Carboxylic Acid Units Research Articles

Red-emission, photobiological properties and antimicrobial photodynamic assays using mono-substituted corroles contain carboxylic acid and ester units

The mono-substituted corrole derivatives COOH-Cor and COOMe-Cor were obtained by Gryko methodology and characterized by microanaysis. In addition, we investigated experimental photophysical properties (absorption, emission by steady-state and time-resolved fluorescence) in some solvents and TDDFT calculations. Photobiological parameters such as aggregation, photostability and reactive oxygen species generation (ROS) was conducted. In addition, we also evaluated the preliminary antimicrobial photodynamic assays (aPDT) between studied corroles and bacteria strains, by white-light conditions.

Pseudodiproline (Pro-Cyp) Oligomers Fold into Helical Polyproline Type secondary structures.

The synthesis and conformational properties of oligo-proline mimetics composed of dimeric and tetrameric Pro-Cyp constructs linked by a hydroxymethylene unit are reported. Oligomers were studied both in the solid state and in solution, unveiling right-handed helical conformation depending on the configuration of the vicinally substituted trans-cyclopentane carboxylic acid unit (Cyp). Unlike polyproline oligomers, the alternating synthetic Pro-Cyp counterparts are not stabilized by n-π* interactions but rely instead on the steric demands of the extended backbone conformation within the hydroxymethylene-linked Pro-Cyp repeating units.

Experimental synthesis and characterization of PVA‐fumaric acid cross‐linked biodegradable films: Implications as a sustainable matrix for composites

AbstractPolyvinyl alcohol (PVA) is a widely used polymer that is biocompatible, nontoxic, and water‐soluble due to the presence of hydroxyl groups in its domain. This study aims to investigate the effects of fumaric acid (FA) cross‐linking and thermal cross‐linking (TC) on the PVA's mechanical and thermal properties. When the FA is mixed with PVA, it was found in the chemical reaction that the OH groups of PVA are condensing with the carboxylic acid units of FA to yield new ester linkages and water as a by‐product, which further results in the reduction of the water absorption capacity. Quantitatively, the addition of 8 (wt. /wt. %) FA resulted in a minimum of 65% water absorption rate, as compared with 117% for pure PVA. The mechanical and thermal properties of PVA also enhanced with the addition of 2% to 8% FA by weight. For the TC case, the % increase in ultimate tensile strength was 30.9% and 42.5% with and without TC, respectively. As the wt. % of FA increased from 2 to 10%, the % elongation value decreased for both with and without TC films relative to pure PVA. The thermogravimetric analysis revealed the change in degradation temperature of FA‐PVA blended film in comparison with pure PVA. Dynamic mechanical analysis was utilized to analyze the viscoelastic nature and temperature variation at the glass transition temperature. The current fabricated film is a potential candidate for the food packaging films application; moreover, the results reported in this investigation will accelerate the industrial applications of biodegradable PVA.Highlights Increasing the weight percentage of fumaric acid leads to an enhancement in mechanical and thermal properties of the film. Esterification is the usual reaction between fumaric acid and polyvinyl alcohol (PVA), in which ester linkages are formed when the carboxyl groups (‐COOH) of fumaric acid and the hydroxyl groups (‐OH) of PVA combine. Water absorption characteristics of the film reduces as the wt. % of fumaric acid increases. Thermal cross‐linking of the film leads to further improvements in mechanical and thermal properties. The overall effect of increasing the wt. % of fumaric acid is negative on the glass transition temperature of the film. The developed film is a potential candidate for the food packaging films application.

The impact of carboxylic acid anchoring groups on the optoelectronic and nonlinear optical properties of Ru complex dyes: A computational approach

In this study, density functional theory (DFT) and time-dependent DFT (TD-DFT) methods were used to analyze the effects of varying the number and positions of carboxylic acid anchoring groups attached to the bpy ligand of the [Ru(bpy)2(NCS)2] complex. Also the geometric structures, absorption geometry, electronic structures, optical properties, photovoltaic parameters, and nonlinear optical (NLO) properties of the designed [Ru(bpy)2(NCS)2] derivatives were investigated and compared with each other. The results indicate that the optoelectronic properties of these ruthenium (II) complexes are influenced by the number and positioning of carboxylic acid groups on the bipyridine moiety. Calculated values of ΔGinject and ΔGreg for the studied Ru(II) complexes suggest that the energy level alignment with the semiconductor and electrolyte satisfies the criteria. Furthermore, it was observed that the number and position of the anchoring carboxylic acid units is an effective approach to improve their NLO response. Overall, the structural modifications by the anchoring carboxylic acid groups on the bpy ligand of [Ru(bpy)2(NCS)2] complexes seem to fine-tune their DSSC performance and NLO response characteristics.

Covalent Organic Frameworks: Reversible 3D Coalesce via Interlocked Skeleton-Pore Actions and Impacts on π Electronic Structures.

Covalent organic frameworks (COFs) create extended two-dimensional (2D) skeletons and aligned one-dimensional (1D) channels, constituting a class of novel π architectures with predesignable structural ordering. A distinct feature is that stacks of π building units in skeletons shape the pore walls, onto which a diversity of different units can be assembled to form various pore interfaces, opening a great potential to trigger a strong structural correlation between the skeleton and the pore. However, such a possibility has not yet been explored. Herein, we report reversible three-dimensional (3D) coalescence and interlocked actions between the skeleton and pore in COFs by controlling hydrogen-bonding networks in the pores. Introducing carboxylic acid units to the pore walls develops COFs that can confine water molecular networks, which are locked by the surface carboxylic acid units on the pore walls via multipoint, multichain, and multidirectional hydrogen-bonding interactions. As a result, the skeleton undergoes an interlocked action with pores to shrink over the x-y plane and to stack closer along the z direction upon water uptake. Remarkably, this interlocked action between the skeleton and pore is reversibly driven by water adsorption and desorption and triggers profound effects on π electronic structures and functions, including band gap, light absorption, and emission.

An easy route for preparation of carboxylic acid and urea functional block copolymer as corrosion inhibitor

A novel POEGMA-b-(PMEEU-co-PMAA) (poly(oligo(ethylene glycol) methacrylate)-b-poly((methacrylamidoethyl) ethylene urea)-co-poly(methacrylic acid) block copolymer has been synthesized by RAFT polymerization as a corrosion inhibitor. Structural characterization of the block copolymer was done by FTIR, 13C NMR and 1H NMR spectroscopic techniques. The carboxylic acid and cyclic urea units on the block copolymer exert a synergistic effect on corrosion inhibition through chelating of the metal ions or adsorption to the metal surface. Corrosion inhibition of SAE 1012 carbon steel in a 1 M HCl medium has been investigated in the presence of 5 mM polymer using both experimental (electrochemical impedance spectroscopy, Tafel polarization (TP), weight loss) and theoretical approaches. Also, SAE 1012 carbon steel surface morphology changes were followed by energy dispersive X-ray spectroscopy and scanning electron microscopy. Electrochemical techniques indicated that the presence of PMEEU-co-PMAA segments of the polymer in the acid solution inhibits corrosion of SAE 1012 carbon steel. The inhibition efficiency of the polymer was found to be about 85%. According to TP studies, PMEEU-co-PMAA segment acts as a mixed type corrosion inhibitor. The adsorption of PMEEU-co-PMAA molecules onto the metal surface follows Langmuir adsorption isotherm. The K ads value calculated from the equilibrium constant of the adsorption process reflects a strong interaction. SEM and EDAX studies provide evidence of PMEEU-co-PMAA adsorption on the metal surface.

Modulation of Analytical Performance of a Bifunctional Optical Probe at the Micelle‐Water Interface: Selective Sensing of Histidine in Biological Fluid

AbstractBifunctional bis(indolyl)methane (BIM) derivatives with free carboxylic acid groups have been synthesized for the detection of heavy metal pollutants in the aqueous medium. Unlike in water, compounds in the presence of anionic micelle, showed color change from red to yellow specifically in the presence of Cu2+ ions. The incorporation of ionic surfactants could selectively block one of the binding sites, thereby improved the selectivity. In addition, large local concentration of metal ions (Cu2+) at micelle‐water interface of anionic surfactant improved the sensitivity. Metal ion binding at carboxylic acid (donor site) end not only alter the charge transfer state of the molecules, but also modify the self‐assembly property of probe molecules in the aqueous medium. The sensitivity as well as selectivity of the probes towards Cu2+ was found to be dependent on the number of carboxylic acid units on the central aryl ring. Further, the in‐situ formed Cu2+‐complex was involved for the ppb level recognition of histidine, an amino acid essential for protein biosynthesis and enzymatic activities. Finally, the present system was involved in the analysis of residual Cu2+ contents in natural water samples and histidine in the human urine sample.

High-level hierarchical morphology reinforcing covalent adaptable networks

High-level hierarchical morphology reinforcing covalent adaptable networks

Enhanced CO2 capture in nitrogen-enriched microporous carbons derived from Polybenzoxazines containing azobenzene and carboxylic acid units

In this study, we prepared nitrogen-doped microporous carbons (NMCs) from two different benzoxazine monomers (AMBZ, AEBZ), each containing both azobenzene and carboxylic groups, through a simple and environmentally friendly process of ring-opening polymerization (ROP), calcination, and KOH activation. We synthesized the AMBZ and AEBZ monomers through Mannich condensations of 4,4′-diaminodiphenylmethane (M) and 4,4′-diaminodiphenyl ether (E), respectively, with paraformaldehyde and 4-(4-hydroxphenylazo)benzoic acid (Azo-COOH). Differential scanning calorimetry (DSC) revealed that the thermal curing temperatures of AMBZ and AEBZ (both ca. 230 °C) were lower than that of a typical Pa-type benzoxazine monomer (263 °C), suggesting that the azobenzene and COOH units acted as promoters and catalysts for the ROP of the benzoxazine units. In addition, after ROP of the benzoxazine units of AMBZ and AEBZ, the polymers PAMBZ and PAEBZ, respectively, displayed high glass transition temperatures (Tg) and high thermal stability, as evidenced using DSC and thermogravimetric analysis (TGA), due to their greater cross-linking densities. We used Brunauer–Emmett–Teller analysis, TGA, wide-angle X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy to examine the specific surface areas, porous structures, chemical compositions, and thermal stabilities of the resulting KOH-activated NMCs PAMBZ-A and PAEBZ-A. The CO2 capture abilities and thermal properties of these two highly-nitrogen-doped microporous carbons, synthesized from polybenzoxazine (PBZ) resins containing azobenzene and COOH groups, were excellent when compared with those of other N-doped porous carbons derived from other PBZ matrices.

Highly Emissive Water‐Soluble Polysulfurated Pyrene‐Based Chromophores as Dual Mode Sensors of Metal Ions

Pyrene-based materials have gained considerable attention as stimuli-responsive chemical sensors. We designed a polysulfurated arene system based on a tetra(phenylthio)pyrene core decorated with four carboxylic acid units. Three different regioisomers, ortho, meta and para were studied in organic and aqueous solution. These systems are soluble in water at pH≥8 due to the deprotonation of carboxylic acids. The addition of metal ions cannot only quench the fluorescence of the central pyrene core, but also control the formation of three-dimensional nanoscopic objects in a dual mode function. Several divalent metal ions were tested and compared. Addition of ethylenediaminetetraacetic acid (EDTA) disassembles the non-emissive supramolecular system and restores the initial fluorescence of the pyrene core.

Bottom-Up Synthesized MoS2 Interfacing Polymer Carbon Nanodots with Electrocatalytic Activity for Hydrogen Evolution.

The preparation of an MoS2 -polymer carbon nanodot (MoS2 -PCND) hybrid material was accomplished by employing an easy and fast bottom-up synthetic approach. Specifically, MoS2 -PCND was realized by the thermal decomposition of ammonium tetrathiomolybdate and the in situ complexation of Mo with carboxylic acid units present on the surface of PCNDs. The newly prepared hybrid material was comprehensively characterized by spectroscopy, thermal means, and electron microscopy. The electrocatalytic activity of MoS2 -PCND was examined in the hydrogen evolution reaction (HER) and compared with that of the corresponding hybrid material prepared by a top-down approach, namely MoS2 -PCND(exf-fun), in which MoS2 was firstly exfoliated and then covalently functionalized with PCNDs. The MoS2 -PCND hybrid material showed superior electrocatalytic activity toward the HER with low Tafel slope, excellent electrocatalytic stability, and an onset potential of -0.16 V versus RHE. The superior catalytic performance of MoS2 -PCND was rationalized by considering the catalytically active sites of MoS2 , the effective charge/energy-transfer phenomena from PCNDs to MoS2 , and the synergetic effect between MoS2 and PCNDs in the hybrid material.

A Dual Stimuli Responsive Supramolecular Gel Provides Insulin Hydrolysis Protection and Redox‐Controlled Release of Actives

AbstractTwo supramolecular hydrogelators containing a central disulfide moiety and terminal carboxylic acid groups are studied. On the one hand, the hydrogels are responsive to a reductive environment, which transforms the disulfide unit to the corresponding thiols. On the other hand, the hydrogels show pH response associated with the presence of carboxylic acid units. Gels are formed at pH below ≈4 while at higher pH values, ionization of the gelators provokes gel disassembly. The properties of the gel are exploited for the release, as a proof of concept, of Bromophenol Blue in the presence of the reducing species tris(2‐carboxyethyl)phosphine hydrochloride. Additionally, insulin is loaded into the hydrogels and protected from hydrolysis with simulated gastric fluid containing pepsin. Quantitative release of unaltered insulin, checked with an enzyme‐linked immunosorbent assay colorimetric assay, is observed upon treatment with pH 7.4 buffer. This behavior would permit the use of the new hydrogels for oral insulin delivery.

Dihydrophenazine‐based double‐anchoring dye for dye‐sensitized solar cells

AbstractA novel dihydrophenazine‐based organic di‐anchoring dye DK‐11 was synthesized by utilizing a simple synthetic protocol. The dye was characterized by optical and electrochemical studies and used as a sensitizer for dye‐sensitized solar cell. The proposed butterfly structure was supported by IR experiments which ensured the binding of both carboxylic acid units on the semiconductor surface. Using the dye DK‐11, the device generated an efficiency of 5.07% with JSC, VOC, and FF values of 10.65 mA/cm2, 0.67 V, and 0.71, respectively.

Polar-Functionalized, Crosslinkable, Self-Healing, and Photoresponsive Polyolefins.

The nonpolar nature of polyolefins is one of their biggest limitations. Now, an efficient route to generate polar-functionalized, crosslinkable, self-healing, photoresponsive polyolefins with thermoplastic, elastomeric, and thermosetting properties is reported. Tunable amounts of carboxylic acid and a cyclic comonomer are installed onto polyolefins by palladium-catalyzed terpolymerization reactions. The incorporated carboxylic acid unit can alter the surface properties of polyolefins. The subsequently introduced Fe3+ /citric acid combination induces dynamic crosslinking and enables self-healing. Under UV light irradiation, citric acid reduces Fe3+ to Fe2+ and decreases the crosslinking density. The Fe2+ moiety can be easily oxidized back to Fe3+ , making the process reversible at the expense of citric acid. The incorporated cyclic comonomer modulates the crystallinity of polyolefins, provides elastic properties, and installs carbon-carbon double bonds for sulfur-induced vulcanization.

Syntheses of α-Amino Acids by Using CO2 as a C1 Source.

The incorporation of CO2 into organic compounds is currently one of the most active research topics in organic chemistry, because CO2 is an abundant, inexpensive, nontoxic, and renewable C1 source. However, CO2 is also a thermodynamically stable and kinetically inert gaseous compound, and as such, special strategies are required to activate CO2 and incorporate it into organic compounds. In particular, because the carbon atom adjacent to the nitrogen atom of amine derivatives is positively charged, umpolung carboxylation, which is a difficult chemical process, should be considered for the production of α-amino acids by using CO2 . In this Minireview, we summarize recent synthetic methods for α-amino acids that use CO2 as a carboxylic acid unit.

Influence of Side‐Chain Composition on Polythiophene Properties and Supramolecular Assembly of Anionic Polythiophene Derivatives

ABSTRACTA series of 10 polythiophene derivatives is reported, in which each polymer has a different percentage of carboxylic acid‐bearing repeat units. The properties of these polymers are explored under acidic conditions, where the carboxylic acid moieties remain neutral, and under basic conditions, where the carboxylic acid units become anionic carboxylates. The properties that are examined for both solutions and films include UV–vis absorption spectroscopy, photoluminescence spectroscopy, and red‐edge optical band gaps. All the properties studied are strongly dependent both on protonation state and percentage of carboxylic acid/carboxylate side chains along the polymer backbone. The anionic form of each polythiophene derivative was also used in layer‐by‐layer film deposition with a cationic phosphonium polyelectrolyte. The film growth process was studied by spectroscopic techniques to assess the influence of side‐chain composition on the film growth and optical properties. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019

Carboxylic Acid Functionalized Spin-Crossover Iron(II) Grids for Tunable Switching and Hybrid Electrode Fabrication.

Two carboxyl-substituted iron(II) grids, one protonated, [Fe4(HL)4](BF4)4·4MeCN·AcOEt (1), and the other deprotonated, [Fe4(L)4]·DMSO·EtOH (2), where H2L = 4-{4,5-bis[6-(3,5-dimethylpyrazol-1-yl)pyrid-2-yl]-1 H-imidazol-2-yl}benzoic acid, were synthesized. Single-crystal X-ray structure analyses reveal that both complexes have a tetranuclear [2 × 2] grid structure. 1 formed one-dimensional chains through intermolecular hydrogen bonds between the carboxylic acid units of neighboring grids, while 2 formed two-dimensional layers stabilized by π-π-stacking interactions. 1 showed spin transition between the 3HS-1LS and 1.5HS-2.5LS states around 200 K, while 2 showed spin-crossover between the 4LS and 2LS-2HS states above 300 K. A modified indium-tin oxide (ITO) electrode was fabricated by soaking the ITO in a solution of 1. The resultant electrode showed reversible redox waves attributed to the original redox processes of iron(II)/iron(III).

Effect and position of spiro-bipropylenedioxythiophene π-spacer in donor-π-spacer-acceptor dyes for dye-sensitized solar cell

Improper orientation and self-assembly of dyes on TiO2 surface are the main disadvantages at the dye-TiO2 interface that governs both charge injection and dye regeneration processes. In this report, a series of homo spiro-dimeric donor-π-spacer-acceptor (D-π-A) dyes based on bithiophene and terthiophene spacers with two-anchoring group containing dyes, TT1, T1T, TT1T were designed and synthesized by Pd-catalyzed successive Suzuki coupling followed by direct arylation reactions. The position of branching centre in TT1 and T1T was systematically varied, where the spiro unit was placed near and away from the anchoring carboxylic acid unit, respectively. The dimeric spiro-dye T1T showed device performance, which is 1.6 fold higher than its structural isomeric analogue TT1, of 3.9% with a Voc and Jsc of 0.593 V and 9.09 mA/cm2, respectively, whereas for the isomeric analogue TT1 a device performance of 2.45% (Voc of 0.568 V and Jsc of 6.25 mA/cm2) under simulated 1 Sun (100 mW/cm2) condition. The improved Voc for the dye T1T compared to TT1 dye was ascribed to the dipole moment exerted by the dyes on TiO2 surface. Further the PCE of 4.16% (Voc 0.589 V, Jsc 9.79 mA/cm2 respectively) maximum was observed, when an extra thiophene unit was inserted in between the donor and π-spacer in dye TT1T. The shifting the position of branching spiroBiProDOT π-spacer makes an impact on the device performance by synergistically enhancing both Voc and Jsc.

Sequence length distribution affects the lower critical solution temperature, glass transition temperature, and CO2-responsiveness of N-isopropylacrylamide/methacrylic acid copolymers

In this study we investigated the effects of the sequence length distributions in random and block copolymers of N-isopropylacrylamide and methacrylic acid (MAA)—PNIPAm-co-PMAA and PNIPAm-b-PMAA, prepared through free radical copolymerization and reversible addition fragmentation chain transfer (RAFT) polymerization, respectively—on their lower critical solution temperature (LCST), glass transition temperatures (Tg), and CO2-responsiveness. The insertion of the PMAA segment into PNIPAm enhanced the thermal properties (e.g., higher values of Tg) because of strong hydrogen bonding between the carboxylic acid units of the PMAA segment and the amide units of the PNIPAm segment, as determined using Fourier transform infrared and 1H NMR spectroscopy. The LCST increased upon increasing the pH for both the random and block copolymers, because the COOH units of the PMAA segments dissociated to form COO− groups, which improved the solubility in aqueous solutions. Furthermore, the variation in the LCST of PNIPAm93-b-PMAA7 with respect to pH was greater than that of PNIPAm-co-PMAA, due to the sequence length distribution effect. Treatment with supercritical CO2 (scCO2) also caused the values of Tg to increase for PNIPAm-co-PMAA but decrease for PNIPAm93-b-PMAA7, presumably because CO2 in the micelle structure of the block copolymer had a plasticization effect. Reversible CO2-responsiveness of the block copolymer in aqueous solution was evidenced by the appearance and disappearance of cloudy aqueous solutions upon alternating bubbling with CO2 and N2; this behavior was not observed for the random copolymers.

Facile construction of terpridine-based metallo-polymers in hydrogels, crystals and solutions directed by metal ions

Driven by tunable metal-ligand interactions, a polydentate ligand TC containing terpyridine and carboxylic acid units was developed to construct metallo-polymers that showed multiple aggregation modes with controlled macroscopic properties. In the presence of different kind of Zn2+ ions or NaOH, TC could form metallo-polymers via π-π stacking and metal-ligand interaction that further trapped water molecules, resulting in hydrogels and crystals. Moreover, these TC/Zn2+ hydrogels could transform to soluble and fluorescent aggregates in the presence of NaOH due to the formation of binuclear metallo-polymers with enhanced ICT emission. The metal-ligand interactions tuned by different metal salts in gels, crystals, and sols were also studied and illustrated in detail, it was also proved that water was an essential linker for constructing Na+-based metallo-polymers from the TC/NaOH crystal data. This work demonstrated the engineered coordination pathways in generating controllable hydrogels and metallo-polymers for the first time, which led to novel approach for facilely constructing a number of hydrogels with tailorable macroscopic properties.