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Many naturally occurring systems show us how multi-component supramolecular assemblies can generate useful functional behaviour. In this article the problems and limitations associated with achieving such behaviour in artificial multi-component assemblies is discussed, together with two examples of functions in artificial supramolecular assemblies based on (i) host-guest chemistry in cavities of cages, and (ii) light-harvesting in multi-chromophore arrays. Important challenges for the future are summarised.

In contrast to most common electrochemiluminescence (ECL) techniques that require either an additional reagent or continuous pulsing between oxidative and reductive potentials, here a fluorescent polymer of intrinsic microporosity (PIM-1) is shown to exhibit intrinsic ECL without the need for a co-reactant at positive applied potentials and as a function of pH. PIM-1 is known to possess high microporosity (based on its rigid and contorted molecular structure) and excellent fluorescence properties. By depositing a nanoparticulate form of the PIM-1 material onto tin-doped indium oxide, we achieve a hierarchically porous deposit with good sustained ECL activity in aqueous media. The mechanism for this reagentless ECL is suggested to be linked to reactive oxygen species produced at positive potentials and discussed in terms of potential analytical applications.

Trimethylsilyl-protected dialkynes incorporating azobenzene linker groups, Me3SiC ≡ CRC ≡ CSiMe3 (R = azobenzene-3,3′-diyl, azobenzene-4,4′-diyl, 2,5-dioctylazobenzene-4,4′-diyl), and the corresponding terminal dialkynes, HC ≡ CRC ≡ CH, have been synthesized and characterized. The CuI-catalyzed dehydrohalogenation reaction between trans-[Ph(Et3P)2PtCl] and the deprotected dialkynes in a 2:1 ratio in iPr2NH/CH2Cl2 gives the platinum(II) diynes trans-[Ph(Et3P)2PtC ≡ CRC ≡ CPt(PEt3)2Ph], while the dehydrohalogenation polycondensation reaction between trans-[(nBu3P)2PtCl2] and the dialkynes in a 1:1 molar ratio under similar reaction conditions affords the platinum(II) polyynes, [-Pt(PnBu3)2-C ≡ CRC ≡ C-]n. The materials have been characterized spectroscopically, with the diynes also studied using single-crystal X-ray diffraction. The platinum(II) diynes and polyynes are all soluble in common organic solvents. Optical-absorption measurements show that the compounds incorporating the para-alkynylazobenzene spacers have a higher degree of electronic delocalisation than their meta-alkynylazobenzene counterparts. Reversible photoisomerization in solution was observed spectroscopically for the alkynyl-functionalized azobenzene ligands and, to a lesser extent, for the platinum(II) complexes. Complementary quantum-chemical modeling was also used to analyze the optical properties and isomerization energetics.

Water-insoluble phosphine-surface-stabilised rhodium clusters [ Rh 6 ( PR 3 ) 6 H 12 ] [ BAr 4 F ] 2 (R = cyclohexyl, Ar F = (3,5-CF 3 ) 2 C 6 H 3 ) can be immobilised onto suitable glassy carbon, graphite, or tin-doped indium oxide (ITO) electrode surfaces. When immersed into alcohol/aqueous electrolyte media, they display stable voltammetric responses consistent with the formation of organic microdroplet | aqueous electrolyte two-phase conditions which are similar to those observed in corresponding anhydrous (CH 2 Cl 2 ) solution phase. This results in an electrode surface that is straightforwardly modified with cluster materials that can uptake or release dihydrogen depending on their redox-state. The results presented herein lead to a slight re-evaluation of the originally reported hydrogen store and release cycle for this system.

H Box: The clusters [Rh6(PR3)6H 12][BArF4]2 (R = cyclohexyl, iPr; see scheme, pink Rh, orange P) reversibly take up two molecules of H2 under ambient conditions (1 atm H2, 298 K) to give discrete octahedral clusters surrounded by 16 hydride ligands. (Figure Presented). © 2005 Wiley-VCH Verlag GmbH and Co. KGaA.

A series of trimethylsilyl-protected monoalkynes (Me3SiC≡C-R) and bis-alkynes (Me3 SiC≡C-R-C≡CSiMe3) incorporating carbazole spacer groups (R = carbazole-2-yl, carbazole-3-yl, carbazole-2,7-diyl, N-(2-ethylhexyl)carbazole-2,7-diyl, carbazole-3,6-diyl, N-(2-ethylhexyl)carbazole-3,6-diyl), together with the corresponding terminal monoalkynes (H-C≡C-R) and bis-alkynes (H-C≡C-R-C≡C-H), have been synthesized and characterized. The CuI-catalyzed dehydrohalogenation reaction between trans-[(Ph)(Et3P)2PtCl], trans-[(Et3P)2PtCl2], and trans-[(PnBu3)2PtCl2] and the terminal alkynes in iPr2NH/CH2Cl2 affords a series of Pt(II) mono- and diynes, while the dehydrohalogenation polycondensation reactions with trans-[(PnBu3)2PtCl2] under similar reaction conditions yields four Pt(II) poly-ynes of the form trans-[(PnBu3)2Pt-C≡C-R-C≡C-]n. The acetylide-functionalized carbazole ligands and the mono-, di-, and polynuclear Pt(II) σ-acetylide complexes have been characterized spectroscopically, with a subset analyzed using single-crystal X-ray diffraction. The Pt(II) mono-, di-, and poly-ynes incorporating the carbazole spacers are soluble in common organic solvents, and solution absorption spectra show a consistent red-shift between the 2- and 2,7- as well as 3- and 3,6-carbazole complexes. Computational modeling is used to explain the observed spectral shifts, which are related to the enhanced electronic delocalization in the latter systems. These results also indicate that the inclusion of carbazole-2,7-diyl units into rigid-rod organometallic polymers should enhance electronic transport along the chains.

Spin transitions are a spectacular example of molecular switching that can provoke extreme electronic and structural reorganizations in coordination compounds. A new 3D cyanoheterometallic framework, [Fe(pz)(Au(CN)2)2], has been synthesized in which a highly cooperative spin crossover has been observed at 367 and 349 K in heating and cooling modes, respectively. Mössbauer spectroscopy revealed a complete transition between the diamagnetic and paramagnetic states of the iron centres. The low-spin-to-high-spin transition induced a drastic structural distortion involving a large one-directional expansion (ca. 10.6%) and contraction (ca. 9.6%) of the lattice. Negative thermal expansion along the c axis was detected below and above the transition temperature.

Crystals of [Co(diox)2(4-NO2-py)2] (1) and [Co(diox)2(4-CN-py)2] (2) where diox are the o-dioxolene 3,5-di-tbutylsemiquinonate(SQ•-) and/or 3,5-di-t-butylcatecholate (Cat2-) ions, 4-NO2-py is 4-nitro-pyridine, 4-CN-py is 4-cyano-pyridine,are among the few known crystals presenting both thermally-induced and photoinduced ls-[M+3(SQ•-)(Cat2-)]↔hs-[M2+(SQ•-)2] valencetautomeric interconversion (VTI). In 2, the thermal-induced VTI is cooperative, characterizing an abrupt conversion, and in 1it is non-cooperative. In this work, crystals of [Co(diox)2(4-NO2-py)2]·benzene (1BZ), [Co(diox)2(4-NO2-py)2]·toluene (1TL),[Co(diox)2(4-CN-py)2]·benzene (2BZ) and [Co(diox)2(4-CN-py)2]·toluene (2TL) have been prepared and analyzed by single crystalX-ray diffraction in order to investigate how solvation modulates thermally-induced VTI. Crystallographic data was also successfullyused together with two-state equilibrium equation to estimate ΔH° and ΔS° VTI thermodynamic parameters. The solvate crystals,like the non-solvated ones, present essentially reversible thermally-induced VTI. 1TL crystal presents the same monoclinicsymmetry and the same intermolecular hydrogen-bonded network of 1 and both present a non-cooperative thermal-induced VTI.1BZ crystal has triclinic symmetry and present a cooperative VTI with a thermal hysteresis of ~30 K. In contrast to 2, thermallyinducedVTI in 2BZ and 2TL is non-cooperative despite the fact that 2, 2BZ and 2TL crystals exhibit the same monoclinic symmetryand the same intermolecular hydrogen-bonded network. In 2BZ and 2TL benzene and toluene molecules as well as thet-butyl groups of the o-dioxolene molecules convert gradually from being dynamically disordered at about 300 K to a static disorderstate below 150 K. The layer separation distance of interacting [Co(diox)2(4-X-py)2], X=CN and NO2, molecules in all solvate crystalsis ~15 Å whereas in the 2, which presents cooperative VTI, it is ~12 Å. An order-disorder component might account to the stabilizationof the metastable hs-Co2+ state in 2BZ and in 2TL but no disorder was found in the 1TL crystals. Therefore, the lack ofcooperativity in the thermally-induced VTI in these crystals seems to be due to the large distance between the layers of interactingmolecules. Cooperativity in the VTI of 1BZ crystal is likely to be related with the unique molecular bond scheme network that connectsneighboring active [Co(diox)2(4-NO2-py)2] molecules through the o-dioxolene oxygen atoms bonded directly to the Co ion.

The formation and chemistry of flavin–indole charge transfer (CT) complexes has been studied using a model cationic flavin. The ability to form a CT complex is sensitive to indole structure as gauged by spectroscopic, kinetics and crystallographic studies. Single crystals of sufficient quality of a flavin–indole CT complex, suitable for X-ray diffraction, have been grown, allowing solid-state structural analysis. When CT complex formation is conducted in d4-methanol, an efficient and synthetically useful C-3 indole deuteration is observed.

Ionic transport (for applications in nanofluidics or membranes) and "ionic diode" phenomena in a zeolitic imidazolate framework (ZIF-8) are investigated by directly growing the framework from aqueous Zn2+ and 2-methylimidazole as an "asymmetric plug" into a 20 μm diameter pore in a ca. 6 μm thin poly-ethylene-terephthalate (PET) film.

Treatment of the quadruply bonded dimolybdenum complexes [Mo2(μ-O2CCF3)4] (1), [Mo2(μ-O2CCH3)4] (2) and [Mo2(μ-O2CBut)4] (3) with the N-heterocyclic carbenes (NHCs), L (La = IPr, Lb =IMes, Lc = IiPr2Me2 and Ld = IEt2Me2), respectively, results in the formation of a series of 1:1 and 1:2 adducts: In the case of the larger, and more sterically demanding, carbene ligands i.e. La and Lb, coordination occurs exclusively axially with respect to the [Mo2] complexes and only once in the case La, [Mo2(μ-O2CR)4(La)] (R = Me, tBu and CF3) (1a, 2a and 3a), and twice in the case of Lb, [Mo2(μ-O2CCF3)4(Lb)2] (2b). For the less sterically demanding carbene ligands (Lc and Ld) coordination to the [Mo2] core occurs twice, with a transoidal dis-tribution about the [Mo2] unit and is exclusively in equatorial positions, resulting in partial displacement of two of the bridg-ing {μ-O2CR} ligands in each complex. In the case of complexes 1a, 2a, 3a, 2b, [Mo2(μ-OTFA)2(OTFA)2(Lc)2] (1c), [Mo2(μ-OTFA)2(OTFA)2(Ld)2] (1d) [Mo2(μ-OAc)2(OAc)2(Ld)2] (2d) the solid state molecular structures have been unambiguously characterised by single crystal X-ray diffraction. As part of our study into the reactivity of NHC ligands with [Mo2(μ-O2CCH3)4], the heteroleptic NHC adduct [Mo2(μ-OAc)2Cl2(Ld)2] (5) formed from the reaction of complex 2d with trimethylsi-lylchloride has also been isolated and structurally characterized using single crystal x-ray diffraction. As part of our study the Mo-Mo stretching frequencies of these complexes have been analyzed by Raman spectroscopy

The reaction of a new ligand, ethyl 2,6-diphenylisonicotinate (EtO(2)C-CAN boolean AND C-H(2)), with K(2)PtCl(4) in acetic acid affords the monocyclometalated complex [{(EtO(2)C-CANAC-H)Pt(mu-Cl)}(2)] (1), which transforms to the bis-cyclometalated derivative [Pt(EtO(2)C-C boolean AND N boolean AND C)(DMS0)] (2) when heated in hot DMSO. Complex 2 is the precursor for preparing a new series of neutral mononuclear bis-cyclometalated complexes [Pt(EtO(2)C-CAN boolean AND C)(L)] (L = tht (3), PPh(3) (4), CN-(t)Bu (5), py (6), py-tBu (7), py-NH(2) (8), py-CN (9), py-CONH(2) (10)). These new complexes have been characterized spectroscopically, and structures of 2-10 have been determined crystallographically. Within each crystal structure the individual molecules pack in a head-to-tail arrangement. Noncovalent interactions, including pi center dot center dot center dot pi; C-H center dot center dot center dot O, C-H center dot center dot center dot N, N-H center dot center dot center dot Pt, N-H center dot center dot center dot pi, C-H center dot center dot center dot O, and N-H center dot center dot center dot O, contribute significantly to the supramolecular structures displayed by these complexes in the solid state. All complexes display UV-vis absorptions in dichloromethane solution. Excitation and emission studies as well as lifetime measurements are described and can be correlated to the solid-state structures of the complexes. DFT and TDDFT computational studies have been performed on 5 and 8 which support the conclusions drawn from the photophysical studies.

The new cobalt(II) phosphine oxide complexes Co(Cy(3)PO)(2)Cl(2) (1), Co(Cy(3)PO)(2)Br(2) (2), Co(Cy(3)PO)(2)I(2) (3), Co(Ph(2)CyPO)(2)Cl(2) (4), Co(Ph(2)CyPO)(2)Br(2) (5), Co(Ph(2)CyPO)(2)I(2) (6), Co(Ph(2)EtPO)(2)Br(2) (7), Co(CY(3)PO)(2)(NCS)(2) (8) and Co(Cy(3)PO)(2)(NO(3))(2) (9) have been prepared mainly by the reaction of anhydrous CoX(2) (X = Cl, Br, I, NCS, NO(3)) with the appropriate phosphine oxide. The complexes were characterised by single-crystal X-ray crystallography supported by IR and UV-Vis absorption spectroscopy. The structural analyses show that the cobalt(II) centre adopts a distorted tetrahedral coordination geometry except for 9 which displays an octahedral geometry. Systematic structural features of these complexes are explained within this paper. (C) 2011 Elsevier Ltd. All rights reserved.

The reaction between 2- and 3-thienyl-substituted 1,3-butadiynes and the electron-deficient osmium cluster Os3H2(CO)10 yields trinuclear coordination products, associated with transformations of the diacetylene ligands. Depending on the heteroaryl end groups, osmium clusters with both a closed and open Os-triangle core were formed. The reaction between Os3H2(CO)10 and 1,4-bis(2-thienyl)butadiyne yielded [Os3(-H)(CO)10{(-n-(C 4H3S)(C8H4S)}] (1) and [Os 3(-H)(CO)10{(3-n2- n1-n1-(SC7H4)C(SC 4H3)}] (2), whereas in the analogous case of 1,4-bis(3-thienyl)butadiyne the main coordination product was found to be [Os3(-H)(CO)10{(-n-(C4H 3S)(C8H4S)}] (3). Compounds 1-3 were stable in air, but lost carbon monoxide upon prolonged heating. Thermal decarbonylation of 1 under N2 yielded a mixture of [Os3(-H)(CO) 9{(3-n3-(C4H 3S)(C8H4S)}] (4) and [Os3(-H) 2(CO)9{(3-n1- n1-(C4H3S)(C8H3S)}] (5). Thermal decarbonylation of 2 yielded [Os3(-H)(CO) 9{(3-n3-(C4H 3S)(C8H4S)}] (6), while thermal decarbonylation of 3 yielded [Os3(-H)(CO)9{(3- n3-(C4H3S)(C8H4S)}] (7). A reaction involving 3 with CF3COOH affords as the main cluster product the known cluster [Os3(-H)(CO)10(O 2CF3)] (8) and, unusually, permits the isolation and characterization of the novel organic molecule [(C4H 3S)(C8H4S)(OCF3)] (9) cleaved from the parent cluster. The structures of the new compounds were established by single-crystal X-ray studies and spectroscopic methods and supported by density functional theory.

The pentadentate ligand N,N′-bis(2-hydroxyphenyl)-pyridine-2,6-dicarboxamide (POPYH4) has been used to prepare a variety of new complexes [HNEt3]2[Zn4Cl(POPYH)3] (2), [HNEt3][PdCl(POPYH2)] (3), [HNEt3][Ni(POPYH)] (4) and K[Ni(POPYH)] (5) which show the versatility of this multidentate ligand. The complexes have been characterised spectroscopically and their molecular and crystal structures have been determined by single crystal X-ray diffraction techniques. In these complexes the ligand exhibits different modes of coordination towards different transition metal ions. The structure of triethylammonium salt of the Zn(II) dianion 2 consists of an unusual tetra-zinc core supported by three POPYH ligands each one of which links two adjacent zinc centres through two oxygen and two nitrogen donor atoms. The salt of the square planar Pd(II) anion 3 contains one POPYH2 ligand which coordinates in a tridentate fashion through the two deprotonated amido groups and by the central pyridine nitrogen donor. The two Ni(II) salts 4 and 5 contain the same [Ni(POPYH)]− anion in which the square planar Ni(II) centre is chelated by a POPYH ligand through the two deprotonated amido nitrogen atoms, the pyridine nitrogen and a deprotonated hydroxyl group.

The stable benzylazido-boronate ester 1 is presented as an example of a dual-functional linker that allows the synthetically valuable boronate motif to be clicked onto other molecules under mild conditions. The utility of the azido-boronate motif as a modular building block is demonstrated in the rapid synthesis of drug-like structures employing sequential catalytic azide–alkyne cycloaddition and Suzuki coupling reactions.

Reaction of the [Rh(η5-C5Me5)(NCMe)3]2+ (1) dication with the hexaosmium [Os6(CO)17]2− (2) dianion leads to the initial formation of [Os6(CO)17Rh(η5-C5Me5)] (3). This cluster readily adds CO to form [Os6(CO)18Rh(η5-C5Me5)] (4) which has been characterised crystallographically. 3 also adds dihydrogen to give [Os6H2(CO)17Rh(η5-C5Me5)] (5) and undergoes a substitution reaction with PPh3 to form [Os6(CO)16(PPh3)Rh(η5-C5Me5)] (6). With the [Ru6(CO)18]2− (7) dianion, [Rh(η5-C5Me5)(NCMe)3]2+ (1) reacts to form three mixed-metal clusters [Ru5(CO)15Rh(η5-C5Me5)] (8), [Ru6(CO)18Rh(η5-C5Me5)] (9) and [Ru6(CO)18Rh2(η5-C5Me5)2] (10). The clusters have been characterised spectroscopically and the structures of 8 and 10 have been confirmed crystallographically. The cluster 8 undergoes a substitution reaction with P(OMe)3 to form the disubstituted product [Ru5(CO)13(P(OMe)3)2Rh((η5-C5Me5)] (11) which has also been characterised crystallographically.

New Cu(II) complexes have been prepared and characterised via single crystal X-ray diffraction studies, EPR spectroscopy, elemental analysis and high resolution mass spectrometry. In all cases 1:2 (copper to ligand) stoichiometric complexes were isolated. The homogeneous Cu(II) complexes were tested for the asymmetric Henry reaction. Conversions in excess of 70% were obtained with enantioselectivities in the range 0–78%. Heterogeneous Cu(II) catalysts have been prepared. In these cases high conversions were obtained. However, after prolonged reaction time the main product observed was 1,3-dinitro-2-phenyl propane. The formation of this product can be curtailed by both decreasing the catalyst loading and employing shorter reaction times.

For the case of the commercially available metal-organic framework (MOF) structure BasoliteTM F300 or Fe(BTC) with BTC = benzene-1,3,5-tricarboxylate, it is shown that the Fe(III/II) electrochemistry is dominated by reductive dissolution rather than ion insertion (which in marked contrast is dominating the behaviour of Fe(III/II) open framework processes in Prussian blues). Solid Fe(BTC) immobilised onto graphite or platinum working electrodes is investigated and it is shown that well-defined and reversible Fe(III/II) reduction responses occur only on platinum and in the presence of aqueous acid. The process is shown to follow a CE-type mechanism involving liberation of Fe(III) in acidic media, in particular for high concentrations of acid. Effective electrocatalysis for the oxidation of hydroxide to O2 (anodic water splitting) is observed in alkaline aqueous media after initial cycling of the potential into the reduction potential zone. A mechanism based on a MOF-surface confined hydrous iron oxide film is proposed. Keywords: MOF, Voltammetry, Prussian blue, Reductive dissolution, Host guest electrochemistry, Water splitting, Sensor

P NMR chemical shifts of the compound are in the same range as the experimental values. For this type of complex, the LDA/SDD method is appropriate for IR predictions whereas the OPBE/IGLO-II method is appropriate for NMR predictions. The activation energy and reaction energy of the intramolecular hydrogen transfer coupled with the structural change of the transition metal framework were estimated at the PW91/SDD level to be 110.32 and ‒0.14 kcal/mol respectively.

With the increase in interest in photocrystallographic experiments, the use of light-emitting diodes (LEDs) provides an alternative, low-budget light source (by comparison to lasers) and allows photocrystallographic experiments to be carried out readily. Here the design of an LED array device suitable for use in single-crystal X-ray diffraction experiments is reported, and the experimental methodology used for determining the structures of metastable species is described.

The reaction of 15–18 membered benzodiazacrown ethers with salicylaldehyde afforded n-membered O2N2-donor macrocyclic ligands mounted with 1,3-diazacyclohexane subrings (1–4) in high yields. The products were characterized by FT-IR, 1H, 13C NMR spectroscopy, elemental analyses, and single crystal X-ray studies. The solid state structures revealed strong intramolecular hydrogen bonding between the pendant phenolic group and the tertiary nitrogen of the corresponding macroring.

The reactions of [Os-3(mu-CO)(CO)(9){mu(3)-eta(2)-Me3SiCCC CSiMe3}] with phosphorus donor ligands (PPh3, PEt3, P(OEt)(3), PHPh2 and a diphosphine; Ph2PCH2PPh2 (dppm)) afford carbonyl mono-substitution products [Os-3(mu-CO)(CO)(8){mu(3)-eta(2)-Me3SiC2C2SiMe3}] even in the case of the bidentate phosphine dppm. All the complexes have been characterized by IR and multinuclear NMR spectroscopy and for 2 (L = PPh3), 3 (L = PEt3), 4 (L = P(OEt)(3)) and 5 (L = eta(1)-dppm) the structures have been confirmed by single- crystal X- ray analysis. The structural analyses show that in all four clusters the substitution has occurred at one of osmium equatorial sites that is sigma- bonded to the mu(3)-eta(2)-alkyne. (C) 2009 Published by Elsevier B.V.

Simultaneous bipotentiostatic electro-deposition of gold onto two closely spaced platinum disc electrodes produces paired gold electrode junctions. The potential applied during gold deposition onto the two electrodes is chosen to be slightly offset (by 0.5 mV) to allow for an automatic cut-off mechanism to control the resulting gap size for the paired diffusion junction. The key parameter controlling the gap size is identified as the deposition potential (in relation to the reversible potential for gold deposition) and paired gold electrode junctions are prepared reproducibly from ca. 5 μm estimated gap size (−250 mV overpotential during deposition) down to approximately 300 nm estimated gap size (−20 mV overpotential during deposition). The resulting paired junction electrodes are characterized for the reduction of alizarin red S and it is shown that for junctions with ca. 300 nm gap size: (i) the low concentration sensitivity is improved to allow sub-micromolar concentration measurements and (ii) due to faster mass transport within the smaller gap a transition from reversible to irreversible electron transfer can be observed.

This paper reports the development of a prototype environmental gas cell, capable of allowing a single crystal to be exposed to different gas mixtures and/or a vacuum whilstin situon the single-crystal diffractometer. The design and application of the cell to the study of a single crystal in the presence of sulfur dioxide are described.

A chemically modified carbon ceramic composite electrode (CCE) containing Dichloro{(8, 9-dimethyl-dipyridio [2,3-a;2′,3′-c] phenazine-κ2-N,N′) bis(triphenylphosphine-κ-P)}ruthenium (II) complex which synthesized newly was constructed by the sol–gel technique. Electrochemical behavior and stability of modified CCE were investigated by cyclic voltammetry. The electrocatalytic activity of CCE was investigated and showed a good effect for oxidation of hydrazine in phosphate buffer solution (PBS). A linear concentration range of 6 μM to 1.2 mM of hydrazine with an experimental detection limit of 1 μM of hydrazine was obtained. The diffusion coefficient of hydrazine and its catalytic rate constant for electrocatalytic reaction along with the apparent electron transfer rate constant (ks) and transfer coefficient (α) were also determined. The modified carbon ceramic electrode doped with this new Ru-complex showed good reproducibility, short response time (t 3 month) and especially good surface renewability by simple mechanical polishing. The results showed that this electrode could be used as an electrochemical sensor for determination of hydrazine in real water samples used in Fars Power Plant Station, including its heat recovery steam generator (HRSG) water (at different operational condition), cooling system and clean waste water.

The synthesis and characterization of the thieno[3,2-b]thiophene and dithieno[3,2-b:2′,3′-d]thiophene containing platinum(II) poly-ynes and their molecular precursors is described and the electronic structure is established by absorption, luminescence and photoinduced absorption measurements. A comparison of the electronic structure of the fused and the nonfused oligothiophenes, thieno[3,2-b]thiophene, dithieno[3,2-b:2′,3′-d]thiophene, 2,2′-bithiophene, and 2,2′:5′,2′′-terthiophene incorporated in platinum(II) poly-ynes is reported. We find the singlet S1 and triplet T1 and Tn excited states to be at higher energy in thin films made from the fused systems than from the nonfused systems. For ligands with the same number of rings, we attribute this to the decreased number of double bonds in the fused system and to the presence of an additional sulfur atom in spacers with the same number of double bonds.

The crystal structures of phenylpropylpyridine-N-oxide and N-methyl-phenylpropylpyridinium iodide are compared, revealing that hydrogen bonding with the solvent molecule plays an important role in the N-oxide compound, whilst electrostatic interactions are predominant in controlling the solid-state orientation of the N-methylated compound. Fluorescence spectroscopy and NOESY indicate that in contrast to the previously reported pyridinium iodide, the N-oxide is not subject to intramolecular pi-stacking, as judged by excimer emission and a lack of corresponding cross peaks, respectively.

CuCN reacts with RLi and TMPLi (TMP = 2,2,6,6-tetramethylpiperidide) to give Gilman-type cuprates R(TMP)CuLi·nL (R = Ph, n = 3, L = THF 2; R = Me, n = 1, L = TMEDA 3). 3 and 3·LiCN have been tested in directed ortho cupration with data suggesting enhanced efficiency for Lipshutz-type 3·LiCN; competition between Lipshutz- and Gilman-type formulations is rationalized by DFT methods.

The reaction of 2 equiv. of [Os3(CO)10(MeCN)2] with R–C C–L–C C–R (R = H, L = (C4H2S); R = SiMe3, L = (C4H2S–C4H2S), (C4H2S–C4H2S–C4H2S), (C4H2S)–(C14H8)–(C4H2S)) affords the series of linked clusters [{Os3(CO)10}(HC C(C4H2S)C CH){Os3(CO)10}] (1), [{Os3(CO)10}(Me3SiC C(C4H2S–C4H2S)C CSiMe3){Os3(CO)10}] (2), [{Os3(CO)10}(Me3SiC C(C4H2S–C4H2S–C4H2S)C CSiMe3){Os3(CO)10}] (4) and [{Os3(CO)10}(Me3SiC C(C4H2S)–(C14H8)–(C4H2S)C CSiMe3){Os3(CO)10}] (6) as the major products. The complexes have been characterised by a range of spectroscopic methods and, in the case of 1 and 2 by single crystal X-ray crystallography. The alkyne groups cap the osmium triangles in the expected μ3-η2-||-bonding mode and each triangle is coordinated by nine terminal and one μ2-carbonyl group. Solution UV–Vis spectra of the complexes were similar to those observed for the free ligands consistent with there being little delocalisation between the cluster units and the thiophene groups.

Sequential reaction of HTMP (= 2,2,6,6-tetramethylpiperidine) with nBuLi and Et2Zn affords unsolvated polymer chains of EtZn(micro-Et)(micro-TMP)Li 6. The scope of this reagent in directed ortho metalation (DoM) chemistry has been tested by its reaction with N,N-diisopropylnaphthamide in THF to give EtZn(micro-C10H6C(O)NiPr2-2)2Li.2THF 7. Data reveal that 6 has undergone reaction with 2 equiv of aromatic tertiary amide and imply that it exhibits dual alkyl/amido basicity. DFT calculations reveal that direct alkyl basicity is kinetically disfavored and instead point to a stepwise mechanism whereby 6 acts as an amido base, liberating HTMP during the first DoM event. Re-coordination of the amine at lithium then incurs the elimination of EtH. Reaction of the resulting alkyl(amido)(arylamido)zincate with a second equivalent of N,N-diisopropylnaphthamide eliminates HTMP and affords 7. Both DoM steps involve the exhibition of amido basicity and each reveals a low kinetic barrier to reaction. Understanding of this reaction sequence is tested by treating 6 with N,N-diisopropylbenzamide in THF. On the basis of theory and experiment, the presence of THF solvent (in place of stronger Lewis bases) combined with the use of a sterically less congested aromatic amide is expected to encourage threefold, stepwise reaction. Isolation and characterization of the resulting tripodal zincate Zn(micro-C6H4C(O)NiPr2-2)3Li.THF 8 bears this out and suggests a significant new level of control in zincate-induced DoM chemistry through the combination of experiment and DFT studies.

The instrumentation and methodology associated with chemical crystallography has developed extensively over the last 25 years. Data collection times have been reduced from days to hours and even minutes as serial diffractometers have been replaced by area detector systems. The increase in reliability of rotating anode generators and the advent of synchrotron radiation has meant that the available X-ray flux has increased by factors of between 100 to 10,000. These advances coupled with the development of new cryogenic systems and high pressure cells has allowed a range of new types of crystallographic experiment to be undertaken that had not been possible previously. One area that has benefited from these advances is stroboscopic photocrystallography, where it is possible to determine the structure of molecules in a crystalline environment that have lifetimes of only a few microseconds or to monitor reactions as they occur in real time. These experiments originate from technical easier experiments, which i...

The importance of C–H bond activation in a simple molecule to form a molecule with enhanced functionality can be easily understood from a study of biological processes at a molecular level where, for example, a specific enzyme selectively activates a chemically inert C–H bond and functionalizes it to a useful product. This strategy is now being used for large scale industrial processes and has both social and environmental benefits. C–H bond functionalization is also of major importance in catalysis because of the possibility of constructing complex structural motifs from relatively simple precursors. However, functionalization of a chemically inert C–H bond needs specific catalysts or reaction conditions that can selectively activate a particular C–H bond, leaving others intact. To achieve this target, various metal catalyzed or mediated reactions have been employed. Keeping the growing importance of this emerging field in mind, we now present recent advances in the field of C–H activation and functionalization using group 10 transition metal catalysts. Attempts have also been made to discuss the future of group 10 transition metals in catalysis.

The importance of C–H bond activation in a simple molecule to form a molecule with enhanced functionality can be easily understood from a study of biological processes at a molecular level where, for example, a specific enzyme selectively activates a chemically inert C–H bond and functionalizes it to a useful product. This strategy is now being used for large scale industrial processes and has both social and environmental benefits. C–H bond functionalization is also of major importance in catalysis because of the possibility of constructing complex structural motifs from relatively simple precursors. However, functionalization of a chemically inert C–H bond needs specific catalysts or reaction conditions that can selectively activate a particular C–H bond, leaving others intact. To achieve this target, various metal catalyzed or mediated reactions have been employed. Keeping the growing importance of this emerging field in mind, we now present recent advances in the field of C–H activation and functionalization using group 10 transition metal catalysts. Attempts have also been made to discuss the future of group 10 transition metals in catalysis.

A new family of luminescent platinum(II) acetylide complexes and polymers were formed by the copper(I) catalyzed reaction of cis-[PtCl2(PR3)2] (R=C6H5–p-CH3) with appropriate acetylide ligands. The reaction of metal precursors with 2.5 equivalents of monoterminal acetylide ligands provided metal complexes trans-[Pt(p-tolyl3P)2(C≡C-R)2] (R=C6H4-p-NO2 (1) C6H4 -p-CH3 (2)), and equimolar amounts of diterminal ligand and metal chloride precursor, under reflux, afforded the metal poly-yne polymers [-Pt(p-tolyl3P)2C≡C–R–C≡C–]n, (R=biphenyl and 2,5-dioctyloxybenzene). Characterization of the newly developed polymer and metal complexes was accomplished by FT-IR, multinuclear NMR (1H, 31P, 13C) and mass spectrometry, as well as elemental analysis. The molecular structure of the metal complex trans-[Pt(p-tolyl3P)2(C≡CC6H4–p-NO2)2] (1) was confirmed by single crystal X-ray crystallography. The electronic absorption and photoluminescence spectra of the metal complexes and polymers have been used to probe their photophysical properties. The studies reveal that the presence of heavy metal atom and substituent groups on the phenyl ring of the ligands can enhance the efficiency of intersystem crossing from the S1 singlet excited state to the T1 triplet excited state and thus give intense phosphorescence.

A new series of biphenylene ethynylene co-polymers, poly(2,5-dialkoxy-4-phenyleneethynylene-4,4-biphenyleneethynylene)s of the general formula [-C ≡C-4-C6H4-C6H4-4-C ≡C-C6H2(2,5-OR)2-]n (R = C4H9 P1, C8H17 P2) has been synthesized using a palladium/copper catalyzed coupling reaction between HC ≡C-4-C6H4-C6H4-4-C ≡C-H and IC6H2(2,5-OR)2I. The new co-polymer [-C ≡C-C6H2(2,5-OC8H17)2-C ≡C-C6H2(2,5-OC4H9)2-]n P5 has also been formed where different alkoxy substituents are present on alternate arene rings in the same polymer backbone. All the polymers were characterized by IR, 1H and 13C NMR spectroscopy and by GPC. The model compounds C6H5-4-C6H4-C≡C-C6H2(2,5-OR)2-4-C6H4-C6H5 (R = C4H9 M1, C8H17 M2) have also been prepared by the reaction between C6H5-4-C6H4-C≡CH and IC6H2(2,5-OR)2I. Single crystal X-ray structures of M1, M2 and Me3Si-C≡C-4-C6H4-C6H4-4-C≡C-SiMe3 were determined with a view to obtain a better understanding of the molecular and intermolecular interactions in the solid state which has been used to explain the optical properties of the polymers derived from them. The absorption and photoluminescence spectra of the polymers, P1, P2 and P5 showed that the lowest energy band is blue shifted due to the introduction of biphenylene fragments into the alkoxy substituted poly(ethynylenephenylene)s.

We present the results of a detailed theoretical study of the linkage isomerisation in [Ni(Et4dien)(η2-O,ON)(η1-NO2)] (Et4dien = N,N,N′,N′-tetraethyldiethylenetriamine). We probe the structure and bonding of the three experimentally-identified isomers in this system through electronic-structure calculations, and we establish possible transition pathways between them using transition-state modelling and periodic solid-state molecular-dynamics simulations. We also explore the photochemical isomerisation reaction using time-dependent density-functional theory. These results provide a thorough account of the linkage isomerisation in this compound, and add insight to ongoing experimental work on this and related systems.

As the spatial and temporal resolution accessible to experiment and theory converge, computational chemistry is an increasingly powerful tool for modelling and interpreting spectroscopic data. However, the study of molecular processes, in particular those related to electronic excitations (e.g. photochemistry), frequently pushes quantum-chemical techniques to their limit. The disparity in the level of theory accessible to periodic and molecular calculations presents a significant challenge when modelling molecular crystals, since accurate calculations require a high level of theory to describe the molecular species, but must also take into account the influence of the crystalline environment on their properties. In this article, we briefly review the different classes of quantum-chemical techniques, and present an overview of methods that account for environmental influences with varying levels of approximation. Using a combination of solid-state and molecular calculations, we quantitatively evaluate the performance of implicit-solvent models for the [Ni(Et4dien)(η2-O,ON)(η1-NO2)] linkage-isomer system as a test case. We focus particularly on the accurate reproduction of the energetics of the isomerisation, and on predicting spectroscopic properties to compare with experimental results. This work illustrates how the synergy between periodic and molecular calculations can be exploited for the study of molecular crystals, and forms a basis for the investigation of more challenging phenomena, such as excited-state dynamics, and for further methodological developments.

(Figure Presented) Give and take: A molecular cluster that readily takes up and stores two molecules of H2 also rapidly releases (milliseconds) the stored H2 by a simple redox process. This process represents a new method of hydrogen storage and release from a well-defined molecular material. © 2006 Wiley-VCH Verlag GmbH and Co. KGaA.

Reactions between the activated cluster [Os 3 (CO) 10 (NCMe) 2 ] and malonic acid, succinic acid and dicarboxylic acetylene, respectively, lead to the formation of the linked cluster complexes [{Os 3 H(CO) 10 } 2 (CO 2 CH 2 CO 2 )] ( 1 ), [{Os 3 H(CO) 10 } 2 (CO 2 C 2 H 4 CO 2 )] ( 2 ), and [{Os 3 H(CO) 10 } 2 (C 4 O 4 )] ( 3 ) in good yield. Cluster 3 was subsequently treated with [Co 2 (CO) 8 ] and this results in the addition of a “Co 2 (CO) 6 ” group giving [{Os 3 H(CO) 10 } 2 (C 2 O 4 ){Co 2 (CO) 6 }] ( 4 ). The X-ray crystal structures are reported for 2 – 4 . In each structure the two triangular triosmium units are linked by the carboxylate groups and within each complex the carboxylate groups are chelating and bridge two osmium atoms.

A new class of transition metal cluster is described, [Rh(6)(PR(3))(6)H(12)][BAr(F)(4)](2) (R = (i)Pr (1a), Cy (2a); BAr(F)(4) = [B{C(6)H(3)(CF(3))(2)}(4)](-)). These clusters are unique in that they have structures exactly like those of early transition metal clusters with edge-bridging pi-donor ligands rather than the structures expected for late transition metal clusters with pi-acceptor ligands. The solid-state structures of 1a and 2a have been determined, and the 12 hydride ligands bridge each Rh-Rh edge of a regular octahedron. Pulsed gradient spin-echo NMR experiments show that the clusters remain intact in solution, having calculated hydrodynamic radii of 9.5(3) A for 1a and 10.7(2) A for 2a, and the formulation of 1a and 2a was unambiguously confirmed by ESI mass spectrometry. Both 1a and 2a take up two molecules of H(2) to afford the cluster species [Rh(6)(P(i)Pr(3))(6)H(16)][BAr(F)(4)](2) (1b) and [Rh(6)(PCy(3))(6)H(16)][BAr(F)(4)](2) (2b), respectively, as characterized by NMR spectroscopy, ESI-MS, and, for 2b, X-ray crystallography using the [1-H-CB(11)Me(11)](-) salt. The hydride ligands were not located by X-ray crystallography, but (1)H NMR spectroscopy showed a 15:1 ratio of hydride ligands, suggesting an interstitial hydride ligand. Addition of H(2) is reversible: placing 1b and 2b under vacuum regenerates 1a and 2a. DFT calculations on [Rh(6)(PH(3))(6)H(x)()](2+) (x = 12, 16) support the structural assignments and also show a molecular orbital structure that has 20 orbitals involved with cluster bonding. Cluster formation has been monitored by (31)P{(1)H} and (1)H NMR spectroscopy, and mechanisms involving heterolytic H(2) cleavage and elimination of [HP(i)Pr(3)](+) or the formation of trimetallic intermediates are discussed.

The structures are reported of 20 1:1 complexes formed between 2,4,6-tri-cz-pyridyl-1,3,5-triazine (tptz) and the nitrates of yttrium and the lanthanoids (La-Lu except Pm). The complexes can be divided up into a series of structural types. The majority of the characterised complexes belong to the isostructural family [Ln(tptz)(NO3)(3)(H2O)]center dot 2C(2)H(5)OH (Ln = Y (3), La-Yb (4-16)), which have three bidentate nitrate groups as well as a co-ordinated water molecule, and the metal ion is 10 co-ordinate, whilst a similar lanthanum complex [La(tptz)(NO3)(3)(H2O)]center dot Me2CO (2) has been prepared. Eleven co-ordinate [La(tptz)(NO3)(3)(CH3OH)(2)] (1), which has three bidentate nitrate groups as well as two co-ordinated methanol molecules, is also reported. By varying the solvent used, three different lutetium complexes can be obtained; [Lu(tptz)(NO3)(3)(C2H5OH)]center dot C2H5OH (18) and [Lu(tptz)(NO3)(3)(H2O)]center dot MeCN (19), both featuring two bidentate nitrate groups, a monodentate nitrate group and a co-ordinated solvent molecule, and [Lu(tptz)(NO3)(2)(H2O)(2)]NO3 center dot 3MeOH (20), whose cation contains two bidentate nitrate groups as well as two co-ordinated water molecules. The ytterbium complex [Yb(tptz)(NO3)(3)(C2H5OH)]-C2H5OH (17) is also described. (c) 2005 Elsevier Ltd. All rights reserved.

Carbonyl⋯carbonyl interactions involving Tr–CO moieties (Tr = first-row transition element) have been studied using crystal structure data retrieved from the Cambridge Structural Database and by use of DFT calculations. By comparison with organic ketones, Tr–CO systems show an increased tendency to form close CO⋯CO interactions, with 45% of these forming pairwise interactions in a sheared antiparallel dimer motif and 55% having a perpendicular (single interaction) geometry. The bulky Tr and steric hindrance arising from other ligands at Tr play a significant role in the formation and geometry of the interactions. DFT calculations for the antiparallel dimer indicate that interaction energies for Tr–CO systems are slightly stronger than for organic ketones, and there is evidence of a stronger CO bond dipole in Tr–CO systems. With interaction energies comparable to those for medium strength hydrogen bonds, we conclude that CO⋯CO interactions in Tr–CO species may have a role to play in the design of novel carbonyl-containing inorganic and metal–organic structures.