Lovell Terri C, Colwell Curtis E, Zakharov Lev N, Jasti Ramesh
Department of Chemistry & Biochemistry , Materials Science Institute , University of Oregon , Eugene , Oregon 97403 , USA . Email:
CAMCOR - Center for Advance Materials Characterization in Oregon , University of Oregon , Eugene , Oregon 97403 , USA.
Chem Sci. 2019 Feb 25;10(13):3786-3790. doi: 10.1039/c9sc00169g. eCollection 2019 Apr 7.
[]Cycloparaphenylenes, or "carbon nanohoops," are unique conjugated macrocycles with radially oriented π-systems similar to those in carbon nanotubes. The centrosymmetric nature and conformational rigidity of these molecules lead to unusual size-dependent photophysical characteristics. To investigate these effects further and expand the family of possible structures, a new class of related carbon nanohoops with broken symmetry is disclosed. In these structures, referred to as []cycloparaphenylenes, a single carbon-carbon bond is shifted by one position in order to break the centrosymmetric nature of the parent []cycloparaphenylenes. Advantageously, the symmetry breaking leads to bright emission in the smaller nanohoops, which are typically non-fluorescent due to optical selection rules. Moreover, this simple structural manipulation retains one of the most unique features of the nanohoop structures-size dependent emissive properties with relatively large extinction coefficients and quantum yields. Inspired by earlier theoretical work by Tretiak and co-workers, this joint synthetic, photophysical, and theoretical study provides further design principles to manipulate the optical properties of this growing class of molecules with radially oriented π-systems.
[18]轮烯，即“碳纳米环”，是一类独特的共轭大环化合物，其具有与碳纳米管中类似的径向取向π体系。这些分子的中心对称性质和构象刚性导致了不同寻常的尺寸依赖性光物理特性。为了进一步研究这些效应并扩展可能的结构种类，本文公开了一类具有对称性破缺的新型相关碳纳米环。在这些被称为[18]轮烯的结构中，一个碳 - 碳单键移动了一个位置，以打破母体[18]轮烯的中心对称性质。有利的是，对称性破缺导致较小的纳米环发出明亮的光，这些较小的纳米环由于光学选择规则通常是不发荧光的。此外，这种简单的结构操作保留了纳米环结构最独特的特征之一——具有相对较大消光系数和量子产率的尺寸依赖性发光性质。受Tretiak及其同事早期理论工作的启发，这项联合的合成、光物理和理论研究提供了进一步的设计原则，以操控这类不断发展的具有径向取向π体系的分子的光学性质。
