Protonated Amine Molecules Research Articles

Effect of Protonated Amine Molecules on the Oxygen Reduction Reaction on Metal-Nitrogen-Carbon-Based Catalysts

Non-precious metal electrocatalysts based on pyrolyzed metal, nitrogen, and carbon (MNC) are viewed as an inexpensive replacement for platinum-based electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. One of the enduring issues in the field of MNC catalysis is identifying the exact active structure responsible for the ORR. Many ORR active sites have been proposed recently, such as transition metal coordinated to (i) four pyrrolic nitrogens, (ii) four pyridinic nitrogens, and (iii) four pyridinic nitrogens interacting with one protonated nitrogen; among these, the latter is viewed as the most promising active site for the ORR. In this study, we have synthesized a manganese-based MNC catalyst (MnNx/C). EPR and X-ray absorption fine structure (XAFS) analysis indicated the presence of four nitrogens around the Mn(II) ion. The ORR performance of an MnNx/C catalyst was recorded in the presence of the disodium salt of ethylenediaminetetraacetic acid (EDTA-Na2), ethylene diamine (ED), and combination of ED and acetic acid (AA). The presence of EDTA-Na2 and ED + AA in the electrolyte solution maximizes the availability of protonated amine-N around the catalyst. As a consequence, we noticed significant improvement in the ORR kinetics in H2SO4 (10−4, 10−6 N) and NaOH (10−6 to 10−2 N) electrolyte solutions. The improvement in the onset potential for the ORR ranged between 80 and 160 mV as the pH was changed from 4 to 12. Based on XAFS data and ORR polarization in the presence of EDTA-Na2 and ED + AA, we believe that the MnN4 moiety interacting with the protonated amine is the most probable active site contributing to ORR activity in the H2SO4 (10−4, 10−6 N) and NaOH (10−6 to 10−2 N) electrolyte solutions.

Crystal Chemistry of Uranyl Carboxylate Coordination Networks Obtained in the Presence of Organic Amine Molecules

AbstractThree uranyl isophthalates (1,3‐bdc) and two uranyl pyromellitates (btec) of coordination‐polymer type were hydrothermally synthesized (200 °C for 24 h) in the presence of different amine‐based molecules [1,3‐diaminopropane (dap) or dimethylamine (dma) originating from the in situ decomposition of N,N‐dimethylformamide]. (UO2)2(OH)2(H2O)(1,3‐bdc)·H2O (1) is composed of inorganic tetranuclear cores, which are linked to each other through the isophthalato ligand to generate infinite neutral ribbons, which are intercalated by free H2O molecules. The compounds (UO2)1.5(H2O)(1,3‐bdc)2·0.5H2dap·1.5H2O (2) and UO2(1,3‐bdc)1.5·0.5H2dap·2H2O (3) consist of discrete uranyl‐centered hexagonal bipyramids connected to each other by a ditopic linker to form a single‐layer network for 2 or a double‐layer network for 3. The protonated diamine molecules are located between the uranyl–organic sheets and balance the negative charge of the layered sub‐networks. The phase (UO2)2O(btec)·2Hdma·H2O (4) presents a 2D structure built up from tetranuclear units, which consist of two central sevenfold coordinated uranium centers and two peripheral eightfold coordinated uranium centers. The connection of the resulting tetramers through the pyromellitate molecules generates an anionic layerlike structure, in which the protonated dimethylammonium species are inserted. The compound UO2(btec)·2Hdma (5) is also a lamellar coordination polymer, which contains isolated eightfold coordinated uranium cations linked through pyromellitate molecules and intercalated by protonated dimethylammonium species. In both phases 4 and 5, the btec linker has non‐bonded carboxyl oxygen atoms, which preferentially interact with the protonated amine molecules through a hydrogen‐bond network. The different illustrations show the structural diversity of uranyl–organic coordination polymers with organic amine molecules as countercations.

Photofragmentation spectroscopy of cold protonated aromatic amines in the gas phase

The electronic spectra of cold protonated aromatic amines: anilineH(+) C6H5-NH3(+), benzylamineH(+) C6H5-CH2-NH3(+) and phenylethylamineH(+) C6H5-(CH2)2-NH3(+) have been investigated experimentally in a large spectral domain and are compared to those of their hydroxyl homologues. In the low energy region, the electronic spectra are similar to their neutral analogues, which reveals the ππ* character of their first excited state. A second transition is observed from 0.4 to 1 eV above the origin band, which is assigned to the excitation of the πσ* state. In these protonated amine molecules, there is a competition between different fragmentation channels, some being specific to UV excitation i.e., not observed in low-energy collision induced dissociation experiments. Besides, for one amine a drastic change in the fragmentation branching ratio is observed within a very short energy range that reveals the complex excited state dynamics and fragmentation processes. The experimental observations can be rationalized using a simple qualitative model, the ππ*-πσ* model [A. L. Sobolewski, W. Domcke, C. Dedonder-Lardeux and C. Jouvet, Phys. Chem. Chem. Phys., 2002, 4, 1093-1100], which predicts that the excited state dynamics is controlled by the crossing between the ππ* excited state and a πσ* state repulsive along the XH (X being O or N) coordinate.

Uranium diphosphonates templated by interlayer organic amines

The hydrothermal treatment of uranium trioxide and methylenediphosphonic acid with a variety of amines (2,2-dipyridyl, triethylenediamine, ethylenediamine, and 1,10-phenanthroline) at 200°C results in the crystallization of a series of layered uranium diphosphonate compounds, [C10H9N2]{UO2(H2O)[CH2(PO3)(PO3H)]} (Ubip2), [C6H14N2]{(UO2)2[CH2(PO3)(PO3H)]2·2H2O} (UDAB), [C2H10N2]2{(UO2)2(H2O)2[CH2(PO3)2]2·0.5H2O} (Uethyl), and [C12H9N2]{UO2(H2O)[CH2(PO3)(PO3H)]} (Uphen). The crystal structures of the compounds are based on UO7 units linked by methylenediphosphonate molecules to form two-dimensional anionic sheets in Ubip2 and UDAB, and one-dimensional anionic chains in Uethyl and Uphen, which are charge balanced by protonated amine molecules. Interaction of the amine molecules with phosphonate oxygens and water molecules results in extensive hydrogen bonding in the interlayer. These amine molecules serve both as structure-directing agents and charge-balancing cations for the anionic uranium phosphonate sheets and chains in the formation of the different coordination geometries and topologies of each structure. Reported herein are the syntheses, structural and spectroscopic characterization of the synthesized compounds.

Mixed-ligand coordination of the (UO2)2+ cation and apophyllite topology of uranyl chlorochromate layer in the structure of ((CH3)2CHNH3)[(UO2)(CrO4)Cl(H2O)

Abstract Addition of the Cl-0 anions to the synthesis mixture stabilizes specific structures of uranyl complexes which results in new compounds with the unprecedented structural topologies. ((CH3)2CHNH3)[(UO2)(CrO4) · Cl(H2O)]is a new member of the small family of compounds based upon the Ur(Xm O n )5 (X = Cl, Br, I) bipyramids. The structure is based upon uranyl chloride chromate layers that alternate with the layers of protonated amine molecules. The layers contain UrClO4 pentagonal bipyramids that share three of its equatorial corners with CrO4 tetrahedra. Topological analysis shows that the [(UO2)(CrO4)Cl(H2O)]-0 layer belongs to the same topology of interpolyhedral linkage as in α-UO2MoO4(H2O)2. This type of topology (linkage of 4-membered rings creating 8-membered rings) is known in silicate crystal chemistry as the topology of the [Si4O10] layers in the minerals of the apophyllite group. Their linkage via various intermediate units results in a large family of open-framework and pillared silicates.

Gas sensing properties of p-type semiconducting vanadium oxide nanotubes

Vanadium oxide nanotubes (VONTs) were synthesized using the V2O5 powder as precursor with dodecylamine as structure-directing template via one-step hydrothermal way. The prepared VONTs sensors exhibit excellent sensing sensitivity and superior recovery property in detecting ethanol vapor. The response to the ethanol vapor and NO2 gases confirms that the samples are of p-type behavior at 80°C, which is associated with the presence of the protonated amine molecules in the VONTs. The sample changes to n-type behavior at 260°C arising from the decomposition of the protonated amine molecules. The p-type VONTs have potential for development of a novel gas sensor.

Synthesis, structure and properties of the first inorganic framework Ba(II) perchlorate polymer with organic template

The first 2D open-architecture Ba(II) perchlorate with organic template, [(H+4-MP)2Ba(ClO4)4]n (1) (4-MP=4-methylpyridine), has been synthesized and characterized by single-crystal and powder X-ray diffraction, elemental analysis, IR, 1H NMR, TGA, DSC and fluorescence properties. The Ba(II) centers of the icosahedral (BaO12) were chelated through μ2-perchlorate donors to form a 2D (4,4) topology with the protonated amine molecules mounted to the main body of the inorganic framework by N–H⋯O H-bonding interactions. To verify the generality of the synthetic methods, 4-MP has been replaced by other different amine templates. The results have shown that the crystallization processes are very sensitive to the induced effect of the organic templates.

Synthesis, structure and properties of the first organic-templated inorganic-framework Ba(II) perchlorate

► Complex 1 has been synthesized by performing two different methods. ► The first Ba(II) perchlorate macro-anionic inorganic-framework network. ► The protonated template molecules residing in the interlamellar space. ► Formation of (4, 4)-connected topology framework. The first organic-templated Ba(II) perchlorate with open architecture, [(C 6 H 8 N) 2 Ba(ClO 4 ) 4 ] n ( 1 ), has been synthesized in the presence of 3-methylpyridine (3-MP) under hydrothermal conditions. The compound 1 was characterized by single crystal X-ray diffraction, elemental analysis, IR, powder XRD, 1 H NMR, TGA and fluorescence spectra. The 12-coordinate Ba(II) ion was located in the center of the irregular icosahedral (BaO 12 ) cage. Then the icosahedral BaO 12 cages and the ClO 4 - linkers joined together to form a (4, 4) topology. And the protonated amine molecules were residing in the interlamellar space of the inorganic macro-anionic topology layers in the aAa mode (a = amine, A = anionic layer). The N–H⋯O hydrogen bonds ensure the stability of the structure by mounted the organic molecules to the main body of the inorganic framework. The solid-state fluorescence spectrum of complex 1 exhibits broad emission at 381 nm at room temperature, which is stronger than the free MPP (MPP = 3-methylpyridinium perchlorate). In addition, the two different synthesis methods provide an effectual impetus about applying hydrothermal reaction chemistry to build novel structures.

A New Mixed‐Valent High Nuclearity Polyoxovanadate Cluster Based on the {V18O42} Archetype

AbstractThe compound (enH2)6[HV16IVV2VO42(Cl)]·Cl2·2H2O (en = 1,2‐diaminoethane) (1), was synthesized under solvothermal conditions employing the amine as reducing agent. Compound 1 crystallizes in the orthorhombic space group Pbcn with a = 13.3343(7), b = 22.3697(3), c = 19.8012(11) Å, V = 5906.4(5) Å3, Z = 4. The central structural motif is a polyoxovanadate anion [HV18O42(Cl)]10– being composed of 18 VO5 square pyramids. The cluster shell contains a (VO5)8 ring in the vertical plane and two (VO5)5 pentagons above and below the ring which are twisted by 45° against each other.Bond valence sum analysis indicates a mixture of VIV/VV atoms with a ratio of 16:2, which is further supported by redox titration. An arrangement of these clusters within the (001) plane leads to the formation of channels hosting the protonated amine molecules, the Cl– anions and water molecules which are joined by an extended hydrogen bonding network. TG‐MS investigation shows a thermal decomposition reaction in at least three steps. The optical band gap was determined as 2.5 eV.

New Three-Dimensional Thiostannates Composed of Linked Cu8S12 Clusters and the First Example of a Mixed-Metal Cu7SnS12 Cluster

Three new compounds (enH)(6+n)Cu(40)Sn(15)S(60) (1), (enH)(3)Cu(7)Sn(4)S(12) (2), and (trenH(3))Cu(7)Sn(4)S(12) (tren = tris(2-aminoethyl)amine) (3) containing Cu(8)S(12) and Cu(7)SnS(12) clusters have been prepared from direct solvothermal reaction of the elements in amine solvents. In 1, the cubic close-packed arrangement of Cu(8)S(12) clusters, interconnected by capping SnS(4) tetrahedra and CuS(3) triangles, form two interpenetrating channel networks that are presumably filled with disordered solvent molecules. Structures 2 and 3 contain well-ordered, protonated amine molecules and Cu(7)SnS(12) clusters. The clusters are connected by SnS(4) tetrahedra to form a three-dimensional structure with ReO(3) topology. (119)Sn Mössbauer measurement is consistent with Sn(IV) atoms linking, and Sn(II) atoms within, the mixed-metal Cu(7)SnS(12) clusters.

Synthesis, crystal structure and magnetism of a new mixed germanium–polyoxovanadate cluster

A new germanium–polyoxovanadate, (H 3aep) 4[V 14Ge 8O 50]·2(aep)·13H 2O ( 1), has been synthesized under solvothermal conditions applying GeO 2, NH 4VO 3, Cu(NO 3) 2·3H 2O and an aqueous solution of 1-(2-aminoethyl)-piperazine (aep, C 6H 18N 3) in the temperature range from 110 to 150 °C. The compound crystallizes in the non-centrosymmetric tetragonal space group P-42 1 c with a = 17.193(1) Å, c = 16.501(1) Å, V = 4877.9(5) Å 3 and Z = 2. The structure consists of isolated spherical [V IV 14Ge IV 8O 50] 12− cluster anions and protonated amine molecules as counterions. The cluster anion can be viewed as a derivative of the [V 18O 42] archetype by replacing four VO 5 pyramids by four Ge 2O 7 units. The latter are formed by corner-sharing of two [GeO 4] 4− tetrahedra. At temperatures above 150 °C the compound (H 2pip) 4(Hpip) 4[V IV 14Ge IV 8O 50(H 2O)] ( 2) (pip = piperazine, C 4N 2H 10) is formed and during the reaction Cu 2+ is reduced to elemental copper. This redox reaction is essential for the formation of 2. The crystal water molecules in the structure of 1 are emitted at low temperatures. The magnetic properties are dominated by strong intra-cluster antiferromagnetic coupling and the strongest exchange between edge- and corner-sharing VO 5 square pyramids results in an eight-membered spin ring to which two three-membered spin bridges are joined. The magnetic susceptibility data suggest that even at the low temperature of 2 K several multiplet states are still significantly populated.

The Layered Thiostannate (dienH2)Cu2Sn2S6: a Photoconductive Inorganic−Organic Hybrid Compound

The new inorganic-organic hybrid compound (dienH2)Cu2Sn2S6 (dien = diethylenetriamine) was synthesized under solvothermal conditions. It crystallizes in the tetragonal space group I4m2 with a = 7.8793(3) A, c = 24.9955(15) A, and V = 1551.80(13) A(3). The structure consists of anionic [Cu2Sn2S6](2-) layers extending in the (001) plane and protonated amine molecules as charge compensating ions sandwiched between the layers. The layered [Cu2Sn2S6](2-) anion is composed of a single layer of edge-sharing CuS4 tetrahedra which is joined above and below to straight chains constructed by corner-sharing SnS4 tetrahedra. The material is a semiconductor with an optical band gap of 1.51 eV. More interestingly, preliminary results demonstrate that the compound exhibits photoconductive properties with an increase of the conductivity by a factor of 3 when irradiated with UV light. Upon heating in an inert atmosphere the compound starts to decompose at about 256 degrees C.

Charge-density matching in organic–inorganic uranyl compounds

Abstract Single crystals of [C10H26N2][(UO2)(SeO4)2(H2O)](H2SeO4)0.85(H2O)2 (1), [C10H26N2][(UO2)(SeO4)2] (H2SeO4)0.50(H2O) (2), and [C8H20N]2[(UO2)(SeO4)2(H2O)] (H2O) (3) were prepared by evaporation from aqueous solution of uranyl nitrate, selenic acid and the respective amines. The structures of the compounds have been solved by direct methods and structural models have been obtained. The structures of the compounds 1, 2, and 3 contain U and Se atoms in pentagonal bipyramidal and tetrahedral coordinations, respectively. The UO7 and SeO4 polyhedra polymerize by sharing common O atoms to form chains (compound 1) or sheets (compounds 2 and 3). In the structure of 1, the layers consisting of hydrogen-bonded [UO2(SeO4)2(H2O)]2− chains are separated by mixed organic–inorganic layers comprising from [NH3(CH2)10NH3]2+ molecules, H2O molecules, and disordered electroneutral (H2SeO4) groups. The structure of 2 has a similar architecture but a purely inorganic layer is represented by a fully connected [UO2(SeO4)2]2− sheet. The structure of 3 does not contain disordered (H2SeO4) groups but is based upon alternating [UO2(SeO4)2(H2O)]2− sheets and 1.5-nm-thick organic blocks consisting of positively charged protonated octylamine molecules, [NH3(CH2)7CH3]+. The structures may be considered as composed of anionic inorganic sheets (2D blocks) and cationic organic blocks self-organized according to competing hydrophilic–hydrophobic interactions. Analysis of the structures allows us to conclude that the charge-density matching principle is observed in uranyl compounds. In order to satisfy some basic peculiarities of uranyl (in general, actinyl) chemistry, it requires specific additional mechanisms: (a) in long-chain-amine-templated compounds, protonated amine molecules interdigitate; (b) in long-chain-diamine-templated compounds, incorporation of acid–water interlayers into an organic substructure is necessary; (c) the inclination angle of the amine chains may vary in order to modify surface area of an organic substructure.

Charge density matching in organic-inorganic uranyl compounds

Abstract Single crystals of [C10H26N2][(UO2)(SeO4)2(H2O)](H2SeO4)0.85(H2O)2 (1), [C10H26N2][(UO2)(SeO4)2] (H2SeO4)0.50(H2O) (2), and [C8H20N]2[(UO2)(SeO4)2(H2O)] (H2O) (3) were prepared by evaporation from aqueous solution of uranyl nitrate, selenic acid and the respective amines. The structures of the compounds have been solved by direct methods and structural models have been obtained. The structures of the compounds 1, 2, and 3 contain U and Se atoms in pentagonal bipyramidal and tetrahedral coordinations, respectively. The UO7 and SeO4 polyhedra polymerize by sharing common O atoms to form chains (compound 1) or sheets (compounds 2 and 3). In the structure of 1, the layers consisting of hydrogen-bonded [UO2(SeO4)2(H2O)]2− chains are separated by mixed organic–inorganic layers comprising from [NH3(CH2)10NH3]2+ molecules, H2O molecules, and disordered electroneutral (H2SeO4) groups. The structure of 2 has a similar architecture but a purely inorganic layer is represented by a fully connected [UO2(SeO4)2]2− sheet. The structure of 3 does not contain disordered (H2SeO4) groups but is based upon alternating [UO2(SeO4)2(H2O)]2− sheets and 1.5-nm-thick organic blocks consisting of positively charged protonated octylamine molecules, [NH3(CH2)7CH3]+. The structures may be considered as composed of anionic inorganic sheets (2D blocks) and cationic organic blocks self-organized according to competing hydrophilic–hydrophobic interactions. Analysis of the structures allows us to conclude that the charge-density matching principle is observed in uranyl compounds. In order to satisfy some basic peculiarities of uranyl (in general, actinyl) chemistry, it requires specific additional mechanisms: (a) in long-chain-amine-templated compounds, protonated amine molecules interdigitate; (b) in long-chain-diamine-templated compounds, incorporation of acid–water interlayers into an organic substructure is necessary; (c) the inclination angle of the amine chains may vary in order to modify surface area of an organic substructure.

Inorganic–organic hybrid structures: Synthesis, structure and magnetic properties of a new iron oxalatoarsenate, [NH 3(CH 2)CH(NH 3)CH 3] 3[Fe 6(AsO 4) 2(HAsO 4) 6(C 2O 4) 3

A hydrothermal reaction of a mixture of iron oxalate, arsenic acid, 1,2-diaminopropane and water at 150 °C gave rise to a new three-dimensional iron oxalatoarsenate, [NH 3(CH 2)CH(NH 3)CH 3] 3[Fe 6(AsO 4) 2(HAsO 4) 6(C 2O 4) 3], I. Crystal data: hexagonal, space group = P-3c1, a = 13.9899 ( 12 ) , c = 14.936 ( 3 ) Å , V = 2531.6 ( 5 ) Å 3 . The structure consists of layers of vertex-sharing FeO 6 octahedral and AsO 4 tetrahedral units that form 12-membered apertures. The layers are connected together by the oxalate units, forming a uniform one-dimensional channel that is occupied by protonated amine molecules. Variable temperature powder XRD studies indicates that I loses crystallinity at ∼300 °C forming an amorphous phase that gives way to crystalline FeAsO 4 at ∼650 °C. Magnetic studies reveal that I is antiferromagnetic with T N = 31 K .

Zn(H 2PO 4) 4] 2− clusters and ∞[Zn 2(HPO 4) 3(H 2PO 4) 2] 4− layers in two new zinc phosphates templated by [H 2(4-amino-2.2.6.6-tetramethylpiperidine)] 2+ cations

Two zinc phosphates (ZnPO), [H 2(N 2C 9H 20)]·[Zn(H 2PO 4) 4] ( I) and [H 2(N 2C 9H 20)] 2·[Zn 2(HPO 4) 3(H 2PO 4) 2]·H 2O ( II), are synthesized under hydrothermal conditions using 4-amino-2.2.6.6-tetramethylpiperidine as organic template. I crystallizes in P 1 ¯ space group with a = 8.7398 ( 3 ) Å , b = 9.0417 ( 3 ) Å , c = 15.3822 ( 1 ) Å , α = 92.57 ( 1 ) ° , β = 89.76 ( 1 ) ° , γ = 102.16 ( 2 ) ° , V = 1187.1 ( 1 ) Å 3 and Z = 2 . Its structure, refined to R = 0.029 and R w = 0.076 for 4279 independent reflections, consists of [Zn(H 2PO 4) 4] 2− clusters held together through strong hydrogen bonds to form pseudo-layers between which the doubly protonated amine molecules are inserted. II is monoclinic, C2, with a = 27.57 ( 2 ) Å , b = 9.745 ( 5 ) Å , c = 14.08 ( 1 ) Å , β = 103.72 ( 5 ) ° , V = 3675 ( 4 ) Å 3 and Z = 4 ( R = 0.079 , R w = 0.268 , 2477 independent reflections). The structure of II consists of ∞[Zn 2(HPO 4) 3(H 2PO 4) 2] 4− inorganic (2D) layers built up from vertex-sharing [ZnO 4] and [(H 2/H)PO 4] tetrahedra. Organic cations and water molecules ensure the connection between these layers via hydrogen bonds. It is shown that numerous (1D), (2D), e.g., [H 2(N 2C 9H 20)] 2·[Zn 2(HPO 4) 3(H 2PO 4) 2]·H 2O, and (3D) (ZnPO) result from the condensation of the [Zn(H 2PO 4) 4] 2− clusters.

Solvothermal syntheses, crystal structures and properties of five new thioantimonates(III) containing the [Sb 4S 7] 2− anion

Five new thioantimonates have been synthesized in the presence of organic amines under solvothermal conditions and their structures determined by single-crystal X-ray diffraction. All of the compounds are layered and contain antimony–sulphide anions of stoichiometry [Sb 4S 7] 2−, but the structure of the anion formed is dependent on the amine used in synthesis. (H 3N(CH 2) 4NH 3)[Sb 4S 7] (1) contains [Sb 4S 7] 2− double chains directed along [010]. Weak interchain Sb–S interactions between neighbouring chains cause the double chains to pack into layers in the ab plane. In the [001] direction, the layers of double chains alternate with doubly protonated diaminobutane molecules to which the chains are hydrogen bonded. Compounds of general formula ( TH) 2[Sb 4S 7] ( T=CH 3(CH 2) 2NH 2 (2), (CH 3) 2CHNH 2 (3), CH 3(CH 2) 3NH 2 (4) and CH 3(CH 2) 4NH 2 (5)) adopt a more complex structure in which [Sb 3S 8] 7− units are linked by SbS 3 3− pyramids to form chains, which in turn are bridged by sulphur atoms to create sheets containing large heterorings. Pairs of such sheets form double layers of four atoms thickness that are stacked along [001]. Protonated amine molecules are located between anionic antimony-sulphide layers to which they are hydrogen bonded. Thermal analysis reveals that the decomposition temperature of materials containing [Sb 4S 7] 2− anions is dependent both on the structure of the anion, the lowest decomposition temperature being that of the low-dimensional phase (1) and on the identity of the amine, the decomposition temperature decreasing with an increasing number of carbon atoms and decreasing density.

Nanostructures in Uranium Oxocompounds

AbstractExamples of uranium-oxide-based nanostructures are considered, including 2D organic-inorganic nanocomposites and nanotubules. In nanocomposites, interfacial interactions between organic and inorganic substructures can be studied by charge-density matching principle. Application of this principle to uranyl compounds requires special attention since surface area of uranyl-based 2D units is higher than that of other inorganic oxysalts units (i.e. metal phosphates). The charge-density matching principle is, however, observed either through tail interdigitation (for long-chain monoamines) or incorporation of acid-water interlayers into organic substructure (for long-chain diamines). In some compounds, protonated amine molecules form cylindrical micelles that involves self-assembly governed by competing hydrophobic/hydrophillic interactions. The flexible inorganic complexes present in the reaction mixture could then form around cylindrical micelles to produce highly undulated 2D sheets or nanotubules.

Chiral open-framework uranyl molybdates. 3. Synthesis, structure and the C222 1 → P2 12 12 1 low-temperature phase transition of [C 6H 16N] 2[(UO 2) 6(MoO 4) 7(H 2O) 2](H 2O) 2

A new chiral 6:7 open-framework uranyl molybdate, [C 6H 16N] 2[(UO 2) 6(MoO 4) 7(H 2O) 2](H 2O) 2, has been synthesized by hydrothermal methods. The structure has been refined using single-crystal X-ray diffraction data collected at 20 and −127 °C. The 20 °C structure [orthorhombic, C222 1, a = 11.3045(14), b = 19.962(6), c = 24.416(5) Å, V = 5510(2) Å 3] has been refined to R 1 = 0.046 on the basis of 6093 unique observed reflections. The −127 °C structure [orthorhombic, P2 12 12 1, a = 11.211(4), b = 19.880(10), c = 24.421(8) Å, V = 5443(4) Å 3] has been refined to R 1 = 0.047 on the basis of 6951 unique observed reflections. The structures are based upon topologically identical frameworks of corner-sharing UO 7 pentagonal bipyramids and MoO 4 tetrahedra. The extra-framework H 2O groups and protonated triethylamine molecules reside in the framework cavities. In the C222 1 structure at 20 °C, H 2O and [C 6H 16N] + molecules filling the chiral channels along [0 0 1] are disordered, whereas, in the P2 12 12 1 structure at −127 °C, they are perfectly ordered. The symmetry difference between structures at 20 °C and −127 °C is the result of a C222 1 → P2 12 12 1 second order phase transition that involves ordering of extra-framework protonated amine molecules and H 2O groups, and distortion of the flexible [(UO 2) 6(MoO 4) 7(H 2O) 2] 2− uranyl molybdate framework. On the basis of measurements of intensities of reflections that violate absence conditions of C-centering cell, the temperature of the phase transition is estimated as −11 °C.

Solvothermal synthesis of an open-framework zinc chlorophosphate, [C 8N 4H 26][Zn 3Cl(HPO 4) 3(PO 4)], with a layer structure

A solvothermal reaction of ZnO, HCl, H 3PO 4, and N, N′(3-bisaminopropyl)-1,2-ethylenediamine (BAPEN) in diethyleneglycol at 160°C yields a new zinc chlorophosphate, [C 8N 4H 26][Zn 3Cl(HPO 4) 3(PO 4)], I. The structure comprises ZnO 4, ZnO 3Cl, HPO 4 and PO 4 tetrahedral units connected through their vertices giving rise to a layered structure with 10-membered apertures. The position of the Zn and P atoms gives rise to double-four ring like building unit with one Zn missing. The fully protonated amine molecules occupy the inter-lamellar region and interacts with the framework through N–H⋯O hydrogen bonds. Crystal data: M=792.85, orthorhombic, space group= Pca2 1 (no. 29), a=9.8410(2), b=15.0912(2), c=16.1220(4) Å, V=2394.32(8) Å 3, Z=4, ρ calc=2.199 g cm −3, μ(Mo Kα)=3.443 mm −1, R 1=0.0520, w R 2=0.1256 and S=1.054.