually for DNA/HS(CH₂)₆OH or DNA/HS(CH₂)₂NH₂ mixed SAMs. Interfacial capacitance (C _d) value of DNA/thiol-mixed SAMs on gold mainly depended on the capacitance of thiols SAMs. DNA hybridization almost did not change the capacitance value of DNA/thiol-mixed SAMs on gold. Hybridization experiments indicated that the maximal DNA hybridization density (H _D) was 1.2 × 10^?11 and 1.1 × 10^?11 mol cm^?2 with HS(CH₂)₅CH₃ or HS(CH₂)₆OH as mixed thiols respectively, much bigger than that with short-chain thiols (HS(CH₂)₂NH₂). The size fitting coefficient d _c/d _t values for the optimal hybridization of DNA/HS(CH₂)₅CH₃ and DNA/HS(CH₂)₆OH mixed SAMs were 0.70 and 0.93, respectively. This indicated that probe DNA with much bigger Γ _m should be co-assembled with HS(CH₂)₅CH₃ on gold to obtain the biggest H _D than with HS(CH₂)₆OH. These conclusions provided the important reference for optimally designing DNA sensor.     

Solvent,substituent, and dimerization effects on the ring-opening mechanisms of monosilacyclopropylidenoids: a theoretical study

Density functional theory and ab initio computations elucidated the ring-opening of substituted (R = –CF₃, –CN, –CH₃, –H, –NH₂, –OCH₃, –OH, –SiH₃) 1-bromo–1-lithiosilirane 1 and 2-bromo–2-lithiosilirane 2 to LiBr complexes of 2-silaallene and 1-silaallene, respectively. Formally, two competitive pathways can be considered. The ring-opening reaction can take place through a concerted manner via TS3. Alternatively, the reaction may proceed in a stepwise fashion with the intermediacy of a free silacyclopropylidene–LiBr complex 7. In both cases, the position of the substituents determines the kinetic of the reactions. The structures with an electron-donating group are generally unstable, whereas the silacyclopropylidenoids bearing electron-withdrawing substituents are particularly stable species. Here, we propose the ring-opening of 5a–h to corresponding LiBr complexes of 2-silaallenes can proceed in both concerted and stepwise mechanism except for –H, –CH₃, and –SiH₃. The obtained activation energies for the ring-openings of 5a–h to related 2-silaallenes are too high for a reaction at room temperature with up to 61.4 kcal/mol. In contrast, the activation energy barriers for the isomerization of 6a–h to the LiBr complexes of 1-silaallenes was determined to be relatively low at the B3LYP/6-31+G(d,p), M06/6-31+G(d,p), and MP2/6-31+G(d,p) levels. Moreover, we have also investigated the solvent effect on the unsubstituted models using both implicit and explicit solvation models. The energy barriers of the solvated models are found to be slightly higher than the results of gas phase calculations. Additionally, the ring-opening of dimer 6 (6–Dim) is also calculated for the ring-opening mechanism with the energy barrier of 3.7 kcal/mol at B3LYP/6-31+G(d,p) level of theory.     

Studies on bis(1′-ortho-carboranyl)benzenes and bis(1′-ortho-carboranyl)biphenyls

Reactions between the C,C′-dicopper(I) derivative of ortho-carborane and ortho-, meta- and para-diiodobenzene are reported. The reaction with 1,2-C₆H₄I₂ unexpectedly afforded 2,2′-bis(1′-ortho-carboranyl)biphenyl, [HCB₁₀H₁₀CC₆H₄]₂2, whereas reactions with 1,3- or 1,4-C₆H₄I₂ provided alternative routes to 1,3-bis(1′-ortho-carboranyl)benzene 3 and 1,4-bis(1′-ortho-carboranyl)benzene 4, respectively. The crystal structure of the biphenyl derivative 2 revealed significant distortions in the biphenylene framework attributable to the proximity of the two bulky carborane cages. UV absorption spectra and electrochemical data on 2 and 3 showed little electronic communication between the two carborane cages in either, and negligible π-conjugation between the two ortho-phenylene rings in 2. However, substantial evidence was found of electronic communication between the carborane cages via the para-phenylene bridge in 4. B3LYP/6-31G^∗ computations have been carried out on compounds 2 and 4, on 4,4′-bis(ortho-carboranyl)biphenyl 6 and on 1,2-bis(1′-ortho-carboranyl)benzene 7. Those on 2, 4 and 6 show the computed geometries to be in very good agreement with the experimental geometries: those on 7 allowed the reported molecular geometry of this compound to be revised and revealed a long cage C–C bond of 1.725(3) Å.     

Crystal structures of 1,1,1-trifluoro-4-hydroxy-4-phenyl-but-3-en-2-one, 2,2,6,6-tetramethyl-3-hydroxy-hept-3-en-5-one, 2,2,6,6-tetramethyl-3-methylamino-hept-3-en-5-one and a study of the ability of these ligands to complex formation with metals

Crystal structures are determined (Bruker Nonius X8 Apex, 4K CCD-detector, λMoK _α, graphite monochromator, T 150 K and 293 K) for two β-diketones F₃CC(O)CH₂C(O)Ph (1) (space group P2₁/c, a = 7.0713(3)Å, b = 11.5190(6)Å, c = 11.3602(6) Å, β = 99.405(2)°, V = 912.90(8) ų, Z = 4), (CH₃)₃CC(O)CH₂C(O)C(CH₃)₃ (2) (space group Pbca, a = 11.5536(8) Å, b = 11.5796(10) Å, c = 17.2523(13) Å, V = 2308.1(3) ų, Z = 8) and a ketoimine (CH₃)₃CC(NCH₃)CH₂C(O)C(CH₃)₃ (3) (space group I4₁/a, a = 18.7687(6) Å, b = 18.7687(6) Å, c = 14.5182(6) Å, V = 5114.2(3) ų, Z = 16). All structures are molecular and comprise isolated molecules joined by van der Walls interactions. The substitution energy of a Na atom for a hydrogen atom in free ligands is calculated by the hybrid B3LYP quantum chemical method. A successful preparation of Na(I) chelates with ligands 1, 2 and failed attempts to prepare a complex with ligand 3 are in accordance with the calculations. Geometrical simulation of a copper(II) complex with ligand 3 reveals the overlap of CH₃ groups which hinders the complexation.     

Theoretical kinetic investigation of thermal decomposition of nitropropane

The thermal decomposition of nitropropane (CH₃CH₂CH₂NO₂) has been investigated at the CBS-QB3 level of theory. The pyrolysis of CH₃CH₂CH₂NO₂ mainly includes the simple bond ruptures mechanism, hydrogen abstraction processes, isomerization and secondary reactions. As a result, for the simple bond ruptures mechanism, the formation of \({\text{CH}}_{3} {\text{CH}}_{2} {\text{CH}}_{2}^{\cdot} +\,^{\cdot}{\text{NO}}_{2}\) products is dominant with the energy barrier of 49.77 kcal mol^?1. The process of H atom on the β–CH₂ abstracted by one O atom of NO₂ moiety in CH₃CH₂CH₂NO₂(CH₃CH₂CH₂NO₂ → CH₃CH=CH₂ + HONO) needs to overcome lower energy barrier than that of the rate-determining step (one of H atom on the α-CH₂ and γ-CH₃ abstracted of reaction) of the other hydrogen abstraction reactions. Therefore, we predict that the corresponding alkenes and HONO are the main products in the hydrogen abstraction reaction of nitroparaffin. Besides, the channel of the CH₃CH₂CHO + HNO formations (CH₃CH₂C(α)H₂NO₂ → CH₃CH₂C(α)H₂ONO → CH₃CH₂CHO + HNO), occurring through the H atom of C(α) abstracted by the N atom of NO₂ moiety after the isomerization reaction from CH₃CH₂CH₂NO₂ to CH₃CH₂CH₂ONO, is favorable in the isomerization secondary reactions. Rate constants and branching ratios are estimated by means of the conventional transition state theory with zero curvature tunneling over the temperature range of 400–1500 K. The calculation shows that the overall rate constant in the temperature of 400–1500 K is mainly dependent on the competitive channels of formations of CH₃CH=CH₂ + HONO and \({\text{CH}}_{3} {\text{CH}}_{2} {\text{CH}}_{2}^{\cdot} +\,^{\cdot}{\text{NO}}_{2}\) The three-parameter expression for the total rate constant is fitted to be k _total = 1.74 × 10^?13 T ^8.20exp(17038.7/T) (s^?1) between 400 and 1500 K.     

Synthesis,characterization, antimicrobial activity and ultrastructure of the affected bacteria of new quinoline compounds

The reaction on 8-hydroxy quinoline-7-aldehyde azo compounds (HL _n ) (where n = 1–5) with 4-amino-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one to obtain HL _n (where n = 6–10) have been characterized by means of TLC, melting point and spectral data, such as IR, ¹H NMR, mass spectra and thermal studies. The X-ray diffraction patterns of two starting materials 8-hydroxy quinoline-7-aldehyde (start 1), 4-amino-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (start 2) and the ligands (HL_5,10) are investigated in powder form. All the ligands have been screened for their antimicrobial activity against four local bacterial species, two Gram-positive bacteria (Bacillus cereus and Staphylococcus aureus) and two Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae) as well as against four local fungi; Aspergillus niger, Alternaria alternata, Penicillium italicum and Fusarium oxysporium. The results show that the azo ligands (HL _n ) (where n = 1–5) have no antimicrobial activity against bacteria and fungi while most azomethine ligands (HL _n ) (where n = 6–10) are good antibacterial agents against E. coli and K. pneumoniae as well as antifungal agents against P. italicum and A. alternata. The results were compared to standard substances (start 1) and (start 2). Among the azomethine ligands, HL₁₀ was the most effective against the most microorganisms tested. The size of clear zone was ordered as p-(OCH₃ < CH₃ < H < Cl < NO₂) as expected from Hammett’s constant (σ ^R ). Also, the ultrastructure study of the affected bacteria confirmed that HL₈ is good antibacterial agent against E. coli and S. aureus.     

Synthesis and catalytic activity of monobridged bis(cyclopentadienyl)rhenium carbonyl complexes

Thermal treatment of three monobridged biscyclopentadienes (C₅H₅)R(C₅H₅) [R = C(CH₃)₂ (1), C(CH₂)₅ (2), Si(CH₃)₂ (3)] with Re₂(CO)₁₀ in refluxing mesitylene gave the corresponding complexes [(η ⁵-C₅H₄)₂R][Re(CO)₃]₂ [R = C(CH₃)₂ (4), C(C₅H₁₀) (5), Si(CH₃)₂ (6)], which were separated by chromatography, and characterized by elemental analysis, IR, and ¹H NMR spectroscopy. The molecular structures of complexes 5 and 6 were characterized by X-ray crystal diffraction analysis and show that both are monobridged bis(cyclopentadienyl)rhenium carbonyl complexes in which the molecule consists of two [(η ⁵-C₅H₄)Re(CO)₃] moieties linked by a single bridge, in which each of the two Re(CO)₃ units is coordinated to the cyclopentadienyl ring in an η ⁵ mode. All three of these monobridged bis(cyclopentadienyl)rhenium carbonyl complexes have good catalytic activities in Friedel–Crafts alkylation reactions.     

Structure and thermal reactivity of Zn(II) salts of isocinchomeronic acid (2,5-pyridinedicarboxylic acid)

The synthesis, an improved refined crystal and molecular structure re-determination, and the thermal decomposition behavior of two Zn(II) derivatives of isocinchomeronic acid (2,5-pyridinedicarboxylic acid or H₂2,5-pydc) are presented. [Zn(2,5-pydc)(H₂O)₃Zn(2,5-pydc)(H₂O)₂]₂ (1) crystallizes in the triclinic P-1 space group with a = 7.106(2), b = 11.450(2), c = 11.869(1) Å, α = 107.29(1), β = 104.08(1), γ = 90.32(2)°, and Z = 2. [Zn(2,5-pydc)(H₂O)₂] · H₂O (2) is orthorhombic (P2₁2₁2₁ space group), with a = 7.342(1), b = 9.430(1), c = 13.834(2) Å, and Z = 4. The structures were refined to agreement R ₁-factors of 0.0315 (1) and 0.0336 (2). Complex (1) is arranged as molecular Zn₄(2,5-pydc)₄(H₂O)₁₀ tetramers, the cages of which define channels that remain unblocked by anions. Compound (2) is polymeric with Zn(2,5-pydc)(H₂O)₂ and Zn(2,5-pydc)(H₂O)₃ units linked through bridging ligands. Both compounds were synthesized under mild conditions in aqueous media, without need to resort to hydrothermal media. Changing the pH from 4.51 to 5.75 suffices to direct the chemical processes toward the orthorhombic compound rather than to the triclinic one.     

Crystal structure of dimethylgold(III) 8-hydroxyquinolinate and 8-mercaptoquinolinate

A crystal-chemical study of dimethylgold(III) complexes with 8-hydroxyquinoline (CH₃)₂Au(OR) and 8-mercaptoquinoline (CH₃)₂Au(SR) (R = C₉H₆N) was performed. Crystal data for (CH₃)₂Au(OR): a = 8.7133(17) Å, b = 27.875(6) Å, c = 8.6688(17) Å, β = 102.76(3)°, Z = 8, ρ(calc) = 2.401 g/cm³, space group P2₁/c, R = 0.0909; for (CH₃)₂Au(SR): a = 3.5401(7) Å, b = 15.689(3) Å, c = 19.910(4) Å, β = 99.81(3)°, Z = 4, ρ(calc) = 2.361 g/cm³, space group P2₁/c, R = 0.0712. Both structures are molecular and involve neutral (CH₃)₂Au(L) molecules, L = C₉H₆NO or C₉H₆NS. In the structures, the molecules are arranged in stacks joined by van der Waals interactions. The average Au…Au intrastack distances are 3.57 Å and 4.34 Å for (CH₃)₂Au(OR) and 3.5 Å for (CH₃)₂Au(SR).