Kinetic Control Research Articles

Evaluation of structurally related acyclic ligands OBETA, EHDTA, and EGTA for stable Mn2+ complex formation.

In recent years, significant research efforts have been dedicated to finding efficient and safe alternatives to the currently used gadolinium (Gd)-based MRI contrast agents. Among the most explored alternatives are paramagnetic chelates of the Earth-abundant Mn2+, which form a prominent class of metal complexes. The design of Mn2+ complexes with enhanced relaxation properties and improved safety profiles hinges on a delicate balance between thermodynamic and kinetic stability, as well as the presence of coordinated water molecules. In this study, we present a comprehensive investigation into the coordination chemistry of three structurally related polyetheraminocarboxylic chelating agents. Our aim is to elucidate the structural features, paramagnetic properties, and thermodynamic and kinetic inertness of the corresponding Mn2+ complexes. The most significant finding is the considerable difference in the dissociation rates of the complexes, with the octadentate EGTA complex being the most labile. The observed dissociation rates correlate well with the nitrogen inversion dynamics, as assessed through NMR spectral analysis of the analogous Zn2+ complexes.

Rapid, Controlled Branching Polymerization of Cyanoacrylate via Pathway-Enabled, Site-Specific Branching Initiation.

Controlled branched structures remain a key synthetic limitation for monomeric tissue adhesives because their on-site polymerization that enables adhesion formation requires rapid kinetics, high conversion, and straightforward setup. In this context, site-specific branching initiation by using evolmers is potentially effective for structural control; however, the efficiency and kinetics in current reaction setups persists to be a major challenge. In this paper, an evolmer induces a controlled branching polymerization of cyanoacrylate amid the high monomer reactivity useful in rapid adhesion. The contrasting reactivities between the vinyl and the initiating groups in the evolmer molecule generate a kinetic pathway that favors a control-enabling branching mechanism. Through density functional theory calculations, the reaction pathway toward branching is shown to kinetically favor site-specific initiation by six orders of magnitude than the route toward non-specificity. Reaction monitoring confirms the branching polymerization after the polymerization with the evolmer forms a more compact structure than the linear counterpart. Control of branching density is demonstrated in rapid polymerizations within minutes and in polymerizations completed in an instant. These results provide a template for achieving site-specific branching initiation during adhesion formation and, broadly, where conditions for kinetic control are necessary.

Misfit Layered Compounds: Insights into Chemical, Kinetic, and Thermodynamic Stability of Nanophases.

ConspectusCompounds with layered structures (2D-materials), like transition metal-dichalcogenides (e.g., MoS2), attracted a great deal of interest in the scientific community in recent years. This interest can be attributed to their unique lamellar structure, which induces large anisotropy in their physicochemical properties. Furthermore, owing to the weak van der Waals interaction between the layers, they can be cleaved along the a-b plane, which allows fabricating single layers with physical properties entirely different from the bulk material. Moreover, stacking layers of different 2D-materials on top of each other has led to a wealth of new observations, for instance, by twisting two layers with respect to each other and producing Moiré lattice. Another outstanding property of inorganic layer compounds is their tendency to form nanotubes, reported first (for WS2) many years ago and subsequently from many other layered compounds.Among the 2D-materials, misfit layer compounds make a special class with an incommensurate and nonstoichiometric lattice made of an alternating layer with rocksalt structure, like LaS (O) and a layer with hexagonal structure, like TaS2 (T). The lack of lattice commensuration between the two slabs leads to a built-in strain, which can be relaxed via bending. Consequently, nanotubes have been produced from numerous MLC compounds over the past decade and their structure was elucidated.Owing to their large surface area, nanostructures are generally metastable and tend to recrystallize into microscopic crystallites via different mechanisms, like Ostwald ripening, or chemically decompose and then recrystallize. The stability of nanostructures at elevated temperatures has been investigated quite scarcely so far. In this perspective, electron microscopy as well as synchrotron-based X-ray absorption and reflection techniques were used to elucidate the chemical selectivity and decomposition routes of rare-earth based MLC nanotubes prepared at elevated temperatures (800-1200 °C).As for the chemical selectivity, entropic effects are expected to dictate the random distribution of the chalcogen atoms on the anion sites of the MLC nanotubes at elevated temperatures. Nonetheless, the sulfur atoms were found to bind exclusively to the rare-earth atom (Ln = La, Sm) of the rocksalt slab and the selenium to the tantalum of the hexagonal TX2 slab. This uncommon selectivity was not found in other kinds of nanotubes like WSe2xS2(1-x). In other series of experiments, the lack of utter symmetry in the multiwall nanotubes leads to exclusions of certain X-ray (0kl) reflections, which was used to distinguish them from the bulk crystallites. The transformation of Ln-based MLC nanotubes into microscopic flakes was followed as a function of the synthesis temperature (800-1200 °C) and the synthesis time (1-96 h). Furthermore, sequential high-temperature transformations of the (O-T) lattice into (O-T-T) and finally (O-T-T-T) phases via deintercalation of the LnS slab was observed. This autocatalytic process is reminiscent of the deintercalation of alkali atoms from different layered structure materials. Annealing at higher temperatures and for longer periods of time eventually leads to the decomposition of the ternary MLC into binary metal-sulfide phases, as well as partial oxidation of the product. This study sheds light on the complex mechanism of high-temperature chemical stability of the nanostructures.

Deciphering the mechanism underlying poor aqueous solubility of extracted quinoa proteins

This study aimed to decipher the mechanisms underlying poor solubility of quinoa proteins by investigating the form of quinoa proteins dispersed in water and how protein-protein interactions influenced the kinetic stability of proteins in the dispersions. Specifically, the relative solubility and the forms of quinoa proteins in 1–5 w/w% protein dispersions were determined by separating proteins via centrifugation and/or ultrafiltration. The kinetic stability of quinoa proteins in the supernatants over a 3-week storage period was characterized by determining the changes of concentration, composition and physicochemical properties of quinoa proteins and predicting protein-protein interactions. The results showed that quinoa proteins existed mainly as differently-sized protein aggregates in the dispersions, leading to low relative solubility. The coagulation of protein aggregates in the supernatants caused severe precipitation during the first week of storage whereas they were disassociated simultaneously. With further storage, the remaining proteins in the supernatants reached kinetic stability, which was contributed by stronger electrostatic repulsion and lower surface hydrophobicity. Moreover, 11S globulin and 2S albumin were precipitated and solubilized together during storage, which was ascribed to intermolecular interactions driven by multiple sites between 11S globulin and/or 2S albumin. This study lays a foundation for extensive utilization of quinoa proteins.

Discretely Nonlinearly Stable Weight-Adjusted Flux Reconstruction High-Order Method for Compressible Flows on Curvilinear Grids

To achieve genuine predictive capability, an algorithm must consistently deliver accurate results over prolonged temporal integration periods, avoiding the unwarranted growth of aliasing errors that compromise the discrete solution. Provable nonlinear stability bounds the discrete approximation and ensures that the discretization does not diverge. Nonlinear stability is accomplished by satisfying a secondary conservation law, namely for compressible flows; the second law of thermodynamics. For high-order methods, discrete nonlinear stability and entropy stability, have been successfully implemented for discontinuous Galerkin (DG) and residual distribution schemes, where the stability proofs depend on properties of L2-norms. In this paper, nonlinearly stable flux reconstruction (NSFR) schemes are developed for three-dimensional compressible flow in curvilinear coordinates. NSFR is derived by merging the energy stable flux reconstruction (ESFR) framework with entropy stable DG schemes. NSFR is demonstrated to use larger time-steps than DG due to the ESFR correction functions, at the cost of larger error levels at design order convergence for equivalent degrees of freedom, while preserving discrete nonlinear stability. NSFR differs from ESFR schemes in the literature since it incorporates the FR correction functions on the volume terms through the use of a modified mass matrix. We also prove that discrete kinetic energy stability cannot be preserved to machine precision for quadrature rules where the surface quadrature is not a subset of the volume quadrature. This result stems from the inverse mapping from the kinetic energy variables to the conservative variables not existing for the kinetic energy projected variables. This paper also presents the NSFR modified mass matrix in a weight-adjusted form. This form reduces the computational cost in curvilinear coordinates because the dense matrix inversion is approximated by a pre-computed projection operator and the inverse of a diagonal matrix on-the-fly and exploits the tensor product basis functions to utilize sum-factorization. The nonlinear stability properties of the scheme are verified on a nonsymmetric curvilinear grid for the inviscid Taylor-Green vortex problem and the correct orders of convergence were obtained on a curvilinear mesh for a manufactured solution. Lastly, we perform a computational cost comparison between conservative DG, overintegrated DG, and our proposed entropy conserving NSFR scheme, and find that our proposed entropy conserving NSFR scheme is computationally competitive with the conservative DG scheme.

Robust interface for O3-type layered cathode towards stable ether-based sodium-ion full batteries

Developing a robust cathode-electrolyte interface (CEI) is crucial for stable layered cathode in sodium-ion batteries (SIBs). A CEI based on ester electrolytes often exhibit poor stability and robustness, which cannot address the issues of structural collapse and material dissolution in layered cathodes. However, there are few reports on constructing a stable CEI for layered cathode based on ether electrolytes. Here we develop a robust CEI for O3-type cathode via DME solvent, which enables a long-term stability of full SIBs. The results indicate that unique decomposition process of DME yields favorable organic component (e.g. RCH2ONa) and high content of inorganic components (e.g. NaF and Na2CO3) in the CEI, which is quite different from ester electrolyte, improving Na+ diffusion kinetic and interfacial stability. Notably, the O3-NaNi0.5Mn0.5O2||Na cell with the designed electrolyte demonstrates outstanding stability up to 500 cycles. Furthermore, the full cell exhibits remarkable cycling performance with a capacity retention of 85% over 200 cycles. This work provides an opportunity for stable operation of layered cathode materials via inexpensive ether electrolytes.

A new improvement to the characteristic equation method applied to different single-effect LiBr-H2O absorption chillers

The characteristic equation method was developed to be applied to absorption machines using characteristic equations to control and predict the thermodynamic performance of these machines. Since the conventional characteristic equation method was established, different approaches have been taken to improve the accuracy of the results of the characteristic equations. The Dühring parameter (B) represents a linear relationship between the internal boiling temperatures at a given concentration of solution and has usually been adopted as a constant fixed value in the characteristic equation method. The influence of the Dühring parameter (B) on the accuracy of the main results is important to the characteristic equation method and has not been analyzed further. This study analyzed this parameter in the characteristic equation method and a new approach to this method was proposed. This analysis gives a better insight into the influence of this parameter on the characteristic equation method and this approach provides a new use of this method to achieve better thermodynamic prediction and control of absorption chillers of different capacities under different operating conditions. The deviations between the fixed B value usually adopted for the LiBr/H2O solution and each value of the B obtained by the model at different concentrations of solution and internal temperatures affected the accuracy of the main results of the characteristic equations. An approach using a linear adjustment between B and the thrust temperature (Δtthrust) was put forward to reduce these deviations. The results of the characteristic equations were more accurate using this adjustment than using the fixed B value. Then, the characteristic equation method was applied to six LiBr/H2O single-effect absorption chillers using the proposed new approach. This approach was compared with the conventional method and with other main approaches. The heat removed (Q̇E) and COP results from the characteristic equations and the thermodynamic modelling were compared. All the average deviations using the proposed approach were less than 2 %, which represents an improvement in the accuracy of the results of the characteristic equations and gives a better prediction and control of absorption chiller performance. Therefore, the proposed approach contributed to improve the accuracy of the characteristic equation method in order to refine its application to absorption chillers.

Synthesis, spectroscopic characterization, crystallographic studies, Hirshfeld surface analysis, DFT, and molecular docking studies of (4-phenylthiazol-2-yl)(thiophen-2-yl)methanone

In the present research article, we have synthesized a novel (4-phenylthiazol-2-yl)(thiophen-2-yl)methanone molecule. The structure of this compound was confirmed using 1H and 13C NMR spectroscopic techniques. Additionally, the crystal structure was determined through single crystal X-ray diffraction, revealing stabilization by various intra and intermolecular interactions, along with π⋅⋅⋅π interaction. These interactions lead to the formation of R_2^2(4) S(6) and S(5) synthons, which play a crucial role in enhancing the stability of the crystal structure. Moreover, the interactions were verified using Hershfield surface analysis and 2D fingerprint plot evaluations. Energy framework analysis was employed to determine the extent to which the interactions existed and the 3D arrangement of the packing economy within the crystal. The outcomes showed that dispersion energy is higher than repulsion and coulomb energies in the crystal structures' interaction energies and chemical pairs. The electronic properties, such as MEP and HOMO-LUMO energy levels have been investigated using DFT. A substantial HOMO-LUMO energy gap of 3.760 eV suggests that the synthesized molecule exhibits high kinetic stability. Also, molecular docking studies were conducted on the target protein (PDB ID: 3S7S) to explore the binding modes and interactions between the proteins and the ligand.

Fabrication of stable oleogel-in-water nanoemulsions with ethyl cellulose nanoparticles

Nanoemulsions (NEs) are liquid-based nanosized colloidal systems offering advantages (superior kinetic stability and rheology) compared to macro- and microemulsions. However, stabilization of these emulsions is difficult, since the small droplet sizes in NEs present large surface area-to-volume ratios. Thus, they need to be stabilized by superb emulsifiers to maintain stability. Herein, we report the construction of novel oleogel-in-water NEs with excellent stability against coalescence and phase separation. To do this, nanoparticles (NPs), based on ethylcellulose (EC), were first prepared, and then NEs were made using EC oleogel as the oil phase, ECNPs solution as the water phase, and tween-80 (TW80) as the surfactant. It was observed that NE stabilized by ECNPs, EC oleogel, and TW80 had a significantly lower particle size (201.86±1.57 nm), polydispersity index (0.13±0.06), with no phase separation over 30 days of storage as well as a higher zeta potential (-79.68±1.36 mV), and complex modulus (21441.80±418.21 kPa), as compared to the control NE (stabilized only by TW80). According to the findings, the developed NE has the potential for food and drug delivery applications.

A new strategy toward synthesis of novel bifunctional N- and S-bearing sorbent for platinum(IV) removal from aqueous solutions and acidic leaching residue of Pt/Al2O3 catalyst

Strong incentive politics have been elaborated for promoting the recovery of precious metals from secondary resources. Solid leaching generates acidic effluents that can be pre-treated using precipitation steps for partial separation before applying sorption for metal recovery from mild acidic solutions. For this purpose, a new sorbent was designed bearing numerous N- and S-bearing reactive groups with good affinity for platinum (as chloroanionic species). Thiazole precursors were first reacted before being grafted (by free radical reaction) with triallyl cyanurate (to form CTTR sorbent). The material was characterized by a series of analytical tools (SEM, BET, FTIR, XPS, TGA, elemental analysis, and titration). The effect of pH combined with FTIR and XPS spectroscopy analyses allowed identifying the mechanisms involved in metal binding: (a) electrostatic attraction of chloroplatinate anions with protonated amine groups (especially in acidic conditions), (b) while at moderate acidic pH metal sorption proceeds through ligand exchange and chelation onto N-based and S-based groups. Optimum sorption was found at pH close to 4 (near pHpzc value). Under selected experimental conditions, the equilibrium was reached in 25–35 min. The pseudo-first order rate equation fitted well experimental profile (though the resistance to intraparticle diffusion contributes to the kinetic control). The maximum sorption capacity at room temperature reached up to 1.58 mmol Pt g−1 (at pH 4). The sorption isotherm was successfully fitted by the Temkin equation. The sorption is spontaneous and exothermic (with reduction in maximum sorption capacity reaching up to 25 %, when temperature increases to 50 °C). Optimum platinum desorption was obtained with 0.3 M HCl solution (with solid/liquid ratio 1.67 g L−1) for complete desorption and enrichment factor close to 4.6. Complete desorption was maintained over 5 cycles, while the sorption efficiency decreased by less than 3.5 % at the fifth cycle. The sorbent showed remarkable stability for PGMs (Pd(II) in addition to Pt(IV)) against alkali-earth elements or base metals (from equimolar synthetic solutions); the selectivity is driven by the preference of the reactive groups (soft base and intermediary base) for soft PGM metals against hard and borderline metal ions; this selectivity is also affected by metal speciation (formation of chloro-anionic species). The valorization of platinum from non-compliant Pt/Al2O3 catalyst was investigated after leaching with aqua regia. Platinum was precipitated from the leachate with ammonium chloride. In a second step, aluminum was removed by precipitation at pH 5. The residual solution was then treated by adsorption on CTTR: optimum separation between Pt and Al was achieved at pH ≈ 3.

An MEDT Study of the Reaction Mechanism and Selectivity of the Hetero-Diels-Alder Reaction Between 3-Methylene-2,4-Chromandione and Methyl Vinyl Ether.

The hetero-Diels-Alder (HDA) reaction between the ambident heterodiene 3-methylene-2,4-chromandione (MCDO) and non-symmetric methyl vinyl ether (MVE) is investigated using the molecular electron density theory (MEDT) at the B3LYP/6-311G(d,p) computational level. The aim of this study is to gain insight into its molecular mechanism and to elucidate the factors that control the selectivity found experimentally. DFT-based reactivity indices reveal that MCDO exhibits strong electrophilic characteristics, while MVE displays a strong nucleophilic character. Meanwhile, the Parr function explains the ortho regioselectivity of this HDA reaction. The highly polar nature of this HDA reaction, supported by the high global electron density transfer (GEDT) taking place at the transition state structures (TSs), accounts for the very low activation energy associated with the most favorable TS-4on. The ambident nature of MCDO allows for the formation of two constitutional isomeric cycloadducts. In the case of MVE, pseudocyclic selectivity is attained using a thermodynamic control. This polar HDA reaction displays an endo stereoselectivity and a complete ortho regioselectivity. A comparative relative interacting atomic energy (RIAE) analysis of the two diastereomeric structures TS-4on and TS-6on indicates a high degree of likeness, which explains the low pseudocyclic selectivity under kinetic control.

Kinetic control aspects and mechanisms in oriented membrane processes for extraction and recovery of ascorbic acid compound.

Ascorbic acid comprises four enantiomers, with only one of them, L-ascorbic acid, recognized as vitamin C. The modern industries place significant importance on obtaining this compound in its purest form. The challenge is to recover L-ascorbic acid, which requires specific processes within these industries. To satisfy this condition, purification is needed, a process that requires large quantities of solvents and high energy consumption. To overcome these limitations, we conducted a study on the facilitated extraction of L-ascorbic acid using three affinity polymer membranes, including supported liquid membrane (SLM), polymer inclusion membrane (PIM), and grafted polymer membranes (GPM) with cholic acid as the extractive agent. Following the characterization of the membranes using IR spectroscopy and SEM techniques, we investigated various parameters associated with substrate diffusion through the organic membrane phase. Regarding the biologically active L-ascorbic acid, our research findings indicated that kinetic factors drove the mechanisms of the studied processes.

Design rules for catalysis in single-particle plasmonic nanogap reactors with precisely aligned molecular monolayers

Plasmonic nanostructures can both drive and interrogate light-driven catalytic reactions. Sensitive detection of reaction pathways is achieved by confining optical fields near the active surface. However, effective control of the reaction kinetics remains a challenge to utilize nanostructure constructs as efficient chemical reactors. Here we present a nanoreactor construct exhibiting high catalytic and optical efficiencies, based on a nanoparticle-on-mirror (NPoM) platform. We observe and track pathways of the Pd-catalysed C-C coupling reaction of molecules within a set of nanogaps presenting different chemical surfaces. Atomic monolayer coatings of Pd on the different Au facets enable tuning of the reaction kinetics of surface-bound molecules. Systematic analysis shows the catalytic efficiency of NPoM-based nanoreactors greatly improves on platforms based on aggregated nanoparticles. More importantly, we show Pd monolayers on the nanoparticle or on the mirror play significantly different roles in the surface reaction kinetics. Our data provides clear evidence for catalytic dependencies on molecular configuration in well-defined nanostructures. Such nanoreactor constructs therefore yield clearer design rules for plasmonic catalysis.

DFT analysis of the concerted metalation-deprotonation in earth-abundant 3d-transition-metal mediated C–H activations

Methane activation and functionalization under catalytic conditions remains a challenge that must be addressed to make this abundant alkane, the primary component of natural gas, into a more useful resource. One possible method of methane activation is concerted metalation-deprotonation (CMD), which thus far has been largely limited to precious metals and more reactive substrates. In this DFT study, CMD activation of methane is assessed employing more earth-abundant 3d transition metal complexes to assess the effects of metal, ligands, etc. upon the kinetics and thermodynamics of methane C–H activation via CMD mechanisms. Key findings from this study reveal the strong influence spin states as well as ligand modification have on the activation energy barriers. Moreover, an unexpected observation pertaining to ligand modification was seen where the acetate ligand exhibited higher computed free energy barriers compared to the trifluoroacetate ligand. Although acetate is more basic than trifluoroacetate, the ligand directing effects ultimately had a greater influence on the thermodynamic control of the CMD mechanism being studied here.

Kirkendall Effect-Driven Reversible Chemical Transformation for Reconfigurable Nanocrystals.

The potential universality of chemical transformation principles makes it a powerful tool for nanocrystal (NC) synthesis. An example is the nanoscale Kirkendall effect, which serves as a guideline for the construction of hollow structures with different properties compared to their solid counterparts. However, even this general process is still limited in material scope, structural complexity, and, in particular, transformations beyond the conventional solid-to-hollow process. We demonstrate in this work an extension of the Kirkendall effect that drives reversible structural and phase transformations between metastable metal chalcogenides (MCs) and metal phosphides (MPs). Starting from Ni3S4/Cu1.94S NCs as the initial frameworks, ligand-regulated sequential extractions and diffusion of host/guest (S2-/P3-) anions between Ni3S4/Cu1.94S and Ni2P/Cu3P phases enable solid-to-hollow-to-solid structural motif evolution while retaining the overall morphology of the NC. An in-depth mechanistic study reveals that the transformation between metastable MCs and MPs occurs through a combination of ligand-dependent kinetic control and anion mixing-induced thermodynamic control. This strategy provides a robust platform for creating a library of reconfigurable NCs with tunable compositions, structures, and interfaces.

Efficient CO2 Reduction Reaction on Cu-Decorated Biphenylene.

Developing efficient electrocatalysts for CO2 reduction into value-added products is crucial for a green economy. Inspired by the recent experimental synthesis of biphenylene (BPH) and the excellent catalytic activity of copper dispersed on two-dimensional (2D) materials, we chose to systematically investigate the pristine, defective, and Cu-decorated BPH for the electrocatalytic CO2 reduction to value-added hydrocarbons. It is observed that the CO2 molecules bind weakly to the pristine BPH, indicating their chemical inertness. Carbon single-vacancy defects facilitate CO2 adsorption with a strong binding energy (Eb) of -3.23 eV, detrimental to the CO2 reduction reaction (CRR) mechanism. We have further investigated the binding energy and kinetic stability of Cu-decorated BPH as a single-atom-catalyst (SAC). The molecular dynamics simulations confirm the kinetic stability, revealing that the Cu-atom avoids agglomeration under low metal dispersal conditions. The CO2 molecule gets adsorbed horizontally on the Cu-BPH surface with a ΔEb of -0.52 eV. The CRR mechanism is investigated using two pathways beginning with two different initial states, formate (*OCOH) and carboxylic (*COOH). The formate pathway confirms the conversion of *OCOH to *HCOOH with the rate-limiting potential (UL) of 0.39 eV for the production of HCOOH, while for the carboxylic pathway, the conversion of *COH to *CHOH has a UL of 0.32 eV, eventually producing CH3OH. Our findings highlight the role of Cu-BPH as an efficient SAC for CO2 catalytic activity to C1 products, as compared to the state-of-the-art Cu, and holds promise as an electrocatalyst for CRR.

Synthesis, characterization, and Hirshfeld surface analysis of coordination compounds composed of two different aminopyridines, isothiocyanate ligand molecules, and two different transition metal atoms.

In this article, we describe the successful synthesis of three coordination compounds formed by the ligands 3-aminopyridine, 4-aminopyridine, and isothiocyanate ion with copper atoms and 4-aminopyridine and isothiocyanate ion with cadmium atoms, and their structural characterizations. The crystal structures of the compounds were determined by single crystal X-ray diffraction. According to that technique, the open formulae of these compounds are [Cu(3-aminopyridine)2(NCS)2] (1), [Cu(4-aminopyridine)3(NCS)2] (2), and [Cd(4-aminopyridine)2(NCS)Cl] (3). In addition, the suitability of the structures of the compounds was characterized by elemental analysis, thermal analysis, and Fourier transform infrared spectroscopy. The single crystal X-ray diffraction analyses of these coordination compounds showed that the first of these coordination compounds had a 1D crystal structure and the other two had a 3D crystal structure. N-H⋯S, N-H⋯N, N-H⋯Cl, N-H⋯π, and C-H⋯π bonds and their combinations were effective in the formation of the crystal structures of the said coordination compounds. The metal atoms [Cu(II), Cu(II), and Cd(II)] in these coordination compounds were surrounded by various ligand molecules in a square planar, square pyramidal, and octahedral arrangement, respectively. In order to investigate some chemical and structural properties of these coordination compounds, theoretical calculations were performed with the software package Gaussian 03. The highest occupied molecular orbital (HOMO), lowest occupied molecular orbital (LUMO), and natural bond orbital (NBO) values of the coordination compounds were used in these calculations. When the energy gap value between the HOMO and LUMO states of the compounds was examined, it was predicted that compound 3 may have lower kinetic stability, higher chemical activity, and lower semiconductor properties than all the other compounds. According to the Hirshfeld surface analysis of the compounds, C⋯H, S⋯H, H⋯H, and N⋯H interactions are generally seen in the crystal structures of all compounds. In addition, Cd⋯Cl, Cd⋯S, H⋯Cl, and Cl⋯Cl interactions also occur in compound 3.

Predicting potential hard materials in Nb[sbnd]B ternary boride: First-principles calculations

To identify potential superhard materials, we conducted a comprehensive theoretical investigation of the thermodynamic and kinetic stability, mechanical properties, electronic structure, Debye temperatures and melting point of sixteen ternary transition metal borides NbTMBx (x = 1, 2, 4 and TM = Ti, V, Fe, Co, Ni, Zr, Ru, Hf, W, Os) using first-principles methods. Our findings indicate that, with the exception of NbFeB, NbRuB, and NbWB, all other borides exhibit both thermodynamic and kinetic stability. Notably, NbTiB4, NbVB4, NbZrB4 and NbHfB4 demonstrate superior hardness and enhanced resistance to deformation, with NbTiB4 showing an impressive hardness value of 40.84 GPa, positioning it as a promising candidate for superhard materials. Both NbVB4 and NbTiB4 have very high Debye temperatures and melting points and can be used in high temperature environments. We further explored the mechanical properties of NbTiB4 at elevated temperatures by employing a combination of first-principles and quasi-static methods. Our analysis reveals that the elastic constants and moduli of NbTiB4 decrease with increasing temperature. Additionally, bonding analysis indicates that all NbB ternary borides exhibit hybridization involving metallic, ionic, and covalent interactions, resulting in the formation of exceptionally strong covalent bonds between boron atoms.

Kinetic Control over Social and Narcissistic Self-Sorting from Multicomponent Mixtures in Seed-Initiated Supramolecular Polymerization by Fine-Tuning of Steric Effects.

Supramolecular polymers offer an intriguing possibility to transfer molecular properties from the nano- to the mesoscale. Towards this achievement, seed-initiated supramolecular polymerization has emerged as a powerful tool, as it prevents unlimited growth and enables size control of the assembly outcome. However, the potential application of the seeding method in the context of complex supramolecular systems is hitherto unclear. Herein we demonstrate that minute differences in molecular design in direct proximity to intermolecular recognition sites govern the molecular packing and in turn dictate the efficacy of seeded polymerization processes. We introduce a stepwise increase in steric demand in the central amino acid residue of a diamide system, which gradually increases the rotational displacement within the aggregated state. This fine-tuning of the molecular packing directly affects the propensity of the different aggregates to act as seeds for the other supramolecular synthons. In turn this allows us to selectively target specific trapped monomer states in binary mixtures for social or narcissistic seeded polymerization.

Kinetic Control over Social and Narcissistic Self‐Sorting from Multicomponent Mixtures in Seed‐Initiated Supramolecular Polymerization by Fine‐Tuning of Steric Effects

Supramolecular polymers offer an intriguing possibility to transfer molecular properties from the nano‐ to the mesoscale. Towards this achievement, seed‐initiated supramolecular polymerization has emerged as a powerful tool, as it prevents unlimited growth and enables size control of the assembly outcome. However, the potential application of the seeding method in the context of complex supramolecular systems is hitherto unclear. Herein we demonstrate that minute differences in molecular design in direct proximity to intermolecular recognition sites govern the molecular packing and in turn dictate the efficacy of seeded polymerization processes. We introduce a stepwise increase in steric demand in the central amino acid residue of a diamide system, which gradually increases the rotational displacement within the aggregated state. This fine‐tuning of the molecular packing directly affects the propensity of the different aggregates to act as seeds for the other supramolecular synthons. In turn this allows us to selectively target specific trapped monomer states in binary mixtures for social or narcissistic seeded polymerization.