N,N'-Diaryl-Sulfurdiimides are Strongly Redox Tuned

The synthesis and extensive characterization of nine aryl sulfur diimides (SDIs, Ar-NSN-Ar) are presented with a robust computational and experimental investigation of the fundamental properties of these important members of the thiazyl family of compounds, with particular attention paid to their highly tunable electrochemical behaviour. This is the first work to undertake a systematic comparison of the electrochemical profiles of a coherent series of SDIs to demonstrate and quantify the response of their reduction potentials to substituent electron-donating and -withdrawing properties. This effect is found to be not only exceptionally strong, but also correlates very closely with computed orbital energies. Electron paramagnetic resonance spectroscopy is used to determine the nature, localization, and qualitative lifetimes of the radical anions of SDIs. This work also addresses significant misconceptions about physical properties of SDIs. Experimental data and modern computational methods are employed to provide a resolute answer to the long-standing contention of the solution-state conformations of SDIs, and to correct historical mistakes in the assignment of infrared spectroscopic data. High-quality crystal structures of all SDIs in this work showcase the utility of the recently introduced structural refinement software NoSpherA2, enabling full anisotropic refinement of H-atoms with accurate C-H bond lengths.

Tetraimido Sulfuric Acid H2 S(NtBu)4 -Valence Isoelectronic to H2 SO4

The valence isoelectronic imido analog H2 S(NtBu)4 (1) of sulfuric acid H2 SO4 was synthesized, isolated, and characterized by NMR spectroscopy and high-resolution X-ray charge density analysis. The latter reveals strongly polarized Sδ+ -Nδ- bonds with virtually no double bond character. The easy-to-polarize S-N bonds are an advantageous and versatile feature of sulfur nitrogen ligands, which enables them to adapt to different electron requirements of various metal cations.

Embracing chemical and structural diversity with UCONGA: A universal conformer generation and analysis program

Molecular properties depend on molecular structure, so the first step in any computational chemistry investigation is to generate all thermally accessible conformers. Typically it is necessary to make a trade-off between the number of conformers to be explored and the accuracy of the method used to calculate their energies. Ab initio potential energy surface scans can, in principle, be applied to any molecule, but their conformational cost scales poorly with both molecular size and dimensionality of the search space. Specialized conformer generation techniques rely on parameterized force fields and may also use knowledge-based rules for generating conformers, and are typically only available for drug-like organic molecules. Neither approach is well-suited to generating or identifying chemically sensible conformers for larger non-organic molecules. The Universal CONformer Generation and Analysis (UCONGA) program package fills this niche. It requires no parameters other than built-in atomic van der Waals radii to generate comprehensive ensembles of sterically-allowed conformers, for molecules of arbitrary composition and connectivity. Analysis scripts are provided to identify representative structures from clusters of similar conformers, which may be further refined by subsequent geometry optimization. This approach is particularly useful for molecules not described by parameterized force fields, as it minimizes the number of computationally intensive ab initio calculations required to characterize the conformer ensemble. We anticipate that UCONGA will be particularly useful for computational and structural chemists studying flexible non-drug-like molecules.