A detailed DFT/TDDFT study on excited-state intramolecular hydrogen bonding dynamics and proton-transfer mechanism of 2-phenanthro[9,10-d]oxazol-2-yl-phenol

In this present work, using density functional theory and time-dependent density functional theory methods, we theoretically study the excited-state hydrogen bonding dynamics and the excited state intramolecular proton transfer mechanism of a new 2-phenanthro[9,10-d]oxazol-2-yl-phenol (2PYP) system. Via exploring the reduced density gradient versus sign((2)(r))(r), we affirm that the intramolecular hydrogen bond O1-H2N3 is formed in the ground state. Based on photoexcitation, comparing bond lengths, bond angles, and infrared vibrational spectra involved in hydrogen bond, we confirm that the hydrogen bond O1-H2N3 of 2PYP should be strengthened in the S-1 state. Analyses about frontier molecular orbitals prove that charge redistribution of 2PYP facilitates excited state intramolecular proton transfer process. Via constructing potential energy curves and searching transition state structure, we clarify the excited state intramolecular proton transfer mechanism of 2PYP in detail, which may make contributions for the applications of such kinds of system in future.