Exploring the Coordination Capabilities of a Family of Flexible Benzotriazole-Based Ligands Using Cobalt(II) Sources

In this study we focus on the coordination chemistry of a family of three flexible benzotriazole-based ligands (L¹–L³) using cobalt­(II) salts. Our efforts have resulted in the formation of 10 novel compounds, formulated as [Co₂(L¹)₂Cl₄]­·2MeCN (1·2MeCN), Co₂(L¹)₂Br₄ (2), [Co­(L²)­Cl₂]­·MeCN (3·MeCN), Co­(L²)­Cl₂ (4), [Co₂(L²)₂Br₄]­·2MeCN (5·2MeCN), [Co­(L²)₂(NO₃)₂]­·2MeCN (6·2MeCN), [Co₂(L³)₂Cl₄]­·2MeCN (7·2MeCN), Co₂(L³)₂Cl₄ (8), Co₂(L³)₂Br₄ (9), and Co­(L³)₂(NO₃)₂ (10). The structures have been well characterized through X-ray crystallography, Fourier transform-infrared spectroscopy, electrospray ionization mass spectrometry, powder X-ray diffraction, elemental analysis, and thermogravimetric analysis studies. The compounds show a large structural variety depending on synthetic parameters (ratio, temperature, and metal salt) and the ligand selection (various conformations in each ligand). When tuned appropriately, these factors drastically affect dimensionality, metal geometry, and the nuclearity of the final product, resulting in a range of zero-dimensional dimers (1, 3, 5, 8, 9), one-dimensional (2, 7, 10), and two-dimensional (4, 6) coordination polymers. A temperature-induced single-crystal-to-single-crystal transformation of compound 3–4 is additionally reported. The magnetic properties of representative compounds (4, 7, 9) are subject to large changes with only minor structural variations, suggesting that tetrahedral Co­(II) nodes in coordination polymers or metal–organic frameworks could function as sensitive reporters of small changes in the local environment.