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Five new imidazo[4,5-f]-1,10-phenanthroline based ligands (1–5) have been synthesised and characterised. The facile synthesis of 1–5 allows two regiochemical points of structural variety allowing highly conjugated and bulky aryl groups of varying functionalities, including azobenzene, trityl and terpyridine constituents, to be attached to the ligand core. 1–5 are fluorescent (λem = 410–415 nm), and react readily with [ReBr(CO)5] in toluene to give neutral coordination complexes of the form fac-[ReBr(CO)3(1–5)]. The series of complexes was characterised using a variety of spectroscopic and analytical techniques. Two examples of this series were characterised in the solid state using single crystal X-ray diffraction which confirmed the octahedral geometry and formulation. Photophysical studies showed that fac-[ReBr(CO)3(1–5)] are phosphorescent in solution under ambient conditions, revealing visible emission (558–585 nm) in aerated solution with corresponding lifetimes in the range 149–267 ns. These attributes are consistent with a triplet metal to ligand charge transfer (3MLCT) emitting state.

A combination of charge density studies and solid state nuclear magnetic resonance (NMR) 1 J NC coupling measurements supported by periodic density functional theory (DFT) calculations is used to characterise the transition from an n–π* interaction to bond formation between a nucleophilic nitrogen atom and an electrophilic sp 2 carbon atom in a series of crystalline peri‐substituted naphthalenes. As the N⋅⋅⋅C distance reduces there is a sharp decrease in the Laplacian derived from increasing charge density between the two groups at ca. N⋅⋅⋅C = 1.8 Å, with the periodic DFT calculations predicting, and heteronuclear spin‐echo NMR measurements confirming, the 1 J NC couplings of ≈3–6 Hz for long C−N bonds (1.60–1.65 Å), and 1 J NC couplings of 2.1 Å., A combination of charge density measurements, solid‐state NMR 1 J NC couplings, and DFT calculations is presented to characterise the transition from an n–π* interaction to bond formation for a series of model crystalline peri‐substituted naphthalenes.

The solid forms of acetaldehyde phenylhydrazone were investigated in detail over a century ago, with curious results: it was reported that a low melting form could be transformed into a high melting form by trace alkali, and the reverse process could be brought about with trace acid. Our reinvestigation of this puzzle with modern instrumentation has shown that all samples, although exhibiting sharp melting points varying from 56 to 101 °C, have identical IR and solid-state NMR spectra and identical crystal structures. NMR studies of the melts provided the key to the understanding of this strange behavior: differently melting samples did so because they initially melted to liquids with different proportions of the Z and E isomers, although given enough time they all tended to the same equilibrium proportion. The leading role of the isomerization rate in the melt was confirmed in cyclic differential scanning calorimetry experiments and accompanying simulations. In the case of polymorphism, different structures melt to the same liquid. In the present case, the same structure melts to different liquids.

The reaction of the simple metalloligand [FeIIIL3] [HL = 1-(4-pyridyl)butane-1,3-dione] with a variety of different MII salts results in the formation of a family of heterometallic cages of formulae [FeIII8PdII6L24]Cl12 (1), [FeIII8CuII6L24(H2O)4Br4]Br8 (2), [FeIII8CuII6L24(H2O)10](NO3)12 (3), [FeIII8NiII6L24(SCN)11Cl] (4), and [FeIII8CoII6L24(SCN)10(H2O)2]Cl2 (5). The metallic skeleton of each cage describes a cube in which the FeIII ions occupy the eight vertices and the MII ions lie at the center of the six faces. Direct-current magnetic susceptibility and magnetization measurements on 3–5 reveal the presence of weak antiferromagnetic exchange between the metal ions in all three cases. Computational techniques known in theoretical nuclear physics as statistical spectroscopy, which exploit the moments of the Hamiltonian to calculate relevant thermodynamic properties, determine JFe–Cu = 0.10 cm–1 for 3 and JFe–Ni = 0.025 cm–1 for 4. Q-band electron paramagnetic resonance spectra of 1 reveal a significant...

The synthesis and characterisation of complexes formed from lanthanide trifluoromethanesulfonates [Ln(OTf)3] and tricyclohexylphosphine oxide (Cy3PO) or tri‐tert‐butylphosphine oxide (tBu3PO) are described. The structures of [Ln(H2O)5(Cy3PO)2]·2R3PO·(OTf)3 (Ln = Pr, Tm; R = Cy and Ln = Nd; R = tBu) are pentagonal bipyramidal with an equatorial plane of five H2O ligands and two axial Cy3PO ligands. The remaining Cy3PO molecules are H‐bonded to the coordinated water molecules, as are the triflate anions. NMR spectroscopy showed that the triflate ions remain associated with the complexes in CDCl3 solution. Lanthanide‐induced shifts in the 19F and 31P NMR spectra confirm that one structure is present for all the lanthanides with an additional structure for the heavier metals. The acidity of the complexes was examined by 31P NMR spectroscopic studies on the reactions between [Ln(H2O)5(Cy3PO)2]·2Cy3PO·(OTf)3 (Ln = La, Eu, Er, Lu) and phosphines PR3 (R = Ph, mesityl, Cy), Ph2PC2H4PPh2 and Ph2PC3H6PPh2. Protonation of the more basic phosphines and H‐bonding to the less basic phosphines is observed.

The role of ligand basicity in complex formation has been investigated using monodentate pyridyls or benzimidazole (mP) in combination with a solution-stable species derived form a coordination polymer, [Cu(L)] (where L = 2-(2-hydroxybenzylidene-amino)phenol). The 12 [Cu(L)(mP)n] complexes generated, combined with the {[Cu(L)]2(pP)} complexes from our previous work (where pP is a polypyridyl ligand), allow us to gauge the likelihood of complex formation based on the pKa of the conjugate acid of the pyridyl ligands and Hammett parameter, σ. Above pKa ≈ 4.5, complexes are formed where the only ligands are L2- and mP or pP and the packing interactions are predominantly van der Waals. Below this value, complex formation is unlikely unless there are additional oxygen ligands in the Jahn-Teller axis of the Cu(ii) ion. The structures of two literature [Cu(L)(bP)] complexes, where bP is a chelating bidentate pyridyl ligand are also re-examined to resolve the positional disorder in the [Cu(L)] moiety.

A family of mono- and ditopic hydroxamic acids has been employed in the synthesis and structural and physical characterisation of discrete (0D) and (1- and 2-D) extended network coordination complexes. Examples of the latter include the 1-D coordination polymer {[Zn(ii)(L3H)2]·2MeOH}n (5; L3H2 = 2-(methylamino)phenylhydroxamic acid) and the 2-D extended network {[Cu(ii)(L2H)(H2O)(NO3)]·H2O}n (5; L2H2 = 4-amino-2-(acetoxy)phenylhydroxamic acid). The 12-MC-4 metallacrown [Cu(ii)5(L4H)4(MeOH)2(NO3)2]·3H2O·4MeOH (7) represents the first metal complex constructed using the novel ligand N-hydroxy-2-[(2-hydroxy-3-methoxybenzyl)amino]benzamide (L4H3). Variable temperature magnetic susceptibility studies confirm strong antiferromagnetic exchange between the Cu(ii) centres in 7. Coordination polymer 5 shows photoluminescence in the blue region (λPL ∼ 421-450 nm) with a bathochromic shift of the emission (∼15-30 nm) from solution to the solid state.

A method for the synthesis of pyridine derivativesbased on a triple cascade reaction catalyzed by chiral secondaryamines was developed. The resulting cyclohexenes (three C–C bonds were formed) were obtained in good yields with good diastereoselectivities and excellent enantioselectivities.

The structure of the complex formed between trimethylamine and iodine monochloride had been redetermined by a combination of neutron powder diffraction and X-ray single crystal diffraction techniques. The structure determined using NPD shows that the geometry of the trimethylamine moiety resembles that in trimethylammonium cations rather than in the free trimethylamine molecule. The structure shows the presence of weak C–D⋯Cl hydrogen bonds, The I–Cl bond length is in agreement with that derived from an analysis of the pKb values of a series of nitrogen bases and previously determined structures containing N⋯ICl fragments.

A novel alkyne-terminated cubic-octameric POSS was synthesised in high yield (82–90%). The X-ray crystal structure revealed intra- and intermolecular hydrogen bonding between the amide groups of the arms. Hybrid biomaterials were synthesised in nearly quantitative yields via a click reaction with (i) azido-N-Fmoc-norleucine and (ii) 3′-azido-3′-deoxythymidine.

The novel coordinate compounds T8[(CH2)n-EWG]8F–-18-crown-6-M+ were prepared by reaction of EWG-(CH2)n-Si(OEt)3 (where n = 1–3 and the electron-withdrawing group, EWG, contains an Si–C(sp3) bond) with an 18-crown-6-M+F– complex (where M+ is K+, Cs+, and Rb+) in the presence of a limited amount of water. The EWG facilitates the formation and encapsulation of the fluoride anion in a silsesquioxane cage. The reaction takes place by complexing an alkali metal in the crown ether, catalyzing silsesquioxane cage formation, and concomitant encapsulation of a fluoride ion within the final T8 cage. The reaction is simple and takes place in a single step with excellent yields of 81–95%. These novel materials have been studied by 19F and 29Si NMR spectroscopy and X-ray crystallography as well as by MALDI-TOF and ESI mass spectrometry. The T8[(CH2)n-EWG]8F–-18-crown-6-M+ compounds can be also synthesized by a facile reaction of 18-crown-6-M+F– with the corresponding T8[(CH2)n-EWG]8 cage in nearly quantitative yield. S...

8-Dimethylaminonaphthalene-1-carbaldehyde reacts readily at 0°C with benzoyl or pivaloyl chloride by O-acylation and formation of a N–C bond (1.566(2)–1.568(3) Å) between the peri-substituents to give a salt. The reaction is promoted by electron donation from the dimethylamino group to the carbonyl group, akin to the properties of an amide. In contrast, the corresponding methyl ester and N,N-diisopropylamide react with acid in ether by protonation of the dimethylamino group and formation of a hydrogen bond to the carbonyl group, while under similar conditions the N,N-dimethylamide undergoes ready hydrolysis to the acid. The structures of products are determined by X-ray crystallography, and from the latter hydrolysis crystals containing zwitterionic 1-dimethylammonium-naphthalene-8-carboxylate and the corresponding O-protonated cation along with dimethylammonium and triflate ions were obtained.

Previous employment of the ligands 2-methoxy-6-[(methylimino)methyl]phenol (L

International audience; Previous employment of the ligands 2-methoxy-6-[(methylimino)methyl]phenol (L1H) and 2-methoxy-6-[(phenylimino)methyl]phenol (L2H) has resulted in the self-assembly of pseudo metallocalix[6]arene complexes of general formulae: [M-7((3)-OH)(6)(L-x)(6)](NO3)(y) (M = Ni(ii), x = 1, y = 2 (1) and Co(ii/iii), x = 2, y = 3 (2)). Extrapolating upon this work, we report the coordination chemistry of ligands 2-methoxy-6-{[(2-methoxyphenyl)imino]methyl}phenol (L3H), 2-[(benzylimino)methyl]-6-methoxyphenol (L4H), 2-[(benzylamino)methyl]-6-methoxyphenol (L5H) and 2-[(benzylamino)methyl]-4-bromo-6-methoxyphenol (L6H), whose structures are modifications of ligands L1-2H. These ligands are employed in the synthesis and characterisation of the dimetallic complex [Ni(ii)(2)(L-3)(3)(H2O)](NO3)2H(2)O3MeOH (3); the monometallic complexes [Ni(ii)(L-4)(2)] (4) and [Co(iii)(L-4)(3)]H2OMeOH (5a); and the tetranuclear pseudo metallocalix[4]arene complexes: [(NO3)< subset of>Co(ii)(4)((3)-OH)(2)(L-5)(4)(H2O)(2)](NO3)H2O (6), [(NO3)< subset of>Ni(ii)(4)((3)-OH)(2)(L-5)(4)(H2O)(2)](NO3)H2O (7) and [Ni(ii)(4)((3)-OH)(2)(L-6)(4)(NO3)(2)]MeCN (8). The tetrametallic butterfly' core topologies in 6-8 are discussed with respect to their structural and topological relationship with their heptanuclear [M-7] (M = Co(ii), Ni(ii)) pseudo metallocalix[6]arene ancestors (1 and 2).

A systematic study of the cellular uptake of emissive complexes as a function of their lipophilicity is presented. Here a series of amphiphilic rhenium fac-tricarbonyl bisimine complexes bearing axial substituted imidazole or thiazole ligands, [Re(bpy)(CO)3(ImCnHm)]+ {n = 1 m = 3 (1+), n = 4 m = 9 (2+), n = 8 m = 17 (3+), n = 12 m = 25 (4+), n = 16 m = 33 (5+), n = 2 m = 3 (6+); bpy = 2,2'-bipyridine, Im = imidazole} and [Re(bpy)(CO)3(L)]+ {L = 1-mesitylimidazole, ImMes (7+), 4,5-dimethylthiazole, dmt (8+) and 4-methyl-5-thiazole-ethanol, mte (9+)} is reported. The X-ray crystal structures of 2+, 8+ and 9+ confirm the geometry and expected distribution of ligands and indicated that the plane of the imidazole/thiazole ring is approximately parallel to the long axis of the bipy ligand. Luminescence studies revealed excellent properties for their use in cell imaging with visible excitation and broad emission profiles. Their uptake in two distinct species has been examined by fluorescence imaging of the diplomonad fish parasite Spironucleus vortens (S. vortens) and rod-shaped yeast Schizosaccharomyces pombe (Schiz. pombe) as a function of their lipophilicity. The uptake of the complexes was highest for the more lipophilic 2+-5+ in both S. vortens and Schiz. pombe in which the long alkyl chain aids in crossing bilipid membranes. However, the increased lipophilicity of longer chains also resulted in greater toxicity. Localisation over the whole cell varied with differing alkyl chain lengths with complex 2+ preferentially locating to the nucleus of S. vortens, 3+ showing enhanced nuclear partitioning in Schiz. pombe, and 4+ for the remaining cell wall bound in the case of S. vortens. Interestingly, complexes of intermediate lipophilicity such as 7+ and 8+ showed reasonable uptake, proved to be non-toxic, and were capable of crossing exterior cell walls and localising in the organelles of the cells.

Crystal structures of the salts of 1,8-naphthalaldehydic acid (8-formyl-1-naphthoic acid) show one of two types of interaction between the functional groups. In the more commonly observed case, a carboxylate oxygen lies close to the aldehyde carbonyl carbon atom (O⋯C: 2.445–2.630 Å) and makes an n–pi* interaction. However, in two other cases the carboxylate group has rotated so that the aldehyde now directs its hydrogen atom at the face of the carboxylate group and forms a surprisingly short contact with the carbon atom (H⋯C: 2.29 and 2.42 Å). This interaction is likely to be electrostatic in nature.

The reaction of the simple metalloligand [Fe

The rich landscape of enantiotropically related polymorphic forms and their solid-state phase transitions of dl-2-aminoheptanoic acid (dl-AHE) has been explored using a range of complementary characterization techniques, and is largely exemplary of the polymorphic behavior of linear aliphatic amino acids. As many as five new polymorphic forms were found, connected by four fully reversible solid-state phase transitions. Two low temperature forms were refined in a high Z′ crystal structure, which is a new phenomenon for linear aliphatic amino acids. All five structures consist of two-dimensional hydrogen-bonded bilayers interconnected by weak van der Waals interactions. The single-crystal-to-single-crystal phase transitions involve shifts of bilayers and/or conformational changes in the aliphatic chain. Compared to two similar phase transitions of the related amino acid dl-norleucine, the enthalpies of transition and NMR chemical shift differences are notably smaller in dl-aminoheptanoic acid. This is explained to be a result of both the nature of the conformational changes and the increased chain length, weakening the interactions between the bilayers.

Recent elegant examples illustrate the power of charge density analysis, employed in a systematic way, to link electron density distribution to molecular structure. This leads to new insights into important chemical systems and the effects of systematic modifications to them. The advances made in extracting the electron density distribution from standard resolution X-ray diffraction data and the subsequent use of this information in systematic studies are also described.

A combination of NMR spectroscopy, mass spectrometry and chemical synthesis was used to elucidate the two-step hydrolytic decomposition pathway of the slow-release hydrogen sulfide (H2S) donor GYY4137 and the key decomposition product was also prepared by an independent synthetic route. The (dichloromethane-free) sodium salt of the phosphonamidodithioate GYY4137 was also produced as a pharmaceutically more acceptable salt. In contrast with GYY4137 and its sodium salt, the decomposition product did not generate H2S or exert cytoprotective or anti-inflammatory effects in oxidatively stressed human Jurkat T-cells and LPS-treated murine RAW264.7 macrophages. The decomposition product represents a useful control compound for determining the biological and pharmacological effects of H2S generated from GYY4137.

A zwitterionic tetrahydrothiophen-3-one derivative containing the enolate of a -keto ester located in the ring and a tetramethylamidinium group in a side chain is formed from tetramethylthiourea and dimethyl acetylenedicarboxylate by a surprising rearrangement reaction. Low-temperature X-ray crystallography shows weak intramolecular coordination of an enolate O atom by the amidinium group (OC: 2.608 angstrom) and also a 1,5 SO short contact (2.706 angstrom) due to electron delocalisation in a cis-sulfanylacrylate grouping

N,O-ligated Pd(II) complexes show considerable promise for the oxidation of challenging secondary aliphatic alcohols. The crystal structures of the highly active complexes containing the 8-hydroxyquinoline-2-carboxylic acid (HCA) and 8-hydroxyquinoline-2-sulfonic acid (HSA) ligands have been obtained. The (HSA)Pd(OAc)2 system can effectively oxidise a range of secondary alcohols, including unactivated alcohols, within 4–6 h using loadings of 0.5 mol%, while lower loadings (0.2 mol%) can be employed with extended reaction times. The influence of reaction conditions on catalyst degradation was also examined in these studies.

The complexes formed on reaction of tri-isopropylphosphine oxide ((C3H7)(3)PO = (Pr3PO)-Pr-i = L) and lanthanide nitrates have been studied. The new compounds have been characterised by elemental analysis, infrared and P-31 NMR spectroscopy in CD2Cl2 solution. On reaction of lanthanide nitrates and L in 1:3 ratios, well defined Ln(NO3)(3)L-3 are obtained for Ln = La-Eu with complexes for the heavier lanthanides forming mixtures of Ln(NO3)(3)L-3 and Ln(NO3)(3)L-2. Analytically pure complexes Ln(NO3)(3)L-2 can be isolated for Yb and Lu. Single crystal X-ray structures for Ln(NO3)(3)L-3, Ln = La (1), Ce (2), Pr (3), the ionic complex [Er(NO3)(2)L-3(H2O)][NO3] (4) and Ln(NO3)(3)L-2, Ln = Yb (5), Lu (6) are reported. The P-31 solution NMR spectra of Ln(NO3)(3)L-3 show that the complexes are fluxional at ambient temperature with spectra consistent with static structures observed at lower temperatures for some complexes. The structures and solution properties are discussed in terms of the steric and electronic properties of the ligand.

This paper reports the synthesis of a series of new half-squaraine dyes (Hf-SQ) based around a common chromophoric unit consisting of linked indoline and squaric acid moieties. Carboxylate groups have been incorporated onto this core structure at four different points to study the influence of the anchoring group position on dye-sensitized solar cell (DSC) device performance. Dyes have been linked to TiO2 directly through the squaric acid moiety, through a modified squaric acid unit where a vinyl dicyano group has replaced one carbonyl, via an alkyl carboxylate attached to the indole N or through a carboxylate attached to the 4 position of a benzyl indole. Contact angle measurements have been studied to investigate the hydrophobic/hydrophilic properties of the dyes and the results have been compared to N719 and Z907. Full characterization data of all the dyes and synthetic intermediates are reported including single-crystal X-ray structural analysis for dye precursors; the indole (2a) and the half-squarylium esters (3a) and (6b), as well as the dyes (4c), (8) and (12). Dye colours range from yellow to red/brown in solution (lambda(max) range from 430 to 476 nm) with 3 ranging from 38 000 to 133 100 M-1 cm(-1). The performance of the dyes in DSCs shows the highest efficiency yet reported for a Hf-SQ dye (eta = 5.0%) for 1 cm(2) devices with a spectral response ranging from 400 to 700 nm depending on the dye substituents. Co-sensitization of half-squarylium dye (7b) with squaraine dye (SQ2) resulted in a broader spectral response and an improved device efficiency (eta = 6.1%). Density functional theory (DFT) calculations and cyclic voltammetry have been used to study the influence of linker position on dye HOMO-LUMO levels and the data has been correlated with I-V and EQE data.

Stereoregular all-cis cyclotetrasiloxanes [R-Si(O)-R′]4 with different functional groups attached to the opposite faces of the ring skeleton were derivatized without stereoisomerization or cleavage of the (SiO)4 ring and with high selectivity using standard synthetic methods. The solid-state structures obtained for the iodophenyl-substituted starting material 16 ([p-I-C6H4-Si(O)-OSiMe2Vin]4) and for the coupling product 21 ([biphenyl-CC-C6H4-Si(O)-OSiMe2Vin]4) show a pronounced differentiation in the steric requirements of the different sides of the ring, resulting in characteristic crystal packing. In combination with the observed high thermal and chemical stability, these data demonstrate the high potential of cyclotetrasiloxanes for a wide range of applications.

The anion-templated synthesis of a rotaxane structure, incorporating the new naphthalimide triazolium motif, is described and the interlocked host shown to exhibit selective, uni-directional, anion-induced shuttling. Initial pseudorotaxane investigations demonstrate the ability of a naphthalimide triazolium threading component to form interpenetrated assemblies with counter-anion-dependent co-conformations. (1)H NMR studies reveal that the shuttling behaviour of the analogous rotaxane host system is controlled by selective anion binding and by the nature of the solvent conditions. Complete macrocycle translocation only occurs upon the recognition of the smaller halide anions (chloride and bromide). The rotaxane solid-state crystal structure in the presence of chloride is in agreement with the solution-phase co-conformation. The sensitivity of the axle naphthalimide absorbance band to the position of the macrocycle component within the interlocked structure enabled the molecular motion to be observed by UV/Vis spectroscopy, and the chloride-induced shuttling of the rotaxane was reversed upon silver hexafluorophosphate addition.

A series of heterometallic coordination clusters (CCs) [Ni(II)2Ln(III)2(L1)4Cl2(CH3CN)2] 2CH3CN [Ln = Y (1Y), Sm (1Sm), Eu (1Eu), Gd (1Gd), or Tb (1Tb)] were synthesized by the reaction of (E)-2-(2-hydroxy-3-methoxybenzylidene-amino)phenol) (H2L1) with NiCl2·6(H2O) and LnCl3·x(H2O) in the presence of Et3N at room temperature. These air-stable CCs can be obtained in very high yields from commercially available materials and are efficient catalysts for the room-temperature domino ring-opening electrocyclization synthesis of trans-4,5-diaminocyclopent-2-enones from 2-furaldehyde and primary or secondary amines under a non-inert atmosphere. Structural modification of the catalyst to achieve immobilization or photosensitivity is possible without deterioration in catalytic activity.

The ability of phosphonium cations to act as intracellular transport vectors is well-established. Phosphonioalkylthiosulfate zwitterions, and (omega)-thioacetylalkylphosphonium salts, which act as 'masked thiolate' ligands, are useful precursors for the formation of phosphonium-functionalised gold nanoparticles, enabling the nanoparticles to be transported into cells for diagnostic and therapeutic purposes. In this study we have completed cytotoxicity studies of (omega)-thioacetylpropylphosphonium salts derived from triphenylphosphine and tri(4-fluorophenyl)phosphine, which show that the compounds are only toxic towards PC3 prostate cancer cells at high concentrations and at prolonged incubation periods and display IC50 values of 67uM and 252uM respectively, significantly higher than those of other phosphonium salts. MALDI-TOF-MS has been used to investigate the uptake of the compounds by PC3 cells and to quantify detectable levels of the compounds inside the cells. The structures of (omega)-thioacetylpropyl(tri-4-fluorophenyl) phosphonium bromide and the corresponding tri(4-fluorophenyl)phosphonio-propylthiosulfate zwitterion have been investigated by single crystal X-ray crystallography. The results show that molecules of the zwitterion are held together through an extensive array of electrostatic and non-covalent interactions. The unit cell of (omega)-thioacetylpropyl(tri-4-fluorophenyl)phosphonium bromide contains eight cations together with eight bromide anions and two waters of crystallisation, all held together through a complex network of hydrogen bonds. The differences in the molecular packing of the two compounds may account for the lower solubility of the zwitterion in aqueous solutions, compared with that of the phosphonium salt.

The first molecular capsule based on an [Ir(ppy)(2)](+) unit (ppy = 2-phenylatopyridine) has been prepared. Following development of a method to resolve rac-[(Ir(ppy)(2)Cl)(2)] into its enantiopure forms, homochiral Ir6L4 octahedra where obtained with the. tritopic 1,3,5-tricyanobenzene. Solution studies and X-ray diffraction show that-these capsules;encapsulate four of the six associated counteranions and that these can be exchanged for other anionic guests Initial photophysical studies have shown that an ensemble of weakly. coordinating ligands can lead to luminescence not present in comparable mononuclear systems.

The crystallization of 5-nitrouracil (5NU) from pure aqueous solution yields two anhydrous polymorphs and a monohydrate depending on the temperature at which the process is carried out. 5NU mimics true polymorphism in that, when retained in aqueous solution, both metastable (anhydrous) forms undergo solvent mediated phase transformations (SMPTs) into the more thermodynamically stable hydrated form as would be predicted by Ostwald’s rule of stages. The phase transformations can occur either in the classical manner of dissolution and recrystallization or, in one case, may in some circumstances be nucleated and morphologically templated by the original crystalline form. There is no appearance from aqueous solution of a known third acentric anhydrous form, previously prepared from acetonitrile solutions. Preliminary experiments suggest this nonappearance may result from the relatively high solubility of this form in aqueous solution.

The 6-azabicyclo[3.2.1]octane ring system, prevalent in a range of biologically active molecules, is prepared through a novel semipinacol rearrangement utilizing a cyclic phosphorane or sulfite intermediate. The rearrangement proceeds with exclusive N-acyl group migration of a β-lactam ring and results in carbonyl functionality at the 7- and bridging 8-position of the bicycle. Precursor ring-fused β-lactam diols are prepared through a sequence of 4-exo trig carbamoyl radical cyclization, regioselective dithiocarbamate group elimination, and dihydroxylation.

Reaction of lanthanide nitrates with (t)Bu(3)PO (=L) lead to the isolation of complexes Ln(NO(3))(3)L(2)·H(2)O·nEtOH (Ln = La (1), Nd(2)), Ln(NO(3))(3)L(2) ·nEtOH (Sm(3), Eu(4)), and Ln(NO(3))(3)L(2) (Dy(5), Er(6), Lu(7)). These have been characterized by elemental analysis, infrared and NMR((1)H, (13)C and (31)P) spectroscopy and single-crystal X-ray diffraction. The structures show L to be positioned on opposite sides of the metal with the nitrates forming an equatorial band. When Ln = Dy, Er, and Lu two distinct molecules are present in the unit cell. A major isomer (70%) has a (P)O-Ln-O(P) angle of less than 180° with one of the nitrate ligands twisted out of the plane of the other nitrates while the lower abundance isomer is more symmetric with the (P)O-Ln-O(P) angle of 180° and the nitrate ligands coplanar giving a hexagonal bipyramidal geometry. These isomers cannot be observed by variable temperature solution (31)P NMR measurements but are clearly seen in the solid-state NMR spectrum of the Lu complex. Variable temperature solid-state NMR indicates that the isomers do not interconvert at temperatures up to 100 °C. Attempts to prepare cationic species [Ln(NO(3))(2)L(3)](+)[PF(6)](-) have not been totally successful and led to the isolation of crystals of Lu(NO(3))(3)L(2) and Tb(NO(3))(3)L(2).CH(3)CN (8).

The structure of 2-(2-pyridylimino)-2H-1,2,4-thiadiazolo[2,3-a]pyridine (NSN) indicates that the molecule has a planar geometry with a linear N···S···N linkage, creating a tetracyclic structure of the formal C2v symmetry. To clarify the nature of the NSN σ(3c–4e) bonding, together with the related NSeN and NTeN, the dynamic and static behaviors are investigated by applying atoms-in-molecules (AIM) dual functional analysis to both the fully optimized and perturbed structures. The structures were optimized computationally, retaining C2v symmetry. All bond critical points are detected as expected and exhibited on both sides of the N···Z···N moiety which supports the formation of NZN σ(3c–4e). It is confirmed that N···S···N is of the covalent nature close to Me2S+-∗-Cl or Me2Se+-∗-Br, whereas N···Se···N and N···Te···N have the (regular) CS nature close to the CT adducts of Me2S(-∗-Cl)2 (TBP) and Me2Se-∗-Br2 (MC), respectively. An experimental high-resolution charge density determination has been performed on ...

The experimental electron density study of Ti(C(5)H(4)Me)(2)[(CH(2))(2)CMe(2)] provides direct evidence for the presence of (C-C)--Ti agostic interactions. In accord with the model of Scherer and McGrady, the C(alpha)-C(beta) bond densities no longer show cylindrical symmetry in the vicinity of the Ti atom and differ markedly from those of the other C-C bonds. At the points along the C(alpha)-C(beta) bond where the deviation is maximal the electron density is elongated toward the metal center. The distortion is supported by parallel theoretical calculations. A calculation on an Mo complex in which the agostic interaction is absent supports the Scherer and McGrady criterion for agostic interactions. Despite the formal d(0) electron configuration for this Ti(IV) species, a significant nonzero population is observed for the d orbitals, the d orbital population is largest for the d(xy) orbital, the lobes of which point toward the two C(alpha) atoms. Of the three different basis sets for the Ti atom used in theoretical calculations with the B3LYP functional, only the 6-311++G** set for Ti agrees well with the experimental charge density distribution in the Ti-(C(alpha)-C(beta))(2) plane.

While it is now well-documented that the synthetic (17α-ethinylestradiol, EE2) and natural (17β-estradiol, E2) estrogens are among the most potent endocrine-disrupting chemicals found in the environment, many of their transformation products (TPs) have not been identified to date. The scarcity of available environmental data on the TPs of EE2 and E2 can be attributed to the difficulty in analyzing trace amounts of previously unknown compounds in the presence of complex environmental matrices. This article presents an overview of current knowledge on the TPs identified from biotic and abiotic degradation studies for these two estrogens and provides a list of the structures of TPs that have been identified to date, resulting from the biodegradation, ozonation, and oxidation of EE2 and E2. We also present the application of liquid chromatography with mass spectrometry (LC-MS), in conjunction with nuclear magnetic resonance spectroscopy (NMR) and X-ray crystallography, in identifying biotic and abiotic TPs of EE2 formed in pure cultures of Nitrosomonas europaea to illustrate how these instrumental techniques can complement each other to identify TPs of estrogens unambiguously.

et al., Keplerates are molecules that contain metal polyhedra that describe both Platonic and Archimedean solids; new copper keplerates are reported, with physical studies indicating that even where very high molecular symmetry is found, the low-temperature physics does not necessarily reflect this symmetry. New copper keplerates are reported, with physical studies indicating that even where very high molecular symmetry is found, the low-temperature physics does not necessarily reflect this symmetry., This work was supported by the EPSRC (UK), including the National EPR Facility, the National Crystallographic Service and for funding an X-ray diffractometer (grant number EP/K039547/1). EMP thanks the Panamanian agency SENACYT-IFARHU for funding. ME acknowledges financial support from MINECO through grant MAT2012-38318-C03-01. REPW thanks the Royal Society for a Wolfson Merit Award.JS thanks the Deutsche Forschungsgemeinschaft (SCHN/615-15)for continuous support. CH and JS thank for support through an exchange program between Germany and Bulgaria (DAAD PPP Bulgarien 57085392 &DNTS/Germany/01/2). Supercomputing time at the LRZ Garching is gratefully acknowledged. HN acknowledges financial support through a ICC-IMR project.

The synthesis, structural and magnetic characterisation of a family of related Cr(iii) cages are reported. Each member comprises {Cr(iii)3O(O2CR1)3(R2-sao)3}2- (R1 = H, CH3, C(CH3)3, C14H9; R2 = Me, Ph, tBu, C10H8) triangles linked by Na+ cations, resulting in either the discrete complexes [H3O][NEt4]2[NaCr(iii)6O2(O2C-C14H9)6(Naphth-sao)6] (1) and [Na4Cr(iii)6O2(O2CC(CH3)3)6(3,5-di-tBu-sao)6(MeCN)6] (3); or the extended networks [H3O]2[Na2Cr(iii)6O2(O2CH)6(Ph-sao)6(MeCN)2(H2O)2]n·4MeCN (2); [H3O][Na3Cr(iii)6O2(O2CCH3)6(Me-sao)6(MeCN)]n (4) and [Na2Cr(iii)3O(O2CCH3)3(Me-sao)3(H2O)6]n·3MeCN (5). Magnetic susceptibility data obtained for 2 and 4 reveal weak antiferromagnetic exchange between the Cr(iii) ions in the triangles.

Reactions of 4′-(4- n alkyloxyphenyl)-4,2′:6′,4″-terpyridines (alkyl = hexyl or nonyl) with CoIJNCS) 2 lead to three structurally characterized chiral 3D assemblies which adopt rare neb topologies. For the n hexyl-functionalized ligands, both enantiomorphic lattices of the neb nets (crystallizing in the tetragonal space groups P4 1 2 1 2 and P4 3 2 1 2, respectively) are presented

We consider the roles of heteroatoms (mainly nitrogen, the halogens and the chalcogens) in dictating the conformation of linear conjugated molecules and polymers through non-covalent intramolecular interactions. Whilst hydrogen bonding is a competitive and sometimes more influential interaction, we provide unambiguous evidence that heteroatoms are able to determine the conformation of such materials with reasonable predictability.

A family of Mn-III dimers of general formula [Mn-2(III)(R-sao)(2)(dpa)(2)](ClO4)(2) (1-5) has been synthesised using derivatised phenolic oximes (R-saoH(2), where R = H, Me, Et, Ph) in combination with di-(2-picolyl)-amine (dpa). Their structures reveal a double-oxime bridged [Mn-III(NO)](2) magnetic core in which the Jahn-Teller axes lie perpendicular to the bridging plane, in contrast to two previously reported family members (6, 7). The switch in the orientation of the Jahn-Teller axes is enforced through the use of the chelating ligand which is present in 1-5 and absent in 6-7. Dc magnetic susceptibility measurements reveal that the exchange interactions between the MnIII metal centres in 1-5 are antiferromagnetic in contrast to that observed for 6 and 7 which are ferromagnetic. DFT calculations performed on complexes 1-6 reproduce both the sign and strength of the J values found experimentally. Molecular orbital analysis unlocks a common mechanism of magnetic coupling based upon the orientation of the Jahn-Teller axis, with the magneto-structural correlation also dependent upon the Mn-N-O-Mn angles - with ferromagnetic interactions at smaller dihedral angles.

The in situ formation and subsequent Cu(II) ligation of the polydentate pro-ligands o-[(E)-(2-hydroxy3- methoxyphenyl) methylideneamino] benzohydroxamic acid (L1H3), o-[(E)-(2-hydroxy-3-methoxy-5-bromophenyl) methylideneamino] benzohydroxamic acid (L2H3) and o-[(E)-(2-hydroxyphenyl) methylideneamino] benzohydroxamic acid (L3H3), leads to the self-assembly of the cages [Cu(II)(10)(L-1)(4)(2-aph)(2)(H2O)(2)](ClO4)(4)center dot 5MeOH (1), [Cu(II)(14)(L-1)(8)(MeOH)(2.5)(H2O)(7.5)](NO3)(4)center dot 3MeOH center dot 7H(2)O (2), [Cu(II)(14)(L-2)(8)(MeOH)(4)(H2O)(6)](NO3)(4)center dot 6H(2)O (3), [Cu(II)(14)(L-3)(8)(MeOH)(6)(H2O)(2)](NO3)(4)center dot 4MeOH center dot 8H(2)O (4) and [Cu(II)(30)O(OH)(4)(OMe)(2)(L-1)(16)(MeOH)4(H2O)(2)](ClO4)(4)center dot 2MeOH center dot 30H(2)O (5). Each member comprises a highly unusual topology derived from off-set, stacked, near planar layers of polynuclear subunits connected through long Cu(II)-O contacts. The exact topology observed is dependent on the specific reaction conditions and methodologies employed. Dc magnetic susceptibility studies on 1, 2, 4 and 5 reveals strong antiferromagnetic exchange between the Cu(II) centres in all siblings. We also present the 1D coordination polymer {[Cu(II)(L-4)]center dot H2O}(n) (6) comprising the pseudo macrocyclic ligand [[2-[(E)-(2-hydroxy-3-methoxyphenyl) methyleneamino] benzoyl] amino] ethanimidate (L4H2), which is formed upon the incorporation of an MeCN unit at the hydroxamate group of precursor ligand L1H3.

The reaction proceeds with low diastereoselectivity and all products are isolated as mixtures of diastereomers.

Recent elegant examples illustrate the power of charge density analysis, employed in a systematic way, to link electron density distribution to molecular structure. This leads to new insights into important chemical systems and the effects of systematic modifications to them. The advances made in extracting the electron density distribution from standard resolution X-ray diffraction data and the subsequent use of this information in systematic studies are also described.

The crystals of two new salts containing 1-(4-hydroxyphenyl)-2,4,6-triphenyl-pyridinium cations and biphenyl-4-sulfonic or 4-aminobenzenesulfonic acid counterions were determined by X-ray diffraction. 4-(2,4,6-triphenylpyridinium-1-yl)-phenolate itself is interesting because of its large negative solvatochromic effect. The salts were obtained from ethanol solution with the following chemical composition: 2C 29 H 21 NO·2C 12 H 10 O 3 S·C 2 H 6 O ( 2 ) and 3C 29 H 21 NO·3C 6 H 7 NO 3 S·3C 2 H 6 O·H 2 O ( 3 ) as found by crystal structure analysis. Both salts crystallize in monoclinic centrosymmetric space groups ( P 2 1 / c and P 2 1 / n , respectively). The hydroxyl group of the cation serves in these structures as a donor for strong hydrogen bond. Symmetrically independent molecules form hydrogen bonds with different acceptors. In this work, some important aspects of the studied structures are discussed: an antiparralel arrangement of the molecules, relationships between various molecular geometrical parameters and acceptor/donor behaviour of the phenolate O − /OH substituent in different crystal (solvent) environments.

Building on previous studies of anion-receptor complexes based on a urea scaffold substituted symmetrically with electron-withdrawing nitro groups, the electron density distribution in an analogousthiourea receptor complex and the related asymmetrically substituted urea and thiourea receptors are described. On this basis it is possible to probe both the effect of changing the receptor core from a urea to10 a thiourea moiety and that of asymmetrical substitution of the receptor molecule. These modifications are shown to significantly alter the anion binding properties, solid-state packing and electron density distribution in the anion-receptor complexes.

The novel nucleoside 5-iodo-4-thio-2′-deoxyuridine (4) was synthesized and fully characterized by IR, NMR, and MS. Its structure was determined by single-crystal X-ray diffraction. Compound 4 absorbs strongly at 346 nm and is minimally toxic to human tumour cells, but its cytotoxicity is substantially enhanced by low dose UVA radiation. The combined use of 4 and UVA offers a promising route to selectively and effectively kill proliferating cells.

This is the first study on electron density distribution of urea and dicarboxylic acids co-crystals. The accurate electron density of two co-crystals of urea with oxalic acid and l-malic acid molecules is discussed, on the basis of high-resolution X-ray diffraction data collected at 80(2) K, and compared with density functional theory calculations in a crystal structure as well as in the gas phase. Rigid dicarboxylic acid favors two-dimensional planar hydrogen bond networks, whereas flexible acid promotes layers with helical arrangements of those molecules. The nature of chemical bonding is investigated using topological analysis based on quantum atoms in molecules theory, Hirshfeld analysis, noncovalent interactions approach, distributed atomic polarizabilities and electrostatic potential. In a co-crystal of oxalic acid and urea, uncommon carbonyl···carbonyl interaction is observed, representing an antiparallel motif between oxalic and urea molecules, which was so far identified only between the same mol...

The synthesis and full characterization of new half-squaraine dyes (Hf-SQ) containing two or three carboxylate-based linker units is reported and these dyes tested in dye-sensitized solar cell (DSC) devices. The data show improved device efficiency for a Hf-SQ dye with two linkers (η = 5.5%) compared to the highest efficiency Hf-SQ previously reported which had only a single linker (η = 5.0%); this is mainly due to improved Voc. To understand the effects of using multiple dye linker groups, device I–V data have been correlated with single crystal X-ray structural analysis and dye electrical properties (both in solution and adsorbed to TiO2) using UV-visible and ATR-IR spectroscopy along with cyclic voltammetry, and also theoretical studies using density functional theory (DFT) calculations. These data show that positioning the linkers near the dye LUMO and so that this enables complete linker chemisorption are key factors for device performance.

A novel catalytic enantioselective methodology based on synergistic catalysis is reported. The strategy involves: 1) the metal-Lewis-acid activation of alkylazaarenes, and 2) the secondary-amine activation of enals. Consequently, highly functionalized chiral alkylazaarenes were obtained in good yields and with reasonable stereoselectivity.