Thermally stable fullerene derivatives and process for producing the same

A fullerene derivative of the formula I ##STR26## where the symbols and indices have the following meanings:

• F is a fullerene radical of the formula (C.sub.20+2m), where m is a number from 1 to 50
• R.sup.1 to R.sup.8 are identical or different and are each H, NH.sub.2, CO.sub.2 R.sup.9, CN, OCOR.sup.10, COR.sup.10, Cl, BR, I, F, OR.sup.11, CONH.sub.2, C.sub.1 -C.sub.20 -alkyl which can be substituted by Cl, I, Br and F, C.sup.3 -C.sub.8 -cycloalkyl, aryl, heteroaryl, where R.sup.9 to R.sup.11 are each H, C.sub.1 -C.sub.20 -alkyl which can be substituted by F, Cl, Br or I, pyridinyl or phenyl which in turn can be substituted by F, Cl, Br, I, nitro, amino, C.sub.1 -C.sub.20 -alkylamino, C.sub.6 -C.sub.14 -arylamino, C.sub.1 -C.sub.20 -alkylamino, C.sub.6 -C.sub.14 -arylamino, C.sub.1 -C.sub.20 -alkoxy or C.sub.6 -C.sub.14 -aryloxy, or --(CH.sub.2).sub.j --CO.sub.2 H having J=1 to 10, R.sup.1 -R.sup.4 and/or R.sup.5, R.sup.7 can also be part of a cycloaliphatic, aromatic or heteroaromatic system which is in turn substituted by C.sub.1 -C.sub.20 -alkyl, aryl, carboxyl, carbonyl, alkoxy, aryloxy, F, Cl, Br, I, nitro, alcohol or amine, or R.sup.1 and R.sup.2, R.sup.2 and R.sup.3, R.sup.3 and R.sup.4 can in each case together be ##STR27## where R.sup.15 -R.sup.18 are each H, C.sub.1 -C.sub.20 -alkyl, F, Cl, Br, I or phenyl, and AR is the radical of a fused aromatic system, and R.sup.5 and R.sup.7 can together also be an --O-- bridge, n is from 1 to 20.