Search results for "BOND"

Synthesis, characterisation, and molecular and electronic structure of CpMoCl2(R1C≡CR2) (R1, R2 = Ph, Et, Me): a new class of half-sandwich 17-electr…

2000

International audience; Addition of alkyne to [CpMoCl2]2 affords compounds CpMoCl2(η2-alkyne) (alkyne = EtC[triple bond, length as m-dash]CMe, 1; EtC[triple bond, length as m-dash]CEt, 2; PhC[triple bond, length as m-dash]CMe, 3; PhC[triple bond, length as m-dash]CPh, 4) in good yields. The compounds have been characterised by C,H analyses, IR, EPR and mass spectroscopies, magnetic susceptibility, and cyclic voltammetry. In addition, a single crystal X-ray diffraction analysis has been carried out for compound 4. The alkyne ligand adopts an almost parallel conformation relative to the Cp ring, essentially identical with that of previously reported Nb, Ta, and W analogues. Geometry optimisat…

Chalcogen‐Bonding Interactions in Telluroether Heterocycles [Te(CH2)m]n(n=1–4;m=3–7)

2020

The Te⋅⋅⋅Te secondary bonding interactions (SBIs) in solid cyclic telluroethers were explored by preparing and structurally characterizing a series of [Te(CH2 )m ]n (n=1-4; m=3-7) species. The SBIs in 1,7-Te2 (CH2 )10 , 1,8-Te2 (CH2 )12 , 1,5,9-Te3 (CH2 )9 , 1,8,15-Te3 (CH2 )18 , 1,7,13,19-Te4 (CH2 )20 , 1,8,15,22-Te4 (CH2 )24 and 1,9,17,25-Te4 (CH2 )28 lead to tubular packing of the molecules, as has been observed previously for related thio- and selenoether rings. The nature of the intermolecular interactions was explored by solid-state PBE0-D3/pob-TZVP calculations involving periodic boundary conditions. The molecular packing in 1,7,13,19-Te4 (CH2 )20 , 1,8,15,22-Te4 (CH2 )24 and 1,9,17,…

Bringing a Molecular Plus One: Synergistic Binding Creates Guest-Mediated Three-Component Complexes

2020

Cethyl-2-methylresorcinarene (A), pyridine (B), and a set of 10 carboxylic acids (Cn) associate to form A·B·Cn ternary assemblies with 1:1:1 stoichiometry, representing a useful class of ternary systems where the guest mediates complex formation between the host and a third component. Although individually weak in solution, the combined strength of the multiple noncovalent interactions organizes the complexes even in a highly hydrogen-bond competing methanol solution, as explored by both experimental and computational methods. The interactions between A·B and Cn are dependent on the pKa values of carboxylic acids. The weak interactions between A and C further reinforce the interactions betw…

The influence of CH bond polarization on the self-association of 2-acylaminopyrimidines by NH/CH···O/N interactions: XRD, NMR, DFT, and AIM study

2013

The single crystal structures of two 2-acylaminopyrimidines, where alkyl groups in acyl moiety are iso-propyl (1) and dichloromethyl (2), were solved by X-ray diffraction method. The strength of intermolecular hydrogen bonding interactions depends on the C–H bond polarization increased by exchanging two methyl groups by chlorine atoms in the adjacent substituent. The computational methods provide an additional insight into the intermolecular interactions and are utilized in explaining the differences in the observed crystal structures. The experimental and computational data together explain the differences in the formed aggregates and revealed that these simple substitutions cause crucial …

Chiral Brønsted Acid-Catalyzed Asymmetric Allyl(propargyl)boration Reaction of ortho-Alkynyl Benzaldehydes: Synthetic Applications and Factors Govern…

2016

Chiral Bronsted acid-catalyzed allyl(propargyl)boration of ortho-alkynyl benzaldehydes gives rise to ω-alkynyl homoallylic(homopropargylic)alcohols that can be further transformed to complex molecular scaffolds via subsequent hydroalkoxylation, ring-closing enyne metathesis (RCEYM), or intramolecular Pauson–Khand reaction (PKR). Optimizations of each two-step transformation is reported. A strong dependence between enantioselectivities and the nature of the substitution at the alkynyl moiety is observed, showcasing that the triple bond is not merely a spectator in this transformation. Density functional theory (DFT) calculations (M06-2X/6-311+G(d,p)–IEFPCM//B3LYP/6-31G(d)) show that this dep…

Towards highly luminescent phenylene vinylene films

1996

Abstract Fluorescence and electronic absorption spectra, fluorescence decay curves and fluorescence quantum yields of a series of oligo (p-phenylene vinylenes) are investigated in solution, nanoaggregates and vapour-deposited or cast ultrathin films. The film constituting molecules are varied in chain length and modified by electron donating and withdrawing substituents and bulky alkyl spacers. PPP-MO calculations serve to rationalize the resulting spectral changes. In dilute solutions, fluorescence yields of the short oligomers with alkyl or oxyalkyl substituents approach the region of unity. The yields decrease with chain length, reaching a long-chain limit of ΦF=0.4–0.7. Introduction of …

Novel acrylamido monomers with higher hydrophilicity and improved hydrolytic stability: I. Synthetic route and product characterization.

1996

The novel acrylamido monomer reported by our group (N-acryloylaminoethoxyethanol, AAEE; Chiari et al., Electrophoresis 1994, 15, 177-186), found to combine high hydrophilicity with extraordinary resistance to alkaline hydrolysis, has come under closer scrutiny due to unexpected and random autopolymerization while stored as a 1/1 v/v water solution at 4 degrees C (possibly due to a greater oxidability of the ether group). We have additionally found a unique degradation pathway of the monomer, called "1-6 H-transfer", by which the C1 (on the double bond site), by constantly ramming against the C6, next to the ether oxygen (O7, which in fact favors the transfer of the hydrogen atom by C1), pro…

Liquid-crystalline ionomers

1997

Liquid-crystalline (LC) ionomers combine the properties of ionomers (cluster formation of the ionic groups) with LC phases. They can be prepared with LC main-chain and LC side-chain polymers.

1992

Zwitterionic polymers [CH 2 CR(COOR')] n (R= H, Me; R'= (CH 2 ) 11 + NMe 2 (CH 2 ) 3 SO 3 - , (CH 2 ) 2 + N(CH 3 )([CH 2 ] 3 SO 3 - )C 10 H 21 ) are studied by X-ray scattering. The structural order both in the short-range and long-range scale is investigated. The influence of the polymer backbone, of different locations of the ionic groups in isomeric polymers, of bound water and of added inorganic salts on the bulk structures is studied, and the observed rearrangements are analysed

1992

The molecular packing and spatial correlations of polymers [CH 2 CR(COOR')] n (R= H, Me; R'= (CH 2 ) 11 + NMe 2 (CH 2 ) 3 SO 3 - ; (CH 2 ) 2 + N(Me)[(CH 2 ) 3 SO 3 - ][C 10 H 21 ]) are studied by means of X-ray analysis and conformational calculations. The analysis of the correlation functions and density distribution profiles suggest a double-layered molecular packing which is discussed for the three polymers investigated, with respect to their different chemical structures. Whereas the zwitterionic polymethacrylates studied exhibit liquid-like short-range order, the polyacrylate analog exhibits an ordered double-layered superstructure