Free HL Research Articles

Linkage and Geometrical Isomers of Dichloridobis(triphenylphosphine)ruthenium(II) Complexes with Quinoline‐2‐carbaldehyde (Pyridine‐2‐carbonyl)hydrazone: Their Molecular Structures and Electrochemical and Spectroscopic Properties

AbstractThe reactions of quinoline‐2‐carbaldehyde (pyridine‐2‐carbonyl)hydrazone (HL) and [RuCl2(PPh3)3] in various solvents at different temperatures gave the three geometrical isomers trans(Cl,Cl)‐, cis(Cl,Cl),trans(P,N)‐, and trans(P,P)‐[RuCl2(PPh3)2{HL‐κO(amide),κN(imine)}] (1, 2, and 3, respectively) as well as a linkage isomer trans(P,P)‐[RuCl2(PPh3)2{HL‐κN(imine),κN(quin)}] (4). The molecular and crystal structures of 1–4, together with both E and Z configurational isomers (with respect to the C=N double bond) of the free ligand HL, were determined by X‐ray analysis. The ligand HL adopted a Z form and acted as a κO(amide),κN(imine) bidentate ligand in 1–3, whereas it was an E isomer with a κN(imine),κN(quin) coordination mode in 4. The gradual thermal conversions of 1 to 2 and of 2 to 3 were observed in dichloromethane and ethanol, respectively, but an interconversion between 3 and 4 was not detected. In dichloromethane, all complexes have a reversible RuIII/II redox couple in the range 110–412 mV (vs. Ag/Ag+), and the redox potential was largely dependent on the coordination mode of HL and on the mutual configuration of the two PPh3 ligands. Such a potential shift can be interpreted as a combination of Cl–/amide O π‐donor and PPh3/quinoline N π‐acceptor orbital contributions to the RuII dπ orbitals [highest occupied molecular orbitals (HOMOs)]. Complexes 3 and 4 in acetonitrile showed a gradual spectral change, probably because of the substitution of the Cl– ligand by the acetonitrile solvent. In addition, 2–4 showed solvatochromic behavior even in noncoordinating solvents that resulted from a blueshift of the metal‐to‐ligand charge‐transfer (MLCT) transition band in polar solvents. These electrochemical and spectroscopic properties are also supported by DFT and time‐dependent DFT (TD‐DFT) calculations.

Synthesis, DNA binding, antioxidant and cytotoxic activities of ruthenium(II) complexes of a Schiff base ligand

Three ruthenium(II) complexes, [Ru(CO)Cl(PPh3)L], [Ru(CO)Cl(AsPh3)L] and [Ru(CO)Cl(Py)L], were synthesized from the reactions of 2-(benzothiazol-2-yliminomethyl)-phenol (HL) with [RuHCl(CO)B(EPh3)2], where B = PPh3, AsPh3 or pyridine, and E = P or As. All the complexes have been characterized by physicochemical and spectroscopic methods. The structure of the free ligand HL was determined by single crystal X-ray diffraction. The binding of the free ligand and its complexes with CT-DNA was studied using electronic absorption spectroscopy. In addition, the free ligand and its complexes were subjected to antioxidant activity tests, which showed that they all possess significant scavenging effects against DPPH and OH radicals. The in vitro cytotoxicities of the compounds were assessed using tumor (HeLa and MCF-7) cell lines.

Mapping the supramolecular chemistry of pyrazole-4-sulfonate: layered inorganic–organic networks with Zn2+, Cd2+, Ag+, Na+and NH4+, and their use in copper anticorrosion protective films

Five compounds based on the versatile pyrazole-4-sulfonate anion (4-SO3-pzH = L−) were synthesized by the reaction of ligand HL with ZnO, CdCO3, Ag2O, NaOH and NH3, respectively. Crystals of Zn(4-SO3-pzH)2(H2O)2, Cd(4-SO3-pzH)2(H2O)2, Ag(4-SO3-pzH), Na(4-SO3-pzH)(H2O) and NH4(4-SO3-pzH) were obtained from aqueous solutions upon evaporation, and were characterized by single-crystal X-ray diffraction, IR and NMR spectroscopy, thermogravimetric analysis and copper corrosion inhibition experiments. We found that the non-isomorphous, 3-dimensional inorganic–organic layered solid state structure of these compounds is determined by an intricate interplay between the size, charge and coordination preference of the cation, and an extended lattice of hydrogen bonds and aromatic interactions. Ligand L− incorporates a host of different binding capabilities (metal coordination through the pyrazole N-atom and/or the sulfonate O-atom, hydrogen-bonding both as donor and acceptor, π–π and C–H⋯π interactions). Thin films formed by these complexes on copper metal surfaces were studied by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. ZnL2, CdL2, AgL and NH4L, in addition to the free ligand HL, were tested as corrosion inhibitors on copper metal surfaces at three different pH values (2, 3 and 4), and the corrosion rates were quantified. Significant corrosion protection was observed with all compounds at pH 4 and 3.

A Schiff base ligand N-(2-hydroxylacetophenone)-3-oxapentane-1,5-diamine and its nickel(II) complex: synthesis, crystal structure, antioxidation, and DNA-binding properties

A new Schiff base ligand N-(2-hydroxylacetophenone)-3-oxapentane-1,5-diamine (HL) and its Ni complex, [Ni2(L)2(NO3)2], have been synthesized and characterized by physicochemical and spectroscopic methods. The X-ray crystal structure of [Ni2(L)2(NO3)2] shows it to be a dinuclear 2:2 complex, in which each Ni(II) atom is in a distorted octahedral geometry. The two Ni(II) atoms are dibridged by two phenoxo ligands, forming a Ni2O2 parallelogram-type moiety. The interactions between free HL and the complex with calf thymus DNA have been investigated, and the binding constant and linear Stern–Volmer quenching constant suggest that the two compounds bind to DNA via the intercalation mode. The binding affinity of the complex was higher than that of HL. Antioxidant assays in vitro showed that the Ni(II) complex possesses significant antioxidant activity.

Synthesis and complexes of an N4 Schiff-base macrocycle derived from 2,2′-iminobisbenzaldehyde

An N(4) tetradentate [1 + 1] Schiff base metal free macrocycle HL was prepared, by 1 : 1 condensation of 2,2'-iminobisbenzaldehyde (1) and diethylenetriamine, and characterised. Seven mononuclear complexes, [Zn(II)L(py)](BF(4)) (2), [Cu(II)L](BF(4))]·H(2)O (3), [Ni(II)L](BF(4))·H(2)O (4), [Co(II)L](BF(4))]·H(2)O (5), Fe(III)L(BF(4))(2)·2H(2)O·MeCN (6), [Co(III)L(NCS)(2)]·0.3py (7) and [Fe(III)L(NCS)(2)] (8), of L(-) are reported. The Cu(II) and Ni(II) complexes were prepared by a template approach whereas the others were accessed by metallation of pre-formed HL. The X-ray crystal structure determinations show that [Cu(II)L](BF(4)) and [Ni(II)L](BF(4)) feature square planar N(4) coordinated Cu(II) and Ni(II) centres, respectively, whereas [Fe(III)L(NCS)(2)]·NO(2)Me features an octahedral N(6) coordinated Fe(III) centre (two NCS anions bound axially) and the Zn(II) complex, which crystallised as 2{[Zn(II)L(py)](BF(4))}·py, features square pyramidal Zn(II) ions (a pyridine molecule bound axially). In all cases the N(4) macrocycle is bound equatorially to the metal ion. Cyclic voltammograms of the soluble BF(4) complexes, 2-5, were carried out in MeCN vs. 0.01 mol L(-1) AgNO(3)/Ag and revealed multiple, mostly irreversible or quasi-reversible, redox processes. The Zn(II) complex 2 exhibited two irreversible oxidation processes and one irreversible reduction process, all of which are ligand-centered. The Ni(II) complex 4 showed a process with a weak return wave at E(m) = +0.57 V (ΔE = 0.05 V). Interestingly, after controlled potential coulometry experiments on 2, 3 and 4 (at +0.48, +0.61 and +0.71 V which transferred 1.2, 1.0 and 1.6 e(-) equiv. per complex, respectively), a new reversible or quasi-reversible process was obtained, with a lower potential than beforehand (E(m) (ΔE)/V = +0.16 (0.08), +0.31 (0.13) and +0.45 (0.11) respectively).

Dinuclear Zn(II) and Hg(II) complexes of an angular dipyridyl ligand: syntheses, crystal structures, and properties

The angular polytopic dipyridyl ligand 2,6-bis(quinoline-2-carboxamido)pyridine (H2L) was prepared. Assemblies of H2L with ZnAc2 and HgAc2 resulted in two new dinuclear complexes [Zn2(L)(Ac)2] · 1.5H2O · 0.5CH3OH (1) and [Hg2(L)(Ac)2] · 5H2O · CH3OH (2) where the doubly deprotonated L2− bi-chelate as μ-kN,N′ : kN″,N″′, bridging the two metal centers (Ac = acetate). In 1, the two Zn(II) ions are also doubly bridged by two Ac ions in a μ-kO : kO′ coordination, and thus each metal center adopts a distorted tetrahedral geometry. In 2, each Ac ion is only terminal to Hg(II), in a rare distorted triangular or T-shaped coordination geometry. Free H2L, 1, and 2 emit interesting bluish-green fluorescence with strong intensities. Thermogravimetric analysis of 1 shows that the dinuclear structure of 1 is stable to 382°C.

Copper(II) and palladium(II) complexes of a terdentate pyrrolidine diester ligand

The synthesis and characterisation of three copper(II) complexes, [CuLCl] ( 4), [CuLBr] ( 5) and [CuL(NCS)] ( 6), and a palladium(II) complex, [PdLCl] ( 7), of the monoanionic terdentate ligand L − [L − is the deprotonated form of diethyl 2,2′-(pyrrolidine-2,5-diylidene)diacetate (HL) ( 3)] are reported. The X-ray crystal structure determinations show that both 4 and 6 feature square planar copper(II) centres. The cis bond angles are close to 90° (85–93°) thanks in large part to the introduction of an additional carbon atom between the pyrrole ring and each of the ester moieties. These results indicate that the failure of the 2,5-diiminopyrrole head unit to coordinate in a terdentate manner to first row transition metal ions can, in principle, be resolved by introducing an extra carbon atom between the pyrrole ring and each of the imine moieties. A comparison of structural parameters between the two structurally characterised complexes ( 4 and 6) and the non-deprotonated free ligand HL ( 3) indicates that there is an increase in delocalisation of the electron density throughout the π system of the deprotonated ligand on coordination, as the C C and C O double bonds are longer and C–C and C–O single bonds are shorter than the corresponding bond distances in 3.

Synthetic, spectral, magnetic and in vitro cytotoxic activity studies of cobalt(II) complexes with cytokinin derivatives: X-ray structure of 6-(3-methoxybenzylamino)purinium chloride monohydrate

Cobalt(II) complexes with 6-(2-hydroxybenzylamino)purine (HL 1), 6-(2-methoxybenzylamino)purine (HL 2), 6-(3-methoxybenzylamino)purine (HL 3) and 6-(4-methoxybenzylamino)purine (HL 4) of the composition [Co(L 1)Cl(H 2O) 2] · H 2O ( 1), [Co(L 2)Cl(H 2O) 2] ( 2), [Co(L 3) 2(H 2O) 2] · 2H 2O ( 3), [Co(L 4) 2(H 2O) 2] · 2H 2O ( 4) have been synthesized. The compounds have been characterized by elemental analysis, FT-IR, ES+ MS (electrospray mass spectra in the positive ion mode) and electronic spectroscopies, magnetic and conductivity data as tetrahedral high-spin cobalt(II) complexes. The thermal stability of the complexes has also been studied. The cytotoxicity of the complexes ( 1– 4) was determined by a Calcein acetoxymethyl (AM) assay. Human malignant melanoma ( G361), human chronic myelogenous erythroleukemia ( K562), human osteogenic sarcoma ( HOS) and human breast adenocarcinoma ( MCF7) cell lines were used for the testing. The molecular structure of 6-(3-methoxybenzylamino)purinium chloride monohydrate, H 2 L 3 + · Cl · H 2 O , i.e. a protonated form of the free HL 3 ligand, has been determined by a single crystal X-ray analysis. The geometry optimisation and infrared frequencies calculations of HL 1, HL 2, and H 2 L 3 + and H 2 L 4 + were performed using density-functional theory (DFT) calculations at the B3LYP/6-31G* level of the theory. The geometry of complex ( 1) was optimised at the same level of the theory.

Design and synthesis of a new binucleating ligand via cobalt-promoted C-N bond fusion reaction. Ligand isolation and its coordination to nickel, palladium, and platinum.

A new polydentate bridging ligand, NH(4)C(5)N=NC(6)H(4)N(H)C(5)H(4)N (HL(2)), is synthesized by the cobalt-mediated phenyl ring amination of coordinated NH(4)C(5)N=NC(6)H(5). The green cobalt complex intermediate [Co(L(2))(2)](ClO(4)), [1](ClO(4)), and the free ligand HL(2) were isolated and characterized. The X-ray structure of [H(2)L(2)](ClO(4)) is reported. The ligand, upon deprotonation, behaves as a bridging ligand. It reacts with NiCl(2).6H(2)O and Na(2)[PdCl(4)] to produce dimetallic complexes, [Ni(2)Cl(2)(L(2))(2)], 2, and [Pd(2)(L(2))(2)](ClO(4))(2), [3](ClO(4))(2), respectively. X-ray structures of these two dimetallic complexes are reported. The structure of the dinickel complex, in particular, is unique. In this complex, the two deprotonated secondary amine nitrogens of the two [L(2)](-) ligands bind to two nickel centers simultaneously forming a planar Ni(2)N(2) arrangement. The complex [3](ClO(4))(2) is diamagnetic while the complex 2 is paramagnetic. The results of magnetic measurements on the dinickel complex in the temperature range 1.8-300 K are reported. The system can be described as a single spin S = 2 in the low-temperature range T << J/k whereas at high temperatures, T >> J/k, it behaves as two independent spins S = 1.The reaction of [L(2)](-) with K(2)[PtCl(4)], however, yielded a monometallic platinum complex, [PtCl(3)(L(2))], 5, where the pyridyl nitrogen of the aminopyridyl function remained unused. The X-ray structure of the complex 4a is reported. The bond lengths along the ligand backbones in all the complexes indicate extensive pi-delocalization. Spectral data of the complexes are reported and compared.

Reactivity of the tetraphenyldithioimidodiphosphine–diiodine (HL·I2) adduct towards indium powder

The reaction of indium powder with the mixture (SPPh2)2NH and I2 (HL·I2) in Et2O at room temperature gave the indium(III) complex InLI2 (1). The reaction occurs in two steps, the first of which leads to the formation of InI3 and free HL, then the subsequent reaction between these species yields compound 1, H+, and the anion InI4−. The crystal lattice of 1 is made up of neutral acentric molecules where the metal ion is bonded through two sulfur atoms to one anionic (SPPh2)2N− (L) ligand and two iodide ions. The central InIII ion shows a slightly distorted tetrahedral coordination geometry. Density functional theory (DFT) calculations, carried out at the B3LYP level, have been used to interpret the electrochemical behaviour of 1.

Synthesis, characterization and antitumour activity of copper(II) 6-(4-chlorobenzylamino)purine complexes. X-ray structure of 6-(4-chloro-benzylamino)purinium perchlorate

Copper(II) complexes with 6-(4-chlorobenzylamino)purine (HL) have been prepared and characterized by elemental analysis, electronic, i.r., ES + mass and 13C-n.m.r. spectra, and by magnetic and conductivity data. Based on these physical methods, mainly the temperature dependence of magnetic susceptibility data, we conclude that the complexes are: [Cu2(μ-Cl)2(μ-HL)2Cl2] (1) and [CuCl3(H+L)2]Cl (2). They have been studied for their possible antitumour activity against human malignant melanoma G-361, human osteogenic sarcoma HOS, human chronic myelogenous leukaemia K-562 and human breast adenocarcinoma MCF7 cells in vitro. The IC50 values were determined by calcein AM assay. The molecular structure of 6-(4-chlorobenzylamino)purinium perchlorate, i.e. a protonated form of the free HL ligand, has been determined by a single crystal X-ray analysis.

Protonation, complexation and thermochemical behaviour of N-benzoylthiocarbamic- O-alkylester anions in solution

Enthalpies of protonation and metal complex formation of anions of a series of five N-benzoylthiocarbamic- O-alkylesters (R=Et, i-Pr, n-Bu, n-Hex, n-Dodec; 1–5) have been measured by titration calorimetry. Using known stability constants the reaction entropies have been calculated. The free ligands HL are verified to react as NH-acids. The remarkable gain of entropy mainly depends on the high number of lost molecules from the extended solvation shell of the reacting species in the 1,4-dioxane/water mixture. The nickel(II) cations are bound in the complex through similar forces than the NH-proton in the ligand.

(Hexamethylbenzene)ruthenium(II) complexes: synthesis and coordination chemistry of a novel tridentate ligand with an O,O,Cl-donor set

Trimethyl phosphite reacts with (((C/sub 6/Me/sub 6/)RuCl/sub 2/)/sub 2/) in methanol to yield the cation ((C/sub 6/Me/sub 6/)RuCl(P(OCH/sub 3/)/sub 3/)/sub 2/)/sup +/, which has been isolated as a chloride or hexafluorophosphate salt. This cation undergoes a sequence of two Michaelis-Arbuzov type reactions to give the neutral complex and the L/sup -/ anion ((C/sub 6/Me/sub 6/)RuCl(P(O)(OCH/sub 3/)/sub 2/)/sub 2/)/sup -/. Attempts to isolate the anion in the form of its sodium salt NaL have led to products that always contain additional sodium iodide or sodium hexafluorophosphate. The free acid HL can be prepared by protonation from NaL or directly from the reaction of (((C/sub 6/Me/sub 6/)RuCl/sub 2/)/sub 2/) with dimethyl phosphonate, HP(O)(OCH/sub 3/)/sub 2/. L/sup -/ is a uninegative, potentially bidentate or tridentate ligand with an O,O,Cl donor set. It reacts with many transition-metal and main-group-metal ions, e.g. M/sup n+/ = Mg/sup 2 +/, Mn/sup 2 +/, Co/sup 2 +/, Ni/sup 2 +/, Cu/sup 2 +/, Zn/sup 2 +/, Cd/sup 2 +/, Pb/sup 2 +/, Al/sup 3 +/, or Fe/sup 3 +/, to give 2:1 complexes of the composition (ML/sub 2/)/sup (n-2)+/. The reactions of the complexes (((ring)MCl/sub 2/)/sub 2/), (ring)M = (C/sub 5/Me/sub 5/)Rh, (C/sub 6/Me/sub 6/)Ru, and (p-cymene)Ru, withmore » L/sup -/ lead to the cationic complexes ((C/sub 5/Me/sub 5/)RhL)/sup +/, ((C/sub 6/Me/sub 6/)RuL)/sup +/, and ((p-cymene)RuL)/sup +/, which have been isolated as hexafluorophosphate salts. HL oxidatively adds to the metal(0) complexes (Mo(CH/sub 3/CN)/sub 3/(CO)/sub 3/) and (W(DMF)/sub 3/(CO)/sub 3/) to yield metal hydride complexes of the composition (LM(CO)/sub 3/H). The molybdenum hydride is labile and rapidly gives HL and Mo(CO)/sub 6/ under an atmosphere of CO gas.« less

Thiorganoantimony(V) Complexes of Schiff Bases Obtained from Substituted Salicylaldehydes ando-Phenylenediamine or 2-Aminopyridine

Abstract A series of Schiff base complexes of the type R3SbBrL (R = Me or Ph; L− = anion of tridentate monobasic Schiff base ligand of ONN type) have been synthesized and investigated. The free ligands HL are N-(salicylidene)-o-phenylenediamine, (SPD-H), N-(2-hydroxy-1-napthalidene)-o-phenylenediamine (HNAP-H), N-salicylidene-2-aminopyridine, (SAP-H) and N-(2-hydroxy-1-naphthalidene)-2-aminopyridine (HNAP-H). Molecular weight determination in benzene reveals the monomeric nature of these complexes. Both IR and NMR data suggest hepta-coordinated structures for R3SbBr(SPD) and R3SbBr(HNPD) indicating the tridentate nature of the ligands SPD-H and HNPD-H. On the other hand, the complexes R3SbBr(SAP) and R3SbBr(HNAP) are hexa-coordinated indicating the bidentate nature of the ligands SAP-H and HNAP-H.