Quantum Chemical Study of Atomic Structure and Spin States of the Cox(C60)n (x=1-8, n=1-3) Complex Nanoclusters

Abstract

The main features of the local atomic structure of novel Con(C60)x (n=1-8, x=1-3) complexes and Con clusters as well were studied using the ab initio GGA calculations for a set of low and high energy isomers in different spin states. It is shown that high-spin low-symmetry structure of free-standing Con clusters is determined by Jahn-Teller distortions. For the Co(C60)x (x=1-3) isomers the spin state S=1/2 is energetically preferable whereas the low energy isomers of Co2(C60)x (x=1-3) have an intermediate spin state of S=1. The η2 (6-6 edge of C60) type of cobalt ion coordination is preferable for both n=1 and n=2 cases. The η2 (coordination with 6-5 edge) and even the η5 (C5 fragment) types serve as low and high energy intermediates for the cobalt ions migration around the C60 cage. Formation of cobalt dimers can be the final stage of evolution of Con(C60)x atomic structure approaching the equilibrium atomic geometry. For higher n (3-8) the formation of η2, η2 or η1 coordination bonds between Con fragment and C60 molecules through carbon hexagons results in stable complex nanoclusters with nonmonotonic change of average spin momentum upon the number of cobalt atoms in the Con cores. The theoretical results are compared with corresponding experimental data.