Intramolecular charge transfer effects on 4-hydroxy-3-methoxybenzaldehyde.

The absorption and fluorescence spectral characteristics of 4-hydroxy-3-methoxybenzaldehyde (HMB) have been studied in different solvents, pH and beta-cyclodextrin (beta-CD) and compared with 4-hydroxy-3,5-dimethoxybenzaldehyde (HDMB). The inclusion complex of HMB with beta-CD is analysed by UV-vis, fluorimetry, FT-IR, (1)H NMR, SEM and AM1 methods. In HMB, the normal emission (B band) is originates from a locally excited state and the longer emission (A band) is due to intramolecular charge transfer state (ICT). The OH group of HMB is present in the interior part of the beta-CD cavity and aldehyde group present in the upper part of the beta-CD cavity.