IR spectroscopy applied subsequent to a proton transfer reaction in the excited state of isolated 3-hydroxyflavone and 2-(2-naphthyl)-3-hydroxychromone

Abstract

IR/R2PI-spectroscopy has been applied to the electronic ground and electronically excited states of 3-hydroxyflavone (3-HF) and 2-(2-naphthyl)-3-hydroxychromone (2-NHC) in a supersonic jet yielding direct structural information on the educt and product of a proton transfer reaction. We show that IR spectra of the electronically excited states can be recorded subsequent to a photoinduced chemical reaction, in this case a proton transfer. In combination with DFT and TDDFT calculations structural assignments are performed.

Structure of Isolated Xanthone in the T1 State Obtained via Combined UV/IR Spectroscopy

“…These experimentally obtained vibrational transitions fit excellently to the calculated frequencies of xanthone in the T 1 state (DFT/B3LYP/TZVP, scaled by 0.99, [9,10,49] Figure 4 b). The transitions can be assigned to combined CC stretching (ring deformation vibrations) and CÀH bending modes.…”

“…Recently we have also shown that combined nanosecond UV/IR/UV spectroscopy in molecular beam experiments in combination with ab initio calculations yield structural information on isolated molecules and clusters in the electronically excited state subsequent to a proton transfer reaction. [9,10] However, photoinduced reactions often not only involve singlet, but also triplet states. Herein, we show that triplet states of isolated molecules can be investigated by combined ns UV/IR/UV (IR/R2PI) spectroscopy.…”

“…It is interesting to note that this value is a further hint that the ionisation starts from the T 1 state. The origin of this state is at 25 808 cm À1 [29,30] and the ionisation potential was determined by photoelectron spectroscopy in two different publications to be at 69 686 cm À1 (8,64 eV) [32] or 68 718 cm À1 (8.52 eV), [35] leading to an energy of 43 [9,10,49] cf. Figure 3 b).…”

Time-dependent density functional theory study on excited state intramolecular proton transfer of 3-hydroxy-2-(pyridin-2-yl)-4H-chromen-4-one

“…These, in combination with the changing of the bonds lengths and bond angles, indicate that hydrogen-proton transfer happens in the four configurations. The same phenomenon has happened before [3,11,83]. The forms of proton transfer tautomer of 1a(O), 1a(N), and 1a(O)H + are consistent with the results of Chen et al [73].…”

“…Excited state intramolecular proton transfer (ESIPT) is one type of proton transfer reaction that has been investigated in the past few decades [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and has been of considerable interest. It is generally believed that the ESIPT process involves the transfer of a hydroxyl (or amino) proton to an acceptor in the excited state, giving rise to the proton transfer tautomer emission.…”