Maximum filling principle and sublattice characteristics for the atoms of period 4 elements

The most important characteristics of the Voronoi-Dirichlet polyhedra (VDP) of A atoms (A = K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br, or Kr) were determined. The sublattices contain chemically identical A atoms in the crystal structures of 136395 inorganic and organoelement compounds. Irrespective of the nature of period 4 element, the VDP of A atoms have most often 14 faces, the Fedorov cuboctahedron being the most abundant VDP type. In the crystals, A atoms were found to have, most often, C ₁ site symmetry (75% of cases) and also C _s , C _i , and C ₂ site symmetries (6 to 4%). Certain relationships were shown to exist between the nature of the A atom and the preferred symmetry of the site it occupies in the crystal structures.     

Manganese Stereochemistry in the Structures of Oxygen-Containing Compounds

The Voronoi-Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to carry out crystal chemical analysis of coordination of 1304 sorts of Mn atoms in the structure of 859 oxygen-containing compounds. The manganese atoms whose oxidation number varies from 2 to 7 were found to bind 4 to 8 oxygen atoms giving rise to the MnO _n coordination tetrahedra (n = 4), square pyramids (n = 5), octahedra or trigonal prisms (n = 6), pentagonal bipyramids or one-cap trigonal prisms (n = 7), trigonal dodecahedra, cubes, square antiprisms, or hexagonal bipyramids (n = 8). The effect of the valence state and the coordination number of manganese atoms on the parameters of their VDP was studied. The existence of a general linear correlation between the solid angles of the VDP faces corresponding to Mn-O bonds and the corresponding interatomic distances, which vary over a broad range (1.55–3.12 Å), was established. The VDP characteristics can be used to determine the valence state of Mn atoms in the crystal structures and in the crystal chemical analysis of manganites with giant magnetoresistance.     

The coordination polyhedra ZnS<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> in crystal structures

Voronoi-Dirichlet polyhedra (VDP) and the intersecting sphere method were used to analyze the coordination of zinc atoms in the structures of all known compounds containing ZnS _n polyhedra. The Zn(II) atoms were found to coordinate 6, 5, 4, 3, or 2 sulfur atoms to form coordination octahedra or trigonal prisms (n = 6), trigonal bipyramids (n = 5), tetrahedra (n = 4), triangles ZnS₃, or dumbbells ZnS₂. The effect of the coordination number of zinc atoms on the key parameters of zinc VDP is considered. A common linear dependence of the solid angles of the VDP faces corresponding to both valence and non-valence Zn-S contacts on the interatomic distances was established to exist. Although the Zn-S bond lengths vary over a broad range (2.39 to 3.29 Å), the Zn VDP volume almost does not depend on its C.N. with respect to sulfur. Some characteristic features of Zn stereochemistry are considered from the 18-electron rule standpoint.     

Crystal chemistry of lanthanide oxochlorotungstates

Crystal chemical properties of lanthanide oxochlorotungstates of composition LnWO₄Cl (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm) are reported. The unit cell parameters a, b, c, c′, and V of the LnWO₄Cl compounds are correlated with lanthanide ionic radii from different radius systems and with the lanthanide atomic number. The ionic radius systems most suitable for describing the crystal chemical properties of the lanthanide oxochlorotungstates are determined.     

Gas-phase synthesis of terbium and lutetium carboxylates

Gas-phase ligand exchange between volatile lanthanide dipivaloylmethanates (Ln(dpm)₃; Hdpm is dipivaloylmethane, Ln = Tb, Lu) and o-substituted aromatic carboxylic acids (HCarb = Hsal is o-hydroxybenzoic acid, Habz is o-aminobenzoic acid, Hpobz is o-phenoxybenzoic acid, Hpa is o-anilinobenzoic acid). The gas-phase reaction involves the formation of the mixed-ligand complex Ln (dpm)_3?n (Carb)n, which is subsequently converted into tris-carboxylate (Ln(Carb)₃) on heating of the product in vacuum.     

Maximum filling principle and sublattices of actinide atoms in crystal structures

The most important characteristics of the Voronoi-Dirichlet polyhedra (VDP) of A atoms (A is actinide) in chemically homogeneous sublattices in the crystal structures of 3479 inorganic, coordination, and organometallic compounds are determined. The effect of the actinide nature on the A-A interatomic distances in the crystal structures is considered. In the Th, U, Np, or Pu sublattices, VDP have most often 14 faces and the Fedorov cuboctahedron is the most abundant type of VDP, whereas in Ac, Pa, Am, Cm, Bk, or Cf sublattices, the VDP have mainly 12 faces and are shaped like rhomobododecahedra. In A sublattices that typically form VDP with 14 faces, the actinide atoms occupy, most often, sites with C ₁ symmetry (47 to 59% of the sample size). In the case of actinides whose A sublattices tend to form VDP with 12 faces, the C ₁ site symmetry is found either very rarely (Pa, Am, Cf) or not at all (Ac, Cm, Bk).     

Mononuclear and heterodinuclear phenanthrolinedione complexes of <Emphasis Type="Italic">d</Emphasis>- and <Emphasis Type="Italic">f</Emphasis>-block elements

1,10-Phenanthroline-5,6-dione (Phd) complexes of group 3 and lanthanide elements having formulae Ln(hfac)₃(Phd) (Ln = Y, Eu, Yb; hfac = hexafluoroacetylacetonate) were synthesised and characterised. Complexes of d-block elements of the type [MCl(Phd)(p-cymene)]⁺ (M = Ru, Os) were also prepared. In all these species, coordination of the polydentate ligand occurs by the N-donor moieties, as indicated by DFT calculations. The novel compounds were tested, together with fac-ReBr(Phd)(CO)₃, as precursors for the preparation of heterobimetallic d/f derivatives. The reaction of the rhenium complex with yttrium or lanthanide anhydrous triflate salts led to the formation of the complexes ReBr(CO)₃(N,N′-Phd-O,O′)Ln(OTf)₃(THF) (Ln = Y, Eu, Yb), where the trivalent ions interacted with the quinonoid moiety. The redox properties of the rhenium centre were strongly affected by the coordination of Ln(OTf)₃, as observed by comparing the cyclic voltammetry measurements carried out on fac-ReBr(Phd)(CO)₃ and on ReBr(CO)₃(N,N′-Phd-O,O′)Y(OTf)₃.     

Formation of heterometallic compounds in mixed solutions of nickel(II)-Schiff base complexes and lanthanide nitrates: Electrospray ionization mass spectrometry data

Atmospheric-pressure electrospray ionization mass spectrometric data are reported for methanolic Ni(SB) + Ln(NO₃)₃ · nH₂O solutions (H₂SB = N,N′-ethylene-bis(salicylaldiimine), N,N′-ethylene-bis(3-methoxysalicylaldiimine), N,N′-ethylene-bis(acetylacetonediimine); Ln = La, Eu, Lu). Dinuclear and trinuclear heterometallic complexes of composition [(Ni(SB)) _x Ln(NO₃)₃] (x = 1, 2) form in these solutions. The dinuclear-totrinuclear ion intensity ratio depends on the natures of the lanthanide and the Schiff base.     

Crystal and molecular structures and luminescence properties of [Eu(Cin)<Subscript>3</Subscript>]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> complex

The crystal structure of europium cinnamate of the composition [Eu(Cin)₃] _n (Cin is cinnamic acid anion C₉H₇O ₂ ^? ) was determined by X-ray crystallography (a = 22.626(1) Å, c = 7.7330(7) Å, space group R3/c, Z = 3, ρ_calc = 1.448 g/cm³). The coordination polyhedron of Eu atoms is a distorted trigonal prism with three centered square faces. The structure is built of infinite polymeric chains [Eu(Cin)₃] _n running along the c axis and linked by van der Waals and π stacking interactions. Luminescent characteristics of the compound were determined.     

The coordination polyhedra GaS<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> in crystal structures

Voronoi-Dirichlet polyhedra (VDP) and the intersecting sphere method were used to perform coordination analysis of 204 crystallographically different gallium atoms in the structures of all known compounds containing GaS _n polyhedra. The Ga(III) atoms in crystal structures were found to be linked to 6, 4, or three sulfur atoms to form coordination octahedra, tetrahedra, and triangles, respectively, whereas Ga(II) atoms are bound only to three sulfur atoms and a gallium atom. The effect of the valence state and the coordination number of gallium atoms on the key parameters of the VDP is considered. A common linear dependence of the solid angles of the VDP faces corresponding to the Ga-S bonds on the corresponding interatomic distances, which vary from 2.09 to 2.53 Å, was established to exist.     

Quantum-chemical study of lutetium,ytterbium, and gadolinium phthalocyaninates PcLnCl

Structural parameters and IR spectra of the (¹A₁//C_4v)-PcLuCl, (²B₂//C_4v)-PcYbCl, and (⁸A₂//C_4v)-PcGdCl molecules, (²A₂//C_4v)-Pc⁺LuCl, (3B₁//C_4v)-Pc⁺YbCl, and (⁹A₁//C_4v)-Pc⁺GdCl cations, (¹A_g//D_2h)-PcLuCl₂LuPc dimer, and PcLuCl···PcLuCl coaxial molecular pair have been simulated using the DFT (U) PBE0/SDD method. The PcLnCl (Ln = Lu, Yb, Gd) molecules have exhibited the equilibrium Ln–N bond length of 222, 223, and 230 pm, the Ln–Cl bond length of 245, 246, and 253 pm, the dipole moment of 4.73, 4.57, and 4.84 D directed from Cl to Ln, and ionization potential of 6.6 eV. β-Decay (¹A₁//C_4v)-Pc¹⁷⁷LuCl → (¹A₁//C_4v)-(Pc^177mHfCl)⁺ occurs with no significant change of the charge on the metal atom.     

Compositions of nanoparticles of hexagonal symmetry

The formulas for calculation of the number of atoms in nanoparticles with symmetry group D _6h are reported. The numbers of atoms are determined by six structurally invariant numbers and the “quantum number” of the group order n. Eight classes of nanostructures with symmetry group D _6h are revealed: C _{? + 12z} , where z = 0, 1, 2, …, and C _? is C ₂, C ₆, C ₈, or C ₁₄. The sum rule for the coordination numbers of all atoms of subshells related to symmetry elements is established. Two-dimensional nanoparticles are considered.     

Maximum filling principle and sublattice characteristics for the atoms of period V elements

The most important characteristics of the Voronoi-Dirichlet polyhedra (VDP) were determined for the 146 493 crystallographically different A atoms (A = Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, I, or Xe) in sublattices containing chemically identical atoms in the crystal structures of 82093 inorganic and organoelement compounds. Irrespective of the nature of the element of period 5, the VDP have most often 14 faces, the Fedorov cuboctahedron being the most abundant VDP type. The metal atoms A were found to have, most often, C ₁ site symmetry (79% of cases) and also C _s, C ₂, and C _i site symmetries (7 to 2%). Certain relationships were shown to exist between the nature of the metal atom and the preferred symmetry of the site it occupies in the crystal structure.     

Maximum filling principle and sublattice characteristics for the atoms of period 6 elements

The most important characteristics of the Voronoi-Dirichlet polyhedra (VDP) were determined for the 88223 crystallographically different A atoms (A = Cs, Ba, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, or Bi) in sublattices containing chemically identical atoms in the crystal structures of 52370 inorganic and organoelement compounds. Irrespective of the nature of the A element, the VDP have most often 14 faces, the Fedorov cuboctahedron being the most abundant VDP type. The metal atoms A were found to have, most often, C ₁ site symmetry (76% of cases) and also C _s , C ₂, C _i , and C _2v site symmetries (7 to 2%). Certain relationships were shown to exist between the nature of the metal atom and the preferred symmetry of the sites it occupies in the crystal structures.     

Separate Crystallization of Lanthanide Oxalates and Calcium Oxalates from Nitric Acid Solutions

The separation of lanthanides from calcium compounds in the form of oxalates from hot nitric acid solutions of Ln(NO₃)₃ and Ca(NO₃)₂ with the insertion of oxalic acid and a Ln₂(C₂O₄)₃ · nH₂O crystal seed was studied by mass-spectrometric, atomic emission, microscopic, X-ray diffraction, and fluorescence analyses. The produced single-phase precipitate was found to contain an isomorphic impurity of La–Sm oxalates, while calcium oxalate remained in the hot nitric acid solution (95°С) saturated with oxalic acid. This facile and efficient method provides Ln₂(C₂O₄)₃ · nH₂O (n = 9.5 mol) in one step in a 80.1 rel. % yield, with the major phase being at least 99.4 wt %. The unit cell parameters were determined for the crystals of the isomorphic lanthanide oxalate mixture: a = 11.243(2) Å, b = 9.591(2) Å, c = 10.306(2) Å; α = γ = 90°, β = 114.12(1)°; Z = 2; V = 1013.7(5) ų.     

Carbon in boron carbide: The crystal structure of B<Subscript>11.4</Subscript>C<Subscript>3.6</Subscript>

A single crystal of boron carbide obtained from a self-propagating high-temperature synthesis (SHS) product was studied by X-ray crystallography: B_11.4C_3.6, a = 5.594(2) Å, c = 11.977(7) Å, V = 324.6(7) ų, space group R3m, Z = 3, ρ_calcd = 2.56 g/cm³, R = 0.048. The content of carbon in the single crystal was estimated at ～24 at % from analysis of the unit cell parameters, bond lengths, and the volume of B_{12 ? x} C _x icosahedra, which demonstrated the possibility of obtaining by SHS carbon-rich boron carbide crystals due to the substitution of carbon atoms for boron atoms in icosahedra. Comparison of the X-ray crystallographic data for single crystals of boron carbide with the results of quantum-chemical calculations (an ab initio method (the 3–21G basis set) with geometry optimization) showed that the C-B-C group in a crystal has a nonlinear structure.     

Water-fluorine chains in (18-crown-6)·NH<Subscript>4</Subscript>F·3H<Subscript>2</Subscript>O hydrate

The structure and composition of (18-crown-6)·NH₄F·3H₂O hydrate were determined from single crystal XRD data at 173 K. The compound is monoclinic P2₁/n with unit cell parameters a = 11.913(1) Å, b = 7.928(1) Å, c = 20.679(3) Å; β = 105.14(1)°. The ammonium cation is included in the crown-ether and forms three hydrogen bonds to oxygen atoms. The water molecules and the fluorine ions connected by hydrogen bonds form chains consisting of square faces and running parallel to the b axis of the crystal.     

Visible and near-infrared luminescence of polycatenated cationic pyridinone lanthanide networks

A series of isomorphic lanthanide coordination polymers [Ln(III)(MBP)_2(NO_3)_2(Br)?2C_3H_6O] [Ln=Eu, Tb, Er, Yb, and Gd; MBP=N,N′-methylene-bis(pyridin-4-one)] featuring polycatenated sql cationic network and incorporated bromide counter ion were prepared. Their visible and near-infrared(NIR) luminescence properties were characterized by steady-state excitation and emission spectra, as well as luminescence lifetimes and quantum yields. The D_(2d) dodecahedron coordination geometry causes visible light excitations and strongly monochromatic emissions. The external heavy-atom environment induces remarkable enhancement on the NIR emissions. The sensitization processes are revealed by analyzing the electronic properties of MBP ligand.     

Crystal structure of EuLnAgS<Subscript>3</Subscript> (Ln = Gd and Ho) compounds

The crystal structures of the first prepared EuLnAgS₃ (Ln = Gd and Ho) compounds, which have two polymorphs, were determined by X-ray powder diffraction. α-EuLnAgS₃ phases are isostructural to BaErAgS₃ (monoclinic crystal system, space group C2/m): a = 17.3168(10) Å, b = 3.9683(2) Å, c = 8.3174(4) Å, β = 103.94° (EuGdCuS₃); a = 17.1729(12) Å, b = 3.9367(3) Å, c = 8.2905(6) Å, β = 103.9° (EuHoCuS₃). β-EuLnAgS₃ phases belong to the AgBiS₂ structure type (cubic crystal system, space group Fm-3m): a = 5.739(2) Å (EuGdCuS₃) and a = 5.678 Å (EuHoCuS₃). In the α-EuLnAgS₃ crystal structure, LnS₆ octahedra and AgS₅ trigonal bipyramids share edges to form a three-dimensional (3D) structure with channels accommodating Eu²⁺ ions. A decrease in Ln³⁺ ionic radius gives rise to the crystal-chemical contraction of the 3D structure.