Triplet State Baird Aromaticity in Macrocycles: Scope, Limitations, and Complications.
Triplet State Baird Aromaticity in Macrocycles: Scope, Limitations, and Complications.
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DOI：
10.1021/acs.jpca.0c08926
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发表时间：
2021-01-21
期刊：
影响因子：
--
通讯作者：
Ottosson H
中科院分区：
文献类型：
--
作者：
Ayub R;El Bakouri O;Smith JR;Jorner K;Ottosson H
4 n π电子环状分子在第一ππ* 三重态（T1）的芳香性，称为Baird芳香性，在过去的十年中得到了越来越多的关注。在这里，我们探索计算的限制T1状态Baird芳香性的大环化合物，[n]CM的，这是四个不同的单环（M =对亚苯基（PP），2，5-连接呋喃（FU），1，4-连接环己-1，3-二烯（CHD），和1，4-连接环戊二烯（CPD））的环状低聚物。我们努力得到对各种DFT泛函通用的结论，尽管对于在其主要共轭路径中具有多达20个π电子的大环，我们发现当基于UB 3LYP over UM 06 -2X和UCAM-B3 LYP几何时，对于它们的T1态，在正则UCCSD（T）和近似DLPNO-UCCSD（T）水平上的单点能量最低。这一发现是在对比什么以前已经观察到的电子基态的扩展卟啉。然而，无论功能，大环与2，5-连接的呋喃（[n]CFU的）保留贝尔德芳香性，直到大于那些由其他三个单核组成的n。此外，当基于芳香性的几何、电子和能量方面时，具有特定n的3[n]CFU比类似的3[n]CPP具有更强的Baird芳香性，而磁性指数则相反。为了构建大的T1态Baird-芳香族[n]CM，设计应该是这样的，即大环周长的T1态Baird芳香性在具有一个或几个单环的局部闭壳层Hückel芳香性和半定域三重态双自由基特征的情况下占主导地位。在S 0中具有比苯低的Hückel芳香性的单体（例如，呋喃）是优选的。结构限制，例如，亚甲基桥也是获得较大Baird芳族大环的途径。最后，通过使用Zilberg-Haas描述的T1状态的芳香性，我们揭示了类似的Hückel芳香性的相应的闭壳双作用，但观察到更强的Hückel芳香性的大环双作用比Baird芳香性的中性大环的T1状态。
The aromaticity of cyclic 4nπ-electron molecules in their first ππ* triplet state (T1), labeled Baird aromaticity, has gained growing attention in the past decade. Here we explore computationally the limitations of T1 state Baird aromaticity in macrocyclic compounds, [n]CM’s, which are cyclic oligomers of four different monocycles (M = p-phenylene (PP), 2,5-linked furan (FU), 1,4-linked cyclohexa-1,3-diene (CHD), and 1,4-linked cyclopentadiene (CPD)). We strive for conclusions that are general for various DFT functionals, although for macrocycles with up to 20 π-electrons in their main conjugation paths we find that for their T1 states single-point energies at both canonical UCCSD(T) and approximative DLPNO-UCCSD(T) levels are lowest when based on UB3LYP over UM06-2X and UCAM-B3LYP geometries. This finding is in contrast to what has earlier been observed for the electronic ground state of expanded porphyrins. Yet, irrespective of functional, macrocycles with 2,5-linked furans ([n]CFU’s) retain Baird aromaticity until larger n than those composed of the other three monocycles. Also, when based on geometric, electronic and energetic aspects of aromaticity, a 3[n]CFU with a specific n is more strongly Baird-aromatic than the analogous 3[n]CPP while the magnetic indices tell the opposite. To construct large T1 state Baird-aromatic [n]CM’s, the design should be such that the T1 state Baird aromaticity of the macrocyclic perimeter dominates over a situation with local closed-shell Hückel aromaticity of one or a few monocycles and semilocalized triplet diradical character. Monomers with lower Hückel aromaticity in S0 than benzene (e.g., furan) that do not impose steric congestion are preferred. Structural confinement imposed by, e.g., methylene bridges is also an approach to larger Baird-aromatic macrocycles. Finally, by using the Zilberg–Haas description of T1 state aromaticity, we reveal the analogy to the Hückel aromaticity of the corresponding closed-shell dications yet observe stronger Hückel aromaticity in the macrocyclic dications than Baird aromaticity in the T1 states of the neutral macrocycles.
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影响因子：
4.1
作者：
Dai, Chenshu;Chen, Dandan;Zhu, Jun
通讯作者：
Zhu, Jun
影响因子：
4.4
作者：
BECKE, AD
通讯作者：
BECKE, AD
影响因子：
4.6
作者：
Casademont-Reig, Irene;Ramos-Cordoba, Eloy;Matito, Eduard
通讯作者：
Matito, Eduard
影响因子：
5.2
作者：
Fallah-Bagher-Shaidaei, H;Wannere, CS;Schleyer, PV
通讯作者：
Schleyer, PV
影响因子：
2.9
作者：
Aihara, Jun-ichi;Nakagami, Yuto;Makino, Masakazu
通讯作者：
Makino, Masakazu