A new small molecule gelator and 3D framework ligator of lead(ii)

Abstract

Reacting equimolar quantities of 5-allenyl-1,3-benzenedicarboxylic acid (H2abd) with lead(II) acetate trihydrate in N,N-dimethylformamide (DMF) under solvothermal conditions results in formation of a metallogel with a critical gelation percentage of 1% w/v. Elemental analysis performed on the gel provided a molecular composition ratio of [Pb(abd)(H2O)]n (1). Viewing the gel by scanning electron microscopy (SEM) identified an entangled network of cross-linked nano-fibres. 1 H-NMR aliquots of hydrated lead(II) acetate added to a solution of H2abd in deuterated DMF allow inferences to be made about solution-state behaviour that occurs during the initial gel aggregation stage. Under nonsolvothermal conditions, combining H2abd and hydrated lead(II) acetate resulted in formation of single crystals suitable for X-ray diffraction, which were identified as a 3D coordination polymer with composition [Pb(abd)(DMF)] (2). Structural features observed within this 3D coordination polymer provide the basis for assigning the molecular structure to the fibrils present within gel 1. This assertion is supported by comparable vibrational profiles taken from a sample of dried gel 1 to that of crystalline 2, and the matching of early solution-state 1 H-NMR spectroscopic trends to later solid-state observations.A new allene dicarboxylate ligand reacts with hydrated lead(II) acetate in DMF to yield either a crystalline 3D framework or a metallogel dependent on the reaction temperature.

Shedding Light on Functional Hybrid Nanocomposites 19th Century Paint Medium

“…It can be stressed that, as lead oxide particles are semiconductors (band gap of 2.6-2.7 eV) and therefore photocatalysts, they may create holes and precursor electrons of radical species in the presence of visible light. It is also quite possible that these radicals (observed in previous EPR experiments [4] ) contribute to the polymerisation processes of certain double bonds present in the varnish components and observed by 13 C-NMR.…”

“…Micron-sized hydrated lead acetate precursors, carboxylated triterpenes, solvent (turpentine, i.e., mainly monoterpenes), and poly-beta-myrcene oligomers are mixed mechanically. FTIR-ATR and 13 C-NMR demonstrated the interaction of the lead compound and the carboxylic acid moieties of the triterpenoids, by the formation of resinate bands in FTIR (1500-1600 cm −1 ) and of a new chemical environment in the acidic carbon region in NMR (≈180 ppm). The coordination between lead cations and carboxylic acid functions of the triterpenoids drives the dissolution of the lead precursors in the organic mixture, and the subsequent formation of lamellar triterpenoids metallogels such as the more studied sterol metallogels based on lithocholates in presence of Pb or Cu ions, [11] that display continuous lamellar structures.…”

“…Micron-sized hydrated lead acetate precursors, carboxylated triterpenes, solvent (turpentine i.e., mainly monoterpenes) and poly-beta-myrcene oligomers are mixed manually and mechanically. FTIR-ATR and 13 C-NMR demonstrated the interaction of the lead compound and the carboxylic acid moieties of the triterpenoids, by the formation of resinate bands in FTIR (1500-1600 cm -1 ) and of a new chemical environment in the acidic carbon region in NMR (ca. 180 ppm).…”

“…To investigate possible complementary reactions, we also monitored the proportion of CC in the gel and the "OA + turpentine" mixture, by integration of the concerned peaks [25] of the 13 C NMR spectra: the ratio CC /C aliphatic decreases slightly in the gel (≈17% in the varnish and only 12% in the gel, calculated from the spectra Figure S3, Supporting Information). 207 Pb-NMR experiments were carried out to investigate the local environment of Pb in the gels and clarify the coordination of Pb in the complex (Pb (II) has a very flexible coordination sphere, since it is known to exhibit a coordination number ranging from 3 to 12).…”

“…To investigate possible complementary reactions, we also monitored the proportion of C=C in the gel and the "OA + turpentine" mixture, by integration of the concerned peaks [25] of the 13 C RMN spectra: the ratio C=C /C aliphatic decreases slightly in the gel (ca. 17% in the varnish and only 12% in the gel, calculated from the spectra figure S3).…”