Benzoic Acid Units Research Articles

A terbium coordination polymer based on mixed rigid and flexible organic ligands as a luminescent sensor for the convenient visual detection of ascorbic acid

Ascorbic acid (AA) is an essential antioxidant in the human body, whose detection is of significance in many fields. In this study, a two-dimensional terbium coordination polymer [Tb (dlba) (phen)]n (Tb-CP) based on a rigid 1,10-phenanthroline (phen) and a flexible 2-(3,5-dicarboxybenzyloxy) benzoic acid unit (H3dlba) was prepared under the hydrothermal conditions and characterized by Powder X-ray diffraction, elemental analysis, thermogravimetric analysis, infrared spectroscopy and single crystal X-ray diffraction. The Tb-CP synthesized via the mixed ligand strategy exhibits excellent water stability and acid-alkali resistance. As a luminescent sensor, the Tb-CP showed bright green luminescence characteristics of Tb3+, which was quenched after the addition of AA, with a quenching efficiency of 95.3 %. Additionally, the sensor shows high sensitivity and a rapid response time of 30 s. The detection limit is as low as 55.4 nM. In the actual sample test, the recovery rate of AA was 95–105 % (RSD< 1 %), indicating that the sensor has the potential for practical application. Furthermore, an integrated system based on Tb-CP and a smartphone can be employed for the visual detection of AA.

Replication of Sequence Information in Synthetic Oligomers.

ConspectusThe holy grail identified by Orgel in his 1995 Account was the development of novel chemical systems that evolve using reactions in which replication and information transfer occur together. There has been some success in the adaption of nucleic acids to make artificial analogues and in templating oligomerization reactions to form synthetic homopolymers, but replication of sequence information in synthetic polymers remains a major unsolved problem. In this Account, we describe our efforts in this direction based on a covalent base-pairing strategy to transfer sequence information between a parent template and a daughter copy. Oligotriazoles, which carry information as a sequence of phenol and benzoic acid side chains, have been prepared from bifunctional monomers equipped with an azide and an alkyne. Formation of esters between phenols and benzoic acids is used as the equivalent of nucleic base pairing to covalently attach monomer building blocks to a template oligomer. Sequential protection of the phenol side chains on the template, ester coupling of the benzoic acid side chains, and deprotection and ester coupling of the phenol side chains allow quantitative selective base-pair formation on a mixed sequence template. Copper catalyzed azide alkyne cycloaddition (CuAAC) is then used to oligomerize the monomers on the template. Finally, cleavage of the ester base pairs in the product duplex by hydrolysis releases the copy strand. This covalent template-directed synthesis strategy has been successfully used to copy the information encoded in a trimer template into a sequence-complementary oligomer in high yield.The use of covalent base pairing provides opportunities to manipulate the nature of the information transferred in the replication process. By using traceless linkers to connect the phenol and benzoic acid units, it is possible to carry out direct replication, reciprocal replication, and mutation. These preliminary results are promising, and methods have been developed to eliminate some of the side reactions that compete with the CuAAC process that zips up the duplex. In situ end-capping of the copy strand was found to be an effective general method for blocking intermolecular reactions between product duplexes. By selecting an appropriate concentration of an external capping agent, it is also possible to intercept macrocyclization of the reactive chain ends in the product duplex. The other side reaction observed is miscoupling of monomer units that are not attached to adjacent sites on the template, and optimization is required to eliminate these reactions. We are still some way from an evolvable synthetic polymer, but the chemical approach to molecular replication outlined here has some promise.

Syn and anti polymorphs of 2,6-dimethoxy benzoic acid and its molecular and ionic cocrystals: Structural analysis and energetic perspective

The conformational polymorphism in 2,6-dimethoxy benzoic acid, in which the acidic hydrogen atom can be either in an anti or a syn conformation with respect to the carbonyl oxygen atom, has been studied. The compound crystallizes in two conformational polymorphic forms, anti and syn. The COOH group lies out of the phenyl ring plane due to steric repulsion with the ortho-methoxy substituents. The acidic O–H bond in the COOH carboxyl group in anti appears to be more polar/ionic compared to the syn form. Both polymorphs were characterized by single-crystal X-ray diffraction and for the anti form a neutron diffraction measurement was carried out. In addition, a new molecular co-crystal (MCC) and a new ionic cocrystal (ICC) form were also obtained and characterized by single crystal X-ray diffraction in which the protonated 2,6-dimethoxy benzoic acid units adopt syn configuration. The crystal packing, hydrogen bonding and intermolecular interactions are discussed in terms of Hirshfeld surface analysis and derived properties such as the contact enrichment ratio and energy frameworks. Cohesive energies based on fully periodic DFT calculations as well as based on the sum of dimeric interaction energies were estimated for both syn and anti forms. They reveal the higher stability of the crystal structure in the anti form while the syn form is more stable in the isolated state. Room temperature Raman spectra were collected on the single crystals of the anti and ionic cocrystal forms and compared with both isolated-molecule and periodic calculations.

Integrated probing the influence of dye acceptor with several electron withdrawing groups for dye-sensitized solar cells

In order to explore the influence of diverse acceptors with varying amounts of electron withdrawing groups on the organic dye in dye-sensitized solar cell (DSCs), a series of JF419 organic analogues with several cyano groups (CN) on acceptor were engineered. By performing theoretical studies on these investigated dyes and the corresponding dye/(TiO2)38 complexes, two benzoic acid units (benzothiadiazole benzoic acid and vinyl benzoic acid) with more -CNs were identified as alternative acceptors for DSCs. Particularly, S3 and S5 dyes exhibited impressive red-shift in spectra (ca. 77 nm for S3 and 48 nm for S5 compared with JF419), more accessible charge separation state and large driving force for dye regeneration (ΔGreg = 0.51 eV for S3 and ΔGreg = 0.61 eV for S5). According to quantifying the charge transfer (CT) on semiconductor surface, it found that the growing electron withdrawing groups on acceptor can strengthen the interaction between dyes and TiO2 and provide favorable conditions for electron injection. A brilliant balance between the electron injection time (τ = 6.8 fs for S3 and τ = 7.3 fs for S5) and the electron-hole recombination distance (r = 20.5 Å for S3 and r = 19.2 Å for S5) could be acquired for S3 and S5 dyes. Synthetically, introducing electron withdrawing groups on acceptor for organic dyes is a valid approach for gaining great performance of DSCs.

Efficient Solar Cells Based on Porphyrin Dyes with Flexible Chains Attached to the Auxiliary Benzothiadiazole Acceptor: Suppression of Dye Aggregation and the Effect of Distortion.

Donor-π-acceptor-type porphyrin dyes have been widely used for the fabrication of efficient dye-sensitized solar cells (DSSCs) owing to their strong absorption in the visible region and the ease of modifying their chemical structures and photovoltaic behavior. On the basis of our previously reported efficient porphyrin dye XW11, which contains a phenothiazine-based electron donor, a π-extending ethynylene unit, and an auxiliary benzothiadiazole acceptor, we herein report the syntheses of novel porphyrin dyes XW26-XW28 by introducing one or two alkyl/alkoxy chains into the auxiliary acceptor. The introduced chains can effectively suppress dye aggregation. As a result, XW26-XW28 show excellent photovoltages of 700, 701, and 711 mV, respectively, obviously higher than 645 mV obtained for XW11. Nevertheless, the optimized structures of XW26 and XW27 exhibit severe distortion, showing large dihedral angles of 57.2° and 44.0°, respectively, between the benzothiadiazole and benzoic acid units, resulting from the steric hindrance between the benzoic acid unit and the neighboring alkyl/alkoxy chain on the benzothiadiazole unit, and thus blue-shifted absorption, decreased photocurrents. and low efficiencies of 5.19% and 6.42% were observed for XW26 and XW27, respectively. Interestingly, XW26 exhibits a more blue-shifted absorption spectrum relative to XW27, indicating that the steric hindrance of the alkyl/alkoxy chains has a more pronounced effect than the electronic effect. Different from XW26 and XW27, XW28 contains only one alkyl chain neighboring the ethynylene unit, which does not induce obvious steric hindrance with the benzoic acid unit, and thus distortion of the molecule is not seriously aggravated compared with XW11. Hence, its absorption spectrum and photocurrent are similar to those of XW11. As a result, a higher efficiency of 9.12% was achieved for XW28 because of its suppressed dye aggregation and higher photovoltage. It is worth noting that a high efficiency of 10.14% was successfully achieved for XW28 upon coadsorption with CDCA, which is also higher than the corresponding efficiency obtained for XW11. These results provide a novel approach for developing efficient porphyrin dyes by introducing chains into the suitable position of the auxiliary benzothiadiazolyl moiety to suppress dye aggregation, without seriously aggravating distortion of the dye molecules.

Isolation of Coralmycins A and B, Potent Anti-Gram Negative Compounds from the Myxobacteria Corallococcus coralloides M23.

Two new potent anti-Gram negative compounds, coralmycins A (1) and B (2), were isolated from cultures of the myxobacteria Corallococcus coralloides M23, together with another derivative (3) that was identified as the very recently reported cystobactamid 919-2. Their structures including the relative stereochemistry were elucidated by interpretation of spectroscopic, optical rotation, and CD data. The relative stereochemistry of 3 was revised to "S*R*" by NMR analysis. The antibacterial activity of 1 was most potent against Gram-negative pathogens, including Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumanii, and Klebsiella pneumoniae, with MICs of 0.1-4 μg/mL; these MICs were 4-10 and 40-100 times stronger than the antibacterial activities of 3 and 2, respectively. Thus, these data indicated that the β-methoxyasparagine unit and the hydroxy group of the benzoic acid unit were critical for antibacterial activity.

A Twist‐Bend Nematic Phase Driven by Hydrogen Bonding

AbstractThe liquid crystalline phase behavior of 4‐[6‐(4′‐cyanobiphenyl‐4‐yl)hexyloxy]benzoic acid (CB6OBA) and 4‐[5‐(4′‐cyanobiphenyl‐4‐yloxy)pentyloxy]benzoic acid (CBO5OBA) is described. Both acids show an enantiotropic nematic phase attributed to the formation of supramolecular complexes by hydrogen bonding between the benzoic acid units. In addition, CB6OBA provides the first example of hydrogen bonding driving the formation of the twist‐bend nematic phase. The observation of the twist‐bend nematic phase for CB6OBA, but not CBO5OBA, is attributed to the more bent molecular shape of the complexes formed by the former, reinforcing the view that shape is a key factor in stabilizing this new phase. Temperature‐dependent FTIR spectroscopy reveals differences in hydrogen bonding between the two nematic phases shown by CB6OBA which suggest that the open hydrogen‐bonded complexes may play an important role in stabilizing the helical arrangement found in the twist‐bend nematic phase.

A twist-bend nematic phase driven by hydrogen bonding.

The liquid crystalline phase behavior of 4-[6-(4'-cyanobiphenyl-4-yl)hexyloxy]benzoic acid (CB6OBA) and 4-[5-(4'-cyanobiphenyl-4-yloxy)pentyloxy]benzoic acid (CBO5OBA) is described. Both acids show an enantiotropic nematic phase attributed to the formation of supramolecular complexes by hydrogen bonding between the benzoic acid units. In addition, CB6OBA provides the first example of hydrogen bonding driving the formation of the twist-bend nematic phase. The observation of the twist-bend nematic phase for CB6OBA, but not CBO5OBA, is attributed to the more bent molecular shape of the complexes formed by the former, reinforcing the view that shape is a key factor in stabilizing this new phase. Temperature-dependent FTIR spectroscopy reveals differences in hydrogen bonding between the two nematic phases shown by CB6OBA which suggest that the open hydrogen-bonded complexes may play an important role in stabilizing the helical arrangement found in the twist-bend nematic phase.

Nanostructures of Nematic Materials of Laterally Branched Molecules

The synthesis and small-angle X-ray scattering (SAXS) characterization is reported for 20 laterally branched mesogenic molecules, which are derived from the common rod-shaped 2,5-bis([4-(octyloxy)phenyl]carbonyloxy) benzoic acid unit. These compounds have a varying degree of flexibility, in that their lateral branch is formed upon conversion of the acid to either an ester or an amide, and most laterally branched molecules exhibit relatively wide nematic liquid-crystal phases with a direct nematic-to-crystal transition at lower temperatures. SAXS studies reveal the presence of smectic-like nanostructures (clusters) with short-range order in the nematic phase, with characteristic correlation lengths from 3 to over 10 nm. The smectic layers that are contained in these clusters are tilted with respect to the nematic director by angles ranging from 0° (i.e. untilted) to 55°. In some compounds, the intensity of the SAXS peak corresponding to the smectic layer spacing depends strongly on temperature. The main features of the nanostructures can be understood based on the molecular structure; therefore, guiding future synthetic work towards more precisely controlled and technologically useful nanostructures in nematics.

3,5-Bis[(pyridin-4-yl)methoxy]benzoic acid

Single crystals of the title compound, C19H16N2O4, were obtained under hydro­thermal conditions by an unintended recrystallization of the employed microcrystalline starting material. The [(pyridin-4-yl)meth­oxy]benzoic acid unit is nearly planar, with a maximum deviation from the least-squares plane of 0.194 (2) Å. This plane is inclined by 35.82 (6)° to that defined by the second (pyridin-4-yl)meth­oxy group [in which the largest deviation from the least-squares plane is 0.013 (2) Å]. In the crystal, mol­ecules are linked by O—H⋯N hydrogen bonds involving the acid hy­droxy group and a pyridine N atom into chains parallel to [-201].

Synthesis and Characterization of Supramolecular Polymeric Materials Containing Azopyridine Units

AbstractSummary: The synthesis and characterization of a series of supramolecular polymeric complexes formed by H‐bonding interactions between benzoic acid and azopyridine derivatives are described. A series of polymeric networks have been synthesized using a polymethacrylate bearing benzoic acid units as side groups, and several polymers with azopyridine as H‐acceptor side groups. Furthermore, low‐molecular‐weight pyridine derivatives have been used to prepare an homologous side‐chain polymer, and a network with azopyridine as a non‐covalent crosslinker. Special attention was paid to the thermal and mesomorphic properties of these materials, which were studied by DSC, POM, and XRD.Micrograph of the mesomorphic melt of a sample taken at 130 °C on cooling from the isotropic state.magnified imageMicrograph of the mesomorphic melt of a sample taken at 130 °C on cooling from the isotropic state.

3,5-Lutidinium–2-chloro-4-nitrobenzoate–2-chloro-4-nitrobenzoic acid (1/1/1)

The title compound, C7H10N+·C7H3ClNO4−·C7H4ClNO4, consists of a 3,5-lutidinium (3,5-di­methyl­pyridinium) cation, a 2-chloro-4-nitro­benzoate anion and 2-chloro-4-nitro­benzoic acid. The anion is linked to the cation and the acid, respectively, by N—H⋯O and O—H⋯O hydrogen bonds. There are three C—H⋯O hydrogen bonds which connect the lutidinium–benzoate–benzoic acid units, forming a molecular tape.

Phase behavior of liquid-crystalline copolymer/liquid crystal blends

Thermodynamic phase behavior was studied for blends between side-chain liquid-crystalline (SCLC) copolymers and a low molecular weight liquid crystal (LC). SCLC copolymers, Copolyx having x mol fraction of a benzoic acid unit and 1−x mol fraction of a cyanobiphenyl group in their side chain, were prepared by radical polymerization and mixed with a low molecular weight LC, 4-cyano-4′-n-hexyloxybiphenyl (6OCB). The phase diagram of the Copoly0.24/6OCB blend exhibited an upper critical solution temperature which was not observed for homopolymer systems. Employing SCLC copolymers having two different kinds of mesogens in polymer/low molecular weight LC blends enabled us to obtain the new type of phase diagram.

Blends of side-chain liquid crystalline polymers: towards self-assembled interpenetrating networks

The possibility of using various types of non-covalent cross-linking, to promote the structure of interpenetrating networks in blends based on side-chain liquid crystalline polymers, was investigated. The polymers used included: (1) random copolymers of liquid crystalline polyacrylates containing benzoic acid units for hydrogen-bond cross-linking through the formation of intermolecular dimers; (2) liquid crystalline polyacrylate-ionomers bearing sodium salt groups for cross-linking through ionic aggregates; and (3) a styrene–butadiene–styrene triblock copolymer having a network structure with polystyrene microdomains as cross-links. The preparation method consists of making a dilute solution of two polymers, then evaporating the solvent and drying the mixture. No evidence of network interpenetrating was observed. The results suggest, however, that blends composed of two components having a network structure, for both H-bond/ionic-aggregate and H-bond/triblock-copolymer combinations, have a greater miscibility, compared with blends containing only one component capable of forming a network structure through non-covalent cross-linking. The improved miscibility is characterized by reduced domain sizes and, for blends of two liquid crystalline polymers, changes in the phase transition behavior.

Ferroelectric liquid crystals consisted of butyl lactate and 3-naphthyl-propenoic acid derivatives

3-(6-alkyloxy-2-naphthyl)propenoic acids were connected by phydroxybenzoic acid to L-(-)-ethyl lactate and L-(-)-butyl lactate, CnONPBLC2 and CnONPBLC4, respectively. CnONPBBLC4 series was obtained with one p-hydroxy benzoic acid unit more as the core. CnONPBLC2, n=6, 8, 10 and 12, exhibited enantiotropic smectic A (SA) phase in the range of 60 to 120 [ddot]C. Monotropic chiral smectic C (Sc*) phases were observed for n=10 and 12. CnONPBLC4 series exhibited enantiotropic SA phases. Sc* phases were observed for n=8 and 9 monotropically and n=12 and 14 enantiotropically. CnONPBBLC4 exhibited enantiotropic Sc* and SA phases. The transition temperatures for crystal to Sc*, Sc* to SA and SA to Iso were 80, 170 and 220 [ddot]C, respectively. Extremely wide temperature range for Sc* phase was observed. The values of Ps and tilting angle of C12ONPBLC4 were 54 nC/cm2 and 22 degrees, respectively, at 30 [ddot]C below the SA-Sc* transition.

Orientation distribution of liquid‐crystalline polyester sheets studied by polarized infrared spectroscopy

AbstractPolarized infrared spectroscopy was applied to evaluate the orientation distribution in extrusion‐molded sheets of a liquid‐crystalline copolyester consisting of 73 mol % of 4‐hydroxy benzoic acid units and 27 mol % of 2‐hydroxy‐6‐naphthoic acid units. The surface orientation function was evaluated from the polarized attenuated total reflection/Fourier transform infrared spectra and the polarized specular reflection spectra. In the case of the specular reflection method, the absorption and refractive indices were obtained from the specular reflectance using the Kramers–Kronig relation and the Fresnel equation. On the other hand, the microscopic orientation functions inside the sheets were evaluated by Fourier‐transform infrared microspectroscopy. The polarized FTIR microspectra of microtomed section of sheets were measured in a microscopic domain as small as 40 μ at various positions from the center of the sheet. The surface orientation function was shown to be higher than the interior orientation function. Orientation functions obtained by the spectroscopic techniques are lower than crystal orientation functions determined by wide‐angle x‐ray diffraction, implying that the crystal orientation function is higher than the orientation function of noncrystalline molecular chains. The orientation distribution in the sheet is discussed in relation to the morphological structures studied by scanning electron microscopy. © John Wiley &amp; Sons, Inc.

Investigations of the biosynthesis of novobiocin.

Abstract The biosynthesis of novobiocin was investigated using isotopically labelled compounds. The amino-group of the coumarin unit was found to be derived from tyrosine, other typical 7-oxycoumarin precursors were not incorporated into the coumarin unit of novobiocin, 4′-hydroxyphenylpyruvate was a better precursor of the substituted benzoic acid unit than was 4′-hydroxycinnamic acid. A biosynthetic route to this unit of novobiocin is suggested. Synthetic pathways for 2′,4′-dihydroxyphenylalanine-1-14C and 4-hydroxybenzaldehyde-U-14C are reported for the first time.