Intramolecular hydrogen bonding and photoinduced intramolecular proton and electron transfer in 2-(2′-hydroxyphenyl)benzothiazole

Intramolecular hydrogen bonding (IHB) and photoinduced intramolecular proton and electron transfer in 2-(2′-hydroxyphenyl)benzothiazole (HBT) were investigated theoretically. The IHB causes planarization of the molecule, which results in the change of the energy level of LUMO, and the change of density of state (DOS) of HOMO. The IHB and intramolecular proton transfer (IPT) was studied by IR spectra, which shows the influence of IHB to the IR spectra and the dynamics of IPT. The excited state properties of them are investigated with 2D and 3D real space representations, which revealed that the intramolecular charge transfer (ICT) also occurs when IPT happens. From the 3D transition density, the orientation of transition dipole moment for enol reverses, compared to that of normal. The orientation of ICT between enol and keto is opposite, which results from the opposite orientation of transition dipole moment between them.