Formation Of Mononuclear Complexes Research Articles

Synthesis, structural, DFT studies and antibacterial evaluation of Cp∗ rhodium and Cp∗ iridium complexes using hydrazide based dipyridyl ketone ligand

The synthesis, characterization and antibacterial evaluation of four new water soluble half-sandwich complexes of N′-{di(pyridin-2-yl)methylene}picolinohydrazide (PHADPK-L1) and N′-{di(pyridin-2-yl)methylene}nicotinohydrazide (NHADPK-L2) have been described with the general formula [Cp∗MLCl]BF4 where L=L1, M=Rh (1), Ir (2); L=L2, M=Rh (3), Ir (4) have been described. All the complexes have been characterized by elemental analysis and spectral studies. Crystal structures of all the complexes 1–4 have been determined by single crystal X-ray analyses. Preliminary in vitro antibacterial activity of the four complexes was investigated against Gram-positive bacterium Staphylococcus aureus, and Gram-negative bacteria viz., Escherichia coli, Klebsiella pneumonia and Pseuedomonas aeruginosa by agar well diffusion method. Spectral and structural studies revealed that the formation of mononuclear complexes takes place by dipyridyl mediated N–N binding. All the complexes exhibited a HOMO (highest occupied molecular orbital)–LUMO (lowest unoccupied molecular orbital) energy gap from 3.65 to 3.97eV.

Some Pb(II) complexes of 2, 6-bis (Hydroxymethyl) Pyridine with different Pb(II) Salts involving the anions chloride, Perchlorate and Nitrate. A Photoelectron spectroscopic study

Some Pb(II) complexes of 2, 6-bis(hydroxymethyl)pyridine (dhmp) with different Pb(II) salts [PbCl2.6H2O, Pb(ClO4)2.6H2O, Pb(NO3)2.3H2O] are synthesized and characterized and studied by IR, NMR and mass spectroscopy. The distortion of the coordination polyhedron, dependent on the anion kind influence on the distribution of donor sites and the formation of mononuclear complexes. There is no case the contortions of Pb(II) salt or water of hydration were found in the coordination sphere. Spectroscopy data shows that complexes are mononuclear 2: 1 (L: M) complexes. The ligand dhmp components is mono-deprotonated and act as anionic ligand. The complex number 4 show same behavior. But in 1, 2 and 4 complexes it behave as neutral ligand. The basal planes are occupied by O donors and N atoms are in the axial positions of Octahedral in 3 and 4 the basis are formed by two O and two N donor atoms, and O atoms are in the axes. Complex 3 shows the N atoms in trans position but 4 shows N atoms in cis position. Complexes (1–4) shows packing and cationic complex unit is strong and weak hydrogen bond interactions involving the contortions and hydroxyl hydrogen atoms or aromatic hydrogen atoms to stabilize the complexes.

Study of Multiporphyrin Compounds as Colorimetric Sitting-Atop Metal Complexes: Synthesis and Photophysical Studies.

Mono-, di-, tri-, and hexaporphyrin derivatives were synthesized and their sensorial ability toward Na+ , Li+ , Ca2+ , Cu2+ , Ni2+ , Co2+ , Fe3+ , Zn2+ , Cd2+ , Hg2+ , Ag+ , Cr3+ , Pb2+ , and Al3+ was explored by absorption and emission spectroscopy and 1 H NMR spectroscopy. For all of the studied porphyrin derivatives the most significant spectral changes were observed upon addition of Zn2+ , Cd2+ , Cu2+ , Co2+ , Pb2+ , Hg2+ , and Fe3+ , which resulted in a color change from red to green. When the remaining metal ions were tested, no significant changes were observed. The results reveal, as expected, the formation of mononuclear complexes for porphyrin 4, dinuclear complexes for diporphyrin 7, and trinuclear complexes for triporphyrins 9 and 10. In addition, complexes of type M6 L were determined for hexaporphyrin 8. The NMR spectroscopy studies suggest that the interaction with the metals occurs with the formation of sitting-atop complexes. This study also shows that the sensitivity increases with increasing number of coordination sites, with the most pronounced case observed for Hg2+ . The lowest value of detectable concentration of 0.05 μm for Hg2+ was achieved for hexaporphyrin 8.

New Fe(II) complexes with Schiff base ligand: Synthesis, spectral characterization, magnetic studies and thermal stability

New ligand (Z)-2-(1-methyl-2-(pyridine-2-ylmethylene)hydrazinyl)benzoxazole (L) reacts with Fe(II) ions what results in formation of mononuclear complexes of 2:1 stoichiometry (complexes 1 and 2), which crystallize in the rare space group Ia–3d (No. 230) with solvent–acetonitrile–molecules in the crystal structure. Obtained complexes were studied in terms of their properties in the solid state concerning thermal stability and magnetism. N3-donor Schiff base type L is a strong crystal field ligand, therefore both obtained Fe(II) complexes are diamagnetic at room temperature what has been confirmed by magnetic susceptibility measurements and Mössbauer spectroscopy. However, the reversible LS (1A1)↔HS (5T2) spin-transitions may be observed starting above room temperature, remaining incomplete even up to 400K. The thermal stability and electronic reflectance spectra of complexes were determined as well.

Cyclodiphosphazane appended with pyridyl functionalities: Reactivity, transition metal chemistry and structural studies

A pyridyl functionalized cyclodiphosphazane, cis-{(μ-NtBu)P(OCH2C5H4N-o)}2 (1) was synthesized by reacting pyridine-2-methanol with cis-{(μ-NtBu)PCl}2. The reactions of cis-{(μ-NtBu)P(OCH2C5H4N-o)}2 with chalcogenides in appropriate stoichiometry afforded both mono and bis-chalcogenides. The treatment of 1 with ML2Cl2 (M = Pd or Pt; L2 = COD, (SMe2)2) in 1:1 molar ratios resulted in the formation of mononuclear complexes, [MCl2{(μ-NtBu)P(OCH2C5H4N-o)}2] (8 M = Pd; 9 M = Pt), whereas the 1:2 reactions produced binuclear complexes [(MCl2)2{(μ-NtBu)P(OCH2C5H4N-o)}2] (10 M = Pd; 11 M = Pt). The reaction of 1 with [Ru(η6-p-cymene)(μ-Cl)Cl]2 afforded [((η6-p-cymene)RuCl2)2{(μ-NtBu)P(OCH2C5H4N-o)}2] (13). Reaction of [Rh(μ-Cl)(COD)]2 with 1 in a 1:2 molar ratio yielded the mononuclear complex, [{(CO)RhCl}2{(μ-NtBu)P(OCH2C5H4N-o)}2] (14), while the 1:1 reaction of [Rh(μ-Cl)(CO)2]2 with 1 produced a binuclear complex [((CO)RhCl{(μ-NtBu)P(OCH2C5H4N-o)}2] (15). The treatment of 1 with AuCl(SMe2) resulted in the formation of a binuclear complex [(AuCl)2{(μ-NtBu)P(OCH2C5H4N-o)}2] (16). The reaction of 1 with 2 equiv of CuBr gave coordination polymer [{Cu(μ-Br)}2{(μ-NtBu)P(OCH2C5H4N-o)}2]n (17). The crystal structures of 5, 8–10, 13 and 17 were established by single-crystal X-ray diffraction studies.

Mononuclear and terminal zirconium and hafnium methylidenes.

The dimethyl aryloxide complexes [(PNP)M(CH3)2(OAr)] (M=Zr or Hf; PNP(-)=N[2-P(CHMe2)2-4-methylphenyl]2); Ar=2,6-iPr2C6H3), which were readily prepared from [(PNP)M(CH3)3] by alcoholysis with HOAr, undergo photolytically induced α-hydrogen abstraction to cleanly produce complexes [(PNP)M=CH2(OAr)] with terminal methylidene ligands. These unique systems have been fully characterized, including the determination of a solid-state structure in the case of M=Zr.

Complex formation between zinc(II) and arginine in a large range of reagent concentration

Arginine and zinc(II) play an important role in the human physiology. Arginine is a precursor of NO which is a vasodilator and zinc(II) is frequently an enzyme activator having also therapeutic role. The complex formation between zinc(II) and arginine is studied, at 25 °C and in 1.00 mol dm−3 NaCl as ionic medium. The investigation is carried out potentiometrically, by employing cells involving glass and zinc amalgam electrodes, in a large range of reagent concentration. Experimental data can be explained by assuming the formation of mononuclear complexes in zinc(II), but with the participation of hydrogen ions. The formation of the following species with the relative stability constant explains the experimental data: ZnHL (log β 1,1,1 = 16.11 ± 0.07), ZnH2L2 (log β 1,2,2 = 33.41 ± 0.05), ZnH3L3 (log β 1,3,3 = 45.93), ZnH2L3 (log β 1,2,3 = 36.04), and ZnHL3(log β 1,1,3 = 27.15), where L represents the completely deprotonated arginine.

Absorption spectra, luminescence properties and electrochemical behavior of Mn(II), Fe(III) and Pt(II) complexes with quaterpyridine ligand

6,6‴-Dimethyl-2,2′;6′,2″;6″,2‴-quaterpyridine ligand L reacts with Mn(II) 1, Fe(III) 2 and Pt(II) 3, 4 ions what results in formation of mononuclear complexes. The reactions were carried out under different conditions (various solvent, temperature, counterion), leading to new complexes [MnL(H2O)Cl][ClO4], [FeLCl2][FeCl4], [PtL][Pt(CH3CN)Cl3]2 in which dimethylquaterpyridine acts as tetradentate ligand. The use of more drastic reaction conditions leds to obtain of a novel organoplatinum(II) complex [Pt(L-H)Cl], that reveal unique tridentate coordination mode C, N, N′. Obtained compounds were thoroughly studied in terms of their structural studies. We also have investigated physicochemical and electrochemical properties of these complexes.

Metal-ion induced FRET in macrocyclic dynamic tweezers

We report here about effective FRET process (73–99%) in mono-Mg2+ complexes of symmetrical crown ether bis(styryl) dyes. The FRET process has not been observed in the free state and in binuclear complexes. The formation of mononuclear complex provides two styrylic fragments with appropriate positions of absorption and emission bands for FRET. The other important parameter for FRET is the proper geometric orientation of both chromophores, which attain sandwich conformation with close positioning of complexed and free styryl fragments induced by ion-modulated geometry reorganization of the bis-dye.

Heteroditopic thiacalix[4]arene receptor having ester and bipyridyl moieties for ions binding with positive/negative allosteric effect

A novel ditopic receptor possessing two complexation sites and bearing 1,3-alternate conformation based thiacalix[4]arene was prepared. The binding behaviors with Na+, K+ and Ag+ ions have been examined by 1H NMR titration experiment in (CDCl3/CD3CN; 10:1, v/v) solution. The job plots proves 1:1 complexation of 1,3-alternate-4 with Na+, K+ and Ag+ ions. Although the formation of heterogeneous dinuclear complexes was not clearly observed, the exclusive formation of mononuclear complexes of 1,3-alternate-4 with metal cations is of particular interest with positive/negative allosteric effect in thiacalix[4]arene family. These findings further demonstrate that preorganization, suitable conformational changes and affinity have a pronounced effect on the complexation process between the two different arms placed at the two edges of the thiacalix[4]arene cavity.

Cd(II) complexes with pendant armed oxa- and azamacrocyclic ligands

The coordination capability of the pendant-arm macrocyclic ligands – with different sizes, nature and number of the donor atoms – dioxotriaza 17-membered (L1) and pentaaza 17-membered (L2) towards nitrate and perchlorate Cd(II) salts, has been investigated. The complexes were prepared in 1:1 metal/ligand molar ratio. The characterization carried out by elemental analysis, FAB mass spectrometry, IR and NMR spectroscopy, conductivity measurements, together with the crystal structure of the complexes [CdL1(CH3CN)](ClO4)2·CH3CN and [CdL2](ClO4)2 confirms the formation of mononuclear complexes in all cases. The X-ray diffraction of [CdL1(CH3CN)](ClO4)2·CH3CN complex presents a mononuclear endomacrocyclic structure with the metal ion coordinated by the five donor atoms from the macrocyclic framework, the amine group from the pendant-arm and one acetonitrile molecule, in a distorted pentagonal bipyramid geometry. The complex [CdL2](ClO4)2 is also mononuclear, but the cadmium ion is in a distorted trigonal prism environment coordinated by the six nitrogen donor atoms from the ligand. In both cases, the perchlorate ions do not participate in the coordination to the metal ion, but they are involved in numerous hydrogen bond interactions inter- and intramolecular with phenoxy and amino-groups.

Spectral and Structural Studies of Platinum Group Metal Complexes of3‐(Di‐2‐Pyridylaminomethyl)Benzamide and Formation of Mutual Intermolecular Hydrogen Bonding in Some Complexes

AbstractThe new ligand, 3‐(di‐2‐pyridylaminomethyl)benzamide, L, which carries two different coordination sites, i.e. the primary amide moiety on one side and a di‐2‐pyridylamine unit as a strong chelating group on the other side is synthesized. Reaction of chloro‐bridged dimers viz., [(η6‐arene)Ru(μ‐Cl)Cl]2 and [Cp*M(μ‐Cl)Cl]2 with two equivalents of the ligand L in methanol followed by the addition of NH4BF4 results the formation of mononuclear complexes of the formulation [(η6‐arene)Ru(L)Cl]BF4 [arene = C6H6 (1), C10H14 (2), C6Me6 (3)] and [Cp*M(L)Cl]BF4 [M = Rh (4); Ir (5)]. All these complexes are characterized by micro analyses, IR, and 1H NMR spectroscopic analyses and finally by single crystal XRD study of some representative complexes. Complexes 3 and 5 show mutual intermolecular hydrogen bonding by amide–amide interactions.

Effect of humic acid on nickel(ii) sorption to Ca-montmorillonite by batch and EXAFS techniques study

The influence of humic acid (HA) on Ni(II) sorption to Ca-montmorillonite was examined by using a combination of batch sorption experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy technique. The sorption of Ni(II) on HA-montmorillonite hybrids is strongly dependent on pH and temperature. At low pH, the sorption of Ni(II) is mainly dominated by Ni-HA-montmorillonite and outer-sphere surface complexation. The EXAFS results indicate that the first coordination shell of Ni(II) consists of ∼6 O atoms at the interatomic distances of ∼2.04 Å in an octahedral structure. At high pH, binary Ni-montmorillonite surface complexation is the dominant sorption mechanism. EXAFS analysis indicates the formation of mononuclear complexes located at the edges of Ca-montmorillonite platelets at pH 7.5, while a Ni-Al layered double hydroxide (LDH) phase at the Ca-montmorillonite surface formed with pH 8.5. At pH 10.0, the dissolved HA-Ni(II) complexation inhibits the precipitation of Ni hydroxide, and Ni-Al LDH phase forms. The rise of temperature increases the sorption capacity of Ni(II), and promotes Ni-Al LDH phase formation and the growth of crystallites. The results are important to evaluate the physicochemical behavior of Ni(II) in the natural environment.

Synthesis and structural characterization of diorganotin dithiocarbamates from 4‐(ethylaminomethyl)pyridine

AbstractThree 4‐(ethylaminodithiocarbamate) methylpyridine diorganotin derivatives were prepared using a one‐pot synthetic procedure from 4‐(ethylaminomethyl)pyridine, carbon disulfide, KOH as a base, and the corresponding diorganotin dichloride (R = Me, nBu, Ph). All three compounds were successfully characterized in solution (1H, 13C, and 119Sn NMR) as well as in the solid state (IR, mass spectrometry, and X‐ray diffraction). In all three cases, an anisobidentate coordination mode was observed for the dithiocarbamate moiety to the tin atom, evidenced mainly by the different SnS bond distances obtained from the X‐ray diffraction analysis. The organic groups attached to the tin atom have no influence on the reaction course, leading in each case to the formation of mononuclear complexes with the metal center in a hexacoordinated environment. Interestingly, in the solid state the methyl‐tin derivative showed Pyċn and SċSn intermolecular interactions, which were not observed in the two other complexes. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:422–428, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.21032

Versatile Schiff-base hydrazone fluorescent receptors: Synthesis, spectroscopy and complexation studies

A family of emissive acyclic ligands (1–4) and their Cu2+ and Zn2+ metal complexes has been synthesized and characterised by microanalysis, IR, MALDI mass spectrometry, UV–Vis and fluorescence emission. For comparative purposes, the coordination ability of all chemosensors (1–4) towards the same metal ions was explored in solution (with the help of the UV–Vis and emission spectroscopy) and in gas phase (by MALDI mass spectrometry). The formation of mononuclear complexes with two or three units of ligands was observed during the entire process.

Synthesis, characterization and crystal structure of some bidentate heterocyclic Schiff base ligands of 4-toluoyl pyrazolones and its mononuclear Cu(II) complexes

We depict the synthesis of a new set of six bidentate heterocyclic Schiff base ligands, formed by the condensation of three different 4-toluoyl pyrazolones with various aromatic amines in ethanolic medium. All of these ligands have been characterized on the basis of elemental analysis, IR, 1H NMR, 13C NMR and Mass spectral data. The molecular geometries of three of these ligands have been determined by single crystal X-ray study. It reveals that these ligands exist in amine-one tautomeric form in the solid state. The reaction of these ligands with copper(II) resulted in the formation of mononuclear complexes having the general composition [CuL 2(H 2O) 2] with two water molecules at axial positions. These complexes have been characterized on the basis of elemental analysis, Cu-estimation, molar conductivity, magnetic measurements, IR, UV–Visible, FAB–Mass, TG–DTA–DSC data, cyclic voltametric measurements and ESR spectral studies. ESR spectra and magnetic susceptibility measurements indicates distorted octahedral stereochemistry of Cu(II) complexes, while non-electrolytic behaviour of complexes indicates the absence of counter ion.

Rare Earth Metal Complexes Supported by Ancillary Imidazolin‐2‐iminato Ligands

AbstractThe coordination chemistry of imidazolin‐2‐iminato ligands towards rare earth metal atoms is reviewed. The structural characterization of a large number of mono‐, bis‐ and tris(imidazolin‐2‐iminato) complexes – in most cases scandium, yttrium, gadolinium, and lutetium complexes – reveals almost exclusively the formation of mononuclear complexes with very short metal–nitrogen bonds, which confirms the ability of imidazolin‐2‐iminato ligands to efficiently act as imido‐type 2σ,4π‐electron donors. In particular, mono(imidazolin‐2‐iminato) metal dichlorides proved to be excellent starting materials for the introduction of alkyl, amido, cyclopentadienyl, cyclooctatetraenyl, and carboranyl ligands and also for the preparation of efficient pre‐catalysts for ring‐opening, hydroamination and hydrosilylation reactions, which allow to establish imidazolin‐2‐iminato ligands as novel valuable members of the growing family of ancillary ligands in organo rare earth metal and organolanthanide chemistry. In addition, the coordination chemistry of several imidazolin‐2‐imine‐hybrid ligands such as cyclopentadienyl‐imine and pincer‐type diimine ligands is described, and the structural characterization of the resulting complexes indicates that also neutral imidazolin‐2‐imines act as strong amido‐type donor ligands towards rare earth metal ions.

Synthesis, Spectral and Thermal Studies of New Rutin Vanadyl Complexes

Complexes between oxovanadium (IV) cation and flavonoid derivatives were developed recently in order to increase the intestinal absorption and to reduce the toxicity of vanadium compounds. For these reasons, is interesting to investigate the complexation process between flavonoid rutin (Rut) and vanadyl cation in order to isolate new complexes. Two new complexes [VO(Rut)(H2O)2](SO4)0.5 2H2O and [VO(Rut)2] 4H2O have been obtained and characterized by elemental and thermal analyses and several spectroscopic techniques (ESI-MS, IR, UV-Vis, fluorescence). The studies concerning complex formation between vanadyl and rutin (Rut) performed in different solutions show the formation of mononuclear complexes with 1:1 and 1:2 metal to ligand stoichiometry.

Uranium Uptake by Hectorite and Montmorillonite: A Solution Chemistry and Polarized EXAFS Study

The mechanism of U(VI) retention on montmorillonite and hectorite at high ionic strength (0.5 M NaCl) was investigated by solution chemistry and, at near-neutral pH, polarized EXAFS spectroscopy. Uranium(VI) sorption increases from pH 3 to 7 on the two clays, but with a steeper edge for hectorite. Uranium(VI) is no longer retained at pH > 9, presumably owing to the formation of soluble anionic complexes. Polarized EXAFS showed that U(VI) retains its uranyl conformation on montmorillonite (U_mont) and hectorite (U_hect), with uranyl O at 1.79(2) A for U_mont and 1.82(2) A for U_hect, and split equatorial O shells at 2.29(2) and 2.47(2) A (U_mont), or 2.35(2) and 2.53(2) A (U_hect). An additional atomic shell of approximately 0.5 Al/Si at 3.3 A is detected for U_mont, but neither the oxygen nor the cationic shell exhibit clear angular dependence. These results indicate the formation of mononuclear complexes at the edges of montmorillonite platelets, with the orientation of the uranyl axis equal to the magic angle, as constrained by the edges' structural properties. In contrast to U_mont, the U-O signal varies with the polarization angle in U_hect, and the cationic Mg/Si contribution at 3.2 A is weak. The structure of this surface complex is not completely elucidated; it may correspond either to sorption on silanol sites, or to coprecipitation. These results lay out the fundamental molecular-scale basis to understand U retention by neoformed clay layers of nuclear glasses.

First solid state alkaline-earth complexes of monensic acid A (MonH): crystal structure of [M(Mon)2(H2O)2] (M = Mg, Ca), spectral properties and cytotoxicity against aerobic Gram-positive bacteria

Alkaline-earth metal complexes of the monoanionic form of the polyether ionophore monensin A were isolated for the first time in solid state and were structurally characterized using various spectroscopic methods (IR, NMR, FAB-MS). The stoichiometric reaction of monensic acid (MonH) with M(2+) (M = Mg, Ca) in the presence of an organic base leads to the formation of mononuclear complexes of composition [M(Mon)(2)(H(2)O)(2)]. The structures of magnesium (1) and calcium (2) monensin complexes in the solid state were established by single crystal X-ray crystallography. The complexes crystallize as [Mg(Mon)(2)(H(2)O)(2)]x5MeCN (1) and [Ca(Mon)(2)(H(2)O)(2)]xH(2)Ox5MeCN (2) in the monoclinic P21 space group. The alkaline-earth metal ion is placed in a distorted octahedral environment, defined by two monensin anions acting as bidentate ligands in the equatorial plane of the complex as well as by two water molecules occupying the axial positions of the inner coordination sphere. The bactericidal activity of 1 and 2 was evaluated against aerobic Gram-positive microorganisms applying the double layer agar hole diffusion method.