Rowshan Ara Begum

Molecular Thioamide ↔ Iminothiolate Switches for Sulfur Mustards

SNS platinum(II) pincer complexes reversibly bind and release the surrogate half sulfur mustard, 2-chloroethyl ethyl sulfide (CEES). The switch-like behavior of the pincers is attributed to a reversible transformation between the thioamide and iminothiolate forms of the pincer skeleton under slightly acidic and basic conditions, respectively. An amide-based palladium(II) pincer complex also binds CEES, as confirmed crystallographically and by NMR.

Chemical Mustard Containment Using Simple Palladium Pincer Complexes: The Influence of Molecular Walls

Six amide-based NNN palladium(II) pincer complexes Pd(L)(CH3CN) were synthesized, characterized, and examined for binding the sulfur mustard surrogate, 2-chloroethyl ethyl sulfide (CEES). The complexes all bind readily with CEES as shown by (1)H NMR spectroscopy in CDCl3. The influence of para-substituents on the two amide phenyl appendages was explored as well as the effect of replacing the phenyl groups with larger aromatic rings, 1-naphthalene and 9-anthracene. While variations of the para-substituents had only a slight influence on the binding affinities, incorporation of larger aromatic rings resulted in a significant size-related increase in binding, possibly due to increasing steric and electronic interactions. In crystal structures of three CEES-bound complexes, the mustard binds through the sulfur atom and lies along the aromatic walls of the side appendages approximately perpendicular to the pincer plane, with increasingly better alignment progressing from phenyl to 1-naphthalene to 9-anthracene.

Proton-Induced Disproportionation of a Ruthenium Noninnocent Ligand Complex Yielding a Strong Oxidant and a Strong Reductant

The complex Ru(II)(NH(3))(2)(o-benzoquinonediimine)Cl(2) undergoes a reversible apparent acid/base reaction, although it has no obvious basic lone pairs. The reaction is a proton-assisted disproportionation yielding an oxidant ([Ru(III)(NH(3))(2)(o-benzoquinonediimine)Cl(2)](+)) and a reductant ([Ru(III)(NH(3))(2)(o-phenylenediamine)Cl(2)](+)). These species were characterized by electrochemistry, ultraviolet-visible light (UV-vis), vibrational (infrared (IR) and Raman), mass and electron paramagnetic resonance (EPR) spectroscopy, and X-ray structural analysis. The reaction is shown to be downhill from an isodesmic calculation. Three different isosbestic interconversions of the parent and product species are demonstrated. The electronic structures of these species were analyzed, and their optical spectra assigned, using density functional theory (DFT) and time-dependent DFT. This disproportionation of a noninnocent ligand complex may be relevant to the application of noninnocent ligands in organometallic catalysis and in the biological milieu.