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

Molecular assemblies of C-60, mono-substituted by ethyl, C-60[C(COOC2H5)(2)], 1a; n-propyl, C-60[C(COOC3H7)(2)]) 1b; dodecyl, C-60[C(COOC12H25)(2)], 1c; and triethyeleneglycol-monomethyl ether, C-60[C(COO(CH2CH2O)(3)CH3)(2)], 1d, esters of malonic acid and three different regioisomeric bis-substituted isomers of C-60, equatorial-C-60[C(COOC2H5)(2)](2), 2a; trans(3)-C-60[C(COOC2H5)(2)](2), 2b; and trans(2)-C-60-[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 C-60 derivatives could be transferred onto solid substrates by the Langmuir-Blodgett technique with transfer ratio close to unity. (C) 1999 Elsevier Science S.A. All rights reserved.