Complexation Research Articles

Immobilization and coordination chemistry of Friedel’s salt (Ca/Al-LDHs) on heavy metals removal

Friedel’s salt (F’s salt, FS, Ca/Al-LDHs) was prepared via coprecipitation synthesis to remove Pb(II) and Zn(II). The adsorption of F’s salt on Pb(II) and Zn(II) was a physical adsorption process and could be well described by pseudo-second order kinetics. The adsorption process is mainly completed by surface adsorption of pore structure and interlayer structure. In addition, the crystal microstructure parameter, molecular structure and elemental spatial distribution analysis results demonstrated that Pb(II) and Zn(II) could form new solid solutions such as Pb/CaAl-Cl-LDHs, CaZn/Al-Cl-LDHs and Zn/CaAl-Cl-LDHs via lattice replacement, and then effectively immobilized in F’s salt crystals. Unlike Pb(II), there are two fixed lattice substitution pathways for Zn(II), that is, Ca(II) and Al(III) can be used as replacement objects. Notably, the chemical bonding mechanism is more prominent for the solidification of Pb(II) than that of Zn(II) in F’s salt. Moreover, the superficial coordination chemistry analysis results revealed that the abundant OH groups distributed in the main layer laminate structure can also serve as the binding sites for Pb(II) and Zn(II). This study provides a theoretical basis and novel insights into the immobilization mechanism of Pb(II) and Zn(II) in F’s salt.

Exploring the Anti-Urolithiatic Potential of White Seeds from Abrus Precatorius Via In Vitro Investigations

Medicinal plants are a valuable aspect of local heritage with global importance, often used as remedies for various health conditions. Their therapeutic properties are linked to a wide variety of complex chemical compounds, particularly secondary metabolites, found in different plant parts. Identifying the specific components responsible for medicinal effects is essential. Phytochemicals, which are abundant in medicinal plants, are generally considered safer and less toxic compared to synthetic alternatives. In line with this understanding, the present research investigates the in vitro anti-urolithiatic potential of white seeds of Abrusprecatorius. The seeds were chosen for their possible role in treating urolithiasis. Phytochemical screening of the plant extract revealed the presence of compounds such as flavonoids, coumarins, saponins, proteins, glycosides, quinones, and tannins.Two In Vitro assays, Crystal Nucleation and Aggregation, were performed, both with and without inhibitors. The study tested various concentrations of plant extracts (50mg/ml, 100mg/ml, 150mg/ml, 200mg/ml, and 250mg/ml) using four solvents: water, ethanol, chloroform, and petroleum ether, to assess their effect on calcium oxalate (CaOX) crystal formation, which is a primary component of kidney stones.Among the extracts tested, the water extract showed the highest inhibition of nucleation (85%) at a concentration of 250mg/ml. Aqueous, ethanol, and chloroform extracts exhibited notable anti-urolithiatic activity across different concentrations. Crystal aggregation was assessed using a spectrophotometer, and the water extract demonstrated the highest inhibition (78%) at the same concentration. Additionally, the chloroform extract showed significant anti-urolithiatic activity.When comparing extracts, the chloroform extract at 500mg/ml was the most effective in inhibiting the growth of calcium oxalate crystals. Overall, the study highlights the potential of Abrusprecatorius white seed extracts in inhibiting calcium oxalate crystal nucleation, aggregation, and growth, suggesting their potential as a treatment for urolithiasis. These results underscore the value of these extracts as promising agents in managing kidney stones

Recent progress on photoactive nonprecious transition-metal complexes

Recent progress on photoactive nonprecious transition-metal complexes

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.

QUANTUM-CHEMICAL AND AGROCHEMICAL INVESTIGATIONS OF Cu++ METAL COMPLEX BASED ON HYDROXYBENZOIC ACIDS

The crystal arrangement of molecules is necessary to determine what kind of supramolecular structures (2- or 3-dimensional framework) are formed as a result of intermolecular interactions, furthermore, it depends on the physicochemical properties of the crystal, for example, melting temperature, solubility, stability, activity and etc.. However, such qualitative analysis can be replaced by quantitative analyzes based on quantum-chemical approaches. One of them is based on the calculation of a surface with the same electron charge density, called the Hirshfeld surface. In our case, the main contribution of intermolecular interactions of mixed-ligand metal complex [Cu(PHBA)2(MEA)2] by Hirshfeld surface analysis and quantum chemical DFT calculations has shown that that they correspond to strong H‧‧‧O/O‧‧‧H bonds. Using DFT calculations, it was calculated that an odd electron MO (doublet state) arises when a complex is formed due to an odd d (d9) orbital in the Cu2+ ion of the compound [Cu(PHBA)2(MEA)2]. By the molecular docking studies the investigated complex compound [Cu(PHBA)2](MEA)2] recorded stronger binding energies than auxins taken as a control. The compound [Cu(PHBA)2](MEA)2], which showed the strongest performance, had a result 6% higher than the highest performing natural auxin. Quant-chemical calculation results are tested by agrochemical investigations on the mungbean plant

Unraveling the noncovalent interactions in a organic crystal using Quantum theory of atoms in molecules

X-ray diffraction analysis, combined with the Quantum Theory of Atoms in Molecules (QTAIM), serves as a powerful tool for describing chemical bonding in real space for solids. By integrating theoretical and experimental data, a more accurate representation of atomic interactions including Van der Waals forces, hydrogen bonds, covalent, ionic, and metallic bonds is achieved. The analysis of noncovalent interactions through electronic density enables the identification of Lewis acid and base sites, while also revealing the directional ‘key-lock’ interactions that correspond to molecular recognition. The examination of critical points in the electron density and its derivatives allows for the characterization of the types of interactions present in crystal packing. This study focuses on the experimental and theoretical investigation of noncovalent interactions within a molecular crystal of a newly synthesized carbohydrazide derivative. The crystal structure was determined using X-ray single-crystal diffraction, and the crystallographic asymmetric unit was optimized via DFT, with the results compared to experimental data. Noncovalent interactions in real space such as Van der Waals forces, hydrogen bonds, and inter- and intramolecular steric repulsions were analyzed in terms of electron density and its derivatives. The QTAIM framework was applied to quantify the strength of these interactions, employing Voronoi deformation density and electron localization and delocalization indices for solids. The results presented in this work, using crystal engineering, reveal that derivatives of diurea compounds crystallize following a characteristic pattern that forms a synthon configuration. The strength of this interaction, quantified through QTAIM analysis of the electronic density, provides a deeper understanding of the chemistry of these compounds, both in terms of biological activity and coordination chemistry.

Triscyanocorrole, the Newest and Most Intriguing Member of the C1-Substituted Corrole Family.

Considering the potential advantages of minimally sized corroles for diverse applications, this study reports a facile access to cyano-substituted derivatives via a rare CF3/CN conversion. Investigation of the fully characterized gallium, phosphorus, and cobalt complexes discloses multiple effects of the meso-nitrile groups attached to the macrocycle. This corrole appears to be the most electron poor derivative which comes into play in the redox potentials of the corresponding complexes. Compared to its precursor, both the absorption and emission are strongly red shifted and the fluorescence lifetime and quantum yield are much larger. The coordination chemistry is affected as well, by virtue of axial ligands being perpendicular rather than parallel relative to each other.

Stereocontrolled Synthesis of Chiral Helicene‐Indenido ansa‐ and Half‐Sandwich Metal Complexes and Their Use in Catalysis

AbstractDespite recent tremendous progress in the synthesis of nonplanar chiral aromatics, and helicenes in particular, their conversion to half‐sandwich or sandwich transition metal complexes still lags behind, although they represent an attractive family of modular and underexplored chiral architectures with a potential catalytic use. In this work, starting from various chiral helicene‐indene proligands, we prepared the enantio‐ and diastereopure oxa[6]‐ and oxa[7]helicene‐indenido half‐sandwich RhI and RhIII complexes and oxa[7]helicene‐bisindenido ansa‐metallocene FeII complex. To document their use, oxahelicene‐indenido half‐sandwich RhIII complexes were employed as chiral catalysts in enantioselective C−H arylation of benzo[h]quinolines with 1‐diazonaphthoquinones to afford a series of axially chiral biaryls in mostly good to high yields and in up to 96 : 4 er. Thus, we developed stereocontrolled synthesis of chiral helicene‐indenido ansa‐ and half‐sandwich metal complexes, successfully demonstrated the first use of such helicene Cp‐related metal complexes in enantioselective catalysis, and described an unusual sequence of efficient central‐to‐helical‐to‐planar‐to‐axial chirality transfer.

Stereocontrolled Synthesis of Chiral Helicene-Indenido ansa- and Half-Sandwich Metal Complexes and Their Use in Catalysis.

Despite recent tremendous progress in the synthesis of nonplanar chiral aromatics, and helicenes in particular, their conversion to half-sandwich or sandwich transition metal complexes still lags behind, although they represent an attractive family of modular and underexplored chiral architectures with a potential catalytic use. In this work, starting from various chiral helicene-indene proligands, we prepared the enantio- and diastereopure oxa[6]- and oxa[7]helicene-indenido half-sandwich RhI and RhIII complexes and oxa[7]helicene-bisindenido ansa-metallocene FeII complex. To document their use, oxahelicene-indenido half-sandwich RhIII complexes were employed as chiral catalysts in enantioselective C-H arylation of benzo[h]quinolines with 1-diazonaphthoquinones to afford a series of axially chiral biaryls in mostly good to high yields and in up to 96 : 4 er. Thus, we developed stereocontrolled synthesis of chiral helicene-indenido ansa- and half-sandwich metal complexes, successfully demonstrated the first use of such helicene Cp-related metal complexes in enantioselective catalysis, and described an unusual sequence of efficient central-to-helical-to-planar-to-axial chirality transfer.

Development of Neural Network Potentials for Studying Chemical Behaviors of La3+/Nd3+ Ions in Molten LiCl-KCl-CsCl in Combination with Raman Spectroscopy.

The chemistry of molten salts has attracted great research interest owing to their wide applications in diverse fields. In the pyrochemical reprocessing of spent nuclear fuel or molten salt nuclear reactors, lanthanide elements as the principal fission products bring about changes in the composition and properties of molten salts. Herein, we report a comprehensive study on the coordination chemistry of the representative trivalent lanthanide ions (La3+/Nd3+) in LiCl-KCl-CsCl using a multiscale strategy combining Raman spectroscopy, deep learning, and large-scale molecular dynamics (MD) simulations. The neural network potential (NNP)-based MD and Raman spectroscopy studies revealed that La3+/Nd3+ ions prefer to form persistent octahedron complexes with the six-coordinated species as the dominant species at high temperatures. Compared to LaCl63-, NdCl63- shows higher stability with obviously longer lifetimes in LiCl-KCl-CsCl, as confirmed by the observed stronger interaction of Nd3+-Cl- pairs. The total and partial structure factors further indicated the formation of a more stable network structure in LiCl-KCl-CsCl containing NdCl3. Besides, the temperature exerts a larger influence on the local structures of the La3+ species compared to the Nd3+ analogues. According to the potential mean force calculations, the bond dissociation energies follow the order Ln-Cl > Li-Cl > K-Cl > Cs-Cl in LiCl-KCl-CsCl-LnCl3. The NNP-based large-scale MD simulations have been verified to be an efficient and powerful way in molten salt chemistry research.

Significantly enhanced mechanical properties of NiCoV medium-entropy alloy via precipitation engineering

Precipitation engineering is one of the most effective means to enhance the strength of an alloy, which essentially requires precipitates with certain deformability, fine size, and uniform distribution. However, for multicomponent alloy systems, the chemical complexity poses significant difficulties in applying this strengthening method due to the diversity and brittleness of the potential precipitate phases. In this work, we demonstrated the precipitation engineering in a chemically complex prototype alloy NiCoV. Specifically, formation of detrimental σ, μ and Heusler phases was avoided by reducing the V content, and a two-step short-term annealing was designed to trigger homogeneous κ nucleation while inhibiting its rapid coarsening. It is found that both grain and phase boundaries can trap V atoms, which not only pins these interfaces but also hinders the V partitioning needed for κ growth. Consequently, we achieved an ultrafine κ/γ architecture in the NiCoV0.9 alloy, which surprisingly exhibited an ultrahigh yield strength of 1.6 GPa and a total work-hardening amount of 219 MPa. Our analysis indicates that the hetero-deformation induced (HDI) stress is mainly responsible for the high strength, while the coherent nature of phase boundaries and decent deformability of κ alleviate stress concentration, giving rise to the pronounced work-hardening. Our work highlights the importance of suitable phase selection and delicate substructure tailoring in precipitation engineering, with key findings also useful for enhancing overall mechanical properties in other multicomponent alloys.

Complexes of Iron(II), Cobalt(II), and Nickel(II) with DOTA-Tetraglycinate for pH and Temperature Imaging Using Hyperfine Shifts of an Amide Moiety.

Paramagnetic complexes of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA4-) derivatives have shown potential for molecular imaging with magnetic resonance. DOTA-tetraglycinate (DOTA-4AmC4-) coordinated with lanthanide metal ions (Ln3+) demonstrates pH/temperature sensing with Biosensor Imaging of Redundant Deviation in Shifts (BIRDS) and Chemical Exchange Saturation Transfer (CEST), respectively, detecting nonexchangeable (e.g., -CHy, where 3 ≥ y ≥ 1) and exchangeable (e.g., -OH or -NHx, where 2 ≥ x ≥ 1) protons. Herein, we report paramagnetic complexes of divalent transition-metal ions (M2+ = Fe2+, Co2+, Ni2+) with DOTA-4AmC4- that endow a unique amide proton (-NH) moiety for pH/temperature sensing. Crystallographic data reveal that DOTA-4AmC4- coordinates with M2+ through oxygen and nitrogen donor atoms, ranging in coordination numbers from 8-coordinate in Fe(II)DOTA-4AmC2-, 7-coordinate in Co(II)DOTA-4AmC2-, and 6-coordinate in Ni(II)DOTA-4AmC2-. The -CHy protons in M(II)DOTA-4AmC2- displayed modest pH/temperature sensitivities, but -NH protons exhibited higher intensity, suggesting prominent BIRDS properties. The pH sensitivity was the highest for Ni(II)DOTA-4AmC2- (1.42 ppm/pH), followed by Co(II)DOTA-4AmC2- (0.21 ppm/pH) and Fe(II)DOTA-4AmC2- (0.16 ppm/pH), whereas temperature sensitivities were comparable (i.e., 0.22, 0.13, and 0.17 ppm/°C, respectively). The CEST image contrast for -NH in M(II)DOTA-4AmC2- was much weaker compared to that of Ln(III)DOTA-4AmC-. Given its high pH sensitivity and low cytotoxicity, Ni(II)DOTA-4AmC2- shows promise for use in preclinical BIRDS-based pH imaging.

Thermal and Luminescent Properties of Multi-Ligand Complexes of Europium(III) with Pyrazine-2-carboxylic Acid

Eu(III) compounds with pyrazine-2-carboxylic acid and nitrogen- and phosphorus-containing neutral ligands were synthesized. Using the methods of chemical elemental and thermal analysis and IR spectroscopy, the composition of the complexes and the method of coordination of carboxylate ions were established. The most thermally stable compounds have been identified. The luminescent characteristics of complex compounds have been studied. It was found that the maximum luminescence intensity is characteristic of europium(III) pyrazinate with triphenylphosphine oxide. The morphological structure and dispersion of the complexes were determined.

Affecting Charges and Structures of {Bi6} Architectures by 12‐Electron Transition Metal Fragments

AbstractMolecules based on polyatomic bismuth substructures are currently attracting a lot of attention owing to this heavy and essentially non‐toxic element's uncommon chemical and physical properties, which include unprecedented bonding properties. Hexaatomic {Bi6} substructures that underly more complex cluster structures were recently reported to adopt different structures or exhibit different structural details as a consequence of the charge of the {Bi6} unit. This leads to either crown‐shaped cycles for a nominal Bi66− or differently distorted trigonal prisms for compositions close to Bi62−. It was predicted by quantum chemistry that Bi64− should adopt a distinctly distorted boat‐like shape, yet a corresponding compound has remained elusive. Here, we report a proof of this assumption by the synthesis of [K(crypt‐222)]2[Bi6{Zn(hmds)}2] ⋅ 1.5THF (1), comprising a bimetallic [Bi6{Zn(hmds)}2]2− cluster that fulfills the prediction for the geometric and electronic structure of the missing link (crypt‐222=4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo‐[8.8.8]hexa‐cosane, hmds=hexamethyldisilazanid). A detailed quantum chemical study shows how the nature of Lewis‐acidic transition metal complexes—in particular, 12‐electron fragments—control and fine‐tune the resulting {Bi6} architectures in accordance with the degree of electron‐withdrawal from the polybismuthide core.

Effect of the Pyrolysis Environment in a Complex Compound in the Synthesis of In0.6Ga0.4N Powders and their Characterization

In this work, the comparison between nitrogen and air synthesis environments in obtaining In0.6Ga0.4N powders is presented, and the effect of how the air environment can reduce the pyrolysis temperature of In0.6Ga0.4N powders to 271 °C using the thermal gravimetric analysis, and derivative thermogravimetry methods. X‐ray diffraction patterns demonstrate the presence of a cubic phase in nanocrystallites, in addition to less presence of the hexagonal phase. In contrast, scanning electron microscopy micrographs show a surface morphology of irregular agglomerates with a porous appearance and the presence of nonuniform plates. Energy‐dispersive spectroscopy and X‐ray photoelectron spectroscopy spectra demonstrate the presence of elemental contributions of gallium, indium, and nitrogen. At the same time, transmission electron microscopy shows the cubic structure and an interplanar distance of 2.7 Å for the (200) plane. Raman scattering shows the presence of E2(high) vibration mode for the hexagonal phase with a value of 560 cm−1. Finally, the photoluminescence spectrum shows an energy emission at 1.39 eV (886 nm), which is associated with the emission of the In0.6Ga0.4N powders.

Affecting Charges and Structures of {Bi6} Architectures by 12-Electron Transition Metal Fragments.

Molecules based on polyatomic bismuth substructures are currently attracting a lot of attention owing to this heavy and essentially non-toxic element's uncommon chemical and physical properties, which include unprecedented bonding properties. Hexaatomic {Bi6} substructures that underly more complex cluster structures were recently reported to adopt different structures or exhibit different structural details as a consequence of the charge of the {Bi6} unit. This leads to either crown-shaped cycles for a nominal Bi6 6- or differently distorted trigonal prisms for compositions close to Bi6 2-. It was predicted by quantum chemistry that Bi6 4- should adopt a distinctly distorted boat-like shape, yet a corresponding compound has remained elusive. Here, we report a proof of this assumption by the synthesis of [K(crypt-222)]2[Bi6{Zn(hmds)}2] ⋅ 1.5THF (1), comprising a bimetallic [Bi6{Zn(hmds)}2]2- cluster that fulfills the prediction for the geometric and electronic structure of the missing link (crypt-222=4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo-[8.8.8]hexa-cosane, hmds=hexamethyldisilazanid). A detailed quantum chemical study shows how the nature of Lewis-acidic transition metal complexes-in particular, 12-electron fragments-control and fine-tune the resulting {Bi6} architectures in accordance with the degree of electron-withdrawal from the polybismuthide core.

A Convenient Approach for the Synthesis of Multidentate N-Heterocyclic Carbene Ligand Precursors.

Multidentate bis-NHCs ligands with various spacers are expected to combine the advantages of coordination chemistry and catalysis. These offer opportunities to construct various organometallic frameworks involving transition metals and main group elements. Therefore, developing a general procedure for synthesizing a variety of carbene salt precursors using a convenient technique is key in this context. The extended protocol of a solvent-free approach for synthesizing various bridged bis-imidazolium carbene salts, including tris and tetrakis-imidazolium precursors, is reported here. This method can be performed in the laboratory, leading to high yields (80-95 %) and isolated as analytically pure, multigram, bench-stable compounds.

Investigating the effect of fermentation byLactobacillus reuteri on biochemical properties of Ceylon Cinnamon

Abstract Introduction Fermentation is an important biotechnological process that improves the biochemical properties of natural raw materials by transforming high molecular compounds into more beneficial low molecular compounds through microbial biotransformation. Ceylon cinnamon (Cinnamomum zeylanicum Blume), globally recognized as 'true cinnamon', contains high molecular weight, complex compounds that are responsible for its renowned antioxidant, antibacterial, and therapeutic properties, making it a vital component in medicinal applications1. Aims The present study aimed to investigate the effect of fermentation by Lactobacillus reuteri on selected phytochemical contents, antioxidant, and antibacterial properties of bark extracts of Ceylon cinnamon (Cinnamomum zeylanicum Blume) and to determine the optimum conditions for fermentation of Cinnamon bark extract by L. reuteri. Method Authenticated Ceylon cinnamon bark (CCB) was extracted into water using the decoction method. The water extract was fermented by L. reuteri under controlled conditions (pH 6, incubation at 35 ºC) and optimized using two parameters; the inoculum density (1.5×108 cfu/ml and 7.5×108 cfu/ml) and incubation time (2 and 4 days). After fermentation, total polyphenolic content (TPC), total flavonoid content (TFC), DPPH free radical scavenging activity and antibacterial activity of non-fermented extracts (NFE) and fermented extracts (FE) of CCB were evaluated. Antibacterial activity was determined using the agar well diffusion method against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Ethical approval was not required since no human or animal study was done during the study. Results The extract fermented with an inoculum density of 7.5×108 cfu/ml and incubated for 4 days showed the highest TFC (19.3 ± 0.3 mg RE/g) and antioxidant activity (IC50: 97.2 ± 0.8 µg/ml) in comparison to that of NFEs (TFC:13.3 ± 0.3 mg RE/g and DPPH activity: IC50: 233.7 ± 12.8 µg/ml). Moreover, the fermented samples showed a reduction in TPC, indicating possible biotransformation of compounds. and no significant change in the antibacterial activity in comparison to the non-fermented samples. Discussion and Conclusion This study was mainly focused on investigating the effect of fermentation of Ceylon cinnamon bark aqueous extract by Lactobacillus reuteri. The increased antioxidant activity and total flavonoid content are notable and could be attributed to chemical transformations of some complex flavanols including catechin gallate and epicatechin gallate present in aqueous cinnamon to catechin and epicatechin monomers by the action of enzymes secreted by L. reuteri during the fermentation process2. Hence, this study suggests that fermentation using L. reuteri has a considerable positive impact on certain biochemical properties of cinnamon water extract. Cinnamon bark is a complex matrix containing various phytochemicals that could interact with bacterial strains in ways that are not fully understood. These interactions could lead to unexpected effects or limitations during fermentation.

A comprehensive investigation of the impact of carbon-supported metal complexes of triaminoguanidine on the characteristics of a double-base propellant

ABSTRACT In this study, triaminoguanidine complexes grafted onto activated carbon (AC-TAG-Fe and AC-TAG-Co) were designed and investigated for their catalytic effect on the thermolysis of a double base propellant consisting of nitrocellulose (NC) and diethylene glycol dinitrate (DEGDN). The successful synthesis of transition metal complexes with triaminoguanidine and their subsequent grafting onto activated carbon were confirmed using various analytical techniques, including Fourier Transform Infrared Spectroscopy, Raman Spectroscopy, X-ray Diffraction, and Scanning Electron Microscopy. Thermal characterization using Thermogravimetric Analysis and Differential Scanning Calorimetry provided valuable insights into the thermal properties and reactivity of the elaborated NC/DEGDN-based composites. Importantly, the addition of various additives resulted in notable improvements in both the enthalpy of reaction and density. Isoconversional kinetic studies revealed that the incorporation of TAG-Fe and TAG-Co complexes reduced the apparent activation energy of the NC/DEGDN composite from 137.4 kJ/mol to 135.4 kJ/mol and 114.8 kJ/mol, respectively, suggesting their catalytic effect. Furthermore, it is found that the addition of activated carbon (AC) resulted in an increase in activation energy to 154 kJ/mol, whereas grafting TAG-Fe and TAG-Co complexes onto AC as a catalytic support subsequently reduced activation energy to 119 kJ/mol and 112 kJ/mol, respectively. Overall, this research serves as a valuable reference for future studies focusing on investigating the catalytic combustion characteristics of double-base solid propellants.

Synthesis, spectral characterisation, DFT calculations, biological evaluation and molecular docking analysis of new Mannich compounds derived from cyclopentanone

This research outlines the efficient one-pot calcium chloride-catalysed synthesis of three novel Mannich bases: M1, M2 and M3. M1 and M2 resulted from the condensing of benzaldehyde with m-nitroaniline and m-bromoaniline, respectively, in conjunction with cyclopentanone. However, M3 was obtained through the reaction of p-methoxybenzaldehyde, m-bromoaniline and cyclopentanone. The isolated compounds were thoroughly characterised using elemental analysis and various analytical and spectroscopic techniques, including the determination of their melting points, electrospray mass spectrometry (ESMS), Fourier transform infrared (FTIR), electronic spectroscopy (UV–Vis), and nuclear magnetic resonance (NMR) spectroscopy (1H- and 13C NMR). Thermal stability (TGA and DTA analysis) of the three Mannich compounds was also examined. The newly synthesised Mannich bases exhibit remarkable potential as metal ion complexing agents and as fundamental building blocks for forming small organic molecules, particularly bioactive molecules and novel ligands for coordination chemistry. In addition to their structural significance, the biological efficacy of these compounds was assessed, revealing their excellent antimicrobial properties toward bacterial and fungal species. These activities suggest their potential use in combating microbial infections. Theoretical DFT simulations employing the B3LYP functional at the 6-311++G(d,p) level provided a thorough analysis of the stability of compounds, electrical properties, and geometry. Additionally, molecular docking studies of the Mannich compounds with two protein targets, 5IQ9 and 5VBU (both relevant for drug discovery) were performed. These studies revealed that the three Mannich compounds exhibit similar binding energies and effective interaction with both the 5IQ9 and 5VBU proteins, suggesting the potential of these Mannich compounds as dual inhibitors targeting both proteins.