Multiparameter High-Throughput and in Situ X-ray Diffraction Study of Six New Bismuth Sulfonatocarboxylates: Discovery, Phase Transformation, and Reaction Trends

With the employment of high-throughput methods, the system Bi$^{3+}$/4,8-disulfonyl-2,6-naphthalenedicarboxylic acid (H$_4$DSNDC)/H$_2$O/additive (HNO$_3$ or NaOH) was systematically investigated under hydrothermal reaction conditions. The influence of the molar ratio of the starting materials, pH, and reaction temperature and time was investigated in more than 500 reactions. The product formation is highly sensitive toward small changes of the synthesis parameters, but six new bismuth sulfonatocarboxylates were reproducibly obtained starting from clear solutions of the reactants. All compounds were structurally characterized from single-crystal X-ray diffraction data. Fully deprotonated linker ions are found in [Bi$_6$O$_6$(OH)$_2$(H$_2$O)$_4$(DSNDC)] (1), [Bi$_2$(OH)$_2$(DSNDC)] (2), [Bi$_8$O$_7$(OH)$_2$(H$_2$O)$_2$(DSNDC)$_2$] (3), and [Bi$_7$O$_5$(OH)$_3$(H$_2$O)$_4$(DSNDC)$_2$]·4H$_2$O (4), while the presence of larger amounts of acid or short reaction times leads to compounds with noncoordinating −COOH groups, [Bi$_2$(OH)$_2$(H$_2$O)$_2$(DSNDC)(H$_2$DSNDC)] (5) and [Bi$_6$O$_4$(OH)$_4$(H$_2$O)$_{12}$(H$_2$DSNDC)$_3$]·xH$_2$O (6), respectively. The inorganic building units (IBUs) in all six structures differ substantially from each other; the IBUs found in 2 ({Bi$_2$(OH)$_2$}), 5 (BiO$_8$ polyhedron), and 6 ({Bi$_6$O$_4$(OH)$_4$} cluster) have been reported in the literature, while new IBUs are observed for 1 (chains of composition {Bi$_3$O$_3$(OH)}$_∞$), 3 ({Bi$_{16}$O$_{14}$(OH)$_4$} cluster), and 4 ({Bi$_7$O$_5$(OH)$_3$} cluster). Systematic variation of the reaction temperature and time indicated their distinct influence on product formation. Hence, in situ powder X-ray diffraction measurements at Deutsches Elektronen-Synchrotron, Hamburg, Germany, employing synchrotron radiation were carried out. In all studied in situ reactions, compound 6 is first observed and subsequently transformed to 1, 2, 4, and 5, depending on the reaction time and temperature as well as concentration of the starting materials