The discovery of photoswitchable azobenzene-systems that undergo trans-to-cis photoisomerisation was a milestone in supramolecular chemistry. Such photoswitches have possible applications in data storage, stimuli responsive delivery systems, and molecular machines due to fast and selective switching. However, the light induced cis isomer of azobenzene is rather unstable and reverts thermally and photochemically to the thermodynamically stable trans configuration. We report, for the first time, controlled photoswitching of an azo-naphthalenediimide (azo-NDI) which can be achieved upon binding of fluoride ions through anion-π interaction. This NDI-F–NDI “sandwich” stabilises the cis configuration through the generation of an NDI•− radical anion, and a dianionic, NDI2− species that becomes unusually stable in the cis form. The sandwiched cis form reverts to the trans form only upon decomplexation of F−. A model pollutant was successfully degraded using the photogenerated NDI-F–NDI sandwich. This opens a wide range of applications in molecular and supramolecular nanotechnology.

The tetrapeptide segment LVFF from the central hydrophobic core of amyloid β-peptide, Aβ17-20 , based methacrylate monomer was polymerized via reversible addition-fragmentation chain transfer (RAFT) polymerization to afford well-defined side-chain peptide polymers. The polymer was transformed to carry primary amino groups in the peptide terminals, depicting pH-responsiveness and was further modified to provide amphiphilic graft copolymer-based nanocarriers with pH-triggered dynamic dye release capability. The polymers acquired α-helical conformation guided by Aβ17-20 peptide. Computational studies were performed to investigate the secondary interactions of the peptide-based materials.

A unique electrochemical-and fluorescenceactive molecular switch based on a 1,1′-unsymmetrically substituted ferrocenyl coumarin system has been developed. Upon chemical oxidation of the ferrocene moiety with Fe(ClO 4 ) 3 , the present system displays high fluorescence output through an inhibited photoinduced electron transfer (PET) process and also exhibits slight diminution of emission intensity upon the addition of Hg 2+ . The feasibility of the PET process was further verified by the Weller equation and DFT studies, which indicate that oxidation of ferrocene units in 5 depletes electron population from the HOMO of central ferrocene, and thus the PET process is forbidden and reemergence of fluorescence is observed. Theoretical studies further revealed that charge transfer in the excited state from coumarin-centered orbitals (LUMO+1) to mercury-centered empty orbitals (LUMO) may be attributed to fluorescence quenching upon addition of Hg 2+ ion. The unprecedented combination of Fe 3+ ion, Hg 2+ ion, and sodium L-ascorbate (LAS) has been used to generate a molecular system exhibiting combinational INHIBIT logic operation.

The electrocatalytic performance of transition metal dichalcogenides (TMDs) can be hugely impacted by their phase and electronic structure. In this regard, stabilization of the 1T (metallic) phase is a substantial challenge to attain superior electrocatalytic activity compared to its thermodynamically stable polymorph (2H phase). This report provides a simple approach to introduce the 1T phase into 2H−MoSe2 through heteroatom (Cr3+) doping using a hydrothermal method. 1T/2H−MoSe2 (x Cr) (x=1,2,3 and 5) materials have shown better electrocatalytic HER activities compared to the 2H−MoSe2, especially 2% Cr3+ doped MoSe2 (1T/2H−MoSe2 (2 Cr)) have shown the best catalytic activity. 1T/2H−MoSe2 (2 Cr) exhibits a current density of 20 mA cm−2 at an overpotential of 176 mV, low Tafel slope of 77 mV/dec, high double layer capacitance (Cdl) of 78.3 mF cm−2 and good cyclic stability. The improved electrocatalytic activity of 1T/2H−MoSe2 (2 Cr) could be attributed to the high conductance, high 1T phase content and the greater number of active sites resulting from the introduction of Cr3+ ions into MoSe2. In addition, density functional theory (DFT) studies predict that the introduction of Cr3+ ions into the MoSe2 monolayer increases the conduction electron density in the basal plane at room temperature which in turn supports the generation of additional active sites along the basal plane.

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