The liquid structure of the solvents dimethylformamide (DMF) and dimethylacetamide (DMA)

Exploring solubility and energetics: Dissolution of biologically important l-threonine in diverse aqueous organic mixtures across the temperature range of 288.15 K to 308.15 K

This research provides a thorough investigation into the solubility behavior and solution thermodynamics of l-threonine in significant organic solvent systems. The work was done on measuring the actual solubility and subsequently calculating overall transfer solvation free energetics (∆Genergetic0i) and transfer entropies (∆St0i) at a temperature of 298.15 K. These measurements were performed as l-threonine transitioned from water to different water-organic mixed solvents systems. The saturated solubilities of l-threonine were determined using the 'gravimetric method' at five equidistant temperatures namely 288.15 K, 293.15 K, 298.15 K, 303.15 K and 308.15 K. By analyzing the data on solubility, we further obtained the different energies involved in solvation related issues. In the case of single solvents, the nature of solubility of l-threonine was observed like: dimethylsulfoxide (DMSO) < acetonitrile (ACN) < N, N-dimethylformamide (DMF) < ethylene glycol (EG) < water (H2O), irrespective of the experimental conditions. Specifically, at 298.15 K, the solubilities of l-threonine in single solvents were found to be as follows: 0.8220 mol per kg of water, 0.3101 mol per kg of EG, 0.1337 mol per kg of DMF, 0.1107 mol per kg DMSO and 0.1188 mol per kg of ACN. This research critically examines the relationship between the experimental saturated solubility of l-threonine and the complex properties influencing its solvation energy in diverse aqueous organic solvent systems.

Thermodynamic Study of N-Methylformamide and N,N-Dimethyl-Formamide

An extensive thermodynamic study of N-methylformamide (CAS RN: 123-39-7) and N,N-dimethylformamide (CAS RN: 68-12-2), is presented in this work. The liquid heat capacities of N-methylformamide were measured by Tian-Calvet calorimetry in the temperature interval (250-300) K. The vapor pressures for N-methylformamide and N,N-dimethylformamide were measured using static method in the temperature range 238 K to 308 K. The ideal-gas thermodynamic properties were calculated using a combination of the density functional theory (DFT) and statistical thermodynamics. A consistent thermodynamic description was developed using the method of simultaneous correlation, where the experimental and selected literature data for vapor pressures, vaporization enthalpies, and liquid phase heat capacities and the calculated ideal-gas heat capacities were treated together to ensure overall thermodynamic consistency of the results. The resulting vapor pressure equation is valid from the triple point to the normal boiling point temperature.

The local ordering of polar solvents around crystalline carbon nitride nanosheets in solution

The crystalline graphitic carbon nitride, poly-triazine imide (PTI) is highly unusual among layered materials since it is spontaneously soluble in aprotic, polar solvents including dimethylformamide (DMF). The PTI material consists of layers of carbon nitride intercalated with LiBr. When dissolved, the resulting solutions consist of dissolved, luminescent single to multilayer nanosheets of around 60-125 nm in diameter and Li+ and Br- ions originating from the intercalating salt. To understand this unique solubility, the structure of these solutions has been investigated by high-energy X-ray and neutron diffraction. Although the diffraction patterns are dominated by inter-solvent correlations there are clear differences between the X-ray diffraction data of the PTI solution and the solvent in the 4-6 Å-1 range, with real space differences persisting to at least 10 Å. Structural modelling using both neutron and X-ray datasets as a constraint reveal the formation of distinct, dense solvation shells surrounding the nanoparticles with a layer of Br-close to the PTI-solvent interface. This solvent ordering provides a configuration that is energetically favourable underpinning thermodynamically driven PTI dissolution. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'.

Manipulating Nucleation and Crystal Growth of Inorganic Perovskite Solar Cells

Inorganic metal halide perovskite materials as sunlight absorbers for solar cells exhibit better thermal stability than organic-inorganic hybrid counterparts. Pure cesium lead triiodide (CsPbI3), with the most suitable band gap, suffers phase instability under an ambient environment. Nucleation and crystal growth are two crucial steps in fabricating a solution-processed perovskite film. A high-quality perovskite film with good morphology makes a significant impact on the efficiency and stability of perovskite solar cells. Dimethylformamide (DMF) is a commonly used aprotic solvent. However, it is difficult to obtain a high-quality inorganic perovskite film using DMF as a single solvent due to its slow evaporation and strong coordination with Pb2+. Here, we investigate dimethylacetamide (DMAc)/DMF as a cosolvent to prompt nucleation during the spin-coating process, leading to higher nucleation density and better surface coverage. In addition, we introduce CsBr in dimethylammonium lead triiodide (DMAPbI3)/CsI precursors to slow down the crystal growth process. CsBr does not increase the film band gap but leads to a pinhole-free film with better crystallinity. Through nucleation and crystal growth engineering, the power conversion efficiency of inorganic perovskite devices is improved to 17.67%, and ambient environment stability is significantly enhanced.

Weak Interactions in Dimethyl Sulfoxide (DMSO)-Tertiary Amide Solutions: The Versatility of DMSO as a Solvent

The structures of equimolar mixtures of the commonly used polar aprotic solvents dimethylformamide (DMF) and dimethylacetamide (DMAc) in dimethyl sulfoxide (DMSO) have been investigated via neutron diffraction augmented by extensive hydrogen/deuterium isotopic substitution. Detailed 3-dimensional structural models of these solutions have been derived from the neutron data via Empirical Potential Structure Refinement (EPSR). The intermolecular center-of-mass (CoM) distributions show that the first coordination shell of the amides comprises ∼13-14 neighbors, of which approximately half are DMSO. In spite of this near ideal coordination shell mixing, the changes to the amide-amide structure are found to be relatively subtle when compared to the pure liquids. Analysis of specific intermolecular atom-atom correlations allows quantitative interpretation of the competition between weak interactions in the solution. We find a hierarchy of formic and methyl C-H···O hydrogen bonds forms the dominant local motifs, with peak positions in the range of 2.5-3.0 Å. We also observe a rich variety of steric and dispersion interactions, including those involving the O═C-N amide π-backbones. This detailed insight into the structural landscape of these important liquids demonstrates the versatility of DMSO as a solvent and the remarkable sensitivity of neutron diffraction, which is critical for understanding weak intermolecular interactions at the nanoscale and thereby tailoring solvent properties to specific applications.

Synthetic approaches for accessing rare-earth analogues of UiO-66

Rare-earth (RE) analogues of UiO-66 with non-functionalised 1,4-benzenedicarboxylate linkers are synthesised for the first time, and a series of synthetic approaches is provided to troubleshoot the synthesis. RE-UiO-66 analogues are fully characterised, and demonstrate a high degree of crystallinity, high surface area and thermal stability, consistent with the UiO-66 archetype.

Infrared spectroscopic and computational studies of Co(ClO4)2 dissolved in N,N-dimethylformamide (DMF). Vibrations of DMF influenced by Co2+ or ClO4- or both

Infrared (IR) spectroscopy for N,N-dimethylformamide (DMF) shows that the OCN bend (δ_OCN) and the CO stretch (ν_CO) vibrations undergo an upshift and a downshift, respectively, on the dissolution of Co(ClO₄)₂. Quantum chemical calculations are performed for optimizing the structures and predicting the IR spectra of model complexes for solute species. The calculations reveal that Co²⁺ exerts a much larger influence than ClO₄^- on the vibrations of DMF. For Co²⁺(DMF)₆, in which each DMF molecule is coordinated to Co²⁺ via the O atom, the Co²⁺⋯DMF interaction upshifts the δ_OCN frequencies (+24 cm^-1 on average) while the dipole coupling gives rise to splitting (12 cm^-1) of the modes. On the other hand, the Co²⁺⋯DMF interaction downshifts the ν_CO frequencies (-15 cm^-1 on average) while the splitting of the modes amounts to 37 cm^-1. As a result, one of the ν_CO modes is located at an upshifted position (+13 cm^-1) despite the O-atom coordination. For six-coordinated isomers of Co²⁺(DMF)₇, the δ_OCN and ν_CO frequencies of the second-sphere DMF are close to those of bulk DMF in neat liquid. The calculations indicate that it is difficult to prove or exclude the formation of contact ion pairs [Co(DMF)₅ClO₄]⁺ and solvent-shared ion pairs [Co(DMF)₆ClO₄]⁺ by IR spectroscopy in the δ_OCN and ν_CO regions. However, asymmetric ClO stretches of the ClO₄^- moiety suggest that conceivable is the coexistence of solvent-shared ion pairs only.