Counterion-mediated micellar growth for cetyltrimethylammonium 2,6-dichlorobenzoate alone and together with cetyltrimethylammonium chloride has been investigated using small-angle scattering techniques. Variations in counterion composition at constant ionic strength cause large changes in micelle size. The selectivity coefficient for adsorption of the aromatic counterion over chloride ions at CTA+ surfaces has been determined. The effects of the two counterions on micellar surface potentials, together with 1H NMR chemical shift data, allow inferences to be drawn about the penetration of the aromatic counterion into the head group region of the micelles. The aromatic ion increases the surfactant-packing parameter by both increasing the average volume per surfactant monomer, a cosurfactant-like effect, and decreasing the area per head group by screening electrostatic repulsions. Counterions such as chloride, which show only surface adsorption, affect only area and are much less effective at driving micellar growth. Some comparisons are also made with literature data for CTABr.

The syntheses and structures of cyclooctyne halogeno copper(I) complexes are described. The dimeric compounds [CuX(cyclooctyne)] 2 (5: 5a, X ) Cl; 5b, X ) Br; 5c, X ) I) are formed by reaction of equimolar amounts of cyclooctyne and copper(I) halide. X-ray structure analyses of all three compounds 5 show the copper(I) ion in a trigonal-planar coordination with bridging halide ligands. The complexes 5 react with an excess of cyclooctyne to give the monomeric bis(alkyne) complexes [CuX(cyclooctyne) 2 ] (7: 7a, X ) Cl; 7b, X ) Br; 7c, X ) I).Here, the three X-ray structure determinations prove that two η 2 -coordinated alkyne ligands are bound to a monomeric copper(I) halide unit. The reaction of the bromo complex 5b with 3,3,6,6-tetramethyl-l-thia-4-cycloheptyne (S-alkyne) affords the first mixed-alkyne copper complex [(cyclooctyne)CuBr 2 Cu(S-alkyne)] (9). Compound 9 forms dinuclear molecules in solution but a polymeric bent chain in the solid state (X-ray structure determination), in which one copper remains in a trigonal-planar environment and the other copper has a tetracoordinated structure.