X-ray Structural Investigation Research Articles

Lanthanide-Based Probes for Imaging Detection of Enzyme Activities by NIR Luminescence, T1- and ParaCEST MRI.

Applying a single molecular probe to monitor enzymatic activities in multiple, complementary imaging modalities is highly desirable to ascertain detection and to avoid the complexity associated with the use of agents of different chemical entities. We demonstrate here the versatility of lanthanide (Ln3+) complexes with respect to their optical and magnetic properties and their potential for enzymatic detection in NIR luminescence, CEST and T1 MR imaging, controlled by the nature of the Ln3+ ion, while using a unique chelator. Based on X-ray structural, photophysical, and solution NMR investigations of a family of Ln3+ DO3A-pyridine model complexes, we could rationalize the luminescence (Eu3+, Yb3+), CEST (Yb3+) and relaxation (Gd3+) properties and their variations between carbamate and amine derivatives. This allowed the design of probes which undergo enzyme-mediated changes detectable in NIR luminescence, CEST and T1-weighted MRI, respectively governed by variations in their absorption energy, in their exchanging proton pool and in their size, thus relaxation efficacy. We demonstrate that these properties can be exploited for the visualization of β-galactosidase activity in phantom samples by different imaging modalities: NIR optical imaging, CEST and T1-weighted MRI.

Cytotoxicity and Apoptosis-Induction in MCF-7 Cells for New Pd(II) Complex Based on s-Triazine Ligand: Synthesis, Single Crystal X-ray Diffraction Analysis and Structural Investigations

The synthesis and X-ray structure analysis of the new [PdLCl2]*0.5 CH2Cl2 complex where L is hydrazono-s-triazine di-morpholine derivative, were presented. In the neutral inner sphere of this complex, the organic ligand L is acting as a NN-bidentate chelate via the pyridine and hydrazone N-atoms. The coordination configuration of the Pd(II) is completed by two chloride ions at cis-positions. The tetra-coordinated Pd(II) showed a distorted square planar geometry. The outer sphere comprised half methylene chloride molecule per [PdLCl2] as crystal solvent. The crystal stability is dominated by a number of weak C-H…N, C-H…Cl, and C-H…O non-covalent interactions. Based on Hirshfeld analysis, the H…H, N…H, H…Cl, O…H, Pd…C, and Cl…C intermolecular interactions contributed by 45.2, 9.3, 21.5, 5.8, 2.3, and 3.4%, respectively. DFT studies revealed closed shell characters for the Pd-N and Pd-Cl coordinate bonds. The net charge of Pd is also predicted to be 0.311 e and the amount of electron density transferred from the ligand groups is 1.689 e. The Pd(II) complex exhibited potent cytotoxic activity against MCF-7, HepG2, and A549 cells with IC50 values of 1.18, 4.74, and 5.22 μg/mL, compared to cisplatin with IC50 values of 4.1, 9.7, and 12.3 μg/mL, respectively. Additionally, it exhibited poor cytotoxicity against WISH cells with much higher IC50 values (IC50 = 37.2 μg/mL). Investigating apoptosis-induction, the Pd(II) complex induced apoptotic cell death by an 11-fold change in MCF-7 cells arresting the cell phase at the G0–G1 phase. Accordingly, Pd(II) complex can be developed as a promising anti-breast cancer agent.

Crystal structures of biocompatible Mg-, Zn-, and Co-whitlockites synthesized via one-step hydrothermal reaction

Abstract Large-scale single crystals of Ca9Mg(PO4)6(PO3OH), Ca9Zn(PO4)6(PO3OH), and Ca9Co(PO4)6(PO3OH) were synthesized using hydrothermal technique, and turned out to be similar to natural bone whitlockite. The hexagonal single crystals about 1 mm with high-quality were obtained with this method for the first time. The crystals were of sufficiently good quality for the precision X-ray structural investigation. The compounds crystallize in usual for this structural type trigonal space group R3c. Presence of hydrogen atom in the structure was confirmed by means of infra-red (IR) spectroscopy, differential scanning calorimetry (DSC) and differential thermogravimetry (DTG) methods. Based on the analysis of the local bond valence sum (BVS), a conclusion on the localization of H atoms was made. The formation of O–H groups and hydrogen bonds H⋯O in vicinity of PO4 tetrahedra was shown and similar to bone whitlockite. This research provides new data on possibility of using hydrothermal technique for obtaining doped bone whitlockites. Hydrogen-containing doped whitlockites can combine bioactive properties and improve biocompatibility due to similarity to natural bond. New structural data are useful for finding the ways to better biocompatibility of whitlockite-based materials.

Superior dielectric and varistor properties of ZnO or SnO2 diffused calcium copper titanate ceramics

Sub-micrometer-sized (0.33 μm) polycrystalline powders of calcium copper titanate (CCTO) were synthesized via the solgel method. Compacted calcined powders were sintered at 900 °C/2h to obtain porous (<80% density) pellets. Subsequently, ZnO or SnO2 pastes (∼10 μm grain size) were smeared on either side of the pellets and sintered at 1100 °C/15 h, which yielded dense (>95% density) ceramics. X-ray structural investigations revealed the presence of ZnO or SnO2 traces in the bulk of the CCTO ceramics. Scanning electron microscopy and energy dispersive spectroscopic studies confirmed the diffusion and the segregation of these oxides at the grain boundaries. The dielectric and varistor properties of the ZnO or SnO2 diffused samples were found to be superior to that of pristine CCTO ceramics. For instance, the dielectric constant (ɛ′) of ZnO diffused ceramics exhibited a value as high as 2.4 × 104 (1 kHz, at room temperature) and a dielectric loss (D) of 0.059. Similarly, SnO2 diffused ceramics exhibited a dielectric constant of 2.7 × 104 (1 kHz, at room temperature) associated with a dielectric loss of 0.047. The figure of merit of varistor performance, i.e., nonlinear coefficient (α = 10.6), of the SnO2 diffused sample is significantly higher than that of ZnO diffused (α = 7.4) and pristine CCTO (α = 4.5) ceramics. The dielectric data obtained for both the pristine and ZnO or SnO2 diffused ceramics were rationalized by invoking Cole–Cole analysis. The thermal activation energy was estimated from the temperature-dependent dielectric data besides current (I)–voltage (V) characteristics. Equivalent circuit modeling of the Nyquist plots demonstrated that the inclusion of ZnO and SnO2 layers in CCTO ceramics remarkably improved the grain boundary resistance (Rgb) by 5-fold and 20-fold, respectively, which resulted in making CCTO a better dielectric. This methodology of fabricating ceramics via interfacial engineering could pave the way for obtaining superior CCTO ceramics associated with exotic functional properties.

Spectroscopic and X-ray structural investigations of the active calcium preparation

Structural studies of calcium citrate obtained by IR irradiation of calcium carbonate and citric acid in various ratios by spectroscopic and X-ray structural analysis has been carried out. It is shown that in the obtained samples of calcium carbonate there are polymorphic states in the form of aragonite, vaterite, calcite, as well as ikaite and in calcium citrate complex calcium compounds with different coordination numbers are observed.

Synthesis, structure, thermal and magnetic properties of new tetranuclear copper(II) complex supported by multidentate ligand and glutarate functionality

A new tetranuclear Cu(II) complex, [Cu(H2O)4][Cu4(cpdp)2(glut)]Cl2·6H2O (1) was successfully constructed by utilization of carboxylate-based multidentate ligand N,N'-bis[2-carboxybenzomethyl]-N,N'-bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol (H3cpdp), in combination with glutarate (glut) and Cu(II) ions, and characterized systematically. Originally, the symmetrical flexible ligand cpdp3− is capable to bind two Cu(II) ions, leaving behind accessible binding sites for further coordination of exogenous glutarate anion which facilitates the assembly of two ligand-bound Cu(II) pairs. In MeOH/H2O, the reaction of CuCl2·2H2O with H3cpdp and sodium glutarate in the presence of NaOH results in the formation of 1. Complex 1 was characterized by different analytical techniques, including single crystal X-ray structure investigation. Analysis of single crystal X-ray structure shows that 1 is a self-assembled tetranuclear copper complex in which two dinuclear [Cu2(cpdp)]+ species are exclusively bridged by one glutarate functionality through μ4:η1:η1:η1:η1 manner, acting as a coligand. Thermoanalytical methods (TGA/DTA) were used to examine the thermal stability and it was observed that 1 is stable up to ∼190°C. Variable temperature (2-300 K) magnetic susceptibility studies show the weak antiferromagnetic interactions among the copper centers with the value of magnetic exchange coupling constant (J) of -0.5 cm−1.

One pot synthesis of two potent Ag(I) complexes with quinoxaline ligand, X-ray structure, Hirshfeld analysis, antimicrobial, and antitumor investigations

In one pot, the self-assembly of AgNO3 and 2-chloroquinoxaline (2Cl-quinox) in water–ethanol mixture afforded two novel crystalline Ag(I) complexes. The major product is the polymeric complex [Ag(2Cl-quinox)(NO3)]n; (1), while the minor product (2) comprises two molecules which are the monomeric [Ag(2Cl-quinox)2(NO3)]; (2a) and polymeric [Ag(2Cl-quinox)(NO3)]n; (2b) complexes. The single crystal X-ray structure revealed that 1 and 2b are made up of two-dimensional infinite sheets. In contrast, 2a is a monomeric complex which has a highly distorted tetrahedral geometry around Ag(I) center. In all cases, the 2Cl-quinox molecule acts as a terminal monodentate ligand. Complexes 1 and 2b have similar molecular structures and also have almost similar crystal packing. Using Hirshfeld surface analysis, the O…H hydrogen bonds and π–π stacking interactions contributed significantly to the molecular packing. Both complexes have broad-spectrum action towards multi drug-resistance bacteria. The most effective function of 2 is against Proteus morganii, with a MIC value of 8 μg/mL. Complex 2 (IC50 = 5.93 ± 0.52 μg/mL) has remarkably greater cytotoxic effect against lung carcinoma (A-549) than cis-platin (IC50 = 7.5 ± 0.69 μg/mL) and AgNO3 (IC50 = 14.7 ± 0.53 μg/mL). The higher Ag-content in 2 could be the main reason for its higher cytotoxicity than 1.

Lanthanide Luminescence and Thermochromic Emission from Soft-Atom Donor Dichalcogenoimidodiphosphinate Ligands

The luminescence properties of two divalent europium complexes of the type Eu[N(SPPh2)2]2(THF)2 (1) and Eu[N(SePPh2)2]2(THF)2 (2) were investigated. The first complex, Eu[N(SPPh2)2]2(THF)2 (1), was found to be isomorphous with the reported structure of complex 2 and exhibited room temperature luminescence with thermochromic emission upon cooling. We found the complex Eu[N(SePPh2)2]2(THF)2 (2) was also thermochromic but the emission intensity was sensitive to temperature. Both room temperature and low temperature (100 K) single crystal X-ray structural investigation of 1 and 2 indicate geometric distortions of the metal coordination, which may be important for understanding the thermochromic behavior of these complexes. The trivalent europium complex Eu[N(SPPh2)2]3 (3) with the same ligand as 1 was also structurally characterized as a function of temperature and exhibited temperature-dependent luminescence intensity, with no observable emission at room temperature but intense luminescence at 77 K. Variable temperature Raman spectroscopy was used to determine the onset temperature of luminescence of Eu[N(SPPh2)2]3 (3), where the 615 nm (5D0 → 7F2 transition) peak was quenched above 130 K. The UV-visible diffuse reflectance of 3 provides evidence of an LMCT band, supporting a mechanism of thermally activated LMCT quenching of Eu(III) emitting states. A series of ten isomorphous, trivalent lanthanide complexes of type Ln[N(SPPh2)2]3 (Ln = Eu (3) Pr (4), Nd (5), Sm (6), Gd (7), Tb (8)) and Ln[N(SePPh2)2]3 (Ln = Pr (9), Nd (10, structure was previously reported), Sm (11), and Gd (12) for Q = Se) were also synthesized and structurally characterized. These complexes for Ln = Pr, Nd, Sm, and Tb exhibited room temperature luminescence. This study provides examples of temperature-dependent luminescence of both Eu2+ and Eu3+, and the use of soft-atom donor ligands to sensitize lanthanide luminescence in a range of trivalent lanthanides, spanning near IR and visible emitters.

A new Febuxostat-Telmisartan Drug-Drug Cocrystal for Gout-Hypertension Combination Therapy

Drug–drug cocrystalllization is a novel mechanism for effective pharmacological combination therapy. In this work, we have demonstrated the preparation of a drug-drug cocrystal of a hypertension drug (Telmisartan; TEL) with a hyperuricemia drug (Febuxostat; FEB) in 1:1 molar ratio using a solvent evaporation method for the first time. Generally, a multi-component system may yield either a eutectic, salt, and/or a cocrystal. This study adopted a methodical orthogonal framework to analyze the final solid form. A single crystal X-ray structural investigation revealed the formation of a heterosynthon with carboxylic and benzimidazole groups of FEB and TEL, respectively, in the triclinic P-1 space group. ΔpKa of the heterosynthon is ∼1.5, hence, based on the empirical rules, a salt-cocrystal continuum is hypothesized. Further, attenuated total reflectance Fourier transform infrared (ATR-FTIR), and Raman spectroscopy were employed to corroborate the hydrogen bond formation in the heterosynthon (-N---H-O-), which confirmed the propensity for cocrystal formation. An accelerated stability study and an in vitro biorelevant dissolution study of the cocrystal were performed, which demonstrated that it is physiochemically stable, but it resulted in a slower dissolution rate when compared with plain drugs.

Whither Second-Sphere Coordination?

Whither Second-Sphere Coordination?

Effect Of vacuum plasma on structure and function of fibers of Ichnocarpus frutescens

The present investigation is based on high strength and high water resistant cellulosic biodegradable fiber of Ichnocarpus frutescens (IF). IF is known as the longest plant fiber. A survey of literature does not reveal any substantial information on spectroscopic data and chemical composition of IF fiber. In this report ,X-ray structural investigation, FT-IR study and biomass compositional analysis of both untreated IF fiber and plasma-exposed IF fiber are presented. The IF fiber was extracted from the stem of the plant by treating with 4% dil. NaOH solution followed by modifying it using vacuum nitrogen cold plasma exposure. The mechanism of molecular interaction between solid IF fiber and coldplasma are discussed in detail along with the description of the cold plasma exposure experimental setup. The structure of cellulose-Iß present in IF fiber was revealed from the XRD pattern and found to be monoclinic in nature with lattice parameter a = 7.784 Å, b = 8.201 Å, c = 10.380 Å, α = γ = 90°, β = 95.80°. The change in FWHM, crystallite size, fiber orientation and % crystallinity of the plasma-exposed IF fiber indicates molecular interactions of the solid fiber with plasma molecules. The FT-IR data reveal the presence of NH2 and NO3 groups in the plasma-exposed IF fiber. The investigation of biomass compositional analysis of IF fiber reports 35.87 ± 0.65% cellulose, 17.77 ± 0.47% hemicellulose, 2.47 ± 0.04% acid-soluble lignin(ASL) and 17.10 ± 0.66% acid-insoluble lignin(AIL).

π-Stacking interactions in new arylsulphonylamine-substituted derivatives of imidazo[2,1-b]thiazol

• "Closed" type of sulfonamide molecular systems is characterized by the presence of intramolecular π-stacking. • The electron density distribution functions obtained theoretically (QTAIM) coincide with those experimentally measured by the XRD method. • The energy of π-π-interaction is in the range of 0.54–0.88 kcal/mol. The peculiarities of a spatial structure of new representatives of arylsulfonylamino-substituted derivatives of imidazo[2,1- b ][1,3]thiazoles were studied by X-ray diffraction analysis. All presented molecules are "closed" systems due to efficient intramolecular π-stacking and compact arrangement of fragments. The features of weak intramolecular stacking interactions were revealed based on X-ray structural investigation and QTAIM analysis. A theoretical study of the stereo electronic structure based on the electron density distribution in the XRD experiment was carried out. The energies of π-stacking interaction were estimated by theoretical methods based on the value of the potential energy density at the bond critical point (3, -1) type.

In vitro anticancer activity of 4(3H)-quinazolinone derived Schiff base and its Cu(II), Zn(II) and Cd(II) complexes: Preparation, X-ray structural, spectral characterization and theoretical investigations

This work reports the synthesis of a novel quinolin-4(3H)-one based Schiff base ligand 3-[(E)-(2,5-dimethoxyphenyl)methylidene]amino-2-methylquinazolin-4(3H)-one (DMPAQ) and its coordination complexes of the type [M(DMPAQ)(phen)]X (1a-1c), where M = Cu(II), Zn(II) and Cd(II) ions, respectively, phen = 1,10-phenanthroline. All the synthesized compounds were characterized using UV–Visible, elemental analysis, FT-IR, 1H NMR, Mass spectroscopy and TGA techniques. The triclinic structure of the DMPAQ is determined by employing single crystal X-ray crystallographic analysis. The characterization results suggested that the ligand, DMPAQ is bidentate and coordinate to the metal center through the lactum oxygen and the azomethine nitrogen. The synthesized DMPAQ ligand and complexes (1a-1c) were screened for their in vitro anticancer activity against the human breast adenocarcinoma cell line, MCF-7. The complexes 1a and 1b displayed significant anticancer activity against MCF-7 cells even at lower GI50 value (GI50 = 0.016 µM) than the standard drug doxorubicin (GI50 = 0.018 µM). Further, we have performed computational DFT studies on the chemical reactivity of the ligand and the three complexes by means of Conceptual Density Functional Theory (CDFT) through the “Koopmans in DFT” (KID) approximation to support the experimentally obtained results.

Structure-based design approach to rational site-directed mutagenesis of β-lactoglobulin

Recombinant proteins play an important role in medicine and have diverse applications in industrial biotechnology. Lactoglobulin has shown great potential for use in targeted drug delivery and body fluid detoxification because of its ability to bind a variety of molecules. In order to modify the biophysical properties of β-lactoglobulin, a series of single-site mutations were designed using a structure-based approach. A 3-dimensional structure alignment of homologous molecules led to the design of nine β-lactoglobulin variants with mutations introduced in the binding pocket region. Seven stable and correctly folded variants (L39Y, I56F, L58F, V92F, V92Y, F105L, M107L) were thoroughly characterized by fluorescence, circular dichroism, isothermal titration calorimetry, size-exclusion chromatography, and X-ray structural investigations. The effects of the amino acid substitutions were observed as slight rearrangements of the binding pocket geometry, but they also significantly influenced the global properties of the protein. Most of the mutations increased the thermal/chemical stability without altering the dimerization constant or pH-dependent conformational behavior. The crystal structures reveal that the I56F and F105L mutations reduced the depth of the binding pocket, which is advantageous since it can reduce the affinity to endogenous fatty acids. The F105L mutant created a unique binding mode for a fatty acid, supporting the idea that lactoglobulin can be altered to bind unique molecules. Selected variants possessing a unique combination of their individual properties can be used for further, more advanced mutagenesis, and the presented results support further research using β-lactoglobulin as a therapeutic delivery agent or a blood detoxifying molecule.

Synthesis, characterization, structures and in vitro antitumor activity of platinum(II) complexes bearing adeninato or methylated adeninato ligands

Reactions of the carbonato platinum(II) complexes [Pt(CO3)(PPh3)2]·CH2Cl2 (1) and [Pt(CO3)(dppe)] (dppe = 1,2-bis(diphenylphosphino)ethane; 2) with adenine (3a) and its N6-methylated derivatives (N6-MeAde, 3b; N6,N6-Me2Ade, 3c) resulted under splitting off carbon dioxide in formation of bis(adeninato)platinum complexes [Pt(N6,N6-RR’Ade–H-κN9)2(PPh3)2] (4a–4c) and [Pt(N6,N6-RR’Ade–H-κN9)2(dppe)] (5a–5c) R/R’ = H, Me, respectively. Analogous reactions with adenines methylated at the N9 or N3 position (9-MeAde, 3d; N6,9-Me2Ade, 3e; 3-MeAde, 3f) gave cationic complexes which could be isolated as hexafluorophosphate salts: [Pt(9-MeAde–H-κ2N6,N7)(PPh3)2][PF6] (6a), [Pt(N6,9-Me2Ade–H-κ2N6,N7)(dppe)][PF6] (6b), and [Pt(3-MeAde–H-κ2N6,N7)(PPh3)2][PF6] (7). The deprotonation of the less acidic exocyclic N6HR (R = H, Me) group and the chelating κ2N6,N7 coordination in complexes 6/7 could unambiguously clarified by 1H,15N HMBC NMR spectroscopy and additionally by DFT calculations. All complexes were fully characterized especially by NMR (1H, 13C, 31P) and single-crystal X-ray structural investigations (4b∙2i-PrOH, 4c, 5a∙MeOH, and 5c∙1.5 MeOH). In vitro antitumoral activity was investigated against five tumor cell lines (A549 lung, A2780 ovarian, DLD-1 colon, FaDu head and neck, and SW1736 anaplastic thyroid). The most active compound 4b was found more active than cisplatin against cisplatin resistant DLD-1 (IC50 = 4.1 ± 0.5 µM) and SW1736 cell lines (IC50 = 1.5 ± 0.4 µM).

Выращивание объемных кристаллов оксида галлия из расплава методом Чохральского в кислородсодержащей атмосфере

This paper reports on successful experiments in growing beta-gallium oxide crystals using the Czochralski method. The influence of growth atmosphere composition on crystal quality of the material was studied. It is shown that to obtain high quality optically transparent crystals it is necessary to have about 5 vol.% oxygen in the growth atmosphere. X-ray structural analysis and investigation of optical transmission spectra of grown crystals are carried out.

Heavy alkaline earth π-complexes with doubly-reduced polycyclic aromatic hydrocarbons of variable sizes

Barium (II) π-complexes with two planar polycyclic aromatic hydrocarbons (PAHs), anthracene and fluoranthene, have been prepared by direct alkaline earth metal reduction reactions in THF in the presence of 1,2-diiodoethane (DIE), used as an activator. The products have been crystallographically characterized to reveal their mixed-ligand composition, {[Ba(I)(THF)3]22+[C14H10]2–} (1) and {[Ba(I)(THF)3]22+[C16H10]2–} (2). A similar strontium (II) product, {[Sr(I)(THF)4]22+[C10H8]2-} (3), has been synthesized using potassium-naphthalenide ligand-exchange reaction starting with SrI2. In 1 and 2, Ba(II) ions are π-complexed by doubly-reduced PAHs with the planarity of the dianions being preserved upon reduction and metal binding. In contrast, the naphthalene dianion in 3 adopts a non-planar geometry with a dihedral angle of 15.2°. The M–Ccentroid distances of 2.754 (6) Å and 2.755 (14) Å in 1 and 2, respectively, are longer than that in 3 (2.600 (2) Å). The coordination environment of alkaline earth metal ions is completed by iodide ligands and coordinated THF molecules. The X-ray structural investigation confirmed the formation of the iodide-bridged 1D polymers in barium products, {[Ba (μ-I) (THF)3]22+[C14H10]2–}∞ (1) and {[Ba (μ-I) (THF)3]22+[C16H10]2–}∞ (2) vs. a discrete strontium complex with terminal iodide ligands in 3.

Heterospin bis(dioxolene)manganese complexes with iminopyridine ligands. The effect of ancillary ligand on the charge distribution in the complex

Three novel bis-dioxolene manganese complexes (dioxolene = the reduced forms of 3,6-di-tert-butyl-o-quinone) with iminopyridine ligands having various substituents (cyclohexyl, 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) and phenyl) at the imine nitrogen atom have been synthesized. The X-ray structural investigation has shown that the obtained compounds are characterized by different charge distribution. In spite of this complexes demonstrate close magnetic behavior. Compounds based on phenyl- and TEMPO-substituted iminopyridines containing anion-radical form of dioxolene are characterized by strong antiferromagnetic exchange interaction between unpaired electrons on the manganese ions and o-semiquinonato ligands.

Mixed-ligand coordination compounds based on the rigid 4,4′-bis(1-imidazolyl)biphenyl and pyridinedicarboxylate ligands

The mixed-ligand binuclear complexes [Co2(BIBP)(2,6-PDC)2(H2O)4] (1), [Ni2(BIBP)(2,6-PDC)2(H2O)4] (2), and the coordination polymers 1D-{[Zn(BIBP)(2,6-PDC)]·4.5H2O}n (3), 2D-[Ni2(BIBP)(2,5-PDC)2(H2O)4]n (4), and 3D-{[Ni2(BIBP)3(2,3-PDC)2]·3.75H2O}n (5) were synthesized in good yields, characterized by IR, thermogravimetry and single X-ray diffraction method (BIBP = 4,4′-bis(1-imidazolyl)biphenyl, 2,6-PDC = 2,6-pyridinedicarboxylate, 2,3-PDC = 2,3-pyridinedicarboxylate, 2,5-PDC = 2,5-pyridinedicarboxylate). Compounds 1 and 2 are binuclear complexes, compound 3 is a 1D polymer, 4 has a 2D laminated structure, and 5 represent a 3D framework. A common motif in the structures, independent of their dimensionality is the bridging action of the neutral BIBP ligand between two metal ions and a metal chelating coordination of the dianionic PDC ligand through the pyridine nitrogen atom and the carboxylate group in 2-position. The comparative single crystal X-ray structure investigations reveal the fine-tuning influence of the carboxylic group positions in the pyridinedicarboxylate (PDC) ligands and the metal nature on the final structure topology and dimensionality. Compounds 1 and 2 are isostructural and represent Co(II) and Ni(II) isomorphs, where the metal ions coordinate two water molecules and the 2,6-PDC ligand in ONO chelate mode, while the bidentate BIBP ligand link the metal ions into a dinuclear complex. In 3 the 2,6-PDC ligand coordinates to the zinc atom in the same ONO chelate mode and two bridging BIBP ligands give a coordination number of five and extend the structure to a 1D polymer with an enantiopure triple-stranded helix motif in a case of spontaneous resolution in the chiral tetragonal space group P4322. In 4 the 2,5-PDC ligand realises its chelate-bridging function and together with the bridging BIBP ligand form 2D layers with the Ni(II) atoms with hcb (honeycomb or 6,3) topology. In 5 the chelate-bridging 2,3-PDC and BIBP ligands form (4,4)-layers which are interlinked by additional BIBP pillars to a 3D network with two-fold interpenetration of symmetry-related networks.

Ethylethanolammonium 4-nitrobenzoate

The demand for corrosion inhibitors with low toxicity has increased in the last years in a wide range of sectors. Our study presents the synthesis, X-ray structure, thermal and kinetic investigation of ethylethanolammonium 4-nitrobenzoate (EEA4NB) as corrosion inhibitor for iron in 3% NaCl solution. Proton transfer and hydrogen bonding in the organic salt were elucidated and confirmed by infrared spectroscopy and single-crystal X-ray diffraction. Simultaneous TGA–DTA and heat flow analysis were used to study the thermal and kinetic behavior of EEA4NB. The results provided useful information about thermal stability and thermal decomposition. The non-isothermal kinetic parameters were estimated by using three different kinetic methods. Electrochemical corrosion measurements show corrosion inhibitor efficiency of EEA4NB for iron in 3% NaCl solution higher than 92% and a decrease of corrosion current and corrosion rate as a result of adsorption of EEA4NB molecules at the metal/solution interface.