Manganese Doped-Nitrogenated Carbon as an Efficient Catalyst for Acidic Electrocatalytic Reduction of CO2

Renewable electricity-driven CO2 electroreduction to value-added chemicals is a feasible approach to alleviate both environmental and energy issues. However, CO2 reduction reaction (CO2RR) systems in alkaline electrolytes are constrained by intrinsic limitations such as salt accumulation that impede further industrialization. Herein, an atomically dispersed Mn doped-nitrogen carbon (AD MnNC) catalyst is developed to electrochemically reduce CO2 to CO in both neutral and acidic media. Benefiting from well-dispersed MnNx sites, the maximum CO Faradaic efficiency (FECO) reaches ≈100% at -0.73 V versus reversible hydrogen electrode (RHE) with CO current density (JCO) of 20.4 mA cm-2 in neutral 0.5 m KHCO3. Due to diminished *H adsorption, AD MnNC achieves a FECO of 85.3% at pH 2.0, effectively suppressing the hydrogen evolution reaction (HER) in an acidic electrolyte. The mechanistic study reveals that AD MnNC accelerates the production of *COOH intermediates through a proton-coupled electron transfer (PCET) pathway and thus promotes CO formation.

Synthesis, Structural Elucidation and Pharmacological Applications of Cu(II) Heteroleptic Carboxylates

Six heteroleptic Cu(II) carboxylates (1-6) were prepared by reacting 2-chlorophenyl acetic acid (L¹), 3-chlorophenyl acetic acid (L²), and substituted pyridine (2-cyanopyridine and 2-chlorocyanopyridine). The solid-state behavior of the complexes was described via vibrational spectroscopy (FT-IR), which revealed that the carboxylate moieties adopted different coordination modes around the Cu(II) center. A paddlewheel dinuclear structure with distorted square pyramidal geometry was elucidated from the crystal data for complexes 2 and 5 with substituted pyridine moieties at the axial positions. The presence of irreversible metal-centered oxidation reduction peaks confirms the electroactive nature of the complexes. A relatively higher binding affinity was observed for the interaction of SS-DNA with complexes 2-6 compared to L¹ and L². The findings of the DNA interaction study indicate an intercalative mode of interaction. The maximum inhibition against acetylcholinesterase enzyme was caused for complex 2 (IC₅₀ = 2 µg/mL) compared to the standard drug Glutamine (IC₅₀ = 2.10 µg/mL) while the maximum inhibition was found for butyrylcholinesterase enzyme by complex 4 (IC₅₀ = 3 µg/mL) compared to the standard drug Glutamine (IC₅₀ = 3.40 µg/mL). The findings of the enzymatic activity suggest that the under study compounds have potential for curing of Alzheimer's disease. Similarly, complexes 2 and 4 possess the maximum inhibition as revealed from the free radical scavenging activity performed against DPPH and H₂O₂.

Structure determination from unindexed powder data from scratch by a global optimization approach using pattern comparison based on cross-correlation functions

A method of ab initio crystal structure determination from powder diffraction data for organic and metal-organic compounds, which does not require prior indexing of the powder pattern, has been developed. Only a reasonable molecular geometry is required, needing knowledge of neither unit-cell parameters nor space group. The structures are solved from scratch by a global fit to the powder data using the new program FIDEL-GO (`FIt with DEviating Lattice parameters - Global Optimization'). FIDEL-GO uses a similarity measure based on cross-correlation functions, which allows the comparison of simulated and experimental powder data even if the unit-cell parameters deviate strongly. The optimization starts from large sets of random structures in various space groups. The unit-cell parameters, molecular position and orientation, and selected internal degrees of freedom are fitted simultaneously to the powder pattern. The optimization proceeds in an elaborate multi-step procedure with built-in clustering of duplicate structures and iterative adaptation of parameter ranges. The best structures are selected for an automatic Rietveld refinement. Finally, a user-controlled Rietveld refinement is performed. The procedure aims for the analysis of a wide range of `problematic' powder patterns, in particular powders of low crystallinity. The method can also be used for the clustering and screening of a large number of possible structure candidates and other application scenarios. Examples are presented for structure determination from unindexed powder data of the previously unknown structures of the nanocrystalline phases of 4,11-difluoro-, 2,9-dichloro- and 2,9-dichloro-6,13-dihydro-quinacridone, which were solved from powder patterns with 14-20 peaks only, and of the coordination polymer dichloro-bis(pyridine-N)copper(II).

Tetra-aqua-bis-(pyridine-3-carbo-nitrile-κN 1)nickel(II) benzene-1,4-di-carboxyl-ate tetra-hydrate

A nickel(II) terephthalate complex, viz. [Ni(C6H4N2)2(H2O)4](O2CC6H4CO2)·4H2O, has been synthesized and studied by single-crystal X-ray diffraction. It crystallizes in the triclinic space group P . The crystal structure shows an approximately octa-hedral coordination environment of the complex with the [Ni(H2O)4(3-NCpy)2]2+ (3-NCpy is pyridine-3-carbo-nitrile) cation associated with four free water mol-ecules and hydrogen bonded to a terephthalate dianion [graph set R 2 2(8)]. The supra-molecular structure of the compound is stabilized by a three-dimensional array of O-H⋯O and O-H⋯N hydrogen bonds, along with π-π stacked pyridine-3-carbo-nitrile rings and C-H⋯O inter-actions.

4-Cyanopyridine complexes [MX2(4-CNpy)x]n (with X = Cl, Br and x = 1, 2): crystal structures, thermal properties and a comparison with [MX2(3-CNpy)x]n complexes

Crystal structures of [MX₂(4-CNpy)_x] with X = Cl and Br, M = Mn, Fe, Co, Ni, Cu, and Zn, and x = 1 and 2 were determined by X-ray powder diffraction. 4-Cyanopyridine can build chain and net structures.

Coordination compounds built up from MIICl2 and 3-cyanopyridine: double chains, single chains and isolated complexes

Crystal structures of [M^IICl₂(3-CNpy)_x], with M = Mn, Fe, Co, Ni, Cu, Zn and x = 1, 2, were determined by X-ray powder diffraction. Surprisingly, 3-cyanopyridine coordinates monodentately only.