Chen Pangkuan, Marshall Ariel S, Chi San-Hui, Yin Xiaodong, Perry Joseph W, Jäkle Frieder
Department of Chemistry, Rutgers University Newark, Newark, NJ, 07102 (USA).
School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA, 30332-0400 (USA).
Chemistry. 2015 Dec 7;21(50):18237-47. doi: 10.1002/chem.201502268. Epub 2015 Oct 30.
A set of monodisperse bent donor-acceptor-donor-type conjugated borazine oligomers, BnNn+1 (n=1-4), incorporating electron-rich triarylamine donor and electron-deficient triarylborane acceptor units has been prepared through an iterative synthetic approach that takes advantage of highly selective silicon-boron and tin-boron exchange reactions. The effect of chain elongation on the electrochemical, one- and two-photon properties and excited-state photodynamics has been investigated. Strong intramolecular charge transfer (ICT) from the arylamine donors to boryl-centered acceptor sites results in emissions with high quantum yields (Φfl >0.5) in the range of 400-500 nm. Solvatochromic effects lead to solvent shifts as large as ∼70 nm for the shortest member (n=1) and gradually decrease with chain elongation. The oligomers exhibit strong two-photon absorption (2PA) in the visible spectral region with 2PA cross sections as large as 1410 GM (n=4), and broadband excited-state absorption (ESA) attributed to long-lived singlet-singlet and radical cation/anion absorption. The excited-state dynamics also show sensitivity to the solvent environment. Electrochemical observations and DFT calculations (B3LYP/6-31G*) reveal spatially separated HOMO and LUMO levels resulting in highly fluorescent oligomers with strong ICT character. The BnNn+1 oligomers have been used to demonstrate the detection of cyanide anions with association constants of log K>7.
通过利用高度选择性的硅硼和锡硼交换反应的迭代合成方法，制备了一组单分散的弯曲供体-受体-供体型共轭硼嗪低聚物BnNn+1（n = 1 - 4），其包含富电子的三芳基胺供体和缺电子的三芳基硼烷受体单元。研究了链增长对电化学、单光子和双光子性质以及激发态光动力学的影响。从芳胺供体到硼中心受体位点的强分子内电荷转移（ICT）导致在400 - 500 nm范围内具有高量子产率（Φfl > 0.5）的发射。溶剂化显色效应导致最短成员（n = 1）的溶剂位移高达约70 nm，并随着链增长而逐渐减小。这些低聚物在可见光谱区域表现出强双光子吸收（2PA），双光子吸收截面高达1410 GM（n = 4），以及归因于长寿命单重态-单重态和自由基阳离子/阴离子吸收的宽带激发态吸收（ESA）。激发态动力学也显示出对溶剂环境的敏感性。电化学观察和DFT计算（B3LYP/6 - 31G*）揭示了空间分离的HOMO和LUMO能级，从而产生具有强ICT特征的高荧光低聚物。BnNn+1低聚物已被用于证明对氰化物阴离子的检测，缔合常数log K > 7。
