Aromatic character studies on pentafulvalenes, and its derivatives via nuclear independent chemical shifts (NICS)

Pentafulvalenes are completely conjugated unsaturated molecules. Many works have been done on pentafulvalenes. In this work, DFT calculations were carried out on molecular structure of pentafulvalenes and pentafulvalene-like containing heavy atoms, 1X (X= C, Si, and Ge), and 2X (X= N ,P ,B and As) using 6-311++G** basis set of the GAUSSIAN 98 program. The aromatic character of 1X and 2X was investigated through magnetic criteria. Nuclear independent chemical shifts NICS (1.0) calculations clarified an aromatic character in both five rings of 1X and 2X, which was decreased from X=C to X=Si in 1X molecules. However, the aromatic character in 2X ring were decreased from X=N to X=P. The details and related discussions would be presented.