Anionic Bidentate Research Articles

Binuclear Coordination Assemblies of Metal Tetraphenylporphyrins (M = Mn, Fe, and In) with Anionic Thioindigo Bridges as Promising Magnetic Systems with Tunable Properties.

A series of hybrids comprising two metal (Mn, Fe, and In) tetraphenylporphyrins axially substituted with anionic bidentate trans-thioindigo ligands (TI) were obtained. Substitution of the axial chloride anion by an oxygen atom of the dye forms short M-O bonds. Crystalline binuclear assemblies (TI•-)·{[MnIITPP]0·[MnIIITPP]+}·xC6H4Cl2 (x = 2 for 1 or 1 for 2) and (TI2-){[MIIITPP]+}2·xC6H4Cl2 (M = Fe and x = 2 for 3, M = In and x = 1 for 4) were synthesized. The thioindigo (TI2-) dianion and metal (FeIII and InIII) atoms in TPPs maintain their initial charge states during the formation of 3 and 4, allowing the separation of paramagnetic FeIII or diamagnetic InIII ions by a diamagnetic TI2- bridge. Strong antiferromagnetic coupling is observed between FeIII (S = 5/2) centers in complex 3. Partial reduction of MnIII to MnII occurs upon the formation of 1 and 2, leading to assemblies containing three paramagnetic centers: MnII (S = 5/2), MnIII (S = 2), and TI•- radical anion (S = 1/2). Orthogonal arrangement of TPP and TI molecules in 1 provides strong ferromagnetic coupling. Weak antiferromagnetic coupling is realized in 2 due to the rotation of the TI bridge.

Tricarbonyl rhenium(i) complexes with 8-hydroxyquinolines: structural, chemical, antibacterial, and anticancer characteristics.

Twelve tricarbonyl rhenium(i) complexes in the '2 + 1' system with the anionic bidentate N,O-donor ligand (deprotonated 8-hydroxyquinoline (HQ) or its 2-methyl (MeHQ) or 5-chloro (ClHQ) derivative) and neutral N-donor diazoles (imidazole (Him), 2-methylimidazole (MeHim), 3,5-dimethylpyrazole (Hdmpz), and 3-phenylpyrazole (HPhpz)) were synthesized: [Re(CO)3(LN,O)LN] (LN,O = Q-, MeQ-, ClQ-; LN = Him, MeHim, Hdmpz, HPhpz). Their crystal structures were determined by the scXRD method, compared with the DFT-calculated ones, and characterized by analytical (EA) and spectroscopic techniques (FT-IR, NMR, and UV-Vis) interpreted with DFT and TD-DFT calculations. Most of the Re(i) complexes did not show relevant antibacterial activity against Gram-negative and Gram-positive bacterial strains. Only [Re(CO)3(MeQ)Him] demonstrated significant action 4-fold better against Gram-negative Pseudomonas aeruginosa than the free MeHQ ligand. The cytotoxicity of the compounds was estimated using human acute promyelocytic leukemia (HL-60), ovarian (SKOV-3), prostate (PC-3), and breast (MCF-7) cancer, and breast non-cancerous (MCF-10A) cell lines. Only HQ and ClHQ ligands and [Re(CO)3(Q)Hdmpz] complex had good selectivity toward MCF-7 cell line. HL-60 cells were sensitive to all complexes (IC50 = 1.5-14 μM). Still, pure HQ and ClHQ ligands were slightly more active than the complexes.

Cobalt(II), nickel(II), palladium(II) and zinc(II) metallothiosemicarbazones: Synthesis, characterization, X-ray structures and biological activity

Metal(II) complexes of the type [Co(S-HL)2Cl2] and [Ni(N,S-L)2], [Pd(N,S-L)2], [Zn(N,S-L)2], were synthesized from the reaction of HL with metal(II) chlorides. All complexes were characterized by spectroscopic methods, such as elemental analysis, FT-IR, 1H NMR, and single crystal X-ray diffraction. In the [Co(S-HL)2Cl2] complex, the cobalt atom adopts a distorted tetrahedral geometry around the cobalt(II) ion, with two neutral monodentate S-thiosemicarbazone ligands coordinating via one of the thiocarbonyl sulfur atom and two chlorides. In the [Ni(N,S-L)2] and [Pd(N,S-L)2] complexes, HL ligand is coordinated with the metal center, as a mono anionic bidentate N,S donors which are in trans position and that metal(II) ions adopt square planar coordination. [Zn(N,S-L)2] indicates that the anionic thiosemicarbazone ligands bind to the metal in a distorted tetrahedral arrangement with N,S donor atoms. The antimicrobial activity of the ligand and metal(II) complexes were studied against bacterial strains and fungal stain. It was observed that the ligand showed weaker activity than the metal complexes. The Zn(II) complex had the best antibacterial activity against E. faecalis, while the Co(II) complex showed the best activity against S. aureus bacteria. Co(II) and Pd(II) complexes were relatively more effective against Gram-negative bacteria. It was determined that metal complexes were less effective against gram negative bacteria compared to gram positive bacteria. A little antifungal activity was observed in Zn(II) and Co(II) complexes.

Synthesis, characterization, crystal structure, Hirshfeld surface analysis and DFT of 1,2-benzothiazine metal (II) complexes

In the present study, the mononuclear complexes of oxicam precursor with Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) metal ions have been prepared. The UV/Vis, FT-IR, 1H NMR spectroscopies, elemental analysis and magnetic susceptibility measurements were used to confirm successful synthesis of transition metal complexes. The square planar coordination geometry of the Cu(II) complex 5 was confirmed by XRD analysis. The spectroscopic data indicated that two mono anionic bidentate ligands act as chelating agents and attached with metal center via enolate oxygen and carbonyl oxygen of the ester group present in 1,2-benzothiazine. The molar conductance indicated the non-ionic nature of the Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes. The octahedral geometry is proposed for the Mn(II), Co(II) and Zn(II) complexes, respectively and square planar geometry for Ni(II) and Cu(II) complexes is proposed on the basis of obtained data. The reported basis sets with ligand and its Cu(II) complex were used to conduct DFT studies. The synthesis of the targeted compounds was also confirmed by energy gap calculations between HOMO and LUMO. The Hirshfeld surface analysis of the copper complex was carried and 2D contacts were drawn. Furthermore, COX-I and COX-II inhibition studies for the targeted compounds were carried out by applying molecular docking study. The docking results revealed that these molecules have potential to inhibit the cyclooxygenases and may reduce the inflammation in the body.

Spectral, crystallographic, theoretical, and catalytic activity studies of the PdII complexes in different coordination modes of benzoylthiourea ligand

Syntheses of neutral monodentate dichloro bis[N‐(diethylcarbamothioyl)‐4‐fluorobenzamido-κS] palladium(II), [PdIICl2(LH-κS)2] and anionic bidentate bis[N‐(diethylcarbamothioyl)‐4‐fluorobenzamido-κ2O,S] palladium(II), [PdII(L-κ2S,O)2] complexes of N‐(diethylcarbamothioyl)‐4‐fluorobenzamide (LH) ligand is reported. While [PdIICl2(LH-κS)2] was obtained by reaction between PdCl2 and LH in acetonitrile solution as a single crystal form, [PdII(L-κ2S,O)2] was formed recrystallization of [PdIICl2(LH-κS)2] in dichloromethane: ethanol solvent mixture as powder form. The PdII complexes were characterized by elemental analysis, FT-IR, 1H NMR, and 13C NMR spectral measurements. Furthermore, the molecular structure of [PdIICl2(LH-κS)2] was defined by single crystal X-ray diffraction, and the result obtained was also confirmed by spectral data. The optimized molecular geometry of the ligand and [PdIICl2(LH-κS)2] complex was obtained by density functional theory calculation at the B3LYP/6-311G(d,p) and LanL2DZ level of theory, respectively. We found that the optimized geometrical parameters agree very well with the experimental one. Therefore, we used the same theoretical level (B3LYP/LanL2DZ) for the [PdII(L-κ2S,O)2] which is a powder form, not a single crystal form. The energies of frontier molecular orbitals (EHOMO and ELUMO), energy band gap, and quantum molecular descriptors of the prepared compounds were calculated. Information about the site of chemical reactivity, charge density distribution, the size, and shape of the molecules was obtained by mapping with molecular electrostatic potential (MEP). NBO analysis was applied for the investigation of intra and inter-molecular bonding and conjugative interaction in molecular systems. The Mulliken and natural population analyses were used to predict positive and negative charges on every atom in the molecules. Hirshfeld surface analysis and 2D fingerprint plots were applied to visualize and quantify intermolecular interactions and packing modes in the supramolecular structure. The Coulomb interaction, dispersion, and total energy calculations were used to visualize and analyze the three-dimensional figures of the crystal lattice. Furthermore, the catalytic efficiencies of both palladium complexes have been confirmed in the Suzuki-Miyaura C-C reaction using a very low 0.01 mol% catalyst loading.

Spectroscopic Insight into Tetrahedrally Distorted Square Planar Copper(II) Complex: XRD/HSA, Physicochemical, DFT, and Thermal Investigations

The reaction of bidentate N-S-thione-Schiff base, (E)-benzyl 2-(1-(4-chlorophenyl)-ethylidene)hydrazinecarbodithioate, with Cu(NO3)2·3H2O produced a cis-Cu(II) complex. The molecular structure was confirmed and characterized by CHN-EA, FAB-MS, IR, and UV-Vis analyses. The XRD supported cis-isomer of the bis anionic bidentate N (azomethine) and S (thiol) ligand coordination mode in tetrahedrally distorted square planar, rarely reported in the literature. The results of the XRD-bond lengths were in perfect agreement with the density functional theory (DFT) calculation. DFT-calculated angles around the Cu(II) center displayed slightly less distortion around the metal center from those of XRD. Additionally, the thermal stability of the complex was evaluated via thermal gravimetric analysis (TGA). Two-dimensional fingerprint (2D-FP), Hirshfeld surface analysis (HSA), and molecular electrostatic potential (MEP) support the XRD-packing results with the existence of the H⸱⸱⸱Cl and CH⸱⸱⸱π bonds as the main interactions in the crystal lattice of the desired complex.

Palladium complexes derived from benzoylthiourea ligands: Synthesis, crystal structure, and catalytic application in Suzuki C–C coupling reactions

Abstract[PdCl2(HL1‐κS)2] and [PdCl2(HL2‐κS)2] complexes were formed from neutral monodentate modes of HL1 and HL2 ligands, which are coordinated to the palladium(II) center, respectively. [Pd(L1‐κ2S,O)2] and [Pd(L2‐κ2S,O)2] complexes were obtained by recrystallization of corresponding [PdCl2(HL1‐κS)2] and [PdCl2(HL2‐κS)2] complexes as anionic bidentate coordination modes. All palladium(II) complexes were characterized by elemental analysis, FT‐IR, and NMR (1H and 13C) techniques. The molecular structure of [Pd(L1‐κ2S,O)2] and [Pd(L2‐κ2S,O)2] was also confirmed by single‐crystal X‐ray diffraction method. The roles and behaviors of the prepared four palladium(II) complexes in catalytic investigations for the Suzuki C–C coupling reaction were examined for the first time. The complexes acted as the excellent catalyst precursor and showed highly catalytic activity for the Suzuki C–C coupling reaction of various arylhalides with phenylboronic acid at low catalyst loading (0.01 mol%).

IRMPD spectroscopy and quantum chemistry calculations on mono- and bi-metallic complexes of acetylacetonate ligands with aluminum, iron, and ruthenium ions.

Metal-ligand cluster ions are structurally characterized by means of gas-phase infrared multiple photon dissociation spectroscopy. The mass-selected complexes consist of one or two metal cations M3+ (M = Al, Fe, or Ru) and two to five anionic bidentate acetylacetonate ligands. Experimental IR spectra are compared with different density functional theory calculations, namely, PBE/TZVP, B3LYP/6-31G*, and M06/6-31+G**. Frequency analysis was also performed at different levels, namely, scaled static harmonic and unscaled static anharmonic, or with ab initio molecular dynamics simulations at the PBE/TZVP level. All methods lead to simulated spectra that fit rather well with experimental data, and the spectral red shifts of several main bands, in the 1200 cm-1-1800 cm-1 range, are sensitive to the strength of the metal-ligand interaction and to the spin state of the ion. Due to the rigidity of those complexes, first principles molecular dynamics calculations provide spectra similar to that produced by static calculations that are already able to catch the main spectral signatures using harmonic calculations at the B3LYP/6-31G* level.

STRUCTURE OF LANTHANIDE SEMIQUINOLATES WITH NITROGEN-CONTAINING LIGANDS

Molecular and crystal structures are determined for a series of mixed-ligand mononuclear compounds of lanthanides (Ln) with the 3,6-di(tert-butyl)-1,2-benzoquinone (SQ) anion radical and bidentate nitrogen-containing ligands (L) of the composition [Ln(SQ)3(L)], where Ln is Tb or Dy, L is 2,2′-bipyridine (bipy); Ln is Eu, L is 1,10-phenanthroline (phen) or N,N,N′,N′-tetramethylethylenediamine (tmen). It is confirmed that the introduction of bidentate L significantly increases the stability of lanthanide semiquinolates in both liquid and solid phases.

Subtle variation of stereo-electronic effects in rhodium(I) carbonyl Schiff base complexes and their iodomethane oxidative addition kinetics

Rhodium(I) carbonyl complexes of the form [RhI(N,O-ScBa)(CO)(PR3)] (R = Ph or Cy), with N,O-ScBaH a mono anionic bidentate Schiff base ligand, 2-(cyclopentyliminomethyl)-5-methylphenol (5-Me-Sal-CyPH), and bearing different phosphine ligands on Rh(I), are reported. N,O-ScBaH was also varied to be 2-(cyclohexyliminomethyl)phenol (Sal-CyH) and 2-(isopropyliminomethyl)-5-methylphenol (5-Me-Sal-IPropH) to investigate the effects of different substituent groups on the periphery of the Schiff bases on metal center reactivity. The structural characterization of two sample complexes is described and an extensive spectroscopic kinetic-mechanistic study utilizing UV/vis, infrared and 31P NMR spectroscopy of the iodomethane oxidative addition is presented. Iodomethane oxidative addition led exclusively to RhIII-alkyl complexes as final products, while an associative activation is inferred from the large negative ΔS ≠ value. The relative reactivity of the [RhI(N,O-ScBa)(CO)(PR3)] complexes when stepwise varying PR3 (PPh3, PPh2Cy, PPhCy2 and PCy3) as tertiary phosphine ligands follow a surprising similar reactivity relationship as observed for a range of isostructural [RhI(X,O-Bid)(CO)(PR3)] complexes, with X = O, N or S in corresponding oxinate, acetylacetonate and thioureate mono anionic X,O-Bid ligands. This suggests systematic and responsive dynamic behavior of the PR3 ligands, independent of the bidentate chelate at the Rh(I) metal center. A variation of more than two orders-of-magnitude in reactivity was observed.

Synthesis, Crystal Structures and Anticancer Studies of Morpholinyldithiocarbamato Cu(II) and Zn(II) Complexes.

Cu(II) and Zn(II) morpholinyldithiocarbamato complexes, formulated as [Cu(MphDTC)2] and [Zn(μ-MphDTC)2(MphDTC)2], where MphDTC is morpholinyldithiocarbamate were synthesized and characterized by elemental analysis, spectroscopic techniques and single-crystal X-ray crystallography. The molecular structure of the Cu(II) complex revealed a mononuclear compound in which the Cu(II) ion was bonded to two morpholinyl dithiocarbamate ligands to form a four-coordinate distorted square planar geometry. The molecular structure of the Zn(II) complex was revealed to be dinuclear, and each metal ion was bonded to two morpholinyl dithiocarbamate bidentate anions, one acting as chelating ligand, the other as a bridge between the two Zn(II) ions. The anticancer activity of the morpholinyldithiocarbamate ligand, Cu(II) and Zn(II) complexes were evaluated against renal (TK10), melanoma (UACC62) and breast (MCF7) cancer cells by a Sulforhodamine B (SRB) assay. Morpholinyldithiocarbamate was more active than the standard drug parthenolide against renal and breast cancer cell lines, and [Zn(μ-MphDTC)2(MphDTC)2] was the most active complex against breast cancer. The copper(II) complex had a comparable activity with the standard against renal and breast cancer cell lines but showed an enhanced potency against melanoma when compared to parthenolide.

Ru(II) complexes containing (2-(pyren-1-ylmethylene)hydrazinyl)benzothiazole: Synthesis, solid-state structure, computational study and catalysis in N-alkylation reactions

Reactions of (2-(pyren-1-ylmethylene)hydrazinyl)benzothiazole (L) with ruthenium(II) prefabricated precursors [RuHCl(CO)(EPh3)3] and [RuH2(CO)(EPh3)3] (E = P or As) afforded new Ru(II) complexes [RuCl(CO)(EPh3)2(L)] and [RuH(CO)(EPh3)2(L)] (E = P or As) (1–4). All the Ru(II) complexes (1–4) were characterized by IR, NMR spectroscopies, ESI-mass spectrometry and elemental analyses. The solid-state structures of Ru(II) complexes (2 and 3) were established by single crystal X-ray analyses and revealed distorted octahedral geometries around the ruthenium(II) ion and mono anionic bidentate N^N coordination mode for hydrazine ligand. The Ru(II) complexes 2 and 3 were also analyzed using Hirshfeld surface analysis and DFT calculations. Moreover, all the complexes (1–4) were utilized in the N-alkylation reactions of amines using alcohol. Complex 3 was found to be highly active towards N-alkylation of different aromatic amines with alcohol.

Hydrogen Bond Enhanced Halogen Bonds: A Synergistic Interaction in Chemistry and Biochemistry.

The halogen bond (XB) has become an important tool for molecular design in all areas of chemistry, including crystal and materials engineering and medicinal chemistry. Its similarity to the hydrogen bond (HB) makes the relationship between these interactions complex, at times competing against and other times orthogonal to each other. Recently, our two laboratories have independently reported and characterized a synergistic relationship, in which the XB is enhanced through direct intramolecular HBing to the electron-rich belt of the halogen. In one study, intramolecular HBing from an amine polarizes the iodopyridinium XB donors of a bidentate anion receptor. The resulting HB enhanced XB (or HBeXB) preorganizes and further augments the XB donors. Consequently, the affinity of the receptor for halogen anions was significantly increased. In a parallel study, a meta-chlorotyrosine was engineered into T4 lysozyme, resulting in a HBeXB that increased the thermal stability and activity of the enzyme at elevated temperatures. The crystal structure showed that the chlorine of the noncanonical amino acid formed a XB to the protein backbone, which augmented the HB of the wild-type enzyme. Calorimetric analysis resulted in an enthalpic contribution of this Cl-XB to the stability of the protein that was an order of magnitude greater than previously determined in biomolecules. Quantum mechanical (QM) calculations showed that rotating the hydroxyl group of the tyrosine to point toward rather than away from the halogen greatly increased its potential to serve as a XB donor, equivalent to what was observed experimentally. In sum, the two systems described here show that the HBeXB concept extends the range of interaction energies and geometries to be significantly greater than that of the XB alone. Additionally, surveys of structural databases indicate that the components for this interaction are already present in many existing molecular systems. The confluence of the independent studies from our two laboratories demonstrates the reach of the HBeXB across both chemistry and biochemistry and that intentional engineering of this enhanced interaction will extend the applications of XBs beyond these two initial examples.

New Five Coordinate Ru(II) Carbonyl Complexes Containing 2‐Aminofluorene Schiff Base Derivatives: Synthesis, Structure and Catalytic Activity

AbstractThe monometallic five coordinated ruthenium(II) Schiff base complexes of the general type [Ru(CO)(EPh3)2(L1−3)]Cl (E=P or As) have been synthesized and characterized by analytical and spectral (FT−IR, UV−Vis and 1H NMR) methods. The electronic spectra of the complexes indicate the presence of intense MLCT transitions in the visible region. The molecular structure of the complex [Ru(CO)(PPh3)2(L3)]Cl 5 was characterized by single crystal X−ray diffraction studies, which revealed that the Schiff base ligands coordinated to the ruthenium(II) ion as mono anionic bidentate (O, N) donor forming six membered chelating rings. Further, the five coordinate [Ru(CO)(PPh3)2(L3)]Cl 5 complex was found efficiently to catalyze the formation of amides from various substituted aldehyde and showing higher catalytic activity in the presence of NH2OH.HCl and NaHCO3 and the yield was up to 97%.

Cyclometalated Ru(II)‐NHC Complexes as Effective Catalysts for Transfer Hydrogenation: Influence of Wingtip Group on Catalytic Outcome

AbstractCyclometalated N‐heterocyclic carbene (NHC) based ruthenium benzene complexes of general formula [(η6‐C6H6)Ru(C C)Cl] (C C=1‐butyl‐3‐phenylimidazol‐2‐ylidene 1 a, 1‐isopropyl‐3‐phenylimidazol‐2‐ylidene 1 b and 1‐benzyl‐3‐phenylimidazol‐2‐ylidene 1 c) have been synthesised via C−H activation of 1‐alkyl‐3‐phenylimidazolium salts with [(η6‐C6H6)RuCl2]2 under silver transmetallation condition. All the complexes have been characterized by elemental analysis and spectral methods. The solid‐state structures of the complexes 2 a‐c have been established by a X‐ray single crystal diffraction study which revealed that NHC ligands behaved as mono anionic bidentate C C donors to the Ru(II) center via carbenic carbon and cyclometalated carbon. The newly synthesised ruthenium(II) NHC complexes 2 a‐c have been exploited as potential homogeneous catalysts to the transfer hydrogenation reactions for a broad scope of ketones to alcohols using 2‐propanol as a hydrogen source. The titled complexes worked well with low catalyst loading of 0.2 mol% with maximum conversion of 100% under optimized condition with reference to base, temperature, time, catalyst loading and substrate scope. Besides, the influence of the nature of wingtip group of the NHC ligands on the transfer hydrogenation reaction has also been reported to demonstrate the efficacy of catalyst.

Structural and catalytic properties of some azo-rhodanine Ruthenium(III) complexes

Novel azo-rhodanine ruthenium(III) complexes of the type trans-[Ru(Ln)2(AsPh3)2]Cl (Ln = monobasic bidentate anions of 5-(4′-methoxyphenylazo)-3-phenylamino-2-thioxothiazolidin-4-one (HL1), 5-(phenylazo)-3-phenylamino-2-thioxothiazolidin-4-one (HL2) and 5-(4′-chlorophenylazo)-3-phenylamino-2-thioxothiazolidin-4-one (HL3); AsPh3 = triphenylarsine) have been synthesized and characterized by elemental analysis, spectroscopic (IR, 1H NMR and UV–VIS), magnetic, X-ray diffraction, mass spectra and thermal analysis techniques. These techniques confirm the formation of octahedral ruthenium(III) complexes. The Ru(III) complexes were tested as a catalysts for the oxidation of benzyl alcohol to benzaldehyde with N-methylmorpholine-N-oxide as a co-oxidant. The effect of time, temperature, and solvent were also studied and the mechanism of this catalytic oxidation reaction is suggested. Molecular docking was used to predict the binding between azo rhodanine derivatives (HLn) with the receptor of 3qum- immune system receptor of human prostate specific antigen (PSA) in a Fab sandwich with a high affinity and a PCa selective antibody.

Influence of anions on the adsorption of uranyl on hydroxylated α-SiO2(001): A first-principles study

The adsorption of uranyl on hydroxylated α-SiO2(001) in the presence of a series of anionic ligands, i.e. OH−, CO32-, NO3-, H2PO4-, HPO42-, CH3COO− (Ac−), C6H5COO− (PhCO2-), C6H5O− (PhO−), was studied by the periodic density functional theory (DFT) implemented in the Vienna ab initio simulation package (VASP). For the ligands other than OH− and PhO−, only the bidentate coordination modes to the uranyl were considered. The excess charge effect of a charged system was first evaluated by constructing models with net charge as is or neutralized by creating defect at the bottom of silica, and the results show that a neutralized model, even with defects, is more realistic than the charged ones. All uranyl species prefer to bind with the deprotonated site (O−) rather than the protonated one (OH), which suggests that the increase of pH, which leads to the deprotonation of the surface, may enhance the uranyl adsorption. On the other hand, the anionic ligands, which are formed at higher pH, have negative effects. The weaker acidic ligands, such as H2CO3, H3PO4 and H2O, whose speciation in solutions is sensitive to the fluctuation of pH, have more complex effect on the uranyl adsorption than strong acids or bases. Humic substances may coordinate with uranyl through carboxyl and phenolic groups, with the carboxyl group bound stronger. The ternary complexes with one bidentate (or monodentate) anion and one (or two) H2O as ligands, which leads to the uranyl penta-coordinated in its equatorial plane, are more favorable than other configurations when bound to the same anionic ligand. Both the charged nature and the coordination behavior of an anionic ligand are relevant to its ability to influence the adsorption of uranyl on the mineral surface. In addition, the uranyl species adsorbed at the surface functionalized by anionic ligands were also addressed, and the functionalized surfaces have weaker interaction with hydrated uranyl dication.

Tropolone as anionic and neutral ligand in lead(II) and bismuth(III) complexes: Synthesis, structure, characterization and computational studies

Two new metal complexes, [Bi(trop)2(Htrop)(CF3SO3)] (1) and [Pb(trop)2(Htrop)] (2), have been synthesized by reaction of the respective metal triflates with an excess of tropolone (Htrop) in the concentrated methanol or dimethylsulfoxide solution. In addition, it was found that complex 1 crystallizes through the formation of unstable intermediate methanol solvated tris(tropolonato)bismuth(III) compound. The characteristic behavior of tropolone which coordinates both as the bidentate anion (trop−) and the monodentate neutral molecule (Htrop) has been revealed in 1 and 2. The crystal structures of studied compounds have been determined by single-crystal X-ray diffraction. The molecular structures of both complexes have been compared with their geometries received from DFT calculations giving a good correlation. The presented compounds show coordination number of metal ion equal to five in 2 and six in 1 and the presence of stereochemically active 6s2 lone electron pair. The complexes were characterized by FT-IR, NMR and UV–Vis techniques. IR and UV–Vis spectra of 1 and 2 were also simulated by DFT methods. TD-DFT predictions demonstrate the frontier HOMOs and LUMOs cover in the major part the tropolonate and(or) tropolone moieties which gives mainly ligand-to-ligand charge transfer (LLCT) and ligand centered (LC) character to the energy bands above 300 nm.

Zwitterionic nickel(II) complexes: Synthesis, characterization, decomposition, and stoichiometric and catalytic reactivities

Zwitterionic nickel(II) compounds with a borate-containing anionic bidentate phosphine ligand (PBP−) have been synthesized and some of them crystallographically characterized. The methyl complex, (PBP−)Ni+CH3(NCCH3), reacts with H2 to form an 12-membered macrocycle containing three Ni nuclei and reacts with carbon monoxide (CO) to afford the acetyl complex (PBP−)Ni+COCH3(CO). The square planar acetyl complex is stable in solution under 1 atm of CO but undergoes irreversible decomposition under high CO pressure at room temperature. X-Ray crystallographic characterization of a decomposition product revealed fragmentation of the anionic borate under high pressure. (PBP−)Ni+COCH3(CO) is an active catalyst for ethylene-CO copolymerization, but its productivity is low likely due to its instability under high CO pressure.

The influence of cations on lithium ion coordination and transport in ionic liquid electrolytes: a MD simulation study.

The dynamical and structural properties in two ionic liquid electrolytes (ILEs) based on 1-ethyl-3-methylimidazolium bis-(trifluoromethanesulfonyl)-imide ([emim][TFSI]) and N-methyl-N-propylpyrrolidinium bis-(trifluoromethanesulfonyl)imide([pyr13][TFSI]) were compared as a function of lithium bis-(trifluoromethanesulfonyl)-imide (LiTFSI) salt concentrations using atomistic molecular dynamics (MD) simulations. The many-body polarizable APPLE&P force field has been utilized. The influence of anion polarization on the structure of the first coordination shell of Li(+) was examined. In particular, the reduction of the oxygen of the TFSI anion (OTFSI) polarizability from 1.36 Å(3) to 1.00 Å(3) resulted in an increased fraction of the TFSI anion bidentate coordination to the Li(+). While the overall dynamics in [pyr13][TFSI]-based ILEs was slower than in [emim][TFSI]-based ILEs, the exchange of TFSI anions in and out of the first coordination shell of Li(+) was found to be faster in pyr13-based systems. The Li(+) ion transference number is higher for these systems as well. These trends can be related to the difference in interaction of TFSI with the IL cation which is stronger for pyr13 than for emim.