电子亲和度的Al ((n) 集群和多倍芳香度的方形结构Al4 ((2-) 的电子亲和度
Chang-Guo Zhan1, Fang Zheng, David A Dixon
1Department of Medicine, College of Physician & Surgeons, Columbia University, New York, New York 10032, USA. Chang-Guo.Zhan@pnl.gov
像Al(4)(2-) 这样的团中的芳香性得到了高级计算的证实,揭示了超出简单pi电子的新"多倍"芳香性. 这挑战了传统的观点,并提出了新的方法来理解分子中的化学结合.
科学领域:
- * 计算化学 计算机化学
- * * 量子化学 量子化学
- * 材料科学 材料科学
背景情况:
- * 芳香性,传统上与平面有机分子和4n+2移位的pi电子有关,解释了异常的稳定性.
- *最近的实验表明全金属MAl(4)(-) 系统中的芳香性,特别是方形平面Al(4)(2-) 单元.
- *Al(4)(2-) 结构是新一类芳香无机分子的原型.
研究的目的:
- *以计算方式研究团离子的电子结构和芳香度,特别是为n=0-4.0的Al (n) (n) (n) (n) -).
- * 确定这些团的电子亲和度,并与实验数据进行比较.
- *阐明Al(4)(2-) 和Al(3)(-) 中的芳香性质的性质,并提出分析非局部化结合的一般化框架.
主要方法:
- *高层次的ab initio量子化学计算,特别是CCSD(T) /aug-cc-pVxZ推算到完整的基础设置极限.
- * 对Al (n) (n) (-) 集群 (n=0-4) 的电子亲和度的计算.
- *对共振能量和结合系统进行分析,以描述芳香度.
主要成果:
- *对Al (n) (n) - (n=0-4) 的计算电子亲和度与实验值非常一致.
- *Al(4)(2-) 呈现出显著的共振能量,证实了它对Al(4) 的芳香性和稳定性.
- *Al(4)(2-) 显示出异常的"多重"芳香度,由三个独立的非局部化结合系统产生的,每个系统都符合4n+2规则,与 (C(6) H(6) 的单一pi芳香度不同.
- *Al(3)(-) 显示了2倍的芳香度 (pi加sigma),具有9个潜在的Kekulé样结构.
结论:
- *Al(4)(2-) 的芳香度与等有机分子的芳香度有着根本的不同,其特点是具有多个同时非局部化的结合系统.
- * 提出了一种分析非局部化化学键的通用方法,适用于有机和无机系统.
- * 分子芳香性可能来自于同时满足电子计数规则的多个独立的非局部化结合系统,导致"多重"芳香性.
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