ABSTRACTPillar-layered metal-organic frameworks (PL-MOFs) are advanced crystalline porous substances built using metal ions, oxygen- and nitrogen-donor linkers. The pillar-layered strategy emerged as a very effective way to incorporate the Schiff base functionalities into pore cages of MOFs by using N-donor Schiff base pillar ligands. The Schiff base functionalities provide active sites for enhanced performance in sensing, catalysis, adsorption, extraction, and gas separation areas. Although the PL-MOFs have gained remarkable advances in the last few decades, Schiff base PL-MOFs have been reviewed to a lesser extent up to this point. In this way, a review summing up their performance is profoundly expected. This review covered the recent developments connected with Schiff base PL-MOFs, including synthesis and applicability in various potential fields. It also included the challenges and forthcoming pathways for fulfilling the research and development needs of Schiff base PL-MOFs.

ABSTRACTIn this paper, the biological applications of synthetic dysprosium(III) complex, with 4,5-diazafluoren-9-one (dafone) ligand, including DNA/BSA interaction, antibacterial and anticancer activity were studied in vitro. The bovine serum albumin (BSA) and fish DNA (FS-DNA) binding of the dysprosium complex were studied by multi-spectrophotometric as well as computational calculation. Its DNA and BSA binding ability were estimated by fluorescence, absorption, circular dichroism spectroscopy, and viscosity measurements (only for DNA). The Dy-complex binds to DNA and BSA presenting high binding constants. For both DNA/BSA binding, the negative signs of thermodynamic parameter confirmed that hydrogen bonds and van der Waals forces play a main role in the interaction process. The competitive experiments with ethidium bromide (EtBr) and rhodamine B exhibited that the Dy-complex interacts with DNA via groove binding. The BSA competitive experiments showed that Dy-complex interacts with site 3 of BSA, which was completely arranged by docking studies. This complex showed high antimicrobial and cytotoxicity. Besides, nanocarriers of Dy-complex were produced, and the anticancer activities of these compounds were measured. (This paper provides a manifestation of a new tradition by which Comments on Inorganic Chemistry starts publishing original research content that, nonetheless, preserves the Journal’s identity as a niche for a critical discussion of contemporary literature in inorganic chemistry) (For previous manifestations, see Comments Inorg. Chem. 2018, 38, 1–35; 2019, 39, 1–26; 2019, 39, 188–215; 2020, 40, 1–24; 2020, 40, 277–303; 2021, 1–46, doi: 10.1080/02603594.2021.1962310.)

(2022). Richard Hadley Holm: A Remembrance and A Tribute. Comments on Inorganic Chemistry: Vol. 42, No. 2, pp. 61-108.

Published in Comments on Inorganic Chemistry: A Journal of Critical Discussion of the Current Literature (Vol. 42, No. 4, 2022)

ABSTRACTThere is an increasing demand for simple, greener, and cost-effective synthesis of nanomaterials and nanostructures with well-defined and uniform architectures. Recently, various studies are focused on the application of plant viruses and bacteriophages to construct innovative nano-based systems and nanoformulations; these viruses can be employed as suitable scaffolds or biotemplates for nanoparticle synthesis in view of their structural symmetry, simplicity in functionalization/surface modification, small sizes, various distinct shapes, simple genetic manipulation, monodispersity, and capability of self-assembling. Additionally, plant viruses and bacteriophages with their unique structures and relative simplicity have shown attractive advantages such as ease of isolation or purification processes and nonpathogenicity to humans and animals. However, there is still a lack of knowledge regarding the mechanisms and relative processes of nanoparticle formation using these viruses. Notably, host organisms are required for protein expression, and there are limited studies on optimization of nanoparticle synthesis and up-scalable and commercial production; therefore, more elaborative studies and comprehensive evaluations should be conducted to find and solve these challenging issues. In this review, important matters pertaining to viral fabrication of nanoparticles using plant viruses and bacteriophages are covered, with a focus on possible mechanisms and related important challenges.

ABSTRACTThe complexation of gadolinium(III) with citric acid in aqueous solutions was studied by pH-metric titration, proton magnetic relaxation, and mathematic simulation in the pH range 2.0–10 at [Gd3+]: [H4Cit] = 1:1, 1:2, 1:3 ([Gd3+] = 1.3, 2.6, 5.0, 10.0, and 20.0 mmol L−1). In the process of simulation, the equilibrium composition, a model obtained from previously known works and including mono- and bis-citrate complexes of gadolinium(III) was taken as a basis. In this work, it is shown that a satisfactory description of the experimental data set of two independent physico-chemical methods is achieved only with the additional inclusion of citrate complexes of gadolinium(III) with higher degree of protonation and some new polynuclear complexes. The complex [GdH4Cit]3+ with the molecular form of the citrate ligand, and the polynuclear complexes [Gd2(HCit)2]°, [Gd2Cit2]2-, [Gd6(OH)2Cit6]8-, [Gd6(OH)3Cit6]9- were first detected at the molar ratio of 1:1. At two- and three-fold excess of citric acid, mononuclear bis- and tris-citrate complexes with different degrees of protonation were found, and binuclear tetrakis- and hexakis-citrate complexes [Gd2(HCit)Cit3]9-and [Gd2(HCit)4Cit2]14- at the pH > 7.5. On the example of this manuscript, the importance of applying the NMR relaxation method for identifying polynuclear complexation in systems containing paramagnetic ions is shown.

ABSTRACTXPS analyses of open shell ionic compounds, especially oxides of the first row transition metals, for information such as oxidation state tend to focus on characteristics of the metal 2p XPS features alone. These analyses could be made considerably more robust with simultaneous characterization of the XPS of the metal 3p features as well as the 2p features. In these comments, we provide a perspective on the conceptual and theoretical framework needed to extract chemical information from the complex multiplet structure of the 3p XPS of Fe oxides as representative of 3d transition metal oxides. We also present information about a novel kind of many-body effects that may contribute to a further redistribution of the Fe 3p XPS intensity. The concern here is not to develop a complicated mathematical formalism but to explain the complexity in terms of fundamental quantum mechanical concepts. This is done on the basis of ab initio Dirac Hartree–Fock wavefunctions where we examine the physical nature of the 3p XPS features of the representative ferrous and ferric oxides of FeO and Fe2O3, respectively. The key objectives of this paper are as follows: (1) to demonstrate the importance of the angular momentum coupling of open shell electrons, which is done more easily with RS multiplets; (2) to show that a single configuration description of the final state multiplets is woefully inadequate; (3) to identify a novel atomic many-body effect that can lead to a rich satellite structure. The considerations discussed here should have implications for making useful interpretations of the XPS of lower BE levels of other ionic, high spin materials. This paper provides a manifestation of a new tradition by which Comments on Inorganic Chemistry starts publishing original research content that, nonetheless, preserves the Journal’s identity as a niche for critical discussion of contemporary literature in inorganic chemistry; for previous manifestations, see Comments Inorg. Chem. 2020, 40, 277–303 and references cited in the abstract thereof.

ABSTRACT In oxidations by nitric acid (HNO3), such as the dissolution of gold (Au) in aqua regia, mixtures of nitrogen monoxide (NO) and nitrogen dioxide (NO2) are produced. In this article, the exact processes through which these two nitrogen oxides are produced were discussed. It was shown that in the processes of dissolution in HNO3 or aqua regia, NO2 is never a direct product of oxidations by HNO3. It was also explained that in such processes, NO2 is always produced from HNO3 and NO reacting. Further, the effect of the concentration of HNO3 was discussed in light of thermodynamic calculations.

ABSTRACTSilica and silicon nanomaterials have diverse applications in the field of drug/gene delivery, lightweight aggregates, regenerative medicine, tissue engineering, cancer diagnosis/therapy, catalytic applications, and energy storage. There is an increasing demand for eco-friendly synthesis of silica and silicon nanomaterials with enough cost-effectiveness, safety, reliability, simplicity, scalability, and controllable particle size distribution features. These materials can be effectively obtained from various agrarian sustainable bio-resources, including rice husk ash, sugar-cane, coffee husk, wheat husk and corn cob ash. Using green and sustainable techniques can cause to eliminate or reduce laborious/complicated procedures and reduce the environmental contaminants to obtain advanced materials for high-tech applications. In this review, recent advancements pertaining to the catalytic and biomedical applications of silica and silicon nanoparticles are highlighted, as well as their greener synthetic methods.

ABSTRACTThe development of appropriate luminophores for detecting nitroaromatic explosives is a crucial issue for our safety and security. In the past decade, astounding efforts have been made towards the development of phosphorescent iridium probes based on diverse sensing mechanisms for explosive detection. Phosphorescent iridium materials possess unique properties such as long-lived phosphorescence, high quantum efficiency, and modular syntheses that render them as suitable alternatives to organic dyes. According to the literature, many of the iridium molecular probes used to detect nitroaromatics are ”turn-off” luminescence sensors. Thus, the review describes the current state-of-the-art, its accomplishments, unique challenges, and future directions.

ABSTRACTHydrogen (H2) is examined as a fuel and as one of the most extensively studied substitute energy resources for available sources that are being consumed rapidly. Thus, the growing interest in the development of competitive, low-cost hydrogen production leads us to devote particular efforts to establish efficient processes in an economical and environmentally benign way. In this view, both photochemical and electrochemical processes have been exclusively investigated as greener paths for hydrogen production. The present review article highlights the process established for hydrogen generation over the last few years. The overall thrust of the present theme is a discussion of the efforts that have been made so far for finding hydrogen as an alternative fuel from different feedstock through photochemical and electrochemical processes.

ABSTRACTThis paper provides a manifestation of a new tradition by which Comments on Inorganic Chemistry starts publishing original research content that, nonetheless, preserves the Journal’s identity as a niche for a critical discussion of contemporary literature in inorganic chemistry; for previous manifestations, see Comments Inorg. Chem. 2020, 40, 277-303 and references cited in the abstract thereof as Yaseen W. K.; Sanders S. F.; Almotawa R. M.; Otten B. M.; Bhat S.; Alamo D. C.; Marpu S. B.; Golden T. D.; Omary M. A. “Are Metal Complexes” Organic, Inorganic, Organometallic, or Metal-Organic Materials? A case Study for the Use of Trinuclear Coinage Metal Complexes as “Metal-Organic Coatings” for Corrosion Suppression on Aluminum Substrates Comments Inorg. Chem. 2019, 39, 1-26 and also, Mohapatra R. K.; Das P. K.; Pradhan M. K.; El-Ajaily M. M.; Das D.; Salem H. F.; Mahanta U.; Badhei G.; Parhi P. K.; Maihub A. A.; Kudrat -E-Zahan Md. “Recent Advances in Urea- and Thiourea-Based Metal Complexes: Biological, Sensor, Optical, and Corrosion Inhibition Studies” Comments Inorg. Chem. 2019, 39, 127-147).In this work, the Schiff base 1-(6-(1-((4-(4-aminophenoxy)phenyl)imino)ethyl)-pyridin-2-yl)ethan-1-one (L) and eight transition metal complexes were synthesized. The reaction of 4,4-oxy-dianiline with 2,6-diacetylpyridine in 1:1 molar ratio affords to the ligand which was employed in the synthesis of the corresponding metal complexes by reacting with the Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) chlorides in 1:1 molar ratio. All the compounds were characterized by using different analytical methods. Structures of complexes were found to be octahedral as deduced from the spectroscopic and magnetic moment measurements. The ligand behaves as a neutral tridentate ligand where it coordinated to metal ions through N-azomethine, N-pyridine, and O-carbonyl group. Besides, experimental investigations for their antibacterial activity against different bacteria species were studied, molecular docking studies were reported with receptors 4ME7, 4K3V, 3T88 and 4WJ3. Density functional theory (DFT) calculations for ligand were reported. Finally, the evaluation of corrosion inhibition efficiency was measured by using different techniques such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and electrochemical frequency modulation (EFM). Scanning electron microscope (SEM) and energy dispersive X-Ray analysis (EDX) were measured to affirm the presence of barrier film on the carbon steel surface by inspecting the surface morphologies and elemental composition of corrosion products.

ABSTRACTThe interactions between transition metals and sulfur have long been studied for potential applications in catalysis and energy storage and due to the relevance of these motifs in biological and geological systems. Complexes with sulfur-containing ligands can undergo redox transformations centered on sulfur as well as at the metal. Sulfur also readily catenates with other sulfur centers to form polysulfur motifs. Here, the synthesis and structures of notable examples of metal complexes with sulfur-containing ligands (sulfido, polysulfido, and polysulfanido) are described. Aspects of sulfur-centered redox, including spectroscopic and structural considerations, and future research opportunities are highlighted.

ABSTRACTQuantum objects, such as atoms, spins, and subatomic particles, haveunique physical properties that could be useful for many different applications, ranging from quantum information processing to magnetic resonance imaging. Molecular species also exhibit these quantum properties, and, importantly, these properties are fundamentally tunable by synthetic design, unlike ions isolated in a quadrupolar trap, for example. In this comment, we distill multiple, distinct, scientific efforts into an emergent field that is devoted to designing molecules that mimic the quantum properties of objects like trapped atoms or defects in solids. Mimicry is endemic in inorganic chemistry and featured heavily in the research interests of groups across the world. We describe this new field of using molecular inorganic chemistry to mimic the quantum properties (e.g. the lifetime of spin superpositions, or the resonant frequencies thereof) of other quantum objects as “quantum mimicry.” In this comment, we describe the philosophical design strategies and recent exciting results from the application of these strategies.

ABSTRACT This paper provides a 4th manifestation of a new tradition by which the editors of Comments on Inorganic Chemistry wish to lead by example, whereby we start publishing original research content that, nonetheless, preserves the Journal’s identity as a niche for critical discussion of contemporary literature in inorganic chemistry. (For the 1st, 2nd and 3rd manifestations, see: a) Otten, B. M.; Melancon, K. M.; Omary, M. A. “All That Glitters is Not Gold: A Computational Study of Covalent vs Metallophilic Bonding in Bimetallic Complexes of d10 Metal Centers – A Tribute to Al Cotton on the 10th Anniversary of His Passing,” Comments Inorg. Chem. 2018, 38, 1–35; b) Yaseen, W. K.; Sanders, S. F.; Almotawa, R. M.; Otten, B. M.; Bhat, S.; Alamo, D. C.; Marpu, S. B.; Golden, T. D.; Omary, M. A. “Are Metal Complexes “Organic”, “Inorganic”, “Organometallic”, or “Metal-Organic” Materials? A Case Study for the Use of Trinuclear Coinage Metal Complexes as “Metal-Organic Coatings” for Corrosion Suppression on Aluminum Substrates”, Comments Inorg. Chem. 2019, 39, 1–26; and c) Smith, J. B.; Otten, B. M.; Derry, P. J.; Browning, C.; Bodenstedt, K. W.; Sandridge, J. H.; Satumtira, N. T.; Zilaie, M.; Payne, J.; Nuti, R.; Omary, M. A.; Smucker, B. W. “Luminescent, Redox-Active (Dithiolato)Bis(Imine)Platinum(II) Divergent Complexes with Exchangeable Imine Ligands: An Experimental/Computational Study versus Their (Diimine)(Dithiolato)Platinum(II) Convergent Congeners”, Comments Inorg. Chem. 2019, 39, 188–215.) Herein, the dinuclear complexes {Cu[3,5-(CF3)2Pz](µ-dppm)}2 and {Cu[3,5-(CF3)2Pz](µ-dppm)}2•3THF were studied structurally, spectroscopically and via density functional theory (DFT). They were synthesized by reacting bis(diphenylphosphino)methane (dppm) with the cyclic trinuclear complex {μ-[3,5-(CF3)2Pz]Cu}3 to effect nuclearity reduction. Two forms of crystalline solids, {Cu[3,5-(CF3)2Pz](µ-dppm)}2 and {Cu[3,5-(CF3)2Pz](µ-dppm)}2•3THF have been obtained using different recrystallization conditions. The {Cu[3,5-(CF3)2Pz](µ-dppm)}2 complex was found through DFT computations to undergo a distortion from a Y-shaped coordination sphere in the S0 ground state toward a T-shape in the T1 photoexcited, lowest-lying, phosphorescent state. The distortion also causes the copper-copper bond length to contract and form an excimer bond (dCu-Cu = 2.577 Å). Experimentally, the presence of THF in the crystal was found to cause a blue shift, effecting a change in emission color from teal to blue to the naked eye, with a near-unity quantum yields (93%), rendering the latter solid suitable for inorganic LED applications but not OLEDs, as thin films exhibit a reduced quantum yield. Crystallographic evidence suggests that THF leads to a more compact lattice that makes the complexes more rigid and thus hinder the excited state distortions vs unsolvated crystals. Greater distortion leads to a lower energy radiative emission and thus a red shift in the emission color. Films were also studied and found to undergo further red shifting as a result of less rigidity in the media and more surface molecules susceptible to distortion, hence manifesting the luminescence rigidochromism optical phenomenon in the solid state as opposed to the traditional manifestation in frozen vs fluid solution. Photobleaching was studied in both the film and powder to assess photostability, which was superior in neat vs doped solids, which is also favorable for LED applications. Graphical Abstract

ABSTRACTElectrocatalytic hydrogen evolution reactions (HER) offer an enduring strategy for hydrogen fuel production and are vital for sustainable energy conversion and storage. To explore efficient and durable HER electrocatalysts, we fabricated gold-aryl nanoparticles (AuNPs-COOH) anchored on graphitic carbon nitride (g-C3N4) sheets by reducing aryldiazonium tetrachloroaurate(III) salt with sodium borohydride at room temperature in water. Two different nanocomposites, AuNPs-COOH-g-C3N4 (H) (higher amount of g-C3N4) and AuNPs-COOH-g-C3N4 (L) (lower amount of g-C3N4) were prepared. Contact angle measurements revealed that the increased surface wettability of the nanocomposites on glass and silicon wafer surfaces compared to pristine g-C3N4. Cyclic voltammetry, electrochemical impedance spectroscopy, double-layer capacitance, linear sweep voltammetry, and chronoamperometry measurements revealed that AuNPs-COOH-g-C3N4 (L) displayed the best HER performance in 0.1 M H2SO4 electrolyte. Overall, nanocomposites exhibited higher electrocatalytic activity compared to bare AuNPs-COOH and pristine g-C3N4 in current density and onset potential values. The AuNPs-COOH-g-C3N4 (L) nanocomposite offered an excellent electrocatalytic activity and displayed a current density of 53.4 mA/cm2 at 0.72 V vs RHE, which is nearly twice compared to bare AuNPs-COOH of 33.1 mA/cm2. In addition, the nanocomposite showed the lowest onset potential of 0.14 V vs RHE compared to 0.26 V and 0.31 V for AuNPs-COOH-g-C3N4 (H) and AuNPs-COOH, respectively.

ABSTRACTThis review article focuses on 1λ3-phosphaalkene compounds derived from phosphines containing at least one silicon-phosphorous bond. 1λ3-Phosphaalkene compounds are of high value as they are used to form several phosphorous compounds containing a transition metal and main group elements. In addition to the fact that different kinds of 1λ3-phosphaalkynes are prepared from 1λ3-phosphaalkenes. Both families of phosphorous compounds; 1λ3-phosphaalkenes and 1λ3-phosphaalkynes have become important to chemists, as they are used in preparing several phosphorous compounds to be used as homogeneous catalysts in chemical reactions.

ABSTRACTZeolite membranes are widely used in separation, catalysis, sensors and other fields because of their good diffusion performance, shape selection and catalysis capabilities. However, the slow synthesis rate of zeolite membranes restricts their industrialization process, and the random orientation seriously affects their performance. Therefore, this paper investigates the methods for accelerating the synthesis rate of zeolites and the roles of different methods was explored. The synthesis conditions of oriented zeolite membranes are also summarized. Microwave method can efficiently synthesize oriented zeolite membranes, but it has the defects of harsh synthesis conditions and high equipment requirements. Using physical methods and chemical methods to introduce hydroxyl radicals, which is also an effective method to improve the synthesis rate of zeolites. However, there is a lack of research on how to realize the directional synthesis of zeolite membranes during this process. Synthesis conditions, template and support properties affect the directional synthesis of zeolite membranes. Therefore, while introducing free radicals, adjusting the composition of the synthetic solution or introducing inhibitors that affect the growth direction of zeolite in the synthetic system can realize the efficient directional synthesis of zeolite membrane, which is another potential method to promote the industrialization of directional zeolite membrane besides microwave method.

ABSTRACTTitanium dioxide was prepared using titanium-based metal–organic framework (MOF) i.e., NH2-MIL-125(Ti) as a metal precursor. NH2-MIL-125(Ti) was synthesized then calcined at 400 °C, 500 °C, 550 °C, and 600 °C. The properties of NH2-MIL-125(Ti) and produced TiO2 were investigated using various techniques, including powder X-ray diffraction (PXRD), Brunauer–Emmett–Teller (BET), and UV–visible diffuse reflectance spectroscopy (UV–Vis DRS). A scanning electron microscopy (SEM) was used to observe surface morphology and energy-dispersive X-ray spectroscopy (EDX) to analyze elemental composition of prepared samples. PXRD pattern confirms TiO2 anatase phase formation when Ti-MOF was calcined up to 500 °C, whereas the formation of TiO2 rutile phase at calcination temperature of 600 °C. The photocatalytic activities of produced TiO2 photocatalysts were investigated for the cycloaddition reaction of CO2 to propylene oxide.

ABSTRACTSymmetric and asymmetric dihydroxylation reactions catalyzed by osmium have emerged as the most efficient route in the one-step synthesis of diols. This is because on an industrial scale 1,2-diols are prepared via a two-step procedure. Still, it is a challenge to prepare and apply osmium catalysts in dihydroxylation catalysis because of their safety and environmental implications; e.g., volatile, highly toxic, product contamination, etc. To date, few efforts were reported to comprehensively overcome these drawbacks with great success by heterogenizing to an insoluble matrix, including diminishment in catalytic performance. Hence, the need for efficacious solid-supported osmium catalysts to subdue these difficulties is a topic of great importance. This mini review provides a concise overview of some of the most encouraging solid-supported osmium catalysts reported over the last few years, which proved to be more efficient under mild conditions as opposed to other immobilized osmium catalytic systems. The summary discusses the latest developments in the synthetic heterogenizing and homogenization strategies, structure analysis and investigation toward symmetric and asymmetric dihydroxylation for diol production. Specific emphasis is focused on their mechanistic considerations, their reusability and improvement in their safety, and environmental implications.