Search Results (102)

Silicon–lithium clusters are promising candidates for hydrogen storage due to their lightweight composition, high gravimetric capacities, and favorable non-covalent binding characteristics. In this study, we employ density functional theory (DFT), global optimization (AUTOMATON and Kick–MEP), and Born–Oppenheimer molecular dynamics (BOMD) simulations to evaluate the structural stability and hydrogen storage performance of key Li–Si systems. The exploration of their potential energy surface (PES) reveals that the true global minima of Li₆Si₆ and Li₁₀Si₁₀ differ markedly from those of the earlier Si–Li structures proposed as structural analogs of aromatic hydrocarbons such as benzene and naphthalene. Instead, these clusters adopt compact geometries composed of one or two Si₄ (T_d) units and a Si₂ dimer, all stabilized by surrounding Li atoms. Motivated by the recurrence of the Si₄–T_d motif, we explore oligomers of Li₄Si₄, which can be viewed as electronically transmuted analogues of P₄, confirming the additive H₂ uptake across dimer, trimer, and tetramer assemblies. Within the series of Si–Li clusters evaluated, the Li₁₂Si₅ sandwich complex, featuring a σ-aromatic Si₅¹⁰⁻ ring encapsulated by two Li₆⁵⁺ moieties, achieves the highest hydrogen capacity, adsorbing 34 H₂ molecules with a gravimetric density of 23.45 wt%. Its enhanced performance arises from the high density of accessible Li⁺ adsorption sites and the electronic stabilization afforded by delocalized σ-bonding. BOMD simulations at 300 and 400 K confirm their dynamic stability and reversible storage behavior, while analysis of the interaction regions confirms that hydrogen adsorption proceeds via weak, dispersion-driven physisorption. These findings clarify the structure–property relationships in Si–Li clusters and provide a basis for designing modular, lightweight, and thermally stable hydrogen storage materials. Full article

This study aims to apply standard statistics and InterCriteria analysis (ICrA) for assessing the effects of different transcranial magnetic stimulation (TMS) intensities and three muscle conditions on the evoked responses of the first dorsal interosseous muscle (FDIM). Surface electromyograms from the right FDIM of ten right-handed healthy volunteers were recorded, and amplitudes of motor evoked potentials (MEPs), latencies of MEPs, and silent periods were obtained. ICrA was used for the first time as a supplementary tool along with the applied statistical methods. Three case studies were processed by the ICrA approach for a wide examination of neuromuscular excitability in humans. As a result, the relations between increasing TMS intensities, MEP amplitudes, MEP latencies, and silent periods were established at relaxed muscle condition, isometric index finger abduction condition, and co-contraction of antagonist muscles condition. Also, the dependencies between MEP amplitudes, MEP latencies, and silent periods themselves, and for different TMS intensities, were outlined. The results confirmed relations known from the literature and showed new ones. Full article

Two new Co(II) coordination compounds viz. [Co(H₂O)(bz)₂(μ-3-Ampy)₂]_n (1) and [Co(4-Mebz)₂(2-Ampy)₂] (2) (wherebz = benzoate, 4-Mebz = 4-Methylbenzoate and Ampy = Aminopyridine) were synthesized and characterized via elemental (CHN), electronic spectroscopy, FT-IR spectroscopy, and thermogravimetric analysis (TGA). The molecular structures were determined by single-crystal X-ray diffraction analysis, inferring that compound 1 crystallizes as a 3-Ampy bridged Co(II) coordination polymer, whereas compound 2 crystallizes as a mononuclear Co(II) compound. Compound 1 unfolds the presence of N–H⋯O, C–H⋯O, O–H⋯O, C–H⋯N and aromatic π⋯π interactions, while for compound 2, N–H⋯O, C–H⋯O, C–H⋯C and C–H⋯π interactions are observed. Both the compounds showcase scarcely reported chelate ring interactions involving the benzoate moiety (chelate ring⋯π in 1 and N–H⋯chelate ring in 2). We also conducted theoretical evaluations comprising of combined QTAIM/NCI plot analysis, DFT energy calculation and MEP surface analysis to analyze the supramolecular interactions present in the crystal structures. As per QTAIM parameters, the predominance of π-stacking interactions over hydrogen bonds in stabilizing the assembly in compound 1 is affirmed. Likewise, in compound 2, both hydrogen bonding (HBs) and C–H⋯π interactions are deemed pivotal in stabilizing the dimeric assemblies. The in vitro antiproliferative activities of compounds 1 and 2 were performed against Dalton’s lymphoma (DL) cancer cell lines through cytotoxicity and apoptosis assays, showcasing higher cytotoxicity of compound 1 (IC₅₀ = 28 μM) over compound 2 (IC₅₀ = 34 μM). Additionally, a molecular docking study investigated the structure–activity relationship of these compounds and allowed an understanding of the molecular behaviour after treatment. Full article

Background: Monobond Etch & Prime (MEP; Ivoclar) has a material-dependent effect on dental ceramics. This study evaluated the impact of MEP application time on the resin–ceramic shear bond strength (SBS) of lithium disilicate (LD) and advanced lithium disilicate (ALD) ceramics. Methods: LD and ALD discs were distributed into four groups (n = 20): no surface treatment; 5% HF etching followed by the application of a silane-containing primer (S); MEP applied for 40 s and maintained for 20 s; MEP applied for 2 min and maintained for 40 s. Resin–ceramic SBS was evaluated at 24 h and after thermocycling. The statistical analysis of SBS was performed by using the three-way ANOVA and Tukey’s multiple comparisons tests. Additional ceramic samples were prepared to assess the surface topography. Results: There was no statistically significant difference in the SBS of the MEP groups (20 s and 2 min) and HF + S. However, only the HF + S and MEP (2 min) groups showed durable adhesion after thermocycling. MEP resulted in less distinct surface alterations compared with HF etching. Conclusion: Increasing the application time of MEP to 2 min resulted in more durable resin–ceramic adhesion compared with the application time (40 s) recommended by the manufacturer. The adhesion of resin–ceramic to LD and ALD did not significantly differ. Full article

Background: This study aimed to analyze the impact of seated, 45° inclined, and supine positions on respiratory muscle strength (Maximal Inspiratory Pressure—MIP, Maximal Expiratory Pressure—MEP, Sniff Nasal Inspiratory Pressure—SNIP and Sniff Nasal Expiratory Pressure—SNEP) and the electrical activity of respiratory muscles in healthy adults. Ten healthy subjects were evaluated. Methods: Personal, anthropometric data (weight, height, BMI) and lung function (spirometry) were collected, followed by random assessments of inspiratory (MIP, SNIP) and expiratory (MEP, SNEP) muscle strength. Respiratory muscle strength maneuvers and surface electromyographic (sEMG) activity were assessed in sitting, 45° inclined, and supine positions. Results: present that MIP was statistically higher in the sitting position compared to the supine position (p < 0.05) and the 45° supine position (p < 0.05), with SNIP: p < 0.05 and SNEP: p < 0.05 as well. Intercostal muscle activity was higher during MIP, MEP, and SNEP maneuvers in the sitting position (p < 0.05). Additionally, rectus abdominis muscle activity was higher in this position during MIP and SNEP maneuvers. Conclusions: The results suggest there are significant differences in inspiratory pressures between positions, with the difference in activity muscle pattern. In conclusion, body position affected maximal respiratory pressures and influences EMG activation of specific respiratory muscles during MIP. Full article

In the present work, we reported the synthesis and characterization [single crystal X-ray diffraction technique, spectroscopic, etc.] of two new Ni(II) and Zn(II) coordination compounds, viz. [Ni(2,6-PDC)₂]₂[Ni(en)₂(H₂O)₂]₂[Ni(en)(H₂O)₄]·4H₂O (1) and [Zn(2,6-PDC)(Hdmpz)₂] (2) (where 2,6-PDC = 2,6-pyridinedicarboxylate, en = ethylene-1,2-diamine, and Hdmpz = 3,5-dimethyl pyrazole). Compound 1 is found to crystallize as a multicomponent Ni(II) compound with five discrete complex moieties, whereas compound 2 is isolated as a mononuclear Zn(II) compound. A deep analysis of the crystal structure of 1 unfolds unusual dual enclathration of guest complex cationic moieties within the supramolecular host cavity stabilized by anion–π, π-stacking, N–H⋯O, C–H⋯O, and O–H⋯O hydrogen bonding interactions. Again, the crystal structure of compound 2 is stabilized by the presence of unconventional C–H⋯π(chelate ring) interactions along with C–H⋯O, C–H⋯N hydrogen bonding, π-stacking, and C–H⋯π(pyridyl) interactions. These non-covalent interactions were further studied theoretically using density functional theory (DFT) calculations, molecular electrostatic potential (MEP) surfaces, non-covalent interaction (NCI) plot index, and quantum theory of atoms in molecules (QTAIM) computational tools. The computational study displays that π-stacking or H bonds greatly tune the directionality of compound 1, although non-directional electrostatic forces dominate energetically. For compound 2, a combined QTAIM/NCI plot analysis confirms the presence of unconventional C–H⋯π(chelate ring) interactions along with other weak interactions obtained from the crystal structure analysis. Further, the individual energy contributions of these weak yet significant non-covalent interactions have also been determined computationally. Full article

Phycocyanin (PC) is a naturally occurring green pigment in Spirulina. It was extracted by ultrasonic extraction using green technology, and its structure was studied using IR- and NMR-spectroscopy. Spectral data confirmed the PC structure. This study also involves an in silico assessment of the diverse applications of green pigment PC. Utilizing QSAR, PreADME/T, SwissADME, and Pro-Tox, this study explores the safety profile, pharmacokinetics, and potential targets of PC. QSAR analysis reveals a favorable safety profile, with the parent structure and most metabolites showing no binding to DNA or proteins. PreADME/T indicates low skin permeability, excellent intestinal absorption, and medium permeability, supporting oral administration. Distribution analysis suggests moderate plasma protein binding and cautious blood–brain barrier permeability, guiding formulation strategies. Metabolism assessments highlight interactions with key cytochrome P450 enzymes, influencing drug interactions. Target prediction analysis unveils potential targets, suggesting diverse therapeutic effects, including cardiovascular benefits, anti-inflammatory activities, neuroprotection, and immune modulation. Based on the in silico analysis, PC holds promise for various applications due to its safety, bioavailability, and potential therapeutic benefits. Experimental validation is crucial to elucidate precise molecular mechanisms, ensuring safe and effective utilization in therapeutic and dietary contexts. DFT calculations, including geometry optimization, MEP analysis, HOMO-LUMO energy surface, and quantum reactivity parameters of the PC compound, were obtained using the B3LYP/6–311G(d,p) level. This integrated approach contributes to a comprehensive understanding of PC’s pharmacological profile and informs future research directions. Full article

An Fe(III)-carbonato six-coordinate picket fence porphyrin complex with the formula [K(2,2,2-crypt)][Fe^III(TpivPP)(CO₃)]·C₆H₅Cl·3H₂O (I) has been synthesized and characterized by UV-Vis and FT-IR spectra. The structure of (carbonato)(α,α,α,α-tetrakis(o-pivalamidophenyl)porphinato)ferrate(III) was also established by XRD. The iron atom is hexa-coordinated by the four nitrogen atoms of the pyrrol rings and the two oxygen atoms of the CO₃²⁻ group. Complex I, characterized as a ferric high-spin complex (S = 5/2), presented higher Fe-Np (2.105(6) Å) and Fe-P_C (0.654(2) Å) distances. Both X-ray molecular structure and Hirshfeld surface analysis results show that the crystal packing of I is made by C-H⋯O and C-H⋯Cg weak intermolecular hydrogen interactions involving neighboring [Fe^III(TpivPP)(CO₃)]⁻ ion complexes. Computational studies were carried out at DFT/B3LYP-D3/LanL2DZ to investigate the HOMO and LUMO molecular frontier orbitals and the reactivity within the studied compound. The stability of compound I was investigated by analyzing both intra- and inter-molecular interactions using the 2D and 3DHirshfeld surface (HS) analyses. Additionally, the frontier molecular orbital (FMO) calculations and the molecular electronic potential (MEP) analyses were conducted to determine the electron localizations, electrophilic, and nucleophilic regions, as well as charge transfer (ECT) within the studied system. Full article

The advancement of traditional sample preparation techniques has brought about miniaturization systems designed to scale down conventional methods and advocate for environmentally friendly analytical approaches. Although often referred to as green analytical strategies, the effectiveness of these methods is intricately linked to the properties of the sorbent utilized. Moreover, to fully embrace implementing these methods, it is crucial to innovate and develop new sorbent or solid phases that enhance the adaptability of miniaturized techniques across various matrices and analytes. Graphene-based materials exhibit remarkable versatility and modification potential, making them ideal sorbents for miniaturized strategies due to their high surface area and functional groups. Their notable adsorption capability and alignment with green synthesis approaches, such as bio-based graphene materials, enable the use of less sorbent and the creation of biodegradable materials, enhancing their eco-friendly aspects towards green analytical practices. Therefore, this study provides an overview of different types of hybrid graphene-based materials as well as their applications in crucial miniaturized techniques, focusing on offline methodologies such as stir bar sorptive extraction (SBSE), microextraction by packed sorbent (MEPS), pipette-tip solid-phase extraction (PT-SPE), disposable pipette extraction (DPX), dispersive micro-solid-phase extraction (d-µ-SPE), and magnetic solid-phase extraction (MSPE). Full article

This study aimed to address the issue of the low solubility in the model drug probenecid (PRO) and its impact on bioavailability. Two salts of probenecid (PRO), 4-aminopyridine (4AMP), and 4-dimethylaminopyridine (4DAP) were synthesized and characterized by PXRD, DSC, TGA, FTIR, and SEM. The crystal structures of the two salts were determined by SCXRD, demonstrating that the two salts exhibited different hydrogen bond networks, stacking modes, and molecular conformations of PRO. The solubility of PRO and its salts in a phosphate-buffered solution (pH = 6.8) at 37 °C was determined, the results showed that the solubility of PRO salts increased to 142.83 and 7.75 times of the raw drug, respectively. Accelerated stability experiments (40 °C, 75% RH) showed that the salts had good phase stability over 8 weeks. Subsequently, Hirshfeld surface (HS), atom in molecules (AIM), and independent gradient model (IGM) were employed for the assessment of intermolecular interactions. The analyses of salt-forming sites and principles were conducted using molecular electrostatic potential surfaces (MEPs) and pK_a rules. The lattice energy (E_L) and hydration-free energy (E_HF) of PRO and its salts were calculated, and the relationships between these parameters and melting points and the solubility changes were analyzed. Full article

This investigation presents results on the improvement of the corrosion-protective effect of consecutive sealing treatments of anodized Al 1050 (Al_Anod). The treatments were performed in cerium-containing and mixed NaH₂PO₄ + Ca(NO₃)₂ solutions. The changes of the surface morphology, structure and chemical composition, chemical state of the elements, and basic corrosion parameters of the studied systems were investigated by SEM, EDXS, XRD, XPS, and a complex of electrochemical techniques (PDP, E_OCP vs. timeplot, chronoamperometric transients, Rp and CR at E_OCP, etc.). The results obtained show that the basic components of the obtained sealing conversion layers (before and after exposure to model Cl⁻-containing corrosion media) are characterized by Ca₁₀(PO₄)₆(OH)₂, AlO(OH), CePO₄, and CeAlO₃ (after the corrosion tests, they are converted to insoluble Me-PO₃ and Me-P₄O₁₀). We conclude that the observed decrease in the corrosion rate of Al and the corresponding increase in the polarization resistance are accomplished by the two-step sealing treatment, which fills up the Al_Anod pores with insoluble deposits. Full article

We report the synthesis of two novel halogenated nitro-arylhimachalene derivatives: 2-bromo-3,5,5,9-tetramethyl-1-nitro-6,7,8,9-tetrahydro-5H-benzo[7]annulene (bromo-nitro-arylhimachalene) and 2-chloro-3,5,5,9-tetramethyl-1,4-dinitro-6,7,8,9-tetrahydro-5H-benzo[7]annulene (chloro-dinitro-arylhimachalene). These compounds were derived from arylhimachalene, an important sesquiterpene component of Atlas cedar essential oil, via a two-step halogenation and nitration process. Characterization was performed using ¹H and ¹³C NMR spectrometry, complemented by X-ray structural analysis. Quantum chemical calculations employing density functional theory (DFT) with the Becke3-Lee-Yang-parr (B3LYP) functional and a 6-31++G(d,p) basis set were conducted. The optimized geometries of the synthesized compounds were consistent with X-ray structure data. Frontier molecular orbitals and molecular electrostatic potential (MEP) profiles were identified and discussed. DFT reactivity indices provided insights into the compounds’ behaviors. Moreover, Hirshfeld surface and 2D fingerprint analyses revealed significant intermolecular interactions within the crystal structures, predominantly H–H and H–O contacts. Molecular docking studies demonstrate strong binding affinities of the synthesized compounds to the active site of protein 7B2W, suggesting potential therapeutic applications against various isolated smooth muscles and neurotransmitters. Full article

Two new Mn(II) and Zn(II) metal–organic compounds of 1,10-phenanthroline and methyl benzoates viz. [Mn(phen)₂Cl₂]2-ClBzH (1) and [Zn(4-MeBz)₂(2-AmPy)₂] (2) (where 4-MeBz = 4-methylbenzoate, 2-AmPy = 2-aminopyridine, phen = 1,10-phenanthroline, 2-ClBzH = 2-chlorobenzoic acid) were synthesized and characterized using elemental analysis, TGA, spectroscopic (FTIR, electronic) and single crystal X-ray diffraction techniques. The crystal structure analysis of the compounds revealed the presence of various non-covalent interactions, which provides stability to the crystal structures. The crystal structure analysis of compound 1 revealed the formation of a supramolecular dimer of 2-ClBzH enclathrate within the hexameric host cavity formed by the neighboring monomeric units. Compound 2 is a mononuclear compound of Zn(II) where flexible binding topologies of 4-CH₃Bz are observed with the metal center. Moreover, various non-covalent interactions, such as lp(O)-π, lp(Cl)-π, C–H∙∙∙Cl, π-stacking interactions as well as N–H∙∙∙O, C–H∙∙∙O and C–H∙∙∙π hydrogen bonding interactions, are found to be involved in plateauing the molecular self-association of the compounds. The remarkable enclathration of the H-bonded 2-ClBzH dimer into a supramolecular cavity formed by two [Mn(phen)₂Cl₂] complexes were further studied theoretically using density functional theory (DFT) calculations, the non-covalent interaction (NCI) plot index and quantum theory of atoms in molecules (QTAIM) computational tools. Synergistic effects were also analyzed using molecular electrostatic potential (MEP) surface analysis. Full article

The evaluation of patients after the surgical correction of idiopathic scoliosis in a long-term follow-up with clinical neurophysiological methods has not been presented in detail. This study aimed to compare the results of neurophysiological studies in 45 girls with scoliosis of Lenke types 1–3 performed pre- (T0) and postoperatively, 1 week after surgery (T1) and 6 months after surgery (T2). The parameter values of the surface electromyography while attempting maximal contraction (mcsEMG) and the transcranial motor-evoked potentials (MEPs) recorded in the anterior tibial muscles, as well as the electroneurography (ENG) of the peripheral transmission in the peroneal nerve motor fibers, were compared. The results indicate that efferent neural conduction function both centrally and peripherally, and TA muscle function slightly improved immediately after the surgical correction of scoliosis, and further normalization appeared after six months in the long-term follow-up (at p = 0.03). The sEMG recordings indicate that half a year after surgical treatment in IS patients, the TA muscle motor unit recruitment function, as well as the muscle strength evaluated with Lovett’s scale, was comparable to the normal condition. The ENG recording results indicated a gradual reduction in the motor fiber injury symptoms, mainly of the axonal type, in the peroneal nerves. The surgeries also improved the lumbar ventral roots’ neural transmission to a normal functional status. The MEP amplitude parameter values recorded after the surgical scoliosis corrections in T1 indicated a slight improvement in the efferent transmission of neural impulses within the fibers of the spinal tracts; in the long-term T2 observation period, they reached values comparable to those recorded in healthy volunteers, bilaterally. Preoperatively (T0), the results of all the neurophysiological study parameters in the IS patients were asymmetrical at p = 0.036–0.05 and recorded as worse on the concave side, suggesting the lateralization of neurological motor deficits. One week postoperatively (T1), this asymmetry was recorded as gradually reduced, showing almost no difference between the right and left sides six months later (T2). The presented algorithm for the neurophysiological assessments performed in the pre-, intra-, and long-term postoperative periods using the mcsEMG, MEP, and ENG neurophysiological examinations, together with the clinical studies, may help in the comprehensive functional evaluation of the spinal cord tracts and ventral root neural conduction, which allows the detection of the subclinical neurological changes related to scoliosis itself and the consequences of the corrective surgery. Such an evaluation can also be significant in making final decisions regarding IS surgeries and their personalization after attempting conservative treatments with bracing and kinesiotherapy. Neurophysiological studies, as a sensitive biomarker, allowed us to predict and ascertain the final result of IS treatment in the long-term follow-up, which showed the health status of patients as being comparable to that of healthy volunteers. Full article

The reaction between 5-acetylbarbituric acid and 4-dimethylthiosemicarbazide or 4-hexamethyleneiminyl thiosemicarbazide produces 5-acetylbarbituric-4-dimethylthiosemicarbazone (H₂AcbDM) and 5-acetylbarbituric-4N-hexamethyleneiminyl thiosemicarbazone (H₂Acbhexim). Eight new complexes with different copper(II) salts have been prepared and characterized using elemental analysis, molar conductance, UV–Vis, ESI-HRMS, FT-IR, magnetic moment, EPR, and cyclic voltammetry. In addition, three-dimensional molecular structures of [Cu(HAcbDM)(H₂O)₂](NO₃)·H₂O (3a), [Cu(HAcbDM)(H₂O)₂]ClO₄ (4), and [Cu(HAcbHexim)Cl] (6) were determined by single crystal X-ray crystallography, and an analysis of their supramolecular structure was carried out. The H-bonded assemblies were further studied energetically using DFT calculations and MEP surface and QTAIM analyses. In these complexes, the thiosemicarbazone coordinates to the metal ion in an ONS-tridentate manner, in the O-enolate/S-thione form. The electrochemical behavior of the thiosemicarbazones and their copper(II) complexes has been investigated at room temperature using the cyclic voltammetry technique in DMFA. The Cu(II)/Cu(I) redox system was found to be consistent with the quasi-reversible diffusion-controlled process. Full article