Neue Koordinationsverbindungen aus Triorganylzinn(IV)-dimesylamiden und Neutralliganden: Einkern- und Mehrkernkomplexe mit molekularer oder ionischer Kristallstruktur

Polysulfonylamines. CII. New Coordination Compounds Derived from Triorganyltin(IV) Dimesylamides and Uncharged Ligands: Mononuclear and Polynuclear Complexes with Molecular or Ionic Crystal Structures The purpose of this report is to draw attention to the remarkable versatility of the dimesylamides R₃SnA [A^– = (MeSO₂)₂N^–; R = Me ( 1 a ) or Ph ( 1 b )] as precursors for pentacoordinate triorganyltin(IV) complexes belonging to four distinct structural types. Representative complexes were prepared by treating 1 a or 1 b in the appropriate molar ratios with unidentate thiourea or urea-type ligands or with the bidentate ligand [Ph₂P(O)CH₂]₂ (DPPOE). The following compounds were characterized by X-ray analysis: [Me₃Sn(A)(thiourea)] ( 2 a ; monoclinic, space group P2₁/n), [Ph₃Sn(A)(tetramethylthiourea)] ( 2 b ; monoclinic, P2₁, two independent formula units), [Me₃Sn(1-methylurea)₂]⁺ · A^– ( 3 a ; monoclinic, P2₁/c), [Ph₃Sn(1,1-dimethylurea)₂]⁺ · A^– ( 3 c ; triclinic, P1), [{Ph₃Sn(A)}₂(μ-dppoe)] ( 4 ; triclinic, P1), [Ph₃Sn(μ-dppoe)]_nⁿ⁺ · n A^– · n MeCN ( 5 ; monoclinic, P2₁/c). The lattices of 2 a , 2 b and 4 contain discrete uncharged formula units which are mononuclear for 2 a and 2 b or dinuclear for 4 , whereas 3 a , 3 c and 5 have ionic structures featuring mononuclear cations for 3 a and 3 c or an infinite linear-polymeric cation for 5 . In all the structures, the tin atoms adopt trigonal-bipyramidal geometries, the apical positions being occupied in 2 a and 2 b by the S atom of the thiourea and one O atom of A^–, in 3 a and 3 c by the O atoms of two urea-type ligands, in 4 by an O atom of the bridging DPPOE molecule and one O atom of A^–, and in 5 by two phosphoryl O atoms from different bridging DPPOE ligands. In the structures of 2 a , 3 a and 3 c , the (thio)urea NH functions are connected to A^– via intermolecular or interionic N–H … O and N–H … N hydrogen bonds. Crystals of [{Me₃Sn(bipyH⁺ … A^–)}₂(μ-bipy)]²⁺ · 2 A^– ( 6 ; monoclinic, C2/c) formed adventitiously in a reaction mixture containing 1 a and 4,4′-bipyridine. The rod-like supramolecular cation of 6 (length ca. 4 nm) is built up from two Me₃Sn⁺ units bridged through bipy and unidentally coordinated by a monoprotonated bipy (= bipyH⁺), resulting in a trigonal-bipyramidal geometry around tin (N atoms apical); each of the terminal bipyH⁺ ligands forms an ⁺N–H … N^– hydrogen bond with one A^–.     

Selectivity of 1-O-Propargyl-d-Mannose Preparations

Thanks to their ability to bind to specific biological receptors, mannosylated structures are examined in biomedical applications. One of the most common ways of linking a functional moiety to a structure is to use an azide-alkyne click reaction. Therefore, it is necessary to prepare and isolate a propargylated mannose derivative of high purity to maintain its bioactivity. Three known preparations of propargyl-α-mannopyranoside were revisited, and products were analysed by NMR spectroscopy. The preparations were shown to yield by-products that have not been described in the literature yet. Our experiments showed that one-step procedures could not provide pure propargyl-α-mannopyranoside, while a three-step procedure yielded the desired compound of high purity.     

Flavonoid and phenolic acid profile by LC-MS/MS and biological activity of crude extracts from Chenopodium hybridum aerial parts

Extracts from leaves and stems of Chenopodium hybridum were characterised for the presence and quantity of flavonoids and phenolic acids by LC-ESI-MS/MS. Five flavonoids and eight phenolic acids were detected for the first time in aerial parts of this plant species, the most abundant compounds being rutin (2.80 μg/g DW), 3-kaempferol rutinoside (2.91 μg/g DW), 4-OH-benzoic (1.86 μg/g DW) and syringic acids (2.31 μg/g DW). Extracts were tested for anti-inflammatory/antiarthritic, antihyaluronidase and cytotoxic activities against human prostate cancer (Du145, PC3) and melanoma cell lines (A375, HTB140 and WM793) of different malignancy. None of the extracts protected bovine serum albumin from heat-induced denaturation. Antihyaluronidase effect at the tested concentration was higher than standard naringenin. Cytotoxic activity was generally low with an exception of the extract from the leaves, which was found most effective against prostate Du145 cell line with 98.28 ± 1.13% of dead cells at 100 μg/mL.     

Iron-Mediated Amination of Hydrocarbons in the Gas Phase

FeNH⁺ is chosen as a model system to probe the transition-metal-mediated transfer of imine groups in the gas phase by mass-spectrometric means. Ab initio calculations at the MR-ACPF level predict FeNH⁺ to have a linear sextet ground state (⁶Σ⁺); a bent quartet state (⁴A′) and a linear doublet state (²Δ) are higher in energy by 0.14 eV and 0.51 eV, respectively. The bond-dissociation energy is determined to D(Fe⁺−NH)=69±2 kcal mol⁻¹ using ion-molecule reactions. Charge-stripping experiments combined with ab initio calculations yield an ionization energy of IE(FeNH⁺)=15.7±0.5 eV. The chemical behavior of FeNH⁺ towards oxygen, water, hydrogen, aliphatic hydrocarbons, benzene, and toluene reveals an intrinsically high reactivity of FeNH⁺. Because a transfer of the 〈NH〉 fragment to the substrate is feasible in most cases, attractive amination reactions like methane→methylamine, benzene→aniline, or toluene→benzylidenamine can be afforded by FeNH⁺.     

Catalytic Preparation of Non-Symmetrical Ketones in the Gas Phase Over Iron Oxide

The catalytic conversion of esters and mixtures of alcohols and aldehydes in the gas phase over iron oxide has been studied. The method allows for effective synthesis of non-symmetrical ketones.     

The preparation und unusual rearrangement of triply bridged μ-heteromethylenecobalt complexes. Molecular structure of μ-ethoxycarbonylmethylenebis[carbonyl-(η5-cyclopentadienyl)cobalt] (CoCo)

the μ-heteromethylenecobalt complexes, which have been synthesized by photolysis of (η⁵-C₅H₅)Co(CO)₂ in the presence of the corresponding diazoacetates at < ?90°C in tetrahydrofuran, undergo a novel type of intramolecular irreversible rearrangement yielding two isomers. The structure of one of the isomers has been established by X-ray analysis. A comparison of the structural parameters of all known μ-methylene-transition metal complexes shows that the internal angles α of the cyclopropane-like systems are far less sensitive to the compositions and structures of the molecules than the external angles β. The internal angles cannot be readily correlated with other features of the molecule.     

Water as a proton donor in excited state reactions of 6, 6′-biquinoline

6, 6′-biquinoline (BQ) in aqueous-alcoholic solutions exhibits doubleluminescence and two ESR signals in the triplet state. The structureless fluorescence band observed at room temperature was shown to be the result of the protonation of strongly basic¹ (BQ)^* (pK^* = 13). At low temperature the aggregation of the molecule has been observed. The low temperature absorption, luminescence, luminescence excitation spectra, and triplet ESR spectra of the aggregates have been measured and distinguished from the corresponding spectra of monomeric BQ.     

Charge density flow as a driving force of distortion in excited protonated azaaromatics

The INDO method was used to calculate electronic charge densities in the ground and lowest excited singlet and triplet states of neutral and protonated 2,3- and 1,4-diaza derivatives of naphthalene and phenanthrene, and benzo (a) phenazine. Experiniental changes of pK_a upon excitation can be correlated with the values of electron density flow into the heterocy- clic ring. Electron-density increase turns out to be a major factor which causes distortion in some excited protonated species.     

EXCITED STATES OF SIX-MEMBERED N-HETEROCYCLES. FLUORESCENCE, PHOSPHORESCENCE AND ACID-BASE EQUILIBRIA OF FIVE MONO- AND DIAZA-PHENANTHRENES IN THE LOWEST EXCITED (τ,τ) STATES

Abstract— Acid-base equilibria of five azaphenanthrenes (1-and 4-aza; 1,10-, 1,7-, and 4,7-diaza) in the two lowest excited (τ,τ) states have been determined by Förster's cycle. Pure electronic levels of the free bases and their conjugate acids have been located from the absorption, fluorescence and phosphorescence spectra. In diazaphenanthrenes the increase of the first pK_a and the decrease of the second pK_a under excitation has been observed, and an explanation is offered. In many cases the reactivity of the molecule excited to the lowest triplet state differs considerably from that in the ground state. The Pariser-Pam-Pople (PPP) calculations of the free bases have been performed. From the theoretical results, the changes of the net charge on nitrogen atoms under excitation and the magnitude of the S-T splitting in the L_a and L_b states have been discussed and compared with experiment.