H2L1 H2L4 Research Articles

Structurally different mono-, bi- and trinuclear Pd(ii) complexes and their DNA/protein interaction, DNA cleavage, and anti-oxidant, anti-microbial and cytotoxic studies

A series of new structurally different Pd(ii) complexes was obtained by the reactions between K2[PdCl4], 3-methoxysalicylaldehyde-4(N)-substituted thiosemicarbazone [H2L1–H2L4] and bis(diphenylphosphino)ethane [dppe].

Copper(II) complexes based on 2-thenoyltrifluoroacetone aroyl hydrazones: Synthesis, spectroscopy, and X-ray diffraction analysis

Copper(II) complexes CuL • NH3 are synthesized by the interaction of ethanol solutions of parasubstituted 2-thenoyltrifluoroacetylmethane aroyl hydrazones (H2L1–H2L4) and an aqueous-ammonia solution of copper(II) acetate in an equimolar ratio. The copper(II) complexes are studied by elemental analysis, IR spectroscopy, and EPR spectroscopy. Single crystals of CuL3 • NH3 are grown from 1-(2-thenoyl)- 3,3,3-trifluoroacetone para-methylbenzoyl hydrazone and studied using X-ray diffraction analysis (CIF file CCDC 1045841).

CT-DNA/BSA protein binding and antioxidant studies of new binuclear Pd(II) complexes and their structural characterisation

New palladium(II) binuclear complexes (1–4) of the type [Pd2(Msal-Rtsc)2(μ-dppm)] (R=H or CH3 or C2H5 or C6H5) were prepared and characterised by using various spectro analytical techniques. The true coordinating nature of the ligands in the complexes was confirmed by X-ray crystallographic studies. From the X-ray crystallographic analysis, it is found that the ligands [H2L1–H2L4] were bound to metal as tridentate ONS donors and phosphorus atom of bridged diphenylphosphinomethane satisfied the fourth coordination site in both the metal units to form a binuclear complexes. The interaction mode of the complexes (1–4) with calf-thymus DNA (CT-DNA) has been explored by absorption titrations and ethidium bromide displacement study was used to confirm the mode of binding. Based on the results obtained, electrostatic and intercalative binding modes have been proposed. Quenching the tryptophan and tyrosine residues of Bovine Serum Albumin (BSA) by complexes were found as static. Anti-oxidant properties of the complexes were tested against, 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH), superoxide anion radicals.

Uranyl(VI) binding by bis(2-hydroxyaryl)diimine and bis(2-hydroxyaryl)diamine ligand derivatives. Synthetic, X-ray, DFT and solvent extraction studies

The interaction of uranyl(VI) nitrate with a series of bis(2-hydroxyaryl)imine (H2L1–H2L5) and bis(2-hydroxyaryl)amine (H2L8, H2L9) derivatives incorporating 1,3-dimethylenebenzene or 1,3-dimethylenecyclohexane bridges between nitrogen sites is reported. Crystalline complexes of type [UO2(H2L)(NO3)2] (where H2L is H2L1–H2L4) were isolated from methanol. X-ray structures of the complexes of H2L1, H2L2 and H2L4 show that each of these neutral ligands bind to their respective UO22+ centres in a bidentate fashion in which coordination only occurs via each ligand’s hydroxy functions. Two bidentate nitrate anions complete the metal’s coordination sphere in each complex to yield hexagonal bipyramidal coordination geometries. A density functional theory (DFT) investigation of [UO2(H2L1)(NO3)2] in a simulated methanol environment is in accord with this complex maintaining its solid state conformation in solution. Solvent extraction experiments (water/chloroform) employing H2L1–H2L7 in the organic phase and uranyl(VI) nitrate in the aqueous phase showed that both amine derivatives, H2L8 and H2L9, yielded enhanced extraction of UO22+ over the corresponding imine derivatives, H2L1 and H2L2. These results were further compared with those obtained for the corresponding Schiff bases incorporating 1,2-phenylene and 1,2-cyclohexane bridged ligands, H2L6 and H2L7; these more rigid systems also yielded enhanced extraction of UO22+ relative to the more flexible Schiff bases H2L1–H2L5. A very significant synergistic enhancement of the extraction of UO22+ by H2L1–H2L4 and H2L7 was observed in the presence of a 10-fold excess of n-octanoic acid; the influence of pH on extraction efficiency was also investigated. A parallel set of experiments employing H2L1–H2L9 as extractants for europium(III) nitrate indicated a clear uptake preference for UO22+ over Eu3+ in all cases; separation of the uranyl ion from the rare earths is an important objective in mineral processing.

New palladium(II) complexes of 3-methoxysalicylaldehyde-4(N)-substituted thiosemicarbazones: Synthesis, spectroscopy, X-ray crystallography and DNA/protein binding study

A series of 4(N)-substituted 3-methoxysalicylaldehyde thiosemicarbazone (H2L1–H2L4) were reacted with equimolar amount of [PdCl2(AsPh3)2] in ethanol/dichloromethane medium. The new complexes have been characterized by various spectroscopic techniques. The structure determination of the complexes [Pd(H-Msal-mtsc)(AsPh3)](2), [Pd(H-Msal-etsc)(AsPh3)](3) and [Pd(Msal-ptsc)(AsPh3)](4) by X-ray crystallography showed that the ligands H2L2 and H2L3 are coordinated as monobasic bidentate NS donor in the complexes 2 and 3 by forming a five member chelate ring. However, in the complex 4, the ligand H2L4 bound to palladium as dibasic tridentate ONS donor by forming six and five member chelate rings. The binding ability of the palladium(II) precursor [PdCl2(AsPh3)2], ligands (H2L1–H2L4) and their corresponding complexes (1–4) with calf-thymus DNA (CT DNA) has been examined by photophysical studies, which revealed that the complexes bound to DNA through intercalation mode. The protein binding studies have been monitored by quenching of tryptophan and tyrosine residues in the presence of compounds by taking bovine serum albumin (BSA) as a model protein and the mechanism of quenching was found as static. The binding study results showed that the new complexes 1–4 possess better binding affinity than the starting precursor and ligands (H2L1–H2L4).

Polydentate Schiff Base Ligands and Their La(III) Complexes: Synthesis, Characterization, Antibacterial, Thermal, and Electrochemical Properties

We synthesized the Schiff base ligands H2L1–H2L4 and their La(III) complexes and characterized them by the analytical and spectroscopic methods. We investigated their electrochemical and antimicrobial activity properties. The electrochemical properties of the ligands H2L1–H2L4 and their La(III) complexes were studied at the different scan rates (100 and 200 mV), different pH ranges (), and in the different solvents. The electrooxidation of the Schiff base ligands involves a reversible transfer of two electrons and two protons in solutions of pH up to 5.5, in agreement with the one-step two-electron mechanism. In solutions of pH higher than 5.5, the process of electrooxidation reaction of the Schiff base ligands and their La(III) complexes follows an ECi mechanism. The antimicrobial activities of the ligands and their complexes were studied. The thermal properties of the metal complexes were studied under nitrogen atmosphere in the range of temperature 20–1000°C.

Synthesis, characterization, electrochemistry, catalytic, and antimicrobial studies of ruthenium(III) complexes containing ONO donor ligands

A series of ruthenium(III) complexes [RuX(EPh3)2L] (where X = Cl or Br; E = P or As; L = deprotonated dibasic tridentate ligand) were prepared by the reaction of [RuX3(EPh3)3] with Schiff bases (H2L1–H2L4). The ligands were prepared by the condensation of N-4 phenyl/methyl semicarbazide with o-vanillin/o-hydroxy acetophenone. The complexes were characterized by elemental, physico-chemical, and electrochemical methods. Catalytic studies of these complexes for the oxidation of alcohols and aryl–aryl coupling were carried out. Antimicrobial experiments were also carried out.

Synthesis of cobalt(II) complexes with p-tert-butylcalix[4]arene-supported dihydroxamic acids

Four p-tert-butylcalix [4]arene supported dihydroxamic acids(H2L1–H2L4) and their cobalt(II) complexes CoL2 and CoL4 have been synthesised by condensation of hydroxylamine or N-substituted hydroxylamine with the calix [4] arene diacid chloride.

Synthesis and characterisation of chelating polycarboxylate ligands capable of forming intermolecular, complementary triple hydrogen bonds

The reaction between the dianhydride of ethylenedinitrilotetraacetic acid (edta) 1 and aminouracil derivatives was utilised to synthesize bifunctional, chelating ligands capable of co-ordinating to a metal centre via the edta backbone, while simultaneously being able to form complementary intermolecular hydrogen bonds via the uracil moieties. 5-Aminouracil 2, 5-aminoorotic acid 3, 5,6-diaminouracil 4 and 5,6-diamino-2-thiouracil 5 were treated with 1 in dry dmf or dmso to give functionalised dicarboxamide derivatives H2L1–H2L4 in 15–90% yield. The 5,6-diaminouracils 4 and 5 reacted with the dianhydride exclusively via the 5-amino position. The reaction of H2L1–H2L4 with basic metal salts [e.g. KVO3 and Zn(O2CMe)2] in aqueous solutions led to the formation of metal complexes of the anionic ligands L1–L4: K[VO2L1]·5H2O, [Zn(OH2)L1]·4H2O and [Zn(OH2)L3]·5H2O were characterized by single-crystal X-ray crystallography. The solid state structures of these complexes show that the uracil moieties are situated on pendant side-arms. The high degree of rotational freedom of these hydrogen-bonding groups makes this class of metal complex promising in terms of specific binding to water-soluble biomolecules having complementary hydrogen-bonding sites.

Synthesis, structure and metal redox of new VO3+and VO2+complexes incorporating mixed tridentate–bidentate binding

The reaction of bis(acetylacetonato)oxovanadium(IV) with a mixture of a tridentate ONO-co-ordinating hydrazone H2L1–H2L4(general abbreviation H2L; condensates of benzoylhydrazine with benzoylacetone, salicylaldehyde, 2-hydroxy-1-naphthaldehyde and 2-hydroxybutyrophenone respectively) and a bidentate compound 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen) or quinolin-8-ol (Hquin) has afforded the complexes [VIVO(L)(bipy)]. [VIVO(L)(phen)] and [VVO(L)(quin)] in high yields. The crystal structure of [VO(L1)(quin)] has been determined, revealing the distorted-octahedral VO(ONO)(ON) co-ordination sphere with the L1 ligand spanning meridionally. The VO distance is 1.592(3)A and the atom lying trans to VO is the quin nitrogen. There is a large decrease (≈ 700 mV) in the VO3+–VO2+E½ values between [VO(L)(bipy)]{or [VO(L)(phen)]} and [VO(L)(quin)]. The complex [VIVO(L)(quin)]– was electrogenerated in solution but spontaneously reoxidized to [VVO(L)(quin)] in air. For a given bidentate ligand, the VO3+–VO2+E½ values follow the order L1 < L4 < L2 < L3. The ESR spectra of the VO2+ complexes correspond to an axially compressed dxy1 configuration. The 51V hyperfine constants are slightly larger for [VO(L)(quin)]– than for [VO(L)-(bipy)] and [VO(L)(phen)]. The dxy→ dxz,dyz transition of the tetravalent complexes occurs in the region 700–950 nm.

Chemistry of bis(o-benzosemiquinonato)bis(triphenylphosphine)ruthenium(II) complexes. Crystal and molecular structure of [Ru(O2C6Cl4)2(PPh3)2

The green complexes [Ru(Ls)2(PPh3)2]·2H2O (Ls=o-benzosemiquinonate) are obtained in excellent yields by the reaction of catechols H2L1–H2L4 with [RuH(Hsa)(PPh3)3]{H2L1= C6H4(OH)2-1,2; H2L2= 4-ButC6H3(OH)2-1,2; H2L3= 3,5-But2C6H2(OH)2-1,2; H2L4= C6Cl4(OH)2-1,2; H2sa = salicylic acid}. The crystals of the tetrachloro complex are triclinic, space group P with a= 9.430(5), b= 11.689(4), c= 12.551 (6)Å, α= 68.58(3), β= 72.07(4), γ= 79.92(4)° and Z= 1; the final R factor is 0.0406 for 4741 observed reflections. The complex is centrosymmetric with a trans-RuO4P2 co-ordination sphere; the average C–O distance is 1.310(5)Å. Significant dπ–pπ* back-bonding occurs within the RuII(Ls)2 fragment and metal-to-ligand charge-transfer (m.l.c.t.) transitions are observed in the near-IR region (900–1300 nm). In dichloromethane solution four successive one-electron cyclic voltammetric couples are observed. The product of the first one-electron reduction has been identified as [RuIII(Lc)2]–(Lc= catecholate) from ESR spectra. The probable nature of the other members of the redox series is discussed.