Drug prevention and schools: a comparison of current drug education in Luton high schools with the advice given in the DFE Circular 4/95

Drug prevention and schools: a comparison of current drug education in Luton high schools with the advice given in the DFE Circular 4/9

Synthesis of the I–K Fused Polyether Array of CTX3C and Related Ciguatoxins by Use of a Gold-Catalyzed Cyclization Reaction

The I–K fragment (C31–C49) of the ciguatoxin CTX3C has been synthesized from a simple chiral pool derived tetrahydropyranyl alcohol. An efficient gold-catalyzed cyclization reaction of a γ′-hydroxy ynone has been used to accomplish efficient closure of ring K under mild conditions. The resulting vinylogous ester has been elaborated to give a complete tricyclic fragment bearing the dimethyl-substituted side chain required for assembly of the LM spirocyclic acetal portion of the target

Furosemide Cocrystals: Structures, Hydrogen Bonding, and Implications for Properties

In this paper, we report the crystal growth of four cocrystals of furosemide (4-chloro-2-[(2-furanylmethyl)­amino]-5-sulfamoylbenzoic acid), a loop diuretic drug used for the treatment of hypertension and edemas, prepared with <i>p</i>-aminobenzoic acid, nicotinamide, and isonicotinamide as coformers. We present four new crystal structures and elucidate the intermolecular interactions present in the cocrystals. The structures display interesting supramolecular chemistry: a number of different synthons, as well as short strong hydrogen bonds with partial proton transfer and indications of proton disorder. Using powder X-ray diffraction, solid state NMR, and thermal analysis, we provide evidence for the preparation of bulk samples of two compositions, namely, the 1:1 cocrystal of furosemide and <i>p</i>-aminobenzoic acid and 2:1 cocrystal of furosemide and isonicotinamide, highlighting the general necessity of such multitechnique approaches to characterize organic solids (including cocrystals and solvates) prepared by grinding methods. Finally, we correlate the structural features reported for the first time in this work with the previously published pharmacologically relevant properties (solubility and intrinsic dissolution rate) of the furosemide cocrystals

Synthetic Considerations in the Self-Assembly of Coordination Polymers of Pyridine-Functionalized Hybrid Mn-Anderson Polyoxometalates

The incorporation of polyoxometalates (POMs) as structural units into ordered porous constructs such as metal–organic frameworks (MOFs) is desirable for a range of applications where intrinsic properties inherited from both the MOF and POM are utilized, including catalysis and magnetic data storage. The controlled self-assembly of targeted MOF topologies containing POM units is hampered by the wide range of oxo and hydroxo units on the peripheries of POMs that can act as coordinating groups toward linking metal cations leading to a diverse range of structures, but incorporation of organic donor units into hybrid POMs offers an alternative methodology to programmably synthesize POM/MOF conjugates. Herein, we report six coordination polymers obtained serendipitously wherein Zn²⁺ and Cu²⁺ link pyridine-appended Mn-Anderson clusters into two- and three-dimensional network solids with complex connectivities and topologies. Careful inspection of their solid-state structures has allowed us to identify common structure-directing features across these coordination polymers, including a square motif where two Zn²⁺ cations bridge two POMs. By correlating certain structural motifs with synthetic conditions, we have formulated a series of design considerations for the self-assembly of coordination polymers of hybrid POMs, encompassing the selection of reaction conditions, coligands, and linking metal cations. We anticipate that these synthetic guidelines will inform the future assembly of hybrid POMs into functional MOF materials

Symes_Supplementary information_ESM.doc from An investigation into the unusual linkage isomerization and nitrite reduction activity of a novel tris(2-pyridyl) copper complex

1H and 13C NMR spectra of compound 1, deconvoluted calculated IR spectra for [Cu1(NO2)2] and additional crystallographic data for [Cu1(NO2)2]

SO₂ Phototriggered Crystalline Nanomechanical Transduction of Aromatic Rotors in Tosylates: Rationalization via Photocrystallography of [Ru(NH₃)₄SO₂X]tosylate₂ (X = pyridine, 3‑Cl-pyridine, 4‑Cl-pyridine)

Thermally reversible solid-state linkage SO₂ photoisomers of three complexes in the [Ru­(NH₃)₄SO₂<b>X</b>]­tosylate₂ family are captured in their metastable states using photocrystallography, where <b>X</b> = pyridine (<b>1</b>), 3-Cl-pyridine (<b>2</b>), and 4-Cl-pyridine (<b>3</b>). This photoisomerism exists only in the single-crystal form; accordingly, the nature of the crystalline environment surrounding the photoactive species controls its properties. In particular, the structural role of the tosylate anion needs to be understood against possible chemical influences due to varying the <i>trans</i> ligand, <b>X</b>. The photoexcited geometries, photoconversion levels, and thermal stabilities of the photoisomers that form in <b>1</b>–<b>3</b> are therefore studied. <b>1</b> and <b>2</b> yield two photoisomers at 100 K: the O-bound end-on η¹-SO₂ (MS1) configuration and the side-bound η²-SO₂ (MS2); <b>3</b> exhibits only the more thermally stable MS2 geometry. The decay kinetics of the MS2 geometry for <b>1</b>–<b>3</b> demonstrate that the greater the free volume of the GS SO₂ ligand for a given counterion, the greater the MS2 thermal stability. Furthermore, a rationalization is sought for the SO₂ phototriggered molecular rotation of the phenyl ring in the tosylate anion; this is selectively observed in <b>2</b>, manifesting as nanomechanical molecular transduction. This molecular transduction was not observed in <b>1</b>, despite the presence of the MS1 geometry due to the close intermolecular interactions between the MS1 SO₂ and the neighboring tosylate ion. The decay of this anionic molecular rotor in <b>2</b>, however, follows a nontraditional decay pathway, as determined by time-resolved crystallographic analysis; this contrasts with the well-behaved first-order kinetic decay of its MS1 SO₂ phototrigger

About Living Water

Many of the desirable properties of metal–organic frameworks (MOFs) can be tuned by chemical functionalization of the organic ligands that connect their metal clusters into multidimensional network solids. When these linker molecules are intrinsically fluorescent, they can pass on this property to the resultant MOF, potentially generating solid-state sensors, as analytes can be bound within their porous interiors. Herein, we report the synthesis of a series of 14 interpenetrated Zr and Hf MOFs linked by functionalized 4,4′-[1,4-phenylene-bis­(ethyne-2,1-diyl)]-dibenzoate (peb^2–) ligands, and we analyze the effect of functional group incorporation on their structures and properties. Addition of methyl, fluoro, naphthyl, and benzo­thia­diazolyl units does not affect the underlying topology, but induces subtle structural changes, such as ligand rotation, and mediates host–guest interactions. Further, we demonstrate that solid-state photoluminescence spectroscopy can be used to probe these effects. For instance, introduction of naphthyl and benzo­thia­diazolyl units yields MOFs that can act as stable fluorescent water sensors, a dimethyl modified MOF exhibits a temperature dependent phase change controlled by steric clashes between interpenetrated nets, and a tetrafluorinated analogue is found to be superhydrophobic despite only partial fluorination of its organic backbone. These subtle changes in ligand structure coupled with the consistent framework topology give rise to a series of MOFs with a remarkable range of physical properties that are not observed with the ligands alone

Dynamics of Ground and Excited State Vibrational Relaxation and Energy Transfer in Transition Metal Carbonyls

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 rates in the solvated ³CT state are surprisingly solvent-insensitive, which suggests that predominantly intramolecular effects are responsible for the rapid vibrational deactivation. The increased VR rates in the excited state are discussed in terms of intramolecular electrostatic interactions helping overcome structural and thermodynamic barriers for this process in the vicinity of the central heavy atom, a feature which may be of significance to nonequilibrium photoinduced processes observed in transition metal complexes in general

Systematic and Controllable Negative, Zero, and Positive Thermal Expansion in Cubic Zr_1–<i>x</i>Sn_<i>x</i>Mo₂O₈

We describe the synthesis and characterization of a family of materials, Zr_1–<i>x</i>Sn_<i>x</i>Mo₂O₈ (0 < <i>x</i> < 1), whose isotropic thermal expansion coefficient can be systematically varied from negative to zero to positive values. These materials allow tunable expansion in a single phase as opposed to using a composite system. Linear thermal expansion coefficients, α_l, ranging from −7.9(2) × 10^–6 to +5.9(2) × 10^–6 K^–1 (12–500 K) can be achieved across the series; contraction and expansion limits are of the same order of magnitude as the expansion of typical ceramics. We also report the various structures and thermal expansion of “cubic” SnMo₂O₈, and we use time- and temperature-dependent diffraction studies to describe a series of phase transitions between different ordered and disordered states of this material

Redox Non-innocence of Thioether Crowns: Elucidation of the Electronic Structure of the Mononuclear Pd(III) Complexes [Pd([9]aneS₃)₂]³⁺ and [Pd([18]aneS₆)]³⁺

The Pd­(II) complexes [Pd([9]­aneS₃)₂]­(PF₆)₂·2MeCN (<b>1</b>) ([9]­aneS₃ = 1,4,7-trithiacyclononane) and [Pd([18]­aneS₆)]­(PF₆)₂ (<b>2</b>) ([18]­aneS₆ = 1,4,7,10,13,16-hexathiacyclooctadecane) can be oxidized electrochemically or chemically oxidized with 70% HClO₄ to [Pd([9]­aneS₃)₂]³⁺ and [Pd([18]­aneS₆)]³⁺, respectively. These centers have been characterized by single crystal X-ray diffraction, and by UV/vis and multifrequency electron paramagnetic resonance (EPR) spectroscopies. The single crystal X-ray structures of [Pd^III([9]­aneS₃)₂]­(ClO₄)₆·(H₃O)₃·(H₂O)₄ (<b>3</b>) at 150 K and [Pd([18]­aneS₆)]­(ClO₄)₆·(H₅O₂)₃ (<b>4</b>) at 90 K reveal distorted octahedral geometries with Pd–S distances of 2.3695(8), 2.3692(8), 2.5356(9) and 2.3490(6), 2.3454(5), 2.5474(6) Å, respectively, consistent with Jahn–Teller distortion at a low-spin d⁷ Pd­(III) center. The Pd­(II) compound [Pd([9]­aneS₃)₂]­(PF₆)₂ shows a one-electron oxidation process in MeCN (0.2 M NBu₄PF₆, 293 K) at <i>E</i>_1/2 = +0.57 V vs. Fc⁺/Fc assigned to a formal Pd­(III)/Pd­(II) couple. Multifrequency (Q-, X-, S-, and L-band) EPR spectroscopic analysis of [Pd([9]­aneS₃)₂]³⁺ and [Pd([18]­aneS₆)]³⁺ gives <i>g</i>_<i>iso</i> = 2.024, |<i>A</i>_{<i>iso</i>(Pd)}| = 18.9 × 10^–4 cm^–1; <i>g</i>_<i>xx</i> = 2.046, <i>g</i>_<i>yy</i> = 2.041, <i>g</i>_<i>zz</i> = 2.004; |<i>A</i>_{<i>xx</i>(Pd)}| = 24 × 10^–4 cm^–1, |<i>A</i>_{<i>yy</i>(Pd)}| = 22 × 10^–4 cm^–1, |<i>A</i>_{<i>zz</i>(Pd)}| = 14 × 10^–4 cm^–1, |<i>a</i>_<i>xx</i>(H)| = 4 × 10^–4 cm^–1, |<i>a</i>_<i>yy</i>(H)| = 5 × 10^–4 cm^–1, |<i>a</i>_<i>zz</i>(H)| = 5.5 × 10^–4 cm^–1 for [Pd([9]­aneS₃)₂]³⁺, and <i>g</i>_<i>iso</i> = 2.015, |<i>A</i>_{<i>iso</i>(Pd)}| = 18.8× 10^–4 cm^–1; <i>g</i>_<i>xx</i> = 2.048 <i>g</i>_<i>yy</i> = 2.036, <i>g</i>_<i>zz</i> = 1.998; |<i>a</i>_<i>xx(</i>H)| = 5, |<i>a</i>_<i>yy(</i>H)| = 5, |<i>a</i>_<i>zz(</i>H)| = 6 × 10^–4 cm^–1; |<i>A</i>_{<i>xx</i>(Pd)}| = 23× 10^–4 cm^–1, |<i>A</i>_{<i>yy</i>(Pd)}| = 22 × 10^–4 cm^–1, |<i>A</i>_{<i>zz</i>(Pd)}| = 4 × 10^–4 cm^–1 for [Pd([18]­aneS₆)]³⁺. Both [Pd([9]­aneS₃)₂]³⁺ and [Pd([18]­aneS₆)]³⁺ exhibit five-line superhyperfine splitting in the <i>g</i>_<i>zz</i> region in their frozen solution EPR spectra. Double resonance spectroscopic measurements, supported by density functional theory (DFT) calculations, permit assignment of this superhyperfine to through-bond coupling involving four ¹H centers of the macrocyclic ring. Analysis of the spin Hamiltonian parameters for the singly occupied molecular orbital (SOMO) in these complexes gives about 20.4% and 25% Pd character in [Pd([9]­aneS₃)₂]³⁺ and [Pd([18]­aneS₆)]³⁺, respectively, consistent with the compositions calculated from scalar relativistic DFT calculations