A one-pot synthesis of oligo(arylene-ethynylene)-molecular wires and their use in the further verification of molecular circuit laws

A convenient two-step, one-pot synthesis of oligo(arylene-ethynylene) (OAE) type molecular wires in yields of up to 70% via in situ desilylation of protected bis(alkynes) Me3SiC≡CArC≡CSiMe3 (Ar = 2,5-thienyl, 1,4-naphthylene, 9,10-anthrylene) and subsequent Sonogashira cross-coupling with S-(4-iodophenyl) ethanethiolate, 4-iodothioanisole, or 5-bromo-3,3-dimethyl-2,3-dihydrobenzo[b]thiophene is described. The in situ desilylation avoids the manipulation of the sensitive terminal dialkynes (HC≡CArC≡CH), whilst the general approach presented has some advantages over alternative synthetic strategies based on coupling of aryl dihalides (XArX) by avoiding the multi-step preparation and purification of the terminal alkynes S-(4-ethynylphenyl) ethanethiolate, 4-ethynylthioanisole and 5-ethynyl 3,3-dimethyl-2,3-dihydrobenzo[b]thiophene. The molecular conductance of the resulting thiolate or thioether functionalised OAE molecular wires has been determined using scanning tunneling microscope break junction (STM-BJ) methods. The trends in molecular conductance do not track simply with the degree of aromaticity of the molecular core despite the rather similar molecular lengths. Rather, the STM-BJ data are better correlated with the nature of the anchor group, highlighting the important role of electrode-molecule coupling on electron transport in a molecular junction. The experimental conductance data are in good agreement with recently described quantum circuit rules, further highlighting the potential for these relationships to be used as predictive tools in molecular electronics research

Rh(I)(2,5-norbornadiene)(biphenyl)(tris(4-fluorophenyl)phosphine): Synthesis, Characterization, and Application as an Initiator in the Stereoregular (Co)Polymerization of Phenylacetylenes

The synthesis of the Rh(I)-aryl complex, Rh(I)(nbd)(BiPh)(P(4-FC6H4)3) is reported and its efficacy as an initiator for the (co)polymerization of phenylacetylenes established. The X-ray crystal structure indicates that the complex adopts a slightly distorted square planar geometry whose purity and structure was also confirmed by elemental analysis and 1H, 13C, 31P, 19F, 103Rh, and 31P-103Rh{1H} HMQC NMR spectroscopy. We demonstrate that Rh(I)(nbd)(BiPh)(P(4-FC6H4)3) mediates the (co)polymerization of phenylacetylenes in a controlled fashion with initiation efficiencies as high as 0.98, as evidenced by the pseudo-first-order kinetic and number-average molecular weight versus conversion profiles. The ability to form well-defined AB diblock copolymers, in a stereoregular manner, by sequential monomer addition is verified in the block copolymerization of phenylacetylene with 4-fluorophenylacetylene with quantitative crossover efficiency, as determined by size exclusion chromatography

Hydrated alkali-B<inf>11</inf>H<inf>14</inf>salts as potential solid-state electrolytes

Metal boron-hydrogen compounds are considered as promising solid electrolyte candidates for the development of all-solid-state batteries (ASSB), owing to the high ionic conductivity exhibited bycloso- andnido-boranes. In this study, an optimised low cost preparation method of MB11H14·(H2O)n, (M = Li and Na) and KB11H14is proposed and analysed. The formation of the B11H14−salt is pH-dependent, and H3O+competes with small ionic radii cations, such as Li+and Na+, to produce a hydronium salt of B11H14−, which forms B11H13OH−upon heating. The use of diethyl ether to extract B11H14−salt from the aqueous medium during synthesis is an important step to avoid hydrolysis of the compound upon drying. The proposed method of synthesis results in LiB11H14and NaB11H14coordinated with water, whereas KB11H14is anhydrous. Hydrated LiB11H14·(H2O)nand NaB11H14·(H2O)nexhibit exceptional ionic conductivities at 25 °C, 1.8 × 10−4S cm−1and 1.1 × 10−3S cm−1, respectively, which represent some of the highest solid-state Li+and Na+conductivities at room temperature. The salts also exhibit oxidative stability of 2.1 Vvs.Li+/Li and 2.6 Vvs.Na+/Na, respectively. KB11H14undergoes a reversible polymorphic structural transition to a metastable phase before decomposing. All synthesisednido-boranes decompose at temperatures greater than 200 °C

Postsynthetic Bromination of UiO66 Analogues Altering Linker Flexibility and Mechanical Compliance

The data comprise experimental synthesis and characterisation of two porous materials, and their subsequent transformation by addition of bromine. The data also include the effect this modification of the material has on the mechanical properties, specifically the elastic modulus

Cation and anion selectivity of zwitterionic salicylaldoxime metal salt extractants

3-Dialkylaminomethyl substituted salicylaldoximes are efficient metal salt extractants, and, in contrast to related ``salen''-based reagents, are sufficiently stable to acid hydrolysis to allow commercial application in base metal recovery. Crystal structures show that metal salts are bound by a zwitterionic form of the reagents, with copper(II) nitrate, tetrafluoroborate and trifluoroacetate forming [Cu(L)(2)X(2)] assemblies in a tritopic arrangement with a trans-disposition of the anions outwith the coordination sphere. Copper(II) chloride, bromide and zinc(II) chloride form 1:1 assemblies, [Cu(L)X(2)], with the halides in the inner coordination sphere of the metal, leading to high chloride selectivity and very good mass transport efficiencies of CuCl(2). Introduction of the anion-binding sites into the salicylaldoxime extractants changes their cation selectivities; the ligands co-extract small amounts of Fe(III) along with Cu(II) from mixed metal aqueous feed solutions, an issue which will need to be addressed prior to industrial application

Polymerisation of a Cu(II) dimer into 1D chains using high pressure

Long intermolecular interactions are converted into covalent bonds when the complex [Cu-2(OH)(citrate)(Guanidine)2](-) is exposed to a pressure of 2.9 GPa; the coordination of the Cu centres changes from [4 + 1] to [4 + 2], but on increasing the pressure to 4.2 GPa some of the Cu centres become [4 + 1]-coordinate again

Locating gases in porous materials : cryogenic loading of fuel-related gases into a Sc-based metal-organic framework under extreme pressures

The authors thank the EPSRC for funding (EP/K033646) and the STFC for awarding beamtime at the Diamond Light Source.An alternative approach to loading metal organic frameworks with gas molecules at high (kbar) pressures is reported. The technique, which uses liquefied gases as pressure transmitting media within a diamond anvil cell along with a single-crystal of a porous metal-organic framework, is demonstrated to have considerable advantages over other gas-loading methods when investigating host-guest interactions. Specifically, loading the metal-organic framework ScBDC with liquefied CO at 2 kbar reveals the presence of three adsorption sites, one previously unreported, and resolves previous inconsistencies between structural data and adsorption isotherms. A further study with supercritical CH at 3-25 kbar demonstrates hyperfilling of the ScBDC and two high-pressure displacive and reversible phase transitions are induced as the filled MOF adapts to reduce the volume of the system. The maximum gas uptake of porous MOFs was explored by using gases as pressure-transmitting media in high-pressure single-crystal diffraction experiments. A study with supercritical CH at 3-25 kbar demonstrates that two high-pressure phase transitions are induced as the filled MOF adapts to reduce the volume of the system.PostprintPeer reviewe

Experimental Validation of Quantum Circuit Rules in Molecular Junctions

A series of diarylacetylene (tolane) derivatives functionalised at the 4- and 4′-positions by thiolate, thioether, or amine groups capable of serving as anchor groups to secure the molecules within a molecular junction have been prepared and characterised. The series of compounds have a general form X-B-X, Y-B-Y, and X-B-Y where X and Y represent anchor groups and B the molecular bridge. The single-molecule conductance values determined by the scanning tunnelling microscope break-junction method are found to be in excellent agreement with the predictions made on the basis of a recently proposed 'molecular circuit law', which states 'the conductance CH21136_IE1.gif of an asymmetric molecule X-B-Y is the geometric mean CH21136_IE2.gif of the conductance of the two symmetric molecules derived from it, CH21136_IE3.gif and CH21136_IE4.gif.' The experimental verification of the circuit law, which holds for systems in which the constituent moieties X, B, and Y are weakly coupled and whose conductance takes place via off-resonance tunnelling, gives further confidence in the use of this relationship in the design of future compounds for use in molecular electronics research. © 2021 Journal Compilation CH21136_TOC.jp

Data underpinning - Locating gases in porous materials: cryogenic loading of fuel-related gases into a Sc-based metal-organic framework under extreme pressures

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Regulation of Multistep Spin Crossover Across Multiple Stimuli in a 2-D Framework Material

We investigate the effects of a broad array of external stimuli on the structural, spin-crossover (SCO) properties and nature of the elastic interaction within the two dimensional Hofmann framework material [Fe(cintrz)2Pd(CN)4]·guest (cintrz = N cinnamalidene 4-amino-1,2,4-triazole; A·guest; guest = 3H2O, 2H2O, and Ø). This framework exhibits a delicate balance between ferro- and antiferro-elastic interaction characters; we show that manipulation of the pore contents across guests = 3H2O, 2H2O, and Ø can be exploited to regulate this balance. In A·3H2O, the dominant antiferroelastic interaction character between neighboring FeII sites sees the low-temperature persistence of the mixed spin-state species {HS−LS} for {Fe1−Fe2} (HS = high spin, LS = low spin). Elastic interaction strain is responsible for stabilizing the {HS−LS} state and can be overcome by three mechanisms: (1) partial (2H2O) or complete (Ø) guest removal, (2) irradiation via the reverse light-induced excited spin-state trapping (LIESST) effect (λ = 830 nm), and (3) the application of external hydrostatic pressure. Combining experimental data with elastic models presents a clear interpretation that while guest molecules cause a negative chemical pressure, they also have consequences for the elastic interactions between metals beyond the simple chemical pressure picture typically proposed.Manan Ahmed, Katrina A. Zenere, Natasha F. Sciortino, Kasun S. A. Arachchige, Gemma F. Turner, Jace Cruddas, Carol Hua, Jason R. Price, Jack K. Clegg, Francisco Javier Valverde-Mun, oz, Jose A. Real, Guillaume Chastanet, Stephen A. Moggach, Cameron J. Kepert, Benjamin J. Powell, and Suzanne M. Nevill