In this work, the aqueous solubilities of two hydroxybenzoic acids (gallic and salicylic acid) and three phenylpropenoic acids (trans-cinnamic, ferulic, and caffeic acids) are addressed. Measurements ...were performed, as a function of temperature, between 288.15 and 323.15 K, using the shake-flask method for generating the saturated aqueous solutions, followed by compositional analysis by spectrophotometric and gravimetric methods. The pH values of the saturated aqueous solutions were measured by potentiometry. Additional thermodynamic properties, which are fundamental for a better understanding of the solubilization process, as well as necessary for the modeling studies, such as melting temperatures and fusion enthalpies were determined by differential scanning calorimetry (DSC). Apparent acid dissociation constants (K a) were obtained by potentiometry titration. The measured data were modeled with the cubic-plus-association (CPA) equation of state (EoS). This EoS is applied, for the first time, for multifunctional associating molecules, and the results indicate that it can adequately be used to represent the measured and other literature data with satisfactory accuracy.
Nitrogen-containing heteroaromatic cores are ubiquitous building blocks in organic chemistry. Herein, we present a family of metal-free intermolecular formal cycloaddition reactions that enable ...highly selective and orthogonal access to isoquinolines and pyrimidines at will. Applications of the products are complemented by a density functional theory mechanistic analysis that pinpoints the crucial factors responsible for the selectivity observed, including stoichiometry and the nature of the heteroalkyne.
A new dinuclear complex {Fe(tpc-OBn)(NCS)(μ-NCS)}2 (1) based on the tripodal tpc-OBn ligand (tpc-OBn = tris(2-pyridyl)benzyloxymethane), containing bridging μ-κN:κS-SCN and terminal κN-SCN ...thiocyanate ligands, has been prepared and characterized by single crystal X-ray diffraction, magnetic studies, and DFT theoretical calculations. This complex represents the first example of dinuclear FeII complex with double μ-κN:κS-SCN bridges in a head-to-tail configuration that exhibits ferromagnetic coupling between metal ions (J FeFe = +1.08 cm–1). Experimental and theoretical magnetostructural studies on this kind of infrequent FeII dinuclear complex containing a centrosymmetrically Fe2(μ-SCN)2 bridging fragment show that the magnitude and sign of the magnetic coupling parameter, J FeFe, depend to a large extent on the Fe–N–C (α) angle, so that J FeFe decreases linearly when α decreases. The calculated crossover point below which the magnetic interactions change from ferromagnetic to antiferromagnetic is found at 162.3°. In addition, experimental results obtained in this work and those reported in the literature suggest that large Ntripodal–FeII distances and bent N-bound terminal κN-SCN ligands favor the high spin state of the FeII ions, while short Ntripodal–FeII distances and almost linear Fe–N–C angles favor a stronger ligand field, which enables the FeII ions to show spin crossover (SCO) behavior.
A mononuclear Dy(III) complex with a non-Schiff base compartmental ligand has been prepared and characterised by X-ray crystallography and ac magnetic susceptibility measurements. The complex ...exhibits SIM behaviour induced by dilution and/or magnetic field with two thermally activated relaxation processes.
In the present work, two new copper complexes 3a and 3b with a Cu4O4 cubane core are reported. Both complexes are obtained by means of the in situ conversion of the imine functionality of Schiff's ...base ligands 1a (E)-4-chloro-2-((thiazol-2-ylimino)methyl)phenol and 1b (E)-4-bromo-2-((thiazol-2-ylimino)methyl)phenol into amino alcohols 2a (4-chloro-2-(hydroxy(thiazol-2-ylamino)methyl)phenol) and 2b (4-bromo-2-(hydroxy(thiazol-2-ylamino)methyl)phenol), respectively. The ligand transformation may be metal assisted and the generated ligands show an interesting mode of coordination in which the alkoxo-O atom binds in a μ3-manner connecting simultaneously three copper centers and forming a Cu4O4 cubane core. The first analysis of single crystal X-ray diffraction studies reveals that both molecules possess a 4 + 2 cubane-type core, and low temperature magnetic measurements show antiferromagnetic behaviour, in agreement with DFT calculations. However, the best fit and DFT calculations point out three pairs of coupling constants, more coherent with a 2 + 2 + 2 situation, in accordance with the fine analysis of structural data. Finally, phenoxazinone synthase activity has been measured for both molecules, finding kcat = 86.3 h-1 for the chloride derivative copper(ii) complex in methanol, whereas the bromide derivative copper(ii) complex displays kcat = 3.4026 × 102 h-1 and 10.289 × 102 h-1 in methanol and DMSO, respectively.
This work is focused on a case study of a small-scale Organic Rankine Cycle (ORC) adopted for electricity production from low-grade industrial waste heat recovery. This kind of applications raises a ...great interest due to the high amount of low-grade waste heat recoverable within industrial processes, but lacks of in-depth experimental investigations on the topic. The main reason is the difficulty to reach profitable small-scale projects, so more cost-effective solutions are being explored in the literature through thermo-economic optimizations. Nonetheless, the results obtained cannot be discussed with respect to actual operating data. In light of this, this paper proposes to conduct the thermo-economic optimization on the basis of an experimental application. In this manner, a comprehensive model of the facility is developed, calibrated, and validated from actual operating data. The model is used to conduct the thermo-economic optimization, revealing the influence of the organic fluid, cycle architecture, geometric parameters of main components, or control strategy used to obtain the best cost-effective solution. The main results show that, by means of a multivariable optimization using cost-effective ratios as objective function, a cheaper and powerful solution adapted to each specific project may be designed.
•ORC for low-grade waste heat recovery is assessed in industrial processes.•A thermodynamic an economic model of the ORC has been developed.•The model is used to perform a multivariable optimization.•Cost-effective ratios are used as objective functions.•A cheaper and powerful solution has been obtained for the case study.
In this work, pure solvent solubilities of drugs, such as paracetamol, allopurinol, furosemide and budesonide, measured in the temperature range between 298.2–315.2
K are presented. The solvents ...under study were water, ethanol, acetone, ethyl acetate, carbon tetrachloride and n-hexane. Measurements were performed using the shake-flask method for generating the saturated solutions followed by compositional analysis by HPLC. Previous literature values on the solubilities of paracetamol were used to assess the experimental methodology employed in this work. No literature data was found for any of the other drugs studied in this assay. Melting properties of the pure drugs were also determined by differential scanning calorimetry (DSC) to provide a broader knowledge about the solubilization process and also for modeling purposes.
The solubility data as a function of temperature were used to determine the thermodynamic properties of dissolution like, Gibbs energy, enthalpy and entropy. Theoretical work was essentially focused on the evaluation of the Nonrandom Two-Liquid Segment Activity Coefficient (NRTL-SAC) model, which has been referred as a simple and practical thermodynamic framework for drug solubility estimation. A satisfactory agreement was found between experimental and calculated values: the absolute average deviation was 68% for the correlation in the organic solvents and 38% for the prediction in water, where the best results in prediction could be related to the selected solvents.
We present here a novel example of spin crossover phenomenon on a Fe(II) one-dimensional chain with unusual N5S coordination sphere. The {Fe(tpc-OMe)(NCS)(μ-NCS)} n (1) compound was prepared ...using the tridentate tpc-OMe ligand (tpc-OMe = tris(2-pyridyl)methoxymethane), FeCl2·4H2O, and the KSCN salt. Crystallographic investigations revealed that the Fe(II) ions are connected by a single bridging NCS– ligand (μ-κN:κS-SCN coordination mode) to afford a zigzag neutral chain running along the 010 direction, in which the thiocyanato bridging groups adopt a cis head-to-tail configuration. The (N5S) metal environment arises from one thiocyanato-κS and two thiocyanato-κN ligands and from three pyridine of the fac-tpc-OMe tripodal ligand. This compound presents a unique extension of Fe(II) binuclear complexes into linear chains built on similar tripodal ligands and bridging thiocyanate anions. Compound 1 shows a spin crossover (SCO) behavior which has been evidenced by magnetic, calorimetric, and structural investigations, revealing a sharp cooperative spin transition with a transition temperature of ca. 199 K. Temperature scan rate studies revealed a very narrow hysteresis loop (∼1 K wide). Photoswitching of this compound was also performed, evidencing a very fast relaxation process at low temperature. Among other factors, the linearity of the N-bound terminal thiocyanato ligand appears as the main structural characteristic at the origin of the presence of the SCO transition in compound 1 and in the two others Fe(II) previous systems involving thiocyanato-bridges and tripodal tris(2-pyridyl)methane ligands.
The aim of this study was to determine the effectiveness of oxidation processes based on UV radiation (UV, UV/H2O2, UV/K2S2O8, and UV/Na2CO3) to remove bisphenol A (BPA) from aqueous solution. ...Results showed that UV radiation was not effective to remove BPA from the medium. The addition of radical promoters such as H2O2, K2S2O8, or Na2CO3 markedly increased the effectiveness of UV radiation through the generation of HO, SO4−, or CO3−/HCO3 radicals, respectively. The reaction rate constants between BPA and HO, SO4−, and CO3−/HCO3 radicals were kHOBPA=1.70±0.21×1010M−1s−1, kSO4-BPA=1.37±0.15×109M−1s−1 and kCO3-/HCO3BPA=3.89±0.09×106M−1s−1, respectively. The solution pH had a major effect on BPA degradation with the UV/H2O2 system, followed by UV/K2S2O8, and UV/Na2CO3 systems. All oxidation systems in this study showed 100% effectiveness to remove BPA from wastewater, due to its large content of natural organic matter (NOM), which can absorb UV radiation and generate excited triplet states (3NOM*) and various reactive oxygen species. With all three systems, the total organic carbon in the medium was markedly decreased after 5min of treatment. The toxicity of byproducts was higher than that of BPA when using UV/H2O2, similar to that of BPA with the UV/Na2CO3 system, and lower than that of BPA after 40min of treatment with the UV/K2S2O8 system.
•Removal of bisphenol A (BPA) using UV, UV/H2O2, UV/K2S2O8, or UV/Na2CO3 was studied.•The reaction rate constants between BPA and HO•, SO4•−, and CO3•−/HCO3• were obtained.•The solution pH had a major effect on BPA photodegradation.•The UV/K2S2O8 system was the most efficient to remove and mineralize BPA.•The three oxidation systems showed 100% effectiveness to remove BPA from wastewater.
A new family of homochiral silver complexes based on carbophilic interactions with ortho‐phenylene ethynylene (o‐OPE) scaffolds containing up to two silver atoms are described. These compounds ...represent a unique class of complexes with chirality at the metal. Chiral induction is based on the inclusion of chiral sulfoxides, which allow efficient transfer of chirality to the helically folded o‐OPE, leading to circularly polarized luminescence (CPL)‐ and vibrational circular dichroism (VCD)‐active compounds. In the presence of silver(I) cations, carbophilic interactions dominate, which promote helical structures with a defined helicity. This is one of the very scarce examples of the use of such interactions in the attractive field of abiotic foldamers. The switching event has been extensively studied by using different chiroptical techniques, including circular dichroism, CPL, and VCD, and represents one of the few CPL switches described in the literature.
Silver twists: A new family of homochiral silver complexes based on carbophilic interactions with ortho‐phenylene ethynylene (o‐OPE) scaffolds containing up to two silver atoms are described. In the presence of silver(I) cations, carbophilic interactions dominate, which promote helical structures with a defined helicity (see figure). This is one of the very scarce examples of the use of such interactions in the attractive field of abiotic foldamers.
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