Octahedral Topology Research Articles

Crystal structures, Hirshfeld surfaces, Infrared, and XRF/XAFS studies of Long-chain 2D Lead-free Hybrid Perovskite NH3(CH2)9NH3MCl4 (M = Mn, Co, Cu)

Three 2D hybrid perovskite materials based on long chain diammonium NH3(CH2)9NH3MCl4 (M: Mn, Co, Cu) were prepared and characterized. The single crystal X-ray diffraction analysis showed that the novel compound NH3(CH2)9NH3MnCl4 (denoted C9Mn) crystallized in the monoclinic P21/c (Z=4) with the unit cell parameters a=7.405(3) Å, b=7.102(3) Å, c=29.463(11) Å, V=1538.07Å3. The NH3(CH2)9NH3CoCl4 (C9Co) was found to crystallize in the Triclinic space group P¯1 [Z=2; a = 7.3113(4) Å, b = 10.2373(5) Å, c = 12.4701(9) Å; α = 112.323(2)°, β = 92.441(2)°, γ = 93.452(3)°, V=859.68(9) Å3]. The C9Mn and C9Co layered structures contain alternating organic cations +NH3(CH2)9NH3+ and inorganic anions MCl42- (M: Mn, Co), where M is coordinated by six Cl atoms in the octahedral topology MnCl62−, and by four Cl atoms in the tetrahedral CoCl42− unassociated unit. The NH3(CH2)9NH3CuCl4 (C9Cu) crystal quality is not good to do the single crystal X-ray diffraction analysis on this salt. The Hirshfeld surface analyses are performed to compare the importance of attractive H…Cl/Cl…H and detractive H…H intercontacts in the two hybrid compounds. The vibrational modes of alkylenediammonium group of C9Cu, clearly observed in the infrared spectrum, are compared to that observed in the C9Mn and C9Co spectra, discussed based on theoretical group predictions. Analysis was performed at the X-ray absorption fine structure XAFS/XRF beamline to enhance the structure analysis for the salts C9Mn, C9Co and C9Cu.

Supramolecular approaches to metal–organic gels using ‘Chevrel-type’ coordination clusters as building units

A novel hexanuclear {Mn(6)} coordination complex with octahedral topology has been prepared and was subsequently used as a building unit for the construction of coordination polymers and metal-organic gels; the latter exhibit thixotropic behavior and reversible sol-gel phase transitions.

From Platonic Templates to Archimedean Solids: Successive Construction of Nanoscopic {V16As8}, {V16As10}, {V20As8}, and {V24As8} Polyoxovanadate Cages

Supramolecular coordination cages provide unique restricted inner cavities that can be exploited for molecular recognition purposes and catalysis. Their syntheses often involve complex self-organization processes and rely on the identification of preorganized, kinetically stable building units that provide ligand-accessible coordination sites. Here we report a highly effective protocol for the successive buildup of symmetrical nanoscopic polyoxometalate (POM) cages. Our methodology takes advantage of a supramolecular templating effect and utilizes the structure-directing influence of octahedral {X(x)(H(2)O)(6-x)} (X = Br(-), Cl(-); x = 2, 4, 6) assemblies that reside inside the hollow cluster shells and determine the arrangement of di- and tetranuclear vanadate units. The approach allows the preparation of a series of high-nuclearity POM cages that are characterized by {V(16)As(8)}, {V(16)As(10)}, {V(20)As(8)}, and {V(24)As(8)} core structures. In the latter cluster cage, the vanadium centers adopt a truncated octahedral topology. The formation of this Archimedean body is the direct result of the assembly of six square {V(4)O(8)} units that cap the vertices of the encapsulated Platonic {Cl(6)} octahedron. To the best of our knowledge, this {V(24)As(8)} cage is the largest hybrid vanadate cluster reported to date.

Manganese clusters derived from a 2,6-diacetylpyridine dioximato ligand: structure and magnetic study

Reactions of 2,6-diacetylpyridine dioxime (dapdoH₂) with Mn(NO₃)₂ or Mn(SO₃CF₃)₂ under a variety of conditions or co-ligands yield compounds with the formula [Mn₆O₂(OMe)₂(dapdo)₂(dapdoH)₄](X)₂ in which X = NO₃⁻ (1) or SO₃CF₃⁻ (2), [Mn₈O₂(dapdo)₆(NO₃)₂]·H₂O (3) and [Mn(dapdoH₂)(N₃)₂](n) (4). Compounds 1, 3 and 4 were structurally characterized and equivalent structures for 1 and 2 were inferred from spectroscopic and analytical results. Compounds 1 and 2 consist of hexanuclear Mn₂(II)Mn₄(III) complexes whereas 3 consists of an octanuclear Mn₆(II)Mn₂(III) cluster in which the manganese atoms exhibit a rare bicapped elongated octahedral topology. Compound 4 consists of a 1D system bridged by double end-on azido ligands. Variable temperature magnetic studies were performed between 2-300 K, confirming the ground state S = 5 for 1 and 2, S = 0 for 3 and ferromagnetic response for 4.

Di‐ and Dodeca‐Mitsunobu Reactions on C60 Derivatives: Post‐Functionalization of Fullerene Mono‐ and Hexakis‐Adducts

The diverse addition patterns of fullerene adducts make them attractive molecules, generating widespread application. Firstly, in terms of the latter, mono-adducts are extensively used in opto-electronic devices, owing to the fullerene core s capacity to accept up to six electrons. A second important application involves the utilization of fullerene adducts as structural components in material sciences. With their octahedral topology, Th-symmetric hexakis-adducts, are particularly intriguing. Amongst others, the latter have been used in C60-based star polymers. [5] In the aforementioned contexts, the relatively stable methanofullerene adducts obtained through Bingel cyclopropanation reactions are of particular interest. However, this functionalization approach—primarily developed by A. Hirsch and later optimized by Y.-P. Sun—suffers from two critical weaknesses. One is its effectively exclusive limitation to malonates; only a few exceptions are known. The other is a structural concern. In fact, quite often only the use of fairly simple malonates leads to the desired fullerene adducts in reasonable yields without tedious purifications. In order to overcome these problems, several groups have developed post-functionalizations of methanofullerene adducts. For instance, J.F. Nierengarten adapted the copper-mediated Huisgen 1,3dipolar cycloaddition reaction and applied it to the preparation of complex hexasubstituted fullerenes. A. Hirsch developed a selective deprotection–functionalization sequence of fullerene e,e,e-trisadducts. Our own group derivatized hexakis methanofullerenes by using several organometallic cross-coupling reactions. This article outlines the use of the Mitsunobu reaction as an efficient tool for the post-functionalization of fullerene monoand hexakis-adducts. The mild, virtually neutral conditions under which this dehydrative coupling of an alcohol with a pronucleophile (generally an acid) proceeds, prompted our group to use this reaction for the derivatization of fullerene adducts. To this end, we have prepared a C60 mono-adduct bearing 2 hydroxyl groups and a hexakisadduct with 12 hydroxyl functions. The preparation of hexakis compound 4 is depicted in Scheme 1. Ethylene glycol was mono-protected as tert-butyldimethylsilyl ether according to a previously reported procedure. Subsequent diesterification of malonic acid was performed in the presence of DCC in 97% yield. Hexakis-adduct 3 was then readily synthesized by using the optimized conditions

High-Spin Mn4 and Mn10 Molecules: Large Spin Changes with Structure in Mixed-Valence MnII4MnIII6 Clusters with Azide and Alkoxide-Based Ligands

The use has been explored of both azide (N3-) and alkoxide-containing groups such as the anions of 2-(hydroxymethyl)pyridine (hmpH), 2,6-pyridinedimethanol (pdmH2), 1,1,1-tris(hydroxymethyl)ethane (thmeH3) and triethanolamine (teaH3) in Mn cluster chemistry. The 1:1:1:1 reactions of hmpH, NaN3 and NEt3 with Mn(ClO4)(2).6H 2O or Mn(NO3)2.H2O in MeCN/MeOH afford [MnII4MnIII6O4(N3)4(hmp)12](X)2 [X=ClO4- (1), N3- (2)]. The [Mn10(mu4-O) 4(mu3-N3)4]14+ core of the cation has a tetra-face-capped octahedral topology, with a central MnIII6 octahedron, whose eight faces are bridged by four mu 3-N3- and four mu 4-O2- ions, the latter also bridging to four extrinsic MnII atoms. The core has Td symmetry, but the complete [MnII4MnIII6O4(N3)4(hmp)12]2+ cation has rare T symmetry, which is crystallographically imposed. A similar reaction of Mn(ClO4) (2).6H2O with one equiv each of NaN3, thmeH3, pdmH2, and NEt3 in MeCN/MeOH led to [MnII4MnIII6O2(N3)6(pdmH)4(thme)4] (3). Complex 3 is at the same oxidation level as 1/2 but its core is structurally different, consisting of two edge-fused [MnII2MnIII4(mu4-O)]14+ octahedra. Replacement of thmeH3 with teaH3 in this reaction gave instead [MnII2MnIII2(N3)4(pdmH)2(teaH)2] (4), containing a planar Mn 4 rhombus. Variable-temperature, solid-state dc and ac magnetization studies were carried out on 1-4 in the 5.0-300 K range. Complexes 1 and 2 are completely ferromagnetically coupled with a resulting S=22 ground state, one of the highest yet reported. Fits of dc magnetization vs field (H) and temperature (T) data by matrix diagonalization gave S=22, g=2.00, and D approximately 0.0 cm(-1) (D is the axial zero-field splitting parameter). In contrast, the data for 3 revealed dominant antiferromagnetic interactions and a resulting S=0 ground state. Complex 4 contains weakly ferromagnetically coupled Mn atoms, leading to an S=9 ground-state and low-lying excited states, and exhibits out-of-phase ac susceptibility signals characteristic of a single-molecule magnet. Theoretical values of the exchange constants in 1 obtained with density functional theory and ZILSH calculations were in good agreement with experimental values. The combined work demonstrates the synthetic usefulness of alcohol-based chelates and azido ligands when used together, and the synthesis in the present work of two "isomeric" MnIII6MnII4 cores that differ in spin by a remarkable 22 units.

Ferromagnetically-coupled decanuclear, mixed-valence [Mn 10O 4(N 3) 4(hmp) 12] 2+ [hmpH = 2-(hydroxymethyl)pyridine] clusters with rare T symmetry and an S = 22 ground state

The amalgamation of azide ( N 3 - ) and 2-(hydroxymethyl)pyridine (hmpH) ligands in Mn cluster chemistry has been further investigated. The reactions of hmpH, NaN 3 and Et 3N with Mn(NO 3) 2 · H 2O or Mn(ClO 4) 2 · 6H 2O in MeCN/MeOH affords [ Mn 4 II Mn 6 III O 4 ( N 3 ) 4 ( hmp ) 12 ] X 2 [ X = N 3 - ( 1 ) , ClO 4 - ( 2 ) ] . The Mn 10 cation has a tetra-face-capped octahedral topology. The central octahedron comprises six Mn 3+ ions, and the eight faces are bridged by four μ 3 - N 3 - ions and four μ 4-O 2− ions. The twelve bridging hmp − groups provide the peripheral ligation. This cation is the first example of μ 3-1,1,1 azido ligands bridging exclusively Mn 3+ ions, presaging a potentially rich new area of Mn III clusters with high spin values. The [Mn 10(μ 4-O) 4(μ 3-N 3) 4] 14+ core has T d symmetry, but the complete [ Mn 4 II Mn 6 III O 4 ( N 3 ) 4 ( hmp ) 12 ] 2 + cation has rare T symmetry, which is crystallographically imposed. Complexes 1 and 2 are completely ferromagnetically coupled, and have a resulting S = 22 ground state, one of the highest yet reported.

Synthesis, characterization and thermal decomposition study of some nickelnitro derivatives

Compounds with general formula [KxMyNi(NO2)6(H2O)n] (M=Ca, Sr, Ba, La;x=0–2; y=1, 2; n=0, 4) have been prepared and characterized by XRD, IR and EPR techniques. The structure of [Ba2Ni(NO2)6(H2O)2 ]2H2O has been determined by single crystal X-ray diffraction: space group P63 , a=7.525(1) A and c=14.516(1) A. The geometry of the compound consists of an intricate network of ligand-bridged coordination polyhedra, where the arrangement of the nickel(ii) ion exhibits a slightly distorted octahedral topology. The Ca, Sr and La phases have been indexed with a cubic cell, space group Pm3 m and cell parameters 10.354(5) A, 10.517(5) A and 10.571(8) A, respectively. Thermal decomposition of the different compounds using TG involves two consecutive steps: ligand pyrolysis and evolution of the inorganic residue. For the barium compound a third step appears which corresponds to the dehydration process. Further thermal treatments in tubular furnaces yield the formation of different mixed oxides of NiIII and NiIV at lower pressures of oxygen than those obtained from the ceramic method. Advantages of using the metallo–organic method can also be deduced from the SEM study.

Diazidobis(2,2'-bipyridine)nickel(II) Monohydrate

The compound [Ni(N 3 ) 2 (bipy) 2 ].H 2 O (I) (bipy = 2,2'-bipyridine) has been synthesized and its structure determined at room temperature. The coordination polyhedron of the Ni atom shows an octahedral topology with the two bipy and the two azido ligands in a cis arrangement. Two monomeric units form an outersphere dimer through hydrogen bonding with the water molecule to give the overall formula [Ni(bipy) 2 (N 3 ) 2 ] 2 .2H 2 O

Synthesis and Crystal Structure of MCu(edta).cntdot.4H2O: Molecular Precursors for MCuO2 (M = Ca, Sr, Ba)

The compounds MCu(edta){center_dot}4H{sub 2}O (edta = ethylenediaminetetraacetic acid; M = Ca, Sr, Ba) have been synthesized and characterized by analytical and spectroscopic techniques. The structures of the strontium and barium complexes have been determined by X-ray diffraction methods. Both compounds are isostructural and crystallize in the monoclinic system, space group P2{sub 1}/c, with four formula weights in a cell measuring a = 8.717(1), b = 10.568(3), c = 19.374(3) {angstrom}, {beta} = 100.39(1){degrees} for [SrCu(edta)(H{sub 2}O){sub 3}]{center_dot}H{sub 2}O and a = 8.818(1), b = 10.200(2), c = 19.737(2) {angstrom}, {beta} = 102.40(1){degrees} for [BaCu(edta)(H{sub 2}O){sub 3}]{center_dot}H{sub 2}O. The structures were refined to R = 0.046 (R{sub w}=0.051) and R = 0.034 (R{sub w}=0.037) for strontium and barium compounds, respectively. The geometry of the complexes consists of an intricate network of ligand-bridged coordination polyhedra, where the arrangement of the copper(II) ion exhibits a distorted octahedral topology. The geometry of the alkaline-earth metal cations is near to the bicapped trigonal prism, being bound to three water molecules and five oxygen atoms from different edta molecules. In comparison with the structural results of the [CaCu(edta)(H{sub 2}O){sub 2}]{center_dot}2H{sub 2}O, a change in the coordination polyhedron of calcium ion has been established. Thermal treatment ofmore » the complexes using TGA involves three consecutive steps: dehydration, ligand pyrolysis and the formation of inorganic residue. Taking these results into account, further thermal treatments have been performed in order to obtain MCuO{sub 2} phases (M = Ba, Sr, Ca). 33 refs., 6 figs., 4 tabs.« less

Trussarm—A Variable-Geometry-Truss Manipulator

An overview is given of recent work done in Canada on "trussarms"—truss structures of high aspect ratio and variable geometry, suitable for use as manipulator arms. Four possible truss topologies are compared, and the "standard" octahedral topology is shown to be superior, largely on the basis of simplified hinge design. A preliminary com parison is also made between the Canadarm (the current Shuttle manipulator arm) and two trussarms. Some of the key issues in the kinematics, dynamics and control of truss arms are discussed, and the paper closes with a brief description of laboratory trussarm models currently under development.