Editorial of Special Issue “Synthesis and Molecular Applications of Metal-Organic Frameworks (MOFs)”

This Special Issue is dedicated to exploring various approaches and techniques for the preparation and modification of metal–organic frameworks (MOFs), as well as their applications, with a specific focus on molecular research [...

Redox-Induced Aromatic C–H Bond Functionalization in Metal Complex Catalysis from the Electrochemical Point of View

This review generalizes and specifies the oxidizing ability of a number of oxidants used in palladium (Pd)-catalyzed aromatic C–H functionalizations. The redox potentials have been analyzed as the measure of oxidant strength and applied to the reasoning of the efficiency of known reactions where catalytic cycles include cyclometalated palladium complexes (and other organopalladium key intermediates)

Li₃V₂(PO₄)₃ Cathode Material: Synthesis Method, High Lithium Diffusion Coefficient and Magnetic Inhomogeneity

Li3V2(PO4)3 cathodes for Li-ion batteries (LIBs) were synthesized using a hydrothermal method with the subsequent annealing in an argon atmosphere to achieve optimal properties. The X-ray diffraction analysis confirmed the material’s single-phase nature, while the scanning electron microscopy revealed a granular structure, indicating a uniform particle size distribution, beneficial for electrochemical performance. Magnetometry and electron spin resonance studies were conducted to investigate the magnetic properties, confirming the presence of the relatively low concentration and highly uniform distribution of tetravalent vanadium ions (V4+), which indicated low lithium deficiency values in the original structure and a high degree of magnetic homogeneity in the sample, an essential factor for consistent electrochemical behavior. For this pure phase Li3V2(PO4)3 sample, devoid of any impurities such as carbon or salts, extensive electrochemical property testing was performed. These tests resulted in the experimental discovery of a remarkably high lithium diffusion coefficient D = 1.07 × 10−10 cm2/s, indicating excellent ionic conductivity, and demonstrated impressive stability of the material with sustained performance over 1000 charge–discharge cycles. Additionally, relithiated Li3V2(PO4)3 (after multiple electrochemical cycling) samples were investigated using scanning electron microscopy, magnetometry and electron spin resonance methods to determine the extent of degradation. The combination of high lithium diffusion coefficients, a low degradation rate and remarkable cycling stability positions this Li3V2(PO4)3 material as a promising candidate for advanced energy storage applications

Li₃V₂(PO₄)₃/Li₃PO₄ Cathode Materials for Li-Ion Batteries: Synthesis and Characterization

Li3V2(PO4)3/Li3PO4 (LVPO/LPO) composites as cathodes for Li-ion batteries were synthesized by the hydrothermal method and subsequently annealed in an Ar atmosphere. The effect of Li3PO4 content on the crystal structure, morphology and the related magnetic and electrochemical properties of Li3V2(PO4)3/Li3PO4 composites, containing 7.5 wt% and 14 wt% of Li3PO4 (LVPO/LPO-7.5 and LVPO/LPO-14) was investigated. The microstructure and morphology of the obtained composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM); magnetic and electrochemical properties investigations were performed using the electron spin resonance and galvanostatic methods, respectively. It was shown that Li3V2(PO4)3/Li3PO4 composites exhibit a high discharge capacity, good cycle performance (105 and 120 mAh g−1 for the 200th cycle at 1C for LVPO/LPO-7.5 and LVPO/LPO-14, respectively), and insignificant changes in the surface morphology after 200 lithiation/delithiation cycles. Our results demonstrate that the increase in Li3PO4 content led to a decrease in the Li stoichiometry and magnetic inhomogeneity in Li3V2(PO4)3 phase; thus, the improvement in the electrochemical performance of LVPO/LPO composites due to incorporation of Li3PO4 can be attributed to their chemical and magnetic inhomogeneity

Synthetic Tuning of CoII-Doped Silica Nanoarchitecture Towards Electrochemical Sensing Ability

The present work introduces both synthesis of silica nanoparticles doped with CoII ions by means of differently modified microemulsion water-in-oil (w/o) and Stöber techniques and characterization of the hybrid nanoparticles (CoII@SiO2) by TEM, DLS, XRD, ICP-EOS, SAXS, UV-Vis, and UV-Vis/DR spectroscopy and electrochemical methods. The results reveal the lack of nanocrystalline dopants inside the hybrid nanoparticles, as well as no ligands, when CoII ions are added to the synthetic mixtures as CoII(bpy)3 complexes, thus pointing to coordination of CoII ions with Si-O- groups as main driving force of the doping. The UV-Vis/DR spectra of CoII@SiO2 in the range of d-d transitions indicate that Stöber synthesis in greater extent than the w/o one stabilizes tetrahedral CoII ions versus the octahedral ions. Both cobalt content and homogeneity of the CoII distribution within CoII@SiO2 are greatly influenced by the synthetic technique. The electrochemical behavior of CoII@SiO2 is manifested by one oxidation and two reduction steps, which provide the basis for electrochemical response on glyphosate and HP(O)(OEt)2 with the LOD = 0.1 μM and the linearity within 0.1–80 μM. The Stöber CoII@SiO2 are able to discriminate glyphosate from HP(O)(OEt)2, while the w/o nanoparticles are more efficient but nonselective sensors on the toxicants

Conductive Mediators in Oxidation Based on Ferrocene Functionalized Phosphonium Ionic Liquids

Herein, the synthesis of ferrocene-containing salts is presented. Acylation of ferrocene (Fc) according to the Friedel–Crafts method led to ω-bromoacyl ferrocenes. The ω-bromoacyl ferrocenes were subsequently introduced to quaternization reaction with tri-tert-butyl phosphine, which resulted in phosphonium salts. Obtained phosphonium salts were characterized by physical methods. The electrochemical properties of phosphonium salts were studied by cyclic voltammetry (CV). It was found that the replacement of n-butyl fragments at the phosphorus atom by tert-butyl leads to a more anodic potential shift. In contrast to isolobal structures Fc-C(O)(CH2)nP+(n-Bu)3X− and Fc-(CH2)n+1P+(n-Bu)3X−, the CV curves of Fc-C(O)(CH2)nP+(t-Bu)3X− and Fc-(CH2)n+1P+(t-Bu)3X− did not show a large discrepancy between forward and reverse currents. The transformation of the C=O groups to CH2 fragments had a significant effect on the electrochemical properties of ferrocene salts, the oxidation potential of which is close to that of pure ferrocene

Ferrocene-Containing Sterically Hindered Phosphonium Salts

The synthesis and physical properties of the series of the ferrocenyl-containing sterically hindered phosphonium salts based on di(tert-butyl)ferrocenylphosphine is reported. Analysis of voltamogramms of the obtained compounds revealed some correlations between their structures and electrochemical properties. The elongation of the alkyl chain at the P atom as well as replacement of the Br− anion by [BF4]− shifts the ferrocene/ferrocenium transition of the resulting salts into the positive region. DFT results shows that in the former case, the Br− anion destabilizes the corresponding ion pair, making its oxidation easier due to increased highest occupied molecular orbital (HOMO) energy. Increased HOMO energy for ion pairs with the Br− ion compared to BF4− are caused by contribution of bromide atomic orbitals to the HOMO. The observed correlations can be used for fine-tuning the properties of the salts making them attractive for applications in multicomponent batteries and capacitors

Electrochemical Properties and Structure of Multi-Ferrocenyl Phosphorus Thioesters

The reaction of triferrocenylthiophosphite with elemental sulfur leads to triferrocenyltetrathiophosphate. The molecule of tetrathiophosphate adopts propeller-like all synclinal-conformation of the ferrocenyl fragments respective to the P=S bond. All ferrocenyl groups have nearly ideal eclipsed conformation of the cyclopentadienyl fragments. The Fc3S3P (1), Fc3S3P=O, (2) and Fc3S3P=S (3) demonstrate three reversible and well-separated ferrocenyl-based redox events. The electronic structures of 1–3 have been studied quantum-chemically; the energies and composition of frontier orbitals have been calculated

Influence of the Substituent’s Size in the Phosphinate Group on the Conformational Possibilities of Ferrocenylbisphosphinic Acids in the Design of Coordination Polymers and Metal–Organic Frameworks

This paper illustrates how the size and type of substituent R in the phosphinate group of ferrocenyl bisphosphinic acids can affect conformational possibilities and coordination packing. It also demonstrates that H-phosphinate plays a key role in variational mobility, while Me- or Ph- substituents of the phosphinate group can only lead to 0D complexes or 1D coordination polymer. Overall, this paper provides valuable insights into the design and construction of coordination polymers based on ferrocene-contained linkers. It sheds light on how different reaction conditions and substituents can affect conformational possibilities and coordination packing, which could have significant implications for developing new polymers with unique properties