A 9,9,9',9'-tetramethyl-4,4',10,10'-biacridine derivative without substituents at 2,2',7,7'-positions was synthesized. The X-ray analysis revealed formation of one-dimensional stacked column in the crystal. The compound underwent electron-transfer disproportionation by acid stimulus. The generated cation radical exhibited high stability in CH2Cl2 solution under air at room temperature over 10 days even without bulky protecting substituents. By neutralization with NEt3, biacridine was recovered in high yield via back electron transfer.