Cationic Moieties Research Articles

Zwitterionic Covalent Organic Framework Based Electrostatic Field Electrocatalysts for Durable Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are one of the most promising candidates for next-generation energy storage systems. To develop long-life LSBs, there is an urgent need to develop functional materials with higher catalytic activity toward polysulfides and reduced dendritic lithium growth. Herein, an electrostatic field electrocatalyst is designed in a zwitterionic covalent organic framework (COF) with a "two birds with one stone" ability for simultaneously overcoming obstacles in the lithium metal anode and sulfur cathode. The synergism between cationic and anionic moieties in the zwitterionic COF creates an electrostatic field for bidirectionally catalyzing S cathode conversion. Besides, the rational design of zwitterionic COF as a separator modification layer allows lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dissociation and fast lithium-ion conduction, which alleviates lithium dendrite growth and thus improves the cycling life of LSBs. This contribution not only pioneers the application of zwitterionic COF in the field of LSBs but also highlights the potential of electrostatic field electrocatalysts.

Synthesis and characterization of ammonium containing cyclocarbonates and polyurethanes there from

Using a three steps procedure a water soluble cationic bis-cyclocarbonate was prepared. Aminolysis was attempted in water but was not successful because of rapid hydrolysis of the starting cyclocarbonate in these basic conditions. Non-isocyanate polyurethanes (linear and crosslinked) were then prepared in acetonitrile with high yields. The resulting materials exhibited good thermal properties (Tdeg > 230 °C) and Tg > 60 °C. The presence of the cationic moiety led to hydrophilic materials with swelling rate of 45% and a plastification effect was observed with Tg decreasing down to −28 °C. Further, considering ammonium characteristics, antibacterial properties were assessed. Surface adhesion test showed a 99,9% inhibition towards gram-positive and gram-negative bacteria for the polyurethane thermoset. Acute toxicity was evaluated on the bis-cyclocarbonate oligomer confirming its innocuity in the studied concentration range.

Cationic Materials for Gene Therapy: A Look Back to the Birth and Development of 2,2-Bis-(hydroxymethyl)Propanoic Acid-Based Dendrimer Scaffolds.

Gene therapy is extensively studied as a realistic and promising therapeutic approach for treating inherited and acquired diseases by repairing defective genes through introducing (transfection) the "healthy" genetic material in the diseased cells. To succeed, the proper DNA or RNA fragments need efficient vectors, and viruses are endowed with excellent transfection efficiency and have been extensively exploited. Due to several drawbacks related to their use, nonviral cationic materials, including lipidic, polymeric, and dendrimer vectors capable of electrostatically interacting with anionic phosphate groups of genetic material, represent appealing alternative options to viral carriers. Particularly, dendrimers are highly branched, nanosized synthetic polymers characterized by a globular structure, low polydispersity index, presence of internal cavities, and a large number of peripheral functional groups exploitable to bind cationic moieties. Dendrimers are successful in several biomedical applications and are currently extensively studied for nonviral gene delivery. Among dendrimers, those derived by 2,2-bis(hydroxymethyl)propanoic acid (b-HMPA), having, unlike PAMAMs, a neutral polyester-based scaffold, could be particularly good-looking due to their degradability in vivo. Here, an overview of gene therapy, its objectives and challenges, and the main cationic materials studied for transporting and delivering genetic materials have been reported. Subsequently, due to their high potential for application in vivo, we have focused on the biodegradable dendrimer scaffolds, telling the history of the birth and development of b-HMPA-derived dendrimers. Finally, thanks to a personal experience in the synthesis of b-HMPA-based dendrimers, our contribution to this field has been described. In particular, we have enriched this work by reporting about the b-HMPA-based derivatives peripherally functionalized with amino acids prepared by us in recent years, thus rendering this paper original and different from the existing reviews.

Accelerated aerobic oxidative α-hydroxylation of 2-methylcyclohexanone with imidazolium ionic liquids

The great demands of chemical industries for environmental-friendly process draw interests on ionic liquids of high boiling points and low explosion risks. In this work, the aerobic α-hydroxylation of 2-methylcyclohexanone accelerated by 1-alkyl-3-methylimidazolium ionic liquids (ILs) was explored, where the ILs increased the efficiency considerably. ILs could also work as solvent and be separated from reaction mixture by extraction with organic solvents afterwards, where the anion moiety of ILs had a great impact on the reaction. After reaction, ethyl acetate was proved to be well-performed to separate BmimBF4 for next use. Besides, the imidazolium cation moiety was proved to accelerate the reaction via 1HNMR and ATR-FTIR. For mechanistic study, an interaction between imidazolium cation and ketone was proposed and, moreover, supported by ESI-MS. This work should encourage the application and understanding of ionic liquids in aerobic oxidation.

Convenient high resolution mass spectrometry characterization of aromatic sulfur-containing petroleum components following by preliminary S-alkylation with aliphatic alcohols

This paper describes rather suitable and variable preliminary derivatization strategy that may precede the molecular level characterization of sulfur-containing compounds of a particularly aromatic nature by high-resolution MALDI and ESI mass spectrometry. We demonstrated for the first time that free aliphatic alcohols (primary 1-alkanols C3–C20) in the presence of triflic acid provide easy S-alkylation of not only saturated sulfides but also most typical aromatic sulfur-containing compounds (benzothiophene, dibenzothiophene and their homologues) widely distributed and frequently analyzed in oil. The reaction proceeds quantitatively at rather mild conditions and gives rise to corresponding S-alkyl sulfonium salts the cation moieties of which can be detected using MALDI and ESI mass spectrometry with excellent signal/noise (S/N) ratios; the response ratios for target ions being quite close for both methods. Collision-induced dissociation (CID) of S-alkylsulfonium cations proceeds only by the elimination of entire S-alkyl group yielding protonated molecule of the analyte. This process can be useful for a reliable determination of target aromatic heterocyclic compounds in complex mixtures. The applicability of the method is illustrated by the analysis of deasphalted medium petroleum sample. The proposed derivatization principle is considered to be highly applicable as an alternative approach to routine characterization and sensitive determination of most typical sulfur-containing compounds and particularly of aromatic S-heterocycles in crude oils by soft-ionization mass spectrometry methods.

Color properties and non-covalent interactions in hydrated (Z)-4-(1-cyano-2-(2,4,5-trimethoxyphenyl)-vinyl)pyridin-1-ium chloride salt: Insights from experimental and theoretical studies

The optical charge-transfer (CT) property and the crystal structure of (Z)-4-(1-cyano-2-(2,4,5-trimethoxyphenyl)vinyl)pyridin-1-ium chloride monohydrate salt (I), which belongs to an acrylonitrile family, was studied. The title salt, I, was characterized using different spectroscopy techniques and a single-crystal X-ray diffraction study combined with quantum chemical computations. The results showed that the color properties of I are determined by the CT, changes in bandgap, optical absorption, and various non-covalent interactions. The HOMO-LUMO energy gaps are 5.41 eV and 5.23 eV for the precursor and salt, respectively. It was demonstrated that π-π stacking interactions lead to the formation of intercalated dimers and donor-acceptor interactions assisted by hydrogen bonds; the dimers and interactions are different between the precursor and the salt. The cation moiety is mainly stabilized by N(1)+-H···Cl, and the anion is predominantly stabilized by strong O(1W)– H⋯ Cl− bonds as well as the hydrogen bonds with the MeO group O(2W)–H⋯O(1) and O(2W)–H⋯O(1W). The charge transfer between cation and anion moieties in the structure is established through NBO analysis.

Understanding the influence of ethylene glycol on the microscopic behavior of imidazolium-based monocationic and dicationic ionic liquid

In the present work, the influence of a molecular co-solvent, ethylene glycol (EG) on the microscopic behaviour of an imidazolium-based dicationic ionic liquid (DIL) is analysed by employing time-resolved fluorescence anisotropy (TRFA) and nuclear magnetic resonance (NMR) spectroscopic techniques. In order to have a clear understanding of the specific role of DIL, a mono-cationic ionic liquid (MIL) containing an alkyl side chain unit, same as the alkyl spacer chain length of DIL, has also been investigated. The rotational diffusion of two fluorescent probes 9-PA and R110 have been carried out in both neat MIL and DIL and their mixtures with various fractions of EG. The analysis of the results has demonstrated that, within the studied concentration range, the microstructure of MIL encompassing both polar and nonpolar domains gets disrupted as the mole fraction of EG increases. However, a similar investigation in DIL has revealed that the micro-structure of DIL gets affected slightly when similar proportions of EG are added to DIL. This behaviour of DIL is attributed to the enhanced rigidity of the DIL structure due to its folded structural arrangements. Furthermore, NMR studies have provided additional insights into the interactions between the components of ILs and the added solvent. It has been observed that EG can form strong hydrogen-bonding interactions with the imidazolium-ring and alkyl chain protons of MIL. However, such interaction has not been observed in DIL. Moreover, the translational diffusion coefficient (Dt) value for the cationic moiety of both MIL and DIL, measured through NMR, has depicted that in the presence of EG, the change in Dtvalue is much higher for MIL than that for DIL. Overall, the outcome of the combined fluorescence and NMR studies have pointed out that the behaviour of DIL and MIL in the presence of a co-solvent is very different from one another and thus the individual mixture (IL+solvent) can be used for various targeted industrial applications.

Cell-permeable peptide nucleic acid antisense oligonucleotide platform targeting human betacoronaviruses.

Antisense oligonucleotides (ASOs) with therapeutic potential have recently been reported to target the SARS-CoV-2 genome. Peptide nucleic acids (PNAs)-based ASOs have been regarded as promising drug candidates, but intracellular delivery has been a significant obstacle. Here, we present novel modified PNAs, termed OPNAs, with excellent cell permeability that disrupt the RNA genome of SARS-CoV-2 and HCoV-OC43 by introducing cationic lipid moiety onto the nucleobase of PNA oligomer backbone. HCT-8 cells and Caco-2 cells were treated with 1 μM antisense OPNAs at the time of viral challenge and the Viral RNA levels were measured by RT-qPCR three days post infection. NSP 14 targeting OPNA 5 and 11, reduced the viral titer to a half and OPNA 530, 531 and 533 lowered viral gene expression levels to less than 50% of control by targeting the 5' UTR region. Several modifications (oligo size and position, etc.) were introduced to enhance the efficacy of selected OPNAs. Improved OPNAs exhibited a dose-dependent reduction in viral replication and nucleoprotein (NP) protein. When a mixture of oligomers was applied to infected cells, viral titer and NP levels decreased by more than eightfold. In this study, we have developed a modified PNA ASO platform with exceptional chemical stability, high binding affinity, and cellular permeability. These findings indicate that OPNAs are a promising platform for the development of antivirals to combat future pandemic viral infections that do not require a carrier.

Excellent corrosion inhibition and lubrication properties of carbon dot-based ionic liquids as water-based additives

Ionic liquids (ILs) and carbon dots (CDs) have gained more attention as versatile materials. Noticeably, the carbon dot-based ionic liquids (CDILs), a novel ionic combination of the two materials, will be endowed with superior performance and promote the application of CDs in fields of corrosion inhibition and lubrication. In this work, three CDILs with different alkyl chain numbers were synthesized as water-based multifunctional additives. CDILs show excellent corrosion inhibition effect in corrosive aqueous solution and superior lubricating behavior in water. Interestingly, CDILs with medium numbers of alkyl chains in cationic moiety exhibits optimal corrosion inhibition and lubrication performance. Both the physical adsorption of CDILs and the structures of cations influence the quality of adsorption and lubricating film.

Tetrabutylammonium Halides as Selectively Bifunctional Catalysts Enabling the Syntheses of Recyclable High Molecular Weight Salicylic Acid‐Based Copolyesters

AbstractTo synthesize high molecular weight poly(phenolic ester) via a living ring‐opening polymerization (ROP) of cyclic phenolic ester monomers remains a critical challenge due to serious transesterification and back‐biting reactions. Both phenolic ester bonds in monomer and polymer chains are highly active, and it is difficult so far to distinguish them. In this work, an unprecedented selectively bifunctional catalytic system of tetra‐n‐butylammonium chloride (TBACl) was discovered to mediate the syntheses of high molecular weight salicylic acid‐based copolyesters via a living ROP of salicylate cyclic esters (for poly(salicylic methyl glycolide) (PSMG), Mn=361.8 kg/mol, Ð<1.30). Compared to previous catalysis systems, the side reactions were suppressed remarkably in this catalysis system because phenolic ester bond in monomer can be selectively cleaved over that in polymer chains during ROP progress. Mechanistic studies reveal that the halide anion and alkyl‐quaternaryammonium cation work synergistically, where the alkyl‐quaternaryammonium cation moiety interacts with the carbonyl group of substrates via non‐classical hydrogen bonding. Moreover, these salicylic acid‐based copolyesters can be recycled to dimeric monomer under solution condition, and can be recycled to original monomeric monomers without catalyst under sublimation condition.

Tetrabutylammonium Halides as Selectively Bifunctional Catalysts Enabling the Syntheses of Recyclable High Molecular Weight Salicylic Acid-Based Copolyesters.

To synthesize high molecular weight poly(phenolic ester) via a living ring-opening polymerization (ROP) of cyclic phenolic ester monomers remains a critical challenge due to serious transesterification and back-biting reactions. Both phenolic ester bonds in monomer and polymer chains are highly active, and it is difficult so far to distinguish them. In this work, an unprecedented selectively bifunctional catalytic system of tetra-n-butylammonium chloride (TBACl) was discovered to mediate the syntheses of high molecular weight salicylic acid-based copolyesters via a living ROP of salicylate cyclic esters (for poly(salicylic methyl glycolide) (PSMG), Mn =361.8 kg/mol, Ð<1.30). Compared to previous catalysis systems, the side reactions were suppressed remarkably in this catalysis system because phenolic ester bond in monomer can be selectively cleaved over that in polymer chains during ROP progress. Mechanistic studies reveal that the halide anion and alkyl-quaternaryammonium cation work synergistically, where the alkyl-quaternaryammonium cation moiety interacts with the carbonyl group of substrates via non-classical hydrogen bonding. Moreover, these salicylic acid-based copolyesters can be recycled to dimeric monomer under solution condition, and can be recycled to original monomeric monomers without catalyst under sublimation condition.

X-ray structures, density functional theory study, DNA binding ability and micellization behaviour of decavanadates anions containing cationic organic moieties

Reported here synthesis, structure, DNA binding ability of three decavanadates complexes containing cationic organic moieties, 2-methylimidazolium (1), 4-dimethylaminopyridinium (2) and protonated 3-pyridiniumcarboxamide (3). Compounds are stable solids, characterized by elemental analyses, spectroscopic, single-crystal X-ray diffraction and theoretical studies. X-ray diffraction analysis indicates, the molecular structures of the compounds are composed of ion pairs formed by decavanadate ion [H2V10O28]4− and the corresponding cationic organic moieties. Complex 1 composed of decavanadate anion in combination with cationic 2-methylimidazolium and 2 contains decavanadate moiety with counter cation protonated 4-dimethylaminopyridine, two DMSO molecules. The structure of 3 consists of [H2V10O28]4−, protonated 3-pyridinecarboxamide, two co-crystallized neutral organic moieties with two molecules of water. The effective interaction of the ion-pair and hydrogen bonding interaction resulted in the cohesion, stabilization of solid state structure of the complexes. In solid state, compounds present interesting assemblies through the formation of H-bonds analyzed using DFT calculations and quantum theory of “atoms in molecules” (QTAIM). Interaction of the compounds with CT-DNA studied by absorption and fluorescence spectroscopy, show moderately strong intercalative mode of binding. Additionally micellization behaviour of the complexes using surfactant CTAB was studied by conductance measurements and absorption spectroscopy. The complexes show an increased solubility on addition of the surfactant.

(Invited) Corannulene-Based Molecular Nanographenes: Synthesis, Reduction, Supramolecular Complexation and Photophysical Properties

The outstanding electronic properties of graphene-based materials make them one of the most promising assets for application in the electronics industry of the XXI century. Encouraged by these properties, a great number of materials scientists are currently engaged in the development of the emergent field of 2D materials. In the last decade, the reduction of the dimensionality to 1D (nanoribbons) and 0D (nanographenes NGs, or graphene quantum dots, GQDs) have become an important research topic by their singular properties. In this regard, the quantum confinement of the electrons and the edge effects of these graphene derived structures makes possible the bandgap opening and, therefore, the appearance of a semiconductor behavior.The bottom-up preparation of these new structures, specifically employing stepwise organic synthesis, lead to monodisperse molecular nanographenes with atomically controlled morphology and, therefore, to the control of photophysical properties at will. An example of this synthetic management is the insertion of non-hexagonal rings in the honeycomb pattern of NGs, endowing Gaussian curvature to these structures and making molecules with bowl or saddle shapes.Our research group has described the wet synthesis of curved corannulene-based nanographenes by a stepwise Sonogashira–[4+2]–Scholl strategy.[1] Using bromocorannulene 1 as starting material, and depending on the temperature and the oxidant agent used in the Scholl reaction, a [6]helicene corannulene-based nanographene 2 or a positively-negatively curved nanographene 3 were prepared. These molecular curved NGs present interesting photophysical properties such as thermal activated delayed fluorescence (TADF) or dual emission.[2] Additionally, the multi-electron acceptor nature of molecular NGs allows the reduction with alkali metals that normally remains hosted in the pockets of curved nanographenes leading to potential energy storage systems. Within a collaborative work, the reduction of nanographene 2 with Na metal has recently been performed.[3] The formation of a “naked” dianion C76H64 2– (2 2–) solvent separated from the two cationic moieties was observed affording unprecedented selectively reduced species. DFT calculations revealed significant changes in the electron density and the inversion of the ring current aromaticity.Finally, concave–convex interactions between curved nanographenes and fullerenes are known to lead to supramolecular complexes with special interest as photoinduced electron transfer systems, mimicking the photosynthetic process. In a collaborative work,[4] the supramolecular complexation of nanographene 3 with C60 was experimentally monitored by H NMR spectroscopy and studied by DFT calculations.The formation of complexes with stoichiometries 2:1, 1:1 and 1:2 is possible. Furthermore, when the complex was irradiated at 460nm, the formation of the C60 radical anion is observed in an amazing photoinduced electron transfer process. References 1 J. M Fernández-García, P. Evans, S. Medina Ribero, I. Fernández, D. García-Fresnadillo, J. Perles, J. Casado, N. Martín, J. Am. Chem. Soc. 2018, 140, 17188.2 Manuscript in preparation.3 Z. Zhou, Y, Zhu, J. M. Fernández-García, Z. Wei, I. Fernández, M. Petrukhina, N. Martín et al., Chem. Commun. 2022, 58, 5574.4 S. Zank, J. M. Fernández-García, A. J. Stasyuk, A. A. Voityuk, M. Krug, M. Solà, D. Guldi and N. Martín, Angew. Chem. Int. Ed. 2022, 61, e202112834 Figure 1

Antibacterial broad-spectrum dendritic/gellan gum hybrid hydrogels with rapid shape-forming and self-healing for wound healing application.

Treating wound infections has been a difficult task ever since pathogenic bacteria started to develop resistance to common antibiotics. The present study develops hybrid hydrogels based on the formation of a polyelectrolyte complex between the anionic charges of dopamine-functionalized Gellan Gum (GG-DA) and the cationic moieties of the TMP-G2-alanine dendrimer. The hydrogels thus obtained can be doubly crosslinked with CaCl2 , obtaining solid hydrogels. Or, by oxidizing dopamine to GG-DA, possibly causing further interactions such as Shiff Base and Michael addition to take place, hydrogels called injectables can be obtained. The latter have shear-thinning and self-healing properties (efficiency up to 100%). Human dermal fibroblasts (HDF), human epidermal keratinocytes (HaCaT), and mouse monocyte cells (RAW 264.7), after incubation with hydrogels, in most cases show cell viability up to 100%. Hydrogels exhibit adhesive behavior on various substrates, including porcine skin. At the same time, the dendrimer served to crosslink the hydrogels and endow them with excellent broad-spectrum microbial eradication activity within four hours, evaluated using S. aureus 2569 and E. coli 178. Using the same GG-DA/TMP-G2-alanine ratios hybrid hydrogels with tunable properties and potential for wound dressing applications can be produced. This article is protected by copyright. All rights reserved.

Multicomponent Covalent Organic Framework Solid Electrolyte Allowing Effective Li-Ion Dissociation and Diffusion for All-Solid-State Batteries.

Organic solid electrolytes compatible with all-solid-state Li metal batteries (LMBs) are essential to ensuring battery safety, high energy density, and long-term cycling performance. However, it remains a challenge to develop an approach to provide organic solid electrolytes with capabilities for the facile dissociation of strong Li-ion pairs and fast transport of ionic components. Herein, a diethylene glycol-modified pyridinium covalent organic framework (DEG-PMCOF) with a well-defined periodic structure is prepared as a multicomponent solid electrolyte with a cationic moiety of high polarity, an additional flexible ion-transporter, and an ordered ionic channel for all-solid-state LMBs. The DEG-containing pyridinium groups of DEG-PMCOF allow a lower dissociation energy of Li salts and a smaller energy barrier of Li-ion transport, leading to high ion conductivity (1.71 × 10-4 S cm-1) and a large Li-ion transfer number (0.61) at room temperature in the solid electrolyte. The DEG-PMCOF solid electrolyte exhibits a wide electrochemical stability window and effectively suppresses the formation of Li dendrites and dead Li in all-solid-state LMBs. Molecular dynamics and density functional theory simulations provide insights into the mechanisms for the enhanced Li-ion transport driven by the integrated diffusion process based on hopping motion, vehicle motion, and free diffusion of DEG-PMCOF. The all-solid-state LMB assembled with a DEG-PMCOF solid electrolyte displays a high specific capacity with a retention of 99% and an outstanding Coulombic efficiency of 99% at various C-rates during long-term cycling. This DEG-PMCOF approach can offer an effective route to design various solid-state Li batteries.

Magnetic properties of an oxo-bridged dinuclear iron(III) complex resulting from the oxidation of mononuclear iron metallacycles with a flexible ethylenediphenylenebis(oxamate) ligand

Transition metal ions such as copper(II), nickel(II), cobalt(II), and manganese(II) are widely used in the formation of mono- or oligonuclear metallacyclic complexes with the flexible N,N’-2,2′-ethylenediphenylenebis(oxamate) ligand (H4edpba); however similar supramolecular complexes with iron(II) and iron(III) are rarely obtained. In this work, we synthesized for the first time a new air-stable oxo-bridged diiron(III) complex of formula {[Fe(H2edpba)(dmso)]2(μ-O)}·dmso·H2O (2) from dioxygen oxidation of the putative mononuclear iron(II) complex precursor of formula [Fe(H2edpba)(H2O)2]Cl (1) in dimethylsulfoxide (dmso). Compound 2 crystallizes in the monoclinic system and contains one oxo group bridging two cationic mononuclear metallacyclic moieties, [Fe(H2edpba)(dmso)]+. The iron(III) ions are also coordinated to four oxygen atoms from the dianionic H2edpba2− ligands in a tetradentate fashion, while an oxygen atom from the coordinated dmso molecules. Mössbauer spectroscopy confirms the presence of high-spin (HS) Fe3+ ions (2). The magnetic properties of 2 reveal a strong antiferromagnetic interaction between the two HS Fe3+ ions (J = −226.46 cm−1), in agreement with the DFT calculations (J = −207.99 cm−1).

Impact of the Cationic Moiety of Ionic Liquids on Chemoselective Artificial Olfaction.

Ionogels and derived materials are assemblies of polymers and ionic liquids characterized by high stability and ionic conductivity, making them interesting choices as gas sensors. In this work, we assessed the effect of the ionic liquid moiety to generate ionogels and hybrid gels as electrical and optical gas sensors. Six ionic liquids consisting of a constant anion (chloride) and distinct cationic head groups were used to generate ionogels and hybrid gels and further tested as gas sensors in customized electronic nose devices. In general, ionogel-based sensors yielded higher classification accuracies of standard volatile organic compounds when compared to hybrid material-based sensors. In addition, the high chemical diversity of ionic liquids is further translated to a high functional diversity in analyte molecular recognition and sensing.

Coexistence of Cationic and Anionic Phosphate Moieties in Solids: Unusual but Not Impossible.

Phosphoric acid is commonly known either as a neutral molecule or as an anion (phosphate). We theoretically confirm by ab initio molecular dynamics simulations (AIMD) that a cationic form H4PO4+ coexists with the anionic form H2PO4- in the same salt. This paradoxical situation is achieved by partial substitution of Cs+ by H4PO4+ in CsH2PO4. Thus, HnPO4 acts simultaneously as both the positive and the negative ion of the salt. We analyze the dynamical protonation pattern within the unusual hydrogen bond network that is established between the ions. Our AIMD simulations show that a conventional assignment of protonation states of the phosphate groups is not meaningful. Instead, a better description of the protonation situation is achieved by an efficiently fractional assignment of the strongly hydrogen-bonded protons to both its nearest and next-nearest oxygen neighbors.

Electronic, optical and spectroscopic properties of N-dialkyl-imidazolium hexafluorophosphate (CNMIM.PF6) ionic liquid crystal molecules investigated by computational methods.

In this present work, we calculate the electronic, spectroscopic and nonlinear optical properties (NLO) of N-dialkyl-imidazolium hexafluorophosphate (CNMIM.PF6, where N = 10, 12, 14, 16, 18, 20) ionic liquid crystal molecules under the effect of alkyl chain length variation in cation moiety [CNMIM]+ with fixed anion [PF6]-. CONTEXT: The majority of research on ionic liquid crystal to date has been focused on experiments, while theoretical studies on the optical properties of ionic liquid crystal have been extremely rare. Nonlinear phenomena in optical devices have attracted many researchers. Therefore, results of NLO properties may favor facile synthesis and fabrication of novel-type of materials as well as optoelectronic devices. Spectroscopic studies elucidate further insight into ionic liquid crystal behavior. The results demonstrate that variations in alkyl chain length have an impact on the conformers' electrical, spectroscopic, and NLO properties as well as their stability. The stability of ionic liquid crystal molecules increases with increasein the alkyl chain length and the energy band gap range is 6.64-6.29 eV. Understanding ionic liquid crystal's physical behavior requires an understanding of their dipole moments and NLO features, which are covered in this article. The results of NLO characteristics for all ionic liquid crystal molecules show that their first-order hyperpolarizabilities are higher than the reference molecule (urea). METHODS: The electronic (molecular energy band gap, electrostatic potential map, as well as HOMO-LUMO orbitals) and spectroscopic (IR-RAMAN, UV) properties were evaluated with the help of theoretical model at B3LYP/6-31G(d) while the NLO study has been performed using B3LYP and M06-2X with different basis sets 6-31G(d) and 6-311++G(d,p), as implemented in Gaussian09 software.

Synthesis and Evaluation of Functionalized Polyurethanes for pH-Responsive Delivery of Compounds in Chronic Wounds.

Chronic wounds, depending on the bacteria that caused the infection, can be associated with an extreme acidic or basic pH. Therefore, the application of pH-responsive hydrogels has been instigated for the delivery of therapeutics to chronic wounds. Herein, with the aim of developing a flexible pH-responsive hydrogel, we functionalized hydrophilic polyurethanes with either cationic (polyethylene imine) or anionic (succinic anhydride) moieties. A comprehensive physicochemical characterization of corresponding polymers was carried out. Particularly, when tested in aqueous buffers, the surface charge of hydrogel films was closely correlated with the pH of the buffers. The loading of the cationic and anionic hydrogel films with various compound models (bromophenol blue; negatively charged or Pyronin Y; positively charged) showed that the electrostatic forces between the polymeric backbone and the compound model will determine the ultimate release rate at any given pH. The potential application of these films for chronic wound drug delivery was assessed by loading them with an antibiotic (ciprofloxacin). In vitro bacterial culturing was performed using Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Results showed that at the same drug dosage, different release profiles achievable from cationic and anionic polyurethanes can yield different degrees of an antibacterial effect. Overall, our results suggest the potential application of cationic and anionic hydrophilic polyurethanes as flexible pH-responsive materials for the delivery of therapeutics to chronic wounds.