Showing papers on "Tetrahedral molecular geometry published in 2020"
TL;DR: In this article, a density functional theory based quantum chemical calculations have been performed at B3LYP/6-31G (d,p)/Def2-SVP(Sn) level of theory.
35 citations
TL;DR: This work provides an interesting metalloligand method not only to induce the spa-tial growth of metallic clusters to achieve highly symmetric structures, but also to enhance their stability which is crucial for future application.
Abstract: A series of increasingly large silver nanoclusters with a varied combination of Archimedean and/or Platonic solid arrangements was constructed using a flexible trifurcate TiL3 (L = Salicylic acid o
27 citations
TL;DR: The results indicated that complex 3 can be efficiently utilized as a heterogeneous bifunctional catalyst for the Knoevenagel condensation and multicomponent reactions to develop biologically important organic molecules.
Abstract: Five novel zinc(II) and cadmium(II) β-oxodithioester complexes, [Zn(L1)2] (1), [Zn(L2)2]n (2), [Zn(L3)2]n (3) [Cd(L1)2]n (4), [Cd(L2)2]n (5), with β-oxodithioester ligands, where L1 = 3-(methylthio)-1-(thiophen-2-yl)-3-thioxoprop-1-en-1-olate, L2 = 3-(methylthio)-1-(pyridin-3-yl)-3-thioxoprop-1-en-1-olate, and L3 = 3-(methylthio)-1-(pyridin-4-yl)-3-thioxoprop-1-en-1-olate, were synthesized and characterized by elemental analysis, IR, UV-vis, and NMR spectroscopy (1H and 13C{1H}). The solid-state structures of all complexes were ascertained by single-crystal X-ray crystallography. The β-oxodithioester ligands are bonded to Zn(II)/Cd(II) metal ions in an O∧S and N chelating/chelating-bridging fashion leading to the formation of 1D (in 2-4) and 2D (in 5) coordination polymeric structures, but complex 1 was obtained as a discrete tetrahedral molecule. Complex 4 crystallizes in the C2 chiral space group and has been studied using circular dichroism (CD) spectroscopy. The multidimensional assemblies in these complexes are stabilized by many important noncovalent C-H···π (ZnOSC3, chelate), π···π, C-H···π, and H···H interactions. The catalytic activities of 1-5 in reactions involving C-C and C-O bond formation have been studied, and the results indicated that complex 3 can be efficiently utilized as a heterogeneous bifunctional catalyst for the Knoevenagel condensation and multicomponent reactions to develop biologically important organic molecules. The luminescent properties of complexes were also studied. Interestingly, zinc complexes 1-3 showed strong lumniscent emission in the solid state, whereas cadmium complexes 4 and 5 exhibited bright luminescent emission in the solution phase. The semiconducting behavior of the complexes was studied by solid-state diffuse reflectance spectra (DRS), which showed optical band gaps in the range of 2.49-2.62 eV.
15 citations
TL;DR: In this paper, the interaction between imidazole (imi) linker with the selected non-steroidal anti-inflammatory drug indomethacin (indo) [1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid) and Zinc(II) acetate dihydrate resulted in the formation of a polymeric complex {[Zn(indo-O)(µ-indo-,O,O,N,O’)(imi
12 citations
TL;DR: In this article, the As−Fe−As bond angle approaches that in a regular tetrahedron, and a geometric design within an epitaxial heterostructure was proposed to induce superconductivity.
Abstract: Fe-based superconductors exhibit a diverse interplay between charge, orbital, and magnetic ordering. Variations in atomic geometry affect electron hopping between Fe atoms and the Fermi surface topology, influencing magnetic frustration and the pairing strength through changes of orbital overlap and occupancies. Here, we experimentally demonstrate a systematic approach to realize superconductivity without chemical doping in BaFe2As2, employing geometric design within an epitaxial heterostructure. We control both tetragonality and orthorhombicity in BaFe2As2 through superlattice engineering, which we experimentally find to induce superconductivity when the As−Fe−As bond angle approaches that in a regular tetrahedron. This approach to superlattice design could lead to insights into low-dimensional superconductivity in Fe-based superconductors.
12 citations
TL;DR: A monolithic nearly centimeter-sized hexagonal supramolecular structure was observed in the giant tetrahedron with short flexible linkers between PBI and POSS cages, while micrometer-sized crystalline helical structure formed in that with completely rigid aromatic linkers.
Abstract: Recently, ordered structures constructed from rigid three-dimensional (3D) shaped polyhedra have been drawing general interest, with the tetrahedron being the simplest one but showing complicated assembly behaviors Rigid tetrahedron building blocks have been shown to form quasicrystalline and crystalline phases with high packing fractions by both simulation and experiments Nevertheless, the study of 3D tetrahedral building blocks is limited, especially in the field of supramolecular self-assembly Here, we present an experimental study of rigid giant tetrahedral molecules constructed by attaching four bulky polyhedral oligomeric silsesquioxane (POSS) cages to a tetrahedral perylene bisimide (PBI) scaffold Self-assembly of these giant tetrahedra is mediated by π-π interaction between the tetrahedral PBI-based scaffolds and their overall tetrahedral symmetry A monolithic nearly centimeter-sized hexagonal supramolecular structure was observed in the giant tetrahedron with short flexible linkers between PBI and POSS cages, while a micrometer-sized crystalline helical structure formed in that with completely rigid aromatic linkers Their significant difference in electrical conductivity could be explained by two completely different packing models of the giant tetrahedra
12 citations
TL;DR: In this paper, the authors report the preparation, spectroscopic characterisation, crystal structure determination and cryomagnetic investigation of three cobalt(II) complexes of formula trans-[Co(bim)4(NCS)2] (1), [Co( bim)2(NCO) 2] (2) and [Co-bim]2(N3)2 ]n (3) (bim = 1-benzylimidazole).
Abstract: We report the preparation, spectroscopic characterisation, crystal structure determination and cryomagnetic investigation of three cobalt(II) complexes of formula trans-[Co(bim)4(NCS)2] (1), [Co(bim)2(NCO)2] (2) and [Co(bim)2(N3)2]n (3) (bim = 1-benzylimidazole). The structure of 1 is made up of neutral [Co(bim)4(NCS)2] mononuclear units, where the cobalt(II) ion is six-coordinate with four monodentate bim ligands in equatorial positions and two N-thiocyanato groups in the axial sites building a slightly compressed octahedron. In contrast to 1, each cobalt(II) ion in 2 is four-coordinate with two imidazole-nitrogen atoms from two bim molecules and two N-cyanato ligands describing a slightly distorted tetrahedral geometry, the value of Okuniewski's structural parameter being 0.925. The structure of 3 consists of uniform chains of cobalt(II) ions connected by double end-to-end azido bridges in equatorial positions with two trans-coordinated bim molecules occupying the axial sites. The Co–Nbim bond lengths in 3 are ca. 0.06 A shorter than the Co–Nazido distances, the value of the tetragonality parameter being 1.03. The intrachain cobalt–cobalt separation is 5.361(1) A, a value which is much shorter than the shortest interchain one (ca. 12.4 A). Detailed solid state ac and dc magnetic studies show that 1 and 2 are field-induced single-ion magnets with D = +88.6 (1) and −6.8 cm−1 (2). Q-band EPR spectrometry measurements for polycrystalline samples of 1 and 2 confirm the signs of D and reveal the occurrence of a strong (1)/low (2) low asymmetry in the g-tensors. Theoretical calculations by CASSCF/NEVPT2 support the results from magnetometry and EPR for 1 and 2. The values of the spin reversal barrier which were obtained from the corresponding Arrhenius plots cover the ranges 48.0–50.2 cm−1 (1) and 25.9–27.2 and 11.5–13.1 cm−1 for the high- and low-temperature relaxation processes (2). Compound 3 exhibits an overall antiferromagnetic behaviour with a maximum of the magnetic susceptibility at ca. 70 K, the intrachain antiferromagnetic coupling being J = −26.5 cm−1 (the spin Hamiltonian being defined as ). This value is of the same nature and its size compares well with those reported for the scarce examples of this type of cobalt(II) chain.
11 citations
TL;DR: A comparative magneto-structural analysis of complexes 4 and 5 points to the high sensitivity of the single-ion magnetic anisotropy of tetrahedral Co(ii) complexes to subtle changes in the first and second coordination spheres of Co(II) ions.
Abstract: Blue crystals of five heteroleptic cobalt(ii) silanethiolates 1-5 have been obtained by the reaction of [Co{SSi(tBuO)3}2(NH3)]2 with aminopyridines and aminomethylpyridines at an appropriate molar ratio and their structural, spectral, thermal and magnetic properties have been established and described. All complexes 1-5 contain Co(ii) ions in a tetrahedral CoN2S2 environment formed by (tBuO)3SiS- residues and pyridines and present variable structures. Complexes 1-3 are mononuclear [Co{SSi(tBuO)3}2(L1)2] (L1 = 2-aminopyridine 2AP, 3-aminopyridine 3AP, and 4-aminopyridine 4AP). The application of 3AMP and 4AMP (3-aminomethylpyridine and 4-aminomethylpyridine) allows either dinuclear complex 4 [Co{SSi(tBuO)3}2(μ-3AMP)]2 or 1D coordination polymer 5 with the formula of [Co{SSi(tBuO)3}2(μ-4AMP)]n to be obtained. The molecular structures of 1-5 were determined by single-crystal X-ray and powder diffraction, UV-vis and FTIR spectrocopy for solid samples and their thermal properties were characterized by TG-DSC and TG-FTIR methods. The dc and ac magnetic and EPR studies of polycrystalline samples have been performed. For all complexes, the obtained data show a behavior typical of paramagnetic high-spin Co(ii) ions in a tetrahedral geometry, with a considerable contribution of the ZFS effect in a low temperature range. All complexes were also probed for SIM behavior. The modeling of the magnetic and EPR data was done for samples 1, 3, 4 and 5 to estimate ZFS parameters. The obtained results imply a negative value of the axial parameter D in complex 4 and positive D values for the rest of the compounds. A comparative magneto-structural analysis of complexes 4 and 5 points to the high sensitivity of the single-ion magnetic anisotropy of tetrahedral Co(ii) complexes to subtle changes in the first and second coordination spheres of Co(ii) ions.
11 citations
TL;DR: Three shape‐persistent imine cages with truncated tetrahedral geometry with different window sizes were studied as hosts for the encapsulation of tetra‐n‐alkylammonium salts of various bulkiness to deduce the activation barriers for these processes.
Abstract: Three shape-persistent [4+4] imine cages with truncated tetrahedral geometry with different window sizes were studied as hosts for the encapsulation of tetra-n-alkylammonium salts of various bulkiness. In various solvents the cages behave differently. For instance, in dichloromethane the cage with smallest window size takes up NEt$_{4}$t$^{+}$ but not NMe$_{4}$t$^{+}$, which is in contrast to the two cages with larger windows hosting both ions. To find out the reason for this, kinetic experiments were carried out to determine the velocity of uptake but also to deduce the activation barriers for these processes. To support the experimental results, calculations for the guest uptakes have been performed by molecular mechanics’ simulations. Finally, the complexation of pharmaceutical interested compounds, such as acetylcholine, muscarine or denatonium have been determined by NMR experiments.
10 citations
TL;DR: In this paper, the reaction of MO (MO) with benzoic acid (HBz) in H2O/MeOH mixture as solvent yields two benzoate compounds: [Zn(µ-Bz)2]n (1) and [Cd(Bz2(H2O)3] (2).
10 citations
TL;DR: In this paper, two new hybrid single crystals having the general formula [(CH3CH2CH2)4N]2MIICl4 with MII=Co (1) and Mn (2) have been synthetised by the slow evaporation process in aqueous solutions.
TL;DR: In this article, four new complexes, [Co(phend)2Cl2] (1), [CoPhend)(ƞ2-NO3)2H2O].2phend (2), [CuPhend) 2Cl2[3] (3) and [Cu2Phend(2μ-OAc)4] (4) have been synthesized by the reaction of two equivalent phend ligands with one equivalent of CoCl2·6H 2O (1).
TL;DR: A series of 3D divalent metallic complexes were synthesized from an unsymmetrical nitrogenous ligand, 3-[(2-hydroxy-5-methyl-phenylimino)-methyl]-napthalen-2-ol as mentioned in this paper.
TL;DR: A series of binuclear azomethine-Zn(II) complexes was successfully synthesized from 4,4-diaminodiphenylsulphide derived Schiff bases as discussed by the authors.
TL;DR: The synthesis of a new phosphine copper(I) complex is reported, along with a detailed analysis of the geometry characterization and its interaction with double-stranded DNA, which confirmed that the van der Waals interaction is the main driving force for the binding process.
TL;DR: In this paper, a series of new copper complexes have been synthesized and completely characterized by pivotal analytical techniques and the coordination geometry around copper(I) complex was best described as distorted tetrahedral geometry.
TL;DR: X-ray single crystal structural determination andoretical calculations demonstrated that the presence of easy-plane magnetic anisotropy for complexes 1 and 2 is in agreement with the experimental data can pave a way to obtain the four-coordinate and seven-coordinated cobalt(II) single-ion magnets(SIMs) by using bidentate ligand.
Abstract: For a long time, the cobalt(II) complex ([Co(napy)4 ](ClO4 )2 ) (napy=1, 8-naphthyridine) has been considered as an eight-coordinate complex without any structural proof. After careful considerations, two complexes [Co(napy)2 Cl2 ] (1) and [Co(napy)4 ](ClO4 )2 (2) based on the bidentate ligand napy were synthesized and structurally characterized. X-ray single-crystal structural determination showed that the cobalt(II) center in [Co(napy)2 Cl2 ] (1) is four-coordinate with a tetrahedral geometry (Td ), while [Co(napy)4 ](ClO4 )2 (2) is seven-coordinate rather than eight-coordinate with a capped trigonal prism geometry (C2v ). Direct-current (dc) magnetic data revealed that complexes 1 and 2 possess positive zero-field splitting (ZFS) parameters of 11.08 and 25.30 cm-1 , respectively, with easy-plane magnetic anisotropy. Alternating current(ac) susceptibility measurements revealed that both complexes showed slow magnetic relaxation behaviour. Theoretical calculations demonstrated that the presence of easy-plane magnetic anisotropy (D>0) for complexes 1 and 2 is in agreement with the experimental data. Furthermore, these results pave the way to obtain four-coordinate and seven-coordinate cobalt(II) single-ion magnets (SIMs) by using a bidentate ligand.
TL;DR: In this paper, two novel Cu(I) complexes with the 2-acetylpyridine-N(4)-phenyl semicarbazone (HL) ligand were investigated by single-crystal X-ray analysis, Hirshfeld surface, and physicochemical and spectroscopic methods.
Abstract: Two novel Cu(I) complexes with the 2-acetylpyridine-N(4)-phenyl semicarbazone (HL) ligand, [CuCl (HL)(PPh3)]∙CH3CN (1) and [CuBr (HL)(PPh3)] (2), were investigated by single-crystal X-ray analysis, Hirshfeld surface, and physicochemical and spectroscopic methods. In both cases, the Schiff base was coordinated by the bidentate ligand via the pyridine nitrogen and the iminic nitrogen atoms. A molecule of triphenylphosphine and a halide ion (Cl− or Br−) completed the coordination sphere of the metal centers. The geometry around the copper atoms was distorted tetrahedral geometry. The secondary coordination sphere of Cu(I) is pentacoordinated and has weak interactions Cu···O of 2.906(1) A and 2.783(1) A. The 3D Hirshfeld surface and the 2D fingerprint plots of the complexes were analyzed quantitatively to verify the presence of intermolecular interactions. By their crystal structure of (2), it is possible to observe π···π stacking interactions between the pyridyl and phenyl rings from HL and also between phenyl rings and the triphenylphosphine ligands forming a 1D network. The biological activity of the Cu(I) salts, the free semicarbazone, and its Cu(I) complexes was evaluated against human cancer cell lines MCF-7 and nontumor cell lines PBMC.
TL;DR: In this article, the reaction of zinc chloride or zinc nitrate hexahydrate with N,N′-cyclohexane-1,2-diylidene-bis(4-fluorobenzoylhydrazide) (L) in acetonitrile and under ambient conditions, produced two different zinc(II) complexes 1 and 2 respectively, with different coordination modes and geometrical shapes.
TL;DR: In this article, the catalytic properties of 1a-3a and 5a-8a Au(III) chloride complexes with these heterocycles (except from 4) were investigated.
TL;DR: Structural correlations confirm the link between the C-Zn-C angle and Zn-N distance and principal component analysis provides a detailed picture of the correlated distortions.
Abstract: The Lewis acidity of a metal center is influenced not only by the electronic properties of the bonded ligands but also by the bond angles, which we suggest to be important for zinc diorganyls. Molecular orbital correlation predicts that a narrower C-Zn-C bond angle of the R2Zn fragment lowers its lowest unoccupied molecular orbital (LUMO) and increases its Lewis acidity, such that it binds added ligands more strongly. Computations on Me2Zn(bipy) (bipy = 2,2'-bipyridine) yield that, for every 10° of C-Zn-C narrowing close to tetrahedral geometry, the Zn-N distance shortens by 0.027 A (0.048 A per 10° for the range 180-90°) and that the LUMO of the Me2Zn fragment drops by 0.24 eV. A total of 10 dialkyl zinc complexes of bipy or 4,4'-di-tert-butyl-2,2'-bipyridine are crystallographically characterized here. Structure correlations (published and new data) confirm the link between the C-Zn-C angle and Zn-N distance. Principal component analysis provides a detailed picture of the correlated distortions. Relevance for zinc fingers/zinc enzymes is discussed.
19 Nov 2020
TL;DR: Schiff base (L) ligand is prepared via condensation of P-Anisaldehyde and ethylene diamine in 2:1 ratio in ethanol as mentioned in this paper, and the structure of the two derivatives are confirmed using various spectroscopic techniques: C, H, N analyses, IR, UV-visible and X-ray diffraction.
Abstract: Schiff base (L) ligand is prepared via condensation of P-Anisaldehyde and ethylene diamine in 2:1 ratio in ethanol. A new complex is prepared by reacting this ligand with metallic salt CdI2. The structure of the two derivatives are confirmed using various spectroscopic techniques: C, H, N analyses, IR, UV-visible and X-ray diffraction. The IR spectrums of ligand and complex show respectively intense peaks at 1629 cm-1 and 1639cm-1 indicating the presence of azomethine group (N=C). The crystal structure of the ligand belongs respectively to monoclinic, space group P21/n. In the crystal packing of the ligand, molecules are linked by a pair of methyl-C-H…O(methoxy) interactions, forming to an infinite one-dimensional chain. The structural characterization of the complex reveals that it crystallizes in an orthorhombic system P with as space group Pbca with a=14.8704 A; b=12.9618 A; c=22.4416 A. The crystal structure of the monomer complex shows a distorted tetrahedral geometry. The CdII center is coordinated by the bidentate schiff base ligand via the two imine groups (N-donor) and the two chlorine atoms. Non-classical intermolecular H-bonds of the type benzene-C—H…O(methoxy) exist and link the monomeric complex, forming one dimensional chains.
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TL;DR: The results demonstrated here show superconductivity in the antiferromagnetic BaFe2As2 without chemical substitution, by atomic level control of local structure through epitaxial superlattice design, and indicates structure and dimensionality play an important role in the superconducting properties in Fe-based superconductors.
Abstract: Fe-based superconductors exhibit a diverse interplay between charge, orbital, and magnetic ordering1-4. Variations in atomic geometry affect electron hopping between Fe atoms5,6 and the Fermi surface topology, influencing magnetic frustration and the pairing mechanism through changes of orbital overlap and occupancies7-11. Here, we experimentally demonstrate a systematic approach to realize superconductivity without chemical doping in BaFe2As2, employing geometric design within an epitaxial heterostructure. We control both tetragonality and orthorhombicity in BaFe2As2 through superlattice engineering, which we experimentally find to induce superconductivity when the As-Fe-As bond angle approaches that in a regular tetrahedron. This approach of superlattice design could lead to insights into low dimensional superconductivity in Fe-based superconductors.
TL;DR: In this article, the coordination attitude of Zn-II and Sn-II complexes was analyzed to be a mono-negative bi-dentate mode within tetrahedral geometry.
TL;DR: In this article, the structure of the Zn(II) complex was determined by a single crystal X-ray diffraction technique and it was shown that the complex crystallizes in the triclinic system with the P-1 space group and has a distorted tetrahedral geometry.
Abstract: The reaction between zinc(II) acetate dihydrate and ((1H-indol-3-yl)methylene)-N-methylhydrazinecarbothioamide (L) in methanol results in the formation of Zn(II) complex [Zn(C11H11N4S)2] (1). The complex is characterized by CHNS and various spectroscopic analyses. The structure of the complex is determined by the single crystal X-ray diffraction technique. XRD reveals that the Zn(II) complex crystallizes in the triclinic system with the P-1 space group and has a distorted tetrahedral geometry. Two ligand molecules are coordinated to the Zn(II) ion in the bidentate monobasic (NS−) fashion.
TL;DR: In this paper, a series of binuclear complexes with the general formula [CuM(pxbtacn-R2)Cl4] were used to study the potential mimics of superoxide dismutase.
TL;DR: A series of Cu(II) complexes, [LnCuCl2] (Ln-=-LA-LF), supported by N′-aromatic-group-substituted N,N-bis((3,5-dimethyl-1H-pyrazol-1-yl)methylamine ligands have been synthesized as mentioned in this paper.
TL;DR: In this paper, tetra-cationic compounds with tetrahedral geometry were synthesized and four cationic units were introduced on a quaternary carbon through -CH2- spacer.
Abstract: Tetra-cationic compounds with tetrahedral geometry were synthesized. Four cationic units were introduced on a quaternary carbon through -CH2- spacer. Despite of steric crowding around the core, hig...
TL;DR: In this paper, a new α-amino-1H Indazolyl-phosphonates derivative 3a-e was synthesized and subjected to solid state characterization by single-crystal X-ray diffraction analysis, and to study their NMR and Hirshfeld surface analysis.
31 Oct 2020
TL;DR: In this paper, 1, 2, 4-triazole Schiff base and its complexes with a theoretical study using PM3 calculation and HyperChem program, photophysical properties, and surface morphology measured by atomic force microscopy.
Abstract: Background: Schiff base compounds derivative from1,2,4-triazole, and their transition metal complexes play an essential role in coordination and bioinorganic chemistry due to biological and industrial applications.
Objective: The work aims to prepare and characterize of 1, 2, 4-triazole Schiff base and its complexes with a theoretical study using PM3 calculation and HyperChem program, photophysical properties, and surface morphology for these complexes.
Methods: 1, 2, 4-triazole Schiff base prepared by condensation reaction between 4-Amino-3-mercapto-5-phenyl-4H-1,2,4-triazole and 2-hydroxy-1-naphthaldehyde, then Schiff base reacted with Co2+, Ni2+, and Cu2+ ions, the synthesized 1, 2, 4-triazole Schiff base, and its complexes were characterized by infrared spectra, magnetic susceptibility, conductivity measurements, photophysical properties, and surface morphology measured by atomic force microscopy. The practical results were reinforced with a theoretical study for these Schiff base complexes. Then the proposed structures of the prepared complexes.
Results: 1, 2, 4-triazole Schiff base act as a chelate ligand. The coordination has occurred through the oxygen of the phenolic group O-H and the nitrogen of the imine group N=C of Schiff base with divalent metal ions. Cobalt complex has a tetrahedral geometry, while the nickel and copper complexes have square planar geometries.
The stability of all compounds was studied by calculating the energy gap by diffuse reflectance spectroscopy and theoretical calculations. Copper Schiff base is a more stable complex due to the lower value of the energy gap, and the copper Schiff base complex is more semiconductivity than the other complexes. Surface morphology, properties of chelating Schiff base ligand and its complexes measured by atomic force microscopy, cobalt Schiff base complex is higher roughness. The bond length of (-C=N-), (-C-O-),(M-O), and (M-N) are affected in the coordination with metal ions, the bond length of the square planar geometry more affected than tetrahedral geometry.
Conclusion: All compounds were prepared successfully, characterized, and photophysical properties were studied.