Direct investigation of chalcogen bonds by multinuclear solid-state magnetic resonance and vibrational spectroscopy

• Published in: Physical chemistry chemical physics : PCCP 2020-02, Vol.22 (7), p.3817-3824
• Main Authors: Kumar, Vijith, Xu, Yijue, Leroy, César, Bryce, David L
• Format: Article
• Language: English
• Subjects: Benzene; Chalcogen bonds; Chemical equilibrium; Crystal structure; Crystallography; Density functional theory; Diagnostic systems; Donors (electronic); Electronic structure; Infrared spectroscopy; Molecular orbitals; NMR; Nuclear magnetic resonance; Organic chemistry; Selenium; Single crystals; Solid state; Spectrum analysis; Tensors
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c9cp06267j

We report a multifaceted experimental and computational study of three self-complementary chalcogen-bond donors as well as a series of seven chalcogen bonded cocrystals. Bis(selenocyanatomethyl)benzene derivatives were cocrystallized with various halide salts (Bu 4 NCl, Bu 4 NBr, Bu 4 NI) and nitrogen-containing Lewis bases (4,4′-bipyridine and 1,2-di(4-pyridyl)ethylene). Three new single-crystal X-ray structures are reported. 77 Se solid-state nuclear magnetic resonance spectroscopic study of a series of cocrystals establishes correlations between the NMR parameters of selenium and the local ChB geometry. For example, the 77 Se isotropic chemical shift generally decreases on cocrystal formation. Diagnostic 13 C chemical shifts are also described. In addition, all the chalcogen bonded cocrystals and pure tectons are investigated by Raman and IR spectroscopy techniques. Characteristic red shifts of the NC-Se stretching band upon cocrystal formation on the order of 10 to 20 cm −1 are observed, which provides a distinct signature of the chalcogen bond involving selenocyanates. The 125 Te chemical shift tensor and X-ray structure of chalcogen-bonded tellurocyanatomethylbenzene are also reported. Insights into the connection between the electronic structure of the chalcogen bond and the experimentally measured 77 Se chemical shift tensors are afforded through a natural localized molecular orbital density functional theory analysis. For the systems studied here, the lack of a very strong a correlation between experimental and DFT-computed 77 Se chemical shift tensors leads to the conclusion that many structural features likely influence their ultimate values; however, computations on model systems reveal that the ChB alone produces consistent and predictable effects ( e.g. , the chalcogen chemical shift decreases as the chalcogen bond is shortened). We report a multifaceted experimental and computational study of three self-complementary chalcogen-bond donors as well as a series of seven chalcogen bonded cocrystals.