ロバート ・ ベルガー (ドイツ ・ マールブルク大学マールブルク) をありがとう私たちのデータと分子のカイラリティの解釈についての議論を一般に感激します。サンプルを提供するため ZHAW ウェデンスウィル (スイス) からジュリア Kiedrowski、アレキサンダー Schießer とダルムシュタット工科大学 (ドイツ) からマイケル ・ Reggelin と同様、ベンジャミン Spenger、マヌエル Mazenauer Jürgen Stohner に感謝しております。
プロジェクトは、フォーカスひも (カイラル系の電子ダイナミクス) と連邦教育省と研究 (BMBF) の下、科学的と優れた経済性のヘッセン州イニシアティブによって支えられました。MS は、アドルフ ・ メッサー財団によって支援を確認します。

<ol>
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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coulomb+Explosion+Imaging+of+small+molecules.">Coulomb Explosion Imaging of small molecules.</a> Science. 244 (4903), 426-431 (1989).</li><li>Herwig, P. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+the+Absolute+Configuration+of+a+Chiral+Epoxide+in+the+Gas+Phase.">Imaging the Absolute Configuration of a Chiral Epoxide in the Gas Phase.</a> Science. 342 (6162), 1084-1186 (2013).</li><li>D&#246;rner, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cold+Target+Recoil+Ion+Momentum+Spectroscopy:+a+'momentum+microscope'+to+view+atomic+collision+dynamics.">Cold Target Recoil Ion Momentum Spectroscopy: a 'momentum microscope' to view atomic collision dynamics.</a> Physics Reports. 330, 95-192 (2000).</li><li>Ullrich, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recoil-ion+and+electron+momentum+spectroscopy:+reaction-microscopes.">Recoil-ion and electron momentum spectroscopy: reaction-microscopes.</a> Rep. Prog. Phys. 66 (9), 1463-1545 (2003).</li><li>Jagutzki, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiple+Hit+Readout+of+a+Microchannel+Plate+Detector+With+a+Three-Layer+Delay-Line+Anode.">Multiple Hit Readout of a Microchannel Plate Detector With a Three-Layer Delay-Line Anode.</a> IEEE Trans Nucl Sci. 49 (5), 2477-2483 (2002).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> RoentDek GmbH MCP Delay Line Detector Manual. , (2017).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> RoentDek GmbH The RoentDek Constant Fraction Discriminators CFD8c, CFD7x, CFD4c, CFD1c and CFD1x. , (2017).</li><li>Zeller, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+the+He2+quantum+halo+state+using+a+free+electron+laser.">Imaging the He2 quantum halo state using a free electron laser.</a> PNAS. 113 (51), 14651-14655 (2016).</li><li>Pitzer, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stereochemical+configuration+and+selective+excitation+of+the+chiral+molecule+halothane.">Stereochemical configuration and selective excitation of the chiral molecule halothane.</a> J. Phys. B.: At. Mol. Opt. Phys. 49 (23), 234001 (2016).</li><li>Hine, J., Dowell, A. M., Singley, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carbon+Dihalides+as+Intermediates+in+the+Basic+Hydrolysis+of+Haloforms:+IV+Relative+Reactivities+of+Haloforms.">Carbon Dihalides as Intermediates in the Basic Hydrolysis of Haloforms: IV Relative Reactivities of Haloforms.</a> J. Am. Soc. Chem. 78, 479-482 (1956).</li><li>Wales, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+coincidence+detection+algorithm+for+improving+detection+rates+in+coulomb+explosion+imaging.">A coincidence detection algorithm for improving detection rates in coulomb explosion imaging.</a> Nucl. Instr. Meth. in Phys. Res. A. 667, 11-15 (2012).</li><li>Kastirke, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Konstruktion und Aufbau einer UHV-tauglichen COLTRIMS-Kammer. , (2014).</li><li>Calegari, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Charge+migration+induced+by+attosecond+pulses+in+bio-relevant+molecules.">Charge migration induced by attosecond pulses in bio-relevant molecules.</a> J. Phys. B.: At. Mol. Opt. Phys. 49 (14), 142001 (2016).</li><li>Gaie-Levrel, F., Garcia, G. A., Schwell, M., Nahon, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=VUV+state-selected+photoionization+of+thermally-desorbed+biomolecules+by+coupling+an+aerosol+source+to+an+imaging+photoelectron/photoion+coincidence+spectrometer:+case+of+the+amino+acids+tryptophan+and+phenylalanine.">VUV state-selected photoionization of thermally-desorbed biomolecules by coupling an aerosol source to an imaging photoelectron/photoion coincidence spectrometer: case of the amino acids tryptophan and phenylalanine.</a> Phys. Chem. Chem. Phys. 13, 7024-7036 (2010).</li><li>Ablikim, U., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+absolute+geometries+of+cis+and+trans+molecular+isomers+by+Coulomb+Explosion+Imaging.">Identification of absolute geometries of cis and trans molecular isomers by Coulomb Explosion Imaging.</a> Sci. Rep. 6, 38202 (2016).</li></ol>

著者は競争の興味を宣言しません。

コンポーネントの変化のために COLTRIMS セットアップ技術、真空技術、粒子の検出、高速エレクトロニクスおよびデータ解析の分野を中心にかなり高いレベルが必要です。複雑な種の調査をみると、前にそれこのようにチェックすべき徹底的に適切、例えば実行して二原子あるいは三原子種の測定の分析によって、セットアップを実行します。
強度と分子ジェット?...

カイラリティは、150 年以上の魅力的な研究をされている私たちの自然の機能です。19thの世紀、パストゥール、ヴァントホッフ ホフは、スーパー imposable - 左と右の手のようではない 2 つのミラー ・ イメージ構造分子が発生することを発見しました。このプロパティは 'キラル'、'手' のためのギリシャの単語から名付けられました。
これまでのところ、熱力学的性質または左、右利きフォーム (2 ' 異性') のエネルギー準位の違いが見つかりませんでした。ある特定のサンプルの利き手を分析し、光学異性体を分離するには、たとえば chromatographical のさまざまなアプローチで行われるようにも、他のキラル分子との相互作用は使用できます。1キロプティカル (振動) 円の二色性、(V) CD、旋光分散、ORD などが日常的に手口を光学異性体を区別します。2
微細構造の決定になると、これらの手法は量子化学的計算からなどの追加情報を必要です。絶対構成を直接決定する広く受け入れられている唯一のテクニックは異常 x 線回折です。3
最近、クーロン爆発イメージングによる単純な光学活性種の絶対配置を決定ことができることが示されています。4,5このアプローチで気相分子が乗算イオン、残りのコアは強く互いを撃退します。この反発は、分子の高速断片化 ('爆発') に します。方向と大きさの小さい分子の-分子の構造にフラグメントの運動量相関運動量方向驚くほど結合軸にも対応します。加速器からのビームは分子を用いた分子構造決定のためのクーロン爆発を開拓されています。6このビーム箔の技術は最近もキラル認識の適用。7
反して異常 x 線回折、結晶が、気相を提供、サンプルはいけません。クーロン爆発アプローチにより、揮発性の種にとって理想的、従って x 線回折法を補完するもの。特定のケースで、利き手は個々 の分子についても決定できます。
実習では、分子構造の正確な再構成はメタン誘導体、例えば中央の炭素と置換基の異なる分子にも難しい証明されています。これはフラグメント間の相互作用は、クーロンではありません、すべての社債を同時に破るという事実に起因します。特に光学異性体を区別するための立体情報を取得するためには、この復興は必要ありません幸いにも。代わりに、異なるフラグメントの運動量のベクトルは左および右利きの分子の異なる量を生成するために関連付けることができます。信頼性の高い結果を得るため、少なくとも 4 つのフラグメントの運動量は記録する必要があります。
この勢いの情報を測定するために 1 つの測定手順で検出される 1 つ- と -1 つだけ分子ブレーク アップからフラグメントであります。この条件は、'一致検出' と呼ばれます通常。さらに、発光方向ある、分析リストモード データ形式で時間とフラグメントの位置を記録する練習の量に影響を与えます。
原子・分子物理学では、質量分離と時間および位置依存多ヒット検出器のための静電スペクトロ メーターを用いた測定は、このアプローチを実装、技術が開発されています。最も顕著な例の反応顕微鏡としても知られている-COLTRIMS (冷たいターゲット反跳イオン運動量分光法) 設定です。8,9この種の実験のためのスケッチは、図 1で与えられます。同様に電子を記録できる標準的な COLTRIMS に反してクーロン爆発イメージング イオン検出器のみが必要です。
分光計と検出器は、超高真空下でマウントされます (&#60; 1 x 10-9 hPa) 残留ガスからイオンの作成を避けるために。サンプルの分子は、超音速の拡張によって作成された気体自由分子ジェットを通じて提供されます: 蒸気圧のおかげで分子を真空に小さなノズル (約 50 μ m 径) を展開します。ソース チャンバー実験のこの部分は、通常 2 つのスキマーと差動排気される段階で相互作用領域から区切られます。追加セクションを特異的励起はガス噴流をダンプし、相互作用領域の背景のガスを避けるため相互作用領域の後ろに位置しています。
電離放射線は分子ジェット下 90 ° で交差しています。シンクロトロン放射光高速イオンまたは電子衝撃がクーロン爆発を誘発することが可能 '発射' ほとんどの実験室は最近フェムト秒レーザー パルスを使用します。
次のプロトコルが想定をイオンとフェムト秒レーザーの同時イメージングのためのセットアップを実行、実験室で利用できます。4 つまたは 5 つのフラグメントにクーロン爆発を誘発するために必要なピーク強度は 6 x 1014 W/cm2程度する必要があります。非常に長い測定を避けるためには、レーザーの繰り返し周波数は 10 kHz 以上をする必要があります。なぜなら、一方で一致検出のみ確認できますレーザー フォーカスの断片化の確率が大幅レーザー パルス (理想的には 10% 以上) あたり 1 未満の場合、これは重要です。全体の断片化率一方、必要がありますがないため数 kHz より低い関連する multifragmentation 経路のシェアは通常よりも少ない 10-4。促すだけ実際には、原則として既に単一断片化イベントは体サンプルの構成を特定するのに足りるとの光学異性体の豊かさを決定することができます検出される数百の特筆すべき、未知の光学異性体組成のサンプルです。

<table><tbody><tr><td>CHBrCl2</td><td>SigmaAldrich</td><td>139181-10G</td><td>or other suitable sample</td></tr><tr><td>femtosecond laser system</td><td>KMLabs</td><td>Wyvern500</td><td></td></tr><tr><td>High-reflective mirrors</td><td>EKSMA</td><td>042-0800</td><td></td></tr><tr><td>mirror mounts</td><td>Newport</td><td>U100-A-LH-2K&amp;nbsp;&amp;nbsp;</td><td></td></tr><tr><td>focusing mirror (protected silver, f = 75 mm)</td><td>Thorlabs&amp;nbsp;</td><td>CM254-075-P01</td><td>(if available: f = 60 mm)</td></tr><tr><td>COLTRIMS spectrometer, including electronics and data acquisition system</td><td>RoentDek</td><td>custom</td><td>contrary to the standard COLTRIMS, only one detector is needed</td></tr></tbody></table>

coulomb explosion imaging as a tool to distinguish between stereoisomers

この資料は、COLTRIMS (冷たいターゲット反跳イオン運動量分光法)、または「反応顕微鏡」を使用して、個々 分子のレベルで単純な光学活性種の光学異性体 (立体異性体) を区別する方法を示しています。このアプローチでサンプルの気体分子ジェットは真空チャンバー内に展開され、フェムト秒 (fs) と交差します。パルスの強度は、いくつかの陽イオン (正荷電の) フラグメントを生成するいわゆるクーロン爆発の点火の多重電離を高速につながります。静電場は、時間と位置敏感検出器にこれらの陽イオンをガイドします。飛行時間質量分析計と同様に、各イオンの到着時刻はその質量の情報を得られます。黒字として静電場は、放射方向と最適化の後の運動エネルギーにつながるバリエーション飛行時間および影響の位置検出器の方法で調整されます。
各イオンの影響、検出器の電子信号を作成します。この信号は高周波エレクトロニクスによって処理され、コンピューターでイベントごとを記録しました。登録したデータは衝突時刻と位置に対応します。これらのデータと、エネルギーと各フラグメントの排出方向を計算できます。これらの値は、調査、すなわち結合距離と分子による分子に単純な光学活性種やその他の異性体の機能の利き手を決定できるように、原子の相対的な位置の下で分子の構造特性に関連付けられます。

この部分で halomethanes の得られた結果を示す.これらの種は、そのシンプルさと高い蒸気圧のための原理実証実験に最適です。一方より複雑な種ハロタンは、多重電離を誘導するために放射光を単一の軟 x 線光子を用いて検索されてきた。14
CHBrClF
Bromochlorofluorom...

Watch this Scientific Journal Video about Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers at JoVE.com

Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers

立体異性体を区別するためのツールとしてクーロン爆発イメージング

小さな光学活性種クーロン爆発イメージングは、個々 の分子の利き手を決定するための新しいアプローチを提供します。

This article shows how the COLTRIMS (Cold Target Recoil Ion Momentum Spectroscopy) or the "reaction microscope" technique can be used to distinguish ...

coulomb-explosion-imaging-as-tool-to-distinguish-between

Education

Research

JoVE Core

JoVE Journal

Organic Chemistry

Chemistry

Unit 1

Transition Metals and Coordination Complexes

Stereoisomerism

SCIENTISTS IN ACTION

9.0K ビュー.  Goethe-Universität Frankfurt am Main. 小さな光学活性種クーロン爆発イメージングは、個々 の分子の利き手を決定するための新しいアプローチを提供します。

ビデオ: Coulomb Explosion Imaging as a Tool to Distinguish Between Stereoisomers

Spatial Separation of Molecular Conformers and Clusters

Gas-phase molecular physics and physical chemistry experiments commonly use supersonic expansions through pulsed valves for the production of cold molecular beams. However, these beams often contain multiple conformers and clusters, even at low rotational temperatures. We present an experimental methodology that allows the spatial separation of these constituent parts of a molecular beam expansion. Using an electric deflector the beam is separated by its mass-to-dipole moment ratio, analogous to a bender or an electric sector mass spectrometer spatially dispersing charged molecules on the basis of their mass-to-charge ratio. This deflector exploits the Stark effect in an inhomogeneous electric field and allows the separation of individual species of polar neutral molecules and clusters. It furthermore allows the selection of the coldest part of a molecular beam, as low-energy rotational quantum states generally experience the largest deflection. Different structural isomers (conformers) of a species can be separated due to the different arrangement of functional groups, which leads to distinct dipole moments. These are exploited by the electrostatic deflector for the production of a conformationally pure sample from a molecular beam. Similarly, specific cluster stoichiometries can be selected, as the mass and dipole moment of a given cluster depends on the degree of solvation around the parent molecule. This allows experiments on specific cluster sizes and structures, enabling the systematic study of solvation of neutral molecules.

We present a technique that allows the spatial separation of different conformers or clusters present in a molecular beam. An electrostatic deflector is used to separate species by their mass-to-dipole moment ratio, leading to the production of gas-phase ensembles of a single conformer or cluster stoichiometry.

分子適合体とクラスターの空間的分離

Gas-phase molecular physics and physical chemistry experiments commonly use supersonic expansions through pulsed valves for the production of cold ...

工学

Direct Imaging of Laser-driven Ultrafast Molecular Rotation

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb explosion imaging setup in which a hitherto-impractical camera angle is realized. In our imaging technique, diatomic molecules are irradiated with a circularly polarized strong laser pulse. The ejected atomic ions are accelerated perpendicularly to the laser propagation. The ions lying in the laser polarization plane are selected through the use of a mechanical slit and imaged with a high-throughput, 2-dimensional detector installed parallel to the polarization plane. Because a circularly polarized (isotropic) Coulomb exploding pulse is used, the observed angular distribution of the ejected ions directly corresponds to the squared rotational wave function at the time of the pulse irradiation. To create a real-time movie of molecular rotation, the present imaging technique is combined with a femtosecond pump-probe optical setup in which the pump pulses create unidirectionally rotating molecular ensembles. Due to the high image throughput of our detection system, the pump-probe experimental condition can be easily optimized by monitoring a real-time snapshot. As a result, the quality of the observed movie is sufficiently high for visualizing the detailed wave nature of motion. We also note that the present technique can be implemented in existing standard ion imaging setups, offering a new camera angle or viewpoint for the molecular systems without the need for extensive modification.

We present a protocol for creating a real-time movie of a molecular rotational wave packet using a high-resolution Coulomb explosion imaging setup.

レーザー駆動の超高速分子回転のダイレクトイメージング

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb ...

化学

Direct Comparison of Hyperspectral Stimulated Raman Scattering and Coherent Anti-Stokes Raman Scattering Microscopy for Chemical Imaging

Stimulated Raman scattering (SRS) and coherent anti-Stokes Raman scattering (CARS) microscopy are the most widely used coherent Raman scattering imaging technologies. Hyperspectral SRS and CARS imaging offer Raman spectral information at every pixel, which enables better separation of different chemical compositions. Although both techniques require two excitation lasers, their signal detection schemes and spectral properties are quite different. The goal of this protocol is to perform both hyperspectral SRS and CARS imaging on a single platform and compare the two microscopy techniques for imaging different biological samples. The spectral focusing method is employed to acquire spectral information using femtosecond lasers. By using standard chemical samples, the sensitivity, spatial resolution, and spectral resolution of SRS and CARS in the same excitation conditions (i.e., power at the sample, pixel dwell time, objective lens, pulse energy) are compared. The imaging contrasts of CARS and SRS for biological samples are juxtaposed and compared. The direct comparison of CARS and SRS performances would allow for optimal selection of the modality for chemical imaging.

This paper directly compares the resolution, sensitivity, and imaging contrasts of stimulated Raman scattering (SRS) and coherent anti-Stokes Raman scattering (CARS) integrated into the same microscope platform. The results show that CARS has a better spatial resolution, SRS gives better contrasts and spectral resolution, and both methods have similar sensitivity.

化学イメージングのためのハイパースペクトル刺激ラマン散乱とコヒーレントアンチストークスラマン散乱顕微鏡の直接比較

Stimulated Raman scattering (SRS) and coherent anti-Stokes Raman scattering (CARS) microscopy are the most widely used coherent Raman scattering imaging ...

Differential Imaging of Biological Structures with Doubly-resonant Coherent Anti-stokes Raman Scattering (CARS)

Coherent Raman imaging techniques have seen a dramatic increase in activity over the past decade due to their promise to enable label-free optical imaging with high molecular specificity 1. The sensitivity of these techniques, however, is many orders of magnitude weaker than fluorescence, requiring milli-molar molecular concentrations 1,2. Here, we describe a technique that can enable the detection of weak or low concentrations of Raman-active molecules by amplifying their signal with that obtained from strong or abundant Raman scatterers. The interaction of short pulsed lasers in a biological sample generates a variety of coherent Raman scattering signals, each of which carry unique chemical information about the sample. Typically, only one of these signals, e.g. Coherent Anti-stokes Raman scattering (CARS), is used to generate an image while the others are discarded. However, when these other signals, including 3-color CARS and four-wave mixing (FWM), are collected and compared to the CARS signal, otherwise difficult to detect information can be extracted 3. For example, doubly-resonant CARS (DR-CARS) is the result of the constructive interference between two resonant signals 4. We demonstrate how tuning of the three lasers required to produce DR-CARS signals to the 2845 cm-1 CH stretch vibration in lipids and the 2120 cm-1 CD stretching vibration of a deuterated molecule (e.g. deuterated sugars, fatty acids, etc.) can be utilized to probe both Raman resonances simultaneously. Under these conditions, in addition to CARS signals from each resonance, a combined DR-CARS signal probing both is also generated. We demonstrate how detecting the difference between the DR-CARS signal and the amplifying signal from an abundant molecule's vibration can be used to enhance the sensitivity for the weaker signal. We further demonstrate that this approach even extends to applications where both signals are generated from different molecules, such that e.g. using the strong Raman signal of a solvent can enhance the weak Raman signal of a dilute solute.

Differential Imaging of Biological Structures with Doubly-resonant Coherent Anti-stokes Raman Scattering CARS

A combination of three single wavelength short-pulsed lasers is used to generate coherent anti-Stokes Raman scattering (CARS) and doubly-resonant CARS (DR-CARS). The difference between these signals provides enhanced sensitivity for otherwise difficult to detect coherent Raman signals, enabling imaging of weak Raman scatterers.

二重共鳴コヒーレント反ストークスラマン散乱（CARS）と生物学的構造の差イメージング

Coherent Raman imaging techniques have seen a dramatic increase in activity over the past decade due to their promise to enable label-free optical imaging ...

生物学

VSFG顕微鏡を使用したマルチモーダル、迅速、ハイパースペクトル化学分析

Multimodal Nonlinear Hyperspectral Chemical Imaging Using Line-Scanning Vibrational Sum-Frequency Generation Microscopy

Vibrational sum-frequency generation (VSFG), a second-order nonlinear optical signal, has traditionally been used to study molecules at interfaces as a spectroscopy technique with a spatial resolution of ~100 &#181;m. However, the spectroscopy is not sensitive to the heterogeneity of a sample. To study mesoscopically heterogeneous samples, we, along with others, pushed the resolution limit of VSFG spectroscopy down to ~1 &#181;m level and constructed the VSFG microscope. This imaging technique not only can resolve sample morphologies through imaging, but also record a broadband VSFG spectrum at every pixel of the images. Being a second-order nonlinear optical technique, its selection rule enables the visualization of non-centrosymmetric or chiral self-assembled structures commonly found in biology, materials science, and bioengineering, among others. In this article, the audience will be guided through an inverted transmission design that allows for imaging unfixed samples. This work also showcases that VSFG microscopy can resolve chemical-specific geometric information of individual self-assembled sheets by combining it with a neural network function solver. Lastly, the images obtained under brightfield, SHG, and VSFG configurations of various samples briefly discuss the unique information revealed by VSFG imaging.

著者スポットライト:メゾスコピック不均一自己組織化構造の研究におけるVSFG顕微鏡法の可能性の解明 

A multimodal, rapid hyperspectral imaging framework was developed to obtain broadband vibrational sum-frequency generation (VSFG) images, along with brightfield, second harmonic generation (SHG) imaging modalities. Due to the infrared frequency being resonant with molecular vibrations, microscopic structural and mesoscopic morphology knowledge is revealed of symmetry-allowed samples.

ライン走査型振動和周波数発生顕微鏡を用いたマルチモーダル非線形ハイパースペクトルケミカルイメージング

Vibrational sum-frequency generation (VSFG), a second-order nonlinear optical signal, has traditionally been used to study molecules at interfaces as a ...

Stereoisomers

On the basis of mirror symmetry, stereoisomers of an organic molecule can be further classified into diastereomers and enantiomers. Diastereomers are stereoisomers that are not mirror images of each other. Substituted alkenes, such as the cis and trans isomers of 2-butene, are diastereomers, as these molecules exhibit different spatial orientations of their constituent atoms, are not mirror images of each other,&#160;and do not interconvert. Here, the interconversion is suppressed due to restricted rotation around the &#960; bond. Another class of diastereomers &#8212; those without &#960; bonds &#8212; are molecules that have non-superposable spatial orientations and exhibit different configurations of their substituent groups at some, but not all, stereocenters. For example, cis-1,2-dimethylcyclohexane and trans-1,2-dimethylcyclohexane are diastereomers, as these molecules are not superposable and have a different configuration of the methyl and hydrogen groups at only one out of their two stereocenters.
Enantiomers are stereoisomers that are mirror images of each other. As only chiral molecules can have non-superposable mirror images, enantiomers are chiral molecules. For example, the chiral molecule 2-butanol and its mirror image are enantiomers, as these molecules exhibit non-superposable spatial orientations of their constituent atoms and are mirror images of each other. A chiral molecule and its mirror image are collectively referred to as an enantiomeric pair, or a pair of enantiomers. The enantiomer of a chiral molecule can be drawn by taking its mirror image from any position or&#160;exchanging the positions of two of the substituents at each stereocenter of the molecule.

Stereoisomers: Diastereomers and Enantiomers

立体異性体

On the basis of mirror symmetry, stereoisomers of an organic molecule can be further classified into diastereomers and enantiomers. Diastereomers are ...

有機化学

ユニット １

KEY TERMS AND CONCEPTS

<h3>Isomerism in Complexes</h3>
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis configuration, the two chloride ligands are adjacent to each other. The other isomer, the trans configuration, has the two chloride ligands directly across from one another.
<img alt="Image1" src="/files/ftp_upload/11459/11459_Image1.svg" style="text-align: center; height: 200px;" />
Figure 1. The cis and trans isomers of [Co(H2O)4Cl2]+ contain the same ligands attached to the same metal ion, but the spatial arrangement causes these two compounds to have very different properties.
Different geometric isomers of a substance are different chemical compounds. They exhibit different properties, even though they have the same formula. For example, the two isomers of [Co(NH3)4Cl2]NO3 differ in color; the cis form is violet, and the trans form is green. Furthermore, these isomers have different dipole moments, solubilities, and reactivities. As an example of how the arrangement in space can influence the molecular properties, consider the polarity of the two [Co(NH3)4Cl2]NO3 isomers. Remember that the polarity of a molecule or ion is determined by the bond dipoles (which are due to the difference in electronegativity of the bonding atoms) and their arrangement in space. In one isomer, cis chloride ligands cause more electron density on one side of the molecule than on the other, making it polar. For the trans isomer, each ligand is directly across from an identical ligand, so the bond dipoles cancel out, and the molecule is nonpolar.
Another important type of isomers are optical isomers, or enantiomers, in which two objects are exact mirror images of each other but cannot be lined up so that all parts match. This means that optical isomers are non-superposable mirror images. A classic example of this is a pair of hands, in which the right and left hand are mirror images of one another but cannot be superposed. Optical isomers are very important in organic and biochemistry because living systems often incorporate one specific optical isomer and not the other. Unlike geometric isomers, pairs of optical isomers have nearly identical properties (boiling point, polarity, solubility, etc.). Optical isomers differ only in the way they affect polarized light and how they react with other optical isomers. For coordination complexes, many coordination compounds such as [M(en)3]n+ [in which Mn+ is a central metal ion such as iron(III) or cobalt(II)] form enantiomers, as shown in Figure 2. These two isomers will react differently with other optical isomers. For example, DNA helices are optical isomers, and the form that occurs in nature (right-handed DNA) will bind to only one isomer of [M(en)3]n+ and not the other.
<img alt="Image2" src="/files/ftp_upload/11459/11459_Image_2.svg" style="text-align: center; height: 200px;" />
Figure 2. The complex [M(en)3]n+ (Mn+ = a metal ion, en = ethylenediamine) has a non-superposable mirror image.
The [Co(en)2Cl2]+ ion exhibits geometric isomerism (cis/trans), and its cis isomer exists as a pair of optical isomers (Figure 3).
<img alt="Image3" src="/files/ftp_upload/11459/11459_Image_3.svg" style="text-align: center; height: 200px;" />
Figure 3. Three isomeric forms of [Co(en)2Cl2]+ exist. The trans isomer, formed when the chlorines are positioned at a 180&#176; angle, has very different properties from the cis isomers. The mirror images of the cis isomer form a pair of optical isomers, which have identical behavior except when reacting with other enantiomers.
This text is adapted from <a href="https://openstax.org/books/chemistry-2e/pages/19-2-coordination-chemistry-of-transition-metals">Openstax, Chemistry 2e, Chapter 19.2 Coordination Chemistry of Transition Metals.</a>

Stereoisomerism: Geometric &amp; Optical Isomers

Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric ...

遷移金属と配位錯体

&sup1;H NMR Chemical Shift Equivalence: Enantiotopic and Diastereotopic Protons

Replacing each alpha-hydrogen in chloroethane by bromine (or a different functional group) yields a pair of enantiomers. Such protons are called prochiral or enantiotopic and are related by a mirror plane. Enantiotopic protons are chemically equivalent in an achiral environment. Because most proton NMR spectra are recorded using achiral solvents, enantiotopic hydrogens yield a single signal.
In chiral compounds such as 2-butanol, replacing the methylene hydrogens at C3 produces a pair of diastereomers. Such protons are called diastereotopic, and they perceive different environments in all conformations. They cannot be interchanged by rotation or reflection and have slightly different chemical shifts.

1H NMR Chemical Shift Equivalence: Enantiotopic and Diastereotopic Protons

¹H NMR化学シフト同等性:エナンチオトピックプロトンとジアステレオトピックプロトン

Replacing each alpha-hydrogen in chloroethane by bromine (or a different functional group) yields a pair of enantiomers. Such protons are called prochiral ...

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分子適合体とクラスターの空間的分離

レーザー駆動の超高速分子回転のダイレクトイメージング

化学イメージングのためのハイパースペクトル刺激ラマン散乱とコヒーレントアンチストークスラマン散乱顕微鏡の直接比較

二重共鳴コヒーレント反ストークスラマン散乱（CARS）と生物学的構造の差イメージング

ライン走査型振動和周波数発生顕微鏡を用いたマルチモーダル非線形ハイパースペクトルケミカルイメージング

ライン走査型振動和周波数発生顕微鏡を用いたマルチモーダル非線形ハイパースペクトルケミカルイメージング

ライン走査型振動和周波数発生顕微鏡を用いたマルチモーダル非線形ハイパースペクトルケミカルイメージング

立体異性体

立体異性体

¹H NMR化学シフト同等性:エナンチオトピックプロトンとジアステレオトピックプロトン