Isotopic studies are gaining much interest in heritage science, as they can provide insight into a material's age and provenance. Radiocarbon (¹⁴C) dating affords a time frame for the materials being studied, thus providing a historical context, whereas the specific pattern of lead isotope ratios may be used to set geographical constraints on the source of the original materials. Both methods require invasive sampling from the object, and henceforth limits their respective application. With the focus on lead white paint (2PbCO₃·Pb(OH)₂), in this study we extract the time of production of the pigment from the carbonate anion by radiocarbon dating while its origin is traced by lead isotope analysis on the cation. The methodology was applied to 12 British and 8 Swiss paintings from the 18^th to 20^th century, with known dates and provenance. The ¹⁴C analysis of the lead white in combination with the organic binder and canvas alone places all objects between the 17^th and 20^th centuries, which is in agreement with their signed date, wheras the lead isotope analysis of all samples are consistent with lead ores from European deposits. In most of the cases the combined results are consistent with the art historical data and prove that isotope analysis is intrinsic to the object. This feasibility study conducted on paintings of known age demonstrates the possibility to maximize the information output from lead white paint, thus increasing the benefits of a single sampling.

The synthesis, isolation and full characterization of ion pairs between alkaline metal ions (Li⁺, Na⁺, K⁺) and mono-anions and dianions obtained from 5H-dibenzo[a,d]cycloheptenyl (C₁₅H₁₁ = trop) is reported. According to Nuclear Magnetic Resonance (NMR) spectroscopy, single crystal X-ray analysis and Density Functional Theory (DFT) calculations, the trop^‒ and trop^2−• anions show anti-aromatic properties which are dependent on the counter cation M⁺ and solvent molecules serving as co-ligands. For comparison, the disodium and dipotassium salt of the dianion of dibenzo[a,e]cyclooctatetraene (C₁₆H₁₂ = dbcot) were prepared, which show classical aromatic character. A d⁸-Rh(I) complex of trop⁻ was prepared and the structure shows a distortion of the C₁₅H₁₁ ligand into a conjugated 10π -benzo pentadienide unit—to which the Rh(I) center is coordinated—and an aromatic 6π electron benzo group which is non-coordinated. Electron transfer reactions between neutral and anionic trop and dbcot species show that the anti-aromatic compounds obtained from trop are significantly stronger reductants.

In 2016, five fragments from a copy of “The Great Holy Family of Francis I” were brought to the Cologne Institute of Conservation Sciences (CICS) for research and conserva-tion/restoration. A comprehensive technical and material analysis was carried out to as-sist provenance studies. From the analysis of pigments, binder, additives, and canvas fi-bres alongside radiocarbon dating of the lead white pigment, oil binder, and canvas sup-port, as well as the lead stable isotope study, it could be determined that, with high proba-bility, the copy was created in Northern Europe between the late 16th century and the mid-17th century. During this period the original painting was initially displayed in Fon-tainebleau in the “Chapelle Haute” before being transferred in the early 17th century to the newly built “Cabinet des Peintures”, also in Fontainebleau, where it would probably have been more accessible for copying. Interestingly, the written sources describe a copy made during this period to replace the original in the “Chapelle Haute”, the location of which is currently not known. However, the different overall dimensions of the present copy speak against it, having been created to replace the original.