Monoclinic Research Articles

Monoclinic α-Bi2O3 nanorods by microwave-assisted synthesis: Photocatalytic and antioxidant properties

Nanotechnology has emerged as a new route for addressing most environmental and medical challenges, hence this field of research continues to generate research interest. Herein, Bi2O3 was synthesized by a microwave-assisted thermal process. X-ray diffraction (XRD) result confirmed that a nanocrystalline monoclinic crystal structure of the α-phase was formed, and both the Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) analysis confirmed that the synthesized α-Bi2O3 were rod-like in shape. The length of the nanorods was in the range of 60–160 nm, with an average dimension of 101.5 nm, while the width has an average value of 23 nm. A band gap energy value of 2.75 eV was obtained from the absorption spectroscopy, and they absorbed light in the UV to visible range, with an absorption maximum of around 345 nm. Photocatalytic activity of the nanorods under UV irradiation was investigated by assessing the degradation of Bromocresol green (BG) as a model pollutant. The degradation process of the dye molecules was studied at different concentrations (20–80 mg/L), varied photocatalyst dosage (0.025, 0.05, 0.075, and 1.0 g), and a range of solution pH (3, 6, 9, and 12). About 75 % optimum photocatalytic efficiency was achieved at pH 6 after 3 h. In addition, the results showed that an increase in catalyst dosage and concentration of dye molecules contributed to promoting the degradation effect. Moreover, the photocatalyst was found to be stable after 4 consecutive cycles, with negligible loss of efficiency. The antioxidant potency of the nanorods was assessed by evaluating their free radical scavenging capabilities across 4 different assays: 1,1-diphenyl-2-picrylhydrazyle (DPPH), Nitric oxide (NO), Hydrogen peroxide (HP) radical inhibition, and Reducing power (RP). The results from the IC50 values indicated the sample exhibited better inhibition of HP (25.22 µg/mL), followed by RP (28.22 µg/mL), NO (29.37 µg/mL), and DPPH (32.72 µg/mL) respectively. However, the standard Ascorbic acid exhibited IC50 values of 16.25, 24.50, 25.07, and 28.40 µg/mL for DPPH, RP, HP, and NO, respectively. These unique properties of the nanorods showed that they have good antioxidant potential that is comparable with that of Ascorbic acid used as the standard.

Silver sulphide nanoparticles (Ag2SNPs) synthesized using Phyllanthus emblica fruit extract for enhanced antibacterial and antioxidant properties.

In this study, silver sulfide nanoparticles (Ag2SNP's) were successfully produced by using fruit extracts of Phyllanthus emblica. UV-vis, FTIR, XRD with SEM and EDX techniques were used for the synthesis process and for characterization of the resulting nanostructures. According to the findings, the fabricated nanostructure had a monoclinic crystal structure, measuring 44 nm in grain size, and its strain was 1.82 × 10-3. As revealed by SEM analysis, the synthesized nanostructure consists of irregular spherical and triangular shapes. The presence of silver (Ag) and sulfur (S) was also confirmed through EDX spectra. Furthermore, Ag2S nanoparticles were tested for their ability to effectively inhibit gram-positive and gram-negative bacterial growth. As a result of this study, it was clearly demonstrated that Ag2S nanoparticles possess powerful antibacterial properties, particularly when it came to inhibiting Escherichia coli growth. Ag2S nanoparticles had high total H2O2 and flavonoid concentrations and the greatest overall antioxidant activity, according to the evaluation of antioxidant activity of the samples. The results obtained from the P. emblica fruit extract were followed by those obtained from Ag2S nanoparticles were reported in detail. RESEARCH HIGHLIGHTS: Innovative Ag2SNP synthesis using Phyllanthus emblica fruit extract. SEM with EDX revealed a monoclinic crystal structure with a grain size of 44 nm and a strain of 1.82 × 10-3. Many of these applications are demonstrated by the potential of Ag2SNPs to treat and combat bacteria, particularly Escherichia coli. A peak at 653 cm-1 indicates the presence of primary sulfide aliphatic C-S extension vibrations. The abundant H2O2 and NO2 found in P. emblica nanocomposites make them potent antioxidants.

Structural characterization of benzoate anion-supported supramolecular assemblages of Co(III) and Ni(II) cyclam compounds with catecholase-like and antibacterial activities

Two mononuclear compounds, cis-[Co(cyclam)(Bz)2](Bz)·H2O (1), and trans-[Ni(cyclam)(H2O)2](MOBA)2·4H2O (2) (where Bz = benzoate and MOBA = o-methoxy benzoate) have been synthesized and characterized by elemental analyses, spectroscopy, X-ray diffraction, and thermogravimetric techniques. Compounds 1 and 2 crystallize in a monoclinic crystal system with P21/c and P21/n space groups, respectively. The carboxylate ligand in compound 1 enables the cyclam ligand to adopt a cis-V conformation, while in compound 2, cyclam adopts a stable trans-III conformation. Hirshfeld surface analyses were carried out to elucidate the intricate intermolecular forces shaping the crystal structure. The ability of compounds 1 and 2 to imitate the activities of the catechol oxidase enzyme was evaluated using 3,5-di-tert-butyl catechol (3,5-DTBC) as the model substrate. The antibacterial activity was investigated using the Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacterial strains. Interestingly, compound 1 exhibited higher catecholase-like activity than compound 2 and enhanced antibacterial activity.

Stereoisomers of oxime ethers of 1,4-naphthoquinone: Synthesis, characterization, X-ray crystal structures, and DFT studies

In the present work, we use the C-3 substituted 2-hydroxy-1,4-naphthoquinones viz. 2-hydroxynaphthalene-1,4-dione (1), 2-hydroxy-3-methylnaphthalene-1,4-dione (2), and 2-chloro-3-hydroxynaphthalene-1,4-dione (3) as starting materials and obtained naphthoquinoneoxime ethers viz. 3-hydroxy-4-(methoxyimino)naphthalen-1(4H)-one (4), 3-hydroxy-4-(methoxyimino)-2-methylnaphthalen-1(4H)-one (5) and 2-chloro-3-hydroxy-4-(methoxyimino)naphthalen-1(4H)-one (6) via a facile and efficient synthesis involving condensation with methoxyamine hydrochloride. X-ray structure showed that 4 belongs to the orthorhombic (P212121) space group, whereas 5 and 6 (P21/c) crystalize in the monoclinic crystal system. The isomer ratios derived from NMR experiments elucidating stereoisomerism in compounds comprised of carbon-nitrogen double bonds have been analyzed; the naphthoquinone oxime ethers 4, 5, and 6 were also characterized employing the ωB97x-D/6–311++G (d, p) level of density functional theory. Theoretical studies reveal different conformational isomers with the ‘amphi’ and ‘syn’ isomers as low-lying structures along their energy hierarchy in accordance with the X-ray crystallography data. The spectral characterization of vibrational frequencies and 1H /13C NMR chemical shifts in unison with experiments and theory has been presented.

Effect of water-based electrolyte on surface, mechanical and tribological properties of ZrO2 nanotube arrays produced on zirconium

In this work, highly ordered ZrO2 nanotube arrays were fabricated on commercial pure Zr substrates through anodic oxidation in the water-based electrolyte at various voltages (30 V, 40 V and 50 V) for 1 h. The monoclinic- and tetragonal-ZrO2 phases were obtained on ZrO2 nanotubes through anodic oxidation. 13 vibration modes have been observed for the samples grown at low voltages (30 V and 40 V), which are assigned to monoclinic symmetry (7Ag + 6Bg), while—with the increasing growth voltage, the dominant phonon peak intensities associated with the monoclinic symmetry 6 times are decreased, and Eg (268 and 645 cm − 1) mode corresponding to tetragonal symmetry is observed. The nanotube array surfaces exhibited hydrophilic and super-hydrophilic behavior compared to the bare Zr surface. The elastic modulus values of ZrO2 nanotube surfaces (14.41 GPa) were highly similar to those of bone structure (10–30 GPa) compared to bare Zr substrate (120.5 GPa). Moreover, hardness values of ZrO2 nanotube surfaces were measured between ∼76.1 MPa and ∼ 283.0 MPa. The critical load values required to separate the nanotubes from the metal surface were measured between ∼1.6 N and ∼26.3 N. The wear resistance of the ZrO2 nanotube arrays was improved compared to that of plain Zr substrate.

Discovery of a New Polymorph of 5-Methoxy-1H-Indole-2-Carboxylic Acid: Characterization by X-ray Diffraction, Infrared Spectroscopy, and DFT Calculations.

This study presents a new 5-methoxy-1H-indole-2-carboxylic acid (MI2CA) polymorph investigated by single-crystal X-ray diffraction, infrared spectroscopy, and density functional theory (ωB97X-D) calculations employing two basis sets (6-31++G(d,p) and aug-cc-pVTZ). The compound crystallizes in the monoclinic system, space group P21/c (a = 4.0305(2) Å, b = 13.0346(6) Å, c = 17.2042(9) Å, β = 91.871(5)°, Z = 4). In the crystalline structure, the formation of cyclic dimers via double hydrogen bonds O-H⋯O between MI2CA molecules was observed. Interactions between the NH groups of the indole rings and the adjacent methoxy groups, as well as C-H⋯O contacts, significantly influence the spatial arrangement of molecules. The results from DFT calculations, including dimeric and trimeric structures, agree well with the experimental structural and spectroscopic data. Analysis of the infrared spectra confirms the conclusions drawn from X-ray diffraction studies and reveals differences between the IR spectra of the newly obtained polymorph and that reported earlier in the literature. This comprehensive study sheds some light on the MI2CA polymorphism and is important for a potential pharmacological applications of this compound.

Synthesis, crystal structure analysis, catalytic and biological activities of (H2en)3{V10O28}.6H2O. An improved refinement

The hybrid material, (H2en)3{V10O28}.6H2O (1), containing decavanadate units was synthesized by a wet chemistry method using ethylenediamine (en) as a structure-directing agent. It crystallizes in the monoclinic system, space group C2/c, with cell parameters (Å, °): a = 20.2028 (3), b = 17.0629 (3), c = 10.5541 (2), β= 104.2045 (16). The crystal structure forms a 3D framework of isolated [V10O28]6− monomers, ethylenediammonium cations, and H2O molecules linked through NH···O and OH···O hydrogen bonds. The Fourier transform infrared spectroscopy exhibits characteristic bands corresponding to decavanadate groups and organic molecules. The thermal decomposition steps of the hybrid compound show mainly the loss of the organic moieties and the water molecules. The decavanadate compound's catalytic activity was evaluated by oxidizing methylene blue (MB) with hydrogen peroxide. The biological activity of 1 yielded mediocre results.

Piroxicam analogue metal complexes: Synthesis, crystal structures, molecular modeling and biological studies

In recent decades, metal‐based drugs have gained considerable attention all over the world because of their enhanced therapeutic potential. The piroxicam analogue, that is, 2‐Benzyl‐4‐hydroxy‐1,1‐dioxo‐1,2‐dihydro‐1λ6‐benzo [e][1,2] thiazine‐3‐carboxylic acid pyridin‐2‐yl amide 1 was synthesized and coupled with Mn (II), Co (II), Ni (II), Cu (II) and Zn (II) metal ions to isolate complexes 2–6. The N,O‐bidentate chelator coordinated with the metal center via pyridyl nitrogen and amide oxygen atoms by forming six‐membered ring system. Several analytical techniques like UV–Vis, FT‐IR, 1H NMR, magnetic susceptibility, and elemental analysis were performed to confirm the syntheses of the octahedral complexes. The conductance measurement was employed to determine the non‐electrolytic nature of the complexes. The molecular structures of manganese (II) 2, cobalt (II) 3, and zinc (II) 6, complexes were confirmed by single beam X‐ray crystallography revealing the monoclinic crystal system with P21/c space group. The crystallographic data was utilized to carry out the DFT studies, which were found in line with the experimental data. The antioxidant (DPPH, FRAP) and antibacterial activities were performed to determine the therapeutic potential of these synthesized compounds. These studies indicated that understudied compounds have potential as therapeutic agents and they may be used as drug candidates in the future. The in‐silico studies also aligned with the in‐vitro potential of the targeted compounds.

Evaluation of structural parameters of monoclinic nanocrystalline CuO and study of sunlight-driven photocatalytic dye degradation, antimicrobial and antioxidant potential

Highly pure, crystalline and spherical-shaped Copper oxide nanoparticles (NPs) have been synthesized via facile chemical coprecipitation. Various models including the Scherrer, Monshi-Scherrer, Williamson-Hall, Size-Strain Plot and Halder-Wagner method have been applied to study the crystal structure characteristics. The lattice parameters associated with the monoclinic crystal lattice of CuO NPs were estimated to be a = 4.69 Å, b = 3.41 Å, c = 5.14 Å and β = 99.87(degree), unit cell volume V = 81.35Å3 and cell density dx = 6.49 g/cm3. The photocatalytic dye degradation proficiency at 20 mg/l CuO concentration and 120 min sunlight exposure results the order of percentage dye degradation Malachite Green (88.4%) > Crystal Violet (70.8%) > Eosin Yellow (70.2%) > Methylene Blue (54.08%) dyes. The antimicrobial activity assessment was done against the broad-spectrum pathogenic microbes unveiled the exceptional microbial controlling capability of CuO NPs. Furthermore, the antioxidant activity test demonstrated the potential free radical scavenging activity of CuO NPs with an IC50 value of 47.733 µg/ml. Highlights Synthesis of pure and spherical shaped nanocrystalline CuO was done by using low cost and facile chemical coprecipitation method. XRD, FTIR, FESEM, EDX, UV-Vis, and Raman spectroscopic techniques were used for characterization purpose. The structural and crystallographic parameters of monoclinic crystal structure of CuO NPs were evaluated successfully. The photocatalytic performance of CuO NPs follow the percentage dye degradation order as MG (88.4%) > CV (70.8%) > EY (70.20%) > MB (54.08%) after 120 minutes of sunlight exposure. CuO NPs exhibit promising antifungal activity against COVID-19 associated Pulmonary Aspergillosis (CAPA) causing pathogenic fung. CuO NPs show potential DPPH free radical scavenging activity with an IC50 value of 47.733 µg/ml.

New Polymorphic Structures of Uranyl Butyrate and Crotonate

AbstractNew polymorphs of diaquadicrotonato‐ and diaquadibutyratodioxidouranium(VI) were synthesized. X‐ray diffraction analysis at low and room temperatures revealed the monoclinic crystal system for both compounds at both room and low temperatures. New structures contain molecular complexes in which uranium atoms are coordinated by two bidentate carboxylate ions and two water molecules. The crystal structures feature the same packing motif that constitutes layers formed by hydrogen bonds. IR spectroscopy uncovered differences in vibrations of carboxyl and uranyl groups. Voronoi‐Dirichlet parameters of the synthesized compounds and some previously published uranyl carboxylates that have similar complex and crystal structures to the new ones were compared. The new structures demonstrate once again that the volume of Voronoi‐Dirichlet polyhedron of the uranium atom in U sublattice depends on the nature of carboxylate ion alkyl chain.

New Phases in the Sc−Mn−Si and Sc−Mn−Al−Si Systems Through Molten Indium Flux Synthesis

New Phases in the Sc−Mn−Si and Sc−Mn−Al−Si Systems Through Molten Indium Flux Synthesis

Crystal growth, physical and optical properties of TlSr2Cl5 and TlSr2Br5

Small diameter (Ø 16 mm) TlSr2Cl5 and TlSr2Br5 crystals were grown by the Vertical Bridgman method. X-ray diffraction measurements show that both have the monoclinic crystal structure with space group P21/c. TlSr2Cl5 and TlSr2Br5 have a density of 4.14 g/cm3 and 5.03 g/cm3, respectively. The effective Z of TlSr2Cl5 and TlSr2Br5 is 63.7 and 58.6, respectively. Radioluminescence spectra of TlSr2Cl5 and TlSr2Br5 feature a broad emission band peaking at 440 and 445 nm, respectively. The light yield of TlSr2Cl5 and TlSr2Br5 was estimated to be 17,000 and 45,000 ph/MeV, respectively.

Synthesis and Crystal Structure Studies of a New Complex of Co (III)-Schiff Base Derivative Derived from Isonicotinohydrazide

A new Co(III) complex prepared by the reaction of N'–(1–(pyridin–2 yl)ethylidene) isonicotinohydrazide (H2L) with Co(II) ion is reported in this paper. The H2L ligand is structurally characterized by elemental analysis, NMR, and infrared spectroscopies. The mononuclear complex [Co(HL)2]·Cl·3H2O (1), is characterized by infrared spectroscopy, elemental analysis, conductance, magnetic room temperature measurement and single X-ray diffraction. The complex crystallizes in the monoclinic system with space group P21/c. The parameters of the unit cell are a = 9.6818(3) Å; b = 25.1587(6) Å; c = 11.5481(3) Å; β = 101.797(3) °; Z = 4; Rint = 0.0313 and wR(F2) = 0.0812. The asymmetric unit of the compound contains a discrete [Co(HL)2]+ cation one free chloride anion and three uncoordinated water molecules. In the discrete cation one Co3+ ion two organic ligand molecules are present. The coordination polyhedron around the Co3+ center is best described as a distorted octahedral with CoN4O2 chromophore. The crystal structure of the complex is stabilized by intramolecular and intermolecular hydrogen bonds.

The Ce-Ni-Si System Revisited: More Homologue Compounds?

The nickel-rich region of the system Ce-Ni-Si has been reinvestigated utilizing X-ray single-crystal, powder, and electron diffraction as well as electron microprobe and thermal analyses. Two novel hexagonal compounds, τ-Ce20+xNi36+ySi30-z and τ'-Ce30+xNi50+ySi42-z, were identified. The crystal structure of τ-Ce20+xNi36+ySi30-z was derived from single-crystal X-ray diffraction and found to be isotypic with the Sm10Ni20.8P15-type structure (S.G. P63/m, x = 1.8, y = 3.0, z = 1.8, a = 2.07156(2) nm, c = 0.39990(1) nm, RF = 0.048). Rietveld refinement of τ'-Ce30+xNi50+ySi42-z revealed isotypism with Tb15Ni28P21 (S.G. P63/m, a = 2.46926(13) nm, c = 0.40019(3) nm, RF = 0.058). The compound Ce3Ni4Si2 from X-ray single-crystal analysis was found to crystallize in a novel structure type with monoclinic unit cells (S.G. C2/c, a = 1.54708(3) nm, b = 0.58677(1) nm, c = 0.74331(1) nm, β = 102.985(1)°, RF = 0.017). This compound belongs to a new homologue series in the RE-Ni-Si system (RE = La and Ce) with general formula of RE(3×2n)Ni(3×2n+1)Si(2n+1); n = 0,1, ..., ∞. The crystal structure of this series is characterized by alternating numbers (2n) of corner-sharing Si-polyhedral blocks sandwiched between zigzag nickel chains. Higher-order members of this series are produced by the formation of more corner-sharing Si-polyhedral blocks due to removal of nickel chains.

Synthesis, structure, hirshfeld surface analysis and antibacterial activities of [Cd(2-ampy)3(NCS)(μ1,5-SCN)]2 and [Cd(4-ampy)2(μ1,5-dca)2]n complexes (2-ampy = 2-aminopyridine, 4-ampy = 4-aminopyridine, NCS = thiocyanate, dca = dicyanamide)

The complexes [Cd(2-ampy)3(NCS)(μ-SCN)]2 (1) and [Cd(4-ampy)2(μ1,5-dca)2]n (2) were synthesized and characterized using single crystal XRD. Complex 1 has a dimer structure with a triclinic crystal system and space group P1¯, whereas complex 2 has a polymer structure with a monoclinic crystal system and space group P21/c. Hirshfeld surface analysis of complex 1 showed the presence of S⋯N–H and N–H–S interactions between dimer molecules and intramolecular hydrogen bonds N–H⋯N. In complex 2, the analysis showed the polymer coordination chain bonds between Cd(II) ions with N atoms from dicyanamide and intermolecular hydrogen bonds of N–H⋯N. In vitro antibacterial testing for both complexes against Escherichia coli (gram-negative) and Staphylococus aureus (gram-positive) showed a higher inhibition zone diameter than the constituent reactants, where complex 2 had the a higher antibacterial activity.

Synthesis, characterization, antibacterial efficacy, and Cytotoxicity of monoclinic KMg3(Al0.5B0.5)Si3O10F2: A novel material for anticariogenic applications

Fluorophlogopite is a well-known fluorosilicate glass-ceramic derivative known for its bioactivity, machinability and optimal mechanical properties. There is limited information regarding its antibacterial and biocompatible properties. This research paper presents the synthesis and characterization of a novel Boron-doped Fluorphlogopite [KMg3(Al0.5B0.5)Si3O10F2] aiming to improve its antibacterial properties intended for anticariogenic applications. The combustion synthesis method was employed, with oxalyl dihydrazide (ODH) (C2H6N4O2) serving as the fuel. X-ray Diffraction (XRD) analyses unveiled a monoclinic crystal system, showcasing a P21 space group, and an average crystallite size of approximately 28 nm. Morphological scrutiny divulged clustered, irregularly shaped, cluster-like structures. The energy gap was determined to be around 4.97 ± 0.0062 eV. Fourier-Transform Infrared (FTIR) spectroscopy depicted the presence of characteristic bonds. BET analysis indicated the presence of a large surface area and porous structure (mesopores), which may contribute to lower MIC and MBC values, enhancing antibacterial effectiveness. The antibacterial activity, evaluated via agar well diffusion, yielded an 8 mm zone of inhibition. Furthermore, the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) against S mutans were determined to be 2 mg/ml and 16 mg/ml, respectively. The biocompatibility of the synthesized KMg3(Al0.5B0.5)Si3O10F2 was assessed through the MTT assay, indicating non-toxic behavior at a concentration of 12 μg/ml with 98 % cell viability, while showing moderate toxicity with 61 % viable cells at its highest concentration of 200 μg/ml.

Synthesis, Crystal Structure, Hirshfeld Surface, Energy Frame Work and DFT Analysis of Ethyl-4-aminobenzoate Oxalate Monohydrate Salt

Using the single crystal X-ray diffraction method, the title molecule ethyl-4-aminobenzoate oxalate monohydrate has been synthesized, crystallized and characterized. The Hirshfeld surfaces computational approach was used to analyze the intermolecular interactions in the crystal structure. The aforementioned compound crystallizes in a monoclinic crystal system of space group P21/c with the following cell parameters: a = 15.475(3), b = 5.7117(9), c = 14.029(3), = 101.764(6)º, V = 1214.0(4) 3 and Z = 4. The molecules in the crystal structure are connected by the N1-H1C···O7, O5-H2···O3, O7-H1···O4 and C8-H8A···Cg type intermolecular interaction, where Cg is the centroid of the ring. For the title molecule, the inter contact O···H (48.4%) contributes more to the Hirshfeld surfaces. The proton transfer from oxalic acid’s phenolic group to ethyl-4-aminobenzoate’s amine group, which results in the creation of salt, is revealed by the crystal structure. The ground state of ethyl-4-aminobenzoate oxalate monohydrate was also studied theoretically using the density functional method (DFT/B3LYP) with a basis set of 6–311++G(d,p). Charge transfer happens within the molecule, as shown by the computed HOMO and LUMO energies, DOS and MESP, as well as by the optimized molecular structure, electronic structural analysis and UV spectrum analysis.

Study of crystal structure and optical features of single-phase Ba2BiV3O11: Dy3+ nanophosphors for advanced solid-state illuminating applications

Urea-aided solution combustion (SC) method has been employed to generate monoclinic structure-based Dy (III) doped Ba2BiV3O11 nanophosphors. X-ray diffraction (XRD) and the Rietveld refinement techniques confirmed that the developed nanophosphors are crystallized in a monoclinic crystal system with space group as P21/a. The crystallite size was assessed via Scherrer's equation and Williamson-Hall (W–H) plot. SEM and TEM images confirm the agglomerated particle with a non-uniform shape lies in the nano range. An energy dispersive X-ray (EDAX) study is executed to assess various constitute elements and their relative dispersal was analyzed via mapping spectrum. The highly intense emission peak at 577 nm is ascribed to 4F9/2→6H13/2 electronic transition of the Dy3+ ion when energized at 327 nm wavelength. The band gap values for the host matrix and the optimized sample were measured using a DR spectrophotometer. Auzel's model was utilized to establish the values of quantum efficiency (68.21 %), non-radiative rates (597.08 s−1), and intrinsic lifetime (0.7803 ms). Furthermore, PL (photoluminescence) data is exercised to attain chromatic quantities viz. color coordinates (x and y), and correlated color temperature (CCT), which are strongly endorsed for their usage as near UV-based advanced solid-state illuminating devices.

Further Insight into the Manganese(II) 2,2′-Bipyridine-1,1′-dioxide Homoleptic Complex: Single-Crystal X-ray Structure Determination of the Perchlorate Salt and DFT Calculations

The homoleptic cationic complex formed by reacting suitable manganese(II) salts with 2,2′-bipyridine-1,1′-dioxide (bipyO2) has been subjected to several studies in the past because of its peculiar absorption and electrochemical features. Here, the first single-crystal X-ray structure determination of a [Mn(bipyO2)3]2+ salt is reported, where the charge of the cation is balanced by perchlorate anions. The hydrated salt [Mn(bipyO2)3](ClO4)2 crystallizes in the monoclinic system (P21/n space group) and the asymmetric unit contains three cationic complexes and six perchlorate anions. The environment of the manganese(II) ions is best described as octahedral, with scarce variations among the three cations in the asymmetric unit. The bipyO2 ligands exhibit κ2 coordination mode, forming seven-membered metallacycles. The X-ray outcomes have been used as the starting point for DFT and TDDFT calculations, aimed to elucidate the charge transfer origin of the noticeable absorption in the visible range. The MLCT nature is confirmed by the hole and electron distributions associated with the spin-allowed transitions. DFT calculations on the related manganese(III) complex indicate that the geometry of [Mn(bipyO2)3]2+ changes only slightly upon oxidation, in agreement with the reversible electrochemical behaviour experimentally observed.

Photoluminescence properties of Pr-doped LaAsO4: An experimental and theoretical study employing density functional theory

Praseodymium doped lanthanum arsenate, denoted as La1-xPrxAsO4, has been synthesized with different concentrations of the dopant (x = 0.5 %; 1 %; 2 %; 3 % and 5 %) via the combustion method and their optoelectronic properties have been investigated. A study of the crystalline structure and size of the compound by XRD confirms that both the pristine LaAsO4 and Pr-doped LaAsO4 are pure and maintain a monoclinic crystal structure, with the crystalline size ranging from 60 to 76 nm. The morphological study of the nanoparticles by SEM analysis reveals that all samples, regardless of the concentration of Pr3+, consist of homogeneously packed and irregularly shaped small particles. The optical studies by absorption and fluorescence spectroscopies highlight the unique optoelectronic characteristics of La1-xPrxAsO4, with absorption predominantly in the UV and blue regions and prominent emission peaks in the visible spectrum, most notably at 610 nm. The optimal luminescence is observed at a 0.5 % Pr3+ doping level, deviating from typical trends as higher concentrations lead to diminished emission intensity and lifetime due to concentration quenching effects. The application of Density Functional Theory (DFT) with GGA + PBE and GGA + PBE + U approximations has effectively elucidated the electronic structure and optical properties of the Pr-doped LaAsO4. The incorporation of Pr's 4f states within the LaAsO4 forbidden band significantly alters the material's electronic landscape, notably reducing the optical band gap from 4.45 eV to 2.299 eV. This modification in the band structure aligns favourably with the dielectric function curves and density of states analyses, corroborating the observed visible light emission in the doped samples.