Relative stabilities of 6/6 and 5/6 C60(CH2)3

Bridging with the -(CH2)3- group over a bond in C60 introduces a new five-membered ring and allows for three isomers. One originates in the 6/6 bond bridging, the other two in the 5/6 bridging with the central CH2 group located more above the related pentagon (5/65) or hexagon (5/66). According to the AM1 semi-empirical quantum-chemical calculations the ground state of the system is represented by the 6/6 structure, located 76 and 78 kJ/mol below the 5/65 and 5/66 species, respectively. A similar picture is produced by the MNDO, PM3 and SAM1 computations. The bridged bond remains as a relatively long single bond in the all three isomers (1.577, 1.621, 1.621 إ). IR spectra are also computed, and effects of temperature on the thermodynamic relative stabilities evaluated. The 6/6 species remains the dominant component of the equilibrium isomeric mixture even at high temperatures.