Minerals and synthetic Pb(II) compounds with oxocentered tetrahedra: review and classification

Pb9O4(BO3)2(NO3)4: A Lead Borate-Nitrate Containing an Anion-Centered [O8Pb18]∞ Chain with Large Optical Anisotropy

In the field of structural chemistry, crystals containing the [OM4] tetrahedra (M = metal cation) structure have been well documented. However, compounds containing both [OPb4] tetrahedra and π-conjugated groups are less reported due to their structural complexity. In this work, a new lead borate-nitrate, Pb9O4(BO3)2(NO3)4, has been synthesized by a high temperature melt method. Notably, the structure of Pb9O4(BO3)2(NO3)4 contains special [O8Pb18]∞ chains formed by the [OPb4] tetrahedra. This compound possesses a large optical anisotropy with birefringence of Δn = 0.117 at 546 nm.

Self Cycloaddition of o-Naphthoquinone Nitrosomethide to (±) Spiro{naphthalene(naphthopyranofurazan)}-one Oxide: An Insight into its Formation

2-Hydroxy-1-naphthaldehyde oxime was oxidized by AgO (or Ag2O), in presence of N-methyl morpholine N-oxide (NMMO), to the title spiro adduct-dimer (±)-Spiro{naphthalene-1(2H),4'-(naphtho[2',1':2,3]pyrano[4,5-c]furazan)}-2-one-11'-oxide by a Diels-Alder(D-A) type self-cycloaddition, through the agency of an o-naphthoquinone nitrosomethide (o-NQM). Moreover, 2-hydroxy-8-methoxy-1-naphthaldehyde oxime was prepared and subjected to the same oxidation conditions. Its sterically guided result, 9-methoxynaphtho[1,2-d]isoxazole, was isolated, instead of the expected spiro adduct. The peri intramolecular H bonding in the oxime is considered to have a key contribution to the outcome. Geometry and energy features of the oxidant- and stereo-guided selectivity of both oxidation outcomes have been explored by DFT, perturbation theory and coupled cluster calculations. The reaction free energy of the D-A intermolecular cycloaddition is calculated at -82.0 kcal/mol, indicating its predominance over the intramolecular cyclization of ca. -37.6 kcal/mol. The cycloaddition is facilitated by NMMO through dipolar interactions and hydrogen bonding with both metal complexes and o-NQM. The 8(peri)-OMe substitution of the reactant oxime sterically impedes formation of the spiro adduct, instead it undergoes a more facile cyclodehydration to the isoxazole structure by ca. 4.9 kcal/mol.

Pb6O5(NO3)2: A Nonlinear Optical Oxynitrate Structurally Based on Lead Oxide Framework

A high second harmonic generation response is demonstrated by a Pb₆O₅(NO₃)₂ lead oxynitrate whose identity was verified upon reinvestigation of the PbO-Pb(NO₃)₂ system. Its crystal structure exhibits a unique cationic [Pb₆O₅]²⁺ framework hosting orientationally ordered NO₃^- triangles in the channels. Easy preparation and high thermal stability (until ∼500 °C in air) suggest it to be a new promising NLO material.

Synthesis, characterization and morphotropic transitions in a family of M[(UO2)(CH3COO)3](H2O) n (M=Na, K, Rb, Cs; n=0–1.0) compounds

Experimental investigations of crystallization in a family of uranyl triacetate compounds with Na, K, Rb and Cs were performed. The crystal structures of two novel Cs- and Rb-bearing tri(acetato)uranylates were solved, and the content of H2O molecules in the crystal structure of K-bearing uranyl triacetate was refined. Synthesized compounds were analyzed using IR spectroscopy and single-crystal X-ray diffraction. Crystal chemical analysis of the M[(UO2)(CH3COO)3](H2O) n family (M = Na, K, Rb, Cs; n = 0–1.0) reveals the sequence of structural transformations depending on the size of alkali cation resulting in the symmetry reduction from cubic P 213 (for Na), through tetragonal I 41/a (for K and Rb) to triclinic P 1̅ space groups (for Cs), which is in accordance with the principle of morphotropism, suggested by Paul von Groth, founder of the Zeitschrift für Krystallographie journal, in 1870.

Hydrocerussite-related minerals and materials: structural principles, chemical variations and infrared spectroscopy

White lead or basic lead carbonate, 2PbCO3·Pb(OH)2, the synthetic analogue of hydrocerussite Pb3(OH)2(CO3)2, has been known since antiquity as the most frequently used white paint. A number of different minerals and synthetic materials compositionally and structurally related to hydrocerussite have been described within the last two decades. Herein, a review is given of general structural principles, chemical variations and IR spectra of the rapidly growing family of hydrocerussite-related minerals and synthetic materials. Only structures containing a hydroxo- and/or oxo-component,i.e.which are compositionally directly related with hydrocerussite and `white lead', are reviewed in detail. An essential structural feature of all the considered phases is the presence of electroneutral [PbCO3]0cerussite-type layers or sheets. Various interleaved sheets can be incorporated between the cerussite-type sheets. Different sheets are stacked into two-dimensional blocks separated by the stereochemically active 6s2lone electron pairs on Pb2+cations. Minerals and synthetic materials described herein, together with a number of still hypothetical members, constitute a family of modular structures. Hydrocerussite, abellaite and grootfonteinite can be considered to constitute a merotype family of structures. The remaining hydrocerussite-related structures discussed are built on similar principles, but are more complex. Structural architectures of somersetite and slag phase from Lavrion, Attica, Greece, are unique for oxysalt mineral structures in general. Thus, the whole family of hydrocerussite-related phases can be denoted as a plesiotype family of modular structures. The crystal structures of hydrocerussite from Merehead quarry, Somerset, England, and of its synthetic analogue, both determined from single crystals, are reported here for the first time. The results of the infrared (IR) spectroscopy show that this method is useful for distinguishing several different minerals related to hydrocerussite and their synthetic analogues.

Derivation of bond-valence parameters for some cation-oxygen pairs on the basis of empirical relationships between ro and b

Relationships between the ro and b bond-valence parameters are investigated for ideal and distorted coordination polyhedra. For some ranges of the b values, this relationship can be approximated by linear functions, which are used to derive bond-valence parameters for some cation-oxygen pairs (ro , b [Å]): Cu2+—O (1.679, 0.36), Pb2+—O (1.963, 0.49), Hg2+—O (1.924, 0.38), Bi3+—O (1.990, 0.48), Sb3+—O (1.885, 0.53), Y3+—O (2.028, 0.35), La3+—O (2.086, 0.45), Nd3+—O (2.021, 0.46).

Crystal chemistry of the mendipite-type system Pb3O2Cl2—Pb3O2Br2

The crystal structures of the mendipite series Pb3O2Cl2—Pb3O2Br2have been solved by direct methods. The structures are based upon [O2Pb3]2+double chains of edge-sharing OPb4tetrahedra. There are three symmetrically independent Pb2+cations. The number of nonequivalent halogen sites is two (X1, X2). Short Pb—O bonds are located on one side of the Pb2+cations and weak Pb-X bonds are located on the other side of the Pb2+coordination sphere. The evident strong distortion of the Pb2+coordination polyhedra is due to the stereoactivity of the 6s2lone electron pairs of the Pb2+cations. Pb1-X2 and Pb2-X2 bonds are the most sensitive to the X site occupancy, which is in agreement with the non-linear behavior of theaandcparameters. Determination of unit-cell parameters by single crystal studies showed strong deviation from Vegard's rule. Nonlinearity of the lattice parameters is caused by selective ordering of the halide anions over X1 and X2 sites. Br atoms prefer the X2 position, whereas Cl prefers the X1 site. The angle between two adjacent OPb4tetrahedra was determined to analyze the influence of halogen atoms on the structure of the [O2Pb3]2+chain. Different occupancy of the X1 siteby Cl and Br atoms leads to most pronounced angular changes. These observations may be interpreted as adaptation of the [O2Pb3]2+double chains to the large halide ions in the crystal structures of the mendipite series compounds.