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Long-chain mercury carboxylates relevant to saponification in oil and tempera paintings: XRPD and ssNMR complementary study of their crystal structures
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SYSNO ASEP 0554813 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Long-chain mercury carboxylates relevant to saponification in oil and tempera paintings: XRPD and ssNMR complementary study of their crystal structures Author(s) Barannikov, Ruslan (UACH-T) RID, SAI
Kočí, Eva (UACH-T) SAI, RID
Bezdička, Petr (UACH-T) SAI, RID, ORCID
Kobera, Libor (UMCH-V) RID, ORCID
Mahun, Andrii (UMCH-V) ORCID
Rohlíček, Jan (FZU-D) RID, ORCID
Plocek, Jiří (UACH-T) RID, ORCID, SAI
Švarcová, Silvie (UACH-T) SAI, RID, ORCIDNumber of authors 8 Source Title Dalton Transactions. - : Royal Society of Chemistry - ISSN 1477-9226
Roč. 51, č. 10 (2022), s. 4019-4032Number of pages 14 s. Language eng - English Country GB - United Kingdom Keywords cross-polarization ; adiabatic pulses ; thermal-behavior ; chemical-shift ; metal soaps ; NMR Subject RIV CA - Inorganic Chemistry OECD category Inorganic and nuclear chemistry Subject RIV - cooperation Institute of Macromolecular Chemistry - Macromolecular Chemistry
Institute of Physics - Solid Matter Physics ; MagnetismR&D Projects LM2018124 GA MŠMT - Ministry of Education, Youth and Sports (MEYS) GA19-05259S GA ČR - Czech Science Foundation (CSF) Method of publishing Limited access Institutional support UACH-T - RVO:61388980 ; UMCH-V - RVO:61389013 ; FZU-D - RVO:68378271 UT WOS 000756793200001 EID SCOPUS 85125965108 DOI 10.1039/d1dt04160f Annotation Saponification, resulting from pigment-binder interactions, is one of the most endangering phenomena affecting the appearance and stability of painted works of art. The crystallization of metal carboxylates (soaps) in paint layers is recently assumed as the most critical point for the development of undesirable changes induced by saponification, however, the factors triggering it are not fully understood. The red pigment cinnabar (HgS) has been suspected of contributing to saponification, however, the paucity of reliable reference structural data limited the experimental research of its effect at the molecular level. Within this study we synthesized mercury(ii) carboxylates of the formula Hg(C16)(x)(C18)(2-x) (x = 0.0, 0.2, 0.5, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0) where C16 and C18 are hexadecanoate (palmitate) and octadecanoate (stearate), respectively, and characterize them by combination of X-ray powder diffraction (XRPD) and C-13 and Hg-199 solid state NMR (ssNMR). For a more detailed interpretation of their structural and thermal behavior, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used. The crystal structure of the studied mercury carboxylates was described on the basis of complementary ssNMR and XRPD measurements, Rietveld refinement and DFT calculations. All the subjected compounds crystallize in a monoclinic lattice of the C2/c symmetry. Mercury atoms are arranged in a slightly distorted square antiprismatic geometry and are monodentatically bonded to carboxylate anions. The structural disorder at the aliphatic end of the stearic acid chains was detected in the mixed carboxylates. Within the paper, the structural (dis)similarity with the corresponding lead carboxylates is discussed. The synthesized and characterized mercury carboxylates were applied to describe neo-formed mercury soaps in a model experiment simulating an egg-based paint system. Workplace Institute of Inorganic Chemistry Contact Jana Kroneislová, krone@iic.cas.cz, Tel.: 311 236 931 Year of Publishing 2023 Electronic address https://doi.org/10.1039/D1DT04160F
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