We herein report an efficient synthesis of dibenzo[a,m]rubicene, a new member of nonplanar cydopenta-fused polycyclic aromatic hydrocarbon, and its derivatives. It is found that the conformation and molecular packing of dibenzo[a,m]rubicenes in the solid state can be tuned by the substituting groups, and the silyleth-ynylated derivatives of dibenzo[a,m]rubicenes function as p-type organic semiconductors in solution-processed thin film transistors with field effect mobility of up to 1.0 cm(2) V-1 s(-1).