Solar energy absorption in norbornadiene-quadricyclane system through electron donating or withdrawing substituents1

An attempt is made to maximize the solar energy absorption in norbornadiene ( 1 )-quadricyclane ( 2 ) system, through direct attachment of substituents at C1, C2, or C7 atoms of 1 ; calculating the corresponding energies at B3LYP/6-311++G** level of theory. The electron donating and electron withdrawing substituents of 1 n -X , attached at C2, were suitable for both solar absorption bands and solar energy storage. DFT calculations indicate that the solar absorption bands of 1 2-X were shifted to the visible spectrum region through the electron withdrawing substituents more than through electron donating substituents.