Solution Chemistry

Solution chemistry explores the behaviour of substances when dispersed at the molecular or ionic level within a solvent, most commonly water but also including organic and designer media. Central themes include the mechanisms by which solute–solvent interactions govern solubility, reaction kinetics and phase equilibria. Ionic solvation underpins processes ranging from electrochemistry and biological ion transport to materials self-assembly, while molecular solvents direct reaction pathways through polarity, hydrogen bonding and dispersion forces. Advances in spectroscopic, scattering and computational methods have revealed the subtle balance of enthalpic and entropic contributions that control dissolution, complex formation and aggregation phenomena. From dilute electrolytes to concentrated deep eutectic mixtures, solution chemistry links fundamental thermodynamics with applications in catalysis, separations, energy storage and biomolecular function. The field continues to evolve through integration of ultrafast dynamics, machine-learning-aided design and in situ characterisation techniques, offering routes to tailor solvent environments and optimise processes across the chemical and life sciences.

Research from Nature Portfolio

A first-of-its-kind study has directly characterised an aqueous promethium complex, capturing the coordination geometry and bond lengths of this elusive lanthanide in water. By stabilising the radioactive Pm³⁺ ion with a bespoke diglycolamide ligand, researchers obtained synchrotron X-ray absorption data that experimentally trace the lanthanide contraction across the series, informing selective separation strategies.

Two-dimensional infrared–Raman spectroscopy has been harnessed to probe water’s hydrogen-bond network, revealing clear cross-peaks that report on the coupling of low-frequency collective modes with high-frequency O–H stretches. Theory–simulation-guided decomposition of the multidimensional signals establishes direct links between spectral features and tetrahedral order, opening new avenues to monitor liquid structure under varying thermodynamic conditions.

Machine-learning models have achieved sub-percent-level accuracy in predicting densities of deep eutectic solvents, leveraging support-vector regression trained on critical properties and composition. This cheminformatics-driven framework extends reliable property estimation to novel eutectic mixtures without extensive experimentation, accelerating the rational design of sustainable solvent systems.

Research from all publishers

Anharmonic vibrational calculations combined with quasi-classical trajectories have refined the assignment of the gas-phase water octamer spectrum in the OH-stretch region. The work demonstrates that only a limited set of low-energy conformers is needed to account for experimental features, advancing our understanding of cooperative hydrogen-bond dynamics in nanoscale clusters.

A comprehensive spectroscopic and structural survey of dilute lanthanide nitrate solutions has mapped the contraction of the first hydration shell from cerium to lutetium. By integrating X-ray diffraction, infrared and extended X-ray absorption fine-structure measurements, investigators connected changes in ion–water coordination and nitrate binding modes to emerging antimicrobial activity, suggesting novel applications of f-block aqua ions in biocidal formulations.

A comparative study of spectral approaches for non-fluorescent charge-transfer systems has introduced corrected modelling schemes that incorporate hydrogen-bonding effects. By benchmarking two solvatochromic methodologies across diverse solvents, the work delivers more accurate excited-state dipole moments and exploits strong spectral shifts to classify solvent polarity and hydrogen-bonding propensity.

Solution Chemistry publication trend

The graph below shows the total number of articles in solution chemistry across all publications each year (not limited to Nature Index journals).

Technical terms

Ion solvation: The stabilisation of an ion by a surrounding shell of solvent molecules through ion–dipole interactions.

Deep eutectic solvent: A eutectic mixture of hydrogen-bond donor and acceptor that remains liquid well below the melting points of its individual components.

Lanthanide contraction: The systematic decrease in ionic radii across the lanthanide series owing to poor shielding of nuclear charge by 4f electrons.

Tetrahedral order: A local structural motif in water in which a molecule is hydrogen-bonded to four neighbours in an approximately tetrahedral geometry.

Anharmonicity: Non-ideal behaviour of vibrational modes that deviates from the simple harmonic approximation, critical for accurate infrared spectra.

Cheminformatics: The application of data-driven and machine-learning techniques to predict chemical and physical properties from molecular structure.

Two-dimensional spectroscopy: Nonlinear optical methods that correlate sequential interactions with different frequency fields to reveal mode coupling in complex systems.

Support-vector regression: A supervised machine-learning algorithm for regression tasks that finds a function by minimising error within a defined tolerance.

References

1. Observation of a promethium complex in solution. Nature (2024).
2. Two-dimensional infrared-Raman spectroscopy as a probe of water’s tetrahedrality. Nature Communications (2023).
3. Density of Deep Eutectic Solvents: The Path Forward Cheminformatics-Driven Reliable Predictions for Mixtures. Molecules (2021).
4. Anharmonic Assignment of the Water Octamer Spectrum in the OH Stretch Region. The Journal of Physical Chemistry A (2023).
5. Physicochemical Characterization and Antimicrobial Properties of Lanthanide Nitrates in Dilute Aqueous Solutions. Molecules (2024).
6. Comparative Study of Two Spectral Methods for Estimating the Excited State Dipole Moment of Non-Fluorescent Molecules. Molecules (2024).