Showing papers on "Tetrahedral molecular geometry published in 2015"
TL;DR: In this article, six new 1-benzoyl-3-phenyl-thiourea and 1-(2-methylphenyl)thIourea complexes of mercury(II) were obtained in the reactions of the ligands with HgX2 in methanol (X = Cl, Br, I).
330 citations
TL;DR: In this paper, the series of acenaphthylene-1-[2,6-bis(bis(4-fluorophenyl)methyl)-4-methylphenylimino]-2-arylimine derivatives and their dichloronickel complexes were synthesized and fully characterized as well as the single-crystal X-ray diffraction of representative nickel complexes, revealing a distorted tetrahedral geometry.
90 citations
TL;DR: In this article, the first Mg-containing analogs of the Zintl phase compound Ca14AlSb11 were reported, which are isostructural with the Mg2+ compound and crystallize in the tetragonal space group I41/acd (Z = 8) and are obtained by annealing the mixture of the elements at 1075-1275 K.
Abstract: Magnesium-containing Zintl phase compounds Yb14MgSb11 and Ca14MgSb11 have been prepared by annealing the mixture of the elements at 1075–1275 K. These compounds are isostructural with the Zintl compound Ca14AlSb11 and crystallize in the tetragonal space group I41/acd (Z = 8). Single-crystal X-ray data (90 K) were refined for Yb14MgSb11 [a = 16.625(9) A, c = 22.24(2) A, V = 6145(8) A3, and R1/wR2 (0.0194/0.0398)] and Ca14MgSb11 [a = 16.693(2) A, c = 22.577(5) A, V = 6291(2) A3, R1/wR2 (0.0394/0.0907)]. This structure type has been shown to be highly versatile with a large number of phases with the general formula A14MPn11 (A = Ca, Sr, Ba, Yb, Eu; M = Mn, Zn, Nb, Cd, Group 13 elements; Pn = Group 15 elements). The two compounds reported in this paper are the first Mg-containing analogs. Replacing M with Mg, which is divalent with no d-orbitals, probes electronic structure and properties of this structure type. Mg2+ is well-known to prefer tetrahedral geometry and allows for integration of the properties of ...
86 citations
TL;DR: The main target of this paper is to get an interesting data for the preparation and characterizations of metal oxide (MO) nanoparticles using H2L Schiff base complexes as precursors through the thermal decomposition procedure.
51 citations
TL;DR: In this paper, the σacceptor ability of saturated (four-coordinate) heavier group 14 element compounds toward group 11 metals is related to σ*(E-F) molecular orbital levels, which mainly depend on the deviation of the geometry around E from tetrahedral geometry to trigonal bipyramidal.
42 citations
TL;DR: In this article, a new organic-inorganic hybrid metal complex, 1-Ethylpiperazine-1,4-diium tetrachlorocadmate was synthesized and the structure was determined by single crystal X-Ray diffraction analyses.
39 citations
TL;DR: A series of 1-(2,4-dibenzhydryl-6-chlorophenylimino)-2-aryliminoacenaphthylene derivatives (L1-L5) was synthesized and reacted with nickel halides to form the corresponding nickel complexes LNiX2 (X = Br, Ni1-Ni5; X = Cl, Ni6-Ni10) as mentioned in this paper.
Abstract: A series of 1-(2,4-dibenzhydryl-6-chlorophenylimino)-2-aryliminoacenaphthylene derivatives (L1-L5) was synthesized and reacted with nickel halides to form the corresponding nickel complexes LNiX2 (X = Br, Ni1-Ni5; X = Cl, Ni6-Ni10). The molecular structures of representative complexes Ni2 and Ni5 were determined by single crystal X-ray diffraction, indicating the distorted square planar geometry around the nickel atom of complex Ni2 and the distorted tetrahedral geometry around the nickel atom of complex Ni5, respectively. Upon activation with low amounts of ethylaluminium sesquichloride (Et3Al2Cl3, EASC), all nickel complexes exhibited high activities up to 1.09 x 10(7) g of PE per mol of Ni per h toward ethylene polymerization, producing branched polyethylenes. Most importantly, these systems showed good thermo-stability, even at 80 degrees C maintaining the activity with 3.76 x 10(6) g of PE per mol of Ni per h.
37 citations
TL;DR: In this paper, the results of IR, UV-vis, and 1H NMR spectral data and thermal analysis for 1 and 2 suggest that the binding of silver and copper t...
Abstract: Silver(I) and copper(II) complexes of 4-amino-N-(4,6-dimethyl-2-pyrimidinyl) benzenesulfonamide (smz) have been synthesized and characterized by elemental analysis and infrared (IR), 1H NMR, and UV–vis spectroscopy. [Ag(smz)(pyridine)] (1) crystallizes in monoclinic system with space group P21/c and Z = 4, while [Cu(smz)2(pyridine)2]·H2O (2) crystallizes in triclinic system with space group P-1 and Z = 2. X-ray analysis revealed that silver in 1 is four-coordinate exhibiting distorted tetrahedral geometry, while copper in 2 is coordinated to six nitrogens leading to a highly distorted octahedral geometry. The molecular structures of both 1 and 2 are stabilized by N–H⋯O and C–H⋯π intermolecular and C–H⋯O intramolecular interactions. Water plays a significant role in crystal packing by forming strong N–H⋯Owater intramolecular as well as Owater–H⋯N intermolecular interactions in 2. The results of IR, UV–vis, 1H NMR spectral data and thermal analysis for 1 and 2 suggest that the binding of silver and copper t...
36 citations
TL;DR: This work proposes a efficient method that permits a fast convergence of variational calculations to be applied to tetrahedral AB4 molecules for which a use of high symmetry is crucial for vibrational calculations.
Abstract: A simultaneous use of the full molecular symmetry and of an exact kinetic energy operator (KEO) is of key importance for accurate predictions of vibrational levels at a high energy range from a potential energy surface (PES). An efficient method that permits a fast convergence of variational calculations would allow iterative optimization of the PES parameters using experimental data. In this work, we propose such a method applied to tetrahedral AB4 molecules for which a use of high symmetry is crucial for vibrational calculations. A symmetry-adapted contracted angular basis set for six redundant angles is introduced. Simple formulas using this basis set for explicit calculation of the angular matrix elements of KEO and PES are reported. The symmetric form (six redundant angles) of vibrational KEO without the sin(q)−2 type singularity is derived. The efficient recursive algorithm based on the tensorial formalism is used for the calculation of vibrational matrix elements. A good basis set convergence for the calculations of vibrational levels of the CH4 molecule is demonstrated.
33 citations
TL;DR: The umbrella distortions of the trigonal bipyramid are identified as being the most relevant types of transition state structures for the phosphoryl group transfer reactions for phosphatases and this may be related to the possibility that vanadium is an inhibitor for enzymes that support both exploded and five-coordinate transition states.
32 citations
TL;DR: In this article, the coordination modes of dimethyl pyridine-2,6-dicarboxylate derivatives were studied by CSD to predict the behavior of MPC in reactions with metals.
TL;DR: A new series of Co(II), Ni (II) and Cu(II) complexes of (Z)-2-oxo-2-(phenylamino)-N'-(1-(pyridin-2-yl)ethylidene)acetohydrazide (H2OPPAH) have been prepared and characterized by conventional techniques and spectral data indicated that the ligand acts as neutral or mononegative NNO tridentate.
TL;DR: In this article, three binuclear silver(I) complexes were synthesized and characterized by elemental analyses, IR spectroscopy and X-ray single crystal diffraction, and their binding affinity for DNA follows the order 1 > 2 > 3.
Abstract: Three new binuclear silver(I) complexes, namely, [Ag2(Meobb)2](pic)2·2H2O (1), [Ag2(Etobb)2(pic)](pic)·(CH3CN) (2) and [Ag2(Bobb)2(pic)2] (3) (Meobb = 1,3-bis(1-methylbenzimidazol-2-yl)-2-oxapropane, Etobb = 1,3-bis(1-ethylbenzimidazol-2-yl)-2-oxapropane, Bobb = 1,3-bis(1-benzylbenzimidazol-2-yl)-2-oxapropane, pic = picrate), have been synthesized and characterized by elemental analyses, IR spectroscopy and X-ray single crystal diffraction. Complex 1 displays an Ag2(Etobb)2 dimeric structure. Each silver(I) ion is coordinated to two nitrogen atoms that adopt a distorted linear configuration. In complex 2, the coordination environment of silver(I) atoms is different. The Ag1 ion is coordinated in a T-shaped tri-coordinated geometry and the Ag2 is best described to be in a distorted tetrahedron. Complex 3 exhibits a discrete di-silver metallacyclic framework. One silver atom (Ag1) is present in a distorted tetrahedral geometry, whereas the other silver atom (Ag2) is five-coordinated with two nitrogen atoms, oxygen atoms and the Ag1 to form a distorted square-based pyramidal configuration. The interactions of the three complexes with calf thymus DNA (CT-DNA) has been investigated by electronic absorption titration, fluorescence spectroscopy and viscosity measurements, and the modes of CT-DNA binding to the complexes have been proposed. Experimental results suggest that the silver(I) complexes bind to DNA in an intercalation mode, and their binding affinity for DNA follows the order 1 > 2 > 3. The DNA-binding studies demonstrate that steric hindrance has a large influence on the binding ability to DNA. The complex that has smaller steric hindrance binds more strongly to DNA.
TL;DR: In this paper, the structure of the compound [Ag2(C10H10N3O3S) 2(C5H5N)3] has been characterized by elemental analysis, infrared, UV and NMR spectroscopy.
TL;DR: Density functional theory has been employed calculating the equilibrium geometries and vibrational frequencies of metal-phenylalanine complexes at B3LYP level of theory using 6-31G(d) and SDD basis sets and reveals representative metal-to-ligand charge transfer and d-d transitions bands.
TL;DR: The frequency of the hydroxide stretch is found to be sensitive to the vibrational Stark shift induced by the charged metal center, as observed previously for the smaller [MOH](+)(H2O) species.
Abstract: Infrared vibrational predissociation spectra of transition metal hydroxide clusters, [MOH]+(H2O)1–4·D2 with M = Mn, Fe, Co, Ni, Cu, and Zn, are presented and analyzed with the aid of density functional theory calculations. For the [MnOH]+, [FeOH]+, [CoOH]+ and [ZnOH]+ species, we find that the first coordination shell contains three water molecules and the four ligands are arranged in a distorted tetrahedral geometry. [CuOH]+ can have either two or three water molecules in the first shell arranged in a planar arrangement, while [NiOH]+ has an octahedral ligand geometry with the first shell likely closed with five water molecules. Upon closure of the first coordination shell, characteristic stretch frequencies of hydrogen-bonded OH in the 2500–3500 cm−1 region are used to pinpoint the location of the water molecule in the second shell. The relative energetics of different binding sites are found to be metal dependent, dictated by the first-shell coordination geometry and the charge transfer between the hydroxide and the metal center. Finally, the frequency of the hydroxide stretch is found to be sensitive to the vibrational Stark shift induced by the charged metal center, as observed previously for the smaller [MOH]+(H2O) species. Increasing solvation modulates this frequency by reducing the extent of the charge transfer while elongating the M–OH bond.
TL;DR: In this paper, the Jahn-Teller effect at Cu2+ in cuprospinel CuFe2O4 was investigated using high-pressure single-crystal synchrotron X-ray diffraction techniques at the Photon Factory, KEK, Japan.
Abstract: The Jahn-Teller effect at Cu2+ in cuprospinel CuFe2O4 was investigated using high-pressure single-crystal synchrotron X-ray diffraction techniques at beamline BL10A at the Photon Factory, KEK, Japan. Six data sets were collected in the pressure range from ambient to 5.9 GPa at room temperature. Structural refinements based on the data were performed at 0.0, 1.8, 2.7, and 4.6 GPa. The unit-cell volume of cuprospinel decreases continuously from 590.8(6) to 579.5(8) A3 up to 3.8 GPa. Least-squares fitting to a third-order Birch-Murnaghan equation of state yields the zero-pressure volume V = 590.7(1) A3 and bulk modulus K = 188.1(4.4) GPa with K ′ fixed at 4.0. The structural formula determined by electron microprobe analysis and site occupancy refinement is represented as T (Fe3+0.90Cu2+0.10) M (Fe3+1.10Fe2+0.40Cu2+0.50)O4. Most of the Cu2+ are preferentially distributed onto the octahedrally coordinated ( M ) site of the spinel structure. With pressure, the arrangement of the oxygen atoms around the M cation approaches a regular octahedron. This leads to an increase in the electrostatic repulsion between the coordinating oxygen ions and the 3 d z2 orbital of M Cu2+. At 4.6 GPa, a cubic-tetragonal phase transition is indicated by a splitting of the a axis of the cubic structure into a smaller a axis and a longer c axis, with unit-cell parameters a = 5.882(1) A and c = 8.337(1) A. The tetragonal structure with space group I 41/ amd was refined to R 1 = 0.0332 and wR 2 = 0.0703 using 38 observed reflections. At the M site, the two M -O bonds parallel to the c -axis direction of the unit cell are stretched with respect to the four M -O bonds parallel to the a-b plane, which leads to an elongated octahedron along the c -axis. The cubic-to-tetragonal transition induced by the Jahn-Teller effect at Cu2+ is attributable to this distortion of the CuO6 octahedron and involves Cu 3 d z2 orbital, ab initio quantum chemical calculations support the observation. At the tetrahedrally coordinated ( T ) site, on the other hand, the tetrahedral O- T -O bond angle increases from 109.47° to 111.7(7)°, which generates a compressed tetrahedral geometry along the c -axis. As a result of the competing distortions between the elongated octahedron and the compressed tetrahedron, the a unit-cell parameter is shortened with respect to the c unit-cell parameter, giving a c / a ′ ratio ( ![Formula][1] ) slightly greater than unity as referred to cubic lattice ( c / a ′ = 1.002). The c / a ′ value increases to 1.007 with pressure, suggesting further distortions of the elongated octahedron and compressed tetrahedron.
[1]: /embed/mml-math-1.gif
TL;DR: In this paper, three new dimethyl aluminium complexes (LAlMe2) containing aminophenol ligands were synthesized and characterized by different spectroscopic techniques and elemental analysis.
TL;DR: In this article, a single crystal X-ray analysis of the PIC-copper(II) complex was performed in an acetonitrile solution and it was shown that the metal ion adopts tetrahedral geometry, while a distorted square pyramidal coordination is also possible in the absence of solvent molecules.
TL;DR: The 2:1 Schiff base condensates of 4-methyl-2,6-dibenzoylphenol (mdbpH) with ethane-1,2-diamine, L1H2 and L2H2, respectively, were isolated and used to prepare nickel(II) derivatives.
TL;DR: In this paper, the synthesis and characterization of metal complex of tridentate Schiff base ligand derived from the inserted condensation of 2-aminobenzimidazole with salicylaldehyde (2-hydroxybenzaldehyde) in a 1':'1 molar ratio was discussed.
Abstract: The present paper deals with the synthesis and characterization of metal complex of tridentate Schiff base ligand derived from the inserted condensation of 2-aminobenzimidazole (1H-benzimidazol-2-amine) with salicylaldehyde (2-hydroxybenzaldehyde) in a 1 : 1 molar ratio. Using this tridentate ligand, complex of Zn(II) with general formula ML has been synthesized. The synthesized complex was characterized by several techniques using molar conductance, elemental analysis, FT-IR, and mass and 1HNMR spectroscopy. The elemental analysis data suggest the stoichiometry to be 1 : 1 [M : L]. The complex is nonelectrolytic in nature as suggested by molar conductance measurements. Infrared spectral data indicate the coordination between the ligand and the central metal ion through deprotonated phenolic oxygen, imidazole nitrogen of benzimidazole ring, and azomethine nitrogen atom. Spectral studies suggest tetrahedral geometry for the complex. The pure compound, synthesized ligand, and metal complex were screened for their antimicrobial activity.
TL;DR: DFT calculations corroborate the existence of equilibria between four- and five-coordinated complexes of the asymmetric chiral PNP pincer ligand and the mechanism for the CO addition was investigated.
Abstract: Treatment of anhydrous FeX2 (X = Cl, Br) with 1 equiv. of the asymmetric chiral PNP pincer ligands PNP-R,TAD (R = iPr, tBu) with an R,R-TADDOL (TAD) moiety afforded complexes of the general formula [Fe(PNP)X2]. In the solid state these complexes adopt a tetrahedral geometry with the PNP ligand coordinated in κ2P,N-fashion, as shown by X-ray crystallography and Mossbauer spectroscopy. Magnetization studies led to a magnetic moment very close to 4.9μB reflecting the expected four unpaired d-electrons (quintet ground state). In solution there are equilibria between [Fe(κ3P,N,P-PNP-R,TAD)X2] and [Fe(κ2P,N-PNP-R,TAD)X2] complexes, i.e., the PNP-R,TAD ligand is hemilabile. At −50 °C these equilibria are slow and signals of the non-coordinated P-TAD arm of the κ2P,N-PNP-R,TAD ligand can be detected by 31P{1H} NMR spectroscopy. Addition of BH3 to a solution of [Fe(PNP-iPr,TAD)Cl2] leads to selective boronation of the pendant P-TAD arm shifting the equilibrium towards the four-coordinate complex [Fe(κ2P,N-PNP-iPr,TADBH3)Cl2]. DFT calculations corroborate the existence of equilibria between four- and five-coordinated complexes. Addition of CO to [Fe(PNP-iPr,TAD)X2] in solution yields the diamagnetic octahedral complexes trans-[Fe(κ3P,N,P-PNP-iPr,TAD)(CO)X2], which react further with Ag+ salts in the presence of CO to give the cationic complexes trans-[Fe(κ3P,N,P-PNP-iPr,TAD)(CO)2X]+. CO addition most likely takes place at the five coordinate complex [Fe(κ3P,N,P-PNP-iPr,TAD)X2]. The mechanism for the CO addition was also investigated by DFT and the most favorable path obtained corresponds to the rearrangement of the pincer ligand first from a κ2P,N- to a κ3P,N,P-coordination mode followed by CO coordination to [Fe(κ3P,N,P-PNP-iPr,TAD)X2]. Complexes bearing tBu substituents do not react with CO. Moreover, in the solid state none of the tetrahedral complexes are able to bind CO.
TL;DR: Infinite rectangular-tubular helices, [MX2L] (M = Zn(ii), Hg(ii); X(-) = Cl(-), Br(-); L = bis(3-pyridyl)cyclotetramethylenesilane), have been efficiently constructed via the combined effects of the potential flexible conformers of L and the tetrahedral geometry of M(ii) ions.
Abstract: Infinite rectangular-tubular helices, [MX2L] (M = Zn(II), Hg(II); X− = Cl−, Br−; L = bis(3-pyridyl)cyclotetramethylenesilane), have been efficiently constructed via the combined effects of the potential flexible conformers of L and the tetrahedral geometry of M(II) ions. This helical molecular system affords a racemic mixture of P- and M-helices in a crystal. The helical pitches (7.8934(4)–8.1560(2) A) that are sensitive to the nature of M(II) ions and halide anions are attributable to subtle change in the flexible dihedral angles between the two pyridyl groups around Si and the M(II) hinges. Their photoluminescence intensities, correspondingly, are in the order [ZnCl2L] > [ZnBr2L] ≫ [HgCl2L] > [HgBr2L]. Zinc(II) complexes show recyclable catalytic effects on the transesterification reaction in the order [ZnCl2L] > [ZnBr2L]. Calcination of [ZnCl2L] and [ZnBr2L] at 500 °C produces uniform hexagonal tubular spire crystals of 1.2 × 1.2 × 4.0 μm3 dimensions and spheres, respectively.
TL;DR: The self-consistent charge density functional tight binding/molecular mechanics and ensemble averaged variational transition state theory/multidimensional tunneling methods have been employed to investigate the reaction mechanism and to calculate the rate constant of the NS3/NS4A + NS5A/5B acylation reaction.
Abstract: The self-consistent charge density functional tight binding/molecular mechanics (SCC-DFTB/MM) and ensemble averaged variational transition state theory/multidimensional tunneling (EA-VTST/MT) methods have been employed to investigate the reaction mechanism and to calculate the rate constant of the NS3/NS4A + NS5A/5B acylation reaction. This reaction belongs to the vital cycle of the hepatitis C virus once it infects the human cell. A concerted reaction mechanism, with a single transition state in which the tetrahedral geometry has already been adopted and the peptide bond is starting to break, has been determined. This reaction supposes an example where the proposed general two-step serine protease acylation reaction mechanism does not occur, being related to the fact that the enzyme is particularly efficient for the NS5A/5B substrate. The transition state characterized here for the acylation reaction can be a good initial structure in the reach of NS3/NS4A inhibitors based on TS analogues. On the other h...
TL;DR: In this paper, a 1:1 metal:ligand stoichiometry and a distorted tetrahedral geometry for the coordination mercury centers were obtained from X-ray powder diffraction data.
TL;DR: In this article, three novel anthracene-based ferrocenylselenoethers, 1,5-diselena-3-(anthracen-9′-ylmethyl)-[5]ferrocenophane (L3), 1,3-bis(ferricen-seleno)-2-(anthrasenyl-yloxy)-ethylseleno]FERCORENE) (1), [Cu2Br2(L2)2] (L2 = 1,1′-bis[2.25CH2Cl2
Abstract: Three novel anthracene-based ferrocenylselenoethers, 1,5-diselena-3-(anthracen-9′-ylmethyl)-[5]ferrocenophane (L3), 1,3-bis(ferrocenylseleno)-2-(anthracen-9′-ylmethyl)propane (L4) and N,N-bis[2-(ferrocenylselena)ethyl]-N-(anthracen-9′-ylmethyl)amine (L5) and their Cu(I) complexes, [Cu2Br2(L2)2] (L2 = 1,1′-bis[2-(anthracen-9′-yloxy)-ethylseleno]ferrocene) (1), [Cu2I2(L2)2] (2), [Cu2I2(L3)2]·1.25CH2Cl2 (3) and [Cu4I4(L5)2]·CH2Cl2 (4), have been prepared and structurally characterized. The X-ray crystallography analysis reveals that the complexes 1–3 possess a rhomboidal Cu2X2 core which is sandwiched by two L ligands through two Se atoms to form a dimer, while 4 owns a distorted cubane-like Cu4I4 core which is double-bridging linked by two L5 ligands via two Se atoms to produce a 1D loop chain. Each Cu(I) ion in 1–4 displays a distorted tetrahedral geometry. The unique structural feature in L3–L5 is the coexistence of a redox moiety (ferrocenyl) and a fluorescent chromogenic group (anthracenyl). In the cation sensing study, L3 and L4 present multiresponsive signals for Cu2+ and Hg2+, L5 for Cu2+, Zn2+ and Hg2+. The selectivity can be tuned by incorporating an additional donor N atom, and/or oxidation of the ferrocene unit.
TL;DR: In this article, the synthesis, characterization and molecular structure of two new Ag(I) complexes with 3,4-lutidine (34lut) have been reported.
TL;DR: This study validated the unusual pseudo tetrahedral molecular structure formed around the Cd(II) cation and confirmed the charge transfer mechanisms through second order perturbation theory analysis of the Fox Matrix.
TL;DR: In this paper, the orientation of the coordination sites of the receptor in the main chain polymer significantly determines the selective detection behavior for metal ions, and a template for the suitable design of a Zn2+ sensor was provided.
Abstract: The stereochemistry of the coordination sites of a ligand plays a specific role in its binding with metals in a specific geometry. Herein, we designed and successfully prepared three different fluorene-based (A–B)n-type salen polymers (achiral FSP1, FSP2, and chiral FSP3), wherein the A-part is fluorophore and the B-part is the receptor. In the receptor, the coordination sites have four atoms (ONNO) that can bind any metal ion, but the orientation of ONNO differs in the three polymers. This orientation of the coordination site (i.e., the stereochemistry) into the receptor part of the polymer makes them more selective for a particular metal ion. In this study, it is shown that the orientation of the coordination sites of the receptor in the main chain polymer significantly determines the selective detection behavior for metal ions. Among the three polymers, FSP1 and FSP2 are sensitive towards different metal ions but are not selective towards any particular metal ion. However, in contrast, FSP3 is highly sensitive and selective to Zn2+ ions over other metal ions with a turn-on visible bright blue fluorescent color. This turn-on detection of the polymer is possibly due to the suppression of photo-induced electron transfer (PET) upon binding with Zn2+ ions. Theoretical calculations were also performed to show the orientation of the coordination sites. In FSP3, the coordination sites orient in a distorted tetrahedral fashion, which is very much prone to bind Zn2+ in a nearly tetrahedral geometry and that makes it more selective for Zn2+ ions only. The coordination geometry was also supported by 2D NMR studies. This report provides a template for the suitable design of a Zn2+ sensor, depending on the nature of the receptor incorporated into the main chain polymer.