CS-INDO/CI investigation on rotamerism and on excited singlet states of 1,2′-binaphthyl. The appearance of locally excited and twisted intramolecular charge-transfer states

A CS-INDO/S-CI study on rotamerism and on excited singlet states of 1,2′-binaphthyl (1,2′-BN) has been made. Two conformers of similar energy are found at high values of the torsional cordinate (φ= 55 and 125°). As regards the excited singlet states, it is found that S1–S4 are locally excited (LE) states, while S5 and S6 are twisted intramolecular charge-transfer (TICT) states. The consequence of these findings on the photophysical behaviour of 1,2′-BN is briefly discussed.