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The title compound 5-methyl-1,3- bis (3-nitrobenzyl)pyrimidine-2,4(1 H ,3 H )-dione was obtained by reaction of thymine with 3-nitrobenzylbromide in the presence of cesium carbonate. Characterization of the product was achieved by NMR spectroscopy and its stability was probed in basic condition using UV-Visible analysis. Furthermore, the molecular structure was confirmed by X-ray diffraction analysis. The compound crystallizes in orthorhombic Pna 21 space group with unit cell parameters a = 14.9594 (15) A, b = 25.711 (3) A, c = 4.5004 (4) A, V = 1731.0 (3) A 3 and Z = 4. The crystal packing of the title compound is stabilized by intermolecular hydrogen bond, π···π and C−H···π stacking interactions. The intermolecular interactions were furthermore analyzed through the mapping of different Hirshfeld surfaces. The two-dimensional fingerprint revealed that the most important contributions to these surfaces come from O···H (37.1%), H···H (24%) and H···C/C···H (22.6%) interactions. The interaction energies stabilizing the crystal packing were calculated and were presented graphically as framework energy diagrams. Finally, the energy-framework analysis reveals that π···π and C−H···π interactions energies are mainly dispersive and are the most important forces in the crystal.

The use of thermal evaporation processes, such as multieffect distillation (MED) and membrane distillation (MD), is presented as a very interesting option to regenerate salt solutions when a closed-loop system is considered in a salinity gradient power heat engine (SGP-HE). It is due to the possible increase in the operating temperature of the evaporation processes by the use of working fluids preventing ions from scaling formation. This chapter shows the potential of both thermal evaporation processes in terms of thermal energy consumption to regenerate the salt solutions used in an SGP-HE. Several case studies are presented for MED and MD, using three different salt solutions: sodium chloride (NaCl), lithium chloride (LiCl), and potassium acetate (KAc) as working fluids. Results prove the high potential of both thermal evaporation processes to regenerate these salts, achieving minimum values of specific thermal energy consumption of 21.3 kWh/m3 in MED for concentrating a solution of NaCl from 1 to 5 M and 302 kWhth/m3 from 1.8 to 3.6 M for MD.

An efficient synthetic protocol was devised for the preparation of five cationic ruthenium-arene complexes bearing imidazol(in)ium-2-dithiocarboxylate ligands from the [RuCl2(p-cymene)]2 dimer and 2 equiv of an NHC·CS2 zwitterion. The reactions proceeded cleanly and swiftly in dichloromethane at room temperature to afford the expected [RuCl(p-cymene)(S2C·NHC)]Cl products in quantitative yields. When the [RuCl2(p-cymene)]2 dimer was reacted with only 1 equiv of a dithiolate betaine under the same experimental conditions, a set of five bimetallic compounds with the generic formula [RuCl(p-cymene)(S2C·NHC)][RuCl3(p-cymene)] was obtained in quantitative yields. These novel, dual anionic and cationic ruthenium-arene complexes were fully characterized by various analytical techniques. NMR titrations showed that the chelation of the dithiocarboxylate ligands to afford [RuCl(p-cymene)(S2C·NHC)]+ cations was quantitative and irreversible. Conversely, the formation of the [RuCl3(p-cymene)]- anion was limited by an equilibrium, and this species readily dissociated into Cl- anions and the [RuCl2(p-cymene)]2 dimer. The position of the equilibrium was strongly influenced by the nature of the solvent and was rather insensitive to the temperature. Two monometallic and two bimetallic complexes cocrystallized with water, and their molecular structures were solved by X-ray diffraction analysis. Crystallography revealed the existence of strong interactions between the azolium ring protons of the cationic complexes and neighboring donor groups from the anions or the solvent. The various compounds under investigation were highly soluble in water. They were all strongly cytotoxic against K562 cancer cells. Furthermore, with a selectivity index of 32.1, the [RuCl(p-cymene)(S2C·SIDip)]Cl complex remarkably targeted the erythroleukemic cells vs mouse splenocytes., info:eu-repo/semantics/published

The hydrolysis of 2-methyl-2 H -1,2,4-benzothiadiazine 1,1-dioxide (2) during crystallization under humidity (85 %) conditions, lead to N -(2-( N -methylsulfamoyl)phenyl)formamide as second step hydrolysis product, identified in the proposed degradation mechanism. Crystal of N -(2-( N -methylsulfamoyl)phenyl)formamide C 8 H 10 N 2 O 3 S (4), was obtained and characterized. The molecular structure determination was carried out with MoKα X-ray and data measured at 100 K. The compound 4 crystallizes in triclinic P 1 space group with unit cell parameters a = 4.8465(4) A, b = 8.1942(9) A, c = 11.8686(13) A, α = 77.080(4)°, β = 82.069(4)°, γ = 80.648(4)°, V = 450.76 (8) A 3 and Z = 2. The crystal structure is stabilized by intramolecular N-H···O and intermolecular C-H···O and N-H···O hydrogen bonds that extended as infinite 1D chain along [100]. Stabilization is also ensured by oxygen-π stacking interaction between the aromatic ring and oxygen of the sulfonamide group. The analysis of intermolecular interactions through the mapping of d norm and shape-index revel that the most significant contributions to the Hirshfeld surface 40.6 and 33.9% are from H···H and O···H contacts, respectively.

The title compound corresponds to an enaminone E isomer in the solid state. X-ray structure shows that this crystallizes in the orthorrombic system, with space group Pna21 with 2 independent molecules in the asymmetric unit in a non-centrosymmetric setting. The CNNC unit forms dihedral angles of 5.9(3)/2.1(3); 19.7(3)/17.6(3)° with the pyrrole and phenol rings for molecules A and B respectively. The main differences between both molecules is the dihedral torsion between rings, their mean planes form dihedral angles of 25.45(15) and 15.38(15)° for the molecules A and B. In the asymmetric unit, molecules are linked by two weak N – H···O hydrogen bonds with set graph-motif

The effect of the ligand and/or metal-related factors on the formation of tristhiosemicarbazone metallosupramolecular complexes has been studied in this work. The crystal structures of zinc(II) and lead(II) tristhiosemicarbazone mesocates and a hydrolyzed cadmium(II) helicate let us better rationalize some factors involved in the selective formation of helicates or mesocates.

In this paper, we report the design, synthesis and biochemical evaluation of 2-amino-3-(7-methoxybenzo[d][1,3]dioxol-5-yl)propanoic acid 9, a myristicin derivative, from cheap and available vanillin as starting material. Compound 9 is identified as a potential precursor of natural brasiliamide derivatives. All the products are fully characterized. The crystal structure of the intermediate diethyl 2-acetamido-2-((7-methoxybenzo[d][1,3]dioxol-5-yl)methyl)malonate 16, a precursor of this amino acid, is obtained and presented. The interactions stabilizing the crystal packing of 16 were deeply analyzed by considering first the supramolecular stacking and finally, by analyzing the contacts descriptors on the Hirshfeld surface, the molecular fingerprint and the intermolecular energy. Different biochemical properties of the desired amino acid 9 and its selected precursors are investigated. In DPPH test, 9 showed the best anti-radical activity (IC50 = 80.91 μM). The enzymatic, HRP-H2O2/L012, chemiluminescence assay reveals excellent inhibitory effect on the peroxidase activity and a good antioxidant activity of all the tested compounds with the best activity for 9 (IC50 = 0.36 μM). The anti-peroxidase activity observed for compound 9 was confirmed by molecular docking exploration that allows to identify interactions in the HRP-9 complex. Docking results showed that 9 interacts with catalytic and active site residues, especially with Arg38, His42, Ser73, Phe68 and Pro139. Moreover, the inhibition of ROS production by activated HL-60 cells was moderately obtained with compounds 9 and 13. The MTS cell viability test reveals that all tested compounds, except myristicin aldehyde 13, were not cytotoxic indicating that the observed inhibition of ROS production of activated HL-60 cells was not due to cells death. Finally, physicochemical and ADME-Tox predictions suggested that compound 9 could be considered as promising drug candidate.

In this work, novel 1,4-diacetyl-3,6-bis(phenylmethyl)-2,5-piperazinedione (2) is prepared exclusively as the (R,S)-stereoisomer evidenced and confirmed by X-ray diffraction analysis. In addition, spectroscopic (NMR, IR, Raman) analyses were used to characterize the new compound. 2 crystallizes in the Pbca orthorhombic space group, with a symmetry center located at the centroid of the diketopiperazine ring. The structure of 2 is compact with the two phenyl rings folded over and under the diketopiperazine ring, conferring thereby a unique S shape to the molecule. The crystal structure is stabilized by intramolecular interactions, whereas the crystal packing is stabilized by intermolecular H-bond and C−H···π interactions. The different intermolecular interactions were confirmed using Hirshfeld surface analysis and molecular fingerprint. Molecular 2D fingerprint that quantify the different interactions highlights that H···H (58.2%), H···O/O···H (24.8%) and C···H/H···C (14.2%) account for 97.2% of all contacts. The topology of the interaction energy in the crystal structure is obtained and described. The Cremer and Pople puckering parameters indicate that the diketopiperazine ring adopts a flattened chair conformation with Θ = 0.00 ° and Q = 0.2233 (11) A. Moreover, a computational investigation revealed that the optimized structure of 2 using DFT calculation shows excellent agreement with the experimental data. As potential pharmacological active molecule, the molecular docking on breast cancer resistance protein (BCRP) reveals that 2 could interacts with the binding domain residues Phe728, Tyr949, Ser975 and Val978 and could be consider as promising BCRP inhibitor.

The reaction of [RuCl2(p-cymene)]2 with potassium O-ethylxanthate and a set of nine representative Ph2P-X-PPh2 bidentate phosphines (dppm, dppe, dppp, dppb, dpppe, dppen, dppbz, dppf, and DPEphos) afforded monometallic [Ru(S2COEt)2(diphos)] chelates 1-9 in 62-96% yield. All the products were fully characterized by using various analytical techniques and their molecular structures were determined by X-ray crystallography. They featured a highly distorted octahedral geometry with a S-Ru-S bite angle close to 72° and P-Ru-P angles ranging between 73° and 103°. Bond lengths and IR stretching frequencies recorded for the anionic xanthate ligands strongly suggested a significant contribution of the EtO+[double bond, length as m-dash]CS22- resonance form. 1H NMR and XRD analyses showed that the methylene protons of the ethyl groups were diastereotopic due to a strong locking of their conformation by a neighboring phenyl ring. On cyclic voltammetry, quasi-reversible waves were observed for the Ru2+/Ru3+ redox couples with E1/2 values ranging between 0.65 and 0.80 V vs. Ag/AgCl. The activity of chelates 1-9 was probed in three catalytic processes, viz., the synthesis of vinyl esters from benzoic acid and 1-hexyne, the cyclopropanation of styrene with ethyl diazoacetate, and the atom transfer radical addition of carbon tetrachloride and methyl methacrylate. In the first case, 31P NMR analysis of the reaction mixtures showed that the starting complexes remained mostly unaltered despite the harsh thermal treatment that was applied to them. In the second case, monitoring the rate of nitrogen evolution revealed that all the catalysts under investigation behaved similarly and were rather slow initiators. In the third case, [Ru(S2COEt)2(dppm)] was singled out as a very active and selective catalyst already at 140 °C, whereas most of the other complexes resisted degradation up to 160 °C and were only moderately active. Altogether, these results were in line with the high stability displayed by [Ru(S2COEt)2(diphos)] chelates 1-9.

Nine representative [Ru(S2CNEt2)2(diphos)] complexes were prepared in almost quantitative yields (91–97%) from [RuCl2(p-cymene)]2, sodium diethyldithiocarbamate trihydrate, and a diphosphine (dppm, dppe, dppp, dppb, dpppe, dppen, dppbz, dppf, or DPEphos), using a novel, straightforward, one-pot procedure. The recourse to a monomodal microwave reactor was instrumental in reaching the thermodynamic equilibria favoring the targeted monometallic trichelates. All the products were fully characterized by using various analytical techniques and the molecular structures of seven of them were determined by X-ray crystallography. NMR, XRD, and IR spectroscopies evidenced a significant contribution of the thioureide resonance form Et2N+=CS22– to the electronic structure of the 1,1-dithiolate ligand. MS/MS spectrometry showed the formation of phosphine-free [Ru(S2CNEt2)2]+ cations in the gas phase, except when starting from [Ru(S2CNEt2)2(dppbz)]. The activity of the nine complexes was probed in three different catalytic processes, viz., the cyclopropanation of styrene with ethyl diazoacetate, the synthesis of vinyl esters from benzoic acid and 1-hexyne, and the atom transfer radical addition (ATRA) of carbon tetrachloride and methyl methacrylate. In the first two reactions, the saturated trichelates were poorly efficient. This was most likely due to their high stability, which prevented the formation of coordinatively unsaturated species. Contrastingly, with a turnover number of 2000 and an initial turnover frequency of 2080 h–1 for a 0.05 mol% catalyst loading, the [Ru(S2CNEt2)2(dppm)] complex emerged as a very robust, latent ATRA initiator, whose activity matched or outperformed those displayed by the most efficient ruthenium catalysts described so far.

We present in this study the synthesis and characterization of a new 3,3-dimethyl-substituted 1,2,4-benzothiadiazine 1,1-dioxide. 3,3-dimethyl-3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide 10, was obtained by reacting 2-aminobenzenesulfonamide with acetone. The molecular structures of the starting sulfonamide and the new benzothiadiazine were obtained by X-ray diffraction analysis and the interactions like hydrogen bonds stabilizing the crystal packing were discussed. The contacts are confirmed by non-covalent interaction analysis. Analyses of Hirshfeld surface mapped over di, de, dnorm and shape-index were further used to identify the intermolecular interactions. The fingerprint histogram allow to show that H···H (45.7%) and O···H (30.1%) contacts are the dominant interactions in the crystal packing of 10. The effects of the molecular environment were accessed by analyzing the electron density isosurface and the 3D-topology of energy frameworks. The prediction of physicochemical properties suggested that 10 could be considered as a lead-like drug. Therefore, molecular docking study was performed on the α-amino-3‑hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) and suggested that 10 could interact with the allosteric site located on the ligand binding domain of AMPAR and could be a positive allosteric modulator. Docking results show that 10 can bind in a symmetrical way in the GluA2 ligand binding domain with two molecules at the dimer interface. The results also demonstrated that the presence of two methyl groups at the 3-position of the thiadiazine ring induced rotation of 10 in the binding site leading to close contacts with Pro494, Ser497, Ser729 and Ser754.

Enyne-substituted benzoisothiazole derivatives have been synthesised under one-pot, operationally simple conditions using 2-iodo-N-(trimethylsilylethynyl)benzenesulfonamides and terminal alkynes as starting materials and a palladium–copper-based catalytic system. The structure of these heterocycles has been demonstrated by NMR spectroscopy and confirmed by X-ray crystallographic analysis. A plausible reaction mechanism has been proposed.

A screen-printed carbon electrode (SPCE) modified with copper (II) 1-(3-bromobenzyl)-5-methyl-1H-1,2,3-triazole-4-carboxylate [Cu(bmtc)2(H2O)] and was used as an electrochemical sensor of hydrogen peroxide. The material was characterised by crystal X-ray and cyclic voltammetry. The electrochemical behaviour of the modified electrode [Cu(bmtc)2(H2O)]/SPCE was evaluated against bare SPCE for the reduction of 1.0 mM H2O2 in phosphate buffer (pH = 7.0), where the modified electrode responded ~ −0.55 V even though the SPCE did not present response. On the other hand, analytical parameters such as reproducibility (2.7%), repeatability (2.6%), LOD (5.8 × 10−7 mol L−1), selectivity (physiological substances) and stability were evaluated.

The N-methylimidazolium hexachloroantimonate salt Cl6Sb·C4H7N2 (MIMSb), was prepared and fully characterized. In 1H NMR spectrum, the N-H proton shifted to downfield because of the presence of SbCl6− and appears as a triplet at 13.19 ppm. Characterization with IR spectroscopy shows strong absorption band at around 699 cm−1 which is attributed to Sb−Cl stretching. Furthermore, UV–visible analysis at high concentrations in DMSO suggested that MIMSb interacts with DMSO leading to an absorption in visible region at λmax of 426 nm. Electrochemical characterization using cyclic voltammetry demonstrates three redox processes with reduction peaks at 0.69, −0.13 and −0.50 V. Finally, molecular structure of the product was determined by X-ray diffraction analysis. The crystal structure determination was carried out with Mo-Kα X-ray and data measured at 100 K. The title compound crystallizes in monoclinic P21/c space group with unit cell parameters a = 7.1131 (5) A, b = 12.4436 (9) A, c = 14.1658 (11) A, V = 1241.86 (16) A3 and Z = 4. The crystal packing is stabilized by H---Cl interaction. The analysis of intermolecular interactions was realized through the mapping of contact descriptors dnorm, shape-index and the fingerprint reveling that the most significant contribution to the Hirshfeld surface (69.4%) is from H---Cl contacts. Finally, the catalytic activity of MIMSb was probed in the cyclopropanation of styrene with ethyl diazoacetate.

We herein describe the straightforward synthesis of a stable pyridyl(4-methoxyphenyl)iodonium salt and its [18F] radiolabeling within a one-step, fully automated and cGMP compliant radiosynthesis of [18F]UCB-H ([18F]7), a PET tracer for the imaging of synaptic vesicle glycoprotein 2A (SV2A). Over the course of 1 year, 50 automated productions provided 34 ± 2% of injectable [18F]7 from up to 285 GBq (7.7 Ci) of [18F]fluoride in 50 min (uncorrected radiochemical yield, specific activity of 815 ± 185 GBq/μmol). The successful implementation of our synthetic strategy within routine, high-activity, and cGMP productions attests to its practicality and reliability for the production of large doses of [18F]7. In addition to enabling efficient and cost-effective clinical research on a range of neurological pathologies through the imaging of SV2A, this work further demonstrates the real value of iodonium salts for the cGMP 18F-PET tracer manufacturing industry, and their ability to fulfill practical and regulatory ...

A 72 m3/d pilot low-temperature multi-effect distillation plant located at the Plataforma Solar de Almeria has been experimentally characterized at steady state to study the influence of the variation in certain parameters that control the process (the hot water inlet temperature as external thermal energy source and the last effect vapor temperature) on the distillate production, the thermal consumption, and the thermal energy efficiency of the plant. Results allowed characterizing the increase in the water production and the thermal consumption with the increase in the hot water inlet temperature and with the decrease in the last effect vapor temperature. The performance ratio reached its maximum when the last effect vapor temperature ranged from 25 to 35°C, since the temperature difference between effects was lower. The preliminary characterization of this plant provides useful experimental information for design criteria and for the analysis of control strategies of other large-scale MED plant...

© 2016 Balaban Desalination Publications. All rights reserved. Novel desalination approaches are required to provide both drinking and agricultural water as there is ever increasing stress upon precious freshwater resources. It was our hypothesis that a modified Forward Osmosis (FO) process had the potential for production of irrigation water comprising of appropriate concentrations of fertilizers from a seawater feed. Four agents, KNO3, Na2SO4, CaNO3, and MgCl2, plus 35 g/L seawater were used as the draw and feed solutions of the FO process. Net Driving Pressure in the FO process was manipulated either by increasing the concentration of draw solution (FO process) or by increasing feed pressure (Pressure Assisted FO (PAFO) process). A series of nanofiltration (NF) and reverse osmosis (RO) membranes were used for the regeneration of draw solution. The results suggested that a PAFO process was more energy efficient than simple FO, provided the energy relating to the brine flow from the NF/RO membrane for pressurizing the feed solution of PAFO process was used. Furthermore, this study suggested using a mixture of a primary draw solution, MgCl2, and a secondary draw solution, KNO3, for NO3 supply into the irrigation water was preferable. As such, MgCl2 provided the driving force for fresh water extraction while KNO3 was the source of fertilizer in the irrigation water. Results showed that water quality provided by application of a MgCl2 + KNO3 draw solution was better than that from KNO3 or Ca(NO3)2. The concentrations of NO3 and SO4 in irrigation water were within recommended levels when the diluted draw solution was regenerated by a dual stage low-pressure RO process.

Forward Osmosis (FO) has been proposed as an alternative method for seawater desalination, wherein Reverse Osmosis (RO) membrane technology is used for regeneration of the draw solution. Previous studies have indicated that a standalone Reverse Osmosis unit is more energy efficient than a Forward Osmosis-Reverse Osmosis system and as such it was recommended that an FO-RO system was best employed only for the desalination of high salinity seawaters. This study examined FO-RO applicability in more detail by examining the impact of seawater salinity, impact of an Energy Recovery Device (ERD), and the effect of membrane fouling. For comparison purposes, the performance of the FO process was improved to minimize the impact of concentration polarization and optimize the concentration of draw solution. Model calculations revealed that FO-RO was more energy efficient than RO when no Energy Recovery Device was employed. However, results showed there was no significant difference in the power consumption between the FO-RO system and the RO unit at high seawater salinities, particularly when a high efficiency ERD was installed. Moreover, the FO-RO system required more membrane area than conventional a RO unit which may further compromise the FO-RO desalination cost.

Five complexes with the generic formula [ReBr(CO)3(κ2-S,S′-S2C·NHC)] were obtained by reacting [ReBr(CO)5] with a set of representative imidazol(in)ium-2-dithiocarboxylate zwitterions. These ligands are the adducts of N-heterocyclic carbenes (NHCs) and carbon disulfide. The monometallic Re(I) compounds were further coupled with Na[Re(CO)5] to afford bimetallic Re(0) species. Depending on the experimental conditions, either octacarbonyl dimers [Re2(CO)8(μ2–κ1-S,κ1-S′-S2C·NHC)] or hexacarbonyl clusters [Re2(CO)6(κ2-S,S′-κ3-S,C,S′-S2C·NHC)] were isolated. All the products were fully characterized using various analytical techniques. Single crystal XRD analysis helped establish with certainty the various binding modes exhibited by the NHC·CS2 ligands. With bite angles ranging from ca. 104 to 130°, these zwitterions displayed a remarkable flexibility, which also permitted significant twists of the thiometallated rings to preserve a staggered arrangement of the carbonyl groups in the bimetallic systems. Monitoring the chemical shift of the CS2− moiety by 13C NMR spectroscopy was most useful to detect its change of hapticity upon decarbonylation of the octacarbonyl compounds into hexacarbonyl derivatives. IR spectroscopy was another very convenient tool to identify the type of complex formed in a reaction, based on the pattern of its carbonyl vibration bands. Advanced mass spectrometry techniques showed that all the compounds underwent partial or total decarbonylation in the gas phase with no concomitant fragmentation of the bimetallic assemblies into monometallic ions.

A dinuclear Pb(ii) mesocate has been prepared with an unprecedented four-coordinated kernel in which the Pb(ii) lone pair is stereochemically active. This is the first time that this effect has been observed in a supramolecular Pb(ii) helicate or meso-helicate.

Three novel trans-halogeno(4-acetoxyphenyl)bis(triphenylphosphine)palladium(II) complexes (XPd(4-AcOC6H4)(PPh3)2, with X = I (3), Br (4) and Cl (5)) were synthesized and characterized by spectroscopic techniques and by X-ray diffraction analysis. The SEM images of the particles obtained after synthesis and microwave treatment show uniform morphology and particle size lower than 1 μm for the iodo-palladium complex (3). The electrochemical performance of the palladium-based anode materials was evaluated by cyclic voltammetry and galvanostatic cycling. The results show that the nature of the halogen ligand (X = I, Br and Cl) has a high impact on the reaction mechanism during the first discharge and cycling performance. Thus, the three materials IPd(4-AcOC6H4)(PPh3)2 (3), BrPd(4-AcOC6H4)(PPh3)2 (4) and ClPd(4-AcOC6H4)(PPh3)2 (5) deliver high initial irreversible capacities of 1089, 444 and 684 mAh g−1, respectively, during the first discharge at 20 mA g−1 at a voltage window between 0.01 and 3.0 V. In addition, the iodo-palladium-based anode material shows the highest specific capacity and a high capacity retention after 200 cycles at a current density of 50 mA g−1 with an average discharge capacity of about 170 mAh g−1.

A dual stage pressure retarded osmosis (PRO) process was investigated for power generation using different types of membranes. Polyamide (PA) and cellulose triacetate (CTA) membranes were used in the first and second stage of the PRO process to improve the process performance due to the high water permeability of PA membranes. A comparison between dual stage PA–CTA and CTA–CTA membrane systems were carried out using seawater as a draw solution, while fresh water and wastewater effluent were the feed solution in the first and second stage of the process. The impact of draw solution flow rate on the process performance was evaluated. The performance of first and second stage of the PRO process increased by 11.5 and 28.6%, respectively, when the draw solution flow rate increased by a factor of 2.5. In return, there was a negligible increase in the total specific power consumption of the PRO process. In general, power consumption of the dual stage PRO process was as low as 0.3 kWh/m3. Furthermore, the...

Two-stage forward osmosis (FO)–reverse osmosis (RO)/BWRO and conventional RO/BWRO processes were evaluated for saline water treatment. Three different salts, NaCl, MgCl2 and MgSO4, were used as a draw solution. The performance of FO, RO and BWRO regeneration processes was simulated using predeveloped software. The simulation results showed that the water and solute flux across the FO membrane decreased with increasing the FO recovery rate. The highest water flux was in case of 1.2 mol NaCl draw solution for seawater desalination. The total power consumption for seawater desalination was lower in the RO process than in the FO–RO process. However, as the RO recovery rate increased, the difference in total power consumption between the conventional RO process and 0.65 mol MgCl2 FO–RO processes was insignificant. In case of brackish water desalination, the lowest specific power consumption and permeate TDS were in case of the conventional BWRO process and then followed by 0.32 mol MgSO4, 0.22 mol MgCl...

The ligand 4,4′-(1,2,4,5-tetrazine-3,6-diyl)dibenzoic acid has been designed and explored with the aim of using it as a linker to construct three-dimensional metal–organic frameworks (MOFs). We have been successful in the formation of a potassium 3D-MOF using this novel linker. This compound has a three-dimensional structure, wherein the layers formed by potassium ions and carboxylate groups are separated by this organic ligand. Luminescence and cytotoxicity studies have been performed. We used molecular simulations to predict the porous properties of an isoreticular compared to IRMOF-16 based on this linker due to the similarity of the newly designed ligand with p-terphenyl-4,4′′-dicarboxylate present in IRMOF-16.

The reaction of [Fe2(CO)9] with two representative imidazolium-2-dithiocarboxylate zwitterions derived from common N-heterocyclic carbenes (NHCs) bearing mesityl (IMes) or 2,6-diisopropylphenyl substituents on their nitrogen atoms (IDip) unexpectedly afforded two small bimetallic iron-carbonyl clusters with the generic formula [Fe2(CO)6(μ-κ2-S,S′-κ2-S,S′-S3C·NHC)]. After a brief optimization of the reaction conditions, these two “sulfur-enriched” products were isolated in low yields. They were fully characterized by IR, NMR, UV/Visible, and ESI-MS techniques, and their molecular structures were determined by single crystal X-ray diffraction analysis. The two compounds adopted a butterfly-type disposition in the solid state, with an [Fe2(CO)6] core bridged by the trithioperoxycarboxylate moiety of the in situ generated NHC·CS3 ligands. Bond lengths recorded for the CS3– unit revealed that its negative charge was mostly located on the remote sulfur atom.

The superbulky N-heterocyclic carbenes (NHCs) 2,6-bis(diphenylmethyl)-4-methylimidazol-2-ylidene (IDip*Me) and its 4-methoxy analogue (IDip*OMe) reacted instantaneously with carbon disulfide to afford the corresponding imidazolium-2-dithiocarboxylate zwitterions in high yields. These new dithiolate ligands were fully characterized and their coordination chemistry toward common Re(i) and Ru(ii) metal sources was thoroughly investigated. Neutral [ReBr(CO)3(S2C·NHC)] chelates featured three facially-arranged carbonyl groups on a distorted octahedron, whereas cationic [RuCl(p-cymene)(S2C·NHC)]PF6 complexes displayed a piano-stool geometry. The molecular structures of the six new compounds revealed that the NHC·CS2 inner salts were highly flexible. Indeed, the torsion angle between their anionic and cationic moieties varied between ca. 63° in the free ligands and 3° in the ruthenium complexes. Concomitantly, the S-C-S bite angle underwent a contraction from 131° to 110-113° upon chelation. Computation of the %VBur parameter showed that the dithiocarboxylate unit of the NHC·CS2 betaines chiefly determined the steric requirements of the imidazolium moieties, irrespective of the metal center involved in the complexation. The replacement of the p-methyl substituents of IDip*Me with p-methoxy groups in IDip*OMe did not significantly affect the ligand bulkiness. The more electron-donating methoxy group led, however, to small changes in various IR wavenumbers used to probe the electron donor properties of the carbene moiety.

Although Membrane Distillation (MD) has been extensively studied for desalination, it has other applications like removing all kinds of solutes from water and concentrating non-volatile substances. MD offers the possibility of producing a clean stream while concentrating valuable compounds from waste streams towards their recovery, or emerging contaminants and pathogens present in wastewater in order to facilitate their chemical elimination. This paper analyses the elimination of bacterial spores from contaminated water with MD and the role of MD in the subsequent treatment of the concentrate with photo-Fenton process. The experiments were performed at Plataforma Solar de Almeria (PSA) using a plate and frame bench module with a Permeate Gap Membrane Distillation (PGMD) configuration. Tests were done for two different kinds of spores in two different water matrixes: distilled water with 3.5wt% of sea salts contaminated with spores of Bacillus subtilis (B. subtilis) and wastewater after a secondary treatment and still contaminated with Clostridium sp. spores. An analysis of the permeate was performed in all cases to determine its purity, as well as the concentrated stream and its further treatment in order to assess the benefits of using MD. Results showed a permeate free of spores in all the cases, demonstrating the viability of MD to treat biological contaminated wastewater for further use in agriculture. Moreover, the results obtained after treating the concentrate with photo-Fenton showed a shorter treatment time for the reduction of the spore concentration in the water than that when only photo-Fenton was used.

Five complexes with the generic formula fac-[MnBr(CO)3(S2C·NHC)] were obtained by reacting [MnBr(CO)5] with a set of representative imidazol(in)ium-2-dithiocarboxylate zwitterions. These ligands are the adducts of N-heterocyclic carbenes (NHCs) and carbon disulfide. The mononuclear Mn(I) derivatives were coupled with Na[Mn(CO)5] to afford bimetallic [Mn2(CO)6(S2C·NHC)] clusters. Yet, the most convenient strategy to access these dinuclear Mn(0) products implied a direct carbonyl substitution from the [Mn2(CO)10] dimer. The molecular structures of three monometallic and four bimetallic compounds were elucidated by single crystal X-ray diffraction analysis. In the monometallic complexes, the NHC·CS2 ligands exhibited a bidentate κ2-S,S′ coordination mode with an S–C–S bite angle of about 116°. In the dinuclear clusters, the CS2− unit acted as a chelate toward one manganese center and as a pseudoallylic ligand toward the other one. The S–C–S bite angle was reduced to ca. 104°. Thus, the zwitterions displayed a remarkable flexibility, which also permitted a staggered arrangement of the carbonyl groups in the bimetallic systems. Examination of the CO absorption bands on IR spectroscopy helped identify the presence of fac-Mn(CO)3 or Mn2(CO)6 motifs, while the 13C NMR chemical shift of the CS2− moiety was a reliable indicator for monitoring its hapticity. Whereas the dinuclear clusters were air- and moisture-stable crystalline solids, mononuclear halido derivatives displayed only a limited stability under aerobic conditions. Both types of compounds underwent rather unselective, extensive fragmentations in the gas phase, in sharp contrast with the analogous rhenium derivatives that led to clean sequential decarbonylation processes upon collision-induced dissociation.

The effect of the metal ion and ligand design on the enantioselectivity and linkage isomerization of neutral cobalt and zinc bisthiosemicarbazone metallohelicates has been investigated in this work. The electrochemical synthesis has afforded the enantioselective formation of chirally pure cobalt helicates, and the ΛΛ isomer of a single enantiomer has been crystallized as only product for the cobalt methyl-substituted thiosemicarbazone helicate. Interestingly linkage isomers have been formed from zinc ethyl-substituted thiosemicarbazone helicate enantiomers for the first time. The co-existence of these isomers has been evaluated from the point of view of both experimental results and computational calculations.

Power generation by means of Pressure Retarded Osmosis (PRO) has been proposed for harvesting the energy of a salinity gradient. Energy recovery by the PRO process decreases along the membrane module due to depleting of the chemical potential across the membrane and concentration polarization effects. A dual stage PRO (DSPRO) design can be used to rejuvenate the chemical potential difference and reduce the concentration polarization on feed solution. Several design configurations were suggested for the membrane module arrangements in the first and second stage of the PRO process. PRO performance was evaluated for a number of salinity gradients proposed by coupling Dead Sea water or Reverse Osmosis (RO) brine with seawater or wastewater effluent. Maximum specific energy of inlet and outlet feeds was calculated using a developed computer model to identify the amount of recovered and remaining energy. Initially, specific power generation by the PRO process increased by increasing the number of modules of the first stage. Maximum specific energy is calculated along the PRO module to understand the degradation of the maximum specific energy in each module before introducing a second stage PRO process. Adding a second stage PRO process resulted in a sharp increase of the chemical potential difference and the specific energy yield of the process. Between 10% and 13% increase of the specific power generation was achieved by the DSPRO process for the Dead Sea-seawater salinity gradient depending on the dual stage design configuration. For Dead Sea-RO brine, 12–16% increase of the specific power generation was achieved by the dual stage PRO process. For Dead Sea-wastewater and RO brine-wastewater, a neutral and sometimes negative impact occurred when a second stage PRO process was introduced. We concluded that, for a given draw solution concentration, dual stage performs better than the conventional PRO process at high feed salinities, yet requires lower hydraulic pressure.

The synthesis of modified tripeptides (S)-Ala-γ-(R)-Glu-X, where X = (R,S) or (R,R) diastereomers of α-benzyl or α-(4-azidobenzyl)lanthionine, was carried out. The chemical strategy involved the enantioselective alkylation of a 4-MeO-phenyloxazoline. The reductive opening of the alkylated oxazolines, followed by cyclization and oxidation, led to four PMB-protected sulfamidates. Subsequent PMB removal, Boc protection and regioselective opening with cysteine methyl ester led to protected lanthionines. These compounds were further converted in a one pot process to the corresponding protected tripeptides. After ester and Boc deprotection, the four tripeptides were evaluated as potential analogues of the natural tripeptide (S)-Ala-γ-(R)-Glu-meso-A2pm. These compounds were evaluated for introduction, by means of the biosynthetic recycling pathway, into the peptidoglycan of Escherichia coli. A successful in vitro biosynthesis of UDP-MurNAc-tripeptides from the tripeptides containing α-benzyl lanthionine was achieved using purified murein peptide ligase (Mpl). Bioincorporation into E. coli W7 did not occur under different tested conditions probably due to the bulky benzyl group at the Cα carbon of the C-terminal amino acid.

In this work, we first show the findings of autopsy performed on the membranes used in the Scarab AB® membrane distillation (MD) system at the solar MD pilot plant in Plataforma Solar de Almeria (PSA) in Spain. The fouling and the damage endured by the MD membranes during intermittent long-term (2010–2013) solar-powered operation in the pilot plant were assessed and characterized. Different cleaning strategies were used to remove the fouling layer and restore the membrane properties. Data regarding relevant membrane characteristics for the MD process, such as contact angle, gas permeability, porosity, liquid entry pressure, mechanical strength, etc., and their relationship with the membrane performance under MD operation were discussed and analyzed. Scanning electron microscopy (SEM) was employed to study the morphology of the fouled and cleaned membranes and characterize the membrane damage. The identified best cleaning procedure was then applied in the MD plant system at PSA. Results suggested that cleaning effectively removed a great part of the fouling and reduced the wetting of the membranes. However, this improvement was offset by the effect of inactive periods during which wetting processes were favored.

We have been successful in the synthesis of a first in class Metal–Organic-Framework with novel 4′-tetrazolate-4-biphenyl carboxylate spacer. We report the in situ formation of a cadmium MOF by hydrothermal routes. The compound is a three-dimensional structure with small channels that shows an intense blue-green photoluminescence emission at room temperature in the solid state. To the best our knowledge, this is the first time that a coordination compound has been synthesized with this ligand.

Together with desalination, reuse of wastewater is considered as a solution to mitigate the water deficit in many areas. Membrane distillation (MD) is a technology increasingly proposed for desalination and water treatment. The process is supposed to produce pure distillate, and this is what this paper evaluates. Biologically contaminated water was used in a commercial prototype of spiral-wound liquid-gap MD coupled with solar thermal energy to assess the suitability of the process for removing pathogens. Tests were done during several hours for different operating conditions. The produced distillate, the rejected concentrated solution and the feed water were monitored through time and samples were taken for microbiological analysis. Results proved the efficiency of solar MD to produce a contaminant-free distillate when Escherichia coli, Fusarium solani and Clostridium sp spores were present in the feed water. Furthermore, in the first two cases the population of biological contaminants in the con...

The combination of Forward Osmosis (FO) and Reverse Osmosis (RO) was evaluated for seawater desalination. RO process was suggested for the draw solution regeneration because of its high efficiency and applicability for a wide range of ionic solution treatments. Two different salts, NaCl and MgCl2, were used as a draw solution. The performance of FO and RO regeneration processes was simulated using pre-developed software. A comparison between the RO and FO-RO processes was carried out. The simulation results showed that the total power consumption in the RO was lower than that in the FO-RO process. But, the difference in total power consumption between the RO and 0.65mol MgCl2 FO-RO processes was insignificant. The results also showed that the power consumption in the FO process was only 2%-4% of the total power consumption in the FO-RO process. However, the difference in total power consumption between the RO process and the FO-RO process decreased with a higher seawater salinity. In the FO-RO process, the results showed that the permeate TDS was increased with increasing the concentration of draw solution. The lowest permeate TDS was achieved in the 0.65mol MgCl2 FO-RO process and it was attributed to the high rejection rate of MgCl2 by the RO regeneration unit. © 2014 Elsevier B.V.

The deprotonation of 1,3-dimesitylbenzimidazolium tetrafluoroborate with a strong base afforded 1,3-dimesitylbenzimidazol-2-ylidene (BMes), which was further reacted in situ with rhodium or ruthenium complexes to afford three new organometallic products. The compounds [RhCl(COD)(BMes)] (COD is 1,5-cyclooctadiene) and cis-[RhCl(CO)2(BMes)] were used to probe the steric and electronic parameters of BMes. Comparison of the percentage of buried volume (%V(Bur)) and of the Tolman electronic parameter (TEP) of BMes with those determined previously for 1,3-dimesitylimidazol-2-ylidene (IMes) and 1,3-dimesitylimidazolin-2-ylidene (SIMes) revealed that the three N-heterocyclic carbenes (NHCs) had very similar profiles. Nonetheless, changes in the hydrocarbon backbone subtly affected the stereoelectronic properties of these ligands. Accordingly, the corresponding [RuCl2(PCy3)(NHC)(=CHPh)] complexes displayed different catalytic behaviors in the ring-closing metathesis (RCM) of α,ω-dienes. In the benchmark cyclization of diethyl 2,2-diallylmalonate, the new [RuCl2(PCy3)(BMes)(=CHPh)] compound (1d) performed slightly better than the Grubbs second-generation catalyst (1a), which was in turn significantly more active than the related [RuCl2(PCy3)(IMes)(=CHPh)] initiator (1b). For the formation of a model trisubstituted cycloolefin, complex 1d ranked in-between catalyst precursors 1a and 1b, whereas in the RCM of tetrasubstituted cycloalkenes it lost its catalytic efficiency much more rapidly.

Gold compounds to be obtained by the direct electrochemical oxidation of a noble metal are reported. This achievement provides an alternative procedure to obtaining neutral gold compounds with potential medical or catalytic applications.

The oxidation of various N,N′-diarylbenzene-1,2-diamines bearing bulky aromatic substituents with sodium periodate on wet silica gel afforded a series of five new dihydrophenazines instead of the expected cyclohexadiene-1,2-diimines. The reaction most likely proceeds via a 1,6-electrocyclic path and provides a convenient access to an important class of nitrogen heterocycles. Subsequent treatment of the mesityl derivative with chloromethyl pivalate and silver triflate led to the corresponding benzimidazolium salt.

The new homobimetallic ruthenium–vinylidene complex [(p-cymene)Ru(μ-Cl)3RuCl(═C═CHPh)(IMes)] (6) was isolated in high yield upon treatment of [(p-cymene)Ru(μ-Cl)3RuCl(η2-C2H4)(IMes)] (5) with a slight excess of phenylacetylene at −50 °C. Although it was very stable under normal atmosphere in the solid state, this product underwent an oxidative cleavage into the corresponding carbonyl compound [(p-cymene)Ru(μ-Cl)3RuCl(CO)(IMes)] (7) when dissolved in oxygen-containing solvents. Second-generation complexes 6 and 7 were characterized by IR and NMR spectroscopies, and their molecular structures were determined by X-ray diffraction analysis. The catalytic activity of complex 6 was probed in various types of olefin metathesis reactions. Compared to its first-generation analogue [(p-cymene)Ru(μ-Cl)3RuCl(═C═CHPh)(PCy3)], the new ruthenium initiator displayed an enhanced activity. It was also much more selective than ruthenium–ethylene complex 5. Aluminum chloride was a valuable cocatalyst for the ROMP of cyclooct...

The tandem catalysis of ring-closing metathesis/atom transfer radical reactions was investigated with the homobimetallic ruthenium–indenylidene complex [(p-cymene)Ru(μ-Cl)3RuCl(3-phenyl-1-indenylidene)(PCy3)] (1) to generate active species in situ. The two catalytic processes were first carried out independently in a case study before the whole sequence was optimized and applied to the synthesis of several polyhalogenated bicyclic γ-lactams and lactones from α,ω-diene substrates bearing trihaloacetamide or trichloroacetate functionalities. The individual steps were carefully monitored by 1H and 31P NMR spectroscopies in order to understand the intimate details of the catalytic cycles. Polyhalogenated substrates and the ethylene released upon metathesis induced the clean transformation of catalyst precursor 1 into the Ru(II)–Ru(III) mixed-valence compound [(p-cymene)Ru(μ-Cl)3RuCl2(PCy3)], which was found to be an efficient promoter for atom transfer radical reactions under the adopted experimental conditions.

Five new arylvinylidene complexes with substituents ranging from electron-donating to strongly withdrawing (p-OMe, p-Me, p-Cl, p-CF3, and m-(CF3)2) were isolated in high yields by reacting [(p-cymene)Ru(μ-Cl)3RuCl(η2-C2H4)(PCy3)] (3) with the corresponding phenylacetylene derivatives. The known phenylvinylidene complex [(p-cymene)Ru(μ-Cl)3RuCl(═C═CHPh)(PCy3)] (5) was also obtained from [RuCl2(p-cymene)]2, tricyclohexylphosphine, and phenylacetylene under microwave irradiation. The influence of the remote aryl substituents on structural features was investigated by IR, NMR, and XRD spectroscopies. A very good linear relationship was observed between the chemical shift of the vinylidene α-carbon atom and the Hammett σ-constants of the aryl group substituents. The catalytic activity of the six homobimetallic complexes was probed in various types of olefin metathesis reactions. Unsubstituted phenylvinylidene compound 5 served as a lead structure for these experiments. Its reaction with norbornene afforded hig...

Two new second generation ruthenium(II) dichloride-indenylidene complexes [RuCl 2 ,(9-isobutylphosphabicyclo[3.3.1]nonane)(NHC)(3-phenyl-1-indenylidene)], where NHC=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) or its unsaturated imidazol-2-ylidene analogue (IMes), were isolated in high yields upon heating a tetrahydrofuran (THF) solution of the diphosphane complex [RuCl 2 (isobutylphobane) 2 (3-phenyl-1-indenylidene)] with a two-fold excess of the corresponding imidazol-(in)ium-2-carboxylate zwitterions. Both products were characterized by 1 H, 13 C, and 31 P NMR spectroscopy, and the molecular structure of [RuCl 2 (isobutylphobane)(SIMes)(3-phenyl-1-indenylidene)] was determined by X-ray diffraction analysis. A close inspection of the packing structure revealed the presence of different types of intra- and intermolecular interactions that enhanced the global stability of the crystals, while low temperature NMR experiments showed the existence of two distinct rotational isomers due to the unsymmetrical nature of the phobane ligand. The catalytic activity of both compounds was assessed in olefin metathesis using benchmark ring-opening metathesis polymerization, ring-closing metathesis (RCM), and cross-metathesis reactions, and compared with those of related first and second generation ruthenium-benzylidene and indenylidene catalyst precursors. Kinetic studies confirmed the high thermal stability of the mixed isobutylphobane/N-heterocyclic carbene complexes, which suffered from a slow initiation efficiency compared to other catalytic systems based on the tricyclohexylphosphane ligand. However, the remarkable robustness of [RuCl 2 (isobutylphobane)(SIMes)(3-phenyl-1-indenylidene)] was beneficial for performing the RCM of diethyl 2,2-bis(2-methylallyl)malonate. Monitoring the formation of the ruthenium-methylidene active species [RuCl 2 (isobutylphobane)-(SIMes)(=CH 2 )] derived from this precursor further demonstrated its ability to sustain long reaction times and high temperatures required to carry out the RCM of tetrasubstituted olefins.

The need for biomaterials in dental and orthopedic applications has increased as the world population ages. Synthetic calcium phosphate bioceramics and calcium phosphate cements are proved potential substitutes for bone and teeth due to their structural and crystallographic similarities with the biological apatites, and their biocompatibility but they show poor mechanical properties. Chlorapatite and hydroxyapatite whiskers with high aspect ratio can be used to improve this drawback. This work describes a method to transform chlorapatite single crystals into hydroxyapatite whiskers, suitable for the reinforcement of calcium phosphate bioceramics and calcium phosphate cements. Hydroxyapatite whiskers were obtained by treating chlorapatite single crystals in high-temperature hydrothermal conditions. The variable studied was furnace temperature with and without moisture conditions. The characterization of the chlorapatite and hydroxyapatite whiskers was carried out by SEM, XRD, EDS and FTIR. SXRD data were analyzed for the description of the chlorapatite structure.

A [4+4] double-stranded cadmium dihelicate was afforded from an easily accessible thiosemicarbazone ligand; its crystal structure reveals the assembly of two enantiomers into dihelicate pairs, these pairs being further connected into infinite linear chains.

Two new sulfonamide-type fluorescent chemosensors in organic media are reported. The two receptors, [N,N'-bis(2-tosylaminobenzylidene)-1,2-diaminoethane and N,N'-bis(2-tosylaminobenzylidene)-1,3-diamino-2-propanol], display marked changes in the fluorescence emission intensities as a result of deprotonation by basic anions, and show high selectivity for fluoride over other inorganic anions, such as acetate or dihydrogenphosphate. These results suggest that the presence of the imine group as an intramolecular H-bond acceptor enhances the selectivity of these sensors compared to previous examples in the literature. The deprotonation mechanism has been demonstrated by spectrophotometric and spectrofluorimetric titrations as well as by NMR spectroscopy. The X-ray structures of both receptors are also discussed.

Four homobimetallic ruthenium-(p-cymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade pathway from the ethylene complex [(p-cymene)Ru(μ-Cl)3RuCl(PCy 3 )(η 2 -C 2 H 4 )] (7a). All the products were isolated and fully characterized by IR and NMR spectroscopies. The molecular structure of the indenylidene complex 11 was determined by X-ray crystallographic analysis. The catalytic activity of the four complexes was probed in various types of olefin metathesis reactions and compared with those of a related homobimetallic ruthenium-benzylidene complex, as well as first, second, and third generation monometallic Grubbs catalysts. In the ring-closing metathesis (RCM) of diethyl di-allylmalonate, the homobimetallic ruthenium-indenylidene complex 11 outperformed all the ruthenium-benzylidene complexes under investigation and was only slightly less efficient than its monometallic parent. Cross-metathesis experiments with ethylene showed that deactivation of ruthenium-benzylidene or indenylidene complexes was due to the rapid bimolecular decomposition of methylidene active species into ethylene complex 7a. Vinylidene and alleny-lidene complexes were far less efficient catalyst precursors for ring-opening metathesis polymerization (ROMP) or RCM and remained inert under an ethylene atmosphere. Their catalytic activity was, however, substantially enhanced upon addition of an acidic co-catalyst that most likely promoted their in situ transformation into indenylidene species. Due to its straightforward synthesis and high metathetical activity, homobimetallic ruthenium-indenylidene complex 11 is a valuable intermediate for the preparation of the Hoveyda-Grubbs catalyst [Cl 2 Ru(PCy 3 )(=CH-o-O-i-PrC 6 H 4 )] via stoichiometric cross-metathesis with 2-isopropoxystyrene. The procedure did not require any sacrificial phosphine and the transition metal not incorporated into the final product was easily recovered and recycled at the end of the process.

The neutral single-stranded monohelicate [Pd(HL)]·2(CH3CN) (1) aggregates in the solid state to give an infinite 1D supramolecular chain through either the cooperative action of hydrogen bonding and π-stacking interactions or by aromatic π-stacking alone.

We report the first structural evidence in the solid state of discrete water octamers with a 1,4-diaxially substituted hexameric chairlike conformation. These units were found to act as supramolecular glue in the aggregation of Pd(II) monohelicates to give a three-dimensional network through hydrogen-bonding.

Deprotonation of 1,3-di(2-tolyl)benzimidazolium tetrafluoroborate with a strong base afforded 1,3-di(2-tolyl)benzimidazol-2-ylidene (BTol), which dimerized progressively into the corresponding dibenzotetraazafulvalene. The complexes [RhCl(COD)(BTol)] (COD is 1,5-cyclooctadiene) and cis-[RhCl(CO)2(BTol)] were synthesized to probe the steric and electronic parameters of BTol. Comparison of the percentage of buried volume (%VBur) and of the Tolman electronic parameter (TEP) of BTol with those determined previously for 1,3-dimesitylbenzimidazol-2-ylidene (BMes) revealed that the two N-heterocyclic carbenes displayed similar electron donicities, yet the 2-tolyl substituents took a slightly greater share of the rhodium coordination sphere than the mesityl groups, due to a more pronounced tilt. The anti,anti conformation adopted by BTol in the molecular structure of [RhCl(COD)(BTol)] ensured nonetheless a remarkably unhindered access to the metal center, as evidenced by steric maps. Second-generation ruthenium-benzylidene and isopropoxybenzylidene complexes featuring the BTol ligand were obtained via phosphine exchange from the first generation Grubbs and Hoveyda-Grubbs catalysts, respectively. The atropisomerism of the 2-tolyl substituents within [RuCl2(=CHPh)(PCy3)(BTol)] was investigated by using variable temperature NMR spectroscopy, and the molecular structures of all four possible rotamers of [RuCl2(=CH-o-O(i)PrC6H4)(BTol)] were determined by X-ray crystallography. Both complexes were highly active at promoting the ring-closing metathesis (RCM) of model α,ω-dienes. The replacement of BMes with BTol was particularly beneficial to achieve the ring-closure of tetrasubstituted cycloalkenes. More specifically, the stable isopropoxybenzylidene chelate enabled an almost quantitative RCM of two challenging substrates, viz., diethyl 2,2-bis(2-methylallyl)malonate and N,N-bis(2-methylallyl)tosylamide, within a few hours at 60 °C.