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)], 1 c; and triethyeleneglycol-monomethyl ether, C-60[C(COO(CH2CH2O)(3)CH3)(2)], 1d, esters of malonic acid and three different regioisomeric bis-substitut ed 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 surf aces were investigated by surface pressure vs. surface area isotherms, Brew ster-angle microscopy and absorption spectroscopy measurements. For the mon o-adducts, true monolayer was demonstrated only from 1d while multilayer st ructures were formed from 1a, 1b and 1c upon compression. For the bis adduc ts, typical monolayer was seen only from 2c; in contrast no monolayers form ed from upon spreading 2a and 2b on water, but monolayers and multilayers c oexisted. All of the spread C-60 derivatives could be transferred onto soli d substrates by the Langmuir-Blodgett technique with transfer ratio close t o unity. (C) 1999 Elsevier Science S.A. All rights reserved.