▎ 摘　　要

Highly strained cyclic xanthene dimers, which serve as models for reduced graphene oxide (RGO), were synthesized by Ni(0) mediated homo-coupling reactions. The dimers are obtained as highly stable colorless solids. X-ray crystallo-graphic analysis of a tetra-tert-butyl derivative demonstrates that it possesses a highly strained structure with an extremely short non-bonded O center dot center dot center dot O distance (2.5662(44)angstrom). The results of variable temperature NMR experiments show that no signal broadening occurs even at 398 K, indicating that conformational flipping requires considerably high energy.