Bidentate Coordination Mode Research Articles

Vitamin B9 derivatives as carriers of bioactive cations for musculoskeletal regeneration applications: Synthesis, characterization and biological evaluation.

The development of new drugs for musculoskeletal regeneration purposes has attracted much attention in the last decades. In this work, we present three novel vitamin B9 (folic acid)-derivatives bearing divalent cations (ZnFO, MgFO and MnFO), providing their synthesis mechanism and physicochemical characterization. In addition, a strong emphasis has been placed on evaluating their biological properties (along with our previously reported SrFO) using human mesenchymal stem cells (hMSC). In all the cases, pure folate derivatives (MFOs) with a bidentate coordination mode between the metal and the folate anion, and a 1:1 stoichiometry, were obtained in high yields. A non-cytotoxic dose of all the MFOs (50μg/mL) was demonstrated to modulate by their own the mRNA profiles towards osteogenic-like or fibrocartilaginous-like phenotypes in basal conditions. Moreover, ZnFO increased the alkaline phosphatase activity in basal conditions, while both ZnFO and MnFO increased the matrix mineralization degree in osteoinductive conditions. Thus, we have demonstrated the bioactivity of these novel compounds and the suitability to further studied them invivo for musculoskeletal regeneration applications.

Catalytically active nanosized Pd9Te4 (telluropalladinite) and PdTe (kotulskite) alloys: first precursor-architecture controlled synthesis using palladium complexes of organotellurium compounds as single source precursors.

Several intermetallic binary phases of Pd–Te including Pd3Te2, PdTe, PdTe2, Pd9Te4, Pd3Te, Pd2Te, Pd20Te7, Pd8Te3, Pd7Te2, Pd7Te3, Pd4Te and Pd17Te4 are known, and negligible work (except few studies on PdTe) has been done on exploring applications of such phases and their fabrication at nanoscale. Hence, Pd(ii) complexes Pd(L1)Cl2 and Pd(L2-H)Cl (L1): Ph–Te–CH2–CH2–NH2 and L2: HO–2-C6H4–CH Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N–CH2CH2–Te–Ph were synthesized. Under similar thermolytic conditions, complex Pd(L1)Cl2 with bidentate coordination mode of ligand provided nanostructures of Pd9Te4 (telluropalladinite) whereas Pd(L2-H)Cl with tridentate coordination mode of ligand yielded PdTe (kotulskite). Bimetallic alloy nanostructures possess high catalytic potential for Suzuki coupling of aryl chlorides, and reduction of 4-nitrophenol. They are also recyclable upto six reaction cycles in Suzuki coupling.

Fluorescent palladium(II) and platinum(II) NHC/1,2,3-triazole complexes: antiproliferative activity and selectivity against cancer cells.

Fluorescent Pd(ii) and Pt(ii) complexes bearing 4-methylene-7-methoxycoumarin (MMC) and 2,6-diispropylphenyl (Dipp) substituted NHC/1,2,3-triazole hybrid ligands are described. Depending on the reaction conditions two different ligand coordination modes are observed, i.e., bidentate solely coordinating via NHCs or tetradentate coordinating via NHCs and 1,2,3-triazoles. All Dipp substituted complexes show antiproliferative activity against cervix (HeLa) and breast (MCF-7) human carcinoma cells. The activity significantly depends on the coordination mode, with the tetradentate motif being notably more effective (HeLa: IC50 = 3.9 μM to 4.7 μM; MCF-7: IC50 = 2.07 μM to 2.35 μM). Amongst the MMC series, only the Pd(ii) complex featuring the bidentate coordination mode is active against HeLa (IC50 = 6.1 μM). In contrast to its structurally related Dipp derivative (SI = 0.6), it shows a high selectivity for HeLa (SI > 16) compared to healthy skin cells (HaCaT). According to fluorescence microscopy, this compound is presumably located in late endosomes or lysosomes.

Construction of five non-covalent-fabricated Zn2+/Cd2+ supramolecules from 3,5-dimethylpyrazole: Their synthesis and features

The present report pertains to the synthesis and characterization of 5 novel complexes of Zn2(Hdmpz)4(L1)2(1) (L1 = itaconate), Cd(Hdmpz)2(L2) (2) (L2 = isophthalate), Cd(Hdmpz)2(L3) (3) (L3 = 5-amino-isophthalate), Zn(Hdmpz)2(L4)2(4) (L4 = 3-(4‑bromo-phenylcarbamoyl)-acrylate) and [Cd(Hdmpz)2(L4)2]2 • 2H2O (5). These complexes were elaborated from EA, IR and SCXRD analysis and the TGA of all the complexes was also identified.The X-ray studies told that these complexes display mononuclear to dinuclear structures with tetrahedral/octahedral arrangement around each Zn2+/Cd2+. The Hdmpzs in 1–5 are ligated only in monodentate fashion via its neutral N. The CO2− at 1 and 4 exhibits only unidentate coordination fashion, the CO2− in 2 and 3 show the chelating bidentate coordination mode. Compound 5 bear both unidentate bridging and bidentate chelating CO2−.The uncoordinated O of the CO2− in 1 makes the intramolecular NH•••O H-bond with NH of the Hdmpz. Compounds 2 and 3 bear the interchain NH•••O H-bonds from the Hdmpz and the coordinated O. The NH of one pyrazole at 4 made a bifurcated NH•••O H-bond with both O at the CONH and the uncoordinated O of the CO2−, the NH of the other pyrazole gave a single NH•••O H-bond to the CONH. At 5 the NH•••O H-bonds from the NH of the Hdmpz, the O at the CONH and the coordinated O of the CO2− were found. In the anions of 5 there also created the intramolecular NH•••O H-bond between the coordinated O and the CONH, building a S11(7) ring. The intricate intra- and intermolecular classical H-bonds, Br•••O, CHCH, CH3Cπ, CH-Br, CH•••O/CH2•••O/CH3•••O, CH•••π/CH2-π and CH3-π associations are elucidated by the X-ray crystallographic studies, which adhere the discrete units into high-dimensional ordered supramolecular structures.

New pyrazole‐4‐carbothioamide‐based metal complexes: Synthesis, spectral characterization, computational, antimicrobial, and antitumor investigations

A series of 5‐hydroxy‐4‐(N‐substituted carbothioamide) pyrazole derivatives (HL1–HL5) and their iron(III), nickel(II), and copper(II) complexes have been synthesized. Structural elucidations of the isolated ligands and their complexes are basically accomplished by FT‐IR, 1H NMR, 13C NMR, UV–Vis, ESR, MS, and thermogravimetric analysis (TGA). The analytical data propose the stoichiometries 1:3 (M:L) for Fe(III) and 2:3 for both Ni(II) and Cu(II) complexes. The spectral data substantiate the bidentate coordination mode for all ligands towards metal ions via S and O atoms of CS of the carbothioamide group at pyrazole‐C4 and OH group at C(5) where deprotonation occurs from the enolic tautomer on chelation. Likewise, bidentate pattern of a bridged acetate group is confirmed in the case of Ni(II) and Cu(II) complexes. The magnetic moment values validate high spin octahedral geometry for Fe(III) complexes whereas the diamagnetic feature of Ni(II) complexes is in conformity with the square planar symmetry of low spin state. ESR spectra of all Cu(II) complexes support their existence in distorted square planar geometry with a considerable electron exchange between two copper ion centers of dinuclear type. TGA and DTG analysis of six complexes display their considerable thermal stability. Besides, the in vitro biological screening effects of some selected compounds are tested against various human pathogen microorganisms. Among the ligands, HL5 exhibits the greatest antibacterial activity against two Gram‐positive species (Bacillus subtilis and Staphylococcus aureus) and one Gram‐negative (Proteus vulgaris) in comparison with gentamicin drug. Furthermore, IC50 values of [Cu2(L5)3(OAc)] complex reveal its significant anticancer activity against the three tumor cell lines HCT‐116, MCF‐7, and HepG‐2 compared with imatinib and cisplatin as positive controls. Finally, the optimized structures of all ligands and their molecular electrostatic potential surfaces are established by utilizing density functional theory (DFT).

Chromium(III) catalysts based on tridentate silicon-bridged tris(diphenylphosphine) ligands for selective ethylene tri-/tetramerization

The chromium(III) catalysts based on tridentate silicon-bridged tris(diphenylphosphine) ligands of the form RSi(CH2PPh2)3 (L1: R = Me; L2: R = Cy; L3: R = Ph) were investigated for selective ethylene tri-/tetramerization. The steric and electronic properties of the substituents attached to the silicon moiety have been observed to have a great impact on the catalytic performance of these catalysts. Single-crystal analysis, high-resolution mass spectrometry (HR-MS), and elemental analysis revealed that these complexes may adopt mononuclear tridentate coordination mode (k3-P, P, P) with Cr center. However, one of the phosphorus atoms in these complexes may act as a hemilabile donor and presumably loses its coordination with chromium in the presence of a competent donor which consequently transformed the tridentate complexes to bidentate (k2-P, P) coordination mode. Backbone modification of L1 of the precatalyst 1 via successive abstraction of methylene spacers may offer MeSi(CH2)n(PPh2)3 (L4: n = 2; L5: n = 1; L6: n = 0) type chromium(III) complexes. Ethylene oligomerization of these systems suggested that the methylene spacers may effectively tune the complex structure and catalytic performance. Precatalyst 1 and 4 respectively based on L1 and L4 deliver 70% C8 selectivity in the liquid oligomeric fraction and considerable activity under experimental conditions. DFT investigations based on catalyst 4 revealed that the catalyst may simultaneously facilitate the single and double coordination pathways for C8 formation, however, the single coordination pathway is thermodynamically more favorable for this system.

Synthesis, characterization and application of molecular hammock and pincer type complexes

Synthesis, characterization, coordination, bonding and electronic behavior of an ONS pincer ligand with divalent iron, cobalt, copper and zinc are described. The ligand is synthesized by condensation of dihydroxybenzaldehyde with thiosemicarbazide. The reaction of the ligand with metal ions in 1:2 (M:L) stoichiometric in identical conditions resulted in two octahedral pincer type complexes with iron and cobalt in which two ligands extend a perpendicular shape-retaining the ligand’s linearity, and one trigonal bipyramidal pincer complex with zinc. For copper, the ligand preferred a bidentate coordination mode forming a square planar geometry. The structure of the copper complex can be viewed as a molecular hammock. Quantum mechanical studies at DFT level were undertaken to confirm the geometry, spectroscopic and electronic properties of all the complexes. The ability of the compounds to possess biological activity is tested against various pathogenic bacterial strains. The results show that the copper complex displays higher antimicrobial activities as compared to the ligand and other complexes. A remarkable change in the electronic spectrum of the ligand in the presence of cobalt ion in highly aqueous medium demonstrates its use as a metal sensor among a wide range of biological important metal ions.

Synthesis, crystal structure, antibacterial, antiproliferative and QSAR studies of new bismuth(III) complexes of pyrrolidineditiocarbamate of dithia-bismolane and bismane, oxodithia- and trithia-bismocane

Four new bismuth(III) complexes; (CH2S)2Bi[S2CN(CH2)4] (2), CH2(CH2S)2Bi[S2CN(CH2)4] (3), S(CH2CH2S)2Bi[S2CN(CH2)4] (4), O(CH2CH2S)2Bi[S2CN(CH2)4] (5) were prepared from the reaction of the sodium salt of pyrrolidine-dithiocarbamate (1) with four chloro-dithia-bismuth(III) compounds containing five-, six- and eight-membered heterocycles. The complexes were characterized by elemental analyses, infrared, and 1H and 13C NMR spectroscopy. In addition, the single crystal X-ray structures of 2–4 were obtained, showing an asymmetric bidentate coordination mode of the dithiocarbamate ligand moiety. The metal center in 2 and 3 is tetracoordinated, while in 4 a pentacoordinate metal center is observed, the latter is achieved through the 1,5-transannular Bi⋯S interaction, which is common in these types of metallocane rings. Antibacterial assays showed that 2–5 were active in ATCC and clinical isolated strains. Antiploliferation assays were carried out showing high antiproliferative effect against breast cancer cell lines, in vitro. A QSAR model employing quantum global and local chemical descriptors was constructed to gain further insight into their antibacterial activity.

An Oxalate-Bridged Copper(II) Complex Combining Monodentate Benzoate, 2,2'-bipyridine and Aqua Ligands: Synthesis, Crystal Structure and Investigation of Magnetic Properties.

A dinuclear copper(II) complex of formula [{Cu(bipy)(bzt)(OH2)}2(μ-ox)] (1) (where bipy = 2,2′-bipyridine, bzt = benzoate and ox = oxalate) was synthesised and characterised by diffractometric (powder and single-crystal XRD) and thermogravimetric (TG/DTG) analyses, spectroscopic techniques (IR, Raman, electron paramagnetic resonance spectroscopy (EPR) and electronic spectroscopy), magnetic measurements and density functional theory (DFT) calculations. The analysis of the crystal structure revealed that the oxalate ligand is in bis(bidentate) coordination mode between two copper(II) centres. The other four positions of the coordination environment of the copper(II) ion are occupied by one water molecule, a bidentate bipy and a monodentate bzt ligand. An inversion centre located on the ox ligand generates the other half of the dinuclear complex. Intermolecular hydrogen bonds and π-π interactions are responsible for the organisation of the molecules in the solid state. Molar magnetic susceptibility and field dependence magnetisation studies evidenced a weak intramolecular–ferromagnetic interaction (J = +2.9 cm−1) between the metal ions. The sign and magnitude of the calculated J value by density functional theory (DFT) are in agreement with the experimental data.

Monoanionic triketiminate ligands: Peculiarity of coordination mode to lithium and rare earth ions

Deprotonation of β-triketimines (2,6-Me2C6H3N = CMe)3CH (1), (2,6-Me2C6H3N = CMe)2CH(2-MeOC6H4N = CtBu) (2), (2,6-Me2C6H3N = CMe)2CH(2,6-Me2C6H3N = CtBu) (3) by equimolar amount of n-BuLi afforded lithium triketiminate complexes [(2,6-Me2C6H3N = CMe)3C]Li(THF) (4), [(2,6-Me2C6H3N = CMe)2C(2-MeOC6H4N = CtBu)]Li(THF)2 (5), [(2,6-Me2C6H3N = CMe)2C(2,6-Me2C6H3N = CtBu)]Li(THF)2 (6) in 70–80% yields. The salt metathesis reactions of LnCl3 (Ln = Y, Nd) with 6 lead to the formation of neutral triketiminate dichloro complexes [(2,6-Me2C6H3N = CMe)2C(2,6-Me2C6H3N = CtBu)]LnCl2(THF)2 (Ln = Y (7), Nd (8)) in 78 and 70% yields, while the analogous reaction of YCl3 with 5 resulted in triketiminate yttrium chloro ate complex [(2,6-Me2C6H3N = CMe)2C(2-MeOC6H4N = CtBu)]Y(THF)Cl(µ2-Cl)2Li(THF)2 (9). The reactions of the potassium derivatives of the related triketimines 2, 3 with YbI2(THF)2 resulted in the formation of mononuclear triketiminate iodo Yb(II) complexes [(2,6-Me2C6H3N = CMe)2C(2-MeOC6H4N = CtBu)]YbI(THF)2 (10) and [(2,6-Me2C6H3N = CMe)2C(2,6-Me2C6H3N = CtBu)]YbI(TMEDA) (11). X-ray analysis revealed that in 4 and rare-earth metals complexes 7–11 the monoanionic β-triketiminate ligands [(2,6-Me2C6H3N = CMe)3C]−, [(2,6-Me2C6H3N = CMe)2C(2-MeOC6H4N = CtBu)]−, [(2,6-Me2C6H3N = CMe)2C(2,6-Me2C6H3N = CtBu)]− feature bidentate coordination mode and are coordinated to a metal center only through two nitrogen atoms. The ternary systems 7–9/AliBu3/[CPh3][B(C6F5)4] exhibit catalytic activity in isoprene polymerization, allowing to carry out polymerization of 1000 equivalents in 2 h with 91–100% conversion. The obtained polyisoprenes feature high molecular weights (Mn = 12.8 × 104–20.2 × 104) and moderate polydispersities (Mw/Mn = 2.7–3.6), however excellent control of regio- and stereoselectivities (up to 9.9% cis-1,4 units) was observed.

Bidentate cation-anion coordination in the ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate supported by vibrational spectra and NBO, AIM and SQMFF calculations

Experimental attenuated total reflectance (ATR) and Raman spectra for the synthesized ionic liquid 1-Ethyl-3-methylimidazolium hexafluorophosphate [EMIM+][PF6−] have been combined with the functional hybrid B3LYP and the 6-31G∗ and 6-311++G∗∗ basis sets in order to evaluate the coordination mode of [PF6−] anion and determine the its structural, electronic, topological and vibrational properties. The scaled quantum mechanical force fields (SQMFF) methodology allowed us to obtain a set of scaled force constants fitting the observed wavenumbers because, so far, they have not reported. Experimental ATR and Raman spectra for the ionic liquid [EMIM+][PF6−] in the solid phase are consistent with the corresponding predicted by using both levels of theory. Here, complete vibrational assignments of 72 normal modes of vibration expected for ionic liquid were performed by using B3LYP/6-311++G∗∗ level and considering that the [PF6−] anion adopts a bidentate coordination mode. Atomic Merz-Kollman (MK) charges and bond orders studies have revealed a distorted octahedral symmetry of anion in the ionic liquid and have suggested bidentate coordination of anion by two C–H⋯F hydrogen bonds, as experimentally was also proposed. Natural bond orbital (NBO) and atoms in molecules (AIM) calculations support the high stability of ionic liquid and its high dipole moment value. Frontier orbitals for the three species show that the [PF6−] anion increases the reactivity of ionic liquid. Here, we determine that the B3LYP/6-311++G∗∗ molecular force field for the ionic liquid [EMIM+][PF6−] with the bidentate coordination mode adopted by [PF6−] anion is well represented, as also was supported by the scaled force constants calculated for both C–H⋯F hydrogen bonds.

Silver(I) metallodrugs of thiosemicarbazones and naproxen: biocompatibility, in vitro anti-proliferative activity and in silico interaction studies with EGFR, VEGFR2 and LOX receptors.

Four new heteroleptic silver(I) complexes with the general formula [Ag(L1-4)(nap)] (1-4), where L1-4= 2-(1-(4-substitutedphenyl)ethylidene)hydrazinecarbothioamide and nap=naproxen, have been synthesized and characterized. The geometric parameters determined from density functional theory and UV-Vis studies indicate distorted tetrahedral geometry around silver(I) ion. Fourier transform infrared (FT IR) spectra evidenced asymmetric bidentate coordination mode of carboxyl oxygen atoms of naproxen with silver(I) ion. The complexes are stable for 72h and biocompatibility was analysed towards normal human dermal fibroblast cells, which showed non-toxic nature up to 100ng/ml. In vitro anti-proliferative activity of the complexes by MTT assay was tested against three human cancerous cell lines and one non-tumorigenic human breast epithelial cell line (MCF-10a) in which the complex 4 exhibited enhanced activity. The morphological changes observed by acridine orange/ethidium bromide and Hoechst 33258 staining method reveal apoptosis-inducing ability of the complexes. The molecular docking studies suggest hydrogen bonding, hydrophobic and π-pair interactions with the active site of epidermal growth factor receptor, vascular endothelial growth factor receptor 2 and lipoxygenase receptors.

Synthesis, characterization, catalytic and biological application of half-sandwich ruthenium complexes bearing hemilabile (κ2-C,S)-thioether-functionalised NHC ligands.

A series of cationic Ru(ii)(η6-p-cymene) complexes with thioether-functionalised N-heterocyclic carbene ligands have been prepared and fully characterized. Steric and electronic influence of the R thioether substituent on the coordination of the sulfur atom was investigated. The molecular structure of three of them has been determined by means of X-ray diffractrometry and confirmed the bidentate (κ2-C,S) coordination mode of the ligand. Interestingly, only a single diastereomer, as an enantiomeric couple, was observed in the solid state for complexes 1c, 1i and 1j. DFT calculations established a low energy inversion barrier between the two diastereomers through a sulfur pyramidal inversion pathway with R donating group while a dissociative/associative mechanism is more likely with R substituents that contain electron withdrawing group, thus suggesting that the only species observed by the 1H-NMR correspond to an average resonance position of a fluxional mixtures of isomers. All these complexes were found to catalyse the oxydant-free double dehydrogenation of primary amine into nitrile. Ru complex bearing NHC-functionalised S-tBu group was further investigated in a wide range of amines and was found more selective for alkyl amine substrates than for benzylamine derivatives. Finally, preliminary results of the biological effects on various human cancer cells of four selected Ru complexes are reported.

PQ Group Holdings expands polyolefin catalysts portfolio through an agreement with INEOS

The chromium(III) catalysts based on tridentate silicon-bridged tris(diphenylphosphine) ligands of the form RSi(CH2PPh2)3 (L1: R = Me; L2: R = Cy; L3: R = Ph) were investigated for selective ethylene tri-/tetramerization. The steric and electronic properties of the substituents attached to the silicon moiety have been observed to have a great impact on the catalytic performance of these catalysts. Single-crystal analysis, high-resolution mass spectrometry (HR-MS), and elemental analysis revealed that these complexes may adopt mononuclear tridentate coordination mode (k3-P, P, P) with Cr center. However, one of the phosphorus atoms in these complexes may act as a hemilabile donor and presumably loses its coordination with chromium in the presence of a competent donor which consequently transformed the tridentate complexes to bidentate (k2-P, P) coordination mode. Backbone modification of L1 of the precatalyst 1 via successive abstraction of methylene spacers may offer MeSi(CH2)n(PPh2)3 (L4: n = 2; L5: n = 1; L6: n = 0) type chromium(III) complexes. Ethylene oligomerization of these systems suggested that the methylene spacers may effectively tune the complex structure and catalytic performance. Precatalyst 1 and 4 respectively based on L1 and L4 deliver 70% C8 selectivity in the liquid oligomeric fraction and considerable activity under experimental conditions. DFT investigations based on catalyst 4 revealed that the catalyst may simultaneously facilitate the single and double coordination pathways for C8 formation, however, the single coordination pathway is thermodynamically more favorable for this system.

Spectral properties and biological activity of La(III) and Nd(III) Monensinates

AbstractThe present research is focused on evaluation of complexation ability of Monensic acid (MonH) towards La3+ and Nd3+ ions.Changes in the SRCD spectrum of Monensinate anion were monitored upon addition of lanthanide(III) ions. The antibiotic undergoes formation of one neutral ([Ln(Mon)3(H2O)3]) and two positively charged complex species of composition [Ln(Mon)2(H2O)2]+ and [Ln(Mon) (H2O)]2+, respectively (Ln = La3+, Nd3+). Neutral complexes were isolated as fine powders and were characterized by IR, FAB-MS and ESI-MS. It is assumed that Monensin acts in bidentate coordination mode via monodentate carboxylate moiety and hydroxyl group, both located at the opposite ends of antibiotic molecule.Activity of Monensic acid and [Ln(Mon)3(H2O)3] to decrease visible bacteria growth of B. subtilis, S. Lutea and B. mycoides was evaluated by agar hole diffusion method. Results showed that complexation of lanthanide(III) ions to Monensin enhances the activity of non-coordinated ligand.Antitumor efficacy of compounds was assayed on human triple negative breast cancer and transplantable sarcoma in rat. The cytotoxicity was accessed by MTT test, NR uptake, CV assay and double AO/PI staining. Experimental data revealed that Monensic acid and [Ln(Mon)3(H2O)3] possess concentration- and time-dependent activity, and express promising cytotoxic properties against human and rat permanent cancer cell lines.

Synthesis and structural characterization of new transition metal complexes of a highly luminescent amino-terpyridine ligand

The synthesis, NMR and UV–Vis spectroscopy measurements and X-ray diffraction analysis of four new metal complexes of the amino terpyridine ligand 4′-[4-(4-aminophenyl)phenyl]-2,2′:6′,2″-terpyridine L, namely [FeL2](ClO4)2 (1), [ZnL2](ClO4)2 (2), [CdL2](ClO4)2 (3) and [PtMe3IL] (4), are reported. The X-ray crystal structures of complexes 1–3 are 1:2 metal:ligand structures with tridentate ligands decorated around the octahedral metal centers. In complex 4, with L in a bidentate coordination mode, the Pt(IV) coordinated methyl and iodine groups form a fac-arrangement. The 1H NMR spectrum of 4 shows three 195Pt-1H resonances for the methyl groups incorporating the fac-arrangement, which confirms the bidentate coordination mode of L in solution. The X-ray crystal structure of L shows a transoid conformation of the pyridine ring nitrogen atoms along the interannular bond in the terpyridine core. Ligand L exhibits a bright blue emission in dichloromethane [fluorescence quantum yield (ΦF) = 68%] and its emission maxima shows significant solvatochromism (461 nm in dichloromethane to 533 nm in N,N-dimethylformamide), while its complexes 2 and 3 are only very weakly emissive and 1 and 4 are found to be non-emissive.

Combined statistical physics models and DFT theory to study the adsorption process of paprika dye On TiO2 for dye sensitized solar cells

This study reported the combination of advanced statistical physics modeling and density functional theory (DFT) investigation for the interpretation of the adsorption of Paprika dye on TiO2 surface for dye sensitized solar cells. By using a statistical physics modeling method, an adequate monolayer model with four energies was successfully used to interpret the adsorption process at a macroscopic level. The DFT simulation has been used to study the interaction of the Paprika dye on TiO2 surface to understand some of the atomistic details that are crucial to the dye/semiconductor interaction. We pay particular attention to the adsorption modes, geometries and energies between the paprika dye and TiO2. The DFT simulation determined different binding modes which participated in the adsorption of Paprika dye on TiO2 surface: monodentate coordination via hydrogen atom bond, monodentate coordination via oxygen atom bond and bidentate coordination via two oxygen atoms bond. In particular, calculations showed that the interaction between the paprika dye and TiO2 is strengthened with the bidentate coordination mode via the two hydroxyl and ether functionalities groups involved in the adsorption process.

Palladium(II) complexes of (pyridyl)imine ligands as catalysts for the methoxycarbonylation of olefins

Reactions of 2-methoxy-N-((pyridin-2-yl)methylene)ethanamine (L1), 2-((pyridin-2-yl)methyleneamino)ethanol (L2) and 3-methoxy-N-((pyridin-2-yl)methylene)propan-1-amine (L3) ligands with either [PdCl2(COD)] or [PdCl(Me)(COD)] produced the corresponding monometallic complexes [PdCl2(L1)] (1), [PdClMe(L1)] (2), [PdCl2(L2)] (3) and [PdCl2(L3)] (4). The solid state structure of complex 1 confirmed the bidentate coordination mode of L1, giving a distorted square planar geometry. All the complexes (1–4) formed active catalysts for the methoxycarbonylation of higher olefins to give linear and branched esters. The catalytic behavior of complexes 1–4 were influenced by both the complex structure and olefin chain length.

Crystal structures and luminescence properties of lanthanide complexes with 4-bromobenzoate and nitrogen heterocyclic ligands

Five crystals of lanthanide complexes with 4-bromobenzoate (p-BrBA), 2,4,6-tri(2-pyridyl)-1,3,5-trianzine (TPTZ) and 1,10-phenanthroline (Phen) ligands were synthesized. The structures of the complexes [Sm2(TPTZ-TPTZ)(p-BrBA)4] (1), [Eu2(TPTZ)2(p-BrBA)6] (2), [Tb(TPTZ)(p-BrBA)3(H2O)] (3), [Tb2(Phen)2(p-BrBA)2Ac4] (4) and [Dy2(Phen)2(p-BrBA)6] (5) were determined by single-crystal X-ray diffraction. The crystals 1, 5 belong to monoclinic crystal system, and the other three crystals belong to triclinic crystal system. The dinuclear compound [Sm2(TPTZ-TPTZ)(p-BrBA)4] possesses a coupled [TPTZ-TPTZ]2- ligand that coordinates with two Sm3+ ions in both tridentate and bidentate coordination modes. To investigate the luminescence properties of the complexes, six complexes with similar composition in the powder form were also synthesized, whose formulas are [Eu(TPTZ)(p-BrBA)3(H2O)2], [Tb(TPTZ)(p-BrBA)3(H2O)], [Eu2(Phen)(p-BrBA)3Ac3], [Tb(Phen)(p-BrBA)3], [Sm(TPTZ)(p-BrBA)3(H2O)] and [Dy(Phen)(p-BrBA)3]. The luminescence intensity, luminescence lifetime and quantum efficiency of Eu and Tb complexes with Phen ligand are remarkably superior to the corresponding TPTZ complexes. This difference may mainly result from the stronger structural rigidity of the Phen ligand, which reduces the non-radiative transition of the complexes.

Ternary paddlewheel copper(II) complexes: synthesis, structural elucidation, DNA-binding, anti-oxidant and conductance studies

ABSTRACTTwo new binuclear Cu(II) complexes Cu2L4(DMS)2 (1) and Cu2L4(3BrPy)2 (2) where L = para-chlorophenyl acetate, DMS = dimethylsulfoxide and 3BrPy = 3-bromopyridine have been synthesised and characterised using FT-IR, single crystal XRD analysis, absorption and conductance studies. In both the complexes copper(II) ion lies in distorted square pyramidal geometry where the apical position is occupied by pyridine in monodentate fashion while the equatorial positions are occupied by four carboxylate ligands in bidentate coordination mode. The supramolecular structures of the complexes arise primarily as a result of C–H…O and H–C…H types of interactions and are different owing to the different apical ligands. The DNA-binding activity of the complexes has been studied through absorption spectroscopy, viscometry and competitive ethidium bromide displacement techniques. These techniques indicated a mixed electrostatic and intercalative mode of interaction with DNA-binding constant values Kb of 1.98 × 104 M−1 and 2.86 × 104 M−1 for complexes 1 and 2, respectively. These activities represent the preliminary biological relevance of the synthesised complexes.