Novel applications of functionalized 2,1,3-benzothiadiazoles for coordination chemistry and crystal engineering

• Published in: RSC advances Vol. 4; no. 54; pp. 28309 - 28316
• Main Authors: Bashirov, Denis A., Sukhikh, Taisiya S., Kuratieva, Natalia V., Chulanova, Elena A., Yushina, Irina V., Gritsan, Nina P., Konchenko, Sergey N., Zibarev, Andrey V.
• Format: Journal Article
• Language: English
• Published: 01.01.2014
• Subjects: Coordination compounds; Crystal structure; Crystals; Formations; Ligands; Mathematical analysis; Nuclear magnetic resonance; Organic solids
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/c4ra03342f

Two novel applications of functionalized 2,1,3-benzothiadiazoles for metal coordination chemistry and crystal engineering of organic solids are presented. 4-Amino-2,1,3-benzothiadiazole (1) forms a 2 : 1 complex with ZnCl sub(2) (complex 2) and a 1 : 1 complex with 4-nitro-2,1,3-benzothiadiazole (3) (complex 4). The structures of compounds 1-4 were confirmed by single-crystal X-ray diffraction and studied by UV-Vis and IR spectroscopy, and DFT and QTAIM calculations. Complex 2 is the first structurally defined Zn complex with 2,1,3-benzothiadiazole ligands. In this complex, both molecules 1 are coordinated to Zn only by amino groups, thus revealing a novel type of coordination of this ligand to the metal center. According to super(1)H NMR data, complex 2 dissociates in CHCl sub(3), THF or DMSO solutions. There are only a few examples of similar complexes, which are also considered to dissociate in solutions. In crystalline complex 4, molecules 1 and 3 form infinite alternating pi -stacks connected by lateral S...N interactions between the neighboring stacks. Intermolecular S...N interactions are also observed in the crystals of individual 1 and 3 but the packing motifs are different from those in 4. DFT calculations predict a small charge transfer (CT, similar to 0.02e at B97-D3 level) from 1 to 3 upon the formation of 4, which therefore is an unprecedented CT complex where both donor and acceptor moieties are the derivatives of the 2,1,3-benzothiadiazole ring system. This finding creates some new prospects for the crystal engineering of organic solids. Crystalline complex 4 is characterized by an intense CT absorption band with a maximum at similar to 550 nm. However, according to DFT and QTAIM calculations the complex is weakly bonded and its formation is not observed in CH sub(2)Cl sub(2) solution with super(1)H NMR and UV-Vis techniques.