‘Sacrificial’ supramolecular assembly and pressure-induced polymerization: toward sequence-defined functionalized nanothreads

Limited supramolecular strategies have been utilized to synthesize sequence-defined polymers, despite the prominence of noncovalent interactions in materials design. Herein, we illustrate the utility of ‘sacrificial’ aryl-perfluoroaryl supramolecular synthons to synthesize sp³-hybridized nanothreads from sp²-enriched reactants. Our strategy features A–B reactant pairs in the form of a phenol:pentafluorophenol co-crystal that is preorganized for an electronically-biased and sequence-defined polymerization. The polymerization, initiated at 12 GPa, affords an alternating copolymer featuring exogenous –OH functionalities. The external substitution is confirmed through IR spectroscopy. Importantly, the inclusion of the functional unit provides the first experimental glimpse at reaction mechanism: keto–enol tautomerization that can only occur during cycloaddition is observed through IR spectroscopy. Our approach realizes the first example of a functionalized nanothread and attains sequence definition through sacrificial supramolecular preorganization and presents a further approach for de novo design of complex nanothreads.

Supramolecular synthons are exploited to synthesize –OH functionalized sp³-rich sequence-defined nanothreads using pressure-induced polymerization of a phenol:pentafluorophenol co-crystal.      

Ab Initio High Pressure Investigations of InI

The high pressure behaviour of InI is studied by DFT‐calculations and compared with experimental data. The existence of a 5s² electron pair in In⁺ represents an unfavourable bonding situation for high symmetry structures because of effective closed shell repulsion. Since cations with a ns² electron pair are highly polarizable and the electronic situation is more favourable in the low symmetry structure InI prefers a TlI‐type structure at ambient pressure. A pressure induced transition to the more densely packed high symmetry CsCl‐type structure takes place at about 19 GPa according to our calculations. At ambient pressure the interactions are predominantly ionic. However with increasing pressure the distances between In⁺ cations in the TlI‐type structure diminish drastically, mainly due to the changing space requirement of the lone electron pair. Apart from ionic interactions further bonding interactions between the In⁺ cations occur. At elevated pressure the electron localization function (ELF) as well as the band structure diagrams suggest metallic bonding between the In⁺ within the zigzag chain, i. e. increasing bonding interactions between the In⁺ cations due to the electron pair and its s‐p‐mixing. At ambient pressure In‐In interactions are rather weak and the space requirement of the lone electron pair mainly determines the characteristic arrangement of the ions. At elevated pressure the In‐In interactions become stronger and stabilise themselves additionally the specific structural arrangement.     

Über Chalkogenidhalogenide des Chroms Synthese,Kristallstruktur und Magnetismus von Chromsulfidbromid,CrSBr

Chalkogenidehalides of Chromium. Synthesis, Crystal Structure, and Magnetism of Chromiumsulfidebromide, CrSBr CrSBr is obtained from chromium metal and S₂Br₂ in a sealed quartz ampoule at 880°C. It forms air stable, black crystals. The crystal structure determination (space group Pmmn, lattice constants a = 476.7(2), b = 350.6(2), c = 796.5(4) pm, Z = 2, R = 0.026) shows, that CrSBr crystallizes in the FeOCl structure type. The structure consists of layers which are stacked perpendicular to the c axis. The layers are formed by distorted, edge sharing CrS₄Br₂ octahedra. The interatomic distances are Cr? S 239.7 and 241.5 pm, Cr? Br 249.4 pm. To explain the unusual temperature factor of the Br atom the structure determination was additionaly carried out at 205 K and 118 K. A linear decrease of the coefficients of the anisotropic temperature factors of all atoms was found. The coefficients can be extrapolated to zero for 0 K. This shows the large displacement parameter U₁₁ of the Br atom to be caused by thermal vibrations. Even under forced conditions CrSBr does not form intercalation compounds with pyridine or tetracyanoethylene. CrSBr shows a marked antiferromagnetic behavior with a Néel temperature of 132 K and a critical field of 0.35 Tesla at 4.2 K.     

Expedient Diels-Alder assembly of 4-aryl-4-phenylsulfonyl cyclohexanones

The efficient preparation of 4-aryl-4-phenylsulfonyl cyclohexanones, containing a quaternary sulfone-bearing carbon centre, is described. Their synthesis proceeds in 38-78% overall yield by way of three steps: (i) sulfinate alkylation; (ii) methylenation; and (iii) regioselective Diels-Alder condensation with 2-trimethylsiloxybutadiene. The scope and limitations of the one-pot Mannich-type methylenation described were examined.     

Kinetic studies on the deaquation-anation of aquapentammine-cobalt(III) chloride

Summary The deaquation-anation of solid aquapentamminecobalt(III) chloride was studied isothermally and non-isothermally. Kinetic data were obtained from t.g.a. and were analysed using 17 rate laws known for solid state reactions. This reaction, long interpreted as S_N2, was found to obey an A1.5 rate law from both types of experiments. From the isothermal experiments, an E _a of 97.0 kJ mol^-1 was found.     

Ionization of aqueous toluic acids: Conductance and thermodynamics

Conductivities of aqueous solutions ofortho-, meta-, andpara-toluic acids have been measured for the concentration range 0.1–2 millimolar and at 5° intervals from 5 to 100°C. At each temperature pK _a(m) andA ₀ have been calculated using the paired ion model recently described by Fuoss. Thermodynamic parameters have been calculated for the ionization of each acid, and Walden products for the anions. Results are discussed in terms of contributions to acidity by enthalpy and entropy changes as well as by hydration of the various solute species.     

Die differenzierte,zeitliche Titration von Proteinen mit n/150 Kaliumcupri-3-tellurat

Zusammenfassung Es wird gezeigt, daß bei der differenzierten, zeitlichen Titration von Proteinen in genügender Menge (40 bis 60 mg) die Abbaukurve in deutlichen Stufen verläuft, die wahrscheinlich ganz bestimmten Peptidbindungen entsprechen.

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Summary It was shown that in the differential, periodic titration of proteins in sufficient amounts (40 to 60 mg) the degradation curve proceeds in distinct stages, which probably correspond to very definite peptide linkages.

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Résumé On montre que lors du titrage différentiel en fonction du temps de quantités suffisantes de protéines (40–60 mg), la branche décroissante de la courbe présente des parties distinctes qui correspondent vraisemblablement à des liaisons peptidiques bien déterminées.

     

A structure refinement of the high pressure modification BaI2-II

A high pressure phase BaI₂-II, which can be quenched and retained as a metastable form at ambient conditions, is reported. The structure has been determined by X-ray investigations using single crystals. BaI₂-II crystallizes in an anti-Fe₂P-type arrangement, space group $\text{P}\text{6}\text{2m, a = 9.142(6)}$Å, c = 5.173(3)Å, which is slightly denser than the PbCl₂-type structure found at normal pressure. Structural features of the two phases are discussed in comparison.     

Carbonyl‐Komplexe von Chrom,Molybdän und Wolfram mit Isocyanacetat. Reaktionen am koordinierten Isocyanacetat. Stabilisierung von Isocyanessigsäure und Isocyanacetylchlorid am Metall. Isocyanopeptide [1]

Carbonyl Complexes of Chromium, Molybdenum and Tungsten with Isocyano Acetate. Reactions of Coordinated Isocyanoacetate. Stabilization of Isocyanoacetic Acid and Isocyanoacetyl Chloride at the Metal Atom. Isocyanopeptides The reactions of [(OC)₅MCNCH₂CO₂Et] (M = Cr, W) with Na[N(SiMe₃)₂] or with KOH afford the isocyanoacetate complexes [(OC)₅MCNCH₂CO₂]^? ( 1,2 ). Similarly, the complex [(OC)₃Mo(CNCH₂CO₂^?Li⁺)₃] ( 4 ) was obtained from [(OC)₃Mo(CNCH₂CO₂Et)₃] ( 3 ) and LiOH. Protonation of 1 and 2 affords the sublimable isocyanoacetic acid complexes [(OC)₅MCNCH₂CO₂H] ( 5 , 6 ; M = Cr, W) in which the functional isocyanide is stabilized at the metal atom. Reactions of [(OC)₅WCNCH₂CO₂^?K⁺] and of [(OC)₃Mo(CNCH₂CO₂^?Li⁺)₃] with oxalyl dichloride give the isocyanoacetyl chloride compounds [(OC)₅WCNCH₂COCl] ( 9 ) (sublimable) and [(OC)₃Mo(CNCH₂COCl)₃] ( 10 ); the latter ( 10 ) was not isolated. Complexes 9 and 10 were reacted in situ with β‐alanine, glycine, phenylalanine and methionine esters as well as the peptide esters GlyGlyOEt, PhePheOMe, Phe‐β‐AlaOMe, and GlyGlyGlyOMe to form the isocyanoacetyl amino acid esters ( 11 ‐ 14 ) and the isocyanoacetyl peptide esters ( 15 ‐ 18 ) which are stabilized at the molybdenum atom.