Trigonal Geometry Research Articles

A study using physical sphere-in-contact models to investigate the structure of close-packed nanoparticles supported on flat hexagonal, square and trigonal lattices

The tailored design of nanoparticles becomes more important with the advancement of heterogeneous catalysis and materials science. The formation of nanoparticles in catalysts with a specific geometry of the active site becomes necessary to improve activity and selectivity in catalysis. Here we have used physical sphere-in-contact models of various nanoparticles with hexagonal, square and trigonal geometries on flat close-packed surfaces to understand how the distribution of (100) and (111) sites changes as a function of nanoparticle (NP) size in a simplified model of nanoparticle supported metals. The results from this approach clearly show that in 2-layer NPs that have a hexagonal base have 2–3 times more (100) sites than the square and trigonal base NPs as a function of the number of atoms in the NP. In 3D isotropic NPs, this phenomenon is even more pronounced than the 2-layer NPs. We derive equations that estimate the number of (100), (111), the number of atoms and the aspect ratio as a function of n. These equations are important in tailoring the properties of NPs supported on close-packed metal surfaces, which may find applications in materials science, nanotechnology and catalysis.

A Series of Lanthanide Coordination Polymers as Luminescent Sensors for Selective Detection of Inorganic Ions and Nitrobenzene.

Seven new lanthanide coordination polymers, namely [Ln(cpt)3H2O)]n(Ln = La (1), Pr (2), Sm (3), Eu (4), Gd (5), Dy (6), and Er (7)), which were synthesized under hydrothermal conditions using 4'-(4-(4-carboxyphenyloxy)phenyl)-4,2':6',4'-tripyridine (Hcpt) as the ligand. The crystal structures of these seven complexes were determined using single-crystal X-ray diffraction, and they were found to be isostructural, crystallizing in the triclinic P1- space group. The Ln(III) ions were nine-coordinated with tricapped trigonal prism coordination geometry. The Ln(III) cations were coordinated by carboxylic and pyridine groups from (cpt)- ligands, forming one-dimensional ring-chain structures. Furthermore, the luminescent properties of complexes 1-7 were investigated using fluorescent spectra in the solid state. The fluorescence sensing experiments demonstrated that complex 4 exhibits high selectivity and sensitivity for detecting Co2+, Cu2+ ions, and nitrobenzene. Moreover, complex 3 shows good capability for detecting Cu2+ ions and nitrobenzene. Additionally, the sensing mechanism was also thoroughly examined through theoretical calculations.

Evaluation of the Effectiveness of Geogrids Manufactured from Recycled Plastics for Slope Stabilization-A Case Study.

This study aimed to investigate the sustainable use of recycled plastics, specifically polypropylene (PP) and high-density polyethylene (HDPE), in the manufacture of geogrids for geotechnical and civil engineering applications. Plastics were collected from a recycling center, specifically targeting containers used for food, cleaning products, and other domestic packaging items. These plastics were sorted according to the Möbius triangle classification system, with HDPE (#2) and PP (#5) being the primary categories of interest. The research methodologically evaluates the mechanical properties of PP/HDPE (0/100, 25/75, 50/50, 75/25 and 100/0% w/w) composites through tensile and flexural tests, exploring various compositions and configurations of geogrids. The results highlight the superiority of pure recycled HDPE processed into 1.3 mm thick laminated yarns and hot air welded for 20 to 30 s, exhibiting a deformation exceeding 60% in comparison to the PP/HDPE composites. Through SolidWorks® Simulation, it was shown that the adoption of a trigonal geogrid geometry optimizes force distribution and tensile strength, significantly improving slope stabilization efficiency. Based on the results obtained, a laboratory-scale prototype geogrid was developed using an extrusion process. The results underscore the importance of careful composite design and yarn configuration selection to achieve the desired mechanical properties and performance in geogrid applications. It emphasizes the potential of recycled plastics as a viable and environmentally friendly solution for stabilizing slopes, contributing to the reduction in plastic waste and promoting sustainable construction practices.

Luminescent Ln3+-based silsesquioxanes with a β-diketonate antenna ligand: toward the design of efficient temperature sensors.

We report the synthesis and single-crystal X-ray diffraction, magnetic, and luminescence measurements of a novel family of luminescent cage-like tetranuclear silsesquioxanes (PhSiO1.5)8(LnO1.5)4(O)(C5H8O2)6(EtOH)2(CH3CN)2⋅2CH3CN (where Ln = Tb, 1; Tb/Eu, 2; and Gd, 3), featuring seven-coordinated lanthanide ions arranged in a one-capped trigonal prism geometry. Compounds 1 and 2 exhibit characteristic Tb3+ and Tb3+/Eu3+-related emissions, respectively, sensitized by the chelating antenna acetylacetonate (acac) ligands upon excitation in the UV and visible spectral regions. Compound 3 is used to assess the energies of the triplet states of the acac ligand. For compound 1, theoretical calculations on the intramolecular energy transfer and multiphonon rates indicate a thermal balance between the 5D4 Stark components, while the mixed Tb3+/Eu3+ analog 2, with a Tb:Eu ratio of 3:1, showcases intra-cluster Tb3+-to-Eu3+ energy transfer, calculated theoretically as a function of temperature. By utilizing the intensity ratio between the 5D4→7F5 (Tb3+) and 5D0→7F2 (Eu3+) transitions in the range 11-373K, we demonstrate the realization of a ratiometric luminescent thermometer with compound 2, operating in the range 11-373K with a maximum relative sensitivity of 2.0% K-1 at 373K. These findings highlight the potential of cage-like silsesquioxanes as versatile materials for optical sensing-enabled applications.

Dinuclear cadmium(II) complexes with distorted octahedral/monocapped trigonal prism coordination geometries: synthesis, crystal structure, DFT/TD-DFT calculation and photocatalytic degradation of methylene blue

Two Cd(II) complexes [Cd2(L1)2(dca)(NO3)] (1) and [Cd2(L2)2(SCN)(NO3)] (2) (HL1 = 2-methoxy-6-[(2-phenylamino-ethylimino)-methyl]-phenol; and HL2 = 2-[(2-ethylamino-ethylimino)-methyl]-6-methoxy-phenol), have been synthesized and characterized by single crystal structure analysis, IR and mass spectroscopic studies. Both the complexes 1 and 2 possess a triclinic crystal system with space group P1¯. In complex 1, geometry around one metal centre is distorted octahedral and other centre is distorted monocapped trigonal prism, whereas in complex 2, both the metal centres possess distorted octahedral geometries. Strong NH⋅⋅⋅O and weak aromatic CH⋅⋅∙O hydrogen bonding interactions in 1 and strong NH⋅⋅⋅O and NH⋅⋅⋅S hydrogen bonding in 2 results 1D and 2D supramolecular structures, respectively. Experimentally determined electronic spectral data have been compared with the calculated data obtained by DFT and TD-DFT calculation. Photocatalytic abilities of 1 and 2 have been examined by using spectroscopic technique and found that in presence of UV light both the complexes catalytically decomposed methylene blue by 54.0 % and 50.3 %, respectively.

Rational Design of Metallylenes for Hydrogenation Reactions

AbstractThe hydrogenation of alkenes, alkynes, carbonyls, and imines by H2‐activated metallylenes (H3C−EH2−L, CELH2; E=Si, Ge, Sn and L=NMe2, PMe2) was studied using relativistic density functional theory at ZORA‐BP86/TZ2P. By means of activation strain and Kohn–Sham molecular orbital analyses, the physical factors underlying the trends in reactivity were identified and quantified. Firstly, the hydrogenation reactivity increases on descending Group 14, that is from silylenes (E=Si) to stannylenes (E=Sn). This reactivity trend originates primarily from a reduced energy required to break the bonds between the Group 14 atom and the hydrogen atoms because the strength of these bonds decreases from Si−H to Ge−H to Sn−H. Secondly, the reactivity decreases as the Group 15 ligand changes from nitrogen to phosphorus (L=NMe2, PMe2) which stems from the trigonal pyramidal PMe2 geometry compared to the trigonal planar NMe2 geometry. The latter can, therefore, effectively engage in stronger orbital interactions with the substrate than the former, due to a more efficient HOMO–LUMO orbital overlap. By combining our insights, we rationally designed an optimally tuned catalyst (Group 14 atom and ligand) considering the overall catalytic cycle involving H2 activation of the metallylene and subsequent hydrogenation.

Structures of Th4+ aqueous solutions: insights from AIMD and metadynamics simulations.

Solution chemistry of actinide ions is critical to understanding the solvation behaviors and hydrolysis process. Using tetravalent thorium ion Th4+ as a representative example, we investigate the local structures and dynamic behaviors of hydrated Th4+ ions by ab initio molecular dynamics (AIMD) simulations using the recently developed norm-conserving pseudopotentials and basis sets optimized for actinides (J.-B. Lu et al., J. Chem. Theory Comput. 2021, 17, 3360-3371). AIMD simulations reveal two distinct solvation shells, with the first shell comprising 9 water molecules at approximately rTh-O = 2.50 Å and exhibiting a tricapped trigonal prism geometry. These conclusions are confirmed through metadynamics simulations and further structural analysis. AIMD simulations also show the slight effect of temperature and counterions on the structure of the solution. The structured solvation shells of the highly charged Th4+ ion with the specific geometry, distinct from the structure of liquid water, lead to corresponding structural changes in the hydrogen bond network in water. Additionally, beyond the solvent-shared ion pair (SIP) state observed in the unbiased AIMD simulations, the metadynamics simulations reconstruct a two-dimensional free energy surface that clearly indicates the potential stability of the contact ion pair (CIP) state in the system with Cl- as a counterion. The findings in this work provide insights into the solution chemistry of actinides and serve as a reference for studying other actinide solution systems.

Controlling the symmetry of hexamonodentate 3d-transition metal complexes through symmetry propagation from high-symmetry Ti-Mo and Zr-Mo clusters via hydrogen-bonding interactions.

The symmetry of one of the simplest hexamonodentate complexes, [M(H2O)6]2+ (M = Fe, Co, Ni, and Zn), was controlled by tuning interactions in the second coordination sphere. Highly symmetric Ti-Mo or Zr-Mo cluster cations acted as symmetry templates, imposing a crystallographic trigonal coordination geometry in the hexamonodentate complexes through intermolecular hydrogen-bonding interactions. Magnetic measurements revealed that the ideal trigonal symmetry results in weak spin-orbit coupling for high-spin FeII complexes, despite the T-term ground state in the octahedral geometry. In contrast, high-spin CoII analogues with the T-term ground state exhibited strong spin-orbit coupling. DFT studies supported that a d6 FeII ion in the D3 symmetry has a 5A1 ground state while a d7 CoII in the same symmetry has a 4E ground state. Single-ion magnet behavior was observed in the CoII complexes. These results demonstrate that incorporating a diamagnetic, highly symmetric cluster enables precise symmetry control in single-ion magnets containing only monodentate ligands.

An structural study of nine-membered monometallocycles of Pd(II) and Pt(II) employing the 1,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)butane ligand

Two nine-membered metallocycles of PdII (1) and PtII (2) containing 1,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)butane ligand (L1) have been prepared and their structures were determined by IR, NMR spectroscopy, and by single-crystal X-ray diffraction analysis. The molecular structures of L1 display that the pyrazolyl groups adopt an anti-conformation, while in 1 and 2 a discrete nine-membered monometallic macrocycle is generated by the assembly of one ligand and one metal atom, and the ring adopts a twist-chair-boat conformation. The ligand L1 in complexes 1 and 2 acts as cis-chelating ligand via a κ2 N,N coordination mode by the nitrogen atoms of the pyrazolyl rings. In compounds 1 and 2 the metal center adopts a planar geometry. The molecular structure of 1 and 2 also revealed two intramolecular anagostic interactions M•••Hγ–C(sp3) (M = Pd and Pt) with M•••H distances between 2.689 and 2.780 Å, which are important to stabilize the nine membered ring formed. Considering those two M•••Hγ interactions, the ligand L1 generates a κ4 N,N,H,H coordination mode and the metal centers adopt a trigonal prism geometry. The crystal packing of L1, 1 and 2 displayed supramolecular networks promoted mainly by C–H•••π interactions, which were analyzed by Hirshfeld Surface Analysis

Quasi-open Cu(I) sites for efficient CO separation with high O2/H2O tolerance.

Carbon monoxide (CO) separation relies on chemical adsorption but suffers from the difficulty of desorption and instability of open metal sites against O2, H2O and so on. Here we demonstrate quasi-open metal sites with hidden or shielded coordination sites as a promising solution. Possessing the trigonal coordination geometry (sp2), Cu(I) ions in porous frameworks show weak physical adsorption for non-target guests. Rational regulation of framework flexibility enables geometry transformation to tetrahedral geometry (sp3), generating a fourth coordination site for the chemical adsorption of CO. Quantitative breakthrough experiments at ambient conditions show CO uptakes up to 4.1 mmol g-1 and CO selectivity up to 347 against CO2, CH4, O2, N2 and H2. The adsorbents can be completely regenerated at 333-373 K to recover CO with a purity of >99.99%, and the separation performances are stable in high-concentration O2 and H2O. Although CO leakage concentration generally follows the structural transition pressure, large amounts (>3 mmol g-1) of ultrahigh-purity (99.9999999%, 9N; CO concentration < 1 part per billion) gases can be produced in a single adsorption process, demonstrating the usefulness of this approach for separation applications.

Photocatalytic degradation of methylene blue using sunlight-powered coordination polymers constructed from a tetracarboxylate linker

Here, we report the preparation of three coordination polymers - [Mn2(btec)]n, 1; [Ce2(H2btec)(btec)(H2O)2]n, 2; and [Fe(Hbtec)(H2O)2]n3 from 1,2,4,5-benzenetetracarboxylic acid (H4btec). Physicochemical characterization of the coordination polymers were undertaken using microanalysis, X-ray crystallography, FTIR, PXRD, TGA/DSC, and UV/visible spectrophotometry to confirm the identities of the compounds. The Mn(II) centres in 1 exhibit octahedral geometry coordinated by six oxygen atoms and crystallizes in the monoclinic space group I2/m. In 2, Ce(III) centres adopt tricapped trigonal prism geometry, coordinated by three btec4-, three from H2btec2- and the oxygen from one coordinated water molecule. It crystallizes in the triclinic space group P1¯. 3 is composed of an Hbtec ion and two water molecules coordinated to the Fe (III) ion. The band gaps of 1, 2, and 3 are 2.87, 3.10, and 3.61 eV, respectively, while their hydrogen peroxide-assisted efficiencies for the photodegradation of methylene blue are 91, 94, and 100 % respectively. An active species trapping experiment showed that an increase in hydroxy radicals (•OH) explains the enhanced efficiencies and provide an insight into the mechanism of the photodegradation of methylene blue by the photocatalysts. Efficiencies of mixtures of 2/H2O2 and 3/H2O2 reduced only slightly over five cycles of use and PXRD data revealed that 2 and 3 were chemically stable over the three cycles. Overall, the coordination polymers could serve as potential candidates for industrial-scale methylene blue degradation in the aqueous phase.

New Organotin (IV) Compounds Derived from Dehydroacetic Acid and Thiosemicarbazides: Synthesis, Rational Design, Cytotoxic Evaluation, and Molecular Docking Simulation.

Organotin complexes were prepared through a one-pot reaction with three components by reacting thiosemicarbazide or 4-methyl-3-thiosemicarbazide or 4-phenylthiosemicarbazide, dehydroacetic acid (DHA) and dibutyl, diphenyl, dicyclohexyl, and bis[(trimethylsilyl)methyl]tin(IV) oxides; all complexes were characterized by infrared (IR), ultraviolet-visible (UV-vis), mass spectrometry (MS), and nuclear magnetic resonance (NMR) spectroscopy. The 119Sn NMR revealed chemical shifts corresponding to a pentacoordinated environment in solution. The X-ray crystallography of the two complexes evidenced the formation of monomeric complexes with a pentacoordinated geometry around tin via three donor atoms from the ligand, the sulfur of the thiol, the nitrogen of the imine group, and the oxygen of the pyran ring. The geometries of the five-coordinated complexes 3a (Bu2SnL3), 3c (Ph2SnL3), and 3d (Cy2SnL3) acid were intermediate between square pyramidal and trigonal bipyramidal, and complex 1a (Bu2SnL1) adopted a bipyramidal trigonal geometry (BPT). The sulforhodamine B assay assessed the cytotoxicity of organotin(IV) complexes against the MDA-MB-231 and MCF-7 (human mammary adenocarcinoma) cell lines and one normal COS-7 (African green monkey kidney fibroblast). The IC50 values evidenced a significant antiproliferative effect on cancer cells; the complexes were more potent than the positive cisplatin control and the corresponding ligands, dehydroacetic acid thiosemicarbazone (L1), dehydroacetic acid-N(4)-methylthiosemicarbazone (L2), and dehydroacetic acid-N(4)-phenylthiosemicarbazone (L3). The IC50 values also indicated that the organotin(IV) complexes were more cytotoxic against the triple-negative breast cell line MDA-MB-231 than MCF-7, inducing significant morphological alterations. The interactions of organotin(IV) 1c (Ph2SnL1), 1d (Cy2SnL1), and 1e (((CH3)3SiCH2)2SnL1) were evaluated with ss-DNA by fluorescence; intensity changes of the fluorescence were indicative of the displacement of ethidium bromide (EB), confirming the interaction of the organotin(IV) complexes with ss-DNA; the results showed a DNA binding affinity. The thermodynamic parameters obtained through isothermal titration calorimetry showed that the interaction of 1c (Ph2SnL1), with ss-ADN, was exothermic. Molecular docking studies also demonstrated that the organotin(IV) complexes were intercalated in DNA by conventional hydrogen bonds, carbon-hydrogen bonds, and π-alkyl interactions. These complexes furthermore showed a greater affinity towards DNA than cisplatin.

Photoluminescence and Radiation Luminescence in a Hybrid Cuprous (I) Halide: (4,4‐Difluoro‐bipiperidinium)3Cu2I5

AbstractCopper (I) based halide scintillators have received high attention due to their high light yield. At the same time, researchers are increasingly interested in exploring organic‐inorganic hybrid copper(I) based halides, due to the diversity and tunability of structures. Here, we describe high‐efficiency photoluminescence and X‐ray excited luminescence in (DFPD)3Cu2I5 (1) (DFPD=4,4‐difluoro‐bipiperidinium). 1 is comprised of a unique [Cu2I5]3− cluster, which have typical structure allowing high‐transition‐probability self‐trapped exciton emission (one Cu+ ion adopts the tetrahedral coordination geometry, the other trigonal planar coordination geometry, the Cu−Cu distance (2.574 Å) is short). Accordingly, 1 shows efficient yellow‐green photoluminescence with the maximum at 527 nm, a full‐width at half‐maximum of 99.2 nm, a large Stokes shift of 214 nm (1.6 eV) and a quantum yield of 77.15 %. Polycrystalline 1 can also convert high‐energy X‐ray photons into UV‐visible pulsed fluorescence with the light yield of 5000 photons/MeV. This finding plays a valuable role in the development of organic‐inorganic hybrid copper(I) based scintillators.

Boron Polycation Supported by Cyclic Bis(carbodiphosphorane).

A novel cyclic bis(carbodiphosphorane) ligand was prepared and investigated in coordination with group 13 elements, B, Al and Ga. Al and Ga afforded dinuclear adduct where two metal centers were bridged by the bis(carbodiphosphorane) ligand. In contrast, the reaction with boron trichloride afforded a monomeric dicationic three-coordinate boron species composed of one boron moieties and one ligand. The structures of these products were determined by X-ray crystallography. In the dicationic boron compound, the sterically constrained cyclic structure enforced the boron center to acquire strained trigonal geometry with wide C-B-C angle of 140°. Furthermore, theoretical investigation with DFT and NBO suggested a significant contribution of tricationic two-coordinate boron resonance structure supported by two CDP ligands.

ONO-pincer Zn(II) & Cd(II) complexes: Synthesis, structural characterization, Hirshfeld surface analysis and CT-DNA interactions

Four new ONO pincer complexes of type Na2[Cd(L′)(OAc)2] (2a), Na2[Zn(L)(OAc)2] (3a), [Zn(LMe)(OAc)2] (4a) and [Cd(LMe)(OAc)2] (4b), where L′ = N,N'-bis(4-methylpyridin-2-yl)pyridine-2,6-dicarboximidate, L = N,N'-di(pyridin-2-yl)pyridine-2,6-dicarboximidate and LMe=N,N'-bis(1-methylpyridinium-2-yl)pyridine-2,6-dicarboximidate, were synthesized. The ligands were generated during complex formation reaction by the in situ deprotonation of their respective pro-ligands; H2L′ (2), H2L (3) and H2LMe (OTf)2 (4). The newly synthesized metal complexes were characterized by elemental analysis, FT-IR, NMR (1H and 13C), and single crystal X-ray diffraction techniques. The single crystal analysis of 4b disclosed that the central Cd(II) ion is adopting capped trigonal prism geometry. The nature of intermolecular interactions within the crystal structure, fingerprint plots, and molecular surface contours have been studied using Hirshfeld surface analysis. The DNA binding assay was conducted by molecular absorption spectroscopy, viscosity measurement and molecular modeling simulations. DNA-interaction measurements show that the compounds have a high propensity for binding with DNA as a groove binder.

A family of mono-nuclear lanthanide-radical complexes: Synthesis, structures, magnetic and fluorescent properties

Two new rare earth complexes based on TEMPO derivative namely [Ln(hfac)3(H2O)hmb-TEMPO] (Ln = Gd 1, Tb 2; hmb-TEMPO = 4-((2-hydroxy-3-methoxybenzylidene) amino)-2,2,6,6-tetramethyl; hfac = hexafluoroacety lacetonate) were successfully synthesized through reacting hmb-TEMPO radical and Ln(hfac)3. Single-crystal X-ray diffraction reveals that 1 and 2 are isostructural complexes in which the LnIII ion is surrounded nine oxygen atoms and displayed distorted tricapped trigonal prism geometry. Magnetic studies show that antiferromagnetic interactions dominate in complex 1. Nonzero out-of-phase signals were observed for complex 2, indicating single-molecule magnet behavior. The low-temperature photoluminescence spectrum of complex 2 were investigated and discussed in detail.

Identifying native point defect configurations in α-alumina

Intimately intertwined atomic and electronic structures of point defects govern diffusion-limited corrosion and underpin the operation of optoelectronic devices. For some materials, complex energy landscapes containing metastable defect configurations challenge first-principles modeling efforts. Here, we thoroughly reevaluate native point defect geometries for the illustrative case of α-Al2O3 by comparing three methods for sampling candidate geometries in density functional theory calculations: displacing atoms near a naively placed defect, initializing interstitials at high-symmetry points of a Voronoi decomposition, and Bayesian optimization. We find symmetry-breaking distortions for oxygen vacancies in some charge states, and we identify several distinct oxygen split-interstitial geometries that help explain literature discrepancies involving this defect. We also report a surprising and, to our knowledge, previously unknown trigonal geometry favored by aluminum interstitials in some charge states. These new configurations may have transformative impacts on our understanding of defect migration pathways in aluminum-oxide scales protecting metal alloys from corrosion. Overall, the Voronoi scheme appears most effective for sampling candidate interstitial sites because it always succeeded in finding the lowest-energy geometry identified in this study, although no approach found every metastable configuration. Finally, we show that the position of defect levels within the band gap can depend strongly on the defect geometry, underscoring the need to conduct careful searches for ground-state geometries in defect calculations.

Synthesis and Structural Characterization of p-Carboranylamidine Derivatives.

In this contribution, the first amidinate and amidine derivatives of p-carborane are described. Double lithiation of p-carborane (1) with n-butyllithium followed by treatment with 1,3-diorganocarbodiimides, R-N=C=N-R (R = iPr, Cy (= cyclohexyl)), in DME or THF afforded the new p-carboranylamidinate salts p-C2H10B10[C(NiPr)2Li(DME)]2 (2) and p-C2H10B10[C(NCy)2Li(THF)2]2 (3). Subsequent treatment of 2 and 3 with 2 equiv. of chlorotrimethylsilane (Me3SiCl) provided the silylated neutral bis(amidine) derivatives p-C2H10B10[C{iPrN(SiMe3)}(=NiPr)]2 (4) and p-C2H10B10[C{CyN(SiMe3)}(=NCy)]2 (5). The new compounds 3 and 4 have been structurally characterized by single-crystal X-ray diffraction. The lithium carboranylamidinate 3 comprises a rare trigonal planar coordination geometry around the lithium ions.

Complexes of 2-Amino-3-methylpyridine and 2-Amino-4-methylbenzothiazole with Ag(I) and Cu(II): Structure and Biological Applications

Coordination complexes (1–4) of 2-amino-4-methylbenzothiazole and 2-amino-3-methylpyridine with Cu(CH3COO)2 and AgNO3 were prepared and characterized by UV/Vis and FT-IR spectroscopy. The molecular structure for single crystals of silver complexes (2 and 4) were determined by X-ray diffraction. The coordination complex (2) is monoclinic with space group P21/c, wherein two ligands are coordinated to a metal ion, affording distorted trigonal geometry around the central Ag metal ion. The efficient nucleophilic center, i.e., the endocyclic nitrogen of the organic ligand, binds to the silver metal. Ligands are coordinated to adopt cis arrangement, predominantly due to steric reasons. The O(2) and O(3) atoms of the NO3− group further play an important role in such type of ligand arrangement by hydrogen bonding with the NH2 group of ligands. Complex (4) is orthorhombic, P212121, comprising two molecules of 2-amino-3-methylpyridine as ligand coordinated with the metal ion, affording a polymeric structure. The coordination behavior of the ligand is identical to that in complex 2, wherein ring nitrogen is coordinated to the metal center and bridged to another metal ion through an NH2 group. The resulting product is polymeric in nature with the Ag metal in the backbone and ligand as the bridge. Compounds (2–4) were found to be luminescent, while 1 did not show such activity. All compounds were screened for their preliminary biological activities such as antibacterial, antioxidant and enzyme inhibition. Compounds exhibited moderate activity in these tests.

Synthesis and properties of [NR4]3[SbS4] (R = Me, Et, n-Pr, n-Bu) and the crystal structures of [N(n-Bu)4]3[SbS4]⋅6H2O and [N(n-Bu)4]3[Sb(S2O3)3]·2THF

The tetra-alkylammonium tetrathioantimonate(V) salts, [NR4]3[SbS4] (R = Me, Et, n-Pr, n-Bu), have been prepared in basic solution from aqueous [NR4]OH, sulfur and Sb2S3, and characterised by microanalysis, IR, Raman, 1H and 121Sb NMR spectroscopy. The crystal structure of [N(n-Bu)4]3[SbS4]·6H2O shows the presence of the tetrahedral [SbS4]3− anion (disordered over two sites), and also connected through an H-bonding network with the lattice water molecules. The alkylammonium salts are soluble in water and, with the exception of [NMe4]3[SbS4], are also soluble in weakly polar organic solvents, including halocarbons and MeCN. Solubility increases with the R group Me < Et < n-Pr < n-Bu, making the [N(n-Bu)4)3[SbS4] a convenient reagent to explore coordination chemistry or materials applications for which water as the solvent is not suitable. [N(n-Bu)4]3[Sb(S2O3)3]·2THF, the first thiosulfate complex of a p-block element, was produced by slow decomposition of [N(n-Bu)4]3[SbS4] in THF solution in the presence of the [NH(n-Bu)3]Cl (as a source of H+), confirming the instability of the [SbS4]3− anion in acidic media, and the crystal structure of [N(n-Bu)4]3[Sb(S2O3)3]·2THF shows a trigonal antiprismatic coordination geometry with a S3O3 donor set at the antimony(III) centre in the anion.