Theoretical studies on structures and stabilities of C2-C52X2 (XÂ =Â H, F, and Cl) isomers

C2-C52 has two chains of three adjacent pentagons, a pair of adjacent pentagons, and four isolated pentagons, which are highlighted by grey color. PM3, HCTH/3-21G, and B3LYP/6-31G∗ method have been employed for searching the most stable C2-C52X2 (X = H, F, and Cl) derivatives, and 28,52- and 26,52-C2-C52X2 (X = H, F, and Cl) are the two most stable ones, and that indicates carbon sites locate the chains of three adjacent pentagons are more chemically reactive than others.