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Non-covalent sulfur interactions through the lens of quantum chemistry
No full textAmong the chalcogens, sulfur stands out for the remarkable diversity of its chemical bonding and physical forms, from covalent chains and rings to polymeric structures and non-covalent interactions in molecular and crystalline systems. On the occasion of the centenary of quantum chemistry, this work highlights how modern quantum-chemical approaches, such as DFT calculations, electrostatic potential maps, NBO analysis, and potential energy surface investigation, enable a deeper understanding of sulfur-based interactions. Particular attention is given to S···S contacts that determine molecular geometry, crystal packing, and the stability of sulfur-containing systems. Examples from our studies, including quantum-chemical investigations of S···S interactions in the α-allotrope of elemental sulfur (Kretić, Medaković & Veljković, 2023), illustrate (i) preferred geometries and energetic characteristics of these contacts, (ii) their influence on molecular arrangement and crystal packing, and (iii) how theoretical analysis provides predictive insights into structures once rationalized only empirically. This work also demonstrates how quantum-chemical knowledge of sulfur interactions can be extended to the design of new materials and supramolecular assemblies.Centennial of Quantum Theory: Progress in Atomic and Molecular Structure (CEQPAS 2025), Institute of Physics Belgrade, Pregrevica 118, Belgrade, Serbia, 03-05 November 2025.Book of abstracts: [https://cer.ihtm.bg.ac.rs/handle/123456789/8868]Book of abstracts: [https://doi.org/10.5281/zenodo.17467615
Role of magnesium in solidification feeding of hypoeutectic Al-Si5-Mg alloys
No full textThe growing demand for high-performance Al-Si casting alloys stems from their excellent mechanical
properties in engineering applications. Hypoeutectic Al-Si-Mg alloys offer superior fluidity, low thermal
expansion, and corrosion resistance; however, they face solidification challenges such as shrinkage
porosity. This study investigates magnesium's influence on feeding regions in AlSi5Mg alloys. Results show
that increasing magnesium content from 0% to 0.6% significantly affects interdendritic and burst feeding
regions, potentially impacting shrinkage porosity formation
The hydration effect on hydrogen bond strength in the second coordination sphere of ethylenediamine and glycine metal complexes
No full textHydration of metal complexes is important in chemistry and biochemistry. In this study, we calculated the interaction energies of NH···O hydrogen bonds of ethylenediamine complexes and NH···O and O···HO hydrogen bonds of glycine complexes in the second coordination sphere. The systems consisting of a metal complex and a non-coordinated (free) water molecule were solvated with implicit water using the polarizable continuum model (PCM). The calculations were performed at M06L-GD3(PCM)/def2-TZVPP level in aqueous solution. The studied complexes included octahedral cobalt(III), octahedral nickel(II), and square-planar palladium(II), each with different charges. The interaction energies for NH···O and O···HO interactions in the second coordination sphere weaken upon solvation across all complexes, irrespective of the metal ion type or geometry. As the complex charge increased, the weakening in hydrogen bond interactions upon solvation became more pronounced. Upon solvation, hydrogen bonds are 3–29 % weaker for neutral complexes, 42–55 % weaker for singly charged complexes, 50–69 % weaker for doubly charged complexes, and 57 % weaker for triply charged complexes. The weakening of hydrogen bonds for singly negatively charged complexes is 17–47 %. However, after solvation, the trend of interaction energies remained consistent with that in the gas phase, since solvated complexes with higher charges exhibited stronger interactions than those with lower charges. Notably, solvation did not affect the dHO distance significantly, which remained the same as in the gas phase for most complexes
Izuzetna aktivnost Pt3Ni(111) katalizatora za elektrooksidaciju ugljen monoksida
No full textBulk CO oxidation on the Pt3Ni(111) single-crystal alloy was
investigated using electrochemical methods (EC), scanning tunneling
microscopy (STM), infrared adsorption spectroscopy (IRAS) and density
functional theory (DFT) calculations. According to polarization curves,
Pt3Ni(111) has a two-fold higher diffusion current density and is significantly
more active for CO oxidation than Pt(111). According to the IR and STM
results, Pt3Ni(111) exhibits a high activity for CO oxidation due to a unique
surface morphology and an electronic effect caused by Ni from the subsurface
layer. The active sites for CO oxidation in a preignition potential area are
identified as adislands, which are composed of strongly undercoordinated Pt
atoms observed on the surfaces of both catalysts. The increased activity of
Pt3Ni(111) compared to Pt(111) is explained by the fact that the Pt3Ni(111)
surface has more adislands and an earlier potential for OH formation.Oksidacija CO je proučavana na monokristalnoj leguri Pt3Ni(1 )
korišćenjem elektro emijski meto a ) skenirajuće tunelske mikroskopije
(STM), infracrvene adsorpcione spektroskopije (IRAS) i proračuna zasnovani
na teoriji funkcionala gustine (DFT). Polarizacione krive su pokazale da je
Pt3 i ) mnogo aktivniji za oksi a iju o Pt ) sa vostruko većom
gustinom difuzione struje. Rezultati dobijeni IR i STM metodama pokazali su da
je visoka aktivnost Pt3Ni(111) za oksidaciju CO uzrokovana elektronskim
efektom izazvanim i iz po površinskog sloja i specificnom površinskom
morfologijom. Površinska ostrva, sastavljena od visoko nekoordinisanih Pt
atoma etektovani na površinama oba katalizatora označena su kao aktivna mesta za oksidaciju CO u oblasti potencijala pre paljenja Povećana aktivnost
Pt3 i ) u pore enju sa Pt objašnjava se većim brojem površinskih ostrva
prisutni na površini i ranijim poten ijalom formiranja H na površinskim
ostrvima kod Pt3Ni(111) katalizatora
The effect of cobalt loading on efficiency of hybrid Co-Al-carbon-smectite catalysts in process of advanced oxidative degradation of Acid Orange 10 in presence of Oxone®
No full textFour Co-supported hybrid Co-Al-carbon-smectite catalysts were synthetized and tested in catalytic
reaction of oxidative degradation of azo-dye Acid Orange 10 (AO10) in presence of Oxone®.
Catalysts were obtained by simultaneously intercalation of Al-Keggin and HDTMA+ cation on
2μm fraction of the smectite clay, and impregnated with different amount of Co2+ ions form cobalt-acetate in mass-ratio of 1%, 3%, 5%, and 10%. Finally, the obtained samples were submitted to
heat treatment in Ar atmosphere at 400 °C and denoted as 1-Co-Al/H-S, 3-Co-Al/H-S 5-Co-Al/H-S and 10-Co-Al/H-S. The samples were characterized using Inductively coupled plasma - optical
emission spectrometry (ICP–OES), FT-IR spectroscopy and X-ray powder diffraction. The UV-VIS spectroscopy was applied to monitor the concentration of AO10 during the degradation
process at λmax=478 nm. The degradation percentage in 4 h for catalysts 1-Co-Al/H-S, 3-Co-Al/H-S, 5-Co-Al/H-S and 10-Co-Al/H-S were 62.1%, 84.1%, 94.4%, and 95.1% respectively. The results show that the catalysts 5-Co-Al/H-S and 10-Co-Al/H-S exhibit similar degradation percentages for
this reaction. Based on these findings, it can be concluded that 5% Co2+ is the optimal impregnation loading for this reaction
Changes in plant enzymatic activity in response to PFOA
No full textPer- and polyfluoroalkyl substances (PFAS), including perfluorooctanoic acid (PFOA), are highly persistent environmental pollutants that induce stress responses in plants1. Understanding plant adaptation mechanisms under PFAS exposure, and the interaction between PFAS and plant systems is crucial
for assessing the risks of PFAS contamination to plants, and the understanding of underlaying mechanisms can be translated to the plant application in environmental monitoring and phytoremediation2.
Hydroponic experiments were conducted with cucumber (Cucumis sativus) and zucchini (Cucurbita
pepo L.) cultivated in nutrient solutions containing 0.1 mg/L PFOA.
Plant responses were evaluated through chlorophyll content, Normalized Difference Vegetation Index
(NDVI), and the activity of oxidative stress-related enzymes. Leaf reflectance spectra (330–1100 nm)
were recorded using a SpectraVue Leaf Spectrometer. Antioxidant response was analyzed by various
enzymatic assays. Zucchini exposed to PFOA showed enhanced superoxide dismutase (SOD) activity in
leaves, stems, and roots, with minor increase in leaf absorption at 670 nm. NDVI values declined slightly
compared to controls. In cucumbers, responses were stronger: SOD activity increased by 43 % in aerial
parts and 52 % in roots, while catalase (CAT) activity in roots rose nearly tenfold. Notably, laccase activity, absent in controls, was strongly induced in PFOA-treated cucumber roots.
Exposure to PFOA disrupted redox homeostasis, increasing reactive oxygen species (ROS) production
and activating antioxidant defenses. The induction of laccase in cucumbers suggests a dual role in
oxidative stress mitigation and potential PFAS degradation. These findings highlight cucumbers and
zucchini as bioindicators of PFAS exposure, with cucumber showing particular promise for phytoremediation applications
Variability of Essential Oil and Wax in Needles of Abies pinsapo Boiss. (Pinaceae)
No full textSpring needles of Abies pinsapo Boiss. contained 84 identifiable volatile compounds. Monoterpene hydrocarbons dominated the essential oil (86.2%), with β-pinene (34.8%), α-pinene (24.6%), and limonene+β-phellandrene (11.9%) as the major constituents. Stepwise discriminant analysis distinguished young needles from 1- and 2-year-old needles. The average nonacosan-10-ol content was 36.9%, with minimal differences among age classes. Needle n-alkanes ranged from C16 to C33, dominated by C29 (19.02%), C23 (18.89%), C27 (17.62%), and C25 (13.01%). The most abundant n-alkanes were C23 in young, C27 in 1-year-old, and C29 in 2-year-old needles. The total Carbon Preference Index of n-alkanes ranged from 3.2 to 7.3 (mean 4.6), peaking in young needles (6.0). The total average chain length ranged from 24.7 to 27.2 (mean 26.2). Principal component analysis also separated young needles from older ones
Poster presentation: Crystal Structure, Computational Insights, and Biological Activities of Thiazole-Based Hydrazone Zinc(II) Complex [ZnL(NCS)(H₂O)]
No full textWe synthesized a novel zinc(II) complex, [ZnL(NCS)(H₂O)] (1), which originates from a hydrazone ligand (HL) formed by condensing 2-acetylthiazole and thiosemicarbazide. The structure was characterized using single-crystal X-ray diffraction, UV-Vis, and NMR spectroscopy. DFT calculations explored solution behavior in DMSO. TDDFT calculations aligned well with experimental UV-Vis. Biological activities (cytotoxic, antibacterial and antifungal) of complex 1 was evaluated.Poster presented at: 7th EuChems European Inorganic Chemistry Conference, Book of Abstracts, September 7-11, 2025, BelgradeAbstract: [https://cer.ihtm.bg.ac.rs/handle/123456789/8806
Poster: Catalytic activity of Mn(II) Salt vs. Mn(II) Complexes in Epoxidation with m-CPBA
No full textCatalytic activity of Mn(II) salt and mononuclear Mn(II) complexes was investigated in the epoxidation of alkenes with m-CPBA under ambient conditions. Three Schiff base ligands were synthesized and according complexes in reactions with MnCl2·4H2O. Time-resolved Raman spectroscopy was used to monitor substrate conversion, oxidant consumption, and product formation. Styrene was selected as a reference substrate for initial assessment of the catalytic performance of the manganese complexes and salt. The data reveal that simple Mn(II) salt exhibit significantly higher catalytic activity than Mn(II) complexes, indicating that ligand coordination inhibits the reactivity of the manganese centre. The catalytic efficiency of Mn(II) perchlorate was particularly notable, achieving near complete oxidation of styrene within minutes under mild conditions. Furthermore, epoxidation of a range of alkenes demonstrating that Mn(II) salts provide broad substrate scope and high selectivity.Poster presented at: 7th EuChems European Inorganic Chemistry Conference, Book of Abstracts, September 7-11, 2025, BelgradeAbstract: [https://cer.ihtm.bg.ac.rs/handle/123456789/8807
CH/O hydrogen bonds in the second coordination sphere of bipyridine complexes with water: stronger than classical water–water hydrogen bonds
No full textAlthough CH/O interactions are generally recognized as weak noncovalent interactions, CH/O interactions in the second coordination sphere of 2,2′-bipyridine (bipy) complexes are surprisingly strong. Coordinated bipy ligands can form strong interactions; the calculated interaction energies for CH/O interactions of neutral cobalt(II), copper(II), and palladium(II) complexes with a water molecule range from −3.00 to −5.57 kcal/mol. The interaction energies are influenced by the coordination number of the complex and by the position of the interacting hydrogen atom. As the coordination number decreases, the CH/O interaction becomes stronger, while bifurcated interactions are stronger than linear ones. The strongest calculated interaction is a bifurcated interaction in a square-planar palladium(II) complex. The calculated energies and distances of CH/O interactions in bipy complexes are consistent with the data observed by analyzing crystal structures from the Cambridge Structural Database. These findings suggest that such interactions could be relevant for the design of new materials and functional molecular systems where noncovalent bonding plays a key role