Bidentate Coordination Mode Research Articles

Crystal structure of two new polymeric copper(II) complexes active against Trypanosoma cruzi

We report here the characterization of two new polymeric copper(II) complexes containing 2-chlorobenzhydrazide (2-CH) and two N,N-donor ligands, namely, 1,10-phenanthroline (phen) and 4-4′-dimethoxy-2-2′-bipyridine (dmb). The structure of a new polymeric copper(II) complex in which a perchlorate anion acts as a bridge ligand is discussed in detail. In both complexes, spectral data reveals a bidentate coordination mode for hydrazide, perchlorate and N,N-donor ligand. These metal complexes and their free ligands were evaluated for their trypanocidal and cytotoxic activities and the complex with 1,10-phenanthroline has been much more active than benznidazole, a drug used in the treatment of Chagas disease.

Organotin Carboxylates based on 3‐(1,3‐Dioxo‐2,3‐dihydro‐1H‐phenalen‐2‐yl)benzoic Acid and the Influence of Solvent on the Molecular Structure

Self‐assembly of dibutyltin oxide with 3‐(1,3‐dioxo‐2,3‐dihydro‐1H‐phenalen‐2‐yl)benzoic acid (HL) produces (nBu)2SnL2 (1) when benzene is used as solvent, whereas the reaction generates {[(nBu)2SnO]2L}2·C7H8 (2) when toluene is the reactive solvent. The novel organotin carboxylate (nBu)2SnL2 (1) was characterized by elemental analysis, as well as IR, 1H, 13C, and 119Sn NMR spectroscopy. Single crystal X‐ray study reveals that 1 is a dialkyltin carboxylate monomer possessing crystallographically imposed twofold symmetry. Ligand HL in 1 chelates with tin atom in bidentate coordination mode. The molecules of 1 build complicate 1D, 2D, and 3D structures via intermolecular hydrogen bonds, and π···π interactions can be found in the 3D architecture. The preliminary fluorescence activity and antitumor activity of the complex were also studied.

Construction of nine non-covalently-bonded zinc(II) and cadmium(II) supramolecules containing the mixed-ligands of 3,5-dimethylpyrazole and carboxylates: Their synthesis and characterization

The present report pertains to the synthesis and characterization of nine novel mixed-ligand complexes, Zn(Hdmpz)2(L1)2 (1) (Hdmpz = 3,5-dimethylpyrazole, L1 = 2-furoate), Cd(Hdmpz)4(L2)2 (2) (L2 = 1-hydroxy-2-naphthoate), Zn(Hdmpz)2(L3)2 (3) (L3 = 5-bromosalicylate), Cd(Hdmpz)2(L4) (4) (L4 = 4-nitro-phthalate), Zn(Hdmpz)2(L5)2 (5) (L5 = 3-(2-chloro-phenylcarbamoyl)-acrylate), Zn(Hdmpz)2(L6)2 (6) (L6 = 3-m-tolylcarbamoyl-acrylate), Cd(Hdmpz)2(L6)2 (7), Zn(Hdmpz)2(L7)2 (8) (L7 = 3-p-tolylcarbamoyl-acrylate) and [Cd(Hdmpz)2(L7)2]2·2H2O (9). The resulting complexes were formulated from elemental analysis, IR spectra and single crystal X-ray diffraction analysis. The TGA of all the complexes was also evaluated.The X-ray studies revealed that these complexes display mononuclear to binuclear structures with a tetrahedral geometry around each Zn atom and an octahedral geometry around each Cd atom. The Hdmpz ligands in all the compounds are coordinated only in a monodentate fashion through its neutral N atom. The carboxylate ligands in 1, 2, 3, 5, 6 and 8 act only as unidentate coordination ligands, while the carboxylate ligands in 4 and 7 have a chelating bidentate coordination mode. Compound 9 contains both unidentate bridging and chelating bidentate coordinated carboxylate groups.The uncoordinated O atom of the COO− group in 1, 2 and 3 forms an intramolecular hydrogen bond with the N–H group of the Hdmpz, compound, 4 bears an intramolecular N–H⋯O hydrogen bond between the pyrazole ligand and the coordinated O atom. In 5, 6, 7 and 8, there are intramolecular N–H⋯O hydrogen bonds from the N–H unit of the Hdmpz ligand and the O atom of the CONH group. In 9, the N–H⋯O hydrogen bonds from the –H unit of the Hdmpz ligand, the O atom of the CONH group and the coordinated O atom of the COO− group were found. In addition, in the compound 9 there exists an intra-anion N–H⋯O hydrogen bond between the coordinated O atom and the CONH unit, displaying a S11(7) ring.The intricate intra- and intermolecular classical hydrogen bonds, Br–Br, CH3–Br, CH–N, C–H⋯O, CH3⋯O, O⋯π(C), Cl–π, C–H⋯Cπ, C–H⋯π, CH3–π and π–π associations are elucidated from the X-ray crystallographic studies, which turn the discrete complexes into high-dimensional ordered supramolecular structures.

Synthesis and characterization of p-xylylenediaminium bis(nitrate). Effects of the coordination modes of nitrate groups on their structural and vibrational properties

The p-xylylenediaminium bis(nitrate) compound have been synthesized and then, it was characterized by using Fourier Transform infrared (FT-IR) in the solid phase and, by using the Ultraviolet–Visible (UV–Visible) and Hydrogen and Carbon Nuclear Magnetic Resonance (1H- and 13C-NMR) spectra in aqueous solution and in dimethylsulfoxide solvent. In this work, two monodentate and bidentate coordination modes were considered for the nitrate ligands in both media in order to study the structural and vibrational properties of that salt. Hence, the natural bond orbital (NBO), atoms in molecules (AIM), Merz-Kollman (MK) charges, molecular electrostatic potentials (MEP) and frontier orbitals studies were performed for p-xylylenediaminium bis(nitrate) and their cation and anion species taking into account for the salt those two coordination modes for the nitrate ligands. The intermolecular interactions of this salt were also evaluated by Hirshfeld surface analysis. The B3LYP calculations performed by using the hybrid method and the 6-311G* and 6-311++G** basis sets generate monodentate and bidentate structures with Ci and C2 symmetries, respectively. The force fields and the force constants values for these two structures were also computed and their complete vibrational assignments were performed by using those both levels of theory. The strong band at 1536 cm−1, the bands between 2754 and 2547 cm−1 and the bands between 1779 and 1704 cm−1 support clearly the presence of the dimeric species while the IR bands at 1986/1856 cm−1 could justify the presence of the bidentate species in the solid phase.

New coordination modes of iminodiacetamide type ligands in palladium(II) complexes: crystallographic and DFT studies

The reactions of N-alkyliminodiacetamide derivatives, namely N-ethyliminodiacetamide (CH3CH2N(CH2CONH2)2; Etimda) and N-isopropyliminodiacetamide (CH3)2CHN(CH2CONH2)2; i-Primda), with sodium tetrachloropalladate(II) in aqueous solutions were investigated. Three new palladium(II) complexes, [Pd(Etimda−H)2]∙2H2O (1), [Pd(i-Primda−H)2]∙2H2O (2) and [PdCl2(i-Primda)] (3), were obtained and characterized by X-ray structural analysis, infrared spectroscopy and thermal analysis (TGA). The square planar coordination environments around the palladium(II) ions in complexes 1 and 2 consist of two N,N′-bidentate N-alkyliminodiacetamidato ligands, with imino N atoms in trans-position. The complex 3 also exhibits a square planar coordination environment around Pd(II), but with two chloride ions and one neutral N-isopropyliminodiacetamide ligand bound in an N,O′-bidentate coordination mode. The described coordination modes, as well as the presence of deprotonated amide groups in ligands in 1 and 2, are found for the first time in palladium(II) complexes with iminodiacetamide type ligands. The molecular geometries and infrared spectra of these three complexes were also modelled using DFT calculations, at the BP86-D3/def2-TZVPP/PCM level of theory. The RMSD values suggest a good agreement of the calculated and experimental geometries. A QTAIM analysis suggests a qualitative correlation between bond lengths and energy densities, also supported by an NBO analysis. The dimer interaction energy between complex units was estimated at about −15 kcal/mol for all complexes.

Synthesis of whey peptide-iron complexes: Influence of using different iron precursor compounds

Iron-binding peptides are an alternative for increasing the bioavailability of iron and to decreasing its pro-oxidant effect. This study aimed to synthesize and characterize peptide-iron complexes using FeCl2 or FeSO4 as the iron precursor compounds. Whey protein isolate (WPI), WPI hydrolyzed with pancreatin, and its fractions obtained via ultrafiltration (cut-off 5kDa) were used as ligands. The fluorescence intensity of the ligands significantly decreased as the iron concentration increased as a result of metal coordination with the iron-binding sites, which may have led to changes in the microenvironment of tryptophan. For both iron precursor compounds, the primary iron-binding site was carboxylate groups, and the linkage occurred via a bidentate coordination mode with two vibrational modes assigned to the COOFe linkage. However, infrared spectroscopy and thermal analysis results showed that the dynamics of the interaction is different for the iron precursor. The iron source may be of great importance because it may impact iron absorption and the pro-oxidant effect of the mineral.

Structural Phase Transitions and Dielectric Switching in a Series of Organic-Inorganic Hybrid Perovskites ABX3 (X=ClO4- or BF4- ).

A series of organic-inorganic hybrid perovskites ABX3 (A=diprotonated 1,4-diazabicyclo[2.2.2]octane or piperazine; B=Na+ or K+ ; X=ClO4- or BF4- ) has been synthesized. They feature a cubic cage-like host-guest structures of which A is the cationic guest residing in the anionic cage B8 X12 , B is the vertex of the cage with variable coordination numbers between six and twelve, and X is the bridging ligand with mono- and/or bidentate coordination modes. The extended Goldschmidt tolerance factor t is used to describe the phase stability of the compounds. Differential scanning calorimetry, variable-temperature structural analyses, and dielectric measurements reveal that order-disorder transitions of the A guest and/or X bridging ligand are supposed to be responsible for structural phase transitions and dielectric switching in the compounds.

Synthesis, characterization, cytotoxicity and computational studies of new phosphine‐ and carbodithioate‐based palladium(II) complexes

In quest of new metallo‐pharmaceuticals with enhanced anticancer activity, four new phosphine‐ and carbodithioate‐based Pd(II) complexes of the type [(R)CS2Pd(PR3)Cl] (where R = 4‐(2‐hydroxyethyl)piperazine (1, 2), dibenzyl (3, 4); PR3 = diphenyl(p‐tolyl)phosphine (1, 3), tris(4‐tolyl)phosphine (2, 4)) were synthesized and characterized using elemental analysis, Fourier transform infrared and NMR (1H, 13C and 31P) spectroscopies and single‐crystal X‐ray diffraction. The X‐ray diffraction data confirmed the pseudo square‐planar geometry ensuring bidentate coordination mode of carbodithioate ligands. Anticancer activity of the synthesized complexes and their ligands was assessed against human lung (A549), breast (MCF‐7) and prostate (PC3) carcinoma cells using MTT assay. All the tested compounds showed activity in micromolar range. In many cases, the cytotoxicity of the synthesized complexes was higher than or comparable to that of the standard drugs cisplatin and doxorubicin. Complex 3 emerged as the most promising compound with the lowest IC50 values of 4.83, 3.72 and 5.11 μM for A549, MCF‐7 and PC3 carcinoma cell lines, respectively. DNA binding studies were also carried out using UV–visible spectroscopy. We extended our investigations to explore the mechanism of anticancer activity using in silico tools. Based on the mechanism of action of standard drugs used, extensive docking studies were carried out on the three different biomolecular targets.

Synthesis, crystal structure, and luminescent properties of two coordination polymers based on 1,4-phenylenediacetic acid

Two coordination polymers, [Zn(pda)(bib)]n (1) and [Cd(pda)0.5(bib)Cl]n (2)]. (H2pda = 1,4-phenylenediacetic acid, bib = 1,2-bis(imidazol-1-ylmethyl)benzene), have been synthesized by using Zn(II)/Cd(II) salts with two flexible ligands pda and bib under hydrothermal conditions. Their structures have been characterized by elemental analysis, IR spectroscopy, single-crystal X-ray crystallography and powder X-ray diffraction (PXRD) analysis. Due to the coordination geometry around the metal ions and the diverse coordination modes of the flexible ligands, the obtained complex show diverse structures. In the structure of 1, a pair of bib ligands connect two Zn(II) atoms give rise a 22-membered ring, which is further extended by pda ligands in bidentate coordination mode leading a ring-containing 2D layer. In 2, bib ligands join [Cd2Cl2]2+ dimmers generate 1D polymeric ribbon, the pda ligands further extend such ribbon forming a 2D layer network containing rectangular windows, which discovers the effect of the central metal ions on the formation of metal–organic frameworks. In additional, luminescent properties of two complexes have also been studied, they could be potential fluorescence materials.

Elaborated molecular docking and DFT/B3LYP studies for novel sulfa drug complexes, spectral and antitumor investigations

A new series of drug complexes from sulfa was prepared using Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Pt(II) ions. The isolated complexes are deliberately illustrated using spectral, thermal and different theoretical tools. The bidentate mode of coordination is proposed with all complexes. The octahedral configuration is the main structural formula proposed except d8 systems. Significant parameters derived from spectra were deducted to assert on the proposed configurations. XRD and TEM tools display a great conformity in-between for proposing the nano-crystallite sizes of all investigated compounds. Implementing Gaussian 09 program for structural formulas used to obtain the optimized forms. Applying DFT/B3LYP method, the frontier energy gaps were calculated and other important theoretical parameters. Utilizing molecular docking by AutoDock tools used to explain the experimental behavior of organic compounds toward the microorganisms from theoretical visualization. The docked complexes for 4ynu, 4d7h, 1zap, 1ecl, 3e5a, 1y0k and 1bqb protein receptors were investigated and the different energies were calculated. Pt(II), Zn(II) and Cu(II) complexes display significant inhibition for all microorganisms used in biological investigation. Moreover, the IC50 calculated represent the distinguish priority of Ni(II) and Co(II) complexes in overcoming liver cancer.

Developing P-Stereogenic, Planar–Chiral P-Alkene Ligands: Monodentate, Bidentate, and Double Agostic Coordination Modes on Ru(II)

10-Phenyl-5H-dibenz[b,f]azepine (5) is synthesized by Suzuki cross coupling of the protected bromo alkene 4 with PhB(OH)2. 5 reacts with PCl3 to afford the dichlorophosphanyl-azepine 6 in >90% yield. Alkylation of 6 with 1 equiv of t-BuMgBr leads, after recrystallization in Et2O, to the diastereomerically enriched (dr > 98:2) chloride rac-7, which the crystal structure reveals to be the (pS,RP)/(pR,SP) pair. The fact that rac-7 crystallizes in the Sohncke space group P212121 opens up the possibility of a mechanical separation of the enantiomers. Methylation of rac-7 is perfectly stereoselective with inversion of configuration at the P atom to yield the new ligand rac-8 as the (R,R)/(S,S) pair. The corresponding BH3-protected diastereomer rac-9 (i.e., the (R,S)/(S,R) pair), is isolated after flash column chromatography in 73% yield. Compounds 5–9 are accessible in multigram quantities. X-ray crystal structures of Ru(II) complexes demonstrate the ambidentate nature of ligand rac-8: Complex 10 is exclusively P-coordinated, while in complex 11 two ligands bind Ru through their P donors and stabilize the 14-electron metal center with a double agostic interaction. In complex 12, the ligand coordinates in a κP,η2-alkene bidentate fashion.

A Combined Spectroscopic/Molecular Dynamic Study for Investigating a Methyl-Carboxylated PEI as a Potential Uranium Decorporation Agent.

Natural uranium has a very limited radioactive dose impact, but its chemical toxicity due to chronic exposure is still a matter of debate. Once inside the human body, the soluble uranium, under its uranyl form (U(VI)), is quickly removed from the blood system, partially excreted from the body, and partially retained in targeted organs, that is, the kidneys and bone matrix essentially. It is then crucial to remove or prevent the incorporation of uranium in these organs to limit the long-term chronic exposure. A lot of small chelating agents such as aminocarboxylates, catecholamides, and hydroxypyridonates have been developed so far. However, they suffer from poor selectivity and targeting abilities. Macromolecules and polymers are known to present a passive accumulation (size related), that is, the so-called enhanced permeability and retention effect, toward the main organs, which can be used as indirect targeting. Very interestingly, the methyl carboxylated polyethylenimine (PEI-MC) derivative has been described as a potent sequestering agent for heavy metals. It would be therefore an interesting candidate to evaluate as a new class of decorporation agents with passive targeting capabilities matching uranium preferential sequestering sites. In the present work, we explored the ability of a highly functionalized (89% rate) PEI-MC to uptake U(VI) close to physiological pH using a combination of analytical and spectroscopic techniques (inductively coupled plasma optical emission spectrometry (ICP-OES); extended X-ray absorption fine structure (EXAFS); and Fourier transformed infrared (FT-IR)) together with molecular dynamics (MD) simulation. A maximum loading of 0.47 mg U(VI) per milligram of PEI-MC was determined by ICP-OES measurements. From FT-IR data, a majority of monodentate coordination of the carboxylate functions of the PEI-MC seems to occur. From EXAFS and MD, a mix of mono and bidentate coordination mode was observed. Note that agreement between the EXAFS metrical parameters and MD radial distribution functions is remarkable. To the best of our knowledge, this is the first comprehensive structural study of a macromolecular PEI-based agent considered for uranium decorporation purposes.

Zwitterionic amidinates as effective ligands for platinum nanoparticle hydrogenation catalysts.

Ligand control of metal nanoparticles (MNPs) is rapidly gaining importance as ligands can stabilize the MNPs and regulate their catalytic properties. Herein we report the first example of Pt NPs ligated by imidazolium-amidinate ligands that bind strongly through the amidinate anion to the platinum surface atoms. The binding was established by 15N NMR spectroscopy, a precedent for nitrogen ligands on MNPs, and XPS. Both monodentate and bidentate coordination modes were found. DFT showed a high bonding energy of up to -48 kcal mol-1 for bidentate bonding to two adjacent metal atoms, which decreased to -28 ± 4 kcal mol-1 for monodentate bonding in the absence of impediments by other ligands. While the surface is densely covered with ligands, both IR and 13C MAS NMR spectra proved the adsorption of CO on the surface and thus the availability of sites for catalysis. A particle size dependent Knight shift was observed in the 13C MAS NMR spectra for the atoms that coordinate to the surface, but for small particles, ∼1.2 nm, it almost vanished, as theory for MNPs predicts; this had not been experimentally verified before. The Pt NPs were found to be catalysts for the hydrogenation of ketones and a notable ligand effect was observed in the hydrogenation of electron-poor carbonyl groups. The catalytic activity is influenced by remote electron donor/acceptor groups introduced in the aryl-N-substituents of the amidinates; p-anisyl groups on the ligand gave catalysts several times faster the ligand containing p-chlorophenyl groups.

Syntheses and photoluminescence properties of new Zn(II) and Cd(II) coordination polymers prepared from 5-sulfoisophthalate ligand

New coordination polymers, formulated as {[Zn($\mu $-sipH)($\mu $-apim)]$\cdot $3H$_{2}$O} $_{n}$ (1) and {[Cd($\mu $-sip)(H$_{2}$O)$_{2}$ (apimH)]$\cdot $3H$_{2}$O}$_{n}$ (2) were synthesized based on the 1-(3-aminopropyl)imidazole (apim) along with 5-sulfoisophthalate (sip) ligands. The complexes were synthesized under mild hydrothermal conditions. All the complexes were characterized by elemental analysis, FT-IR spectroscopy, and single-crystal X-ray diffraction studies. The X-ray crystallographic studies of 1 and 2 reveal Zn(II) and Cd(II) ions are $\mu $-bridged by dianionic sipH and trianionic sip ligands in bis(monodentate) and bis(bidentate) coordination mode, respectively, to generate 1D polymer chains. In complex 1, the adjacent chains are linked by two apim ligands to form a 1D nanotubular structure. Complex 2 is the first example of a protonated apimH ligand. In the complexes the adjacent 1D chains extend into a 3D supramolecular network by hydrogen bonds. The thermal decomposition behavior and photoluminescent property of the complexes are also discussed herein.

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.

Synthesis and structural characterization of tris(pyrazolyl)hydroaluminate and tris(pyrazolyl)hydrogallate lithium compounds

The tris(pyrazolyl)hydroaluminate derivatives, [HAlTpBut,Me]Li and {[HAlTpMe2]Li}2, have been synthesized via the reactions of LiAlH4 with 3-tert-butyl-5-methylpyrazole and 3,5-dimethylpyrazole, respectively, while the tris(pyrazolyl)hydrogallate counterparts, [HGaTpBut,Me]Li and {[HGaTpMe2]Li}2, are obtained from the corresponding reactions with LiGaH4. X-ray diffraction studies demonstrate that the 3-tert-butyl-5-methylpyrazolyl derivatives, [HAlTpBut,Me]Li and [HGaTpBut,Me]Li, are monomeric with lithium in a trigonal pyramidal coordination environment, whereas the less sterically demanding 3,5-dimethylpyrazolyl derivatives, {[HAlTpMe2]Li}2 and {[HGaTpMe2]Li}2, are dimeric. In addition to the tris(pyrazolyl)hydroaluminate derivative, [HAlTpBut,Me]Li, the tetrakis derivative, [(pzBut,Me)AlTpBut,Me]Li, has also been isolated. X-ray diffraction studies demonstrate that [(pzBut,Me)AlTpBut,Me]Li, as obtained from solutions in benzene, exists as a monomer in the solid state with tridentate coordination, whereas crystals obtained from THF exhibit a bidentate coordination mode, which is supplemented by coordination of THF, i.e.[(pzBut,Me)2AlBpBut,Me]Li(THF). NMR spectroscopic studies, however, indicate that [(pzBut,Me)AlTpBut,Me]Li is fluxional in both benzene and THF solutions.

Coordination geometry determination of stannane compounds with phosphinoyldithioformate ligands using multinuclear NMR, Sn Mössbauer and DFT methods

A series of tin(IV) phosphinoyldithioformate compounds were prepared from metathesis reaction of [R2P(O)CS2]- anion and aliphatic organotin: R′nSnX4-n (R = Ph, Bz; R′ = Me, Et; X = Cl, Br). The compounds are formulated as [SnR′2X{S2CP(O)R2}] (1), [SnR′2{S2CP(O)R2}2] (2), and [SnR′3{S2CP(O)R2}] (3). Structural analysis using a combination of IR, UV and multinuclear NMR (1H, 13C, 31P and 119Sn) spectroscopy showed the ligand prefers S,O bidentate coordination mode in these series for (1), and (2), while monodentate coordination is preferred by (3). Geometries of compounds were determined using 119Sn and 13C NMR coupling constants. The spectroscopic data is consistent with (S,O)-bidentate coordination of the ligands in (1) and (2) in solution, while a monodentate coordination through sulfur is observed in (3). Mössbauer measurements confirmed formal oxidation state of Sn, and shows comparable isomer shifts and quadrupole splitting for compounds (2) and (3) in the solid state. DFT structure optimizations and vibrational frequency calculations were performed for all compounds. The optimized structures and computed shifts of PO and CS vibrations are in excellent agreement with the conclusions of the spectroscopic structural analysis.

Experimental investigations of thermal stability of some morpholinecarbamic acid complexes of copper(II) and zinc(II)

Some new carbamates, viz. M(MorphcbmH)2X2 (MorphcbmH = morpholinecarbamic acid, M = Cu, X = Cl, ClO4,NO3; M = Zn, X = Cl, ClO4, NO3, CH3COO and X2 = SO4), have been synthesized and investigated. Compounds were characterized by elemental analysis, molar conductance, FT infrared, fluorescence, NMR (1H and 13C) and solution electronic absorption spectral studies. Room temperature field-dependent magnetic susceptibility measurements, PXRD spectral and cyclic voltametric studies were also conducted. Chelating bidentate mode of coordination of ligand, MorphcbmH with four coordination around metal ion has been proposed. Ligand and its compounds have also been studied using non-isothermal thermogravimetric analysis and differential scanning calorimetric analytical techniques which inferred formation of metal oxide/MCO3 as final thermal decomposition products. Compounds were screened against the lipase enzyme for assaying their enzyme activity and were found to retard the lipase activity from 48.16 to 0.044 µmol mL−1 min−1.

Comparative Structural Analysis of Biarylphosphine Ligands in Arylpalladium Bromide and Malonate Complexes

The substitution of biarylphosphine ligands was shown to have a marked impact on the α/β selectivity of the arylation of ester enolates. To get further insight into this effect, the solid-state structures of arylpalladium bromide and malonate complexes with four different biarylphosphine ligands were obtained by X-ray diffraction analysis. Structural differences were not very pronounced except for the conformationally restricted CPhos ligand, which showed a bidentate coordination mode in the oxidative addition complex, whereas the other ligands form dimeric species.

Vibrational analysis and crystal structure of two new 1D CuII and CoII coordination polymers, involving the ligands 2,5-dihydroxyterephthalate and glutarate

Aiming to obtain metal-organic frameworks with high dimensionality, two new 1D coordination polymers with the general formula {[Co(DHT)(DMF)2(H2O)2]n} (1) and {[Cu(GLU)(DMF)]n} (2) have been obtained, where DHT=2,5-dihydroxyterephthalate; GLU=Glutarate; and DMF=Dimethylformamide. Both coordination compounds involve simple chain formations in which the carboxylate groups from ligands adopt monodentate (for 1) and bidentate (for 2) coordination modes to the metal center. In this work, both polymers synthesized contain solvent molecules coordinated to metal centers, which represent potential open metal sites to allow postsynthetic modifications that may increase the dimensionality of the systems. The dinuclear group formation of type tetrakis (acetate) dicopper complexes, in the case of polymer (2), is worth mentioning. This unit may be categorized as a secondary building unit (SBU) like a paddlewheel formed in situ. Herein, Raman spectroscopy had an important role in its characterization. So, besides X-ray diffraction by single crystals, vibrational spectroscopy had been employed to reinforce the coordination modes analysis, especially through a good approximation of antisymmetric and symmetric shifts of vibrational modes from the carboxylate group of ligands (in comparison to the ionic form of the free ligand). Finally, we propose the removal of solvents coordinated to metal centers by activation for increasing the system dimensionality.