Department of Chemistry, Indian Institute of Technology Indore , Indore 453552, India.
J Org Chem. 2017 Jul 7;82(13):6840-6845. doi: 10.1021/acs.joc.7b00991. Epub 2017 Jun 13.
A series of unsymmetrical and symmetrical push-pull phenothiazines (3-7) were designed and synthesized by the Pd-catalyzed Sonogashira cross-coupling reaction and subsequent [2 + 2] cycloaddition-retroelectrocyclization reaction with tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). The effect of systematic variation of the number and nature of cyano-based acceptor TCNE and TCNQ units on the photophysical, electrochemical, and computational studies was investigated. The single-photon absorption on phenothiazines 3-7 reveals that substitution of 1,1,4,4-tetracyanobutadiene (TCBD) and a cyclohexa-2,5-diene-1,4-diylidene-expanded TCBD unit results in strong intramolecular charge transfer and lowering of the LUMO energy level. The TCBD-linked and cyclohexa-2,5-diene-1,4-diylidene-expanded TCBD-linked phenothiazines 3-7 exhibit multiredox waves. The computational studies on phenothiazines 3-7 exhibit substantial stabilization of the LUMO with the increase in acceptor strength, which results in lowering of the HOMO-LUMO gap.
通过钯催化的 Sonogashira 交叉偶联反应以及随后与四氰乙烯（TCNE）和 7,7,8,8-四氰基对醌二甲烷（TCNQ）的[2+2]环加成-反环化反应，设计并合成了一系列非对称和对称的推-拉吩噻嗪（3-7）。系统研究了基于氰基的受体 TCNE 和 TCNQ 单元数量和性质的变化对光物理、电化学和计算研究的影响。吩噻嗪 3-7 的单光子吸收表明，1,1,4,4-四氰基丁二烯（TCBD）和环己-2,5-二烯-1,4-二亚基扩展 TCBD 单元的取代导致强烈的分子内电荷转移和降低 LUMO 能级。TCBD 连接和环己-2,5-二烯-1,4-二亚基扩展 TCBD 连接的吩噻嗪 3-7 呈现出多氧化还原波。吩噻嗪 3-7 的计算研究表明，随着受体强度的增加，LUMO 得到了很大的稳定，从而降低了 HOMO-LUMO 能隙。
