(E)-5,5′-Di(thiophen-2-yl)-3,3′-bi[thiophen-3(2H)-ylidene]-2,2′-diones—from conspicuous blue impurities to “quasi-metallic” golden-bronze crystals
作者:Nicholas R. Evans、Andrew J. P. White
DOI:10.1039/c3ob40373d
日期:——
(E)-5,5â²-Di(thiophen-2-yl)-3,3â²-bi[thiophen-3(2H)-ylidene]-2,2â²-dione (1a) has caught the eye of several chemists who have encountered it as a trace by-product in a variety of reactions. We report here the first deliberate synthesis of this intense blue dye (λmax 635 nm; εmax 32â400 L cmâ1 molâ1). We prove on the basis of predictions made with TDDFT that 1a has previously been misassigned as a structural isomer and we correct the visible absorption data that was reported. Derivatives of 1a equipped with pentyl (1b) and butylsulfanyl (1c) groups are readily prepared with our divergent synthetic route (3â7% yield over five steps). Crystals of 1b and 1c exhibit an attractive âquasi-metallicâ golden-bronze lustre. This effect is rare in molecular crystals and is observed only with the most intense dyes.
(E)-5,5′-二(噻吩-2-基)-3,3′-双[噻吩-3(2H)-亚甲基]-2,2′-二酮(1a) 引起了多位化学家的关注,他们在各种反应中偶然发现了它作为微量副产物。我们在此报告了这种强烈蓝色染料的首次有意合成(λmax 635 nm; εmax 32,400 L cm⁻¹ mol⁻¹)。我们基于TDDFT的预测证明,1a以前被错误地分配为结构异构体,并对之前报告的可见吸收数据进行了更正。我们采用发散合成路线,方便地制备了配备戊基(1b)和丁基硫醇(1c)基团的1a衍生物(五步的产率为3–7%)。1b和1c的晶体展现出迷人的“准金属”金铜色光泽。这种效果在分子晶体中比较罕见,仅在最强烈的染料中观察到。