Journal of Chemical Sciences最新文献

Proton conductors play a significant role in various fields, and recent research has focused on exploring crystalline porous materials for their favourable proton-transport properties. However, synthesizing these materials often poses challenges, especially in achieving crystallinity. In this study, we have successfully developed an innovative approach by constructing an amorphous microporous polymer (AMP) structure. Unlike traditional methods that require crystallization, our AMP maintains a certain pore space, while avoiding the need for strict crystallinity. Remarkably, this newly developed AMP displays high-density sulphonic acid sites on its skeleton, enabling it to function as an efficient proton conductor across a wide range of relative humidity (RH) levels. At 70°C and 100% RH, it achieves an impressive maximum conductivity value of 3.34 × 10⁻³ S cm⁻¹. Such an excellent performance can be attributed to the low activation energy for proton conduction, measuring a mere 0.266 eV. This signifies a Grotthuss mechanism, indicating that protons readily jump along hydrogen bonds within the material.

Graphical abstract

Electric field experienced by a protic group depends primarily on solvent configuration and those configurations in which the electric field along the protic group exceeds a critical value, results in spontaneous proton transfer. Electronic structure calculations using density functional theory (DFT) result in artifacts in estimating critical electric fields for the spontaneous proton transfer process, often leading to bistable behaviour, in contrast to MP2 level calculations. Discrepancies in assessing critical electric fields using the DFT method can be attributed to the under-representation of Hartree–Fock exchange in many commonly used functionals, such as B3LYP and M06-2X, whose effect is precipitative in the proton transferred structures. Using the (critical) electric field values obtained by the MP2 level of theory as a benchmark, it is shown that the B3LYP functional altered to include 40% Hartree–Fock exchange, which omits the bistable behaviour and calculates reasonably accurate critical electric fields.

Graphical abstract

Accurate electrostatic description of proton transfer reactions can be accomplished by incorporating 40% Hartree–Fock exchange to the standard B3LYP functional.

Combination of organic donor–linker–acceptor dyes for panchromatic enhancement in photoelectrodes of dye-sensitized solar cells enables their environmentally friendly and cost-effective design. A promising combination in terms of spectral broadening and miscibility are the dyenamo red and blue dyes, which differ only in their molecular structure via linkers. In this work, we investigate the sequential co-sensitization of both dyes together with the co-adsorption of aggregation inhibitor, chenodeoxycholic acid to increase the optical absorption and energy conversion efficiency. Finally, with a J_SC of 10.2 mA cm⁻² and a V_OC of 584 mV, a small increase was achieved.

Graphical abstract

Combining Dyenamo Red and Blue dyes with chenodeoxycholic acid in dye-sensitized solar cells enhances optical absorption and energy efficiency. These combination enable cost-effective, environmentally friendly designs by broadening the spectral range and improving miscibility through sequential co-sensitization and co-adsorption techniques.

Use of magnesium oxide-coated magnetite nanoparticles (Fe₃O₄@MgO) as a heterogeneous base-catalyst in organic functional group transformations has been demonstrated. Catalytic efficiency of the Fe₃O₄@MgO platform as an inorganic base-catalyst was firstly explored in the oxidative hydroxylation of arylboronic acids in the presence of aq. H₂O₂, affording the corresponding phenols with outstanding effectiveness. In addition, the direct O-benzylation of phenols catalyszed by the Fe₃O₄@MgO platform, was efficiently conducted in an aqueous environment, resulting in the formation of benzyl phenyl ethers. Lastly, the hydration of benzonitriles was also achieved when the Fe₃O₄@MgO platform was employed under aqueous conditions, yielding the corresponding benzamides.

Graphic abstract

Magnesium oxide-coated magnetite nanoparticles (Fe O @MgO) were used as a base catalyst in organic transformations. It efficiently catalyzed the oxidative hydroxylation of arylboronic acids, O-benzylation of phenols, and hydration of benzonitriles in aqueous conditions, producing phenols, benzyl phenyl ethers, and benzamides, respectively.

Quick and robust analytical methods are of vital necessity in medicine and biology, making the synthesis of electroactive substrates for the sensing of medically relevant chemicals, a promising area of material science. Rare-earth cuprates, mostly famous for high-temperature superconductivity, continue to exhibit encouraging electroactivity towards surface selective oxidation of biologically active compounds. Samarium cuprate reported in this paper showed developed surface with unique porous morphology and good conductivity––a set of prerequisites for the sensing material. Further studies confirmed excellent samarium cuprate-based carbon paste-electrode sensitivity of enalapril maleate and helped to develop an analytical method with selectivity and stability applicable for wider use.

Graphical abstract

Sintering of equimolar amounts of copper and samarium oxides provides crystalline samarium cuprate at the temperature below its melting point. Obtained material has developed surface with micron-size pores. Further electrochemical studies as an additive in carbon paste, confirmed its excellent activity towards hypertension drug sensing.

(Note: See more examples of graphical abstracts on the journal website, http://www.ias.ac.in/chemsci/index.html under ‘submission information’.)

Geometries and binding energies of Be²⁺ ⋅ (CO)_1–3 complexes have been determined at the level of MP2/aug-cc-pVTZ method. Binding energy increases linearly with the number of CO molecules in these complexes. Our results show that the sequential bond dissociation energy follows the order: ({text{Be}}^{2+}cdot text{CO}) (>) ({text{Be}}^{2+}cdot {left(text{CO}right)}_{2}) (>{text{Be}}^{2+}cdot {left(text{CO}right)}_{3}). This trend was well-explained in terms of ion–quadrupole interaction fluctuations. Detailed bond analysis confirmed that the strength of interaction between Be ion and CO molecule decreases with the number of CO molecules in these complexes. Our calculations show that the strength of interaction with these complexes is highly dependent on the CO bond polarization and stabilization energy of these complexes.

Graphical abstract

The sequential bond energies of the Be²⁺ ·(CO)^1,2,3 complexes follow the trend: Be²⁺ ·(CO) > Be²⁺ ·(CO)₂ > Be²⁺ ·(CO)₃ . The primarycause of the variations observed in the ion-quadruple attraction forces in these complexes is the strength of the σ-donationbetween the Be cation and CO molecules. The ion-induced dipole interaction energy in these complexes is insignificant.

Solid-state anhydrous (QA) and hydrated quercetins (QH) were studied by using combustion calorimetry and thermal analysis-simultaneous thermogravimetry (TG) coupled with differential scanning calorimetry (DSC) methods. The enthalpies of formation were derived employing the experimental heat of combustion for the studied compounds. The obtained data are compared with estimated values using group additivity and quantum calculations. The correlation between experimental and calculated values is discussed considering the number and strength of intermolecular hydrogen bonds. From DSC experiments, the temperature ranges of dehydration followed by melting-decomposition were established.

Graphical abstract

The present study consists in bringing contributions to the completion of thermochemical data banks regarding the important role played by quercetin in the living organisms. The values of the thermodynamic quantities, which characterize the biochemical reactions, are put in correspondence with the biological activity of quercetin.

Synopsis The present study consists in bringing contributions to the completion of thermochemical data banks regarding the important role played by quercetin in the living organisms. The values of the thermodynamic quantities, which characterize the biochemical reactions, are put in correspondence with the biological activity of quercetin.

The advancement of the hydrogen economy worldwide has facilitated the production of hydrogen from various resources. The water-gas shift reaction (WGSR) serves as a critical intermediate step for hydrogen enrichment and CO reduction in syngas derived from carbon-based hydrogen production. This paper presents a numerical investigation into the kinetic modelling of high-temperature WGSR using an iron-based catalyst in a reactor equipped with a Ni membrane. The study employs the Podolski et al. kinetic model with a 93% Fe₂O₃/7% Cr₂O₃ catalyst to evaluate the impact of temperature and the CO/H₂O molar ratio on the overall reaction performance. Results indicate that an increase in temperature leads to a decrease in reactant conversion. To achieve optimal CO conversion and H₂ generation, a CO/H₂O molar input ratio of 1 is necessary. On the other hand, a microkinetic model for WGSR based on the formate mechanism over an iron-based catalyst is proposed. This comprehensive model includes seven adsorbed species and encompasses 18 elementary-step forward reactions. The developed model also enables the evaluation of temperature effects on surface coverage. Key intermediates identified in the model include OH* and HCOO* species. Additionally, it was determined that CO activation is more favorable at high temperatures.

Graphical abstract

The kinetic modelling of the high-temperature water-gas shift reaction (HT-WGSR) was explored for hydrogen production. The process utilized a hydrogen-selective Ni-dense membrane reactor combined with iron-based catalysts, aiming to enhance efficiency and optimize hydrogen separation. Various parameters, such as temperature and feed ratio, influencing reaction rates were also evaluated.

A safe method of producing pyrano[2,3-d]pyrimidine scaffolds without the need for a catalyst is shown, utilizing the concepts of green chemistry. This is achieved by employing polyfluorinated alcohol as a reusable medium and mixing barbituric acid/1,3-dimethylbarbituric acid, malononitrile and aryl aldehydes in an environmentally friendly manner. This environmentally friendly method uses one pot, readily accessible, low-cost reaction media, safe reaction conditions, no requirement for column chromatography for separation and effective use of resources. Furthermore, green 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) did not require significant modifications and remained stable for four reuses. This is highly helpful in satisfying industrial demands and resolving environmental issues.

Graphical abstract

Our study shows that 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) is used as a reusable medium to synthesize pyrano[2,3-d]pyrimidine frameworks without the need for a catalyst. This eco-friendly, cost-effective and straightforward solution has several benefits. It employs readily accessible materials, reduces the need for costly and dangerous chemicals, saves time and yields high-quality results.

Charge transfer complexes including [HBT] and [FBT], 4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile with picric acid, and 2,4-dinitrophenol were synthesized by FTIR and 1H NMR. The full geometrical optimization, frontier molecular orbitals energies, energy gap, chemical reactivity indices, MEP maps, thermodynamic properties, the vibrational spectra, and partial density of states have been investigated at the DFT level (B3LYP) using the basis set SDD (Stuttgart/Dresden ECP plus DZ). Using the investigated computational analysis, it was concluded that the existence of H-bond beside charge transfer interaction is certainly responsible for the high stability of the formed CT complexes. The decrement of the HOMO-LUMO energy gap, a quantum chemical descriptor, explains the ease with which charge transfer interactions take place within the molecule. NBO explains the eventual hyper-conjugative interaction and charge delocalization that take place within the CT complexes and are responsible for the high optical nonlinearity of the HBT-PA, HBT-DNP, FBT-PA, and FBT-DNP complexes. NMR spectra reconfirmed the formation of the new compound, including both charge and hydrogen bonding. The nonlinear optical property and total dipole moment of the CT complexes reveal that the CT complexes could be a suitable candidate for nonlinear optical applications in optoelectronic devices.

Graphical abstract

The synthesized charge transfer complexes (HBT-PA, HBT-DNP, FBT-PA, and FBT-DNP) were characterized by FTIR, NMR, and DFT methods (B3LYP/SDD). Geometrical optimization, HOMO-LUMO energy gap, chemical reactivity, and NBO analysis confirmed charge transfer interactions and hydrogen bonding, enhancing optical nonlinearity. These complexes are promising for optoelectronic applications.