A panel of peralkylated sulfur–guanidine type bases: Novel pro-ligands for use in biomimetic coordination chemistry

• A family of pre-ligands with both N and S donor functionalities is described.
• The geometries of five members have been optimized by DFT methods.
• The DFT as well as X-ray structures of individual members are compared.

A series of novel hybrid molecules containing sulfur and nitrogen donor functions simultaneously has been synthesized and characterized. Designed for use in biomimetic coordination chemistry, these molecules are expected to act directly or in specific precursor roles as polyfunctional Lewis bases towards metal-based Lewis acids to form complexes with biological relevance. Their principal architecture is based on aliphatic or aromatic backbones connecting guanidine moieties with sulfur-containing thioether or disulfide portions. Based on acyclic tetramethylguanidino units and their cyclic dimethylethyl-substituted counterparts, a panel of forty-six members of this class of compounds are presented here. The associated denticity extends from bidentate (N/S donor sets) and tridentate (N/N/S donor sets) via tetradentate (N/N/S/S donor sets) to pentadentate (N/N/N/S/S donor sets). Five of these novel systems were structurally characterized and subjected to geometry optimizations using density-functional theory (DFT).

The preparation of organic sulfides and disulfides terminated by peralkylated guanidine residues is described. These molecules offer the potential to stabilize bio-relevant metal coordination modes in biomimetic complexes. Selected examples have been characterized by X-ray diffraction and subjected to geometry optimizations by means of DFT calculations.Figure optionsDownload as PowerPoint slide