Carboxylic Acid Anions Research Articles

Development of an FeII Complex Exhibiting Intermolecular Proton Shifting Coupled Spin Transition.

In this study, we investigated reversible intermolecular proton shifting (IPS) coupled with spin transition (ST) in a novel FeII complex. The host FeII complex and the guest carboxylic acid anion were connected by intermolecular hydrogen bonds (IHBs). We extended the intramolecular proton transfer coupled ST phenomenon to the intermolecular system. The dynamic phenomenon was confirmed by variable-temperature single-crystal X-ray diffraction, neutron crystallography, and infrared spectroscopy. The mechanism of IPS was further validated using density functional theory calculations. The discovery of IPS-coupled ST in crystalline molecular materials provides good insights into fundamental processes and promotes the design of novel multifunctional materials with tunable properties for various applications, such as optoelectronics, information storage, and molecular devices.

Development of an FeII Complex Exhibiting Intermolecular Proton Shifting Coupled Spin Transition

AbstractIn this study, we investigated reversible intermolecular proton shifting (IPS) coupled with spin transition (ST) in a novel FeII complex. The host FeII complex and the guest carboxylic acid anion were connected by intermolecular hydrogen bonds (IHBs). We extended the intramolecular proton transfer coupled ST phenomenon to the intermolecular system. The dynamic phenomenon was confirmed by variable‐temperature single‐crystal X‐ray diffraction, neutron crystallography, and infrared spectroscopy. The mechanism of IPS was further validated using density functional theory calculations. The discovery of IPS‐coupled ST in crystalline molecular materials provides good insights into fundamental processes and promotes the design of novel multifunctional materials with tunable properties for various applications, such as optoelectronics, information storage, and molecular devices.

N-Benzylethanolammonium Ionic Liquids and Molten Salts in the Synthesis of 68Ga- and Al18F-Labeled Radiopharmaceuticals

Ionic liquids (ILs), due to their structural features, have unique physical and chemical properties and are environmentally friendly. Every year, the number of studies devoted to the use of ILs in medicine and pharmaceutics is growing. In nuclear medicine, the use of ILs with self-buffering capacity in the synthesis of radiopharmaceuticals is extremely important. This research is devoted to obtaining new ionic buffer agents containing N-benzylethanolammonium (BEA) cations and anions of carboxylic acids. A series of new BEA salts was synthesized and identified by NMR (1H, 13C), IR spectroscopy and elemental and thermal analysis. The crystal structures of BEA hydrogen succinate, hydrogen oxalate and oxalate were determined by x-ray diffraction. Newly synthesized compounds were tested as buffer solutions in 68Ga- and Al18F-radiolabeling reactions with a series of bifunctional chelating agents and clinically relevant peptides used for visualization of malignancies by positron emission tomography. The results obtained confirm the promise of using new buffers in the synthesis of 68Ga- and Al18F-labeled radiopharmaceuticals.

Tetrapyridineplatinum(II) Carboxylates: Synthesis and Crystal Structure

A series of mono- and bimetallic cation-anionic complexes based on the [PtPy4]2+ cation with different single-charge anions of carboxylic acids (RCOO–) is synthesized and structurally characterized. A synthetic approach to the preparation of tetrapyridineplatinum complexes [PtPy4]2+ soluble in polar solvents from available reagents is developed. The reaction of tetrapyridineplatinum dichloride [PtPy4](Cl)2 with silver acetate or trifluoroacetate affords compounds [PtPy4](OOCMe)2·6H2O (I) and [PtPy4](OOCCF3)2· 2H2O (II) in the form of crystalline hydrates (CIF files CCDC nos. 2161100 and 2161101, respectively) in high yields. Other carboxylates can be prepared by the treatment of compound I with an excess of a stronger acid, for example, trifluoroacetic acid, with the formation of the corresponding complex trifluoroacetate [PtPy4](OOCCF3)2·4CF3COOH (IIa) (CIF file CCDC no. 2161102). Another method consists of the displacement of acetic acid with an excess of a lowly volatile acid, for example, pivalic acid, when [PtPy4](Piv)2· 5HPiv (III) is formed from the acid melt, and solvatomorph [PtPy4](Piv)2·4HPiv·3C6H12 (IIIa) (CIF files CCDC nos. 2161103 and 2161104, respectively) is formed in a cyclohexane medium. Heteroanionic heterometallic complex [PtPy4](OOCFc)(OOCMe) (IV) (CIF file CCDC no. 2161105) is shown to be formed by the reaction of complex I with ferrocenecarboxylic acid under mild conditions.

Photochromic characteristics, photomodulated luminescence and ammonia vapor sensing properties of three D-A supramolecular assemblies

Synthesized three different supramolecular polymers, {[(4-BCBPY)0.5(H2BTEC)0.5]·H2O}n (1), {[(4-BCBPY)(C2H5NO)Cl]·H2O}n (2) and {[(4-BCBPY)(C2H5NO)Cl]·H2O}n (3) (H2BTEC2− = 1,2,4,5-benzenetetracarboxylic acid anion). In compound 1, benzene carboxylic acid anion acts as an electron donor, and electron-deficient viologen acts as an electron acceptor to form a supramolecular assembly. In compounds 2 and 3, electron-deficient viologen forms supramolecular assemblies with N-methylformamide, water and chloride ions. All three compounds are connected through non-covalent interactions and form a donor-acceptor (D-A) system. Compounds 1, 2 and 3 all exhibited photochromic behavior of electron transfer, while also exhibiting interesting photomodulated luminescence behavior. And compound 1 can also be used as an ammonia vapor sensor material. The photochromic mechanism of the compound and the correlation between calculation and practice are deeply studied by using time-dependent density functional theory (TDDFT).

Charge-Based Separation of Acid-Functional Polymers by Non-aqueous Capillary Electrophoresis Employing Deprotonation and Heteroconjugation Approaches.

Water-borne polymers are in ever-increasing demand due to their favorable ecological profile compared to traditional solvent-borne polymer systems. Many water-borne polymer particles are stabilized in aqueous media by the incorporation of acid-functional monomers. Due to the large variety of comonomers applied, these water-borne polymers have various superimposed statistical distributions, which make it challenging to obtain in-depth information regarding incorporation of the acidic monomers. For selective analysis of the incorporated acidic monomers, a charge-based non-aqueous capillary electrophoresis (NACE) separation was developed. Two approaches were developed: (i) deprotonation of the acid functionality with an organically soluble strong base and (ii) heteroconjugation of anions of carboxylic acids with incorporated acid functionality. In both approaches, N-methylpyrrolidone, as a strong solvent for polymers with a favorable relative permittivity for the presence of dissociated ionic species, was used for the separation. It was shown that anions of carboxylic acids specifically associate with the incorporated acid groups in the polymers, resulting in negatively charged complexes that could be separated based on charge-to-size ratio by NACE. Although both approaches give comparable results with respect to acid distribution for acid-functional polymers, the effective mobility of the deprotonated polymers is roughly double that obtained from the heteroconjugation approach. Unlike the heteroconjugation approach, deprotonation conditions were detrimental to the fused-silica capillary, limiting practical use. Polymers with different chemical compositions, molecular weights, and acid contents were subjected to the CE approaches developed. Polymers with varying molecular weight but similar relative acid monomer content were shown to have similar migration times, which confirms that this approach separates polymers based on charge-to-size ratio.

Photo-immobilization of pseudozwitterionic polymers with balanced electrical charge for developing anti-coagulation surfaces

This study aims to develop an economical coating agent that can easily impart excellent anti-coagulative property onto polymer surfaces. To this end, photo-reactable pseudozwitterionic polymer comprising cationic ammonium, anionic carboxylic acid, and photo-reactable phenyl azide group was synthesized via free-radical polymerization. Hydrophilicity, surface charge, surface elemental analysis, and anti-biofouling properties of the coated substrates were evaluated after photo-immobilizing the pseudozwitterionic polymer on the PET substrate. The pseudozwitterionic polymer was successfully immobilized; the coated substrate showed excellent anti-biofouling properties. Photo-immobilization of the pseudozwitterionic polymer was also confirmed to be effective in imparting anti-biofouling property onto the fibrous filtration membrane. The immobilized pseudozwitterionic polymer effectively prevented membrane blockage and safely filtered platelets from blood plasma.

Adsorption of Anions of Higher Carboxylic Acids on Magnesium from Weakly Alkaline Aqueous Solutions

The adsorption of sodium salts of higher carboxylates on oxidized magnesium is studied via in situ reflective ellipsometry. It is shown that the free energies of adsorption of sodium oleyl sarcosinate (OsS) and sodium linoleate (LiS) is >55 kJ/mol, indicating the chemisorption of carboxylates on oxidized magnesium surfaces. Electrochemical impedance spectra, voltammetry, and corrosion testing show that sodium oleate (OlS) has the best protective properties on pure and oxidized magnesium. The strong protective properties of OlS are confirmed by Mg plate testing under conditions of a wet atmosphere with daily condensation. Tentative passivation of chemically oxidized Mg in a 16 mmol/L OlS solution protects against corrosion for 92–96 h.

Palladium carbonyl complexes with anions of N-heterocyclic carboxylic and pyridine-2-sulfonic acids

Synthesis, spectral characteristics, and structure of palladium(I) carbonyl complexes containing anions of N-heterocyclic carboxylic acids and pyridine-2-sulfonic acid of the general formula [Pd(CO)(NHC-CO2)]n/[Pd(CO)(NHC-SO3)]n, where NHC is an N-heterocycle, were described. The resulting complexes can be attributed to a binuclear structure with bridging or terminal coordination of carbonyl ligands depending on the nature of the substituents in the heterocycle.

Investigating the tribological properties of PILs derived from different ammonium cations and long chain carboxylic acid anion

Abstract Ionic liquid–based lubricants exhibit a great potential to reduce friction and wear observed on metal surfaces. Their advantages in tribology were confirmed by many researchers. In this study, three protic ionic liquids (PILs) were synthesised: tert-oclylamine oleate, diethanolamine oleate, and dodecylamine oleate. Their physical and tribological properties were investigated. These synthesised PILs were used as neat lubricants in steel–steel sliding contact under a reciprocating motion. The coefficients of friction of the synthesised PILs are extremely low. The predicted mechanism to reduce friction is via an adsorption layer. The wear reduction ability was found to be dependent on cation structures. The observed results were compared with the phosphonium ionic liquid, synthetic bases oil, and fully formulated engine oil.

Polyelectrolyte Carboxymethyl Cellulose for Enhanced Delivery of Doxorubicin in MCF7 Breast Cancer Cells: Toxicological Evaluations in Mice Model.

Chemotherapy as an important tool for cancer treatment faces many obstacles such as multidrug resistance and adverse toxic effects on healthy tissues. Drug delivery systems have opened a new window to overcome these problems. A polyelectrolyte carboxymethyl cellulose polymer as a magnetic nanocarrier was synthesized for enhancing delivery and uptake of doxorubicin in MCF7 breast cancer cells and decreasing the adverse toxic effects to healthy tissues. The physicochemical properties of developed nanocarrier showed that it can be used in drug delivery purposes. The efficiency of the delivery system was assessed by loading and release studies. Besides, biological assays including protein-particle interaction, hemolysis assay, cytotoxicity study, cellular uptake, and apoptosis analysis were performed. All results persuaded us to investigate the cytotoxic effects of nanocarrier in an animal model by determining the biochemical parameters attributed to organ injuries, and hematoxylin and eosin (H&E) staining for histopathological manifestations. We observed that the nanocarrier has no toxic effect on healthy tissues, while, it is capable of reducing the toxic side effects of doxorubicin by more cellular internalization. Chemical characterizations and biological studies confirmed that developed nanocarrier with permanent cationic groups of imidazolium and anionic carboxylic acid groups is an effective candidate for anticancer drug delivery.

Elucidating the Reactivity of O2 (a 1Δg): A Study with Amino Acid Anions and Related Sulfur and Oxygen Anionic Species.

Rate constants and product ions were determined for a series of anions reacting with singlet molecular oxygen O2 (a 1Δg) at thermal energy using an electrospray ionization-selected ion flow tube. The 20 naturally occurring amino acids were used to produce corresponding deprotonated anions; only [Cys-H]- and [Pro-H]- were found to be reactive with O2 (a 1Δg), generating OSCH2CH(NH2)CO2- + HO and C5H6NO2- + H2O2, respectively. The reaction of O2 (a 1Δg) with [Cys-H]- has a rate constant more than ten times larger than the reaction of O2 (a 1Δg) with [Pro-H]-. Furthermore, reactions of O2 (a 1Δg) with carboxylic acid and thiol anions were carried out to elucidate the reactivity of the sulfur-containing functional groups. Potential energy surfaces and overall reaction exothermicities were calculated for representative reactions using density functional theory. Reactions in which attack occurs at the sulfur produce HCSO- as an ionic product. Reactions of several carboxylic acid anions likely proceed through a hydroperoxide intermediate that is analogous to that calculated for reactions with amino acid anions at a higher collision energy. Overall, rate constants for reactions of carboxylic acid anions RC(O)O- were found to be smaller for larger R groups.

Selective organ ischaemia/reperfusion identifies liver as the key driver of the post-injury plasma metabolome derangements.

Understanding the molecular mechanisms in perturbation of the metabolome following ischaemia and reperfusion is critical in developing novel therapeutic strategies to prevent the sequelae of post-injury shock. While the metabolic substrates fueling these alterations have been defined, the relative contribution of specific organs to the systemic metabolic reprogramming secondary to ischaemic or haemorrhagic hypoxia remains unclear. A porcine model of selected organ ischaemia was employed to investigate the relative contribution of liver, kidney, spleen and small bowel ischaemia/reperfusion to the plasma metabolic phenotype, as gleaned through ultra-high performance liquid chromatography-mass spectrometry-based metabolomics. Liver ischaemia/reperfusion promotes glycaemia, with increases in circulating carboxylic acid anions and purine oxidation metabolites, suggesting that this organ is the dominant contributor to the accumulation of these metabolites in response to ischaemic hypoxia. Succinate, in particular, accumulates selectively in response to the hepatic ischemia, with levels 6.5 times spleen, 8.2 times small bowel, and 6 times renal levels. Similar trends, but lower fold-change increase in comparison to baseline values, were observed upon ischaemia/reperfusion of kidney, spleen and small bowel. These observations suggest that the liver may play a critical role in mediating the accumulation of the same metabolites in response to haemorrhagic hypoxia, especially with respect to succinate, a metabolite that has been increasingly implicated in the coagulopathy and pro-inflammatory sequelae of ischaemic and haemorrhagic shock.

Structural investigation and molecular docking studies of 2-amino-1H-benzimidazolium 2-hydroxybenzoate and 2-amino-1H-benzimidazolium pyridine 2-carboxylate single crystal

The molecular complexes of 2-amino-1H-benzimidazolium 2-hydroxybenzoate (2ABHB) and 2-amino-1H-benzimidazolium pyridine 2-carboxylate (2ABP2C) were synthesised from a donor 2-aminobenzimidazole (2AB), and acceptors, 2-hydroxybenzoate (2HB) and pyridine 2-carboxylic acid (P2C) respectively. The brown colour single crystals were successfully grown by slow evaporation solution growth technique. The densities of grown crystals 2ABHB and 2ABP2C were measured by floatation method using carbon tetrachloride and xylene as solvents. The single crystal X-ray diffraction reveals the molecular structures of compounds 2ABHB and 2ABP2C. Both the structures contain positively charged 2-aminobenzimidazolium cation, 2ABHB contains negatively charged 2-hydroxybenzoate anion and 2ABP2C contains pyridine 2 carboxylic acid anions. 1H and 13C NMR spectral analyses were used to predict the presence of proton and carbon in the title compounds. The FTIR and Raman spectra have been recorded to detect the vibrational modes of functional groups present in the 2ABHB and 2ABP2C compounds. The proton transfer between the cation and anion was confirmed by UV–Vis spectra of both compounds. For both the compounds, thermal behaviour and stability of the crystals were studied using thermogravimetric and differential thermal analyses technique respectively. Further, the anti-bacterial activity of 2ABHB and 2ABP2C complex against Staphylococcus aureus, Klebsiella pneumonia, Pseudomonas eruginos and E. coli pathogens were investigated.

Structure Simulation and Host–Guest Interaction of Histidine-Intercalated Hydrotalcite–Montmorillonite Complex

The structures of histidine intercalated hydrotalcite–montmorillonite complex (His–LDHs–MMT) were studied using the DMol3 code, GGA/PW91 function, and DND basis set of the density functional theory (DFT). The geometries of His–LDHs–MMT were optimized, and their electronic properties were calculated. The results showed that the structure of the complex can be seen as that the quaternary ammonium group of histidine was adsorbed on the oxygen of MMT lamella, and its oxygen on the carboxylic acid anion was combined with the hydrogen atoms of the LDHs lamella. It was determined that the interaction mainly consisted in hydrogen bonding and electrostatic force. The average binding energies per histidine of His–LDHs and His–MMT were about −65.89 and −78.44 kcal/mol, respectively. The density of states of the complexes showed that the 2p orbitals of oxygen were dominant, and the 1s orbit of hydrogen near the Fermi level indicate the formation of hydrogen bonds in the complex. The charge density data displayed the density field of histidine carboxylic acid anion overlapped with that of hydrotalcite layer, indicating that a strong hydrogen bond interaction existed between histidine and hydrotalcite layer. The analysis of the electrostatic potential of complex indicated that the electrostatic interaction between histidine and MMT is obviously stronger than that of LDHs. The simulated XRD spectra showed the special diffraction peaks of LDHs and MMT layer in the complex.

Green biotransformations catalysed by enzyme-inorganic hybrid nanoflowers in environmentally friendly ionic solvents.

Environmentally friendly ionic solvents such as (a) ionic liquids (ILs) formulated with hydroxyl ammonium cations and various carboxylic acid anions and (b) choline chloride or ethyl ammonium chloride-based deep eutectic solvents (DES) were tested as media for hydrolytic and synthetic reactions catalysed by lipase-inorganic hybrid nanoflowers. The nature of ionic solvents used has a significant effect on the hydrolytic and synthetic activity of the immobilized lipase, as well as on its stability and reusability. In choline chloride-based DES, the activity and especially the operational stability of the biocatalyst are significantly increased compared to those observed in buffer, indicating the potential application of these solvents as green media for various biocatalytic processes of industrial interest.

Resonances of the anthracenyl anion probed by frequency-resolved photoelectron imaging of collision-induced dissociated anthracene carboxylic acid.

Resonances in polyaromatic hydrocarbon (PAH) anions are key intermediates in a number of processes such as electron transfer in organic electronics and electron attachment in the interstellar medium. Here we present a frequency- and angle-resolved photoelectron imaging study of the 9-anthracenyl anion generated through collision induced dissociation (CID) of its electrosprayed deprotonated anthracene carboxylic acid anion. We show that a number of π* resonances are active in the first 2.5 eV above the threshold. The photoelectron spectra and angular distributions revealed that nuclear dynamics compete with autodetachment for one of the resonances, while higher-lying resonances were dominated by prompt autodetachment. Based on electronic structure calculations, these observations were accounted for on the basis of the expected autodetachment rates of the resonances. Virtually no ground state recovery was observed, suggesting that the smallest deprotonated PAH that leads to ground state recovery is the tetracenyl anion, for which clear thermionic emission has been observed. The use of CID and photodissociation of organic carboxylic acid anions is discussed as a route to studying the dynamics of resonances in larger PAH anions.

Effective targeting of gemcitabine to pancreatic cancer through PEG-cored Flt-1 antibody-conjugated dendrimers

Tumor-targeted delivery of anticancer drugs using dendrimers has been recognized as a promising strategy to increase efficiency and reduce adverse effects of chemotherapy. Herein, we developed a dendrimer-based drug delivery system targeting Flt-1 (a receptor for vascular endothelial growth factors (VEGF)) receptor to improve therapeutic efficacy of gemcitabine in pancreatic cancer. Synthesized polyethylene glycol (PEG)-cored PAMAM dendrimers, which bear anionic carboxylic acid groups on the surface were modified with PEG chains, which were then conjugated with Flt-1 antibody. Following structural and chemical characterization studies, gemcitabine HCl-dendrimer inclusion complexes were successfully prepared. These complexes were efficiently engulfed by Flt-1 expressing pancreatic cancer cells, which enhanced the cytotoxicity of gemcitabine. Moreover, pancreatic tumors established in mice were highly targeted by PEG-cored Flt-1 antibody-conjugated dendrimers and increased accumulation of these gemcitabine-loaded complexes exhibited satisfactory in vivo anti-cancer efficacy. In conclusion, dendrimer-based targeted delivery of chemotherapeutics may serve as a promising approach for the treatment of malignancies such as pancreatic cancer that do not benefit from conventional chemotherapy.

A Chelation Strategy for In-situ Constructing Surface Oxygen Vacancy on {001} Facets Exposed BiOBr Nanosheets.

Surface defect of nanomaterials is an important physical parameter which significantly influences their physical and chemical performances. In this work, high concentration of surface oxygen vancancies (SOVs) are successfully introduced on {001} facets exposed BiOBr nanosheets via a simple surface modification using polybasic carboxylic acids. The chelation interaction between carboxylic acid anions and Bi3+ results in the weakness of Bi-O bond of BiOBr. Afterwards, under visible-light irradiation, the oxygen atoms would absorb the photo-energy and then be released from the surface of BiOBr, leaving SOVs. The electron spin resonance (ESR), high-resolution transmission electron microscopy (HRTEM), and UV–vis diffuse reflectance spectra (DRS) measurements confirm the existence of SOVs. The SOVs can enhance the absorption in visible light region and improve the separation efficiency of photo-generated charges. Hence, the transformation rate of adsorbed O2 on the as-prepared BiOBr with SOVs to superoxide anion radicals (•O2−) and the photocatalytic activity are greatly enhanced. Based on the modification by several carboxylic acids and the photocatalytic results, we propose that carboxylic acids with natural bond orbital (NBO) electrostatic charges absolute values greater than 0.830 are effective in modifying BiOBr.

Unusual Adsorption at the Air-Water Interface of a Zwitterionic Carboxybetaine with a Large Charge Separation.

The structures of layers of three different dodecylcarboxybetaine surfactants adsorbed at the air-water interface have been determined by neutron reflection. The zwitterionic compounds differed in the length of the spacer separating the quaternary ammonium and carboxylate groups, which was (CH2)1, (CH2)4, or (CH2)8. The limiting area per molecule was found to be 45, 52, or 84 Å(2), respectively, and compared reasonably with results from surface tension showing that the Gibbs prefactor is 1 in each case. Isotopic labeling was used to distinguish between the position of the alkyl and spacer groups in the layer. The spacer was found to be well-immersed in water for the (CH2)1 and (CH2)4 spacers but significantly above water for the (CH2)8 spacer. The distribution of the (CH2)8 spacer along the surface normal was found to be similar to that of the dodecyl group; i.e., it projects out of the water, contrary to an earlier hypothesis that it forms a loop. Comparison of the overlap of water with dodecyl and spacer groups also indicates that the (CH2)8 spacer is well out of the water. This in turn suggests that the anionic carboxylic acid group, which is dissociated in solution, is not ionized in the adsorbed layer. A further observation is that the dodecylcarboxybetaine with the (CH2)8 spacer reaches surface saturation at one-tenth of the critical micelle concentration. This is highly unusual and is attributed to the long spacer destabilizing the micelle relative to the surface layer.