CH/71 interaction

The 71-electrons of aromatic rings can interact with charged species, yielding strong cation-71 interactions dominated by electrostatic and polarization effects. Interactions with CH units is also possible. For CH-ti interactions in both alkyl-and aryl-based model systems, dispersion effects dominate the interaction, but the electrostatics term is also relevant for aryl CH-ti interactions. ... 

Polymers organized in this unusual state behave as hexagonal mesophases similar to those observed in the bulk at suitable temperature/pressure conditions and adopt the extended chain conformation. Polymers included in nanochannels were discovered a few decades ago [33,34], but the mesomorphic properties and the stabilizing interactions were established much later by advanced spectroscopic techniques [35-41]. The preparation of novel macro-molecular adducts, melting at temperatures as high as 350 °C and sustained by CH- 71 intermolecular interactions, has been a success of supramolecular chemistry in fabricating high performance nanostructured materials [42]. 

The position of the refined a-hydrogen atoms is noteworthy. Both are pointed towards the metal (CeC(12)H(17) 93° and CeC(ll)H(16) 90°), and this results in short Ce-H distances (Ce-H(17) 2.82 and Ce H(16) 2.71 A). Similar a-CH agostic interactions have been observed for a number of lanthanoid and actinoid carbyls and reflect the high electron deficiency of those compounds [58]. 

Only 38 exhibits a selective response toward three analytes capable of CH-ti interactions, while for the other ones the responses are comparable or even lower to those of the polymer coatings, where no host-guest interactions are present. Therefore the dimensions of the preorganized cavity do not constitute a determinant factor for sensor selectivity, which depends on the presence of a 71-basic cavity, easily attainable from the gaseous analyte. 

V. Gutman, The Donor-Acceptor Approach To Molecular Interactions, Plenum Press, New York, 1978, ch. 3. 

Note that Fig. 3.55 is the more exact counterpart of Fig. 4 in Brunck and Weinhold, note 71. Note also that the full potential barrier includes contributions from gauche-type interactions at other dihedral angles. In this context, it is interesting that an idealized cosine-like dependence of the o cc-o ch overlap (or Fock-matrix element), namely... 

In the HMBC spectrum this NH proton exhibited 3/(CH) correlation to the C3" (5174.15) and 2/(CH) interaction to the C13 (5165.48) carbonyl, the latter in turn showing 2/(CH) interaction with H12(56.05). Thus it became clear that a carboxamide group linked the conjugated triene and the cyclopentenone unit. A 2/(CH) coupling of the triene terminus H7 to C4 (5jj/5c 5.86/71.20) established the point of attachment of the triene unit to C4. An observed NOE interaction between the H7 and H5 lent further support to this attachment and was suggestive of proximal orientation of the trans-A1 bond to the epoxy unit in the most preferred conformation. The absolute configuration at C4 was not established. 

XPS studies have revealed unusual and interesting CT interactions in WC16 and MoCl5-doped (CH)X [71]. A lowering of BE was observed for C, W, Mo and Cl after doping, and it was attributed to an increase in the outershell electron densities of these elements in the complexes. The increase has been explained in terms of the transfer of pit-electrons of the olefins to the metal d-orbital, followed by the back-donation to the pit orbital of the olefins and the Cl- ligands. 

Cyanoacetic Acid or Mol Oflic Nptriie (called Cyanessigsaure or Malonsaure-mononitril in Ger), NC-.CH. COOH mw 85.06, N 16.47 wh hygr cryscs, mp 69-71, bp l60 (dec) sol in w, ale eth prepd by interaction of Na ch loro acetate K cyanide soln. This compd forms numerous salts, some of which are unstable... 

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