気相レーザー分光と理論計算によるホスト-ゲスト錯体の研究 : 構造と光化学

内容の要約広島大学(Hiroshima University)博士(理学)Doctor of Sciencedoctora

UV photodissociation spectroscopy of cryogenic cooled gas phase host-guest complex ions of crown ethers

International audienceThe best determination of the most stable protonation site in aromatic molecules relies nowadays on the IR spectroscopy and ab initio calculations. It appears that these methods are not necessarily unambiguous and cannot always be safely employed. We present in this paper an example showing that electronic spectroscopy of cold ions complemented with ab initio calculations gives clear results on the protonation site. In the example given on the aminophenol isomers (in ortho, meta and para positions), the protonation site is assigned from the electronic spectroscopy and in particular we show that for the meta isomer the proton is not on the amino group as observed for the other isomers. It shows also that the protonation site is not conserved in the electrospray evaporation–ionization process

Huge fluorescence lifetime elongation of catechol by complexation with18-Crown-6 ether

第30回化学反応討論会, 2014年6月4日-6日, イーグレひめじ(姫路

Ultraviolet Photodissociation Spectroscopy of Cold K+•Calix[4]arene Complex in the Gas Phase

The cooling of ionic species in the gas phase greatly simplifies the UV spectrum, which is of special importance to study the electronic and geometric structures of large systems, such as bio-related molecules and host-guest complexes. Many efforts have been devoted to achieving the ion cooling with a cold quadrupole Paul ion trap (QIT), but one problem was insufficient cooling of ions (up to ~30 K) in the QIT. In this study, we construct a mass spectrometer for ultraviolet photodissociation (UVPD) spectroscopy of gas-phase cold ions. The instrument consists of an electrospray ion source, a QIT cooled with a He cryostat, and a time-of-flight mass spectrometer. Giving a great care for the cooling condition, we can achieve ~10 K for the vibrational temperature of ions in the QIT, which is estimated from UVPD spectra of the benzo-18-crown-6 (B18C6) complex with potassium ion, K+•B18C6. Using this setup, we measure a UVPD spectrum of cold calix[4]arene (C4A) complex with potassium ion, K+•C4A. The spectrum shows a very weak band and a strong one at 36018 and 36156 cm–1, respectively, accompanied by many sharp vibronic bands in the 36000–36600 cm–1 region. In the geometry optimization of the K+•C4A complex, we obtain three stable isomers: one endo and two exo forms. On the basis of the total energy and UV spectral patterns predicted by density functional theory calculations, we attribute the structure of the K+•C4A complex to the endo isomer (C2 symmetry), in which the K+ ion is located inside the cup of C4A. The vibronic bands of K+•C4A at 36018 and 36156 cm–1 are assigned to the S1(A)–S0(A) and S2(B)–S0(A) transitions of the endo isomer, respectively.This work is partly supported by the Japan Society for the Promotion of Science (JSPS) through the program “Strategic Young Researcher Overseas Visits Program for Accelerating Brain Circulation”

Laser Spectroscopic Study of β-Estradiol and Its Monohydrated Clusters in a Supersonic Jet

The structure of 17β-estradiol (estradiol) and its monohydrated clusters is studied in a supersonic jet. The laser induced fluorescence (LIF) spectrum of estradiol shows several sharp bands in the 35050－35200 cm-1 region. Ultraviolet-ultraviolet hole-burning (UV-UV HB) and infrared-ultraviolet double-resonance (IR-UV DR) spectra of these bands indicate that they are due to four different conformers of estradiol originating from the orientation of two OH groups in the A- and D-rings. Attachment of one H2O molecule to estradiol shifts the monomer origin bands to red by ~350 cm-1 with keeping the interval between the four bands, suggesting that estradiol-H2O 1:1 complexes have conformations similar to those of the four bare estradiol conformers, and that the H2O molecule is bonded to the OH group of the A-ring (phenyl ring). In addition, very weak bands are also found near the origin bands of bare estradiol. These bands are attributed to isomers of estradiol-H2O 1:1 having a hydrogen-bond at the D-ring OH. We determine the conformation of bare estradiol and the structures of its monohydrated complexes with the aid of density functional theory, and discuss the relation between the stability of hydrated clusters and the conformation of estradiol.This is a preprint of an article published by American Chemical Society in Journal of Physical Chemistry A, 2012, available online: http://pubs.acs.org/doi/abs/10.1021/jp302209z.This work is supported from the Japan Society for the Promotion of Science (JSPS) through a Grant-in-Aid project (Nos. 18205003 and 21350016) and from MEXT through a Grant-in-Aid for the Scientific Research on Priority Area “Molecular Science for Supra Functional Systems” (No. 477)

Structure and hydrogen-bonding ability of estrogens studied in the gas phase

The structures of estrogens (estrone, β-estradiol, estriol) and their 1:1 hydrogen-bonded (hydrated) clusters with water formed in supersonic jets have been investigated by various laser spectroscopic methods and quantum chemical calculations. In the S1-S0 electronic spectra, all the three species exhibit the band origin in the 35050－35200 cm-1 region. By applying ultraviolet-ultraviolet hole-burning (UV-UV HB) spectroscopy, two conformers, four conformers and eight conformers, arising from different orientation of OH group(s) in the A-ring and D-ring, were are identified for estrone, β-estradiol, and estriol, respectively. The Infrared-ultraviolet double resonance (IR-UV DR) spectra in the OH stretching vibration were observed to discriminate different conformers of the D-ring OH for β-estradiol and estriol, and it is suggested that in estriol only the intramolecular hydrogen bonded conformer exists in the jet. For the 1:1 hydrated cluster of estrogens, the S1-S0 electronic transition energy is quite different depending on whether the water molecule is bound to A-ring OH or D-ring OH. It is found that the water molecule prefers to form an H-bond to the A-ring OH for estrone and β-estradiol due to the higher acidity of phenolic OH than that of the alcoholic OH. On the other hand, in estriol the water molecule prefers to be bound to the D-ring OH due to the formation of a stable ring-structure H-bonding network with two OH groups. From these results, we conclude that estriol has a hydrogen bonding ability quite different from that of β-estradiol although their difference is just only one substituent.This is a preprint of an article published by American Chemical Society in Journal of Physical Chemistry A, 2013, available online: http://pubs.acs.org/doi/abs/10.1021/jp407438j

The structure of estrogens and their physiological properties studied by laser spectroscopy and quantum chemical calculation

第7回分子科学討論会, 2013年9月24日-27日, 京都テルサ(京都), 3P01

超音速ジェット中でのレーザー分光を用いたestrogenの構造に関する研究

第5回分子科学討論会, 2011年9月20日-23日, 札幌コンベンションセンター(札幌), 2A0

THE SPECTROSCOPIC STUDY OF ESTROGEN AND ITS HYDRATED CLUSTERS IN A SUPER SONIC JET

Author Institution: Department of Chemistry, Graduate School of Science, Hiroshima University, Higashi-hiroshima, 739-8526, JapanStructures of estrogen and its hydrated clusters have been studied by several laser spectroscopies in supersonic jet. The electronic spectrum of estrogen shows several origin bands. By observing UV-UV hole-burning and IR-UV spectra, it is concluded they are due to different conformers originating from difference of orientation of OH group(s). We also observed electronic and IR spectra of estrogen-H$_2$O. By aids of DFT calculations, the conformations and hydrated structures are determined