Hydrates and polymorphs of lead squarate Pb(C4O4): Structural transformations studied by in situ X-ray powder diffraction and solid state NMR

Abstract

Considering the low dimensionality of the crystal structure of the known lead squarate tetrahydrate, Pb(C 4 O 4 ).4H 2 O, the thermal reactivity of the powdered compound and structural studies of lower hydrates have been investigated from X-ray single-crystal and powder diffraction data, solid state NMR and thermal analyses. It is shown that Pb(H 2 O)(C 4 O 4 ) and two polymorphs of anhydrous PbC 4 O 4 can be formed within different conditions. Crystal data of the new phases are: Pb(H 2 O)(C 4 O 4 ) (1), S.G. P2 1 /c, a = 7.3650(5) Å, b = 11.302(1) Å, c = 6.6822(4) Å, β= 102.501(6)°, Z = 4; PbC 4 O 4 (2), orthorhombic crystal system, a = 24.276(6) Å, b = 15.261(3) Å, c = 7.850(2) Å, Z = 4; PbC 4 O 4 (3), S.G. I4/mcm, a = 6.1640(2) Å, c = 12.0526(8) Å, Z = 4. The departure of the water molecules leads to the condensation of initial inorganic chains into 2D or 3D-type crystal structures. The full decomposition of the squarate ligand provides successive lead oxides.

A Semiconducting Bi2O2(C4O4) Coordination Polymer Showing a Photoelectric Response

“…For instance, Wu et al assumed that distorted BiO7E coordination induces local dipoles, facilitating the charge separation process (49). Curiously, Sn2O(C4O4)(H2O) geometry is affected by stereo-active lone pair of Sn 2+ ,(50) while for Pb(H2O)(C4O4) the closest sphere of Pb 2+ is (51). Further insight into the structural details are revealed using FTIR and Raman spectroscopies (Figure 4).…”

“…For instance, Wu et al assumed that distorted BiO 7 E coordination induces local dipoles, facilitating the charge-separation process . Curiously, the Sn 2 O­(C 4 O 4 )­(H 2 O) geometry is affected by the stereoactive lone pair of Sn 2+ , while for Pb­(H 2 O)­(C 4 O 4 ), the closest sphere of Pb 2+ is compactly populated with bridging water molecules and mono- and bidentately coordinated ligands …”

“…54 Sn 2+ , 55 while for Pb(H 2 O)(C 4 O 4 ), the closest sphere of Pb 2+ is compactly populated with bridging water molecules and monoand bidentately coordinated ligands. 56 Further insight into the structural details is revealed using FTIR and Raman spectroscopies (Figure 4). Typically, the vibrational mode bias registered with IR spectroscopy is ∼4 cm −1 (5 × 10 −4 eV), sufficiently small to give changes in the local geometries of the molecular fragments.…”

Resolvable polymorphism in an intergrowth of two modifications of tris(diethyldithiocarbamato)antimony

“…The neighbour diagonally down the Periodic Table, lead(II), also furnishes sparse cases of polymorphism: lead acetate (Martínez-Casado et al, 2016), lead succinate (Dhanya et al, 2011;Foreman et al, 2001;Jiao et al, 2009), lead squarate (Bataille et al, 2019), lead 1,4-phenylenediacetate hemihydrate (Yang et al, 2011), lead soaps (Martínez-Casado et al, 2017) and lead perchlorate terpyridine (Blake et al, 2009;Engelhardt et al, 1996) (Table S1 in the supporting information). The polyhedra around the metal atoms (Sb, Bi and Pb) in these pairs of polymorphic modifications are generally not identical.…”