Synthesis, crystal structure and photophysical properties of 1,4‐bis(1,3‐diazaazulen‐2‐yl)benzene: a new π building block

• Published in: Acta crystallographica. Section C, Structural chemistry Structural chemistry, 2018-02, Vol.74 (2), p.171-176
• Main Authors: Sun, Peili, Zhang, Zongyao, Luo, Hongxia, Zhang, Pu, Qin, Yujun, Guo, Zhi-Xin
• Format: Article
• Language: English
• Subjects: 1,3‐diazaazulene; computational chemistry; crystal structure; DFT calculations; nonlinear optical material; organic functional materials; photophysical properties; π building block
• ISSN: 2053-2296; 2053-2296
• DOI: 10.1107/S2053229617018459

A dimerized 1,3‐diazaazulene derivative, namely 1,4‐bis(1,3‐diazaazulen‐2‐yl)benzene [or 2,2′‐(1,4‐phenylene)bis(1,3‐diazaazulene)], C22H14N4, (I), has been synthesized successfully through the condensation reaction between 2‐methoxytropone and benzene‐1,4‐dicarboximidamide hydrochloride, and was characterized by 1H NMR and 13C NMR spectroscopies, and ESI–MS. X‐ray diffraction analysis reveals that (I) has a nearly planar structure with good π‐electron delocalization, indicating that it might serve as a π building block. The crystal belongs to the monoclinic system. One‐dimensional chains were formed along the a axis through π–π interactions and adjacent chains are stabilized by C—H…N interactions, forming a three‐dimensional architecture. The solid emission of (I) in the crystalline form exhibited a 170 nm red shift compared with that in the solution state. The observed optical bandgap for (I) is 3.22 eV and a cyclic voltammetry experiment confirmed the energy levels of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The calculated bandgap for (I) is 3.37 eV, which is very close to the experimental result. In addition, the polarizability and hyperpolarizability of (I) were appraised for its further application in second‐order nonlinear optical materials. Single‐crystal X‐ray analysis reveals that 1,4‐bis(1,3‐diazaazulen‐2‐yl)benzene has a conjugated structure with 26‐π electrons, indicating promising prospects of serving as a new π building block. In the crystal, the compound forms one‐dimensional chains along the a axis through π–π interactions and adjacent chains are stabilized by C—H…N interactions to form a three‐dimensional architecture.