Showing papers on "Tetrahedral molecular geometry published in 2016"

Structure-Triggered High Quantum Yield Luminescence and Switchable Dielectric Properties in Manganese(II) Based Hybrid Compounds.

Abstract: Two new manganese(II) based organic-inorganic hybrid compounds, C11H21Cl3MnN2 (1) and C11H22Cl4MnN2 (2), with prominent photoluminescence and dielectric properties were synthesized by solvent modulation. Compound 1 with novel trigonal bipyramidal geometry exhibits bright red luminescence with a lifetime of 2.47 ms and high quantum yield of 35.8 %. Compound 2 with tetrahedral geometry displays intense long-lived (1.54 ms) green light emission with higher quantum yield of 92.3 %, accompanied by reversible solid-state phase transition at 170 K and a distinct switchable dielectric property. The better performance of 2 results from the structure, including a discrete organic cation moiety and inorganic metal anion framework, which gives the cations large freedom of motion.

Synthesis, structure, ultrafast kinetics, and light-induced dynamics of CuHETPHEN chromophores

Abstract: Five heteroleptic Cu(I)bis(phenanthroline) chromophores with distinct variation in the steric bulk at the 2,9-phenanthroline position were synthesized using the HETPHEN method, and their ground and excited state properties are described. Analysis of the crystal structures reveals a significant distortion from tetrahedral geometry around the Cu(I) centre which is attributed to favourable aromatic interactions between the two phenanthroline ligands. Ultrafast and nanosecond transient optical spectroscopies reveal that the excited state lifetime can be tuned across two orders of magnitude up to 74 nanoseconds in acetonitrile by changing the 2,9-substituent from hydrogen to sec-butyl. X-ray transient absorption spectroscopy at the Cu K-edge confirmed Cu(I) oxidation to Cu(II) and revealed a decrease of the Cu–N bond lengths in the excited state. The ground and excited state characterization presented here will guide the integration of CuHETPHEN chromophores into complex electron donor–acceptor architectures.

Influences of the protonic state of an imidazole-phenanthroline ligand on the luminescence properties of copper(I) complexes: experimental and theoretical research

Abstract: Two ionic (1a and 1b) and two neutral (2a and 2b) Cu(I) complexes containing an un-deprotonated or a deprotonated nitrogen ligand {2-(4-methyl phenyl) imidazole[4,5-f]-1,10-phenanthroline, MHPIP} and different phosphine ligands (bis[2-(diphenylphosphino) phenyl]ether and PPh3) have been synthesized and characterized by elemental analysis, 1H NMR spectroscopy and X-ray crystallography (1b, 2a and 2b). The complexes adopt a distorted tetrahedral geometry constructed by MHPIP (or MPIP−) and phosphine ligands. The emission spectra show that the ionic complexes exhibit almost ignorable luminescence. However, the deprotonation of the nitrogen ligand makes the neutral complexes exhibit orange or yellow emission both in solution and solid-powder states. Considering the different luminous characters of the neutral complexes, density functional theory (DFT) calculations have been performed at the B3LYP/6-31G** level to provide information about the impact of phosphine ligands on the frontier orbital.

Structurally well-characterized new multinuclear Cu(II) and Zn(II) clusters: X-ray crystallography, theoretical studies, and applications in catalysis

Abstract: Two new trinuclear Cu(II) and dinuclear Zn(II) clusters are crystallized out by reacting the metal salts with the triethanolamine (H3tea) ligand in the presence of benzoic acid (Hba). The complexes are characterized by elemental, thermal, magnetic, spectral (FTIR, UV-Visible, EPR, and photoluminescence) and single crystal X-ray studies. Single crystal X-ray crystallography reveals the composition of the complexes to be [Cu3(H2tea)2(ba)2(NO3)2] (1) and [Zn2(H2tea)(ba)3]H2O (2). FTIR ascertains the binding modes of H2tea−, ba− and NO3−. Triethanolamine binds in both the complexes in the monoanionic (H2tea−) mode. ba− is present as an anchoring auxiliary to generate di- and trinuclear clusters. The Cu(II) ion is present as a distorted octahedral center in the Cu3 cluster (1), while the two Zn(II) ions in 2 have been reported for the first time to possess distorted octahedral as well as tetrahedral geometry in the same molecule. The intriguing features of the non-covalent supramolecular interactions have been investigated and supported theoretically by using Hirshfeld surface analysis and ab initio methods. The solid state photoluminescence (PL) spectra of 1 and 2 disclose the luminescence property of the complexes. Due to the closed or nearly closed shell configuration (d9 or d10), the present complexes are screened for catalytic properties in the hydrocarboxylation of alkanes and cycloalkanes. The catalytic activity data are indicative of the potential catalytic properties of 1 and 2.

Synthesis, spectral, DFT, and antimicrobial studies of tin(II) and lead(II) complexes with semicarbazone and thiosemicarbazones derived from (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone

Abstract: A new series of metal complexes [M(L)2] (where M = Sn(II), Pb(II), and HL = semicarbazone, thiosemicarbazone or phenylthiosemicarbazone) have been prepared and characterized by elemental analysis, conductance measurements, molecular weight determinations, UV–visible, infrared, and nuclear magnetic resonance (1H-, 13C-, and 119Sn-NMR) spectral studies. Elemental analysis of the metal complexes suggested 1 : 2 (metal–ligand) stoichiometry. Infrared spectra of the complexes agree with coordination to the metal through the nitrogen of the azomethine (>C=N−) and the oxygen/sulfur of the ketonic/thiolic group. Electronic spectra suggest a distorted tetrahedral geometry for all Schiff base complexes. The bond lengths, bond angles, highest occupied molecular orbital, lowest unoccupied molecular orbital, Mulliken atomic charges, and the lowest energy model structure of the complexes have been determined with DFT calculations. Representative Schiff base and its metal chelates have been screened for their in...

Luminescent monometallic Cu(I) triphenylphosphine complexes based on methylated 5-trifluoromethyl-3-(2′-pyridyl)-1,2,4-triazole ligands

Abstract: A new family of five new mononuclear Cu(I) triphenylphosphine complexes derived from methylated 5-trifluoromethyl-3-(2′-pyridyl)-1,2,4-triazole ligands has been synthesized and well characterized. They all show an N2P2 distorted tetrahedral geometry and the methylated 5-trifluoromethyl-3-(2′-pyridyl)-1,2,4-triazole ligands display the mono-anionic η2(N1,N2) and charge-neutral η2(N1,N4) chelating coordination modes, along with the 1,2,4-triazolyl ring inversion induced by the NH ↔ N− transformation. These Cu(I) complexes are all emissive in solution and solid states at ambient temperature, which can be well modulated by changing the methyl position on the pyridyl ring and regulating the NH ↔ N− conversion of the 1,2,4-triazolyl ring. It is also shown that the deprotonation of 1,2,4-triazolyl-NH can markedly improve the luminescence properties of Cu(I) complexes.

Theoretical investigation, biological evaluation and VEGFR2 kinase studies of metal(II) complexes derived from hydrotris(methimazolyl)borate

Abstract: The reaction of soft tripodal scorpionate ligand, sodium hydrotris(methimazolyl)borate with M(ClO4)2·6H2O [MMn(II), Ni(II), Cu(II) or Zn(II)] in methanol leads to the cleavage of B-N bond followed by the formation of complexes of the type [M(MeimzH)4](ClO4)2·H2O (1-4), where MeimzH=methimazole. All the complexes were fully characterized by spectro-analytical techniques. The molecular structure of the zinc(II) complex (4) was determined by X-ray crystallography, which supports the observed deboronation reaction in the scorpionate ligand with tetrahedral geometry around zinc(II) ion. The electronic spectra of complexes suggested tetrahedral geometry for manganese(II) and nickel(II) complexes, and square-planar geometry for copper(II) complex. Frontier molecular orbital analysis (HOMO-LUMO) was carried out by B3LYP/6-31G(d) to understand the charge transfer occurring in the molecules. All the complexes exhibit significant antimicrobial activity against Gram (-ve) and Gram (+ve) bacterial as well as fungal strains, which are quite comparable to standard drugs streptomycin and clotrimazole. The copper(II) complex (3) showed excellent free radical scavenging activity against DPPH in all concentration with IC50 value of 30μg/mL, when compared to the other complexes. In the molecular docking studies, all the complexes showed hydrophobic, π-π and hydrogen bonding interactions with BSA. The cytotoxic activity of the complexes against human hepatocellular liver carcinoma (HepG2) cells was assessed by MTT assay, which showed exponential responses toward increasing concentration of complexes.

Synthesis, Structural Characterization, Theoretical Calculations and In Vitro Biological Activities of Organotin(IV) Complexes with [O,O] Donor Ligand

Abstract: The present study deals with the synthesis of ligand 4-oxo-4-(thiazol-2-ylamino)butanoic acid and afterward its organotin(IV) carboxylates [Bu3SnL] (1), [Ph3SnL] (2), [Me2SnL2] (3), [Bu2SnL2] (4) and [Ph2SnL2] (5). These complexes were characterized by useful techniques like elemental analysis, FT-IR, NMR (1H, 13C) and single crystal analysis. The ligand coordinates to tin atom via the carboxylate group. Complex 1 has also been studied by single crystal XRD analysis. It showed that tin has distorted tetrahedral geometry due to bulky butyl groups that hinder the carbonyl oxygen of the ligand interaction with the adjacent tin atom for further coordination. The HOMO–LUMO study of ligand “HL” and its tin complexes 3 and 5 indicated that tin complexes are thermodynamically more stable than the ligand. The synthesized complexes were screened for their biological activities like antibacterial, antifungal, antileishminial, cytotoxicity and protein kinase inhibition studies in vitro. Complexes 1 and 2 exhibited maximum antileishmanial activity that was even higher than that of standard Amphotericin B, with significant cytotoxicity and could be potential candidates for the treatment of leishmaniasis. The UV–visible spectroscopic studies revealed that ligand and its complexes bind with DNA via intercalative mode of interaction leading to hypochromism and minor bathochromic or hypsochromic shifts.

The multiple conformational charge states of zinc(II) coordination by 2His-2Cys oligopeptide investigated by ion mobility-mass spectrometry, density functional theory and theoretical collision cross sections.

Abstract: Whether traveling wave ion mobility-mass spectrometry (IM-MS), B3LYP/LanL2DZ density functional theory, and ion size scaled Lennard-Jones (LJ) collision cross sections (CCS) from the B3LYP optimized structures could be used to determine the type of Zn(II) coordination by the oligopeptide acetyl-His1 -Cys2 -Gly3 -Pro4 -Tyr5 -His6 -Cys7 (amb5 ) was investigated. The IM-MS analyses of a pH titration of molar equivalents of Zn(II):amb5 showed that both negatively and positively charged complexes formed and coordination of Zn(II) increased as the His and Cys deprotonated near their pKa values. The B3LYP method was used to generate a series of alternative coordination structures to compare with the experimental results. The method predicted that the single negatively charged complex coordinated Zn(II) in a distorted tetrahedral geometry via the 2His-2Cys substituent groups, whereas, the double negatively charged and positively charged complexes coordinated Zn(II) via His, carbonyl oxygens and the C-terminus. The CCS of the B3LYP complexes were calculated using the LJ method and compared with those measured by IM-MS for the various charge state complexes. The LJ method provided CCS that agreed with five of the alternative distorted tetrahedral and trigonal bipyramidal coordinations for the doubly charged complexes, but provided CCS that were 15 to 31 A2 larger than those measured by IM-MS for the singly charged complexes. Collision-induced dissociation of the Zn(II) complexes and a further pH titration study of amb5B , which included amidation of the C-terminus, suggested that the 2His-2Cys coordination was more significant than coordinations that included the C-terminus. Copyright © 2016 John Wiley & Sons, Ltd.

Synthesis, spectral, thermal, crystal structure, Hirschfeld analysis of [ bis (triamine)Cadimium(II)][Cadimum(IV)tetra-bromide] complexes and their thermolysis to CdO nanoparticles

Abstract: The coordination chemistry of cadmium(II) with diamine ligands is of particular interest. The most common structure around cadmium(II) center in their complexes is tetrahedral, that is due the octet rule obeyed. Nevertheless, five and six-coordinated complexes are also well known. Now a day, many cadmium(II) complexes with chelate ligands were synthesized for their structural or applications properties. Antibacterial activities and DNA binding affinity of this class of cadmium complexes have attracted considerable interest. Cadmium(II) complexes in dicationic form with general formula [Cd(dien)2]CdBr4 complex 1 (dien = diethylenetriamine) and [Cd(dipn)2]CdBr4 complex 2 (dipn = diproylenetriamine) were prepared and elucidated there chemical structures by elemental analysis, UV–Vis, IR, TG and NMR, additionally complex 1 structure was solved by X-ray diffraction study. The Cd(II) cation is located in a slightly distorted octahedral geometry while Cd(IV) anion is in tetrahedral geometry. High stability of the synthesized complexes confirmed by TG. Thermolysis of complex 1 revealed the formation of pure cubic nanoparticles CdO which was deduced by spectral analysis. The average size of CdO nanoparticles was found to be ~60 nm. Two new Cd(II) complexes of general formula [Cd(N3)2]CdBr4 were made available. The structure of [Cd(dien)2]CdBr4 was confirmed by X-ray diffraction. Thermal, electro and spectral analysis were also investigated in this study. The direct thermolysis of such complexes formed a cubic CdO regular spherical nanoparticle with the ~60 nm average particle size. Graphical abstract ORTEP for the complex 1

Structural evolution, electronic and magnetic manners of small rhodium Rhn+/− (n = 2–8) clusters: a detailed density functional theory study

Abstract: A systematic investigation on the lowest energy electronic structure of neutral, cationic and anionic Rhn (n = 2–8) clusters in the gas phase is performed with an all electron relativistic method using density functional theory within the generalized gradient approximation. The lowest energy structures of neutral and ionic rhodium clusters are evaluated with different multiplicities. Neutral clusters with even atoms of rhodium and ionic clusters containing odd atoms of rhodium are optimized with multiplicities M = 1, 3 and 5, while neutral clusters containing odd rhodium atoms and ionic clusters with even atoms of rhodium are allowed to relax with multiplicities M = 2, 4 and 6. The bond length, binding energy, coordination number, bond dissociation energy, stability function, ionization potential, electron affinity, electrophilicity, LUMO–HOMO gap, chemical hardness, dipole moment and magnetic moment are evaluated from the lowest energy geometry. These studies reveal that even atom rhodium clusters are more stable than odd atom clusters. Calculated electronic properties such as the LUMO–HOMO gap, bond dissociation energy, stability function, electron affinity and electrophilicity suggest that Rh4 with a tetrahedral geometry is the most stable among all Rhn (n = 2–8) clusters. Hence, tetrahedral Rh4 may be considered as the magic number cluster.

High-resolution photoelectron imaging spectroscopy of cryogenically cooled Fe4O(-) and Fe5O(.).

Abstract: We report high-resolution photodetachment spectra of the cryogenically cooled iron monoxide clusters Fe4O(-) and Fe5O(-) obtained with slow photoelectron velocity-map imaging (cryo-SEVI). Well-resolved vibrational progressions are observed in both sets of spectra, and transitions to low-lying excited states of both species are seen. In order to identify the structural isomers, electronic states, and vibrational modes that contribute to the cryo-SEVI spectra of these clusters, experimental results are compared with density functional theory calculations and Franck-Condon simulations. The main bands observed in the SEVI spectra are assigned to the (15)A2←(16)B2 photodetachment transition of Fe4O(-) and the (17)A'←(18)A″ photodetachment transition of Fe5O(-). We report electron affinities of 1.6980(3) eV for Fe4O and 1.8616(3) eV for Fe5O, although there is some uncertainty as to whether the (15)A2 state is the true ground state of Fe4O. The iron atoms have a distorted tetrahedral geometry in Fe4O(0/-) and a distorted trigonal-bipyramidal arrangement in Fe5O(0/-). For both neutral and anionic species, the oxygen atom preferably binds in a μ2-oxo configuration along the cluster edge. This finding is in contrast to prior predictions that Fe5O(0/-) exhibits a μ3 face-bound structure.

Coordination complexes of 4-methylimidazole with Zn II and Cu II in gas phase and in water: a DFT study

Abstract: A quantum chemistry study of mononuclear metal coordination with four 4-methylimidazole ligands (4-MeIm) was investigated. The four complexes [Cu(4-MeIm)4]2+, [Cu(4-MeIm)4, H2O]2+, [Zn(4-MeIm)4]2+ and [Zn(4-MeIm)4, H2O]2+ were studied with particular attention to the Nπ or Nτ possible coordinations of the 4-MeIm ring with the metals, using different DFT methods. The results suggest that the Nτ coordination of 4-MeIm ring to ZnII or CuII is more favorable whatever the level of calculation. In contrast, the addition of one water molecule in the first coordination sphere of the metal ions provides five-coordinated complexes showing no Nπ or Nτ preferences. There is good agreement between the DFT-calculated structure and those available experimentally. When metal ions are four-fold coordinated, they adopt a tetrahedral geometry. When CuII and ZnII are five-fold coordinated, highly symmetric structures or intermediate structures are calculated. Similar energies are calculated for different structures, suggesting flat potential energy surfaces. The addition of implicit solvent modifies the calculated first coordination sphere, especially for [Cu(4-MeIm)4, H2O]2+ structures. The QTAIM and ELF topological analyses of the interaction between CuII and the neutral ligands, clearly indicate a dative bonding with a strong ionic character.

Synthesis, coordination behavior and structural features of chiral iron(II) PNP diferrocene complexes

Abstract: Five new chiral PNP ferrocene ligands with either an imine or amine nitrogen coordination site were synthesized. Only the imine type ligands formed Fe(II) complexes with the general formula [Fe(PNP)X2] (X = Cl, Br). In the solid state these complexes adopt a tetrahedral geometry with the PNP ligand coordinated in a κ2P,N-fashion with the one pendant-arm and the other not coordinated, as determined by X-ray crystallography and Mossbauer spectroscopy. The complexes are paramagnetic with a quintet ground state. In solution there is an equilibrium between [Fe(κ3P,N,P-PNP)X2] and [Fe(κ2P,N-PNP)X2] complexes. Boronation of the non-coordinated arm shifts the equilibrium towards the four-coordinate complex [Fe(κ2P,N-PNPBH3)Br2]. DFT calculations are consistent with the experimental results and indicate that the experimentally observed κ2 isomer is thermodynamically the most stable. In a CO atmosphere, [Fe(PNP)(CO)2Br]Br was formed rather than [Fe(PNP)(CO)Br2].

Synthesis, characterization, and crystal structure of cobalt(II) and zinc(II) complexes with a bulky Schiff base derived from rimantadine

Abstract: Two novel complexes, C38H48CoN2O2 (I) and C38H48N2O2Zn (II), were prepared through an analogous procedure with a corresponding metal chloride and a bulky Schiff base ligand (HL) which derived from rimantadine and salicylaldehyde in appropriate solvents, respectively. They were structurally characterized by the means of IR, UV-Vis, elemental analysis, molar conductance, PXRD and single-crystal X-ray diffraction (CIF files nos. 946735 (I), 893304 (II)). Single-crystal X-ray diffraction analysis reveals that I belongs to the triclinic system, \(P\overline 1 \) space group; each asymmetric unit consists of one cobalt(II) complex and one lattice ethanol molecule. In each complex molecule, cobalt(II) atom is four-coordinated via two oxygen atoms and two nitrogen atoms from the deprotonated Schiff base ligands, forming an approximate planar geometry. The crystal structure also involves strong O–H···O intermolecular hydrogen bonds between the solvent alcoholic and phenol O atoms of complex molecule. Complex II belongs to the monoclinic system, Cc space group. Each asymmetric unit consists of one zinc(II) ion and two deprotonated ligands. Zinc(II) atom lies on a twofold rotation axis and is four-coordinated via two nitrogen atoms and two oxygen atoms from the Schiff base ligands, forming a distorted tetrahedral geometry.