Showing papers by "Alexander J. Blake published in 2014"

Studies on metal-organic frameworks of Cu(II) with isophthalate linkers for hydrogen storage.

Abstract: Hydrogen (H2) is a promising alternative energy carrier because of its environmental benefits, high energy density, and abundance. However, development of a practical storage system to enable the “Hydrogen Economy” remains a huge challenge. Metal–organic frameworks (MOFs) are an important class of crystalline coordination polymers constructed by bridging metal centers with organic linkers. MOFs show promise for H2 storage owing to their high surface area and tuneable properties.In this Account, we summarize our research on novel porous materials with enhanced H2 storage properties and describe frameworks derived from 3,5-substituted dicarboxylates (isophthalates) that serve as versatile molecular building blocks for the construction of a range of interesting coordination polymers with Cu(II) ions.We synthesized a series of materials by connecting linear tetracarboxylate linkers to {Cu(II)2} paddlewheel moieties. These materials exhibit high structural stability and permanent porosity. Varying the organic ...

A Robust Binary Supramolecular Organic Framework (SOF) with High CO2 Adsorption and Selectivity

Abstract: A robust binary hydrogen-bonded supramolecular organic framework (SOF-7) has been synthesized by solvothermal reaction of 1,4-bis-(4-(3,5-dicyano-2,6-dipyridyl)dihydropyridyl)benzene (1) and 5,5′-bis-(azanediyl)-oxalyl-diisophthalic acid (2). Single crystal X-ray diffraction analysis shows that SOF-7 comprises 2 and 1,4-bis-(4-(3,5-dicyano-2,6-dipyridyl)pyridyl)benzene (3); the latter formed in situ from the oxidative dehydrogenation of 1. SOF-7 shows a three-dimensional four-fold interpenetrated structure with complementary O–H···N hydrogen bonds to form channels that are decorated with cyano and amide groups. SOF-7 exhibits excellent thermal stability and solvent and moisture durability as well as permanent porosity. The activated desolvated material SOF-7a shows high CO2 adsorption capacity and selectivity compared with other porous organic materials assembled solely through hydrogen bonding.

Analysis of high and selective uptake of CO2 in an oxamide-containing {Cu2(OOCR)4}-based metal-organic framework.

Abstract: The porous framework [Cu2(H2O)2L]⋅4 H2O⋅2 DMA (H4L=oxalylbis(azanediyl)diisophthalic acid; DMA=N,N-dimethylacetamide), denoted NOTT-125, is formed by connection of {Cu2(RCOO)4} paddlewheels with the isophthalate linkers in L4−. A single crystal structure determination reveals that NOTT-125 crystallises in monoclinic unit cell with a=27.9161(6), b=18.6627(4) and c=32.3643(8) A, β=112.655(3)°, space group P21/c. The structure of this material shows fof topology, which can be viewed as the packing of two types of cages (cage A and cage B) in three-dimensional space. Cage A is constructed from twelve {Cu2(OOCR)4} paddlewheels and six linkers to form an ellipsoid-shaped cavity approximately 24.0 A along its long axis and 9.6 A across its central diameter. Cage B consists of six {Cu2(OOCR)4} units and twelve linkers and has a spherical diameter of 12.7 A taking into account the van der Waals radii of the atoms. NOTT-125 incorporates oxamide functionality within the pore walls, and this, combined with high porosity in desolvated NOTT-125a, is responsible for excellent CO2 uptake (40.1 wt % at 273 K and 1 bar) and selectivity for CO2 over CH4 or N2. Grand canonical Monte Carlo (GCMC) simulations show excellent agreement with the experimental gas isotherm data, and a computational study of the specific interactions and binding energies of both CO2 and CH4 with the linkers in NOTT-125 reveals a set of strong interactions between CO2 and the oxamide motif that are not possible with a single amide.

Triamidoamine-uranium(IV)-stabilized terminal parent phosphide and phosphinidene complexes

Abstract: Reaction of [U(TrenTIPS)(THF)][BPh4] (1; TrenTIPS=N{CH2CH2NSi(iPr)3}3) with NaPH2 afforded the novel f-block terminal parent phosphide complex [U(TrenTIPS)(PH2)] (2; U–P=2.883(2) A). Treatment of 2 with one equivalent of KCH2C6H5 and two equivalents of benzo-15-crown-5 ether (B15C5) afforded the unprecedented metal-stabilized terminal parent phosphinidene complex [U(TrenTIPS)(PH)][K(B15C5)2] (4; U[DOUBLE BOND]P=2.613(2) A). DFT calculations reveal a polarized-covalent U[DOUBLE BOND]P bond with a Mayer bond order of 1.92.

Synthesis and characterization of an f-block terminal parent imido [U═NH] complex: a masked uranium(IV) nitride.

Abstract: Deprotonation of [U(TrenTIPS)(NH2)] (1) [TrenTIPS = N(CH2CH2NSiPri3)3] with organoalkali metal reagents MR (M = Li, R = But; M = Na–Cs, R = CH2C6H5) afforded the imido-bridged dimers [{U(TrenTIPS)(μ-N[H]M)}2] [M = Li–Cs (2a–e)]. Treatment of 2c (M = K) with 2 equiv of 15-crown-5 ether (15C5) afforded the uranium terminal parent imido complex [U(TrenTIPS)(NH)][K(15C5)2] (3c), which can also be viewed as a masked uranium(IV) nitride. The uranium–imido linkage was found to be essentially linear, and theoretical calculations suggested σ2π4 polarized U–N multiple bonding. Attempts to oxidize 3c to afford the neutral uranium terminal parent imido complex [U(TrenTIPS)(NH)] (4) resulted in spontaneous disproportionation to give 1 and the uranium–nitride complex [U(TrenTIPS)(N)] (5); this reaction is a new way to prepare the terminal uranium–nitride linkage and was calculated to be exothermic by −3.25 kcal mol–1.

Synthesis, Characterization, and Reactivity of a Uranium(VI) Carbene Imido Oxo Complex

Abstract: We report the uranium(VI) carbene imido oxo complex [U(BIPMTMS)(NMes)(O)(DMAP)2] (5, BIPMTMS=C(PPh2NSiMe3)2; Mes=2,4,6-Me3C6H2; DMAP=4-(dimethylamino)pyridine) which exhibits the unprecedented arrangement of three formal multiply bonded ligands to one metal center where the coordinated heteroatoms derive from different element groups. This complex was prepared by incorporation of carbene, imido, and then oxo groups at the uranium center by salt elimination, protonolysis, and two-electron oxidation, respectively. The oxo and imido groups adopt axial positions in a T-shaped motif with respect to the carbene, which is consistent with an inverse trans-influence. Complex 5 reacts with tert-butylisocyanate at the imido rather than carbene group to afford the uranyl(VI) carbene complex [U(BIPMTMS)(O)2(DMAP)2] (6).

The role of 5f-orbital participation in unexpected inversion of the σ-bond metathesis reactivity trend of triamidoamine thorium(IV) and uranium(IV) alkyls

Abstract: We report on the role of 5f-orbital participation in the unexpected inversion of the σ-bond metathesis reactivity trend of triamidoamine thorium(IV) and uranium(IV) alkyls Reaction of KCH2Ph with [U(TrenTIPS)(I)] [2a, TrenTIPS = N(CH2CH2NSiPri3)33−] gave the cyclometallate [U{N(CH2CH2NSiPri3)2(CH2CH2NSiPri2C[H]MeCH2)}] (3a) with the intermediate benzyl complex not observable In contrast, when [Th(TrenTIPS)(I)] (2b) was treated with KCH2Ph, [Th(TrenTIPS)(CH2Ph)] (4) was isolated; which is notable as Tren N-silylalkyl metal alkyls tend to spontaneously cyclometallate Thermolysis of 4 results in the extrusion of toluene and formation of the cyclometallate [Th{N(CH2CH2NSiPri3)2(CH2CH2NSiPri2C[H]MeCH2)}] (3b) This reactivity is the reverse of what would be predicted Since the bonding of thorium is mainly electrostatic it would be predicted to undergo facile cyclometallation, whereas the more covalent uranium system might be expected to form an isolable benzyl intermediate The thermolysis of 4 follows well-defined first order kinetics with an activation energy of 223 ± 01 kcal mol−1, and Eyring analyses yields ΔH‡ = 217 ± 36 kcal mol−1 and ΔS‡ = −105 ± 31 cal K−1 mol−1, which is consistent with a σ-bond metathesis reaction Computational examination of the reaction profile shows that the inversion of the reactivity trend can be attributed to the greater f-orbital participation of the bonding for uranium facilitating the σ-bond metathesis transition state whereas for thorium the transition state is more ionic resulting in an isolable benzyl complex The activation barriers are computed to be 190 and 222 kcal mol−1 for the uranium and thorium cases, respectively, and the latter agrees excellently with the experimental value Reductive decomposition of “[U(TrenTIPS)(CH2Ph)]” to [U(TrenTIPS)] and bibenzyl followed by cyclometallation to give 3a with elimination of dihydrogen was found to be endergonic by 4 kcal mol−1 which rules out a redox-based cyclometallation route for uranium

Two-Electron Reductive Carbonylation of Terminal Uranium(V) and Uranium(VI) Nitrides to Cyanate by Carbon Monoxide

Abstract: Two-electron reductive carbonylation of the uranium(VI) nitride [U(TrenTIPS)(N)] (2, TrenTIPS=N(CH2CH2NSiiPr3)3) with CO gave the uranium(IV) cyanate [U(TrenTIPS)(NCO)] (3). KC8 reduction of 3 resulted in cyanate dissociation to give [U(TrenTIPS)] (4) and KNCO, or cyanate retention in [U(TrenTIPS)(NCO)][K(B15C5)2] (5, B15C5=benzo-15-crown-5 ether) with B15C5. Complexes 5 and 4 and KNCO were also prepared from CO and the uranium(V) nitride [{U(TrenTIPS)(N)K}2] (6), with or without B15C5, respectively. Complex 5 can be prepared directly from CO and [U(TrenTIPS)(N)][K(B15C5)2] (7). Notably, 7 reacts with CO much faster than 2. This unprecedented f-block reactivity was modeled theoretically, revealing nucleophilic attack of the π* orbital of CO by the nitride with activation energy barriers of 24.7 and 11.3 kcal mol−1 for uranium(VI) and uranium(V), respectively. A remarkably simple two-step, two-electron cycle for the conversion of azide to nitride to cyanate using 4, NaN3 and CO is presented.

A novel bismuth-based metal-organic framework for high volumetric methane and carbon dioxide adsorption.

Abstract: Solvothermal reaction of H4L (L = biphenyl-3,3’,5,5’-tetracarboxylate) and Bi(NO3)3·(H2O)5 in a mixture of DMF/MeCN/H2O in the presence of piperazine and nitric acid at 100 oC for 10 h affords the solvated metal-organic polymer [Bi2(L)1.5(H2O)2]·(DMF)3.5·(H2O)3 (NOTT-220-solv). A single crystal X-ray structure determination confirms that it crystallises in space group P2/c and has a neutral and non-interpenetrated structure comprising binuclear {Bi2} centres bridged by tetracarboxylate ligands. NOTT-220-solv shows a 3,6-connected network having a new framework topology with a {4·62}2{42·65·88}{62·8} point symbol. The desolvated material NOTT-220a shows exceptionally high adsorption uptakes for CH4 and CO2 on a volumetric basis at moderate pressures and temperatures with a CO2 uptake of 553 gL-1 (20 bar, 293 K) with a saturation uptake of 688 gL-1 (1 bar, 195 K). The corresponding CH4 uptake of 165 V(STP)/V (20 bar, 293 K) and 189 V(STP/V) (35 bar, 293 K) is within the top three MOF materials under the same conditions, surpassed only by PCN-14 and Ni-MOF-74 (230 and 190 V(STP)/V 35 Bar, 298 K). The maximum CH4 uptake for NOTT-220a was recorded at 20 bar and 195 K to be 287 V(STP)/V, while H2 uptake of NOTT-220a at 20 bar, 77 K is 42 gL-1. These gas uptakes have been modelled by Grand Canonical Monte Carlo (GCMC) and Density Functional Theory (DFT) calculations, which confirm the experimental data and give insights into the nature of the binding sites of CH4 and CO2 in this porous hybrid material.

Dynamics of ground and excited state vibrational relaxation and energy transfer in transition metal carbonyls.

Abstract: Nonlinear vibrational spectroscopy provides insights into the dynamics of vibrational energy transfer in and between molecules, a crucial phenomenon in condensed phase physics, chemistry, and biology. Here we use frequency-domain 2-dimensional infrared (2DIR) spectroscopy to investigate the vibrational relaxation (VR) and vibrational energy transfer (VET) rates in different solvents in both the electronic ground and excited states of Re(Cl)(CO)3(4,4′-diethylester-2,2′-bipyridine), a prototypical transition metal carbonyl complex. The strong C≡O and ester C═O stretch infrared reporters, located on opposite sides of the molecule, were monitored in the 1600–2100 cm–1 spectral region. VR in the lowest charge transfer triplet excited state (3CT) is found to be up to eight times faster than in the ground state. In the ground state, intramolecular anharmonic coupling may be solvent-assisted through solvent-induced frequency and charge fluctuations, and as such VR rates are solvent-dependent. In contrast, VR rate...

Reactivity of the uranium(IV) carbene complex [U(BIPMTMS)(Cl)(μ-Cl)2Li(THF)2] (BIPMTMS = {C(PPh2NSiMe3)2}) towards carbonyl and heteroallene substrates: metallo-Wittig, adduct formation, C–F bond activation, and [2 + 2]-cycloaddition reactions

Abstract: The reactivity of the uranium(IV) carbene complex [U(BIPMTMS)(Cl)(μ-Cl)2Li(THF)2] (1, BIPMTMS = {C(PPh2NSiMe3)2}) towards carbonyl and heteroallene substrates is reported. Reaction of 1 with benzophenone proceeds to give the metallo-Wittig terminal alkene product Ph2CC(PPh2NSiMe3)2 (2); the likely “UOCl2” byproduct could not be isolated. Addition of the bulky ketone PhCOBut to 1 resulted in loss of LiCl, coordination of the ketone, and dimerisation to give [U(BIPMTMS)(Cl)(μ-Cl){OC(Ph)(But)}]2 (3). The reaction of 1 with coumarin resulted in ring opening of the cyclic ester and a metallo-Wittig-type reaction to afford [U{BIPMTMS[C(O)(CHCHC6H4O-2)]-κ3-N,O,O′}(Cl)2(THF)] (4) where the enolate product remains coordinated to uranium. The reaction of PhCOF with 1 resulted in C–F bond activation and oxidation resulting in isolation of [U(O)2(Cl)2(μ-Cl)2{(μ-LiDME)OC(Ph)C(PPh2NSiMe3)(PPh2NHSiMe3)}2] (5) along with [U(Cl)2(F)2(py)4] (6). The reactions of 1 with tert-butylisocyanate or dicyclohexylcarbodiimide resulted in the isolation of the [2 + 2]-cycloaddition products [U{BIPMTMS[C(NBut){OLi(THF)2(μ-Cl)Li(THF)3}]-κ4-C,N,N′,N′′}(Cl)3] (7) and [U{BIPMTMS[C(NCy)2]-κ4-C,N,N′,N′′}(Cl)(μ-Cl)2Li(THF)2] (8). Complexes 2–8 have been variously characterised by single crystal X-ray diffraction, multi-nuclear NMR and FTIR spectroscopies, Evans method solution magnetic moments, variable temperature SQUID magnetometry, and elemental analyses.

Synthesis and characterisation of magnesium complexes containing sterically demanding N,N'-bis(aryl)amidinate ligands.

Abstract: Condensation reactions of carboxylic acids and anilines in the presence of polyphosphoric acid trimethylsilyl ester (PPSE) afforded a range of sterically demanding N,N'-bis(aryl)amidines, RN{C(R')}N(H)R [R = Mes (Mes = 2,4,6-trimethylphenyl), R' = Cy (Cy = cyclohexyl) L¹H; R = Dipp (Dipp = 2,6-diisopropylphenyl), R' = Cy L²H; R = Mes, R' = Ph L³H; R = Dipp, R' = Ph L⁴H; R = Mes, R' = Dmp (Dmp = 3,5-dimethylphenyl) L⁵H; R = Dipp, R' = Dmp L⁶H; R = Dmp, R' = Cy L⁷H]. Amidines L¹H-L⁷H have been characterised spectroscopically, and for L⁵H and L⁶H, by X-ray crystallography. Treatment of the amidines with di-n-butylmagnesium in THF solution afforded the monomeric magnesium bis(amidinates) [Mg(L¹)2(THF)] 1, [Mg(L²)2] 2, [Mg(L³)2(THF)] 3, [Mg(L⁵)2(THF)] 5, [Mg(L⁶)2] 6, [Mg(L⁷)2] 7, and the magnesium mono(amidinate) complex [Mg(L⁴)((n)Bu)] 4. These complexes have been characterised spectroscopically, with 1-3, 5 and 6 also being structurally authenticated. Comparison of the magnesium bis(amidinate) complexes reveals that the steric bulk of the amidinate ligand influences both the solid state structure and solution behaviour of these complexes.

The Ketimide Ligand is Not Just an Inert Spectator: Heteroallene Insertion Reactivity of an Actinide–Ketimide Linkage in a Thorium Carbene Amide Ketimide Complex

Abstract: The ketimide anion R2C[DOUBLE BOND]N− is an important class of chemically robust ligand that binds strongly to metal ions and is considered ideal for supporting reactive metal fragments due to its inert spectator nature; this contrasts with R2N− amides that exhibit a wide range of reactivities. Here, we report the synthesis and characterization of a rare example of an actinide ketimide complex [Th(BIPMTMS){N(SiMe3)2}(N[DOUBLE BOND]CPh2)] [2, BIPMTMS=C(PPh2NSiMe3)2]. Complex 2 contains Th[DOUBLE BOND]Ccarbene, Th[BOND]Namide and Th[BOND]Nketimide linkages, thereby presenting the opportunity to probe the preferential reactivity of these linkages. Importantly, reactivity studies of 2 with unsaturated substrates shows that insertion reactions occur preferentially at the Th[BOND]Nketimide bond rather than at the Th[DOUBLE BOND]Ccarbene or Th[BOND]Namide bonds. This overturns the established view that metal-ketimide linkages are purely inert spectators.

Modification of coordination networks through a photoinduced charge transfer process

Abstract: A metal-bearing coordination network synthesised from Re(2,2′-bipyridine-5,5′-dicarboxylate)(CO)3Cl bridging ligands and Cu(II) nodes, [{Cu(DMF)(H2O)[LRe(CO)3Cl]}·DMF]∞ReCu, undergoes an irreversible photoinduced charge transfer process. We demonstrate using time-resolved IR spectroscopy the nature of this photoinduced process and how, under suitable conditions, it is possible to initiate irreversible modification of the crystal through induction of the charge transfer process. As a result we are able to use the photoinduced process, which arises purely as a result of the structure of the coordination network, to write on crystals.

Influence of crown thioether ligands in the structures and of perhalophenyl groups in the optical properties of complexes with argentoaurophilic interactions

Abstract: Reaction of [{Au(C6X5)2}Ag]n (X = Cl, F) with the crown thioethers 1,4,7-trithiacyclononane ([9]aneS3), 1,4,8,11-tetrathiacyclotetradecane ([14]aneS4), or 1,4,7,10,13,16,19,22-octathiacyclotetracosane ([24]aneS8) affords a series of heteronuclear Au(I)/Ag(I) compounds of stoichiometry [{Au(C6X5)2}Ag(L)x] (L = [9]aneS3, x = 2 (1, 4); L = [14]aneS4, x = 1 (2, 5); L = [24]aneS8, x = 0.5 (3, 6)) formed via Ag-S bonds and Au···Ag contacts. X-ray diffraction studies of some of these complexes reveal different structural arrangements and nuclearity depending on the nature of the crown thioether ligand and on the presence or absence of aurophilic interactions. All the complexes are luminescent in the solid state but not in solution. Density functional theory calculations on representative model systems of complexes 2-4 and 6 were carried out to determine the origin of the electronic transitions responsible for their optical properties, which strongly depend on the nature of the perhalophenyl groups bonded to gold.

Alkali metal derivatives of an ortho-phenylene diamine

Abstract: Treatment of the ortho-phenylene diamine C6H4-1,2-{N(H)Tripp}2 (1, PDAH2, Tripp = 2,4,6-triisopropylphenyl) with two equivalents of MR (M = Li, R = Bun; M = Na or K, R = CH2C6H5) afforded the dimetallated alkali metal ortho-phenylene diamide dianion complexes [(PDALi2)(THF)3] (2), [{(PDANa2)(THF)2}2] (3), and [{(PDAK2)(THF)3}2] (4). In contrast, treatment of 2 with two equivalents of rubidium or cesium 2-ethylhexoxide, or treatment of 1 with two equivalents of MR (M = Rb or Cs, R = CH2C6H5) did not afford the anticipated dialkali metal ortho-phenylene diamide dianion derivatives and instead formally afforded the monometallic ortho-diiminosemiquinonate radical anion species [PDAM] (M = Rb, 5; M = Cs, 6). The structure of 2 is monomeric with one lithium coordinated to the two nitrogen centres and the other lithium η4-coordinated to the diazabutadiene portion of the PDA scaffold. Similar structural cores are observed for 3 and 4, except that the larger sodium and potassium ions give dimeric structures linked by multi-hapto interactions from the PDA backbone phenyl ring to an alkali metal centre. Complex 5 was not characterised in the solid state, but the structure of 6 reveals coordination of cesium ions to both PDA amide centres and multi-hapto interactions to a PDA backbone phenyl ring in the next unit to generate a one-dimensional polymer. Complexes 2–6 have been variously characterised by X-ray crystallography, multi-nuclear NMR, FTIR, and EPR spectroscopies, and CHN microanalyses.

Ligand influences on homoleptic Group 12 m-terphenyl complexes

Abstract: Three m-terphenyl ligands 2,6-Ar2C6H3− [Ar = 2,6-Me2C6H3 (2,6-Xyl); 3,5-Me2C6H3 (3,5-Xyl); 2,3,4,5,6-Me5C6 (Pmp)] have been used to stabilise three series of two-coordinate Group 12 diaryl complexes; (2,6-Ar2C6H3)2M [M = Zn, Cd, Hg, Ar = 2,6-Xyl 1–3, 3,5-Xyl 4–6, Pmp 7–9], where differing steric demands on the metal centres are imparted. These are the first homoleptic d-block complexes featuring any of these ligands. Complexes 1–9 have been characterised in solution and the solid state; the analysis of structural changes produced by differences in ligand properties is reported. In particular, complexes 4–6 show smaller C–M–C bond angles and contain secondary ligand interactions that are not seen in the analogous complexes 1–3 and 7–9.

High-pressure studies of palladium and platinum thioether macrocyclic dihalide complexes

Abstract: The mononuclear macrocyclic Pd(II) complex cis-[PdCl2([9 aneS3)] ([9]aneS3 = 1,4,7-trithiacyclononane) converts at 44 kbar into an intensely coloured chain polymer exhibiting distorted octahedral co-ordination at the metal centre and an unprecedented [1233] conformation for the thioether ligand. The evolution of an intramolecular axial sulphur metal interaction and an intermolecular equatorial sulfur-metal interaction is central to these changes. High pressure crystallographic experiments have also been undertaken on the related complexes [PtCl2([9]aneS3)], [PdBr2([9]aneS3)],[PtBr2([9]aneS3)], [PdI2([9]aneS3)] and [PtI2([9]aneS3)] in order to establish the effects of changing the halide ligands and the metal centre on the behaviour of these complexes under pressure. While all complexes undergo contraction of the various interaction distances with increasing pressure, only[PdCl2([9]aneS3)] undergoes a phase change. Pressure-induced I…I interactions were observed for [PdI2([9]aneS3)] and [PtI2([9]aneS3)] at 19 kbar but the corresponding Br…Br interactions in [PdBr2([9]aneS3)] and [PtBr2([9]aneS3)] only become significant at much higher pressure (58 kbar. Accompanying DFT calculations have yielded interaction energies and bond orders for the sulphur metal interactions.

Preparation and structural analysis of (±)-cis-ethyl 2-sulfanylidenedecahydro-1,6-naphthyridine-6-carboxylate and (±)-trans-ethyl 2-oxooctahydro-1H-pyrrolo[3,2-c]pyridine-5-carboxylate.

Abstract: Bicycle ring closure on a mixture of (4aS,8aR)- and (4aR,8aS)-ethyl 2-oxodecahydro-1,6-naphthyridine-6-carboxylate, followed by conversion of the separated cis and trans isomers to the corresponding thioamide derivatives, gave (4aSR,8aRS)-ethyl 2-sulfanylidenedecahydro-1,6-naphthyridine-6-carboxylate, C11H18N2O2S. Structural analysis of this thioamide revealed a structure with two crystallographically independent conformers per asymmetric unit (Z′ = 2). The reciprocal bicycle ring closure on (3aRS,7aRS)-ethyl 2-oxooctahydro-1H-pyrrolo[3,2-c]pyridine-5-carboxyl-ate, C10H16N2O3, was also accomplished in good overall yield. Here the five-membered ring is disordered over two positions, so that both enantiomers are represented in the asymmetric unit. The compounds act as key intermediates towards the synthesis of potential new polycyclic medicinal chemical structures.

Isolation and Characterisation of 2-Tert-butyl-8-hydroxyquinoline as a Crystalline Solid and Its Blue Fluorescent Li Complex

Abstract: 2-Tert-butyl-8-hydroxyquinoline (2-TB-8-hq) has been isolated as a crystalline solid and its X-ray structure elucidated, resolving three decades of controversy, since it was previously wrongly reported as yellow oil by some other workers. An improved synthetic method has been developed which increases the yield from 20% to 60%. The lithium complex of 2-TB-8-hq is blue emitting and the HOMO and LUMO levels are lowered by 0.86 eV and 0.74 eV, respectively, compared with the parent lithium 8-hydroxyquinolinolate (Li 8-hq).

Crystal structure of {2,2'-[ethyl-enebis(nitrilo-methanylyl-idene)]diphenolato-κ(4) O,N,N',O'}oxidovanadium(IV) methanol monosolvate.

Abstract: Two independent mol­ecules of the title solvated complex, [V(C16H14N2O2)O]·CH3OH, also known as [N,N′-bis­(salicyl­idene)ethyl­enedi­amine]­oxidovanadium(IV) or vanadyl salen, crystallize in the asymmetric unit. Each disordered methanol solvent mol­ecule [occupancy ratios 0.678 (4):0.322 (4) and 0.750 (5):0.250 (5)] is linked to a [N,N′-bis­(salicyl­idene)ethyl­enedi­amine]­oxidovanadium(IV) mol­ecule by an O—H⋯O hydrogen bond and to others by C—H⋯O hydrogen bonds. The resulting extended structure consists of a bilayer of mol­ecules parallel to the ab plane. Despite the fact that solvates are common in complexes derived from substituted analogues of the N,N′-bis­(salicyl­idene)ethyl­enedi­amine ligand, the title solvate is the first one of [N,N′-bis­(salicyl­idene)ethyl­enedi­amine]­oxidovanadium(IV) to be structurally characterized. The two vanadyl species have very similar inter­nal geometries, which are best characterized as distorted square-based pyramidal with the vanadium atom displaced from the N2O2 basal plane by 0.5966 (9) A in the direction of the doubly-bonded oxide ligand.

Dilithium cyclohexanediacetate: A layered coordination polymer with non-valent hydrophobic contacts

Abstract: By heating a solution of LiOH and 1,1′-cyclohexanediacetic acid (H2chda) coordination polymer [Li2(chda)] (1) having a layered nature is obtained and characterized.