The formation of metal soaps (metal complexes of saturated fatty acids) is a serious problem affecting the appearance and structural integrity of many oil paintings. Tailored model systems for aged oil paint and time‐dependent attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy were used to study the diffusion of palmitic acid and subsequent metal soap crystallization. The simultaneous presence of free saturated fatty acids and polymer‐bound metal carboxylates leads to rapid metal soap crystallization, following a complex mechanism that involves both acid and metal diffusion. Solvent flow, water, and pigments all enhance metal soap crystallization in the model systems. These results contribute to the development of paint cleaning strategies, a better understanding of oil paint degradation, and highlight the potential of time‐dependent ATR‐FTIR spectroscopy for studying dynamic processes in polymer films.

The molecular structure around metal ions in polymer materials has puzzled researchers for decades. This question has acquired new relevance with the discovery that aged oil paint binders can adopt an ionomer structure when metal ions leached from pigments bind to carboxylate groups on the polymerized oil network. The characteristics of the metal-polymer structure are expected to have important consequences for the rate of oil paint degradation reactions such as metal soap formation and oil hydrolysis. Here, we use two-dimensional infrared (2D-IR) spectroscopy to demonstrate that zinc carboxylates formed in paint films containing zinc white pigment adopt either a coordination chain– or an oxo-type cluster structure. Moreover, it was found that the presence of water governs the relative concentration of these two types of zinc carboxylate coordination. The results pave the way for a molecular approach to paintings conservation and the application of 2D-IR spectroscopy to the study of polymer structure.

We show that the VCD signal intensities of amino acids and oligopeptides can be enhanced by up to 2 orders of magnitude by coupling them to a paramagnetic metal ion. If the redox state of the metal ion is changed from paramagnetic to diamagnetic the VCD amplification vanishes completely. From this observation and from complementary quantum-chemical calculations we conclude that the observed VCD amplification finds its origin in vibronic coupling with low-lying electronic states. We find that the enhancement factor is strongly mode dependent and that it is determined by the distance between the oscillator and the paramagnetic metal ion. This localized character of the VCD amplification provides a unique tool to specifically probe the local structure surrounding a paramagnetic ion and to zoom in on such local structure within larger biomolecular systems.