JP4014960B2 - Molecular wire and manufacturing method thereof - Google Patents

Description

【００１７】
（Ｍは金属元素、Ｒ₁，Ｒ₂はそれぞれ炭化水素基、Ｘ₁〜Ｘ₄はそれぞれデンドリマーを示す）にて表される繰り返し構造を有していることが好ましい。
【００１８】
また、本発明の分子ワイヤの製造方法は、π電子系分子にデンドリマーを導入し、該デンドリマーを導入したπ電子系分子を互いに結合することを特徴としている。
【００１９】
上記π電子系分子とは、該π電子系分子が互いに結合することによって共役分子となる分子である。
【００２０】
具体的には、下式（２）
【００２１】
【化４】

【００２２】
（Ｍは金属元素、Ｒ₁，Ｒ₂はそれぞれ炭化水素基、Ｘ₁〜Ｘ₄はそれぞれデンドリマー、Ｙ₁，Ｙ₂はそれぞれ任意の置換基を示す）にて表される構造を有する化合物をカップリング反応により結合することが好ましい。
【００２３】
上記Ｙ₁，Ｙ₂にて表される置換基は、カップリング反応によって取り外される置換基であれば特に限定されるものではない。
【００２４】
上記の方法によれば、直線構造を有する剛直な分子ワイヤであって、再現性の高い特性を有する分子ワイヤを得ることができる。
【００２５】
【発明の実施の形態】
本発明の実施の一形態について図１ないし図３に基づいて説明すれば、以下の通りである。
【００２６】
本発明の分子ワイヤは、π電子系による共役を有する有機系の共役分子からなり、該共役分子は、共役π電子系ではない嵩高い置換基として、デンドリマーを有している。
【００２７】
π電子系の共役を有する共役分子としては、π電子系の共役を利用して電子の輸送等を行う従来の分子ワイヤであれば特に限定されない。具体的には、芳香族環式化合物や芳香族複素環式化合物，これら環式化合物等が縮合した多環式化合物等の不飽和環式化合物；炭素−炭素二重結合又は三重結合を有する共役系の不飽和鎖式化合物；これらの各化合物が互いに結合した複合化合物、等を挙げることができる。
【００２８】
上記不飽和環式化合物としては、ベンゼン，ナフタレン，アントラセン，これらの各化合物の誘導体等の芳香族環式化合物；チオフェン，ピロール，これらの各化合物の誘導体等の芳香族複素環式化合物；ポルフィリン系化合物，フラーレン，これらの各化合物の誘導体等の多環式化合物を挙げることができる。さらに、不飽和鎖式化合物としては、アセチレンやアセチレン誘導体等が重合してなるポリアセチレン系化合物，エチレンやエチレン誘導体等を挙げることができる。また、複合化合物としては、上記不飽和環式化合物や上記多環式化合物と、上記不飽和鎖式化合物とが結合した化合物等を挙げることができる。
【００２９】
なお、上記誘導体とは、上記の各化合物に水素以外の炭化水素基，エーテル基，水酸基，アリール基，複素環基等の置換基が結合している化合物を示す。
【００３０】
上記のπ電子系の共役を有する共役分子として、さらに具体的には、例えば、従来より分子ワイヤとして用いられている、図３（ａ）に示すベンゼン−アセチレン系化合物、図３（ｂ）に示すポルフィリン系化合物、図３（ｃ）に示すチオフェン系化合物、ポルフィリン系化合物とアセチレン又はアセチレン誘導体とが交互に結合したポルフィリン−アセチレン系化合物、文献（Rainer E. Martin & Fransois Diederich，Angew.Chem.Int.Ed.，38，p.1350-1377(1999)）に記載の化合物等を挙げることができる。これらの化合物も、本発明の分子ワイヤを構成するπ電子系の共役を有する共役分子として用いることができる。
【００３１】
なお、上記ポルフィリン−アセチレン系化合物のポリフィリン系化合物としては、具体的には、β位やメタ位に置換基を有しているポルフィリン化合物；これらのポルフィリン化合物にて、金属元素を中心原子とするポルフィリン錯体等を挙げることができる。上記中心原子となる金属元素は、亜鉛，ニッケル，鉄，マグネシウム，銅等、特に限定されないが、ベリリウム及び希土類元素以外の金属元素であることが好ましい。
【００３２】
また、アセチレン又はアセチレン誘導体としては、アセチレン，ジアセチレン，アルキル置換基を有するアセチレン等を挙げることができる。
【００３３】
上記共役分子に、デンドリマーを置換基として導入しているが、デンドリマーに限定されず、共役π電子系ではない嵩高い置換基であれば、同様に用いることができる。共役π電子系ではない嵩高い置換基としては、例えば、枝分かれしたアルキル基等を挙げることができる。
【００３４】
上記した共役分子の側鎖に、上記の嵩高い置換基を導入することによって、本発明の分子ワイヤを得ることができる。例えば、ポルフィリン−アセチレン系化合物を共役分子として用いた場合、前記式（１）に示す繰り返し構造を有する分子ワイヤが得られる。
【００３５】
式（１）中のＲ₁，Ｒ₂としては、例えば、ベンゼン，ナフタレン，アントラセンが好ましく、特にベンゼンが好ましい。なお、Ｒ₁，Ｒ₂は互いに異なる置換基であってもよく、また、Ｘ₁〜Ｘ₄は、それぞれ異なるデンドリマーであってもよい。但し、直線構造の分子ワイヤを得るためには、置換基及びデンドリマーは、それぞれ同一又は同程度の大きさを有することが好ましい。
【００３６】
これにより、図１に示すように、前記の式（１）にて表される繰り返し構造を有する分子ワイヤ１は、アセチレン基間にて結合が生じて直線状に連なった共役分子の周囲を、デンドリマー２によって覆われた構造を有している。そのため、上記分子ワイヤ１は、その直径が約５ｎｍ程度になり、太くてかつ剛直なものとなる。また、デンドリマー２が立体障害となり、曲がりにくくなるので、直線構造の分子ワイヤ１が得られ、所望する配線を形成しやすく、かつ効率のよい電子輸送が可能になる。
【００３７】
さらに、例えば、ナノリソグラフィによって形成したナノギャップ電極に、上記分子ワイヤ１を配置した場合にも、分子ワイヤ１の直径が、ナノギャップ電極の２ｎｍ程度の凹凸よりも大きくなるので、分子ワイヤ１の存在状態や配線状態を走査プローブ顕微鏡にて観測することができる。
【００３８】
従って、本発明の分子ワイヤは、分子電子素子における部品として用いることができ、分子電子素子間、又は、外部電極と分子電子素子との間の電子輸送や静電的な結合を行う配線として利用することができる。
【００３９】
また、図２に示すように、ドレイン電極−ソース電極間に共役分子３の周囲をデンドリマー２によって覆った分子ワイヤ１を配置し、その下方にゲート電極を配置すれば電界効果トランジスタとして用いることもできる。この電界効果トランジスタでは、ゲート電極に印加するゲート電圧を変化させることによって分子ワイヤの軌道レベルをシフトさせることができると考えられる。さらに、分子ワイヤのソース電極との結合条件を変化することにより、高速化及び省エネルギー化を図ることができると考えられる。
【００４０】
次に、本発明の分子ワイヤの製造方法について説明する。
【００４１】
本発明の分子ワイヤは、π電子系分子に、デンドリマー等の嵩高い置換基を導入し、その後、上記置換基を導入したπ電子系分子を結合させる。すなわち、例えば、共役分子としてのポルフィリン−アセチレン系化合物にデンドリマーを導入してなる前記式（２）にて表される化合物を作製し、式（２）にて表される化合物を酸化カップリング反応により結合すればよい。
【００４２】
なお、式（２）中のＹ₁，Ｙ₂は、酸化カップリング反応にて、取り外され得る置換基であれば特に限定されないが、例えば、ＴＭＳ（Ｓｉ(ＣＨ₃)₃），Ｓｉ(ＣＨ₃)₂Ｃ(ＣＨ₃)₃等であることが好ましい。
【００４３】
【実施例】
〔実施例〕
本発明の一実施例として、前記したポルフィリン−アセチレン系化合物を共役分子として用いた分子ワイヤについて説明すれば、以下のとおりである。
【００４４】
窒素雰囲気下にて、１００ｍＬの３つ口フラスコにクロロホルム１００ｍＬを入れ、さらにポルフィリン（化合物▲１▼）１００ｍｇ（0.17mmol）を溶かした。次いで、Ｎ−ブロモスクシンイミド（ＮＢＳ）６１ｍｇ（0.35mmol）を添加し、反応の進行を高速液体クロマトグラフィ（ＴＬＣ）にて確認し、反応終了後、溶媒を減圧下にて留去した。その後、カラムクロマトグラフィにて、得られた生成物を分取し、再結晶を行って、収量９３ｍｇ（収率７３％）にて化合物▲２▼（Ｃ₃₆Ｈ₂₈Ｂｒ₂Ｎ₄Ｏ₄）を得た（式（３））。
【００４５】
【化５】

【００４６】
得られた化合物▲２▼の質量分析（MALDI-TOF-MS）の結果、分子量は７３９．５０と見積もられた（化学式からの計算では、７３８．０５となる）。
【００４７】
また、溶媒をＣＤＣｌ₃として、化合物▲２▼の¹Ｈ−ＮＭＲ測定（400ＭＨｚ）を行ったところ、化学シフトδ（ppm）＝9.60（４Ｈ，brs，Ｈ_b）,8.94（４Ｈ，brs，Ｈ_a），7.34（４Ｈ，ｍ，ベンゼン環），6.92（２Ｈ，ｍ，ベンゼン環），3.98（１２Ｈ，ｓ，ＯＭｅ）にピークが見られるスペクトルが得られた。
【００４８】
なお、上記括弧内は、順に、各ピークに帰属されるＨ数，スペクトルのピークの形状，化合物中のＨの位置を表す。また、brsはスペクトルがブロードであることを示し、ｍはスペクトルが多重線であることを示し、ｓはスペクトルが一重線であることを示す。Ｈ_a及びＨ_bは、式（３）中の化合物▲２▼のａ，ｂにて示す位置の炭素に結合するＨを示す。
【００４９】
さらに、溶媒をＣＨＣｌ₃として、化合物▲２▼の紫外可視吸収スペクトル測定を行った結果、吸収ピーク波長λmax（ｎｍ）＝657，600，555，520，423であった。
【００５０】
次に、窒素雰囲気下にて、上記化合物▲２▼１００ｍｇ（0.13mmol）を１００ｍＬの３つ口フラスコに入れ、さらに、酢酸亜鉛２水和物２９６ｍｇ（1.35mmol）及びクロロホルム１００ｍＬを加えて、反応の進行をＴＬＣにて確認しながら２４時間撹拌した。反応終了後、生成物を、水，重曹水，食塩水にて洗浄し、無水硫酸ナトリウムで乾燥した後、再結晶を行って、収量１００ｍｇ（収率９３％）にて化合物▲３▼（Ｃ₃₆Ｈ₂₈Ｂｒ₂Ｎ₄ＺｎＯ₄）を得た（式（４））。
【００５１】
【化６】

【００５２】
得られた化合物▲３▼の質量分析（MALDI-TOF-MS）の結果、分子量は８００と見積もられた（化学式からの計算では、８００となる）。また、溶媒をＣＨＣｌ₃として、化合物▲３▼の紫外可視吸収スペクトル測定を行った結果、λmax（ｎｍ）＝608，565，431であった。
【００５３】
続いて、窒素雰囲気下にて、上記にて得られた化合物▲３▼８９ｍｇ（0.11mmol）を１００ｍＬの３つ口フラスコに入れ、乾燥塩化メチレン３０ｍＬを添加して、液体窒素−アセトンバスにて−７８℃まで冷却した。その後、三臭化ホウ素０．４ｍＬを静かに加えて、１２時間撹拌した後、重曹水及び水にてよく洗浄し、メタノールにて抽出を行って、収量８１ｍｇ（収率９６％）にて化合物▲４▼を得た（式（５））。
【００５４】
【化７】

【００５５】
得られた化合物▲４▼の紫外可視吸収スペクトル測定を行った結果、λmax（ｎｍ）＝605，564，423であった。
【００５６】
次いで、窒素雰囲気下にて、上記にて得られた化合物▲４▼８１ｍｇ（0.11mmol）、文献（Craig J.Hawker & J.M.J. Frechet，J.Am.Chem.Soc.，112，p.7638-7647(1990)）に従って合成したデンドリマーの臭化物（下記、Ｇ４−Ｂｒ）１０１０ｍｇ（0.47mmol）、炭酸カリウム４６ｍｇ（0.46mmol）、18−クラウン−６−エーテル５０ｍｇ、ＴＨＦ８０ｍＬを１００ｍＬの３つ口フラスコに入れ、１０日間還流した。その後、クロロホルムを加え、有機層を水及び食塩水にて洗浄し、無水硫酸ナトリウムで乾燥して溶媒を留去した。さらに、ゲル濾過型分取液体クロマトグラフィにて分取して精製し、粗収率３５％にて化合物▲５▼（Ｃ₅₁₆Ｈ₅₁₆Ｂｒ₂Ｎ₄ＺｎＯ₁₂₄）を得た（式（６））。
【００５７】
【化８】

【００５８】
得られた化合物▲５▼の質量分析（MALDI-TOF-MS）の結果、分子量は９００１と見積もられた（化学式からの計算では、８９６３となる）。
【００５９】
また、溶媒をＣＤＣｌ₃として、化合物▲２▼の¹Ｈ−ＮＭＲ測定（400ＭＨｚ）を行ったところ、化学シフトδ（ppm）＝9.35（４Ｈ，brs，Ｈ_b）,8.68（４Ｈ，brs，Ｈ_a），6.20-6.63（１８６Ｈ，ｍ，ベンゼン環），4.70（１２４Ｈ，ｍ，ＣＨ₂Ｏ），3.56（１９６Ｈ，ｓ，ＯＭｅ）にピークが見られるスペクトルが得られた。なお、括弧内の記載は、上記したとおりであり、Ｈ_a及びＨ_bは、式（６）中の化合物▲５▼のａ，ｂにて示す位置の炭素に結合するＨを示す。
【００６０】
さらに、溶媒をＣＨＣｌ₃として、化合物▲５▼の紫外可視吸収スペクトル測定を行った結果、最大吸収波長λmax（ｎｍ）＝608，565，431であった。
【００６１】
次に、窒素雰囲気下にて、上記にて得られた化合物▲５▼１５０ｍｇ（17mmol）、パラジウム触媒１０ｍｇ、ヨウ化銅１０ｍｇを１００ｍＬの３つ口フラスコに入れて、乾燥ＴＨＦ８０ｍＬに溶解し、さらにトリエチルアミン０．１ｍＬ、トリメチルシリル（ＴＭＳ；Ｓｉ(ＣＨ₃)₃）アセチレン０．１ｍＬを添加して、２０時間還流した。その後、得られた生成物を水にて洗浄し、無水硫酸ナトリウムで乾燥させ、カラムクロマトグラフィにて分取して精製し、収量８２ｍｇ（収率５５％）にて化合物▲６▼（Ｃ₅₂₆Ｈ₅₃₄Ｓｉ₂Ｎ₄ＺｎＯ ₁₂₄ ）を得た（化（７））。
【００６２】
【化９】

【００６３】
得られた化合物▲６▼の質量分析（MALDI-TOF-MS）の結果、分子量は９００２と見積もられた（化学式からの計算では、８９９９となる）。
【００６４】
また、溶媒をＣＤＣｌ₃として、化合物▲２▼の¹Ｈ−ＮＭＲ測定（400ＭＨｚ）を行ったところ、化学シフトδ（ppm）＝9.58（４Ｈ，brs，Ｈ_b）,8.91（４Ｈ，brs，Ｈ_a），6.80-6.25（１８６Ｈ，ｍ，ベンゼン環），4.81（１２４Ｈ，ｍ，ＣＨ₂Ｏ），3.64（１９２Ｈ，ｓ，ＯＭｅ），0.52（１８Ｈ，ｓ，ＴＭＳ）にピークが見られるスペクトルが得られた。なお、括弧内の記載は、上記したとおりである。
【００６５】
さらに、溶媒をＣＨＣｌ₃として、化合物▲５▼の紫外可視吸収スペクトル測定を行った結果、最大吸収波長λmax（ｎｍ）＝621，571，437であった。
【００６６】
上記の手順にて得られた化合物▲５▼のＴＭＳ基をテトラブチルアンモニウムフルオリドによってはずし、酢酸銅及びピリジンの存在下にて、酸化カップリング反応を行うことにより、化合物▲５▼が三重結合によって連なった分子ワイヤが得られた。
【００６７】
【発明の効果】
本発明の分子ワイヤは、以上のように、π電子系による共役を有する共役分子に対して、共役π電子系ではないデンドリマー等の嵩高い置換基を導入してなるものである。
【００６８】
それゆえ、共役分子がデンドリマーによって覆われた分子ワイヤを得ることができるので、分子ワイヤの直径を大きくすることができるという効果を奏する。また、分子ワイヤが折り曲がりにくくなり、直線構造の剛直な分子ワイヤを提供することができるという効果を奏する。
【００６９】
その結果、分子電子素子や電極等を上記分子ワイヤにて結合する場合、目的の位置へ配線することが容易になり、分子電子素子や電極等に張り巡らされた分子ワイヤを走査プローブ顕微鏡によって、所望した位置に配線が形成されていることを確認することができるという効果を奏する。さらに、共役分子のπ電子系部分が、デンドリマーの存在によって周囲の分子や電極等から遮断され、不必要な電子的な干渉を受けにくくなり、外部への電子の漏れや、共役分子の酸化を防ぐことができるという効果を奏する。
【図面の簡単な説明】
【図１】本発明における分子ワイヤを示す図である。
【図２】本発明の分子ワイヤを用いた電界効果トランジスタの断面図である。
【図３】（ａ）〜（ｃ）は、従来の分子ワイヤの構造式である。
【符号の説明】
１ 分子ワイヤ
２ デンドリマー
３ 共役分子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a molecular wire used as a wiring for electrically connecting molecular electronic devices.
[0002]
[Prior art]
In the field of nanotechnology, molecular devices in which individual molecules have functions such as diodes and transistors have been proposed as new devices that can replace LSIs (Large Scale Integrated Circuits). In order to make a molecular device function, wiring for electrically connecting molecular electronic elements having individual molecules as functional units is necessary. Since the size of the molecule is nanometer size, the wiring used for the molecular device needs to be on the nanometer order.
[0003]
As such wiring, a molecular wire using conductive organic molecules has been proposed. Wiring technology using molecular wires is indispensable for the development of molecular devices, and is being developed for practical use.
[0004]
Specifically, paying attention to the length of the molecular wire and its electronic state, a long molecular wire with a small energy gap has been designed so far. As such a molecular wire, for example, as shown in FIGS. 3A to 3C, a conjugated molecular wire having a π-electron-based conjugation can be exemplified. That is, as shown in FIG. 3 (a), a conjugated molecular wire in which benzene rings are connected by a carbon-carbon triple bond, as shown in FIG. 3 (b), a conjugated molecular wire having conjugation with a porphyrin compound, 3 (c), a conjugated molecular wire linked with thiophene, described in the literature (Rainer E. Martin & Fransois Diederich, Angew. Chem. Int. Ed., 38, p. 1350-1377 (1999)). The conjugated molecular wire etc. which can be mentioned. Each of the conjugated molecular wires described above can be used as a wiring that transports electrons by intramolecular conjugation and electrically connects molecular electronic devices.
[0005]
[Problems to be solved by the invention]
However, it has been found from the observation with a scanning probe microscope or the like that the conventional conjugated molecular wire is very easy to bend and has a linear structure. That is, the conventional conjugated molecular wire has a problem that it can be bent easily and cannot maintain a linear structure.
[0006]
The bends that occur in the molecular wires make it difficult to bond the molecular electronic devices at desired positions. Further, when the molecular wire is bent, conjugation in the molecule may be interrupted, and efficient electron transport may not be performed.
[0007]
The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a molecular wire having a straight structure, a stable molecular wire, and a manufacturing method thereof. There is to do.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the molecular wire of the present invention is a molecular wire composed of a conjugated molecule having conjugation by a π-electron system, and the conjugated molecule has a dendrimer as a substituent.
[0009]
The conjugated molecule is a chain molecule in which two or more multiple bonds are connected to each other with one single bond interposed therebetween, and electron transport can be performed by an interaction (conjugation) by this connection.
[0010]
According to the above configuration, a dendrimer is introduced into the conjugated molecule as a non-conjugated bulky substituent. Dendrimers are multi-branched polymers having a star-like structure, so they are very bulky and have great steric hindrance. This makes it difficult for the molecular wire to bend and provides a rigid molecular wire having a linear structure. Therefore, when a molecular electronic device, an electrode, or the like is coupled with the molecular wire, wiring to a target position becomes easy.
[0011]
Furthermore, since the conjugated molecule is covered with a bulky dendrimer, electronic interference between the conjugated molecule and the outside is unlikely to occur. Thereby, efficient electron transport is possible, and a molecular wire having stable characteristics can be provided.
[0012]
Further, since the diameter of the molecular wire can be increased by surrounding the conjugated molecule with a dendrimer, the diameter of the molecular wire can be observed with a scanning probe microscope. Therefore, the molecular wire stretched between the electrodes of the molecular electronic device can be observed with a scanning probe microscope, and it can be confirmed that the wiring is formed at a desired position. As a result, it is considered that a quantitative experiment of the molecular electronic device can be suitably performed and a reproducible molecular electronic device can be obtained.
[0013]
Furthermore, since a bulky substituent surrounds the periphery of the conjugated molecule, the π-electron system portion of the conjugated molecule is blocked from the surrounding molecules, electrodes, and the like, and is less susceptible to unnecessary electronic interference. Accordingly, leakage of electrons to the outside and oxidation of the conjugated molecule can be prevented, and a molecular wire having stable characteristics can be obtained.
[0014]
The molecular wire of the present invention is characterized in that, in the molecular wire, the conjugated molecule is composed of a series of porphyrin compounds.
[0015]
Specifically, the conjugated molecule has the following formula (1):
[0016]
[Chemical 3]

[0017]
It is preferable to have a repeating structure represented by (M is a metal element, R ₁ and R ₂ are each a hydrocarbon group, and X _{1 to} X ₄ are each a dendrimer).
[0018]
The molecular wire manufacturing method of the present invention is characterized in that a dendrimer is introduced into a π-electron molecule, and the π-electron molecule into which the dendrimer is introduced is bonded to each other.
[0019]
The π-electron molecule is a molecule that becomes a conjugated molecule when the π-electron molecules are bonded to each other.
[0020]
Specifically, the following formula (2)
[0021]
[Formula 4]

[0022]
(M is a metal element, R ₁ and R ₂ are each a hydrocarbon group, X _{1 to} X ₄ are dendrimers, and Y ₁ and Y ₂ are each an arbitrary substituent) It is preferable to couple | bond by a coupling reaction.
[0023]
The substituent represented by Y ₁ and Y ₂ is not particularly limited as long as it is a substituent removed by a coupling reaction.
[0024]
According to the above method, a molecular wire having a straight structure and a highly reproducible characteristic can be obtained.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
One embodiment of the present invention will be described with reference to FIGS. 1 to 3 as follows.
[0026]
The molecular wire of the present invention comprises an organic conjugated molecule having conjugation by a π electron system, and the conjugated molecule has a dendrimer as a bulky substituent that is not a conjugated π electron system.
[0027]
The conjugated molecule having π-electron conjugation is not particularly limited as long as it is a conventional molecular wire that transports electrons using π-electron conjugation. Specifically, unsaturated cyclic compounds such as aromatic cyclic compounds, aromatic heterocyclic compounds, and polycyclic compounds obtained by condensing these cyclic compounds; conjugates having a carbon-carbon double bond or triple bond Unsaturated chain compounds of the system; complex compounds in which these compounds are bonded to each other.
[0028]
Examples of the unsaturated cyclic compound include aromatic cyclic compounds such as benzene, naphthalene, anthracene, and derivatives of these compounds; aromatic heterocyclic compounds such as thiophene, pyrrole, and derivatives of these compounds; porphyrins Examples thereof include polycyclic compounds such as compounds, fullerenes and derivatives of these compounds. Furthermore, examples of the unsaturated chain compound include polyacetylene compounds obtained by polymerizing acetylene and acetylene derivatives, ethylene and ethylene derivatives, and the like. Examples of the composite compound include compounds in which the unsaturated cyclic compound or the polycyclic compound is bonded to the unsaturated chain compound.
[0029]
In addition, the said derivative | guide_body shows the compound which substituents, such as hydrocarbon groups other than hydrogen, ether groups, a hydroxyl group, an aryl group, and a heterocyclic group, couple | bonded with each said compound.
[0030]
More specifically, for example, a benzene-acetylene compound shown in FIG. 3 (a), which has been conventionally used as a molecular wire, is shown in FIG. Porphyrin compounds shown in FIG. 3, thiophene compounds shown in FIG. 3C, porphyrin-acetylene compounds in which porphyrin compounds and acetylene or acetylene derivatives are alternately bonded, literature (Rainer E. Martin & Fransois Diederich, Angew. Chem. Int. Ed., 38, p.1350-1377 (1999)). These compounds can also be used as conjugated molecules having a π-electron conjugation constituting the molecular wire of the present invention.
[0031]
The porphyrin compound of the porphyrin-acetylene compound is specifically a porphyrin compound having a substituent at the β-position or meta-position; in these porphyrin compounds, the metal element is a central atom. A porphyrin complex etc. can be mentioned. The metal element serving as the central atom is not particularly limited, such as zinc, nickel, iron, magnesium, copper, but is preferably a metal element other than beryllium and rare earth elements.
[0032]
Examples of the acetylene or acetylene derivative include acetylene, diacetylene, acetylene having an alkyl substituent, and the like.
[0033]
Although a dendrimer is introduced into the conjugated molecule as a substituent, the dendrimer is not limited to a dendrimer, and any bulky substituent that is not a conjugated π-electron system can be used similarly. Examples of bulky substituents that are not conjugated π-electron systems include branched alkyl groups.
[0034]
The molecular wire of the present invention can be obtained by introducing the above bulky substituent into the side chain of the conjugated molecule. For example, when a porphyrin-acetylene compound is used as a conjugated molecule, a molecular wire having a repeating structure represented by the formula (1) is obtained.
[0035]
As R ₁ and R ₂ in the formula (1), for example, benzene, naphthalene and anthracene are preferable, and benzene is particularly preferable. R ₁ and R ₂ may be different from each other, and X _{1 to} X ₄ may be different dendrimers. However, in order to obtain a molecular wire having a linear structure, it is preferable that the substituent and the dendrimer have the same or similar sizes.
[0036]
As a result, as shown in FIG. 1, the molecular wire 1 having the repeating structure represented by the above formula (1) is formed around the conjugated molecule in which bonds are formed between the acetylene groups and linearly connected. It has a structure covered with dendrimer 2. Therefore, the molecular wire 1 has a diameter of about 5 nm, and is thick and rigid. In addition, since the dendrimer 2 becomes a steric hindrance and becomes difficult to bend, the molecular wire 1 having a linear structure can be obtained, and a desired wiring can be easily formed, and efficient electron transport becomes possible.
[0037]
Furthermore, for example, when the molecular wire 1 is arranged on a nanogap electrode formed by nanolithography, the diameter of the molecular wire 1 is larger than the irregularities of about 2 nm of the nanogap electrode. The presence state and the wiring state can be observed with a scanning probe microscope.
[0038]
Therefore, the molecular wire of the present invention can be used as a component in a molecular electronic device, and can be used as a wiring for performing electron transport and electrostatic coupling between molecular electronic devices or between an external electrode and a molecular electronic device. can do.
[0039]
In addition, as shown in FIG. 2, if a molecular wire 1 in which the periphery of a conjugated molecule 3 is covered with a dendrimer 2 is disposed between a drain electrode and a source electrode, and a gate electrode is disposed below the molecular wire 1, it can be used as a field effect transistor. it can. In this field effect transistor, it is considered that the orbital level of the molecular wire can be shifted by changing the gate voltage applied to the gate electrode. Furthermore, it is considered that speeding up and energy saving can be achieved by changing the coupling condition of the molecular wire with the source electrode.
[0040]
Next, the manufacturing method of the molecular wire of this invention is demonstrated.
[0041]
In the molecular wire of the present invention, a bulky substituent such as a dendrimer is introduced into a π-electron molecule, and then the π-electron molecule into which the substituent is introduced is bonded. That is, for example, a compound represented by the above formula (2) obtained by introducing a dendrimer into a porphyrin-acetylene compound as a conjugated molecule is prepared, and the compound represented by the formula (2) is subjected to an oxidative coupling reaction. Can be combined.
[0042]
Y ₁ and Y ₂ in the formula (2) are not particularly limited as long as they can be removed by an oxidative coupling reaction. For example, TMS (Si (CH ₃ ) ₃ ), Si (CH ₃ ) ₂ C (CH ₃ ) ₃ or the like is preferable.
[0043]
【Example】
〔Example〕
As one embodiment of the present invention, a molecular wire using the above porphyrin-acetylene compound as a conjugated molecule will be described as follows.
[0044]
Under a nitrogen atmosphere, 100 mL of chloroform was placed in a 100 mL three-necked flask, and 100 mg (0.17 mmol) of porphyrin (compound (1)) was further dissolved. Next, 61 mg (0.35 mmol) of N-bromosuccinimide (NBS) was added, and the progress of the reaction was confirmed by high performance liquid chromatography (TLC). After completion of the reaction, the solvent was distilled off under reduced pressure. Then, the obtained product was fractionated by column chromatography and recrystallized to obtain Compound (2) (C ₃₆ H ₂₈ Br ₂ N ₄ O ₄ ) in a yield of 93 mg (73% yield). Obtained (formula (3)).
[0045]
[Chemical formula 5]

[0046]
As a result of mass spectrometry (MALDI-TOF-MS) of the compound (2) obtained, the molecular weight was estimated to be 739.50 (calculated from the chemical formula was 738.05).
[0047]
Further, when ¹ H-NMR measurement (400 MHz) of compound (2) was performed using CDCl ₃ as a solvent, chemical shift δ (ppm) = 9.60 (4H, brs, H _b ), 8.94 (4H, brs, H _a ), 7.34 (4H, m, benzene ring), 6.92 (2H, m, benzene ring) and 3.98 (12H, s, OMe) were observed.
[0048]
In the parentheses, the H number attributed to each peak, the shape of the peak of the spectrum, and the position of H in the compound are shown in order. Further, brs indicates that the spectrum is broad, m indicates that the spectrum is a multiple line, and s indicates that the spectrum is a single line. H _a and H _b represent H bonded to carbon at the positions indicated by a and b in the compound (2) in the formula (3).
[0049]
Furthermore, as a result of measuring the ultraviolet visible absorption spectrum of Compound (2) using CHCl ₃ as the solvent, the absorption peak wavelength was λmax (nm) = 657, 600, 555, 520, 423.
[0050]
Next, in a nitrogen atmosphere, 100 mg (0.13 mmol) of the above compound (2) was put into a 100 mL three-necked flask, and further 296 mg (1.35 mmol) of zinc acetate dihydrate and 100 mL of chloroform were added to react. The mixture was stirred for 24 hours while confirming the progress of TLC by TLC. After completion of the reaction, the product was washed with water, aqueous sodium bicarbonate, and brine, dried over anhydrous sodium sulfate, recrystallized, and compound (3) (C _{36 H 28 Br 2 N 4 ZnO} 4) was obtained (formula (4)).
[0051]
[Chemical 6]

[0052]
As a result of mass spectrometry (MALDI-TOF-MS) of the obtained compound (3), the molecular weight was estimated to be 800 (calculated from the chemical formula was 800). In addition, as a result of measuring an ultraviolet-visible absorption spectrum of the compound ( ₃₎ using CHCl ₃ as a solvent, it was found that λmax (nm) = 608,565,431.
[0053]
Subsequently, 89 mg (0.11 mmol) of the compound (3) obtained above was placed in a 100 mL three-necked flask under a nitrogen atmosphere, 30 mL of dry methylene chloride was added, and the mixture was added in a liquid nitrogen-acetone bath. Cooled to -78 ° C. Thereafter, 0.4 mL of boron tribromide was added gently, and the mixture was stirred for 12 hours, washed well with aqueous sodium bicarbonate and water, extracted with methanol, and the compound was obtained in a yield of 81 mg (yield 96%). (4) was obtained (Formula (5)).
[0054]
[Chemical 7]

[0055]
The obtained compound (4) was subjected to ultraviolet-visible absorption spectrum measurement. As a result, it was found that λmax (nm) = 605, 564, 423.
[0056]
Subsequently, 81 mg (0.11 mmol) of the compound (4) obtained above under a nitrogen atmosphere, literature (Craig J. Hawker & JMJ Frechet, J. Am. Chem. Soc., 112, p. 7638-7647 (1990)) 1010 mg (0.47 mmol) of a dendrimer bromide synthesized according to (1990)), 46 mg (0.46 mmol) of potassium carbonate, 50 mg of 18-crown-6-ether, and 80 mL of THF were placed in a 100 mL three-necked flask. Refluxed for 10 days. Thereafter, chloroform was added, the organic layer was washed with water and brine, dried over anhydrous sodium sulfate, and the solvent was distilled off. Further purified by preparative in liquid chromatography preparative gel filtration-type fraction, compounds with 35% crude yield ▲ 5 was obtained ▼ a _{(C 516 H 516 Br 2 N} 4 ZnO 124) ( formula (6)) .
[0057]
[Chemical 8]

[0058]
As a result of mass spectrometry (MALDI-TOF-MS) of the obtained compound (5), the molecular weight was estimated to be 9001 (calculated from the chemical formula was 8963).
[0059]
Further, when ¹ H-NMR measurement (400 MHz) of compound (2) was carried out using CDCl ₃ as a solvent, chemical shift δ (ppm) = 9.35 (4H, brs, H _b ), 8.68 (4H, brs, H _{a), 6.20-6.63 (186H, m} , benzene ring), 4.70 (124H, m, CH 2 O), 3.56 (196H, s, is the spectrum peak OMe) is observed was obtained. The description in parentheses is as described above, and H _a and H _b represent H bonded to carbon at the positions indicated by a and b in the compound (5) in the formula (6).
[0060]
Furthermore, the ultraviolet-visible absorption spectrum of compound (5) was measured using CHCl ₃ as the solvent, and as a result, the maximum absorption wavelength λmax (nm) was 608,565,431.
[0061]
Next, under a nitrogen atmosphere, 150 mg (17 mmol) of the compound (5) obtained above, 10 mg of palladium catalyst, and 10 mg of copper iodide are placed in a 100 mL three-necked flask and dissolved in 80 mL of dry THF. Triethylamine (0.1 mL) and trimethylsilyl (TMS; Si (CH ₃ ) ₃ ) acetylene (0.1 mL) were added, and the mixture was refluxed for 20 hours. Thereafter, the obtained product was washed with water, dried over anhydrous sodium sulfate, fractionated and purified by column chromatography, and compound (6) (C ₅₂₆ H) was obtained in a yield of 82 mg (yield 55%). ₅₃₄ Si ₂ N ₄ ZnO ₁₂₄ ) was obtained (Chemical formula (7)).
[0062]
[Chemical 9]

[0063]
As a result of mass spectrometry (MALDI-TOF-MS) of the obtained compound (6), the molecular weight was estimated to be 9002 (calculated from the chemical formula was 8999).
[0064]
Further, when ¹ H-NMR measurement (400 MHz) of Compound (2) was performed using CDCl ₃ as a solvent, chemical shift δ (ppm) = 9.58 (4H, brs, H _b ), 8.91 (4H, brs, H _{a), 6.80-6.25 (186H, m} , benzene ring), 4.81 (124H, m, CH 2 O), 3.64 (192H, s, OMe), 0.52 (18H, s, spectrum peaks TMS) is observed Obtained. The description in parentheses is as described above.
[0065]
Furthermore, the ultraviolet-visible absorption spectrum of compound (5) was measured using CHCl ₃ as the solvent, and as a result, the maximum absorption wavelength λmax (nm) = 621,571,437.
[0066]
The TMS group of compound (5) obtained by the above procedure is removed with tetrabutylammonium fluoride, and an oxidative coupling reaction is carried out in the presence of copper acetate and pyridine, whereby compound (5) is triple bonded. As a result, a chain of molecular wires was obtained.
[0067]
【The invention's effect】
As described above, the molecular wire of the present invention is obtained by introducing a bulky substituent such as a dendrimer which is not a conjugated π-electron system into a conjugated molecule having a conjugated structure by a π-electron system.
[0068]
Therefore, a molecular wire in which a conjugated molecule is covered with a dendrimer can be obtained, so that the diameter of the molecular wire can be increased. In addition, the molecular wire is difficult to bend, and it is possible to provide a rigid molecular wire having a linear structure.
[0069]
As a result, when a molecular electronic device, an electrode, or the like is coupled with the molecular wire, it is easy to wire to the target position, and the molecular wire stretched around the molecular electronic device, the electrode, etc. is scanned by a scanning probe microscope. There is an effect that it is possible to confirm that the wiring is formed at a desired position. In addition, the π-electron part of the conjugated molecule is blocked from surrounding molecules and electrodes due to the presence of dendrimers, making it less susceptible to unnecessary electronic interference, preventing leakage of electrons to the outside and oxidation of the conjugated molecule. There is an effect that it can be prevented.
[Brief description of the drawings]
FIG. 1 shows a molecular wire in the present invention.
FIG. 2 is a cross-sectional view of a field effect transistor using the molecular wire of the present invention.
FIGS. 3A to 3C are structural formulas of a conventional molecular wire.
[Explanation of symbols]
1 molecular wire 2 dendrimer 3 conjugated molecule

Claims (3)

A molecular wire composed of conjugated molecules having conjugation by a π-electron system,
The conjugated molecule has a dendrimer as a substituent ,
The following formula (1)

A molecular wire having a repeating structure represented by (M is a metal element, R ₁ and R ₂ are each a hydrocarbon group, and X _{1 to} X ₄ are each a dendrimer) .   2. The molecular wire according to claim 1, wherein the conjugated molecule is composed of a series of porphyrin compounds. A dendrimer is introduced into a π-electron molecule, and the π-electron molecule introduced with the dendrimer is bonded to each other,
The following formula (2)

(M is a metal element, R ₁ and R ₂ are each a hydrocarbon group, X _{1 to} X ₄ are dendrimers, and Y ₁ and Y ₂ are each an arbitrary substituent) The manufacturing method of the molecular wire characterized by couple | bonding by coupling reaction .

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