JP4252188B2 - Method for producing organic-inorganic composite having spiral structure with controlled spiral direction - Google Patents

Description

【００１１】
【化４】

式（Ｉ）中、ｎは５〜２０の整数であり、Ｘはハロゲン原子を表し、また、式（II）中、ｍは６〜２１の整数である。
【００１２】
本発明の有機無機複合体の製造方法の別の好ましい態様においては、金属酸化物はシリカである。
【００１３】
本発明は、さらに、以上のような方法により得られた有機無機複合体からキラル有機化合物を除去することを特徴とする中空糸状で一定の向きの螺旋状の金属酸化物の製造方法も提供する。本発明に従う中空糸で螺旋状の金属酸化物の製造方法においては、焼成によりキラル有機化合物を除去する。
【００１４】
本発明は、さらに別の視点として、上記の方法により製造され、内側がキラル有機化合物で、外側が金属酸化物から成り直径がナノメータのオーダーの二重円筒構造が螺旋状を呈していることを特徴とする有機無機複合体も提供する。さらに、本発明は上記の方法により製造される中空糸状で螺旋状の金属酸化物も提供する。
【００１５】
【発明の実施の形態】
金属のアルコキシドが触媒により重合し架橋しながら金属酸化物重合体を生成しゲル化することはよく知られている。本発明はこのようなゾルゲル反応をキラルな有機化合物のゲルを鋳型として該有機化合物上で起こし、ゾルゲル反応終了後、その鋳型の構造に応じて、一定の向きの螺旋構造の有機無機化合物および金属酸化物が得られるようにしたものである。
【００１６】
以下、本発明の有機無機複合体および金属酸化物の製造方法、およびそれらの構成する各要素に沿って本発明の特徴を詳述する。
製造方法
（１）：ゾルゲル反応溶液を含む混合液の調製：
本発明に従い螺旋構造の有機無機複合体および中空糸状金属酸化物を製造するには、先ず、キラル有機化合物とゾルゲル反応溶液とを混合して、それらを含有する均一な混合液を調製する。
ここで、本発明において用いるキラル有機化合物については後述する。一方、ゾルゲル反応溶液は、目的のゾルゲル反応系にもよるが、ゾルゲル反応が進行するような当初のゾルが形成されるように、少なくとも、金属酸化物（無機材料）の前駆体（金属酸化物の出発原料：金属アルコキシド、金属クロリド、金属ジケトネート等）、該金属酸化物の前駆体からゾルゲル反応により金属酸化物を生成するための触媒（酸、アルカリ、アミン等）、および水を含まなければならない。但し、これだけではゾルゲル反応系の溶解性が充分でない場合には、それらの前駆体、触媒、水を溶解し得るような溶媒を使用する。
さらに、必要により、混合を円滑にするため、有機低分子とゾルゲル反応溶液とを溶解し得る有機溶媒を用いる。
【００１７】
（２）ゲルの形成：
本発明の方法においては、このようにして得られた混合液中においてキラル有機化合物のゲルを形成させる。ここで、本発明に関連して用いるゲルという語は、一般的には、溶媒を完全に束縛して固まっている状態を指称するが、系を傾け軽い衝撃を与えると流動する程度にキラル有機化合物が互いに結合して繊維を形成している状態も含むものとする。このゲル形成の工程は以下のようにして行う。
キラル有機化合物のゲル形成の生じる温度が室温またはそれ以上である場合には、混合を円滑に行うためにキラル有機化合物とゾルゲル反応溶液との両者を溶解する有機溶媒を添加して調製した均一混合液から、溶解するために加えた有機溶媒を除去することによりゲルを形成させる。この有機溶媒の除去は、一般に、減圧乾燥により行う。また、キラル有機化合物が加熱に耐えられる場合は、上記の均一混合液を加熱した後、室温に冷却してゲルを形成する。さらに、ゲル形成温度が室温以下の場合には、キラル有機化合物とゾルゲル反応溶液とを室温で混合し、系を冷却することによりゲルを形成する。この工程中に、後述するようにキラル有機化合物のキラリティに応じて螺旋繊維状構造のキラル有機化合物のゲルが先行して形成され、金属酸化物のゾルゲル反応が一部進行する。
【００１８】
（３）金属酸化物の重合：
本発明に従い有機無機複合体を製造するには、次に、上記のようにゲルが形成した系を、該ゲルが壊れないような条件下に保持しながら、金属酸化物の重合を更に進行させる。すなわち、室温でゲル形成が生じたような系は室温下に、また、冷却によってゲルが形成したような系は、その冷却温度に、適当時間（一般に、数日間以上）保持すれば、金属酸化物のゾルゲル反応により加水分解、重縮合が進行し、金属酸化物の重合度が上がり溶液中に溶解し得なくなった金属酸化物が螺旋構造のキラル有機化合物のゲルの表面に付着、析出する。後に詳述するように、ゲル化能を有しキラリティが同じイオン性のキラル有機化合物とノニオン性のキラル有機化合物を組み合わせて使用することにより、静電力によりシリカ等の金属酸化物を付着させるのに適度のイオン性を有するキラル有機化合物のゲルが形成されるものと推測される。
【００１９】
（４）有機無機複合体および金属酸化物の調製：
以上のような工程の後、乾燥を行い、余分な溶媒を除去し、螺旋状のゲル構造のキラル有機化合物を残せば、一定の向きの螺旋構造を有するキラル有機化合物の表面に、金属酸化物前駆体由来の金属酸化物が付着した有機無機複合体が得られる。さらに、キラル有機化合物を除去すれば、螺旋状で中空糸状の金属酸化物となる。キラル有機化合物の除去は、溶媒を用いて溶出させることにより可能な場合もあるが、一般に、本発明の複合体における有機化合物は金属酸化物の外壁により強く保護され耐溶剤性を有するので、焼成により行うのが好ましい。
【００２０】
キラル有機化合物
本発明に従えば、有機溶媒および／または水の中でゲルを形成することができ、互いに同じキラリティを有するイオン性のキラル有機化合物とノニオン性（非イオン性）のキラル有機化合物の混合物を使用し、このキラル有機化合物から形成されたゲルを鋳型とし、これにシリカ等の金属酸化物を付着させて、螺旋構造を有する有機無機複合体および金属酸化物を得ることができる。
【００２１】
ここで、本発明において用いられるキラル有機化合物とは、キラリティを有する有機化合物、すなわち、よく知られているように、不斉原子を有するかまたは分子全体が不斉であり（より正確に表現すれば回映対称をもたず）光学活性対掌体が存在する有機化合物である。本発明においては、このようなキラル有機化合物のうち、ゲルを形成し易いような分子構造、すなわち、一般的には、分子同士が一次元的に重なり合って結合し得るような分子構造を有するもの（三次元的に結合するものは結晶化してしまう）から、互いに同じキラリティのイオン性キラル有機化合物とノニオン性キラル有機化合物（すなわち、Ｒ−対掌体同士またはＳ−対掌体同士）を組み合わせて使用する。
【００２２】
本発明において用いられるイオン性キラル有機化合物およびノニオン性キラル有機化合物として特に好適な例は、それぞれ、前述の式（Ｉ）および（II）で表されるジアミノシクロヘキサン誘導体である。その他の好ましい例は、図１に示している。（なお、本明細書および図面に示す化学構造式においては慣用的な表現法に従い、炭素原子および水素原子を省略している。）
【００２３】
式（I）、（II）、（III）、（IV）、（V）、（VI）および（VII）で表される化合物は不斉原子（不斉炭素：式中＊を付けている）を有し、ゲル化能を示す化合物の例である。イオン性キラル有機化合物およびノニオン性キラル化合物として、それぞれ、（Ｉ）と（II）、（III）と（VI）、（IV）と（VII）、（Ｖ）と（VIII）を組み合わせて使用する。これから理解されるように、良好なゲルを形成するためには、イオン性キラル有機化合物とノニオン性キラル有機化合物は、イオン性化合物の電荷部位とノニオン性化合物の対応する部位を除いては、互いに、分子全体として同一または類似の構造を有するものを使用するのが望ましい。例えば、（Ｉ）と（II）の場合、アルキル鎖部分は実質的に長さが等しいか近似しており、ｎ＝ｍ〜ｍ±３程度になるようにすることが望ましい。
【００２４】
また、イオン性のキラル有機化合物としてはカチオン性のもののみを例示しているが、ゲルに付着する金属酸化物（金属酸化物前駆体）の等電点に応じてカチオン性またはアニオン性のキラル有機化合物を使用する。例えば、シリカの等電点はｐＨが約２であり、ゲルへの付着が行われるｐＨ条件下では一般に負の電荷を有するものとして挙動するので、これが付着するようにカチオン性のキラル有機化合物を使用する。しかし、金属酸化物としてアルミナを使用する場合には、その等電点は９であるので、これをキラル化合物のゲルから成る鋳型に付着させるような場合はアニオン性のキラル有機化合物を用いることも可能である。
【００２５】
本発明の特徴は、以上のようなゲル化能を有し且つ同じキラリティを有するイオン性およびノニオン性のキラル化合物の両方を組み合わせて使用することによって、これらのキラル有機化合物のゲルを鋳型としてそのキラリティに応じて螺旋の向きが制御された、すなわち、右巻きまたは左巻きのいずれか一方の向きの螺旋構造を有する有機無機複合体および金属酸化物を製造できることにある。
【００２６】
上述したようなゲル化能を有するイオン性キラル有機化合物またはノニオン性キラル有機化合物はキラリティを有するので、それぞれ単独でも鋳型となる螺旋構造のゲルを形成すると考えられる。しかしながら、後の実施例にも示すように、イオン性キラル有機化合物またはノニオン性キラル有機化合物のいずれか一方のみを使用したりいずれか一方が多すぎる（少なすぎる）場合には、単純な円筒状または粒子状のものしか形成せず、螺旋状の構造体は得られない。これは、イオン性のキラル有機化合物のみを使用したり多すぎる場合には、それから形成されたゲルの表面とシリカ等の金属酸化物（金属酸化物前駆体）との間の静電的相互作用が強すぎるために、シリカ等の金属酸化物が不規則に多量に付着してしまいキラリティが発現されないためと考えられる。また、ノニオン性キラル有機化合物のみを使用したり多すぎる場合には、該キラル有機化合物由来のゲルにシリカ等の金属酸化物が付着しないのであろう。
【００２７】
これに対して、本発明においては、同じキラリティを有し分子構造の酷似したイオン性およびノニオン性のキラルなゲル化能を有する有機化合物が共同して、それらのキラリティに応じた螺旋構造を呈し適度な大きさの表面電荷を有するゲルを形成し、これを鋳型としてその表面にシリカ等の金属酸化物が付着し、そのキラリティ（螺旋の向き）を保持した構造体が得られるものと推測される。螺旋状の構造体を得るのに用いられるカチオン性キラル有機化合物とノニオン性キラル有機化合物の比率は、それらの種類にもよるが、一般的には、いずれか一方を少なくとも１０〜１５重量％使用することが必要である。ゲル状態のキラリティは、例えば、ＣＤ（円二色性）スペクトルを測定することにより知ることができる。
【００２８】
金属酸化物（無機材料）
ゾルゲル反応の進行過程における金属酸化物の表面電荷は金属の種類と溶液のｐＨによって変化するので、キラル有機化合物のゲルの表面に静電的に付着しやすいように金属の種類とｐＨを選ぶ必要があるが、本発明において用いられ得る金属酸化物の種類に基本的に制限はない。例えば、シリカ、アルミナ、ボレイトの他、チタニア、ジルコニア、ヘマタイト等の遷移金属酸化物が挙げられる。
金属酸化物を与えるゾルゲル反応の前駆体（出発物質）としてはこれらの金属のアルコキシドおよびクロリド、ジケトネート等が挙げられる。具体的にはシリカでは、テトラエトキシシラン、メチルトリエトキシシラン、テトラクロロシラン、アルミナではアルミニウムトリ−ｓｅｃ−ブトキシド、アルミニウム（III）２，４−ペンタンジオネート、ボレイトではトリメトキシボラン、チタニアではチタンエトキサイド、ジルコニアではジルコニウムテトラ−ｎ−ブトキサイド等である。
【００２９】
ゾルゲル反応溶液
ゲル状態の繊維状で螺旋状のキラル有機化合物の表面への金属酸化物の付着を効率的に進めるために、溶液の組成は金属酸化物重合体が低重合度のうちに析出する組成が望ましい。すなわち、アルコールやＴＨＦ等の金属酸化物に対する溶解度の大きな有機溶媒を多く含まない組成でなければならない。
また金属酸化物の表面電荷はその金属の電気陰性度と溶液のｐＨによって決まるので、鋳型分子を効率的に付着する符号になるｐＨを金属の種類に応じて変化する必要がある。例えば、カチオン性キラル化合物とノニオン性キラル化合物を用いた場合のゲルはカチオン性となり、これに対して、酢酸主体のゾルゲル溶液中（ｐＨ≒５）でのシリカ表面はアニオンと考えられ、鋳型分子であるゲルの繊維構造表面に金属酸化物が静電引力的に付着し成長すると考えられる。
金属酸化物（無機材料）の含有量がキラル有機化合物に比べ多すぎると乾燥時の金属酸化物の収縮によって有機化合物が圧縮され中空状構造をとりにくくなるし、金属酸化物同士の融合が生じ独立した繊維状構造にならないので望ましくなく、また少なすぎると金属酸化物の中空状構造が脆弱になる。有機無機複合体に対し金属酸化物の量は重量比で一般に２０〜９０％である。
【００３０】
有機無機複合体と金属酸化物の特性
本発明の有機無機複合体は、繊維状のキラル有機化合物の表面に金属酸化物が付着した構造、すなわち、内側がキラル有機化合物であり、外側が金属酸化物である二重円筒状構造から成る（すなわち、円柱状のキラル有機化合物の外側に金属酸化物が存在する円環状の横断面を呈する）。該円筒の直径（最外径）はナノメータのオーダー、すなわち、一般的には数ｎｍから数百ｎｍ（例えば、約３０〜２００ｎｍ）である。そして、内側のキラル有機化合物は、そのキラリティに応じた向きの鋳型ゲルのヘリックス構造（螺旋構造）を保持しているので、有機無機複合体としても全体的に螺旋状を呈する。
【００３１】
このような有機無機複合体から既述のようにキラル有機化合物を除去すると、キラル化合物の大きさに対応する内径を有する円筒状構造、すなわち、内径がナノメータのオーダー（例えば、約１０〜１００ｎｍ）の中空糸状で且つ螺旋状の金属酸化物構造体が得られる。
【００３２】
本発明の有機無機複合体は、中空糸状で螺旋状の金属酸化物（例えば、シリカ）の前駆体として有用であるが、それ自身も各種の用途が期待される。例えば、本発明の有機無機複合体は、中空糸内部に触媒活性のあるキラル有機化合物を残すことにより、外側の螺旋状金属酸化物の形態（螺旋方向等）に親和性を持つ分子のみを触媒変性させることが可能である。
【００３３】
他方、本発明の中空糸状で螺旋状の金属酸化物は、中空糸の外表面、内表面のいずれをも利用して触媒、吸着剤等への応用が可能であり、特に、一定の向きの螺旋構造を有するので、キラリティの関与する反応に対する触媒または触媒支持体としての利用が期待される。その他、本発明の中空糸状金属酸化物は、繊維状態であるため嵩高く、これに加えて中空構造のため断熱効果が高く、金属酸化物の耐熱性が高いことから断熱材としても優れている。
【００３４】
【実施例】
以下に本発明の特徴をさらに明らかにするため実施例を示すが、本発明はこの実施例によって制限されるものではない。
実施例１：キラル有機化合物の合成
有機無機複合体および金属酸化物を調製するための鋳型となるゲル化性キラル有機化合物として、図２に示す反応スキームに従って１〜４のジアミノシクロヘキサン誘導体を合成した。２および４は既述の式（Ｉ）においてｎ＝１０に相当するカチオン性キラル有機化合物であり、１および３は既述の式（II）においてｍ＝１１に相当するノニオン性キラル化合物である。
【００３５】
（１）化合物７および８：トランス（１Ｒ，２Ｒ−または１Ｓ，2Ｓ−）−ジアミノシクロヘキサン（１．０ｇ、８．５７ｍｍｏｌ）および１１−ブロモウンデカン酸（７．６６ｇ、３５．０１ｍｍｏｌ）を窒素雰囲気下、３０ｍｌのＴＨＦに溶かした。得られた溶液を室温に保持した。次いで、ジシクロヘキシルカルボジイミド（７．２ｇ、８．５７ｍｍｏｌ）およびジメチルアミノピリジン（０．４０ｇ、０．８５７ｍｍｏｌ）を添加し、混合液を室温下に４８時間攪拌した。反応混合物をろ過し、酸性水溶液および塩基性水溶液（５０ｍｌ）で抽出した。蒸発器で有機相を蒸発させ、残留物をＴＨＦ／ヘキサン（１：２ｖ／ｖ）を溶出液とするシリカゲルカラムで精製して、化合物７および８（収率はそれぞれ５７％および６０％）を得た。¹Ｈ−ＮＭＲ：δＨ（３００ＭＨｚ）：６．１５（２Ｈ，ｓ）、３．７５（２Ｈ，ｓ）、３．３７（４Ｈ，ｔ，Ｊ＝６．０）、２．１７−１．２６（４Ｈ，ｍ）。ＩＲ：３３５０、２９８０、１６０３、１１１６、１０４７ｃｍ^{− 1}。
【００３６】
（２）化合物１および３：トランス（１Ｒ，２Ｒ−または１Ｓ，２Ｓ）−ジアミノシクロヘキサン（１．０ｇ、８．５７ｍｍｏｌ）、塩化ラウロイル（７．６６ｇ、３５．０２ｍｍｏｌ）およびトリエチルアミン（３．５４ｇ、３５．０１２ｍｍｏｌ）をＴＨＦ（３０ｍｌ）に溶かし、４８時間還流した。得られた溶液を冷却し、ろ過した後、真空蒸発して溶媒を除去した。残留物を酢酸エチル／ヘキサン（１：２ｖ／ｖ）を溶出液とするシリカゲルで精製して、所望の化合物１および３を得た。収率は、それぞれ、５０％および５５％。元素分析（Ｃ₃₀Ｈ₅₈Ｎ₂Ｏ₂として）：計算値（Ｃ，７５．２６；Ｈ，１２．２１；Ｎ，５．８５；Ｏ，６．６８％）、実測値（Ｃ，７５．０、Ｈ，１２．５；Ｎ，５．７％）。¹Ｈ−ＮＭＲ：δＨ（３００ＭＨｚ）：６．１５（２Ｈ，ｓ）、３．７５（２Ｈ，ｓ）、３．３７（４Ｈ，ｔ，Ｊ＝６．０）、２．１７−１．２５（４４Ｈ，ｍ）、０．８７（６Ｈ，ｔ，Ｊ＝５．７）。ＭＳ（ＳＩＭＳ）＝４７８[Ｍ＋Ｈ]⁺。ＩＲ：３３５０、２９８０、１７２２、１６０３、１１１６、１０４７ｃｍ^-1。
【００３７】
（３）化合物２および４：化合物７または８、およびトリエチルアミンをＴＨＦ／ＤＭＦ（９：１ｖ／ｖ）に溶かし、得られた混合物を室温下に２４時間攪拌した。真空蒸発により溶媒を除去し、化合物１および３の場合と同様に精製することにより、化合物２および４を得た。元素分析（Ｃ₃₄Ｈ₇₀Ｂｒ₂Ｎ₄Ｏ₂として）：計算値（Ｃ，５６．１９；Ｈ，９．７１；Ｂｒ，２１．９９；Ｎ，７．７１；Ｏ，４．４０％）実測値（Ｃ，５６．５、Ｈ，９．２；Ｎ，８．０％）。¹Ｈ−ＮＭＲ：δ（３００ＭＨｚ）：７．２６（２Ｈ，ｓ）、４．０１−３．４５（２０Ｈ，ｍ）、２．４０（４Ｈ，ｔ，Ｊ＝６．０）、２．１７−１．２５（３８Ｈ，ｍ）、０．８７（６Ｈ，ｔ，Ｊ＝５．７）。ＭＳ（ＳＩＭＳ）＝７２５[Ｍ＋Ｈ]⁺。ＩＲ：３３５０、２９８０、１７２２、１６０３、１１１６、１０４７ｃｍ^-1。
【００３８】
実施例２：キラル有機化合物のゲル化能試験およびゲルの構造分析
実施例１で合成した化合物１〜４を用い、各種の溶媒に対するゲル化能を調べた。ゲル化能試験は次のように行った：化合物１〜４（それぞれ３ｍｇ）をキャップ付試験管内で溶媒と混合して化合物１〜４のぞれぞれの濃度が５重量％となるようにし、固形分が溶解するまで加熱した。得られた溶液を室温に冷却し、１時間放置してゲルの形成を観察した。その結果を表１に示す。
【００３９】
【表１】

【００４０】
以上の結果から、化合物１〜４は、各種の溶媒に対してゲル化能を有し、特にノニオン性化合物１および３は表に示す全ての溶媒に対して優れたゲル化剤として機能することが確かめられた。
次に、カチオン性キラル有機化合物とノニオン性キラル有機化合物を併用して得られるゲルの構造を調べるためにＣＤ（円二色性）スペクトルの測定を行った。図３は、ゲル化剤として化合物１＋化合物２または化合物３＋化合物４の混合物（５０／５０重量％）を使用した場合のゲル状態アセトニトリル溶液のＣＤスペクトルチャートである。Ｒ−対掌体混合物（化合物１＋化合物２）のＣＤスペクトルは第一コットン効果が負のサインを示しており、左巻き（反時計方向）の螺旋が形成していることが示唆された。一方、Ｓ−対掌体混合物（化合物３＋化合物４）のＣＤスペクトルは、第一コットン効果が正のサインを示しており、右巻き（時計方向）の螺旋を形成していることが示唆された。
【００４１】
このことは、溶媒（アセトニトリル）を除去したキセロゲルの顕微鏡観察によっても確認された。図４は、上述のゲル状態のアセトニトリル溶液をゾル−ゲル転移温度（化合物１＋２については３９．５〜４０．２℃、化合物３＋４については３５．２〜３７．０℃）以下で凍結乾燥することによりアセトニトリルを除去して得られたキセロゲルの走査型電子顕微鏡写真である。いずれも２０〜６０ｎｍの幅の螺旋繊維状の凝集体が形成しており、Ｒ−対掌体混合物（化合物１＋２）を使用した場合は（図４のＡ）繊維の向きは左巻きであり、また、Ｓ−対掌体混合物（化合物３＋４）を用いた場合（図４のＢ）は繊維の向きは右巻きであることが認められる。
【００４２】
実施例３：有機無機複合体および金属酸化物の製造
実施例２に示されるように、化合物１＋化合物２または化合物３＋化合物４を併用することにより、溶媒中で一定の向きの螺旋状のゲルが形成されることが確認されたので、次に、このような螺旋構造のゲルを鋳型とするゾル−ゲル反応による螺旋構造の有機無機複合体および金属酸化物の製造を試みた。
【００４３】
先ず、アセトニトリル（８０．０ｍｇ）、ＴＥＯＳ（テトラエトキシシラン）（８．０ｍｇ）、水（４．０ｍｇ）、および触媒としてベンジルアミン（４．０ｍｇ）から成るゾルゲル反応溶液に、化合物１＋化合物２または化合物３＋化合物４の混合物（それぞれ、混合物の全重量３．０ｍｇとし、化合物１／化合物２または化合物３／化合物４の比率を変えた）を添加して均一な混合液を調製した。混合の初期から白濁しゲル化が見られた。これを室温下に７日間放置した。
【００４４】
次いで、これを室温で開放した条件で２日間乾燥後、真空下６０℃で５時間乾燥して有機無機複合体を得た。図５に、化合物１／化合物２が５０／５０（重量％）の場合のこの複合体のＳＥＭ（走査電子顕微鏡）写真を示す。化合物３／化合物４が５０／５０（重量％）の場合の複合体についても同様のＳＥＭ写真が得られた。これらの写真から二重円筒構造で螺旋状を呈し、円筒の直径（最外径）は、約５０〜２００ｎｍであることが分った。また、化合物１＋化合物２を用いた場合は螺旋は左巻きであり、化合物３＋化合物４を用いた場合は右巻きであり、ゲル状態のキラリティを反映していることが理解された。
【００４５】
さらに、窒素気流下２００℃で２時間乾燥し、次いで５００℃で２時間、最後に空気気流下で５００℃、４時間焼成し金属酸化物（シリカ）を得た。得られたシリカの構造をＴＥＭ（透過型電子顕微鏡）で観察した。その結果を表２に示す。
【００４６】
【表２】

【００４７】
表２に示されるように、カチオン性の化合物２または化合物４が３０〜８５重量％の場合に螺旋構造のシリカが形成され、１００％であったり少なすぎると従来から見られるような単純な円筒形（非螺旋）のシリカしか得られない。さらに、ゲル構造のキラリティに応じて化合物１と化合物２を用いた場合は左巻きの螺旋構造、化合物３と化合物４を用いた場合は右巻きの螺旋構造が形成されており、ゲル構造がシリカに忠実に転写されていることが理解される。ＴＥＭの観察結果から得られるシリカの外径は１００〜１５０ｎｍ、内径２０〜６０ｎｍ程度である。図６は、代表例として化合物１／化合物２（図６のＡ）または化合物３／化合物４（図６のＢ）が５０／５０（重量）の場合のＴＥＭ写真を示す。
【図面の簡単な説明】
【図１】本発明において用いられるのに好適なカチオン性キラル有機化合物およびノニオン性キラル化合物を例示する。
【図２】本発明において用いられるのに好適なキラル有機化合物であるジアミノシクロヘキサン誘導体を合成する反応スキームを示す。
【図３】本発明において鋳型となる有機ゲルのＣＤスペクトルの例を示す。
【図４】本発明において鋳型となる有機ゲル（キセロゲル）の結晶構造を示す透過型電子顕微鏡写真である。
【図５】本発明の有機無機複合体の１例の結晶構造を示す透過型電子顕微鏡写真である。
【図６】本発明の金属酸化物の１例の結晶構造を示す透過型電子顕微鏡写真である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic-inorganic composite and a metal oxide that can be used as various functional materials such as a catalyst. In particular, the present invention relates to a novel structure in which a spiral structure is produced by controlling the direction of the spiral. Regarding the method.
[0002]
[Prior art]
Inorganic porous materials are frequently used as catalysts, supporting materials or adsorbing materials, chromatographic materials, and the like because of the selectivity of molecules due to the size of the surface area and the pore diameter, and further improvements have been attempted. For the preparation of these porous materials, a method using some template is used, and for the preparation of microporous materials such as zeolite, organic low molecular weight compounds, surfactants and block copolymers for mesoporous materials, and macroporous materials, There are examples using each emulsion. Among porous materials, fibrous or hollow inorganic materials are synthesized using tartaric acid molecular aggregates, carbon fibers, and carbon nanotubes as templates. On the other hand, in the research on so-called Biomineralization that utilizes the function of biological material, attempts have been made to create various forms of inorganic materials using biological material as a template. Cylindrical organic inorganic using self-organized lipid tubes Complexes and the like have also been obtained. However, there has been no example of preparing an organic-inorganic composite material or an inorganic material using an organic low-molecular gel as a template. Materials reflecting these gel structures exhibiting various forms are expected to have various applications as materials with anisotropy based on unique forms. For example, it is expected that a new type of functional organic gel-inorganic composite material and porous inorganic material can be obtained by using a fibrous gel, that is, a linear or helical elongated filamentous gel as a template. However, there is no technology that embodies such materials.
[0003]
The present inventors previously used a fibrous organic low-molecular gel as a template, and on this gel, a polymer of the metal oxide is produced by a sol-gel reaction from a sol of a metal oxide such as silica. Further, a technique capable of obtaining an organic-inorganic composite reflecting the structure of an organic low-molecular gel and a hollow fiber metal oxide from which an organic substance has been removed has been disclosed (Japanese Patent Laid-Open No. 11-108922). Particularly preferred as a small organic molecule as a template is a cholesterol derivative having an azobenzene moiety, for example, by using a cholesterol derivative having an azobenzene moiety and a cationic moiety (ammonium salt) at one end. Hollow fiber silica is obtained.
[0004]
In order to improve the technique disclosed in Japanese Patent Application No. 11-108922, the present inventors have previously retained a metal formed from a cholesterol derivative having an azacrown ring substituted with a specific functional group. It has also been clarified that a structure in which a metal different from the metal is fixed to a helical metal oxide is obtained using a gel exhibiting a helical structure in a certain direction as a template (Japanese Patent Application No. 11-319070). ).
[0005]
The techniques disclosed in the above-mentioned patent applications are few techniques that can obtain a helical structure useful as a catalyst or the like, but all use a relatively expensive special organic compound.
[0006]
An object of the present invention is to provide a more general new technique capable of producing a microstructure of a helical structure (helix structure) having a certain orientation useful as a catalyst or the like for a reaction involving chirality. It is in.
[0007]
[Means for Solving the Problems]
The present inventor uses a ionic and nonionic chiral organic compound having gelling ability and the same chirality in combination, and a structure in which the direction of the spiral is controlled by using a gel of these chiral organic compounds as a template And the present invention was derived.
[0008]
Thus, the present invention
(1) a. An ionic chiral organic compound capable of forming a gel in an organic solvent and / or water, and a nonionic chiral compound having the same chirality as the ionic chiral organic compound and capable of forming a gel in an organic solvent and / or water Mixtures with organic compounds,
B. A metal oxide precursor, a catalyst for forming a metal oxide polymer from the metal oxide precursor by a sol-gel reaction, water, and, if necessary, the metal oxide precursor, catalyst, and water are dissolved. A sol-gel reaction solution comprising the solvent obtained, and
C. An organic solvent capable of dissolving the organic chiral compound and the sol-gel reaction solution if necessary,
A step of preparing a homogeneous mixed solution containing
(2) a. Removing the organic solvent from the homogeneous mixture,
B. The homogeneous mixture is heated and then cooled, or
C. Cooling the homogeneous mixture;
A step of forming a gel of the organic chiral compound, and
(3) holding the gel-formed system and advancing the polymerization of the metal oxide;
The present invention provides a method for producing an organic-inorganic composite in which a metal oxide is attached to the surface of a chiral organic compound having a spiral structure in a certain direction.
[0009]
In a preferred embodiment of the method for producing an organic-inorganic composite of the present invention, the ionic chiral organic compound is selected from diaminocyclohexane derivatives represented by formula (I), and the nonionic chiral organic compound is represented by formula (II). Selected from diaminocyclohexane derivatives.
[0010]
[Chemical 3]

[0011]
[Formula 4]

In formula (I), n is an integer of 5 to 20, X represents a halogen atom, and in formula (II), m is an integer of 6 to 21.
[0012]
In another preferred embodiment of the method for producing an organic-inorganic composite of the present invention, the metal oxide is silica.
[0013]
The present invention further provides a method for producing a hollow fiber-like spiral metal oxide having a certain orientation, wherein the chiral organic compound is removed from the organic-inorganic composite obtained by the above method. . In the method for producing a hollow fiber helical metal oxide according to the present invention, the chiral organic compound is removed by calcination.
[0014]
According to another aspect of the present invention, a double cylindrical structure manufactured by the above-described method and having a chiral organic compound on the inside and a metal oxide on the outside and having a diameter of the order of nanometers is spiral. A featured organic-inorganic composite is also provided. Furthermore, the present invention also provides a hollow fiber-like spiral metal oxide produced by the above method.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
It is well known that metal alkoxides are polymerized and cross-linked by a catalyst to form a metal oxide polymer and gel. The present invention causes such a sol-gel reaction to occur on the organic compound using a chiral organic compound gel as a template, and after completion of the sol-gel reaction, depending on the structure of the template, the organic inorganic compound and metal having a spiral structure in a certain direction An oxide is obtained.
[0016]
Hereinafter, the characteristics of the present invention will be described in detail along the method for producing the organic-inorganic composite and the metal oxide of the present invention, and the constituent elements thereof.
Production method
(1): Preparation of mixed solution containing sol-gel reaction solution:
In order to produce an organic-inorganic composite having a spiral structure and a hollow fiber metal oxide according to the present invention, first, a chiral organic compound and a sol-gel reaction solution are mixed to prepare a uniform mixed solution containing them.
Here, the chiral organic compound used in the present invention will be described later. On the other hand, the sol-gel reaction solution is at least a metal oxide (inorganic material) precursor (metal oxide) so that an initial sol in which the sol-gel reaction proceeds is formed, depending on the target sol-gel reaction system. Starting materials: metal alkoxides, metal chlorides, metal diketonates, etc.), catalysts (acids, alkalis, amines, etc.) for producing metal oxides from precursors of the metal oxides by sol-gel reaction, and water Don't be. However, when the solubility of the sol-gel reaction system is not sufficient by this alone, a solvent capable of dissolving the precursor, catalyst, and water is used.
Further, if necessary, an organic solvent capable of dissolving the organic low molecule and the sol-gel reaction solution is used in order to facilitate mixing.
[0017]
(2) Gel formation:
In the method of the present invention, a gel of a chiral organic compound is formed in the mixed solution thus obtained. Here, the term gel used in connection with the present invention generally refers to a state in which the solvent is completely constrained and solidified, but is chiral organic enough to flow when the system is tilted and given a light impact. The state in which the compound is bonded to each other to form a fiber is also included. This gel forming step is performed as follows.
Homogeneous mixing prepared by adding an organic solvent that dissolves both the chiral organic compound and the sol-gel reaction solution for smooth mixing when the temperature at which the gel formation of the chiral organic compound is at room temperature or higher The gel is formed by removing the organic solvent added for dissolution from the liquid. This organic solvent is generally removed by drying under reduced pressure. Moreover, when a chiral organic compound can endure a heating, after heating said homogeneous liquid mixture, it cools to room temperature and forms a gel. Furthermore, when the gel formation temperature is room temperature or lower, the chiral organic compound and the sol-gel reaction solution are mixed at room temperature, and the system is cooled to form a gel. During this process, as described later, a gel of a chiral organic compound having a helical fibrous structure is formed in advance according to the chirality of the chiral organic compound, and a sol-gel reaction of the metal oxide partially proceeds.
[0018]
(3) Polymerization of metal oxide:
In order to produce the organic-inorganic composite according to the present invention, the polymerization of the metal oxide is further advanced while maintaining the system in which the gel is formed as described above under the condition that the gel is not broken. . That is, a system in which gel formation has occurred at room temperature, and a system in which gel has been formed by cooling will be subjected to metal oxidation if kept at the cooling temperature for an appropriate time (generally several days or more). Hydrolysis and polycondensation proceed due to the sol-gel reaction of the product, the degree of polymerization of the metal oxide increases, and the metal oxide that cannot be dissolved in the solution adheres to and deposits on the surface of the gel of the chiral organic compound having a helical structure. As described in detail later, by using a combination of an ionic chiral organic compound having gelling ability and the same chirality and a nonionic chiral organic compound, a metal oxide such as silica is attached by electrostatic force. It is presumed that a gel of a chiral organic compound having moderate ionicity is formed.
[0019]
(4) Preparation of organic-inorganic composite and metal oxide:
After the above steps, drying is performed to remove excess solvent, leaving a chiral organic compound having a helical gel structure, and a metal oxide is formed on the surface of the chiral organic compound having a helical structure in a certain direction. An organic-inorganic composite having a precursor-derived metal oxide attached thereto is obtained. Furthermore, if the chiral organic compound is removed, a spiral and hollow fiber metal oxide is obtained. Although removal of the chiral organic compound may be possible by elution with a solvent, in general, the organic compound in the composite of the present invention is strongly protected by the outer wall of the metal oxide and has solvent resistance, and thus is fired. It is preferable to carry out.
[0020]
Chiral organic compounds
According to the present invention, a gel can be formed in an organic solvent and / or water, and a mixture of an ionic chiral organic compound and a nonionic (nonionic) chiral organic compound having the same chirality as each other is used. Then, a gel formed from this chiral organic compound is used as a template, and a metal oxide such as silica is attached thereto, whereby an organic-inorganic composite and a metal oxide having a helical structure can be obtained.
[0021]
Here, the chiral organic compound used in the present invention is an organic compound having chirality, that is, as is well known, it has an asymmetric atom or the whole molecule is asymmetric (more accurately expressed). It is an organic compound in which an optically active enantiomer exists. In the present invention, among these chiral organic compounds, those having a molecular structure that is easy to form a gel, that is, those having a molecular structure that allows molecules to overlap and bond one-dimensionally in general. (Those that bond three-dimensionally will crystallize), so combine ionic chiral organic compounds and nonionic chiral organic compounds (that is, R-enantiomers or S-enantiomers) of the same chirality. To use.
[0022]
Particularly suitable examples of the ionic chiral organic compound and the nonionic chiral organic compound used in the present invention are diaminocyclohexane derivatives represented by the aforementioned formulas (I) and (II), respectively. Another preferred example is shown in FIG. (In the chemical structural formulas shown in the present specification and drawings, carbon atoms and hydrogen atoms are omitted in accordance with conventional expressions.)
[0023]
Compounds represented by the formulas (I), (II), (III), (IV), (V), (VI) and (VII) are asymmetric atoms (asymmetric carbon: marked with * in the formula) It is an example of a compound having a gelation ability. (I) and (II), (III) and (VI), (IV) and (VII), (V) and (VIII) are used in combination as an ionic chiral organic compound and a nonionic chiral compound, respectively. . As will be understood, in order to form a good gel, the ionic chiral organic compound and the nonionic chiral organic compound are separated from each other except for the charge site of the ionic compound and the corresponding site of the nonionic compound. It is desirable to use those having the same or similar structure as the whole molecule. For example, in the case of (I) and (II), the alkyl chain portions are substantially equal in length or approximate to each other, and it is desirable that n = m to m ± 3.
[0024]
In addition, only cationic compounds are exemplified as ionic chiral organic compounds, but cationic or anionic chiral depending on the isoelectric point of the metal oxide (metal oxide precursor) attached to the gel. Use organic compounds. For example, the isoelectric point of silica has a pH of about 2, and generally behaves as having a negative charge under pH conditions where attachment to a gel is performed. use. However, when alumina is used as the metal oxide, its isoelectric point is 9, so an anionic chiral organic compound may be used when it is attached to a template comprising a gel of a chiral compound. Is possible.
[0025]
The feature of the present invention is that by using a combination of both ionic and nonionic chiral compounds having the above-mentioned gelation ability and the same chirality, the gel of these chiral organic compounds is used as a template. It is to be able to manufacture an organic-inorganic composite and a metal oxide having a spiral structure controlled according to chirality, that is, having a spiral structure in either a right-handed or left-handed direction.
[0026]
Since the ionic chiral organic compound or nonionic chiral organic compound having the gelation ability as described above has chirality, it is considered that each of them forms a gel having a helical structure as a template. However, as shown in the following examples, when only one of the ionic chiral organic compound and the nonionic chiral organic compound is used, or when either one is too much (too little), a simple cylindrical shape is used. Alternatively, only particles are formed, and a spiral structure cannot be obtained. This is because when only ionic chiral organic compounds are used or too much, electrostatic interaction between the surface of the gel formed from it and a metal oxide such as silica (metal oxide precursor) This is considered to be because the metal oxide such as silica is irregularly deposited in a large amount and thus no chirality is exhibited. Moreover, when only a nonionic chiral organic compound is used or too much, metal oxides, such as a silica, will not adhere to the gel derived from this chiral organic compound.
[0027]
On the other hand, in the present invention, organic compounds having the same chirality and having similar molecular structure and ionic and nonionic chiral gelling ability jointly exhibit a helical structure corresponding to the chirality. It is presumed that a gel having a moderately large surface charge is formed, and using this as a template, a metal oxide such as silica adheres to the surface, and a structure that retains its chirality (spiral direction) is obtained. The The ratio of the cationic chiral organic compound and the nonionic chiral organic compound used to obtain the helical structure depends on the type of the compound, but generally at least 10 to 15% by weight of either one is used. It is necessary to. The chirality in the gel state can be known, for example, by measuring a CD (circular dichroism) spectrum.
[0028]
Metal oxide (inorganic material)
Since the surface charge of the metal oxide during the progress of the sol-gel reaction varies depending on the type of metal and the pH of the solution, it is necessary to select the type and pH of the metal so that it easily adheres to the surface of the chiral organic compound gel. However, there is basically no limitation on the type of metal oxide that can be used in the present invention. Examples thereof include transition metal oxides such as titania, zirconia, and hematite in addition to silica, alumina, and borate.
Examples of the precursor (starting material) of the sol-gel reaction that gives a metal oxide include alkoxides and chlorides of these metals, diketonates, and the like. Specifically, silica is tetraethoxysilane, methyltriethoxysilane, tetrachlorosilane, alumina is aluminum tri-sec-butoxide, aluminum (III) 2,4-pentanedionate, borate is trimethoxyborane, and titania is titanium ethoxy. For side and zirconia, zirconium tetra-n-butoxide is used.
[0029]
Sol-gel reaction solution
In order to efficiently promote the adhesion of the metal oxide to the surface of the gel-like fibrous and spiral chiral organic compound, the composition of the solution is preferably a composition in which the metal oxide polymer precipitates within a low degree of polymerization. . That is, the composition should not contain a large amount of an organic solvent having high solubility in metal oxides such as alcohol and THF.
Further, since the surface charge of the metal oxide is determined by the electronegativity of the metal and the pH of the solution, it is necessary to change the pH, which is a sign for efficiently attaching the template molecule, according to the type of metal. For example, when a cationic chiral compound and a nonionic chiral compound are used, the gel becomes cationic. On the other hand, the silica surface in a sol-gel solution mainly composed of acetic acid (pH≈5) is considered an anion, and the template molecule It is thought that the metal oxide adheres electrostatically on the fiber structure surface of the gel and grows.
If the content of metal oxide (inorganic material) is too much compared to the chiral organic compound, the organic compound is compressed due to shrinkage of the metal oxide during drying, making it difficult to form a hollow structure, and fusion of metal oxides occurs. This is undesirable because it does not result in an independent fibrous structure, and if it is too small, the hollow structure of the metal oxide becomes brittle. The amount of the metal oxide with respect to the organic-inorganic composite is generally 20 to 90% by weight.
[0030]
Properties of organic-inorganic composites and metal oxides
The organic-inorganic composite of the present invention has a structure in which a metal oxide is attached to the surface of a fibrous chiral organic compound, that is, a double cylindrical structure in which the inside is a chiral organic compound and the outside is a metal oxide. (That is, it exhibits an annular cross section in which a metal oxide is present outside a cylindrical chiral organic compound). The diameter (outermost diameter) of the cylinder is on the order of nanometers, that is, generally several nanometers to several hundred nanometers (for example, about 30 to 200 nm). The inner chiral organic compound retains the helix structure (helical structure) of the template gel oriented according to its chirality, and therefore exhibits an overall helical shape as an organic-inorganic composite.
[0031]
When the chiral organic compound is removed from the organic-inorganic composite as described above, a cylindrical structure having an inner diameter corresponding to the size of the chiral compound, that is, the inner diameter is on the order of nanometers (for example, about 10 to 100 nm). A hollow fiber-like and helical metal oxide structure is obtained.
[0032]
The organic-inorganic composite of the present invention is useful as a precursor of a hollow fiber-like helical metal oxide (for example, silica), but various uses are expected. For example, the organic-inorganic composite of the present invention catalyzes only molecules having affinity for the outer helical metal oxide form (helical direction etc.) by leaving a chiral organic compound having catalytic activity inside the hollow fiber. It is possible to denature.
[0033]
On the other hand, the hollow fiber-like and spiral metal oxide of the present invention can be applied to a catalyst, an adsorbent, etc. using both the outer surface and the inner surface of the hollow fiber. Since it has a helical structure, it is expected to be used as a catalyst or a catalyst support for a reaction involving chirality. In addition, the hollow fiber metal oxide of the present invention is bulky because it is in a fiber state, and in addition to this, it has a high heat insulating effect due to its hollow structure, and it is also excellent as a heat insulating material because the metal oxide has high heat resistance. .
[0034]
【Example】
Examples are given below to further clarify the features of the present invention, but the present invention is not limited to these examples.
Example 1: Synthesis of chiral organic compounds
According to the reaction scheme shown in FIG. 2, 1-4 diaminocyclohexane derivatives were synthesized as gelling chiral organic compounds serving as templates for preparing organic-inorganic composites and metal oxides. 2 and 4 are cationic chiral organic compounds corresponding to n = 10 in the aforementioned formula (I), and 1 and 3 are nonionic chiral compounds corresponding to m = 11 in the aforementioned formula (II). .
[0035]
(1) Compounds 7 and 8: Trans (1R, 2R- or 1S, 2S-)-diaminocyclohexane (1.0 g, 8.57 mmol) and 11-bromoundecanoic acid (7.66 g, 35.01 mmol) in a nitrogen atmosphere Below, it was dissolved in 30 ml of THF. The resulting solution was kept at room temperature. Then dicyclohexylcarbodiimide (7.2 g, 8.57 mmol) and dimethylaminopyridine (0.40 g, 0.857 mmol) were added and the mixture was stirred at room temperature for 48 hours. The reaction mixture was filtered and extracted with an acidic aqueous solution and a basic aqueous solution (50 ml). The organic phase was evaporated in an evaporator and the residue was purified on a silica gel column eluting with THF / hexane (1: 2 v / v) to give compounds 7 and 8 (yields 57% and 60% respectively). Obtained.¹H-NMR: δH (300 MHz): 6.15 (2H, s), 3.75 (2H, s), 3.37 (4H, t, J = 6.0), 2.17-1.26 ( 4H, m). IR: 3350, 2980, 1603, 1116, 1047 cm^{− 1}.
[0036]
(2) Compounds 1 and 3: trans (1R, 2R- or 1S, 2S) -diaminocyclohexane (1.0 g, 8.57 mmol), lauroyl chloride (7.66 g, 35.02 mmol) and triethylamine (3.54 g, 35.012 mmol) was dissolved in THF (30 ml) and refluxed for 48 hours. The resulting solution was cooled, filtered and then evaporated in vacuo to remove the solvent. The residue was purified on silica gel eluting with ethyl acetate / hexane (1: 2 v / v) to give the desired compounds 1 and 3. Yields are 50% and 55%, respectively. Elemental analysis (C₃₀H₅₈N₂O₂As :) Calculated value (C, 75.26; H, 12.21; N, 5.85; O, 6.68%), measured value (C, 75.0, H, 12.5; N, 5 .7%).¹H-NMR: δH (300 MHz): 6.15 (2H, s), 3.75 (2H, s), 3.37 (4H, t, J = 6.0), 2.17-1.25 ( 44H, m), 0.87 (6H, t, J = 5.7). MS (SIMS) = 478 [M + H]⁺. IR: 3350, 2980, 1722, 1603, 1116, 1047 cm^-1.
[0037]
(3) Compounds 2 and 4: Compound 7 or 8, and triethylamine were dissolved in THF / DMF (9: 1 v / v), and the resulting mixture was stirred at room temperature for 24 hours. The solvent was removed by vacuum evaporation, and the compounds 2 and 4 were obtained by purification in the same manner as in the case of compounds 1 and 3. Elemental analysis (C₃₄H₇₀Br₂N_FourO₂As :) Calculated value (C, 56.19; H, 9.71; Br, 21.99; N, 7.71; O, 4.40%) Actual value (C, 56.5, H, 9. 2; N, 8.0%).¹H-NMR: δ (300 MHz): 7.26 (2H, s), 4.01-3.45 (20H, m), 2.40 (4H, t, J = 6.0), 2.17- 1.25 (38H, m), 0.87 (6H, t, J = 5.7). MS (SIMS) = 725 [M + H]⁺. IR: 3350, 2980, 1722, 1603, 1116, 1047 cm^-1.
[0038]
Example 2: Gelability test of chiral organic compound and structural analysis of gel
Using the compounds 1 to 4 synthesized in Example 1, the gelation ability with respect to various solvents was examined. The gelation ability test was performed as follows: Compounds 1 to 4 (3 mg each) were mixed with a solvent in a capped test tube so that the concentration of each of Compounds 1 to 4 was 5% by weight. Heated until solids dissolved. The resulting solution was cooled to room temperature and left for 1 hour to observe gel formation. The results are shown in Table 1.
[0039]
[Table 1]

[0040]
  From the above results, compounds 1 to 4 have gelling ability with respect to various solvents, and in particular, nonionic compounds 1 and 3 function as excellent gelling agents with respect to all the solvents shown in the table. Was confirmed.
  Next, a cationic chiral organic compound andNonionCD (Circular Dichroism) spectrum was measured in order to investigate the structure of the gel obtained by using an organic chiral organic compound in combination. FIG. 3 is a CD spectrum chart of an acetonitrile solution in a gel state when a mixture of compound 1 + compound 2 or compound 3 + compound 4 (50/50 wt%) is used as a gelling agent. The CD spectrum of the R-enantiomer mixture (compound 1 + compound 2) showed a negative sign for the first cotton effect, suggesting that a left-handed (counterclockwise) spiral was formed. On the other hand, in the CD spectrum of the S-enantiomer mixture (compound 3 + compound 4), the first cotton effect shows a positive sign, suggesting that a right-handed (clockwise) spiral is formed. .
[0041]
This was also confirmed by microscopic observation of a xerogel from which the solvent (acetonitrile) was removed. FIG. 4 shows that the above acetonitrile solution in a gel state is freeze-dried at a temperature below the sol-gel transition temperature (39.5 to 40.2 ° C. for compound 1 + 2 and 35.2 to 37.0 ° C. for compound 3 + 4). 2 is a scanning electron micrograph of a xerogel obtained by removing acetonitrile. In each case, a spiral fiber aggregate having a width of 20 to 60 nm is formed, and when the R-enantiomer mixture (compound 1 + 2) is used (A in FIG. 4), the fiber orientation is left-handed, and When the S-enantiomer mixture (compound 3 + 4) is used (B in FIG. 4), it is recognized that the direction of the fiber is right-handed.
[0042]
Example 3: Production of organic-inorganic composite and metal oxide
As shown in Example 2, it was confirmed that by using Compound 1 + Compound 2 or Compound 3 + Compound 4 together, a spiral gel in a certain direction was formed in the solvent. An attempt was made to produce an organic-inorganic composite having a helical structure and a metal oxide by a sol-gel reaction using such a gel having a helical structure as a template.
[0043]
First, a sol-gel reaction solution composed of acetonitrile (80.0 mg), TEOS (tetraethoxysilane) (8.0 mg), water (4.0 mg), and benzylamine (4.0 mg) as a catalyst was added to compound 1 + compound 2 or A mixture of compound 3 + compound 4 (each having a total weight of 3.0 mg of the mixture and changing the ratio of compound 1 / compound 2 or compound 3 / compound 4) was added to prepare a uniform mixture. From the early stage of mixing, it became cloudy and gelation was observed. This was left at room temperature for 7 days.
[0044]
  Next, this was dried at room temperature for 2 days and then dried under vacuum at 60 ° C. for 5 hours to obtain an organic-inorganic composite. In FIG.Compound 1 / Compound 2The SEM (scanning electron microscope) photograph of this composite in the case of 50/50 (weight%) is shown.Similar SEM photographs were obtained for the composites in which compound 3 / compound 4 was 50/50 (wt%). theseFrom this photo, it is shown that the cylinder has a spiral shape with a double cylinder structure, and the diameter (outer diameter) of the cylinder is about 50 to 200 nm.Was. It is understood that the spiral is left-handed when Compound 1 + Compound 2 is used, and right-handed when Compound 3 + Compound 4 is used, reflecting the gel state chirality.The.
[0045]
Further, it was dried at 200 ° C. for 2 hours under a nitrogen stream, then calcined at 500 ° C. for 2 hours and finally at 500 ° C. for 4 hours under an air stream to obtain a metal oxide (silica). The structure of the obtained silica was observed with a TEM (transmission electron microscope). The results are shown in Table 2.
[0046]
[Table 2]

[0047]
As shown in Table 2, when a cationic compound 2 or compound 4 is 30 to 85% by weight, a silica having a helical structure is formed, and when it is 100% or too little, a simple cylinder as conventionally seen Only shaped (non-spiral) silica is obtained. Furthermore, when compound 1 and compound 2 are used according to the chirality of the gel structure, a left-handed spiral structure is formed, and when compound 3 and compound 4 are used, a right-handed spiral structure is formed. It is understood that it is faithfully transcribed. The outer diameter of silica obtained from the observation result of TEM is about 100 to 150 nm and the inner diameter is about 20 to 60 nm. FIG. 6 shows a TEM photograph when Compound 1 / Compound 2 (A in FIG. 6) or Compound 3 / Compound 4 (B in FIG. 6) is 50/50 (weight) as a representative example.
[Brief description of the drawings]
FIG. 1 illustrates cationic chiral organic compounds and nonionic chiral compounds suitable for use in the present invention.
FIG. 2 shows a reaction scheme for synthesizing a diaminocyclohexane derivative, which is a chiral organic compound suitable for use in the present invention.
FIG. 3 shows an example of a CD spectrum of an organic gel used as a template in the present invention.
FIG. 4 is a transmission electron micrograph showing the crystal structure of an organic gel (xerogel) serving as a template in the present invention.
FIG. 5 is a transmission electron micrograph showing the crystal structure of one example of the organic-inorganic composite of the present invention.
FIG. 6 is a transmission electron micrograph showing the crystal structure of one example of the metal oxide of the present invention.

Claims (3)

(1) a. An ionic chiral organic compound capable of forming a gel in an organic solvent and / or water, and a nonionic chiral compound having the same chirality as the ionic chiral organic compound and capable of forming a gel in an organic solvent and / or water Mixtures with organic compounds, and
B. A sol-gel reaction solution comprising a metal oxide precursor, a catalyst for forming a metal oxide polymer from the metal oxide precursor by a sol-gel reaction, and water (provided that the solubility of the sol-gel reaction solution is not sufficient) Is a step of mixing a precursor of the metal oxide, a catalyst, and a solvent capable of dissolving water) to prepare a homogeneous mixed solution (however, in order to facilitate mixing, the chiral organic compound and An organic solvent capable of dissolving the sol-gel reaction solution may be used),
(2) a. (Or in the case of using the organic solvent to remove the organic solvent from the previous SL homogeneous mixture)
B. (C) heating or cooling the homogeneous mixture, or c. Cooling the homogeneous mixture;
A step of forming a gel of the organic chiral compound, and (3) a step of maintaining the gel-formed system and advancing the polymerization of the metal oxide,
A method for producing an organic-inorganic composite in which a metal oxide is attached to the surface of a chiral organic compound having a spiral structure in a certain direction, characterized by comprising:
The ionic chiral organic compound is selected from diaminocyclohexane derivatives that are cationic chiral organic compounds represented by formula (I), and the nonionic chiral organic compound is selected from diaminocyclohexane derivatives represented by formula (II). Here, the cationic chiral organic compound is 30 to 85% by weight with respect to the total amount of the cationic chiral organic compound and the nonionic chiral organic compound, and the metal oxide is silica. Method.

[In Formula (I), n is an integer of 5-20, X represents a halogen atom, and m is an integer of 6-21 in Formula (II). ]   A method for producing a hollow silica-like spiral silica in a certain direction, wherein a chiral organic compound is removed from an organic-inorganic composite obtained by the method of claim 1.   The method for producing hollow fiber-like helical silica according to claim 2, wherein the chiral organic compound is removed by calcination.

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