スピン状態の変化は,ビス・インデニル・クロム・II複合体のステリック・フォースされたリガンド・ローテーションによるものです
Erik D Brady1, Jason S Overby, M Brett Meredith
1Contribution from the Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA.
Journal of the American Chemical Society
|August 9, 2002
まとめ
オーガノクロミウム (II) ビス (II) インデニル (II) 複合体のステリックボールは,リガンドの方向性を変化させ,磁気特性を変化させます. このスピン状態の操作は,磁気的に調整可能な分子への経路を提供します.
科学分野:
- 有機金属化学 有機金属化学
- 無機化学 無機化学とは
- マテリアルサイエンス 材料科学
背景:
- サイクロペンタディエニル環は,通常,移行金属複合体におけるd軌道エネルギーに影響を与えない.
- カーボサイクルのリガンドは,サイクロペンタディエニルとは異なり,そのアラインメントに基づいて磁気特性を変化させることができます.
- 置換されたオーガノクロム (II) ビス (II) インデニル複合体は,これらの効果を研究するためのモデルシステムを提供します.
研究 の 目的:
- インデニルリガンドの回転方向が,オーガノクロミウム複合体の磁性特性にどのように影響するかを調査する.
- リガンド構成とスピン状態の制御における置換剤によるステリック阻害の役割を調査する.
- 金属複合体の磁気行動を調節するために,リガンドの指向が使用できるかどうかを判断する.
主な方法:
- 代用されたリチウムインデニドとクロミウムII) クロリドを用いた単位置換および非置換オーガノクロミウム (II) ビス (II) インデニル) 複合体の合成.
- スピン状態 (高スピン対低スピン) を決定するための磁気感受性測定.
- 構造的形状 (横軸対左軸) と結合距離を明らかにするために,X線微分分析を行います.
- 金属のd軌道とHOMO-LUMOギャップに対するリガンド方向性の電子効果を理解するためのコンピューティングモデリング.
主要な成果:
- モノ置換複合体 ((1-RC(9) H(6)) ((2) Cr) は高スピン (S=4) で,段階的なインデニル構成を採用しています.
- 大量のt-BuまたはSiMeグループを持つ異位複合体 ((1,3-R(2)C(9) H(5)) ((2) Cr) は低スピン (S=2) で,ステリカルに強制されたガッチ形状を採用しています.
- X線 difraktionでは,単位置換複合体における段階的な形状と,非置換複合体における左辺形状の確認がされ,後者のCr-C結合の長さは短かった.
- 計算により,ガウス形状は金属-リガンド軌道混合を増加させ,HOMO-LUMOギャップを大きくし,低スピン状態を好むことが明らかになった.
結論:
- インデニルリガンドのステリックバルクは,インデニルリガンドの回転方向を効果的に制御し,オーガノクロミウム (II) 複合体のスピン状態を決定する.
- 階層から左側のインデニル方向への変更は,電子構造と磁気特性に大きな影響を及ぼします.
- ステリカルに強制されたリガンド回転は,調節可能な磁気特性を有する分子を設計および合成するための実行可能な戦略です.
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