Almaz Aliev

New [PbBi2O4][Bi2O2]Cl2 and [PbnBi10-nO13][Bi2O2]nCl4+n Series by Association of Sizable Subunits: Relationship with Arppe’s Compound Bi24O31Cl10 and Luminescence Properties

Four new mixed lead-bismuth oxychloride compounds have been prepared and characterized by single crystal X-ray diffraction. Their crystal structures are described on the basis of the association of distinct building units found in parent Pb or Bi oxychlorides. The new compound PbBi4O6Cl2 is formed of the stacking of 2D positive [Bi2O2](2+) layers and neutral [PbBi2O4](0) double layers separated by Cl(-) anions. Similar motifs with finite lengths are combined together in the new series [Pb(n)Bi(10-n)O13][Bi2O2](n)Cl(4+n). From the structural viewpoint, it is striking that this family of homologous phases is strongly related to Bi24O31Cl10 well-known as Arppes compound in which the fluorite-like [Bi2O2]n subunit was increased from n = 1 (mixed Bi/Pb Arppes compound) to n = 2, 3, and 4 new members. The preparation of the respective powders shows the predominant stability of the n = 2 term which was prepared as a single-phase, while other terms have not been obtained in absence of secondary phases. For n = 2, the impedance spectroscopy shows a conductivity value σ ∼ 10(-3) S cm(-1) at 650 °C and suggests a contribution of Cl(-) in the diffusion process. Most remarkable, PbBi4O6Cl2 as well as [Pb2Bi8O13][Bi2O2]2Cl6 show very bright red emission at low temperature, which could be assigned to Bi(3+) transitions by comparison to BaBi4O6Cl2. The different shapes of the excitation spectra lead to the assumption of a complete Pb-Bi energy transfer.

Multidimensional open-frameworks: combinations of one-dimensional channels and two-dimensional layers in novel BI/M oxo-chlorides.

Here we discuss the synthesis and characterization of three novel bismuth oxo-chlorides ([Bi6Na0.5O7.5][Na0.5Cl3]channel[Cl]layer; [Bi17PbO22][Cl6]channel[Cl3]layer; [Bi9(Pb0.2Mn0.8)O12][Cl3]channel [Cl2]layer) which all show an original multidimensional crystal structure. It is formed of two-dimensional (2D)-layered blocks separated by Cl(-) layers. The blocks are porous with triangular one-dimensional (1D)-Cl(-) channels with various section sizes. This multidimensional feature is unique in the field of Bi and Pb oxo-halides, while so far only 1D or 2D halides units have been reported. The stability of the framework is allowed by Bi(3+)/M(n+) aliovalent substitution to balance charge neutrality. The channel and tunnel walls are formed by edge-sharing O(Bi,M)4 oxocentered tetrahedra, while the triangular tunnel junctions are achieved by O(Bi,M)5 pyramids. The three compounds are rather stable, but only [Bi6Na0.5O7.5][Na0.5Cl3]tunnel[Cl]layer was obtain as a single-phase material so that its photoluminecence properties have been investigated. It shows an unusual red bright luminescence with a maximum at 14150 cm(-1) at low temperatures due to Bi(3+) transitions that are well explained by the Bi-Cl bonding scheme.

Labile degree of disorder in bismuth-oxophosphate compounds: Illustration through three new structural types

Here, we analyze the crystal structures of three new Bi/M oxophosphates, focusing on the ambiguity between order and disorder in different structural subunits. The three structures are original but systematically built on the assembly of O(Bi,M)4 tetrahedra into various 1D-oxocenterd units, separated by PO4 groups that create cationic channels. Two main subunits show versatile degrees of disorder, i.e., the cationic channels and some of the terminal O(Bi,M)4 entities. (a) In the compound [Bi2(Bi1.56K0.44)(dis)O3]K0.88(dis)(PO4)2, the K/K and K/Bi disorder is total on both nano- and micro-sized domains. (b) In the incommensurately modulated [Bi10(Bi∼0.5Cd∼0.5)8(dis)O16](Bi0.6Cd0.8)2(ord)(PO4)8, only the cationic channels show an ordered Bi/Cd arrangement which can be modified by minor stoichiometric changes between domains. (c) In [Bi18Zn10O21](ord)Zn5(ord)(PO4)14, both subunits are almost perfectly ordered (complex Bi/Zn sequence) into a 7-fold supercell, but this order strongly depends on the observation scale and is mainly lost in micronic-grains also due to slight compositional changes. However, the refined noncentrosymmetric organization is maintained (SHG tests) in the bulk. The relative stability of ordered versus disordered sites is discussed on the basis of the existence of two possible mixed sites and probably depends on the M chemical nature. Disorder was characterized by use of solid-state (31)P NMR probing for the first two cases. Finally, the observed disordered or long periodicities along the infinite dimension suggest the sketch of a periodic/rigid skeleton of O(Bi,M)4 units with counterions filling the interspace in more or less disordered arrangements.

Investigation of New Alkali Bismuth Oxosulfates and Oxophosphates with Original Topologies of Oxo-Centered Units

Two new alkali bismuth oxosulfates, [Bi12O15]Li2(SO4)4 (I) and [Bi7K2O8]K(SO4)4 (II), have been synthesized by heating a mixture of Bi2O3, CuSO45H2O, and A2CO3 (A = Li, K), and characterized by single crystal XRD, transmission electron microscopy, and multiphoton SHG and IR spectroscopy. In the above formula the [BixOy] subunits denote the 3D-porous (I) or 1D-columnar (II) polycationic host-lattice formed of edge-sharing OBi4 or O(Bi,K)4 oxocenterd tetrahedra. The SO4(2-) groups and alkali ions are arranged into channels in the interstices leading to original opened crystal structures for these two first reported alkali oxo-bismuth sulfates. The strong adaptability of the oxocentered framework is demonstrated by the possibility of preparing single crystals of [Bi8.73K0.27O8]K1.54(PO4)4 (III) whose crystal structure is similar to those of II with disorder between OBi4 and O(Bi3,K) tetrahedra and different channel occupancy due to the aliovalent replacement of SO4(2-) for PO4(3-).

Original oxo-centered bismuth oxo-arsenates; critical effect of PO4 for AsO4 substitution

This work deals with the synthesis and crystal structure study of new bismuth oxo-arsenates and their homologous oxo-phosphates: Bi6ZnO7(AsO4)2vs. Bi6ZnO7(PO4)2 and Bi3.667Cd3O4(AsO4)3vs. Bi3Cd4O4(PO4)3. Their crystal structures were solved using single crystal X-ray diffraction. These are two other examples of crystal structures built on ribbon-like polycations formed of the linkage of oxo-centered O(Bi,M)4 tetrahedra sharing edges and surrounded by isolated XO4 groups (X = As or P), where the O(Bi,M)4 units are derived from the fluorite topology structure. Dealing with Bi6ZnO7(PO4), its acentric space group was confirmed by preliminary second harmonic generation (SHG). The P/As substitution led to a centrosymmetric space group due to local reorientation of oxo-anions. This is strongly related to steric effects between AsO4 (d As–O = 1.6–1.7 A) and PO4 (d P–O = 1.4–1.5 A). Concerning Bi3.667Cd3O4(AsO4)3 and Bi3Cd4O4(PO4)3, they show a second example of the reorientation of the XO4 groups depending of the X chemical nature. Finally, we present an original topology of oxo-centered units obtained with Bi5KO5(AsO4). The photoluminescence properties of Bi5KO5(AsO4) and Bi6ZnO7(AsO4)2 were also investigated. The first one emits at room temperature in the reddish-orange range (single band peak at 615 nm assigned to the Bi3+: 3P1 → 1S0 transition) whereas the second exhibits a weak emission in the green range (peak at 530 nm). Its intriguing temperature dependence is discussed in the paper.

Synthesis and structural variety of first Mn and Bi selenites and selenite chlorides

Abstract Single crystals of new Mn2[Bi2O](SeO3)4 (I), MnBi(SeO3)2Cl (II), MnIIMnIII(SeO3)2Cl (III), Mn5(SeO3)2Cl6 (IV), and Mn4(Mn5,Bi)(SeO3)8Cl5 (V) have been synthesized by chemical vapour transport and hydrothermal methods. They have been structurally characterized by single crystal X-ray diffraction analysis. The compounds II–V are the first Mn selenite chlorides, while the I, II and V compounds are the first Bi-containing Mn oxoselenites. Structural relationships of the new phases with other compounds are discussed. An overview of the mixed-ligand MnOmCln polyhedra in inorganic compounds is given.

Possible cationic ordering in bismuth oxide phosphates

Inorganic compounds with structures containing XA4 anion-centered tetrahedra (X = anion, A = metal cation, Bi3+ in our case) are very attractive for solid-state chemists1, because of their interesting physical properties such as low dimensional-magnetism, ionic conductivity, luminescence, optical anisotropy, second harmonic generation, etc. In particular, bismuth oxides and oxy-salts demonstrate a great structural diversity due to the often-found OBi4 units able to organize into 0-dimensional (0D), 1D, 2D and 3D frameworks. Due to valence unit reasons, the OBi4 tetrahedra are usually either strongly distorted, or admit the co-presence of a different Mn+ cation into O(Bi,M)4 tetrahedra, whose M-O contribution is relaxing the central oxygen bond valence sum. The variety of aliovalent M cations that can be incorporated into the O(Bi,M)4 tetrahedral bricks make this class of inorganic compounds a gold mine of inspiration for the findings of novel structural motifs and physical properties. Particularly, the Bi2O3-MO-P2O5 (M = divalent metals)2-5 ternary system displays an impressive number of distinct crystal structures based on the association of O(Bi)4 and O(Bi,M)4 sharing edges to form ribbons of variable width and differently connected and surrounded by phosphates. Sometimes, between four PO4 groups takes place tunnels, hosting M2+ cations. These tunnels and the mixed Bi3+/M2+ at the edges of ribbons are responsible for strong disorder in the structure (around phosphorus). Most of the studied compounds show evidence of modulated structures either by electron diffraction6-7 but also sometimes on XRD single crystal patterns17 that denote a partial or complete ordering in large periodicities that could occur in small-sized domains but can also extend at a larger scale. Taking into account the number of concerned compounds this ambiguity between full, partial and complete disorder deserves attention. Here we present three new structural types that cover the full panorama in terms of order-disorder duality in this unique class of compounds using complementary methods such as NMR spectroscopy, electron microscopy and X-Ray diffraction. For example the [Bi10(Bi~0.5Cd~0.5)8O16] (PO4)8(Bi0.6Cd0.8)2 new compound shows a modulation vector q ~ 0.4c* and the structure was solved using the 4D formalism. It led to the evidence of a partial cationic ordering in the 1D-columns (figure 1 and 2).

Phase homology and structural prediction in extended series of inorganic bi-based compounds

we are interested in the organization of bismuth-based 1D sizeable building-units (BUs) into new XO4 containing frameworks (X=P, As, V). In the Bi2O3-X2O5-MOx (M=various cations) ternary diagrams, structural relationships between the phases in competition have been generalized with respect to systematically found sizeable BUs. For the first time we present here an unified model which allows a generalization of most of the reported compounds of these chemical systems and an-easy distinction of pertinent BUs and comprehension of their assembly into the final edifice. The concerned crystal-types mainly follow from the X/M for Bi cationic substitution in the -Bi2O3 fluorine-like structure. In its ideal form, the -Bi2O3 is better described from a regular lattice of edge-sharing (O,)Bi4 “anti-tetrahedra” [1,2]. It involves that all cations align along a “square-grid”. Experimentally, we observe that XO4 tetrahedra substitute the Bi-sites with important constraints, such that the “cationic grid” persists but strongly distorted. The degree of distorsion is proportional to the ratio of XO4. Strikingly, sizeable 1D(2D)-ribbons(planes) of O(Bi)4 tetrahedra persist (=BUs), surrounded by XO4 groups. On the basis of such an extended rational model, the structural prediction, formulation and elaboration of novel archetypes have been successfully achieved for several terms [3,4]. Currently, the characterization of variously sized BUs from n=1 to emphasizes the thermo-dynamical stability of various structural types, despite their closed chemical compositions. We will pay special attention to several aspects such as HREM/XRD complementarity, disorder-order duality and recent tailormade compounds including polar materials.