Lone electron pair micelles

Higher homologues start at N = 4 they allow more pronounced departures from the galena-like array, especially in the form of locally "inflated interspaces that accommodate lone electron pairs of quasi-octahedral Bi or Sb (so-called lone electron pair micelles, Makovicky Mumme, 1983). Onjy and are known for the Ag-free subsystem Pb-Bi-S. Reduction of symmetry in from the usual orthorhombic to monoclinic, caused by Pb/Bi ordering that proceeded differently for the two (originally) mirror-related slabs was exceptionally observed in one natural occurrence of (Mumme, unpubl.). Allowing for the Ag+Bi = 2Pb substitution in octahedral layers, also the cases L, and... 

Figure 6. The crystal structure of gustavite, PbAgBi g (Kupcfk Steins 1990). In order of decreasing size circles denote S, Pb, Bi and (Ag,Bi) two atomic levels of the orthorhombic subcell, 2 A apart, are indicated by void and filled circles. Stippling indicates cores of large lone electron pair micelles in which the pairs of Bi are concentrated.

Figure 8.5. Plot of the system constants (solvation parameter model) against composition for a mixed micelle electrolyte solution containing 50 mM sodium N-dodeconyl-N-methyltaurine and different amounts of the non-ionic surfactant Brij 35 (polyoxyethylene [23] dodecyl ether) (Left). Plot of the system constants for a mixed micelle buffer containing 50 mM sodium N-dodecanoyl-N-methyltaurine and 20 mM Brij 35 against the volume fraction of acetonitrile added to the electrolyte solution (Right). System constants m = difference in cavity formation and dispersion interactions r = difference in electron lone pair interactions s = difference in dipole-type interactions a = difference in hydrogen-bond basicity and b = difference in hydrogen-bond acidity. (From ref. [218] Royal Society of Chemistry).

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