Abstract: | Equilibrium geometries and relative stabilities of 24 possible isomers for C78O4 based on C78 (C2v) were studied by intermediate neglect of differential overlap (INDO) calculations. It was indicated that the most stable geometry is 28,29,30,31,52,53,73,78‐C78O4, where three oxygen atoms are added to the same hexagon, through which the longest axis of C78 (C2v) goes, and the forth oxygen atom is added to the C(73)? C(78) bond intersected by the shortest axis of C78 (C2v), and epoxide structures are formed. Electronic spectra of C78O4 isomers were investigated based on the optimized geometries. The blue shift of the first absorption for 28,29,30,31,52,53,73,78‐C78O4 compared with that of C78 (C2v) was rationalized and nature of transition for the peaks discussed. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 |