Novel linear transition metal clusters of a heptadentate bis-beta-diketone ligand.

The synthesis and the structure of the new potentially heptadentate ligand 1,3-bis-(3-oxo-3-(2-hydroxyphenyl)-propionyl)-2-methoxybenzene (H5L) is described. The reaction in pyridine or DMF of this ligand with various M(AcO)2 salts (M = NiII, CoII, MnII) leads to very different products depending on the metal. Thus, the dinuclear complexes [M2(H3L)2(py)4] (M = NiII, 1; CoII, 2) or the linear zigzag tetranuclear clusters [Mn4(H2L)2(AcO)2(py)5] (3) and [Mn4(H2L)2(AcO)2(dmf)4] (4) have been synthesized and characterized crystallographically. Slow oxidation of complex 3 leads to the formation of the novel mixed-valence linear complex [Mn3(HL)2(py)6] (5), displaying an unprecedented asymmetric MnIIIMnIIIMnII topology. The coordination geometry of complexes 1 to 5 has been analyzed and discussed by means of continuous shape measures. Magnetic measurements of 3 and 5 demonstrate that the metals within these complexes weakly interact magnetically with coupling constants of J1 = -1.13 cm-1 and J2 = -0.43 cm-1 (S = 0) for complex 3 and J1 = -5.4 cm-1 and J2 = -0.4 cm-1 (S = 5/2) for complex 5 (using the H = -Sigma2JijSiSj convention). These results are consistent with X-band EPR measurements on these compounds.

Nanosized polymetallic resorcinarene-based host assemblies that strongly bind fullerenes.

Polymetallic nanodimensional assemblies have been prepared via metal directed assembly of dithiocarbamate functionalized cavitand structural frameworks with late transition metals (Ni, Pd, Cu, Au, Zn, and Cd). The coordination geometry about the metal centers is shown to dictate the architecture adopted. X-ray crystallographic studies confirm that square planar coordination geometries result in "cagelike" octanuclear complexes, whereas square-based pyramidal metal geometries favor hexanuclear "molecular loop" structures. Both classes of complex are sterically and electronically complementary to the fullerenes (C(60) and C(70)). The strong binding of these guests occurred via favorable interactions with the sulfur atoms of multiple dithiocarbamate moieties of the hosts. In the case of the tetrameric copper(II) complexes, the lability of the copper(II)-dithiocarbamate bond enabled the fullerene guests to be encapsulated in the electron-rich cavity of the host, over time. The examination of the binding of fullerenes has been undertaken using spectroscopic and electrochemical methods, electrospray mass spectrometry, and molecular modeling.

(N-Benzyl-bis-N',N''-salicylidene)-cis-1,3,5-triaminocyclohexane copper(II): a novel catalyst for the aerobic oxidation of benzyl alcohol.

Reaction of Cu(BF(4))(2).6H(2)O with the N(3)O(2) donor ligand H(2)L (where H(2)L = N-benzyl-N',N''-di-tert-butyl-disalicyl-triaminocyclohexane) results in the formation of a novel Cu(II)L complex, 1. X-Ray crystallography of it shows the Cu(II) centre coordinated by two phenolate oxygens and two imine nitrogens in a distorted square plane with an elongated bond to the amine nitrogen (2.512 A) in the axial position. EPR spectroscopy gives g values of g(1) = 2.277, g(2) = 2.100, g(3) = 2.025, and A(1) = 15.6 mT which are consistent with the distorted square pyramidal coordination environment determined from the X-ray structure. UV/visible and electrochemical analysis of shows that it undergoes two reversible processes assigned to the successive oxidation of the phenolate oxygens to phenoxyl radicals, the first at E((1/2)) = 0.89 V (DeltaE = 81 mV, vs. Ag/AgCl) and the second at E((1/2)) = 1.13V (DeltaE = 84 mV, vs. Ag/AgCl). Chemical oxidation results in the formation of a species, assigned as [1](+)(.) which is EPR silent due to antiferromagnetic coupling between the Cu(II) centre and the bound phenoxyl radical. The oxidised species catalyses the oxidation of benzyl alcohol to benzaldehyde.

Mutual induced fit in cyclodextrin-rocuronium complexes.

The binding of rocuronium bromide to 6-perdeoxy-6-per(4-carboxyphenyl)thio-gamma-cyclodextrin sodium salt, displays biphasic behaviour characteristic of the formation of a binary and 2 : 1 ternary guest-host complex in aqueous solution. Thermodynamic and structural data on this sequential complexation process can be rationalised within a single model involving switching of the conformational equilibria of both the rocuronium bromide and cyclodextrin molecules. Isothermal titration calorimetry (ITC), NMR and fluorescence experiments in solution, together with X-ray crystallography and molecular modelling, suggest that in order to induce encapsulation both rocuronium bromide and the modified cyclodextrin undergo conformational changes. Ring A of rocuronium bromide 'switches' from the more sterically encumbered chair to the sterically less demanding twist-boat, whilst the modified cyclodextrin "opens" its cavity to allow the steroid to enter. The recognition and mutual induced fit between cyclodextrin and steroid represents a classic example of dynamic host-guest chemistry.

Macropolyhedral boron-containing cluster chemistry. Synchrotron X-ray structural analysis of [(PMe2Ph)2Pd2B16H20(PMe2Ph)2] and [(PMe2Ph)3Pt2B16H18(PMe2Ph)]: models of intermediates to more condensed metallaboranes from the [(PMe2Ph)2PtB8H12] thermolysis system.

Thermolyses of [(PMe2Ph)2PdB8H12] and [(PMe2Ph)2PtB8H12] respectively yield eighteen-vertex [(PMe2Ph)2Pd2B16H20(PMe2Ph)2] and [(PMe2Ph)3Pt2B16H18(PMe2Ph)], which exhibit structure models for probable successive precursive intermediates for the more condensed macropolyhedral metallaboranes [(PMe2Ph)4Pt3B14H16], [(PMe2Ph)2Pt2B12H16] and [(PMe2Ph)2Pt2B16H15(C6H4Me)(PMe2Ph)] that have previously been reported as products from [(PMe2Ph)2PdB8H12] thermolyses.

Supramolecular structures of 1-phenylethylammonium tartrates.

The structures of six 1-phenylethylammonium tartrates have been determined and in each of them a distinctive hydrogen-bonded anion substructure can be identified. (S)-1-Phenylethylammonium (R,R)-hydrogen tartrate [(I), P21, Z'=1] contains anion sheets built from a single type of R4(4)(22) ring with cations pendent, via three N-H...O hydrogen bonds, from just one face of the sheet. (S)-1-Phenylethylammonium rac-hydrogen tartrate [(II), P21, Z'=2] and its enantiomorph (R)-1-phenylethylammonium rac-hydrogen tartrate [(III), P21, Z'=2] contain anion sheets built from four types of ring, R2(2)(10), R2(2)(12), R2(4)(14) and R4(4)(20), and there are cations pendent from both faces of the sheet. The anion substructure in bis[(S)-1-phenylethylammonium] (R,R)-tartrate [(IV), P2(1), Z'=1] consists of simple C(5) chains, which are linked into sheets by the cations, while in bis(rac-1-phenylethylammonium) (R,R)-tartrate [(V), P2(1), Z'=2] there are anion sheets containing two distinct types of R4(4)(22) ring, with equal numbers of (R) and (S) cations pendent from each face of the anion sheet. Bis[(R)-1-phenylethylammonium] rac-tartrate methanol hemisolvate [(VI), P1, Z'=4, with 14 independent components in the asymmetric unit] contains anion sheets built from two types of R2(2)(12) ring and two types of R6(6)(32) ring; half of the cations and half of the methanol molecules are pendent from each face of the sheet.

Ammonium cyanate shows N-H...N hydrogen bonding, not N-H...O.

The transformation of ammonium cyanate into urea, first studied over 170 years ago by Wöhler and Liebig, has an important place in the history of chemistry. To understand the nature of this solid state reaction, knowledge of the crystal structure of ammonium cyanate is a prerequisite. Employing neutron powder diffraction, we demonstrate conclusively that, in the structure of ammonium cyanate, the NH(4)(+) cation forms N-H...N hydrogen bonds to four cyanate N atoms at alternate corners of a distorted cube, rather than our previously proposed alternative arrangement with N-H...O hydrogen bonds to cyanate O atoms at the other four corners.

Structural study of the thermal and photochemical spin states in the spin crossover complex [Fe(phen)2(NCSe)2].

The first structural data for [Fe(phen)(2)(NCSe)(2)] (obtained using the extraction method of sample preparation) in its high-spin, low-spin and LIESST induced metastable high-spin states have been recorded using synchrotron radiation single crystal diffraction. The space group for all of the spin states was found to be Pbcn. On cooling from the high-spin state (HS-1) at 292 K through the spin crossover at about 235 K to the low-spin state at 100 K (LS-1) the iron coordination environment changed to a more regular octahedral geometry and the Fe-N bond lengths decreased by 0.216 and 0.196 A (Fe-N(phen)) and 0.147 A (Fe-N(CSe)). When the low-spin state was illuminated with visible light at about 26 K, the structure of this LIESST induced metastable high-spin state (HS-2) was very similar to that of HS-1 with regards to the Fe-phen bond lengths, but there were some differences in the bond lengths in the Fe-NCSe unit between HS-1 and HS-2. When HS-2 was warmed in the dark to 50 K, the resultant low-spin state (LS-2) had an essentially identical structure to LS-1. In all spin states, all of the shortest intermolecular contacts (in terms of van der Waals radii) involved the NCSe ligand, which may be important in describing the cooperativity in the solid state. The quality of the samples was confirmed by magnetic susceptibility and IR measurements.

The salt-type 1:2 adduct of meso-5,5,7,12,12,14-hexa-C-methyl-1,4,8,11-tetraazacyclotetradecane (tet-a) and 5-nitroisophthalic acid forms a hydrogen-bonded sheet structure containing two configurational isomers of [(tet-a)H2]2+.

The title compound, meso-5,7,7,12,14,14-hexamethyl-4,11-diaza-1,8-diazoniacyclotetradecane bis(3-carboxy-5-nitrobenzoate), C(16)H(38)N(4)(2+).2C(8)H(4)NO(6)(-), is a salt in which the cation is present as two configurational isomers, disordered across a common centre of inversion in P1, with occupancies of 0.847 (3) and 0.153 (3). The anions are linked into chains by a single O-H...O hydrogen bond [H...O 1.71 A, O...O 2.5063 (15) A and O-H...O 156 degrees ] and the cations link these anion chains into sheets by means of a range of N-H...O hydrogen bonds [H...O 1.81-2.53 A, N...O 2.718 (5)-3.3554 (19) A and N-H...O 146-171 degrees ].

Labile coodination dendrimers.

Addition of anionic benzylsulfate dendrons to dynamic mixtures of Ag+ and triphosphine ligands results in the assembly of loosely-bonded cage-core dendrimers.

4-(allylamino)-2-amino-6-benzyloxy-5-nitrosopyrimidine from synchrotron data at 150 K: double chains built from N[bond]H...N, N[bond]H...O, N[bond]H...pi(arene) and aromatic pi-pi-stacking interactions.

In the title compound, C(14)H(15)N(5)O(2), the intramolecular dimensions are consistent with a highly polarized electronic structure. The molecules are linked into chains by a combination of N[bond]H...N, N[bond]H...O and N[bond]H...pi(arene) hydrogen bonds, and the chains are linked in pairs by aromatic pi-pi-stacking interactions

Effect of Included Solvent Molecules on the Physical Properties of the Paramagnetic Charge Transfer Salts beta' '-(bedt-ttf)(4)[(H(3)O)Fe(C(2)O(4))(3)].Solvent (bedt-ttf = Bis(ethylenedithio)tetrathiafulvalene).

The new charge transfer salt, beta' '-(bedt-ttf)(4)[(H(3)O)Fe(C(2)O(4))(3)].C(5)H(5)N, I, (bedt-ttf = bis(ethylenedithio)tetrathiafulvalene) has a crystal structure closely similar to that of the reported salt beta' '-(bedt-ttf)(4)[(H(3)O)Fe(C(2)O(4))(3)].C(6)H(5)CN, II, which has a superconducting critical temperature of 8.6 K. However, variable temperature magnetic and transport experiments show that I has a metal to insulator transition at 116 K. The crystal structure of I has been determined above (150 K) and below (90 K) the metal to insulator transition and comparisons are made with the structure of II. The pyridine solvate crystallizes in the monoclinic space group C2/c with a = 10.267(2) Å, b = 19.845(4) Å, c = 34.907(7) Å, beta = 93.22(3) degrees, Z = 4 at 150 K and with a = 10.2557(15) Å, b = 19.818(28) Å, c = 34.801(49) Å, beta = 93.273(14) degrees, Z = 4 at 90 K. The structures of I and II both consist of layers of bedt-ttf with +0.5 formal charge per molecule and layers of approximately hexagonal symmetry containing H(3)O(+) and [Fe(C(2)O(4))(3)](3)(-). The solvent molecules occupy hexagonal cavities formed by the anionic layer. Changing the solvent molecule from C(6)H(5)CN to C(5)H(5)N induces disorder in the bedt-ttf layer which accounts for the dramatic difference in observed physical properties. For I, at 150 K, one-half of all the bedt-ttf molecules have identical conformations to all the molecules in II where both terminal ethylene groups of each bedt-ttf molecule are twisted and eclipsed with respect to the opposite end of the molecule. The remaining 50% of bedt-ttf molecules in I have disordered ethylene groups. The disorder persists at 90 K where it can be resolved into two conformations: twisted-twisted eclipsed and twisted-twisted staggered.