Reversible and stable redox behavior of a Pt(II) bis(dithiobenzoate)-type complex attributed to rotaxane-based stabilization

Helic[6]arene-Based Chiral Pseudo[1]rotaxanes and [1]Rotaxanes

Chiral pseudo[1]rotaxanes and [1]rotaxanes constructed from macrocyclic arenes still remain a big challenge mainly owing to the lack of such chiral macrocycles. In this work, a new system of chiral pseudo[1]rotaxanes formed by self-inclusion of helic[6]arene containing amide linked with the terminal tertiary amines was first discovered. Based on an atom-economic stopping strategy, a pair of chiral [1]rotaxanes were conveniently obtained in almost quantitative yields by blocking the pseudo[1]rotaxanes with monobenzyl bromide of tetraphenylethene. The structures of pseudo[1]rotaxanes and [1]rotaxanes were characterized by 2D NMR spectra in solution, combined with DFT calculations. The photophysical properties further revealed the efficient chirality transfer of helic[6]arene to the tetraphenylethene moiety, compared to their unthreaded chiral isomers. The discovery of the chiral pseudo[1]rotaxanes allows for a wide and available synthesis of chiral [1]rotaxanes, and also opening a new avenue to the design of chiral supramolecular materials.

Suppression of Undesirable Isomerization and Intermolecular Reactions of Double Bonds by a Linked Rotaxane Structure

For luminescent materials, the isomerization and intermolecular reactions of their double bonds are often undesirable because they cause a reduction in the luminescence properties of the π-system. Herein, we report a new methodology to simultaneously prevent isomerization and intermolecular reactions by utilizing the steric effect of a linked rotaxane structure. The ring units are covalently linked in order to prevent any undesired shuttling effect from occurring during isomerization. In addition, the insulated structure provides robust optical properties by prevention of intermolecular reactions. Bulky linked rotaxane structures on both sides of the N=N and C=C double bonds suppress E/Z isomerization; photoluminescence quantum yield (PLQY) measurements reveal that this results in suppression of PLQY reduction caused by isomerization. Moreover, an improvement in the stability under light irradiation and air atmosphere is demonstrated.

Electrochemically switchable rotaxanes: recent strides in new directions

Are they still electrifying? Electrochemically switchable rotaxanes are well known for their ability to efficiently undergo changes of (co-)conformation and properties under redox-control. Thus, these mechanically interlocked assemblies represent an auspicious liaison between the fields of molecular switches and molecular electronics. Since the first reported example of a redox-switchable molecular shuttle in 1994, improved tools of organic and supramolecular synthesis have enabled sophisticated new architectures, which provide precise control over properties and function. This perspective covers recent advances in the area of electrochemically active rotaxanes including novel molecular switches and machines, metal-containing rotaxanes, non-equilibrium systems and potential applications.

Electrochemical Characterization of Central Action Tricyclic Drugs by Voltammetric Techniques and Density Functional Theory Calculations

This work details the study of the redox behavior of the drugs cyclobenzaprine (CBP), amitriptyline (AMP) and nortriptyline (NOR) through voltammetric methods and computational chemistry. Results obtained in this study show that the amine moiety of each compound is more likely to undergo oxidation at 1a at E_p1a ≈ 0.69, 0.79, 0.93 V (vs. Ag/AgCl/KClsat) for CBP, AMP and NOR, respectively. Moreover, CBP presented a second peak, 2a at E_p2a ≈ 0.98 V (vs. Ag/AgCl/KClsat) at pH 7.0. Furthermore, the electronic structure calculation results corroborate the electrochemical assays regarding the HOMO energies of the lowest energy conformers of each molecule. The mechanism for each anodic process is proposed according to electroanalytical and computational chemistry findings, which show evidence that the methods herein employed may be a valuable alternative to study the redox behavior of structurally similar drugs.