Showing papers by "Hiroshi Sekiya published in 2011"
TL;DR: In this paper, a T-shaped coordination structure for Co + (H 2 O) 3, which exposes empty coordination sites for additional H 2 O ligands, was investigated with the IR photodissociation spectroscopy in the OH stretch region and density functional theory calculations.
32 citations
TL;DR: This is the first observation of a photoionization-induced rearrangement of the water network in [FA-(H(2)O)(4)](+), and through DFT calculations, it is concluded that the rearrangements occurs due to entropic effects.
Abstract: Photoionization-induced rearrangement of the water network in the trans-formanilide 1 ∶ 4 cluster, FA–(H2O)4, has been investigated by using IR-photodissociation spectroscopy and quantum chemical calculations. The IR spectrum of FA–(H2O)4 in the S0 state shows that the observed cluster has a cyclic hydrogen-bonded structure where the CO group and the NH group of FA are bridged with four water molecules, consistent with the reported structure [E. G. Robertson, Chem. Phys. Lett., 2000, 325, 299]. However, the corresponding cyclic hydrogen-bonded structure in the D0 state of [FA–(H2O)4]+ is a minor product arising from photoionization via the S1–S0 origin of FA–(H2O)4. The dominant product has an extended H-bonded structure, where the intermolecular hydrogen bond between the hydrogen of the OH group of a water molecule and the CO group is dissociated. This is the first observation of a photoionization-induced rearrangement of the water network in [FA–(H2O)4]+. Through DFT calculations, we conclude that the rearrangement occurs due to entropic effects.
31 citations
TL;DR: IR-dip spectra of trans-acetanilide-water 1:1 cluster, AA-(H(2)O)(1), have been measured for the S( 0) and D(0) state in the gas phase and explicitly indicates that the water molecule in AA migrates from the CO group to the NH group in the D-state.
Abstract: IR-dip spectra of trans-acetanilide−water 1:1 cluster, AA-(H2O)1, have been measured for the S0 and D0 state in the gas phase. Two structural isomers, where a water molecule binds to the NH group o...
30 citations
TL;DR: Ab initio calculations show that a second stable "cyclic-nonplanar isomer" exists in addition to a "bridged-Planar isomers", and that an isomerization from a bridged-planarIsomer to a cyclic- nonplanar Isomer is most probably responsible for the short lifetimes of the vibronic states of 7AI(H(2)O)(3).
Abstract: A picosecond pump and probe experiment has been applied to study the excited state dynamics of 7-azaindole–water 1 ∶ 2 and 1 ∶ 3 clusters [7AI(H2O)2,3] in the gas phase. The vibrational-mode selective Excited-State-Triple-Proton Transfer (ESTPT) in 7AI(H2O)2 proposed from the frequency-resolved study has been confirmed by picosecond decays. The decay times for the vibronic states involving the ESTPT promoting mode σ(1) (850–1000 ps) are much shorter than those for the other vibronic states (2100–4600 ps). In the (1 + 1) REMPI spectrum of 7AI(H2O)3 measured by nanosecond laser pulses, the vibronic bands with an energy higher than 200 cm−1 above the origin of the S1 state become very weak. In contrast, the vibronic bands in the same region emerge in the (1 + 1′) REMPI spectrum of 7AI(H2O)3 with picosecond pulses. The decay times drastically decrease when increasing the vibrational energy above 200 cm−1. Ab initio calculations show that a second stable “cyclic-nonplanar isomer” exists in addition to a “bridged-planar isomer”, and that an isomerization from a bridged-planar isomer to a cyclic-nonplanar isomer is most probably responsible for the short lifetimes of the vibronic states of 7AI(H2O)3.
29 citations
TL;DR: In this paper, the authors showed that the 4′-diethylamino-3-hydroxyflavone (3) yields two polymorphic crystals, one monoclinic, space group P21/n (1a), and the other triclinic P1 (1b).
Abstract: Crystallization of 4′-diethylamino-3-hydroxyflavone (1) yields two polymorphic crystals. One is monoclinic, space group P21/n (1a), and the other triclinic, P1 (1b). In both crystals, the two adjac...
4 citations