Tobias Rüffer

Hydrolysis of a basic bismuth nitrate--formation and stability of novel bismuth oxido clusters.

The synthesis of the nanoscaled bismuth oxido clusters [Bi(38)O(45)(NO(3))(20)(DMSO)(28)](NO(3))(4)·4DMSO (1a) and [Bi(38)O(45)(OH)(2)(pTsO)(8)(NO(3))(12)(DMSO)(24)](NO(3))(2)·4DMSO·2H(2)O (2) starting from the basic bismuth nitrate [Bi(6)O(4)(OH)(4)](NO(3))(6)·H(2)O is reported herein. Single-crystal X-ray diffraction analysis, ESI mass spectrometry, thermogravimetric analysis, and molecular dynamics simulation were used to study the formation, structure, and stability of these large metal oxido clusters. Compounds 1a and 2 are based on a [Bi(38)O(45)](24+) core, which is structurally related to δ-Bi(2)O(3). Examination of the fragmentation pathways of 1a and 2 by infrared multi-photon dissociation (IRMPD) tandem MS experiments allows the identification of novel bismuth oxido cluster species in the gas phase.

From {Bi22O26} to chiral ligand-protected {Bi38O45}-based bismuth oxido clusters.

The reaction of [Bi(22)O(26)(OSiMe(2)tBu)(14)] (1) in THF with salicylic acid gave [Bi(22)O(24)(HSal)(14)] (2) first, which was converted into [Bi(38)O(45)(HSal)(22)(OH)(2)(DMSO)(16.5)]·DMSO·H(2)O (3·DMSO·H(2)O) after dissolution and crystallization from DMSO. Single-crystal X-ray diffraction analysis and ESI mass spectrometry associated with infrared multi-photon dissociation (IRMPD) tandem MS experiments confirm the formation of the large and quite stable bismuth oxido cluster 3. The reaction of compound 2 with the butoxycarbonyl(BOC)-protected amino acids phenylalanine and valine (BOC-PheOH and BOC-ValOH), respectively, resulted in the formation of chiral [Bi(38)O(45)(BOC-AA)(22)(OH)(2)] (AA=deprotonated amino acid), as shown by a combination of different analytical techniques such as elemental analysis, dynamic light scattering, circular dichroism spectroscopy, and ESI mass spectrometry.

Synthesis and crystal structure of a dinuclear zinc(II)-dithiocarbamate complex, bis {[(μ 2-pyrrolidinedithiocarbamato-S,S′)(pyrrolidinedithiocarbamato-S,S′)zinc(II)]}

A new zinc(II) complex of pyrrolidinedithiocarbamate (PDTC), bis[(μ 2-pyrrolidinedithiocarbamato-S,S′)(pyrrolidinedithiocarbamato-S,S′)zinc(II)], [Zn2(PDTC)4] (1) has been prepared by reaction of ZnCl2 with ammonium pyrrolidinedithiocarbamate in 1 : 1 and 1 : 2 ratio, respectively. The complex has been characterized by IR, NMR and X-ray crystallography. Compound 1 crystallizes in the triclinic space group P 1 in the form of a centrosymmetric dimer. The solid-state structure contains two crystallographically equivalent Zn+2 centers in a tetrahedrally distorted ion sphere. A mixed-ligand complex, [Zn(PDTC)(MSC)]− (MSC = mercaptosuccinate) was also prepared but the structure of the resulting complex was found to be the same as 1, suggesting that the thiolate ligand was replaced on addition of PDTC.

Hydrolysis studies on bismuth nitrate: synthesis and crystallization of four novel polynuclear basic bismuth nitrates.

Hydrolysis of Bi(NO(3))(3) in aqueous solution gave crystals of the novel compounds [Bi(6)O(4)(OH)(4)(NO(3))(5)(H(2)O)](NO(3)) (1) and [Bi(6)O(4)(OH)(4)(NO(3))(6)(H(2)O)(2)]·H(2)O (2) among the series of hexanuclear bismuth oxido nitrates. Compounds 1 and 2 both crystallize in the monoclinic space group P2(1)/n but show significant differences in their lattice parameters: 1, a = 9.2516(6) Å, b = 13.4298(9) Å, c = 17.8471(14) Å, β = 94.531(6)°, V = 2210.5(3) Å(3); 2, a = 9.0149(3) Å, b = 16.9298(4) Å, c = 15.6864(4) Å, β = 90.129(3)°, V = 2394.06(12) Å(3). Variation of the conditions for partial hydrolysis of Bi(NO(3))(3) gave bismuth oxido nitrates of even higher nuclearity, [{Bi(38)O(45)(NO(3))(24)(DMSO)(26)}·4DMSO][{Bi(38)O(45)(NO(3))(24)(DMSO)(24)}·4DMSO] (3) and [{Bi(38)O(45)(NO(3))(24)(DMSO)(26)}·2DMSO][{Bi(38)O(45)(NO(3))(24)(DMSO)(24)}·0.5DMSO] (5), upon crystallization from DMSO. Bismuth oxido clusters 3 and 5 crystallize in the triclinic space group P1 both with two crystallographically independent molecules in the asymmetric unit. The following lattice parameters are observed: 3, a = 20.3804(10) Å, b = 20.3871(9) Å, c = 34.9715(15) Å, α = 76.657(4)°, β = 73.479(4)°, γ = 60.228(5)°, V = 12021.7(9) Å(3); 5, a = 20.0329(4) Å, b = 20.0601(4) Å, c = 34.3532(6) Å, α = 90.196(1)°, β = 91.344(2)°, γ = 119.370(2)°, V = 12025.8(4) Å(3). Differences in the number of DMSO molecules (coordinated and noncoordinated) and ligand (nitrate, DMSO) coordination modes are observed.

Extremely Simple but Long Overlooked: Generation of α-Azido Alcohols by Hydroazidation of Aldehydes†

of 1 with hydrazoic acid to prepare a-azido alcohols 2 is completely unknown. Attempts to generate 2 by methanolysis of silyl ethers 3 led only to 1. a-Azido alcohols of type 2 have been discussed as short-lived intermediates in the solvolysis of diazides 4, which also yielded the final products 1. Protonation of 2 at N-a leads to an intermediate that is generally accepted to explain the mechanism of the Schmidt reaction. Recently, in situ formation of azidomethanol (2a) was postulated in the reaction of formaldehyde and sodium azide in the presence of acetic acid. This reaction was completed by copper(I)-catalyzed cycloaddition at terminal alkynes to give 1,2,3-triazoles. In all of these cases, there is no spectroscopic proof of intermediates 2, whereas compounds of types 3 6] and 4 and also a-azido ethers 5 9] can be prepared easily from precursors 1 or the corresponding acetals or enol ethers and then isolated and characterized. This led to the presumption that hydrazoic acid does not react with aldehydes readily. Since we did not question this statement or at least did not doubt the elusiveness of a-azido alcohols 2, we obtained evidence for these compounds incidentally. By treatment of triazide 7 with anhydrous hydrogen halide, we prepared azidochloromethane (8) and azidobromomethane (9) besides diazide 10 (Scheme 2). The desired products are inter-

Solvatochromism and linear solvation energy relationship of diol- and proline-functionalized azo dyes using the Kamlet–Taft and Catalán solvent parameter sets

New donor–acceptor-substituted azo dyes, such as 2-({4-[(E)-(2,4-dinitrophenyl)diazenyl]-2-nitrophenyl}amino)propane-1,3-diol, (2S)-1-{4-[(E)-(2,4-dinitrophenyl)diazenyl]-2-nitrophenyl}-pyrrolidine-2-carboxylic acid and methyl-(2S)-1-{4-[(E)-(2,4-dinitrophenyl)diazenyl]-2-nitrophenyl}pyrrolidine-2-carboxylate have been obtained in a single step by nucleophilic aromatic substitution of (E)-1-(2,4-dinitrophenyl)-2-(4-fluoro-3-nitrophenyl)diazene with 2-aminopropane-1,3-diol, (S)-proline and (S)-proline methyl ester hydrochloride. The solvatochromism of the diol- and (S)-proline-methyl-ester-containing azo dye was studied and analysed using the empirical Kamlet–Taft and Catalan solvent parameter set. The dyes undergo a reversible protonation–deprotonation equilibrium in a concentration range of 5–12 M hydrochloric acid. The UV/Vis absorption spectra show a bathochromic shift with increasing acid strength of the medium.

SYNTHESIS AND CHARACTERIZATION OF SUBSTITUTED (AMINOMETHYL)LITHIUM COMPOUNDS. THE STRUCTURES OF LI2(CH2NPH2)2(THF)3 AND LI4(CH2NC5H10)4(THF)2

Abstract (Aminomethyl)lithium compounds LiCH2NRR′ · x THF (NRR′ = NMe2 (1a, x = 0), NPhMe (1b, x = 2), NPh2 (1c, x = 1 … 1,5), NC5H10 (1d, x = 0, NC5H10 = piperidino), and NC7H14 (1e, NC7H14 = 2,6-dimethylpiperidino)) were prepared by the reaction of Bu3SnCH2NRR′ with BuLi. 1a–d were isolated in solid state and characterized by NMR spectroscopy (1H, 13C, 7Li). 1e was obtained in solution and characterized via reaction with MeOH and with benzophenone to generate MeNC7H14 and Ph2C(OH)CH2NC7H14, respectively. Recrystallization of 1c and 1d from n-hexane/THF gives [Li2(CH2NPh2)2(THF)3] (1c′) and [Li4(CH2NC5H10)4(THF)2] (1d′), respectively, whose structures (X-ray) were determined. The dimeric compound 1c′ forms a central planar four-membered Li2C2 ring. One lithium atom is four-coordinated to two methylene carbon atoms (d(Li-C) = 2.246(9), 2.235(9) A) and two oxygen atoms of THF. Unusually, the second lithium exhibits a nearly planar coordination sphere represented by two methylene carbon atoms (d(Li-C) = 2.17(1) and 2.16(1) A) and by the oxygen atom of the disordered THF molecule. 1d′ is a tetrameric species exhibiting a molecular C2 symmetry. The lithium atoms are arranged in a distorted tetrahedron with methylene carbon atoms occupying each face of the tetrahedron.

Probing the surface polarity of inorganic oxides using merocyanine-type dyes derived from barbituric acid

The solid state complexes, solvatochromic and acidochromic behaviour of four merocyanine-type dyes derived from barbituric and thiobarbituric acid and their use as solvatochromic probe molecules for coloured surfaces are described. The dyes were obtained by condensation reaction of barbituric, N-methylbarbituric, N,N′-dimethylbarbituric and thiobarbituric acid with 4-N,N-dimethylaminocinnamaldehyde. The dyes were characterised by means of liquid and solid state NMR techniques (1H MAS NMR, 1H–1H DQ MAS NMR, 13C CPMAS NMR), single-crystal X-ray analysis, UV/vis and IR measurements. The solvatochromism has been investigated in 43 solvents and interpreted in terms of Kamlet–Taft parameters α, β, and π*. Altogether, the solvatochromic properties of these four dyes were determined mainly by the hydrogen bond donating (HBD) ability and the polarisability/dipolarity of a solvent. The interactions of the dyes with oxidic and metal surfaces were studied. Their perichromic behaviour was compared with that of established solvatochromic dyes for the determination of α, β, and π*, namely dicyano-bis-(1,10-phenanthroline)-iron(II)-complex (1), 3-(4-amino-3-methylphenyl)-7-phenyl-benzo-[1,2-b:4,5-b′]-difuran-2,6-dione (2) and 4-tert-butyl-2-(dicyanomethylene)-5-[4-(diethylamino)benzylidene]-Δ3-thiazoline (3). The barbituric acid dyes were used to probe the surface polarity of coloured oxides like tungsten(VI) oxide and iron(III) oxide. The interactions between the dyes and metals like zinc and aluminium were also investigated.

Interplay of hydrogen bonding and molecule–substrate interaction in self-assembled adlayer structures of a hydroxyphenyl-substituted porphyrin

Abstract The formation of hydrogen-bonded organic nano-structures and the role of the substrate lattice thereby were investigated by scanning tunneling microscopy. The self-organization of 5,10,15,20-tetra(p-hydroxyphenyl)porphyrin (H2THPP) molecules leads to two molecular arrangements on Au(111). One of these is characterized by pair-wise hydrogen bonding between hydroxyl groups and a low packing density which enables a rotation of individual molecules in the structure. A different interaction with stronger chain-like hydrogen bonding and additional interactions of phenyl groups was observed for the second structure. The influence of the substrate on the epitaxial behavior is demonstrated by the adsorption of H2THPP on the highly anisotropic Ag(110) substrate. There, several balances between the occupation of favorable adsorption positions and the number of hydrogen bonds per molecule were found. The molecules form molecular chains on Ag(110) and also assemble into two-dimensional periodic arrangements of differently sized close-packed blocks similar to the second type of supramolecular ordering found on Au(111). Dispersion corrected Density Functional Theory calculations were applied to understand the adsorption and complex epitaxy of these molecules. It is shown that the azimuthal orientation of the saddle-shape deformed molecule plays an important role not only for the intermolecular but also for the molecule–substrate interaction.

Two novel nanoscaled bismuth oxido clusters, [Bi38O45(OMc)22(C8H7SO3)2(DMSO)6(H2O)1.5]·2.5H2O and [Bi38O45(HSal)22(OMc)2(DMSO)15(H2O)]·DMSO·2H2O

Abstract The synthesis of [Bi38O45(OMc)22(C8H7SO3)2(DMSO)6(H2O)1.5]·2.5H2O (1·2.5H2O) (OMc—methacrylate) and [Bi38O45(HSal)22(OMc)2(DMSO)15(H2O)]·DMSO·2H2O(2·DMSO·2H2O) (Hsal—salicylate) starting from [Bi38O45(OMc)24(DMSO)9]·2DMSO·7H2O and sodium 4-vinylbenzenesulfonate and salicylic acid, respectively, is presented. The bismuth oxido clusters show diameters of 2.9 nm (1) and 2.4 nm (2) and molecular weights of 11,440.22 g/mol (1·2.5H2O) and 13,151.92 g/mol (2·DMSO·2H2O). The polynuclear framework of 1 and 2 is quite similar; nevertheless, a comparison of the bismuth and oxygen atom positions of 1 and 2 shows a weighted root mean square deviation of 0.307 and 0.413 Å, respectively, as a result of the different coordination sphere. Both [Bi38O45]24+ cores in 1 and 2 are coordinated by two different anionic ligands with a ligand-to-ligand ratio of 22:2, which might indicate two particularly reactive positions at each bismuth oxido cluster.