Z. Slanina et al., Biologically active fullerene derivatives: Computations of structures, energetics, and vibrations of C-60(OH)(x) and C-60(NO2)(y), INT J QUANT, 74(3), 1999, pp. 343-349
This article reports quantum-chemical semiempirical computations of selecte
d multihydroxy and multinitro derivatives of C-60. Polyhydroxylated fullere
nes have been known for their efficient free-radical scavenging activity an
d promising results in reducing the concentration of free radicals in patho
logical blood and in inhibiting the growth of abnormal cells. Nitro-fullere
nes are directly linked to hydroxy-fullerenes as polyhydroxylated fullerene
s can be produced through hydrolysis of polynitro-fullerenes. In spite of t
his considerable biological application potential, microscopic knowledge of
the systems is very Limited. This study thus supplies' quantum-chemical se
miempirical (primarily PM3) calculations of the structure and energetics fo
r selected hydroxy- and nitro-fullerenes. The configurational sampling of C
-60(OH)(x) extends from x = 2 to x = 36. The computations offer a useful in
sight into the molecular structure, energetics, and possible stability meas
ures. It is suggested that thermodynamic stability could be measured throug
h a partial dissociation heat. Among the computed structures, C-60(OH)(6) a
nd C-60(OH)(18) exhibit the best value of the partial dissociation heat. Wi
th nitro-fullerenes, tetra-nitro derivatives were computed here. The comput
ations follow the finding for dinitro derivatives that low-energy structure
s have either the two nitro groups placed in the para position on one hexag
on or added to one 6/6 (double) bond of the cage. The lowest tetra-nitro sp
ecies found has the para-pal a arrangement applied to two hexagons separate
d by one pentagon. Hydroxy- and nitro-fullerenes do not exhibit the highest
topologically possible symmetry, that is, symmetry is lowered due to nonbo
nding interactions. (C) 1999 John Wiley & Sons, Inc.