Three symmetrically and three unsymmetrically substituted cibalackrot (7,14-diphenyldiindolo[3,2,1-de:3′,2′,1′-ij][1,5]naphthyridine-6,13-dione, 1) dyes carrying two derivatized phenyl rings have been synthesized as candidates for molecular electronics and especially for singlet fission, a process of interest for solar energy conversion. Solution measurements provided singlet and triplet excitation energies and fluorescence yields and lifetimes; conformational properties were analyzed computationally. The molecular properties are close to ideal for singlet fission. However, crystal structures, obtained by single-crystal X-ray diffraction (XRD), are rather similar to those of the polymorphs of solid 1, in which the formation of a charge-separated state followed by intersystem crossing, complemented with excimer formation, outcompetes singlet fission. Results of calculations by the approximate SIMPLE method suggest which ones among the solid derivatives are the best candidates for singlet fission, but it appears difficult to change the crystal packing in a desirable direction. We also describe the preparation of three specifically deuteriated versions of 1, expected to help sort out the mechanism of fast intersystem crossing in its charge-separated state.

中文翻译：

---

苯基取代的 Cibalackrot 衍生物：合成、结构和溶液光物理学

三个对称和三个不对称取代的 cibalackrot (7,14-diphenyldiindolo[3,2,1- de :3',2',1'- ij ][1,5]naphthyridine-6,13-​​dione, 1 ) 染料携带已经合成了两个衍生苯环作为分子电子学的候选者，特别是单线态裂变，这是一种对太阳能转换感兴趣的过程。溶液测量提供了单线态和三线态激发能量以及荧光产量和寿命；通过计算分析了构象特性。分子特性接近单线态裂变的理想值。然而，通过单晶 X 射线衍射 (XRD) 获得的晶体结构与固体1的多晶型物非常相似，其中电荷分离态的形成随后是系间交叉，辅以准分子形成，胜过单线态裂变。近似 SIMPLE 方法的计算结果表明，固体衍生物中哪些是单线态裂变的最佳候选者，但似乎很难在理想的方向上改变晶体堆积。我们还描述了1的三个特别氘化版本的制备，预计有助于理清电荷分离状态下快速系间穿越的机制。