Infrared and Raman spectra of phtalate, isophtalate and terephtalate ions

Direct Probing of Vibrational Interactions in UiO-66 Polycrystalline Membranes with Femtosecond Two-Dimensional Infrared Spectroscopy

UiO-66 is a benchmark metal-organic framework that holds great promise for the design of new functional materials. In this work, we perform two-dimensional infrared measurements on polycrystalline membranes of UiO-66 grown on c-sapphire substrates. We study the symmetric and antisymmetric stretch vibrations of the carboxylate groups of the terephthalate linker ions and find that these vibrations show a rapid energy exchange and a collective vibrational relaxation with a time constant of 1.3 ps. We also find that the symmetric vibration of the carboxylate group is strongly coupled to a vibration of the aromatic ring of the terephthalate ion. We observe that the antisymmetric carboxylate vibrations of different terephthalate linkers show rapid resonant (Förster) energy transfer with a time constant of ∼1 ps.

Structures, Bonding and Sensor Properties of Some Alkaline o-Phthalatocuprates

Comprehensive study of the structure and bonding of disodium, dipotassium and diammonium di-o-phthalatocuprates(II) dihydrates has been undertaken. The crystal structure of ammonium o-phthalatocuprate has been determined. The identity of structures of phthalatocuprate chains in potassium and ammonium salts has been revealed. Vibrational spectra of all three compounds have been recorded, and the assignment of vibrational bands has been made. Force field calculations have shown a minor effect of outer-sphere cations (Na+, K+, NH4+) on both intraligand (C-O) and metal-ligand bond strengths. Synthesized compounds have been tested as electrochemical sensors on D-glucose, dopamine and paracetamol. Their sensitivity to analytes varied in the order of Na+ > K+ > NH4+. This effect has been explained by the more pronounced steric hindrance of copper ions in potassium and ammonium salts.

Crystallinity after decarboxylation of a metal-carboxylate framework: indestructible porosity for catalysis

We report a curious case study of a Zr(iv)-carboxylate framework, which retains significant crystalline order after cascade thermocyclization of its linker components, and - more notably - after the crucial carboxylate links were severed by heat. Vigorous heat treatment (e.g., 450 °C and above) benzannulates the multiple alkyne groups on the linker to generate linked nanographene blocks and to afford real stability. The resultant Zr oxide/nanographene hybrid solid is stable in saturated NaOH and concentrated H₃PO₄, allowing a convenient anchoring of H₃PO₄ into its porous matrix to enable size-selective heterogeneous acid catalysis. The Zr oxide components can also be removed by strong hydrofluoric acid to further enhance the surface area (up to 650 m² g^-1), without collapsing the nanographene scaffold. The crystallinity order and the extensive thermal transformations were characterized by X-ray diffraction, scanning transmission electron microscopy (STEM), IR, solid state NMR and other instrumental methods.

Atomic/molecular layer deposition and electrochemical performance of dilithium 2-aminoterephthalate

Crystalline Li-terephthalate and amino-functionalized Li-terephthalate thin film electrodes are fabricated from gaseous precursors with ALD/MLD to show that the electron-donating amino group lowers the redox potential.

Formation of uranyl phthalate coordination polymers with unusual 2D net topologies in the presence of organic cations

Inclusion of heterocyclic cations into a uranyl-phthalate system allowed the formation of 2D coordination polymers whose topological analysis revealed that the underlying nets had unusual topologies.

Synergistic chemo-enzymatic hydrolysis of poly(ethylene terephthalate) from textile waste

Due to the rising global environment protection awareness, recycling strategies that comply with the circular economy principles are needed. Polyesters are among the most used materials in the textile industry; therefore, achieving a complete poly(ethylene terephthalate) (PET) hydrolysis in an environmentally friendly way is a current challenge. In this work, a chemo‐enzymatic treatment was developed to recover the PET building blocks, namely terephthalic acid (TA) and ethylene glycol. To monitor the monomer and oligomer content in solid samples, a Fourier‐transformed Raman method was successfully developed. A shift of the free carboxylic groups (1632 cm⁻¹) of TA into the deprotonated state (1604 and 1398 cm⁻¹) was observed and bands at 1728 and 1398 cm⁻¹ were used to assess purity of TA after the chemo‐enzymatic PET hydrolysis. The chemical treatment, performed under neutral conditions (T = 250 °C, P = 40 bar), led to conversion of PET into 85% TA and small oligomers. The latter were hydrolysed in a second step using the Humicola insolens cutinase (HiC) yielding 97% pure TA, therefore comparable with the commercial synthesis‐grade TA (98%).

Functional conductive nanomaterials via polymerisation in nano-channels: PEDOT in a MOF

Reactions inside the pores of metal-organic frameworks (MOFs) offer potential for controlling polymer structures with regularity to sub-nanometre scales. We report a wet-chemistry route to poly-3,4-ethylenedioxythiophene (PEDOT)-MOF composites. After a two-step removal of the MOF template we obtain unique and stable macroscale structures of this conductive polymer with some nanoscale regularity.

Water interactions in metal organic frameworks

Insight into the structural variation of metal organic framework materials upon hydration.

Molecular structure and vibrational spectra of Bis(melaminium) terephthalate dihydrate: a DFT computational study

The experimental and theoretical vibrational spectra of Bis(melaminium) terephthalate dihydrate were studied. The Fourier transform infrared (FT-IR) spectra of the Bis(melaminium) terephthalate dihydrate and its deuterated analogue were recorded in the solid phase. The molecular geometry and vibrational frequencies of Bis(melaminium) terephthalate dihydrate in the ground state have been calculated by using the density functional method (B3LYP) with 6-31++G(d,p) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The molecule contains the weak hydrogen bonds of N-H···O, N-H···N and O-H···O types, and those bonds are calculated with DFT method. In addition, molecular electrostatic potential, frontier molecular orbitals and natural bond orbital analysis of the title compound were investigated by theoretical calculations. The lack of the second harmonic generation (SHG) confirms the presence of macroscopic center of inversion.

Ethylenediammonium dication: H-bonded complexes with terephthalate, chloroacetate, phosphite, selenite and sulfamate anions. Detailed vibrational spectroscopic and theoretical studies of ethylenediammonium terephthalate

Crystalline complexes between ethylenediammonium dication and terephthalate, chloroacetate, phosphite, selenite and sulfamate anions were obtained by slow evaporation from water solution method. Room temperature powder infrared and Raman measurements were carried out. For ethylenediammonium terephthalate theoretical calculations of structure were performed by two ways: ab-initio HF and semiempirical PM3. In this case the PM3 method gave more accurate structure (closer to X-ray results). The additional PM3 calculations of vibrational spectra were performed. On the basis theoretical approach and earlier vibrational studies of similar compounds the vibrational assignments for observed bands have been proposed. All compounds were checked for second harmonic generation (SHG).

Co-adsorption and separation of CO2-CH4 mixtures in the highly flexible MIL-53(Cr) MOF

The present study attempts to understand the use of the flexible porous chromium terephthalate Cr(OH)(O(2)C-C(6)H(4)-CO(2)) denoted MIL-53(Cr) (MIL = Material from Institut Lavoisier) for the separation of mixtures of CO(2) and CH(4) at ambient temperature. The coadsorption of CO(2) and CH(4) was studied by a variety of different techniques. In situ synchrotron X-ray Powder Diffraction allowed study of the breathing of the solid upon adsorption of the gas mixtures and simultaneously measured Raman spectra yielded an estimation of the adsorbed quantities of CO(2) and CH(4), as well as a quantification of the fraction of the narrow pore (NP) and the large pore (LP) form of MIL-53. Quantitative coadsorption data were then measured by gravimetry and by breakthrough curves. In addition, computer simulation was performed to calculate the composition of the adsorbed phase in comparison with experimental equilibrium isotherms and breakthrough results. The body of results shows that the coadsorption of CO(2) and CH(4) leads to a similar breathing of MIL-53(Cr) as with pure CO(2). The breathing is mainly controlled by the partial pressure of CO(2), but increasing the CH(4) content progressively decreases the transformation of LP to NP. CH(4) seems to be excluded from the NP form, which is filled exclusively by CO(2) molecules. The consequences in terms of CO(2)/CH(4) selectivity and the possible use of MIL-53(Cr) in a PSA process are discussed.

Immobilization of lipases on hydrophobilized zirconia nanoparticles: highly enantioselective and reusable biocatalysts

Our study has demonstrated for the first time that zirconia nanoparticles modified by a simple carboxylic surfactant of a very long alkyl chain can significantly enhance the activity of the immobilized lipases for asymmetric synthesis in organic media. Zirconia nanoparticles of ca. 20 nm diameter were grafted with carboxylic surfactant modifiers from Tween 85 and erucic acid. The surface of nanoparticles was successfully changed from hydrophilic to hydrophobic. Lipases from Candida rugosa and Pseudomonas cepacia were immobilized on the modified zirconia nanoparticles by adsorption in aqueous solution. The immobilized lipases were used for the resolution of ( R, S)-ibuprofen and ( R, S)-1-phenylethanol through esterification and acylation, respectively, in isooctane organic solvent. When immobilized on erucic acid-modified zirconia, both lipases gave significantly higher activity and enantioselectivity compared with those from their corresponding crude lipase powders. The nanohybrid biocatalysts are stable and can be reused for eight cycles without loss in activity and selectivity. The interaction between the hydrophobic surface of zirconia support and lipases probably induces the conformational rearrangement of lipases into an active, stable form.

IR, Raman and SERS spectra of disodium terephthalate

The IR and Raman spectra of disodium terephthalate were recorded and analysed. Surface enhanced Raman scattering (SERS) spectrum was recorded in silver colloid. The vibrational wavenumber of the compound have been computed using the Hartree-Fock/6-31G* basis and compared with the experimental values. SERS studies suggest a flat orientation of the molecule at the metal surface.

Effect of pH on the Viscosity of Titanium Dioxide Aqueous Dispersions with Carboxylic Acids

Dispersions of titanium dioxide nanoparticles with terephthalic acid, isophthalic acid, salicylic acid, benzoic acid, and pyridine-2,5-dicarboxylic acid were prepared by aqueous grinding. The pH of the dispersions was adjusted by adding either HCl or NaOH, and the viscosity of the dispersions was measured. It was found that the viscosity of the system depends strongly on pH. The qualitative interpretation of the results based on the DLVO theory is presented. The evidence of the effect of bridging interactions on the viscosity of titanium dioxide-dicarboxylic acid dispersions is discussed.

Adsorption and self-assembly of aromatic carboxylic acids on Au/electrolyte interfaces

The adsorption and self-assembly of benzoic acid (BA), isophthalic acid (IA), and trimesic acid (TMA) on Au(111) single crystals and on Au(111-25 nm) quasi-single crystalline film electrodes have been investigated in 0.1 M HClO4 by combining in situ surface-enhanced infrared reflection absorption spectroscopy (SEIRAS) and scanning tunneling microscopy (STM) with cyclic voltammetry. All three acids are physisorbed on the electrode surface in a planar orientation at negative charge densities. Excursion to positive charge densities (or more positive potentials) causes an orientation change from planar to perpendicular. Chemisorbed structures are formed through the coordination of a deprotonated carboxyl group to the positively charged electrode surface. The three acid molecules assemble in different ordered patterns, which are controlled by pi-stacking (BA) or intermolecular hydrogen bonds between COOH groups (IA, TMA). A detailed analysis of the potential and time dependencies of the nu(C=O), nus(OCO), and nu(C-OH) vibration modes shows that the strength of lateral interactions increases upon chemisorption with an increasing number of COOH groups in the sequence of BA<IA<TMA. The vibration bands shift to higher wavenumbers due to dipole-dipole coupling, Stark tuning, and electron back donation from the electrode to COO-. In addition, an "indirect" electron donation to the COOH groups takes place via the conjugated molecular skeleton superimposed on the intermolecular hydrogen bonding.

Supramolecular nanostructures of 1,3,5-benzene-tricarboxylic acid at electrified Au(111)/0.05 M H2SO4 interfaces: an in situ scanning tunneling microscopy study

The potential-induced adsorption and self-assembly of 1,3,5-benzene-tricarboxylic acid (TMA) was investigated at the electrified Au(111)/0.05 M H2SO4 interface by in-situ scanning tunneling microscopy (STM) and surface enhanced infrared reflection absorption spectroscopy (SEIRAS) in combination with electrochemical techniques. Depending on the applied electric field, TMA forms five distinctly different, highly ordered supramolecular adlayers on Au(111) surfaces. We have elucidated their real-space structures at the molecular scale. In the potential range -0.25 V < E < 0.20 V, planar-oriented TMA molecules form a hexagonal open-ring honeycomb structure, Ia, a hydrogen-bonded ribbon-type phase, Ib, and a herringbone-type phase, Ic, stabilized by directional hydrogen bonding and weak substrate-adsorbate interactions. Interfacial water molecules are being replaced. In 0.20 V < or = E < 0.40 V, e.g., around the potential of zero charge, and at slightly higher coverages, a close-packed physisorbed adlayer of hydrogen-bonded TMA dimers, II, was observed. Further increase of the electrode potential to positive charge densities causes an orientation change from planar to upright. An initially disordered phase, IIIa, transforms into an ordered, stripelike chemisorbed adlayer, IIIb, of perpendicularly oriented TMA molecules. One carboxylate group per molecule is bound to the electrode surface, while the two other protonated carboxyl groups are directed toward the electrolyte and act as structure-determining components of a hydrogen-bonded two-dimensional ladder-type network. Structural transitions between the various types of ordered molecular adlayers are attributed to (hole) nucleation and growth processes.

Self-generation of tiered surfactant superstructures for one-pot synthesis of Co3O4 nanocubes and their close- and non-close-packed organizations

Self-generation of ionic organic capping from nonionic surfactant polyoxyethylene (20) sorbitan trioleate (Tween-85) has been realized for the controlled synthesis of single crystalline Co(3)O(4) quantum dots (3.0-5.7 nm) in cubic morphology from related layered hydroxide precursors at 80-95 degrees C. With chemical modification of hydrophobic functional groups on the surface of Co(3)O(4) nanocubes; furthermore, various nanocube-containing micellar superstructures can be further assembled through hydrophobic interactions between Tween-85 molecules and the surface coating under "one-pot" conditions. In particular, square arrangements, spherical domains, and line-assemblies of the prepared Co(3)O(4) nanocubes and their inter-transformations have been attained for the first time by manipulating intersurfactant-interactions. Hydrolysis of Tween-85 and the resultant tiered surfactant superstructures have been investigated with FTIR/UV-vis/EA/TGA/DTA/XPS methods, and the capping species has been identified to be alkylated oleic carboxylate anions derived from Tween-85. Pronounced quantum confinement effects have been observed with the prepared Co(3)O(4) nanocubes, and the optical band gap energies determined are 3.95 and 2.13 eV, respectively, for O(2-)--> Co(2+) and O(2-)--> Co(3+) charge-transfer processes.

In situ ATR-SEIRAS study of adsorption and phase formation of trimesic acid on Au(111-25 nm) film electrodes

The adsorption and phase formation of 3 mmol L–1 trimesic acid (TMA) on Au(111-25 nm) film electrodes in contact with aq. 0.1 mol L–1 HClO4 electrolyte have been investigated by in situ ATR-SEIRAS, cyclic voltammetry, chronoamperometry, and STM measurements. Depending on the applied electrode potential, TMA molecules assemble in three distinctly different 2D ordered adlayers. In the range 0.10 < E < 0.50 V, planar-oriented molecules form an open ring honeycomb pattern (phase I) stabilized by directional hydrogen bonds. Interfacial water molecules are being replaced. A close-packed, physisorbed adlayer II forms at higher potentials in the range 0.58 < E < 0.75 V. Further increase of the electrode potential causes an orientation change. An initially disordered phase transforms into an ordered, stripe-like chemisorbed adlayer III of perpendicularly oriented TMA molecules (0.90 < E < 1.20 V). One carboxylate group per molecule is bound to the electrode surface, while the two other protonated carboxyl groups are directed toward the electrolyte, and act as structure-determining components of a hydrogen-bonded molecular ladder network. Strongly hydrogen-bonded and isolated water species are co-adsorbed. The potential-induced formation of chemisorbed TMA proceeds in two steps: (i) orientation change from planar to a disordered tilted and (or) perpendicular phase IIIa (τ < 5 ms) according to a Langmuir-type kinetics; (ii) subsequently, the chemisorbed TMA molecules align into a highly ordered, stripe-like phase IIIb with co-adsorbed water species. Key words: ATR-SEIRAS, trimesic acid, Au(111), supramolecular assembly.

Fourier transform infrared and Raman spectra. Semi empirical AM1 and PM3; MP2/DZV and DFT/B3LYP-6-31G(d) ab initio calculations for dimethylterephthalate (DMT)

Fourier transform infrared and Raman spectra of dimethylterephthalate (DMT), as microcrystalline powder, have been investigated. The vibrational spectra were calculated using the AM1 and PM3 semi empirical procedures, and the Møller-Plesset (MP2/DZV), and the Becke-Lee, Yang and Parr gradient-corrected correlation functional: B3LYP/6-31G(d) ab initio calculations. On this basis, and assisted with the FT-IR and Raman spectra of the terephthalic acid, an assignment of the vibrational spectra of dimethylterephthalate was proposed. In the calculations, remarkable differences concerning the assignments of the vibrational spectra were noted between the AM1 and PM3 methods. Also, the ab initio procedure shows differences in interpreting the spectra compared with the semi empiric procedures, and among themselves. Calculated geometrical parameters were compared with the experimental values of dimethylterephthalate, diethylterephthalate and terephthalic acid.

Infrared spectra of phthalic acid, the hydrogen phthalate ion, and the phthalate ion in aqueous solution

The infrared spectra of a series of aqueous solutions containing phthalic acid (1,2-benzenedicarboxylic acid) and varying pH were examined using attenuated total reflection Fourier transform infrared spectroscopy and potentiometry. The basis spectra of phthalic acid, the hydrogen phthalate ion, and the phthalate ion were isolated using a factor analysis in which the absorbance of these species varies with pH and total phthalate concentration according to equilibrium and mass balance relations. Assignments of these basis spectra were made by comparison with spectra calculated ab initio. The conditional formation constants of phthalic acid and the hydrogen phthalate ion were determined at 25.0+/-0.1 degrees C in 0.6 M NaCl ionic media using infrared spectroscopy and in 1.5 M NaCl ionic media using both infrared spectroscopy and potentiometry.

Fourier transform infrared and raman spectra, vibrational assignment and ab initio calculations of terephthalic acid and related compounds

The Fourier transform infrared and Raman spectra of solid terephthalic acid, p-C6H4(COOH)2, have been recorded, and the Fourier transform Raman spectra for the terephthalate anion were measured. The wavenumbers for the band positions have been calculated in order to assign them. Moller-Plesset (MP2) and Density functional theory (DFT) calculations have been carried out with Huzinaga-Dunning basis sets (DZV). Also, a normal coordinate analysis through the Wilson-El'yashevich method was performed. The differences between the calculated ab initio spectra and the spectra of the solid phase have been interpreted with respect to the different C(2h) and C(i) local symmetry in the gas and in the solid phase, respectively, and considering also the formation of long-chains of terephthalic acid in the solid phase. In spite to the absence of experimental data for the cis conformation, calculations have been carried out and structural parameters and infrared intensities have been evaluated for the trans and cis conformations of terephthalic acid.