Synthesis of functional aromatic multisulfonyl chlorides and their masked precursors

The synthesis of functional aromatic bis(sulfonyl chlorides) containing an acetophenone and two sulfonyl chloride groups, i.e., 3,5-bis[4-(chlorosulfonyl)phenyl]-1-acetophenone (16), 3,5-bis(chlorosulfonyl)-1-acetophenone (17), and 3,5-bis(4-(chlorosulfonyl)phenyloxy)-1-acetophenone (18) via a sequence of reactions, involving in the last step the quantitative oxidative chlorination of S-(aryl)- N,N'-diethylthiocarbamate, alkyl- or benzyl thiophenyl groups as masked nonreactive precursors to sulfonyl chlorides is described. A related sequence of reactions was used for the synthesis of the aromatic trisulfonyl chloride 1,1,1-tris(4-chlorosulfonylphenyl)ethane (24). 4-(Chlorosulfonyl)phenoxyacetic acid, 2,2-bis[[[4-(chlorosulfonyl)phenoxyacetyl]oxy]methyl]-1,3-propanediyl ester (27), 5,11,17,23-tetrakis(chlorosulfonyl)-25,26,27,28-tetrakis(ethoxycarbonylmethoxy)calix[4]arene (38), 5,11,17,23,29,35-hexakis(chlorosulfonyl)-37,38,39,40,41,42-hexakis(ethoxycarbonylmethoxy)calix[6]arene (39), 5,11,17,23,29,35,41,47-octakis(chlorosulfonyl)-49,50,51,52,53,54,55,56-octakis(ethoxycarbonylmethoxy)calix[8]arene (40), 5,11,17,23-tetrakis(tert-butyl)-25,26,27,28-tetrakis(chlorosulfonyl phenoxyacetoxy)calix[4]arene (44), 5,11,17,23,29,35-hexakis(tert-butyl)-37,38,39,40,41,42-hexakis(chlorosulfonylphenoxyacetoxy)calix[6]arene (45), and 5,11,17,23,29,35,41,47-octakis(tert-butyl)-49,40,51,52,53,54,55,56-octakis(chlorosulfonylphenoxyacetoxy)calix[8]arene (46) were synthesized by two different multistep reaction procedures, the last step of both methods consisting of the chlorosulfonation of compounds containing suitable activated aromatic positions. 2,4,6-Tris(chlorosulfonyl)aniline (47) was obtained by the chlorosulfonation of aniline. The conformation of two series of multisulfonyl chlorides i.e., 38, 39, 40 and 44, 45, 46, was investigated by (1)H NMR spectroscopy. The masked nonreactive precursor states of the functional aromatic multisulfonyl chlorides and the aromatic multisulfonyl chlorides reported here represent the main starting building blocks required in a new synthetic strategy elaborated for the preparation of dendritic and other complex organic molecules.     

Homoleptic Two‐Coordinate Silylamido Complexes of Chromium(I), Manganese(I), and Cobalt(I)

Anionic two‐coordinate complexes of first‐row transition‐metal(I) centres are rare molecules that are expected to reveal new magnetic properties and reactivity. Recently, we demonstrated that a N(SiMe₃)₂^? ligand set, which is unable to prevent dimerisation or extraneous ligand coordination at the +2 oxidation state of iron, was nonetheless able to stabilise anionic two‐coordinate Fe^I complexes even in the presence of a Lewis base. We now report analogous Cr^I and Co^I complexes with exclusively this amido ligand and the isolation of a [Mn^I{N(SiMe₃)₂}₂]₂^2? dimer that features a Mn?Mn bond. Additionally, by increasing the steric hindrance of the ligand set, the two‐coordinate complex [Mn^I{N(Dipp)(SiMe₃)}₂]^? was isolated (Dipp=2,6‐iPr₂‐C₆H₃). Characterisation of these compounds by using X‐ray crystallography, NMR spectroscopy, and magnetic susceptibility measurements is provided along with ligand‐field analysis based on CASSCF/NEVPT2 ab initio calculations.     

Combining Neopentyllithium with Potassium tert‐Butoxide: Formation of an Alkane‐Soluble Lochmann–Schlosser Superbase

Mixtures of alkyllithium and heavier alkali‐metal alkoxides are often used to form alkyl compounds of heavier alkali metals, but these mixtures are also known for their high reactivity in deprotonative metalation reactions. These organometallic mixtures are often called LiC–KOR superbases, but despite many efforts their constitution remains unknown. Herein we present mixed alkali‐metal alkyl/alkoxy compounds produced by reaction of neopentyllithium with potassium tert‐butoxide. The key to success was the good solubility and temperature‐stability of neopentyl alkali‐metal compounds, leading to hexane‐soluble mixtures, which allowed handling at ambient temperatures and isolation by crystallization. The compounds in solid state and in solution were identified by X‐ray crystallography and NMR spectroscopy as mixtures of lithium/potassium neopentyl/tert‐butoxy aggregates of varying compositions Li_xK_yNp_z(OtBu)_x+y?z.     

Reich-type iterated function systems

In this paper, we introduce the concept of Reich-type iterated function system and prove the existence and uniqueness of the attractor of such a system. Moreover, we study the properties of the canonical projection from the code space onto the attractor of such a system. We also present an iterated function system consisting of continuous Reich contractions having more than one attractor.     

Trinuclear {M1}CN{M2}2 complexes (M1 = Cr(III), Fe(III), Co(III); M2 = Cu(II), Ni(II), Mn(II)). Are single molecule magnets predictable?

The reaction of the hexacyanometalates K3[M(1)(CN)6] (M(1) = Cr(III), Fe(III), Co(III)) with the bispidine complexes [M(2)(L(1))(X)](n+) and [M(2)(L(2))(X)](n+) (M(2) = Mn(II), Ni(II), Cu(II); L(1) = 3-methyl-9-oxo-2,4-di-(2-pyridyl)-7-(2-pyridylmethyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylic acid dimethyl ester; L(2) = 3-methyl-9-oxo-7-(2-pyridylmethyl)-2,4-di-(2-quinolyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylic acid dimethyl ester; X = anion or solvent) in water-methanol mixtures affords trinuclear complexes with cis- or trans-arrangement of the bispidine-capped divalent metal centers around the hexacyanometalate. X-ray structural analyses of five members of this family of complexes (cis-Fe[CuL(2)]2, trans-Fe[CuL(1)]2, cis-Co[CuL(2)]2, trans-Cr[MnL(1)]2, trans-Fe[MnL(1)]2) and the magnetic data of the entire series are reported. The magnetic data of the cyanide bridged, ferromagnetically coupled cis- and trans-Fe[ML]2 compounds (M = Ni(II), Cu(II)) with S = 3/2 (Cu(II)) and S = 5/2 (Ni(II)) ground states are analyzed with an extended Heisenberg Hamiltonian which accounts for anisotropy and zero-field splitting, and the data of the Cu(II) systems, for which structures are available, are thoroughly analyzed in terms of an orbital-dependent Heisenberg Hamiltonian, in which both spin-orbit coupling and low-symmetry ligand fields are taken into account. It is shown that the absence of single-molecule magnetic behavior in all spin clusters reported here is due to a large angular distortion of the [Fe(CN)6](3-) center and the concomitant quenching of orbital angular momentum of the Fe(III) ((2)T2g) ground state.     

Microscopic Features of Bosonic Quantum Transport and Entropy Production

The microscopic features of bosonic quantum transport in a nonequilibrium steady state, which breaks time reversal invariance spontaneously, are investigated. The analysis is based on the probability distributions, generated by the correlation functions of the particle current and the entropy production operator. The general approach is applied to an exactly solvable model with a point‐like interaction driving the system away from equilibrium. The quantum fluctuations of the particle current and the entropy production are explicitly evaluated in the zero frequency limit. It is shown that all moments of the entropy production distribution are non‐negative, which provides a microscopic version of the second law of thermodynamics. On this basis a concept of efficiency, taking into account all quantum fluctuations, is proposed and analyzed. The role of the quantum statistics in this context is also discussed.     

Organocopper‐catalyzed living radical polymerization initiated with aromatic sulfonyl chlorides

The living radical polymerization of methyl methacrylate initiated from aromatic sulfonyl chlorides and catalyzed by the new catalytic systems CuSBu/bpy CuSPh/bpy and CuCCPh/bpy (bpy = 2,2′‐bipyridine) is described. For a target degree of polymerization of 200, lowering the ratio of catalyst to sulfonyl chloride group from 1/1 to 0.25/1 mol/mol decreases the values of the experimental rate constant of polymerization from 5.12 × 10⁻², 2.4 × 10⁻², and 1.87 × 10⁻² min⁻¹ to 1.8 × 10⁻³, 4.9 × 10⁻³, and 4.2 × 10⁻³ min⁻¹ for CuSBu, CuSPh, and CuCCPh, respectively, whereas the corresponding initiator efficiency increases from 62 to 99%. The external orders of reaction in the catalyst are 0.79 for CuSPh, 0.88 for CuCCPh, and 1.64 for CuSBu. A mechanistic interpretation that involves the in situ generation of, most likely, the real catalyst CuCl, starting from combinations of CuSBu, CuSPh, and CuCCPh and sulfonyl chloride or alkyl halide growing species, is suggested. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4353–4361, 2000     

The mechanism of chain growth in oxidative polycondensation of phenols

A new mechanism of chain extension in oxidative polycondensation of phenols has been proposed. Between the two accepted mechanisms: quinol ether redistribution and quinol ether rearrangement, the second mechanism seems to be the most important for the chain growth. The first mechanism, quinol ether redistribution, preserves the system average degree of polymerization and assures a permanent equilibration of the polymeric chains, but has only a minor contribution to the molecular weight increase. The second mechanism, quinol ether rearrangement, proved to be the most important for chain extension and was interpreted as a repeated Claisen rearrangement (a particular case of a sigmatropic rearrangement), characteristic to allyl ethers of phenols. Experimental data proved that the above mentioned mechanisms probably take place simultaneously and the real growth of the molecular weight is a result of the cumulative contributions of both mechanisms.     

Sintered and 3D-Printed Bulks of MgB2-Based Materials with Antimicrobial Properties

Pristine high-density bulk disks of MgB₂ with added hexagonal BN (10 wt.%) were prepared using spark plasma sintering. The BN-added samples are machinable by chipping them into desired geometries. Complex shapes of different sizes can also be obtained by the 3D printing of polylactic acid filaments embedded with MgB₂ powder particles (10 wt.%). Our present work aims to assess antimicrobial activity quantified as viable cells (CFU/mL) vs. time of sintered and 3D-printed materials. In vitro antimicrobial tests were performed against the bacterial strains Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Enterococcus faecium DSM 13590, and Enterococcus faecalis ATCC 29212; and the yeast strain Candida parapsilosis ATCC 22019. The antimicrobial effects were found to depend on the tested samples and microbes, with E. faecium being the most resistant and E. coli the most susceptible.     

Self‐Assembled Columnar Triazole Quartets: An Example of Synergistic Hydrogen‐Bonding/Anion–π Interactions

The self‐assembly of triazole amphiphiles was examined in solution, the solid state, and in bilayer membranes. Single‐crystal X‐ray diffraction experiments show that stacked protonated triazole quartets (T₄) are stabilized by multiple strong interactions with two anions. Hydrogen bonding/ion pairing of the anions are combined with anion–π recognition to produce columnar architectures. In bilayer membranes, low transport activity is observed when the T₄ channels are operated as H⁺/X^? translocators, but higher transport activity is observed for X^? in the presence of the K⁺‐carrier valinomycin. These self‐assembled superstructures, presenting intriguing structural behaviors such as directionality, and strong anion encapsulation by hydrogen bonding supported by vicinal anion–π interactions can serve as artificial supramolecular channels for transporting anions across lipid bilayer membranes.