Three New Metal(II) Complexes with Unusual 2D Hydrogen Bond Network Based on <Emphasis Type="Italic">N</Emphasis>-methylimidazole

Three new metal(II) complexes based on N-methylimidazole, [ML₆]·(SH)₂·(H₂O)_2, (M = Ni(II) (1), Co(II) (2), Cu(II) (3), L=N-methylimidazole), have been synthesized and characterized. The single crystal X-ray structural analyses show that complexes 1, 2, and 3 have isomorphous structures and crystallize in monoclinic system with space group P2₁/c. The complexes containing isolated SH^? anions, which may come from the thermochemical sulfate reduction, are located in the gap with lattice water molecules and provide multiple intermolecular hydrogen bonds to form 2D layers. Topology analyses show a 2D hydrogen bond network, which can be regarded as an unprecedented trinodal (3,4,6)-connected topology with Schläfli symbol (3.4.5³.6)₂(3.4.5)₂(3²;5⁴;6⁴;8²;9³). Cyclic voltammetry and UV–vis spectra were studied.     

Syntheses and Characterization of Three Coordination Polymers of Zinc(II) and Cadmium(II) with Dicarboxylates and Bis(thiabendazole) Ligands

Three d ¹⁰ coordination polymers formulated as [Zn(L1)₂(mip)] _n (1), [Zn(L1)(2,6-ndc)] _n (2) and [Cd(L2)_0.5(bpdc)] _n (3) (L1 = 1,1′-(1,3-propanediyl)bis(thiabendazole), L2 = 1,1′-(1,6-hexanediyl)bis(thiabendazole), H₂mip = 5-methylisophthalic acid, 2,6-H₂ndc = 2,6-naphthalenedicarboxylic acid, H₂bpdc = 4,4′-biphenyldicarboxylic acid) were hydrothermally synthesized. Complexes 1–3 were characterized by elemental analysis, IR spectroscopy, X-ray powder diffraction analysis, and single crystal X-ray diffraction. Complexes 1 and 2 present different chain structures, both of them are extended into 2D supramolecular architectures via C–H···O hydrogen bonds, while 3 is a three-fold interpenetrating three-dimensional framework with binodal 4,4-connected mog topology. The thermal stability, UV–visible spectroscopy and luminescence properties of complexes 1–3 were also examined. Furthermore, complex 3 exhibits relatively positive catalytic activity towards the degradation of methyl orange in a Fenton-like process.     

Synthesis,Structures, and Catalytic Properties of Two Zinc(II) Coordination Polymers Constructed from Polycarboxylate and Bis(Benzimidazole) Ligands

Two Zn(II) coordination polymers, formulated as {[Zn(L1)_0.5(btc)_0.5(H₂O)]·H₂O} _n (1) and {[Zn(L2)(1,4-ndc)]·2H₂O} _n (2) [L1 = 1,4-bis(2-methylbenzimidazole-1-ylmethyl)benzene, L2 = 1,4-bis(2-methylbenzimidazole)butane, H₄btc = butane-1,2,3,4-tetracarboxylic acid, 1,4-H₂ndc = 1,4-naphthalenedicarboxylic acid] have been synthesized and structurally characterized by single crystal X-ray diffraction. Complex 1 features a 3D (3,4)-connected network with the topology of fsh-3,4-P2₁/c. Complex 2 is a 2D (4,4) grid with sql topology and further extends into a 3D supramolecular framework by π–π stacking interactions. In addition, the thermal stability, fluorescence, and catalytic properties of two complexes for degrading methyl orange dye in a Fenton-like process were investigated.     

Second-Order NLO Active Heterotrimetallic Schiff Base Metallopolymer

The new ionic heterotrimetallic unsymmetrically-substituted Schiff base complex [Ni{(η ⁵-Cp)Fe(η ⁵-C₅H₄)-C(=O)CH=C(4-HO-C₆H₄)NCH₂CH₂N=CH-(2-O-(η ⁶-C₆H₄)Ru(η ⁵-Cp*)}][PF₆] (3; Cp = C₅H₅ and Cp* = C₅(CH₃)₅) was prepared in 86% yield by a one-pot procedure by mixing equimolar amounts of 4-hydroxyphenyl functionalized ferrocenylenaminone 1, the organometallic aldehyde [(η ⁵-Cp*)Ru(η ⁶-2-HO-C₆H₄CHO)][PF₆] (2) and nickel(II) acetate tetrahydrate in refluxing ethanol for 2 h. Its corresponding side-chain metallopolymer 4 was synthesized by reacting the organometallic-inorganic hybrid 3 with polyacrylic acid (DP = 25) in DMF at 110 °C for 48 h with an equimolar quantity of N,N′-dicyclohexylcarbodiimide and a catalytic amount of 4-dimethylaminopyridine. The new complex 3 was characterized by FT-IR and multidimensional NMR spectroscopy, elemental analysis and mass spectrometry. Single crystal X-ray diffraction analysis of 3 showed that the ferrocenyl and [(η ⁵-Cp*)Ru]⁺ units exhibit an anti-conformation and are almost coplanar with the unsymmetrical Schiff base complex fragment, while the 4-HO-C₆H₄ plane is almost perpendicular. The four-coordinate Ni^II metal ion adopts a square planar geometry, with two nitrogen and two oxygen donor atoms that are mutually trans. Size-Exclusion Chromatography established that metallopolymer 4 is formed of approximately three pendant ionic trimetallic units, while Differential Scanning Calorimetry and Thermal Gravimetric Analysis indicated that 3 and 4 are thermally stable with decomposition temperatures that exceed or border to 250 °C. Harmonic Light Scattering measurements at 1.91 µm incident wavelength showed that compounds 3 and 4 exhibit rather high second-order nonlinear responses, with hyperpolarizability β _1.91 values strongly increasing on passing from the monomeric unit 3 to its metallopolymeric counterpart 4.     

Syntheses and Structural Characterization of Co(II) Coordination Polymers Supported by Bis(<Emphasis Type="Italic">N</Emphasis>-benzimidazolyl)methane and Bis(<Emphasis Type="Italic">N</Emphasis>-imidazolyl)methane

[Co₂(L¹)₂(NCS)₄]·4MeOH 1, [Co(L²)₂(H₂O)₂](Sal)₂·4H₂O (Sal = salicylate) 2 were obtained from self-assembly of the cobalt salts with bis(N-benzimidazolyl)methane (L¹), and bis(N-benzimidazolyl)methane (L²), and their structures were characterized by IR and X-ray diffraction analysis. Complex 1 exhibits a two-dimensional grid structure, whereas complex 2 is a coordination polymer having a one-dimensional linear chain structure. The grid in 1 lies parallel to the crystallographic ab plane and exhibits intra-grid M–M separations of 10.508 × 10.508 Å. Hydrogen bonds hold the cationic chains in 2 together leading to a three-dimensional network structure.     

(4<Emphasis Type="Italic">Z</Emphasis>,15<Emphasis Type="Italic">Z</Emphasis>)-Octadecadienoic Acid Inhibits Glycogen Synthase Kinase-3β and Glucose Production in H4IIE Cells

Many uncommon non-methylene-interrupted fatty acids (NMI FA) are present in limpet gonads, but their biological properties remain unknown. To investigate new biological effects of naturally occurring NMI FA in eukaryotic cells, the biological activities of structurally analogous (4Z,15Z)-octadecadienoic acid (1), (9Z,20Z)-tricosadienoic acid (2), and (12Z,23Z)-hexacosadienoic acid (3) were examined by using a yeast-based drug-screening system using the Ca²⁺-sensitive mutant strain, Saccharomyces cerevisiae (zds1Δ erg3Δ pdr1Δ pdr3Δ). Among 1–3, 1 showed restored growth activity at a dose of 80 µg/disc in the mutant yeast strain. This phenotype suggests that 1 suppresses Ca²⁺-signaling of the mutant yeast through inhibition of glycogen synthase kinase-3β (GSK-3β) or calcineurin pathways or both. From this result, the inhibitory activity of 1–3 against GSK-3β was further determined. 1–3 showed potent inhibitory activity against GSK-3β with IC₅₀ values ranging from 8.7 to 21.9 µM. Inhibition of GSK-3β reduces gene expression of the gluconeogenic key enzymes in liver, so we analyzed glucose production in rat hepatoma H4IIE cells to assess GSK-3β inhibitory activity of 1–3. Acid 1 inhibited glucose production at 25 µM in H4IIE cells. Our results would open up new possibilities for an anti-diabetic effect of 1 and might provide important insights into understanding the biological properties of naturally occurring NMI FA.     

Synthesis,Characterization and Surface Properties of Amidosulfobetaine Surfactants Bearing Odd-Number Hydrophobic Tail

Three amidosulfobetaine surfactants were synthesized namely: 3-(N-pentadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2a); 3-(N-heptadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2b), and 3-(N-nonadecanamidopropyl-N,N-dimethyl ammonium) propanesulfonate (2c). These surfactants were prepared by direct amidation of commercially available fatty acids with 3-(dimethylamino)-1-propylamine and subsequent reaction with 1,3-propanesultone to obtain quaternary ammonium salts. The synthesized surfactants were characterized by IR, NMR and mass spectrometry. Thermogravimetric analysis (TGA) results showed that the synthesized surfactants have excellent thermal stability with no major thermal degradation below 300 °C. The critical micelle concentration (CMC) values of the surfactants 2a and 2b were found to be 2.2 × 10^?4 and 1.04 × 10^?4 mol/L, and the corresponding surface tension (γ_CMC) values were 33.14 and 34.89 mN m^?1, respectively. The surfactants exhibit excellent surface properties, which are comparable with conventional surfactants. The intrinsic viscosity of surfactant (2b) was studied at various temperatures and concentrations of multi-component brine solution. The plot of natural logarithm of relative viscosity versus surfactant concentration obtained from Higiro et al. model best fit the surfactant behavior. Due to good salt resistance, excellent surface properties and thermal stability, the synthesized surfactant has potential to be used in various oil field applications such as enhanced oil recovery, fracturing, acid diversion, and well stimulation.     

One Pot Synthesis and Properties of Cationic Surfactants: <Emphasis Type="Italic">n</Emphasis>-Alkyl-3-Methylpyridinium Bromide

Three new amphiphilic compounds i.e., n-decyl-3-methylpyridinium bromide (a), n-dodecyl-3-methylpyridinium bromide (b), and n-tetradecyl-3-methylpyridinium bromide (c), have been synthesized by condensation reaction and characterized by NMR (¹H, ¹³C) and FTIR spectroscopic techniques. The micellization behavior of the compounds has been studied in ethanol employing conductometry and UV/visible spectroscopy. The critical micellization concentration (CMC) values for compound a, b and c was found to be 0.31, 0.29 and 0.27 m mol L^?1, respectively. Effect of temperature on the CMC was checked in the range of 298-318 K. The thermodynamic parameters such as ΔG, ΔH and ΔS of the micellization process of these surfactants were computed. The negative values of ΔG and positive values of ΔH indicated the spontaneous and endothermic nature of the micellization process. Antimicrobial activities of these amphiphiles showed significant activity against different bacterial strains.     

2-Methoxylated FA Display Unusual Antibacterial Activity Towards Clinical Isolates of Methicillin-Resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> (CIMRSA) and <Emphasis Type="Italic">Escherichia coli</Emphasis>

The naturally occurring (6Z)-(±)-2-methoxy-6-hexadecenoic acid (1) and (6Z)-(±)-2-methoxy-6-octadecenoic acid (2) were synthesized in 7–8 steps with 38 and 13% overall yields, respectively, by using an acetylide coupling approach, which made it possible to obtain a 100% cis-stereochemistry for the double bonds. In a similar fashion, the acetylenic analogs (±)-2-methoxy-6-hexadecynoic acid (3) and (±)-2-methoxy-6-octadecynoic acid (4) were also synthesized in 6–7 steps with 48 and 16% overall yields, respectively. The antibacterial activity of acids 1–4 was determined against clinical isolates of methicillin-resistant Staphylococcus aureus (ClMRSA) and Escherichia coli. Among the series of compounds, acid 4 was the most active bactericide towards CIMRSA displaying IC_50s (half maximal inhibitory concentrations) between 17 and 37 μg/mL, in sharp contrast to the 6-octadecynoic acid, which was not bactericidal at all. On the other hand, acids 1 and 3 were the only acids that displayed antibacterial activity towards E. coli, but 1 stood out as the best candidate with an IC₅₀ of 21 μg/mL. The critical micelle concentrations (CMCs) of acids 1–4 were also determined. The C18 acids 2 and 4 displayed a five-fold lower CMC (15–20 μg/mL) than the C16 analogs 1 and 3 (70–100 μg/mL), indicating that 4 exerts its antibacterial activity in a micellar state. None of the studied acids were inhibitory towards S. aureus DNA gyrase discounting this type of enzyme inhibition as a possible antibacterial mechanism. It was concluded that the combination of α-methoxylation and C-6 unsaturation increases the bactericidal activity of the C16 and C18 FA towards the studied bacterial strains. Acids 1 and 4 stand out as viable candidates to be used against E. coli and CIMRSA, respectively.     

Silicon-containing halogenated poly(amides) derived from diacids with aminoacidic and imidic moieties in the side chain: synthesis,characterization, optical studies and thermal properties

New halogenated silicon-containing poly(amides) (PAs) derived from diacids and an aromatic diamine containing an Si atom were obtained according to the Yamazaki procedure. The diacids contain a preformed halogenated imide ring, another amide group and an aminoacidic residue. The diacids and the PAs were characterized by IR and ¹H, ¹³C and ²⁹Si NMR spectroscopy, elemental analysis and, when corresponding, optical rotation. For those PAs containing F atoms in the imide ring, we also observed the signals corresponding to the coupling of the C–F atoms in the ¹³C MNR spectra. The results are in agreement with the proposed structures. Also, PAs without amino acid residues were synthesized according to the same procedure. PAs were soluble in aprotic polar solvents and some of them in m-cresol and THF, due to the inclusion in the structure of meta-substitution aromatic rings, flexible aminoacidic residue and polar C–Si bonds. The η _inh values were low, indicating the presence of oligomeric species of low molecular weight. The T _g values did not show a clear tendency about the influence of the nature of the amino acid residue, but when the influence of the halogen atoms was analyzed, it was possible to observe a decrease in the T _g values, due to the higher chain separation, and consequently the lower interactions between them. The thermal decomposition temperatures were determined at 10 % of weight loss, showing in general good values between 300 and 367 °C, and not showing a relationship between the values and the structure of the side groups. The transparency was studied observing moderate values at 400 nm, but showing 80 % of transparency between 500 and 550 nm, which was attributed to the higher aromatic content of these PAs. All PAs showed flame retardancy due to the presence of the halogen atoms.     

Synthesis,Characterization, Crystal Structures and Thermal and Fluorescence Studies of Dinuclear and Polymeric Silver(I) Complexes of 5,5-Diethylbarbiturate with 2,5-Dimethylpyrazine and Piperazine Involving Ag–Ag Interactions

Two silver(I) complexes, [Ag(dmpyz)₂][Ag(barb)₂] (1) and {[Ag(ppz)][Ag(barb)₂]·H₂O} _n (2) (barb = 5,5-diethylbarbiturate, dmpyz = 2,5-dimethylpyrazine and ppz = piperazine), have been synthesized and characterized by elemental analyses, IR, thermal analysis (TG-DTA) and single-crystal X-ray diffraction. Complex 1 consists of [Ag(dmpyz)₂]⁺ and [Ag(barb)₂]^? ions in which the silver(I) ions are linearly coordinated by two dmpyz or two barb ligands. These two ions are connected by strong Ag–Ag interactions (Ag–Ag = 2.896 (1) Å). Complex 2 is a 1D coordination polymer in which the silver(I) ions are bridged by the ppz ligands in a linear fashion, leading to a zigzag chain of [Ag(ppz)] _n ⁺ , which interacts with the [Ag(barb)₂]^? units by Ag–Ag interactions of 3.183 (1) Å. The 1D chains are further assembled to form 3D networks by strong N–H···O and OW–H···O hydrogen bonds. IR spectra and TG-DTA data are in agreement with the crystal structures. The fluorescent properties of 1 were also evaluated.     

Homo and Dinuclear Heteroleptic Zn,Cd &amp; Pb Complexes Derived from FcCOOH and DTBbpy Ligands: Structural,Luminescence and Electrochemical Studies

Mononuclear [Zn(FcCOO)(DTBbpy)₂]ClO4.(H₂O)₃ (1) and dinuclear [Cd₂(FcCOO)₂(DTBbpy)₄]ClO₄·(H₂O) (2), [Pb₂(FcCOO)₂(DTBbpy)₂(H₂O)₂]·ClO₄ (3) (FcCOO = ferrocenecarboxylate, DTBbpy = 4,4′-di-tert-butyl-bipyridyl) metal complexes have been synthesized and characterized by single crystal X-ray diffraction. It reveals that the Zn(II), Cd(II) and Pb(II) metal complexes have different coordination geometries [Zn and Pb = distorted octahedral, Cd = distorted pentagonal bipyramidal]. The compound 3 shows the hemidirected mode of coordination in the geometrical system due to the inert pair effect of the lone pair of an electron on Pb(II) metal atom. The molecules are further forms 2D & 3D framework structure via intermolecular hydrogen bonding. All the three compounds exhibit strong fluorescence emission bands in the liquid state at ambient temperature, of which the emission maxima show red-shifted and the solution-state electrochemistry of compounds 1–3 in CH₃CN has been investigated.     

Supramolecular Polymers and Chiral Phosphine Oxides by Oxidation of Gold(I) Complexes

The chiral diphosphine ligand R,R-cyclo-C₆H₁₀-trans-1,2-{NHC(=O)C₆H₄-2-PPh₂}₂, 1, forms complexes with gold(I) of formula [Au(1)]Cl, 2, and [(ClAu)₂(µ-1)], 3, in which the diphosphine acts as a trans-chelate and bridging ligand, respectively. Oxidation of these gold(I) complexes leads to dissociation and oxidation of the diphosphine ligand to form the corresponding diphosphine dioxide R,R-cyclo-C₆H₁₀-1,2-{NHC(=O)C₆H₄-2-P(=O)Ph₂}₂, which has been crystallized in its protonated form and as complexes with Na⁺ and Fe²⁺, with [AuBr₂]^? or [AuBr₄]^? anions. Some of these compounds form supramolecular polymers by intermolecular hydrogen bonding.     

Thermogravimetric characteristics of <Emphasis Type="Italic">α</Emphasis>-cellulose and decomposition kinetics in a micro-tubing reactor

The pyrolysis characteristics and kinetics of α-cellulose were investigated using thermogravimetric analyzer (TGA) and micro tubing reactor, respectively. Most of the α-cellulose decomposed between 250 and 400 °C at heating rate of 5–20 °C/min. The apparent activation energy was observed in the range of 263.02 kJ mol^?1 to 306.21 kJ mol^?1 at the conversion of 10-80%. The kinetic parameters were determined by nonlinear least-squares regression of the experimental data, assuming first-order kinetics. It was found from the kinetic rate constants that the predominant reaction pathway was A(α-cellulose) to B(bio-oil) rather than A(α-cellulose) to C(gas; C₁-C₄) and/or to B(bio-oil) to C(gas; C₁-C₄) at temperatures of 340-360 °C.     

Syntheses,Structures, and Catalytic Properties of Five Isomorphous 3D Transition Metal Complexes Derived from Formate

Five isomorphous 3D complexes of formates, namely, {Cu(HCOO)₂·4H₂O} _n (1), {Co(HCOO)₂·2H₂O} _n (2), {Mn(HCOO)₂·2H₂O} _n (3), {Co(HCOO)₂·DMF·H₂O} _n (4), and {Mn₂(HCOO)₆·0.5[HN(CH₃)₂]} _n (5), were synthesized and characterized by microanalysis. The catalytic activities of these complexes for the oxidation of phenol by H₂O₂ to catechol (CAT) and hydroquinone (HQ) were investigated. Complex 1 showed the best performance by exhibiting a high conversion rate of 68.02% and a high selectivity for CAT with a maximum CAT/HQ ratio of 2.74.     

Catalyst Screening through Quantum Chemical Calculations and Microkinetic Modeling: Hydrolysis of Carbon Dioxide

Quantum chemical calculations are emerging as an effective way to screen catalysts for particular applications. In this contribution, we demonstrate the power of density functional theory to study CO₂ hydrolysisby six carbonic anhydrase mimics, evaluating thermodynamic and kinetic parameters at the mechanistic level. A microkinetic model was then built based on the kinetics and thermodynamics calculated from first principles. The intrinsic reaction rate constant was calculated from the results of the microkinetic model and compared with experimental data. Overall, the rate constants were in good agreement with experimental values, except for zinc-tri and complex b, which were overestimated. This was ascribed to their ineffective complexation with Zn²⁺. How the reaction rate constants vary with time was also investigated. From 0 to 12 ms, the rate constants of complexes a and d decreased to 50 and 67% of their initial values, respectively; the rate constants of complexes b and f2 were almost invariant with time; the rate constant of complex f1 showed an unusual double sigmoidal shape. The pK_a values of these six carbonic anhydrase mimics as well as three additional mimics were calculated. A correlation between pK_a values and the binding free energy of OH-was obtained by fitting data from five zinc(II) aza-macrocyclic complexes. The reaction rate constants were found to increase linearly with the pK_a value, indicating CO₂ adsorption is the rate-limiting step.     

Synthesis and characterization of polyimides from 4,4′-(3-(<Emphasis Type="Italic">tert</Emphasis>-butyl)-4-aminophenoxy)diphenyl ether

A novel diamine 4,4′-(3-(tert-butyl)-4-aminophenoxy)diphenyl ether (4) was synthesized from 2-tert-butylaniline and 4,4′-oxydiphenol through iodination, acetyl protection, coupling reaction and deacetylation protection. Then some polyimides (PIs) were obtained by one-pot polycondensation of diamne 4 with several commercial aromatic dianhydrides respectively. They all exhibit enhanced solubility in organic solvents (such as NMP, DMF, THF and CHCl₃ etc.) at room temperature. Their number-average molecular weights are in the range of (2.1–3.7)?×?10⁴ g/mol with PDI from 2.25 to 2.74 by GPC. They can form transparent, tough and flexible films by solution-casting. The light transparency of them is higher than 90% in the visible light range from 400 nm to 760 nm and the cut-off wavelengths of UV–vis absorption are below 370 nm. They also display the outstanding thermal stability with the 5% weight loss temperature from 525 °C to 529 °C in nitrogen atmosphere. The glass transition temperatures (T _g s) are higher than 264 °C by DSC. XRD results demonstrate that these PIs are amorphous polymers with the lower water absorption (<0.66%). In summary, the incorporation of tert-butyl groups and multiple phenoxy units into the rigid PI backbones can endow them excellent solubility and transparency with relatively high T _g s.     

Four Flexible Bis(Thiabendazole)-Based Cd(II) Coordination Polymers with Various Aromatic Carboxylates: Syntheses,Structures and Properties

Four Cd(II) coordination polymers (CPs) including [Cd(btbb)_0.5(L1)] _n (1), [Cd(btbb)(L2)·(H₂O)_1.5] _n (2), [Cd(btbb)(L3)] _n (3), and [Cd(btbb)(HL4)] _n (4) (btbb?=?1,4-bis(thiabendazole)butane, H₂L1?=?5-hydroxyisophthalic acid, H₂L2?=?4,4′-biphenyldicarboxylic acid, H₂L3?=?tetrabromoterephthalic acid, H₃L4?=?5-nitro-1,2,3-benzenetricarboxylic acid) were prepared under hydrothermal conditions based on flexible bis(thiabendazole) ligand and different co-carboxylates. Their structures have been determined by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra, X-ray powder diffraction, and thermogravimetric analyses. CP 1 exhibits a 3D 2-nodal (3,4)-connected framework with the 3,4T10 topology. CP 2 and 3 feature typical hcb layer structure, and 3 is further combined into a 3D supramolecular architecture through C–H?O hydrogen bonds. CP 4 possesses an infinite chain and further extended into 2D supramolecular network by O–H?O hydrogen-bonding interactions. The effects of the aromatic polycarboxylate co-ligands on the CPs framework have been discussed and the catalytic activities of CPs 1–4 for degradation of methyl orange in Fenton-like process are also investigated.     

Assembly,Fluorescent and Adsorption Properties of Two Cadmium(II)/Cobalt(II) Coordination Complexes Functionalized by the Flexible Bis(Pyridyl)-bis(Amide) Ligand

A new cadmium(II) and a new cobalt(II) coordination complexes [Cd₅(BTB)₄(HL)₂]·2H₂O (1) and [Co(HBTB)(L)]·2H₂O (2) [H₃BTB?=?1,3,5-tri(4-carboxylphenyl)benzene, L?=?N,N′-bis(3-pyridyl)octandiamide] were prepared under the solvothermal conditions by the assembly of cadmium(II)/cobalt(II) chloride, the flexible bis(pyridyl)-bis(amide) ligand L and the aromatic tricarboxylic acid H₃BTB. The structures of complexes 1–2 have been characterized by X-ray single crystal diffraction analyses, infrared spectroscopy (IR), powder X-ray diffraction (PXRD) and thermogravimetric (TG) analyses. Complex 1 is a 3D metal–organic network with the penta-nodal (2,4,4,5,6)-connected {4·6³·8·10}₂{4²·6⁵·8³}₂{4³·6³}₂{4⁶·8⁹}{6}₂ topology constructed from the 3D [Cd₅(BTB)₄]_n^2n? coordiantion framework and the protonated HL ligands. Complex 2 displays a binodal (4,4)-connected {6⁴·8·10}{6} topological 2D layered architecture based on the 1D [Co(HBTB)]_n chains and the 1D [CoL]_n chains, which are further linked by hydrogen bonding interactions to form a 3D supramolecular network. Moreover, the fluorescent properties of the cadmium(II) complex and the dyes adsorption performances of complexes 1–2 have been studied.     

Inhibition of mild steel corrosion in hydrochloric acid medium by polymeric inhibitors containing residues of essential amino acid methionine

Ethyl ester hydrochloride of amino acid l-methionine 1 was converted to cationic monomers N,N-diallyl methionine ethyl ester hydrochloride 2 and hydrochloride salt of N,N-diallylmethionine 3. Cationic monomers 2 and 3 underwent alternate copolymerization with SO₂ in dimethyl sulfoxide to give terpolymers 4 and 5, respectively, both having?≈?1:1 ratio of sulfide and sulfoxide motifs owing to O transfer from dimethyl sulfoxide to the S. The sulfide groups in 5 have been oxidized with H₂O₂ to give polymer sulfoxide 6. In the presence of a small concentration of 35.2 µM (~?11?±?1 ppm) of each of the polymers 4, 5 and 6, the inhibition efficiency against mild steel corrosion in 1.0 M HCl at 60 °C was determined to be 90.8, 98.7 and 93.0%, respectively. The inhibition efficiency obtained from gravimetric weight loss was corroborated by the findings of potentiodynamic polarization and electrochemical impedance spectroscopy methods. Adsorption of polymer compounds onto the mild steel surface followed a mixture of chemisorption and physisorption processes and obeyed Langmuir, Temkin and Freundlich adsorption isotherms. The X-ray photoelectron spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy techniques further confirmed that the synthesized compounds formed a protective film onto the metal surface and prove it against further corrosion attack.