Amending the Anisotropy Barrier and Luminescence Behavior of Heterometallic Trinuclear Linear [MIILnIIIMII] (LnIII=Gd,Tb, Dy; MII=Mg/Zn) Complexes by Change from Divalent Paramagnetic to Diamagnetic Metal Ions

The sequential reaction of a multisite coordinating compartmental ligand [2‐(2‐hydroxy‐3‐(hydroxymethyl)‐5‐methylbenzylideneamino)‐2‐methylpropane‐1,3‐diol] (LH₄) with appropriate lanthanide salts followed by the addition of [Mg(NO₃)₂] ? 6 H₂O or [Zn(NO₃)₂] ? 6 H₂O in a 4:1:2 stoichiometric ratio in the presence of triethylamine affords a series of isostructural heterometallic trinuclear complexes containing [Mg₂Ln]³⁺ (Ln=Dy, Gd, and Tb) and [Zn₂Ln]³⁺ (Ln=Dy, Gd, and Tb) cores. The formation of these complexes is demonstrated by X‐ray crystallography as well as ESI‐MS spectra. All complexes are isostructural possessing a linear trimetallic core with a central lanthanide ion. The comprehensive studies discussed involve the synthesis, structure, magnetism, and photophysical properties on this family of trinuclear [Mg₂Ln]³⁺ and [Zn₂Ln]³⁺ heterometallic complexes. [Mg₂Dy]³⁺ and [Zn₂Dy]³⁺ show slow relaxation of the magnetization below 12 K under zero applied direct current (dc) field, but without reaching a neat maximum, which is due to the overlapping with a faster quantum tunneling relaxation mediated through dipole–dipole and hyperfine interactions. Under a small applied dc field of 1000 Oe, the quantum tunneling is almost suppressed and temperature and frequency dependent peaks are observed, thus confirming the single‐molecule magnet behavior of complexes [Mg₂Dy]³⁺ and [Zn₂Dy]³⁺.     

Brownian Bridges for Late Time Asymptotics of KPZ Fluctuations in Finite Volume

Height fluctuations are studied in the one-dimensional totally asymmetric simple exclusion process with periodic boundaries, with a focus on how late time relaxation towards the non-equilibrium steady state depends on the initial condition. Using a reformulation of the matrix product representation for the dominant eigenstate, the statistics of the height at large scales is expressed, for arbitrary initial conditions, in terms of extremal values of independent standard Brownian bridges. Comparison with earlier exact Bethe ansatz asymptotics leads to explicit conjectures for some conditional probabilities of non-intersecting Brownian bridges with exponentially distributed distances between the endpoints.     

Reactivity of Bispropargyl Sulfones under Basic Conditions: Interplay Between Garratt–Braverman and Schmittel/Myers–Saito Cyclization Pathway

The preference for Garratt–Braverman (GB) over Myers–Saito (MS) and Schmittel (SCM) cyclizations has recently been demonstrated in sulfones capable of undergoing all three of the processes. As the GB cyclization is a self-quenching process, there is a need to change the selectivity to the non-self-quenching MS or SCM pathway so as to enhance the DNA-cleaving efficiency that operates through the radical-mediated process. Herein we report a conformational constraint-based strategy developed by using computations (M06-2X/6-31+G*) to switch the selectivity from GB to MS/SCM pathway which also results in greater DNA-cleavage activity. The preference for GB could be brought back by easing the constraint with the help of spacers.     

Pt Nanoparticles Supported on a Dynamic Boronate Ester-Based G-quadruplex Hydrogel as a Nanoreactor

Herein, we have reported a dynamic boronic ester mediated guanosine (G) based G-quadruplex hydrogel as an ideal template for in situ and ‘green chemical’ approach for the synthesis and stabilization of Pt NPs. ¹¹B NMR and FT-IR spectra reveal the formation of dynamic boronate ester bonds. The TEM images of the G-quadruplex hydrogel reveal entangled three-dimensional (3D) crosslink nanofibrillar networks with average diameter of 20 nm. Similarly, AFM images of the hydrogel show dense nanofibrillar assembly with an average height of 6 nm. The in situ generated Pt NPs have been characterized using TEM and XPS techniques. The average size of the nanofiber supported Pt NPs is 1.5 nm. The Pt NPs embedded G-quadruplex hydrogel shows better mechanical stiffness than the native hydrogel as the storage modulus (G′) increases to 2250 Pa from 317.08 Pa after the in situ generation of Pt NPs. Furthermore, G-quadruplex hydrogel supported Pt NPs have been used as a catalytic system for hydrogenation reaction of different aromatic nitro compounds in aqueous medium. The use of G-quadruplex molecular system as a template for the synthesis and stabilization of metal NPs would be an interesting area of research.     

Rejuvenating the Geometric Electrocatalytic OER Performance of Crystalline Co3O4 by Microstructure Engineering with Sulfate

Despite significant research on its electrocatalytic OER activity, the geometric performance of Co₃O₄ has remained unsatisfactory compared to relatively amorphous Co-based materials. In particular, the activity of Co₃O₄ prepared through annealing always gets inferior compared to its amorphous precursor. This demands the development of synthetic techniques to prepare Co₃O₄ with superior activity as the unpredictable crystal structure of the amorphous materials makes it difficult to understand their structure-activity relationships despite higher geometric activity. In this article, we have shown that incorporation of sulfate in pre-annealed materials plays a pivotal role in boosting the OER activity of annealed Co₃O₄ irrespective of the pre-annealed phase. In contrast to commonly used nitrate or carbonate that leaves the structure upon annealing and renders the resulting Co₃O₄ with poor activity, sulfate remains in the annealed structure due to its thermal stability and causes a dramatic enhancement in the geometric electrocatalytic OER activity of resulting Co₃O₄ compared to the pre-annealed phase. This was due to the “pore-alteration ability” and “crystallization hindrance effect” of sulfate ions that significantly alter the microstructure of the resulting Co₃O₄ during annealing process by dramatically improving the surface area, pore size, and pore volume. Moreover, sulfate incorporation provided structures with considerably higher mesoporosity that is known to be conducive for reactant and product diffusion within the network. The improved textural properties led to better exposure of the catalytic centres to the electrolyte leading to higher geometric OER activity despite identical intrinsic activity of both sulfate free and incorporated Co₃O₄ as confirmed from their specific activities. Further, the Co₃O₄ synthesized by annealing sulfate incorporated precursor was found to be rich with oxygen defects that are known to increase the potency of a material towards electrocatalytic OER. The sulfate ions also etched out in the electrolyte during electrocatalysis leading to complete unblocking of the pores thereby helping in sustaining the high geometric OER activity. To our knowledge, this is the first report where the geometric electrocatalytic OER activity of an annealed Co₃O₄ is significantly better compared to its pre-annealed phase and is in fact comparable to the activity of amorphous Co-hydroxide based compounds.     

(1‐Butyl‐4‐methyl‐pyridinium)[Cu(SCN)2]: A Coordination Polymer and Ionic Liquid

The compound (C₄C₁py)[Cu(SCN)₂], (C₄C₁py=1‐Butyl‐4‐methyl‐pyridinium), which can be obtained from CuSCN and the ionic liquid (C₄C₁py)(SCN), turns out to be a new organic–inorganic hybrid material as it qualifies both, as a coordination polymer and an ionic liquid. It features linked [Cu(SCN)₂]^? units, in which the thiocyanates bridge the copper ions in a μ_1,3‐fashion. The resulting one‐dimensional chains run along the a axis, separated by the C₄C₁py counterions. Powder X‐ray diffraction not only confirms the single‐crystal X‐ray structure solution but proves the reformation of the coordination polymer from an isotropic melt. However, the materials shows a complex thermal behavior often encountered for ionic liquids such as a strong tendency to form a supercooled melt. At a relatively high cooling rate, glass formation is observed. When heating this melt in differential scanning calorimetry (DSC) and temperature‐dependent polarizing optical microscopy (POM), investigations reveal the existence of a less thermodynamically stable crystalline polymorph. Raman measurements conducted at 10 and 100 °C point towards the formation of polyanionic chain fragments in the melt. Solid‐state UV/Vis spectroscopy shows a broad absorption band around 18 870 cm^?1 (530 nm) and another strong one below 20 000 cm^?1 (<500 nm). The latter is attributed to the d(Cu^I)→π*(SCN)‐MLCT (metal‐to‐ligand charge transfer) transition within the coordination polymer yielding an energy gap of 2.4 eV. At room temperature and upon irradiation with UV light, the material shows a weak fluorescence band at 15 870 cm^?1 (630 nm) with a quantum efficiency of 0.90(2) % and a lifetime of 131(2) ns. Upon lowering the temperature, the luminescence intensity strongly increases. Simultaneously, the band around 450 nm in the excitation spectrum decreases.     

Control of Regioselectivity over Gold Nanocrystals of Different Surfaces for the Synthesis of 1,4‐Disubstituted Triazole through the Click Reaction

Gold nanocubes, octahedra, and rhombic dodecahedra were examined for facet‐dependent catalytic activity in the formation of triazoles. Rhombic dodecahedra gave 100 % regioselective 1,4‐triazoles. The product yield was increased by decreasing the particle size. However, a mixture of 1,4‐ and 1,5‐triazoles was obtained in lower yields when cubes and octahedra of similar sizes were used. The lowest Au‐atom density on the {110} surface and largest unsaturated coordination number of surface Au atoms may explain their best catalytic efficiency and product regioselectivity. Various spectroscopic techniques were employed to verify the formation of the Au–acetylide intermediate and establish the reaction mechanism, in which phenylacetylene binds to the Au {110} surface through the terminal‐binding mode to result in the exclusive formation of 1,4‐triazoles. The smallest rhombic dodecahedra can give diverse 1,4‐disubstituted triazoles in good yields by coupling a wide variety of alkynes and organic halides.