A series of MN6-type energetic complexes with triazole/tetrazole ligands was designed using density functional theory. We aimed to elucidate the spin-crossover (SCO) behavior and establish a quantitative structure-property relationship for spin-controlled sensitivity regulation. The complexes with d5–d7 configurations were identified as promising SCO candidates, showing characteristic volume changes of 1.8–5.3%. Numerical fitting reveals that SCO correlates with a normalized bond-length change. A universal linear scaling law was established as ΔH/ΔV = −24 + 56·XΔd/d, defining a quantitative SCO criterion of −24 < ΔH/ΔV < 32 kJ·mol−1 per 100% volume change. This work has demonstrated that spin-controlled stability offers a precise strategy for tuning energetic performance, enabling the design of high-energy, low-sensitivity materials.
In this study, NMR spectroscopy was used to investigate the temperature dependences of paramagnetic chemical shifts in a 22% solution of poloxamer 407 with and without the addition of the [Dy(DTPA)]2− complex. The half-width of the polymer signals in the system with the paramagnetic additive depends significantly on the solution viscosity and temperature due to the Curie-spin contribution to the paramagnetic spin-spin relaxation rate enhancement. The [Dy(DTPA)]2−complex can be considered as a promising compound for the design of temperature-sensitive NMR probes aimed at determining local temperature and viscosity in aqueous media and dispersed systems.
The rational design of transition-metal sensitizers remains a critical challenge in advancing dye-sensitized solar cell (DSSC) technologies beyond noble-metal systems. A series of cobalt-based complexes, CoISO(Diaquabis(4-pyridinecarboxylato-κN)(acetato-κO)cobalt(III)), CoPICO (Diaquabis(pyridine-2-carboxylato-κ2N,O)(acetato-κO)Cobalt(III)), CoIL3 (Bis(pyridine-4-yl-3-nitrobenzoate)cobalt(III) diacetate) and CoIL4 (Bis(pyridine-4-yl-4-nitrobenzoate)cobalt(III)diacetate), were synthesized and systematically evaluated as sensitizers in dye-sensitized solar cells (DSSCs) to establish a detailed structure–activity relationship (SAR) linking coordination chemistry to photovoltaic performance. The ligands IL3 (pyridine-4-ylmethyl-3-nitrobenzoate) and IL4 (pyridine-4-ylmethyl-4-nitrobenzoate), differing only by nitro substituent position (meta vs para), were synthesized and subsequently coordinated to cobalt acetate to obtain high-purity complexes (yields: CoISO 87.5%, CoPICO 42.4%, CoIL3 84%, CoIL4 92%). Spectroscopic analysis confirmed octahedral coordination environments with characteristic CoN (425–574 cm−1) and CoO (526 cm−1) vibrations. UV–Vis spectra revealed d–d transitions at 538–564 nm corresponding to optical energies of 2.20–2.47 eV. Magnetic susceptibility measurements distinguished intermediate-spin CoISO (μeff = 2.14 BM) and CoIL3 (2.90 BM) from high-spin CoPICO (5.45 BM) and CoIL4 (5.92 BM). Voltammetry over 5–200 mV s−1 resolved a quasi-reversible Co(III)/Co(II) couple with ΔEp = 50.7, 67.1 and 78.6 mV at 5 mV s−1 for CoPICO, CoIL4 and CoIL3 respectively, close to the 59 mV Nernstian value for a one-electron process, together with a second, higher-potential process lying beyond the +0.4 V limit of the window. ΔEp widened with scan rate and Nicholson analysis gave k0/√D = 1.9–5.2 s−1/2. CoISO does not behave as a single couple: its cathodic feature lies positive of its anodic one. Impedance spectra were capacitive, with near-vertical Nyquist responses and no charge-transfer semicircle; the low-frequency impedance rose in the order CoPICO (20 Ω) < CoIL3 (21 Ω) < CoIL4 (29 Ω) < CoISO (52 Ω). A 50 W/cm2 LED illumination demonstrated pronounced performance variation. CoIL3 delivered the highest power conversion efficiency (η = 0.0403) with Jsc = 0.342 A cm−2, Voc = 0.917 V and Pmax = 0.020 W cm−2. CoPICO showed the highest Voc of 1.050 V but moderate efficiency (η = 0.0115). CoISO exhibited an exceptionally high fill factor of 81.05% but very low Jsc of 0.006 A cm−2, limiting η to 0.0096. CoIL4 showed the lowest efficiency (η = 0.0070), attributed to steric and electronic decoupling effects. All complexes displayed large injection driving forces (ΔEinj > 1.5 eV), indicating that regeneration kinetics and interfacial recombination and not electron injection govern overall device performance.
An iron(III) porphyrin immobilized on zinc hydroxide nitrate (ZHN–FeP) was developed as a bifunctional solid for heterogeneous catalysis of styrene epoxidation, CO₂ cycloaddition to epoxides, and one-pot sequential oxidation/carbonation tandem process. The hybrid combines the oxidative activity of the iron porphyrin center with the Lewis acidic sites of the layered hydroxide salt support, enabling cooperative catalysis in both individual and integrated transformations. In styrene oxidation, ZHN–FeP afforded up to 94.2% styrene oxide yield under optimized conditions. In the CO₂ cycloaddition reaction, the hybrid catalyst reached 98.5% conversion to styrene carbonate under 2 bar CO₂, while the individual ZHN and FeP components gave lower conversions. The free FeP also displayed high catalytic efficiency in CO₂ fixation, with TON (turnover number) and TOF (turnover frequency) values of 195,440 and 8143 h−1, respectively. In the one-pot sequential reaction, ZHN–FeP afforded 35% styrene carbonate yield, confirming the feasibility of coupling oxidation and CO₂ valorization in a single catalytic system. These results highlight the potential of ZHN-supported metalloporphyrins as multifunctional catalysts for sustainable CO₂ utilization.
Nickelalactone complexes, intermediates from the reductive coupling of CO2 and alkenes, supported by diphosphine (dppe = ethylenebis(diphenylphosphine) and dtbpe = ethylenebis(ditert-butylphosphine)) or bipyridine (bpy = 2,2′-bipyridine, dmbpy = 4,4′-dimethyl-2,2′-bipyridine, and dtbbpy = 4,4′-bis(tert-butyl)-2,2′-bipyridine) ligands were evaluated for their electrochemical behavior as postulated intermediates on-route to electrochemical carboxylated products. The synthesis and characterization of two new nickelalactones, 4 ((dmbpy)Ni(C2H4COO)) and 5 ((dtbbpy)Ni(C2H4COO)), are reported including 1H NMR spectra and single-crystal X-ray diffraction data. Cyclic voltammetry experiments of the diphosphine complexes, 1 ((dppe)Ni(C2H4COO)) and 2 ((dtbpe)Ni(C2H4COO)), in acetonitrile scanning cathodically showed an irreversible reduction event associated with loss of the lactone fragment and formation of bis(diphosphino)nickel(0). In contrast, bipyridine supported complexes, 3 ((bpy)Ni(C2H4COO)), 4 and 5, showed a quasi-reversible feature followed by an irreversible reduction event upon scanning cathodically, associated with bipyridine reduction and loss of lactone fragment respectively. For all complexes explored, the irreversible feature associated with formal reduction to nickel(0) is near (ΔEp ≤ 200 mV) the potential of direct reduction of carbon dioxide to CO2•– (−2.68 V vs. (C5H5)2Fe+/0), indicating that under electrochemical conditions nickelalactone reduction is unfavorable. Controlled potential electrolysis (CPE) and spectroelectrochemical vibrational spectroscopy (SEC-FTIR) experiments identified acrylate and propionate as the carboxylate products following nickelalactone reduction. These results highlight that under the operating potentials of electrochemical carboxylation systems, multiple competing species are likely present as opposed to one discrete metallalactone intermediate, providing important considerations for the design of transition metal complexes for electrochemical carboxylation to form carboxylic acids.
We report seven new copper(II) complexes with perfluorinated carboxylates and quinoline as ligands. Single crystal X-ray diffraction, infrared spectroscopy (IR), electron impact (EI) mass spectrometry, electron paramagnetic resonance spectroscopy (EPR), magnetic susceptibility, and elemental analysis were used to confirm the composition and structure of the studied compounds. Research has revealed that mononuclear (quinH)2[Cu(O2CC6F13)4], [Cu(O2CR)2(quin)2], where R = C3F7, C5F11, C6F13, dinuclear [Cu2(quin)2(μ-O2CC6F13)4], and tetranuclear (quinH)2[Cu4(μ3-OH)2(O2CC5F11)4(quin)2(μ-O2CC5F11)4], [Cu4(μ3-OH)2(O2CC3F7)2(quin)4(μ-O2CC3F7)4] structures are formed in such system. For [Cu(O2CC6F13)2(quin)2] at 100 K, the rarely observed modulated phase was identified, and its structure was also determined. Magnetic studies for complexes of the general formula [Cu(O2CRF)2(quin)2] have shown that all three compounds present similar behaviour.
Triangular planar and tetragonal boron-containing compounds play a vital role in various biological processes due to their distinct molecular structures and unique electronic properties. In this study, the synthesis and structural characterization of a series of triangular planar (LB1–4) and tetragonal (LBN1–4) boron-luteolin conjugate compounds were performed as potential therapeutic agents. Subsequently, AChE inhibition, antibacterial activity against carbapenem-resistant strains Acinetobacter baumannii (A. baumannii), Escherichia coli (E. coli), and Klebsiella pneumoniae (K. pneumoniae), and MRSA, evaluation of methicillin-resistant Staphylococcus aureus MRSA biofilm disruption, docking, and gene expression studies of these boron compounds were carried out. Structural characterization of bioactive triangular planar/tetragonal boron-luteolin conjugate compounds was performed using NMR (1H, 13C, and 11B) spectra, 19F NMR for (LB1) and (LBN1), FT-IR spectra, UV–Vis spectra, Fluorescence spectra, LC-MS/MS spectrometry, elemental analysis, and melting point analysis techniques. Among the synthesized compounds, (LB4) exhibited notable antibacterial activity against carbapenem-resistant strains, with MIC values of 32, 256, and 32 μg/mL against A. baumannii, E. coli, and K. pneumoniae, respectively, while a markedly stronger activity was observed against MRSA (MIC = 4 μg/mL). The strongest antioxidant activity was recorded for (LB1), with an IC₅₀ value of 8.07 ± 0.354 μg/mL. Regarding AChE inhibitory activity, (LBN3) demonstrated the highest potency, exhibiting an IC₅₀ value of 46.189 ± 0.348 μg/mL. Furthermore, (LB4) effectively inhibited MRSA biofilm formation, achieving a biofilm inhibition rate of 54.9 ± 0.7% at 1 × MIC. Gene expression analysis revealed that (LB4) significantly downregulated the expression of mepA, sarA, icaA, and dtlB. In addition, molecular docking studies showed that (LB4) displayed favorable binding affinities toward the 2X3F protein target, with docking scores of −7.053 kcal/mol.
Surface engineering of silicon has developed as effective strategy for improving light harvesting in photovoltaic materials. In this work, porous silicon (p-Si) was fabricated on p-type Si (111) substrates through chemical etching process via thermal evaporation of selenium (Se) and selenium/germanium (SeGe) thin films to enhance its optical properties. The structural, vibrational, morphological, and optical properties were characterized using XRD, Raman, SEM and UV–Visible absorption spectroscopy. XRD analysis confirmed that the crystalline Si framework was preserved after chemical etching, while additional diffraction peaks verified the deposition of Se and SeGe layers. Raman spectra revealed the c-Si transverse optical phonon mode together with Se-related vibrational modes, indicating the formation of stable semiconductor heterostructures. SEM observations demonstrated the transformation of the smooth silicon surface into highly interconnected porous network, providing effective template for the uniform deposition of Se and SeGe. UV–Vis absorption measurements shows the enhancement in optical absorption from c-Si to p-Si, p-Si/Se, and p-Si/SeGe. The maximum absorbance increased from average 1.8 for c-Si to 2.7 for porous 3.9 and reached 4.8 for the porous Si/SeGe heterostructure, showing the improvement in broadband light harvesting. The enhanced optical response is attributed to the synergistic effects of multiple light scattering within the porous architecture and the complementary absorption characteristics of Se and Ge. These results demonstrate that SeGe-modified porous silicon is promising light-absorbing material for advanced Si-based photovoltaic and optoelectronic applications.
Glucose monitoring plays a crucial role in clinical diagnostics, particularly in the management of diabetes mellitus. The development of non-enzymatic glucose sensors has attracted considerable attention owing to their potential for improved stability and operational robustness compared with enzyme-based systems. In this study, a Cu(II) complex (CuL₂) was synthesized from the halogen-substituted Schiff base ligand, (Z)-2-(((4-chloro-2-iodophenyl)imino)methyl)phenol (HL). The ligand was prepared by condensation of 2-hydroxybenzaldehyde with 2-iodo-4-chloroaniline and subsequently coordinated to Cu(II) using copper acetate. Both the ligand and its complex were comprehensively characterized by FT-IR, UV–Vis spectroscopy, elemental (CHN) analysis, high-resolution mass spectrometry, 1H and 13C NMR spectroscopy, and single-crystal X-ray diffraction. Single-crystal analysis revealed that the Cu(II) complex crystallizes in the monoclinic crystal system (space group C2/c) and adopts a square-planar coordination geometry through bidentate coordination of the azomethine nitrogen and phenolate oxygen atoms. The electrochemical performance of the ligand and CuL₂ toward non-enzymatic glucose sensing was investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and an extended-gate field-effect transistor (EGFET) in alkaline medium. Under the investigated conditions, the CuL₂ complex exhibited enhanced electrocatalytic responses toward glucose oxidation relative to the free ligand, with improved sensitivity and lower limits of detection across the three sensing platforms. The enhanced electrochemical behaviour is attributed to the combined influence of the electron-withdrawing halogen substituents and the redox-active copper centre. Density functional theory (DFT) calculations on the CuL₂–glucose system at the 6–31 + G(d,p)/LANL2DZ level provided further insight into the interaction between CuL₂ and glucose and supported the proposed catalytic pathway. Overall, these findings demonstrate the potential of halogen-substituted Cu(II) Schiff base complexes as a platforms for the development of non-enzymatic glucose sensors.
A novel Ni8 cluster with the molecular formula [Ni₈(L2−)8(CH3OH)2] (1) (H2L = (E)-2-((5-bromo-2-hydroxybenzylidene)amino)-6-methoxybenzoic acid) has been synthesized by one-pot condensation and coordination self-assembly and structurally characterized. X-ray diffraction analysis reveals that cluster 1 displays a linear-shaped octanuclear structure and each central Ni(II) ions in 1 adopt a distorted octahedron coordination geometry. Catalytic performance studies indicates that cluster 1 can effectively convert CO2 with epoxides forming cyclic carbonates under mild reaction conditions. What's more, cluster 1 as heterogeneous catalyst can be reused at least five times with a negligible loss of catalytic activity.
