Homoleptic complexes of isocyano- and diisocyanobiazulenes with a 12-electron, ligand-based redox capacity
Homoleptic complexes of isocyano- and diisocyanobiazulenes with a 12-electron, ligand-based redox capacity
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DOI：
10.1039/d3dt01958f
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发表时间：
2023-07-31
影响因子：
4
通讯作者：
Barybin，Mikhail V.
中科院分区：
文献类型：
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作者：
Connelly，Patrick T.;Applegate，Jason C.;Barybin，Mikhail V.
低聚和聚奥是设计先进功能材料的有吸引力的π共轭结构单元。在本文中，我们证明了将氧化还原非无辜的2，2 ′-二异氰基-6，6 ′-联奥π-连接体（1）的一个或两个异氰化物末端锚定到氧化还原活性[Cr（CO）5]部分提供了方便的分子内氧化还原参考，用于明确地确定6，6 ′-联奥支架经历由还原电位压缩/反转控制的可逆的一步2 e −还原。用六当量的二（η6-萘）铬（0）处理。2-异氰基-1，1 ′，3，3 ′-四乙氧羰基-6，6 ′-联甘菊环（6）或[（OC）5Cr（η1- 2，2 ′-diisocyano-1，1 ′，3，3 ′-tetraethoxycarbonyl-6，6 ′-biazulene）]（11）得到了均配型Cr（0）配合物13和14，（每分子）在温和E1/2下的基于配体的还原容量分别为−1.29 V和−1.15 V（相对于Cp 2Fe 0/+）。整体可逆氧化还原容量从单核配合物13的15 e −变化到七核配合物14的21 e −。后一种“纳米复合物”的直径约为100 μ m。5 nm，具有7个Cr（0）中心和6个2，2 ′-二异氰基-6，6 ′-联奥桥。[（OC）5Cr（2-isocyano-1，1 ′，3，3 ′-tetraethoxycarbonyl-6，6 ′-biazulene）]（7）的X-射线结构表明两个azulenic部分之间的平面角为43.5°。11在Au（111）基底上的自组装提供了11的有机金属单层膜，其特征在于2，2 ′-二异氰基-6，6 ′-联奥连接体的近似直立取向，如椭圆偏振测量和11内C4 v-对称[（-NC）Cr（CO）5]红外报告物的RAIR特征所证明的。值得注意的是，将溶液中11的FTIR光谱与吸附在Au（111）上的11的RAIR光谱进行比较，表明在约100 nm处存在电子耦合。通过2，2 ′-二异氰基-6，6 ′-联奥桥连接的Cr（0）和Au原子之间的距离为2 nm。
Oligo- and polyazulenes are attractive π-conjugated building blocks in designing advanced functional materials. Herein, we demonstrate that anchoring one or both isocyanide termini of the redox non-innocent 2,2′-diisocyano-6,6′-biazulenic π-linker (1) to the redox-active [Cr(CO)5] moiety provided a convenient intramolecular redox reference for unambiguously establishing that the 6,6′-biazulenic scaffold undergoes a reversible one-step 2e− reduction governed by reduction potential compression/inversion. Treatment of bis(η6-naphthalene)chromium(0) with six equiv. of 2-isocyano-1,1′,3,3′-tetraethoxycarbonyl-6,6′-biazulene (6) or [(OC)5Cr(η1-2,2′-diisocyano-1,1′,3,3′-tetraethoxycarbonyl-6,6′-biazulene)] (11) afforded homoleptic Cr(0) complexes 13 and 14 with a 12e− (per molecule) ligand-based reduction capacity at mild E1/2 of −1.29 V and −1.15 V vs. Cp2Fe0/+, respectively. The overall reversible redox capacity varies from 15e− for the mononuclear complex 13 to 21e− for the heptanuclear complex 14. The latter “nanocomplex” has a diameter of ca. 5 nm and features seven Cr(0) centers interlinked with six 2,2′-diisocyano-6,6′-biazulenic bridges. The X-ray structure of [(OC)5Cr(2-isocyano-1,1′,3,3′-tetraethoxycarbonyl-6,6′-biazulene)] (7) indicated a 43.5° interplanar angle between the two azulenic moieties. Self-assembly of 11 on a Au(111) substrate afforded an organometallic monolayer film of 11 featuring approximately upright orientation of the 2,2′-diisocyano-6,6′-biazulenic linkers, as evidenced by ellipsometric measurements and the RAIR signature of the C4v-symmetric [(–NC)Cr(CO)5] infrared reporter within 11. Remarkably, comparing the FTIR spectrum of 11 in solution with the RAIR spectrum of 11 adsorbed on Au(111) suggested electronic coupling at a ca. 2 nm distance between the Cr(0) and Au atoms linked by the 2,2′-diisocyano-6,6′-biazulene bridge.