Effects of hydrophobic–hydrophilic balance and stereochemistry on the supramolecular assembly of functionalized fullerenes

Molecular assemblies of C60, mono-substituted by ethyl, C60[C(COOC2H5)2], 1a; n-propyl, C60[C(COOC3H7)2], 1b; dodecyl, C60[C(COOC12H25)2], 1c; and triethyeleneglycol-monomethyl ether, C60[C(COO(CH2CH2O)3CH3)2], 1d, esters of malonic acid and three different regioisomeric bis-substituted isomers of C60, equatorial-C60[C(COOC2H5)2]2, 2a; trans3-C60[C(COOC2H5)2]2, 2b; and trans2-C60-[C(COOC2H5)2]2, 2c on water surfaces were investigated by surface pressure vs. surface area isotherms, Brewster-angle microscopy and absorption spectroscopy measurements. For the mono-adducts, true monolayer was demonstrated only from 1d while multilayer structures were formed from 1a, 1b and 1c upon compression. For the bis adducts, typical monolayer was seen only from 2c; in contrast no monolayers formed from upon spreading 2a and 2b on water, but monolayers and multilayers coexisted. All of the spread C60 derivatives could be transferred onto solid substrates by the Langmuir–Blodgett technique with transfer ratio close to unity.