Bidentate Phen Research Articles

Solvent driven structural topologies involving unconventional O[sbnd]H(methanol)⋯π contact and anti-cooperative HB⋯anion-π⋯HB assemblies with unusual enclathration of dual guest (H2O)4 cores in Mn(II) and Ni(II) coordination compounds: Antiproliferative evaluation and theoretical studies

Two Mn(II) and Ni(II) coordination complexes viz. [Mn(phen)2(2,6-PDC)]·2CH3OH (1) and [Ni(2,6-PDC)2][Ni(H2O)4(en)]·6H2O (2) (phen = 1,10-phenanthroline, 2,6-PDC = 2,6-pyridinedicarboxylate and en = ethylenediamine) have been isolated at ambient conditions and characterized by elemental analysis, FT-IR, electronic spectroscopy, TGA and single crystal X-ray diffraction. Switching the solvent from methanol to water has changed the structural topologies of the compounds. Compound 1 is composed of a hepta-coordinated Mn(II) centre with two bidentate phen and one tridentate 2,6-PDC; whereas compound 2 is composed of cationic [Ni(H2O)4(en)]2+ and anionic [Ni(2,6-PDC)2]2– moieties with hexa-coordinated Ni(II) centers. Crystal structure analysis of compound 1 unfolds the presence of unorthodox OH(methanol)⋯π interactions involving the uncoordinated methanol molecules. The unusual enclathration of dual H-bonded guest (H2O)4 cores in the hexameric Ni(II) hosts in compound 2 provides rigidity to the crystal structure. The antiparallel π-stacked dimers and anti-cooperative HB···anion-π···HB assemblies observed in the solid-state structures of 1 and 2 respectively have been studied theoretically using DFT calculations and NCI plot index computational tools. In vitro anticancer evaluation of the compounds considering cell cytotoxicity and apoptosis assay showed significant concentration dependent cytotoxicity in Dalton’s lymphoma (DL) cancer cells with nominal effects in normal PBMC cells. To elucidate the possible mode of action of the cytotoxic behavior of the compounds, in silico docking studies have been carried out which revealed the efficient interaction of the compounds with the active sites of antiapototic cancer target proteins. The inhibitions of the activities of antiapoptotic target proteins have been further investigated using western blot analysis.

A methylenediphosphonate bridged copper(II) tetramer: Synthesis, structural, thermal, and magnetic characterization of [Cu4(H2O)2(phen)4(μ-P2O6CH2)2]·21H2O

A novel tetracopper(II) complex namely, [Cu4(H2O)2(phen)4(μ-P2O6CH2)2]·21H2O (1) was synthesized by using copper(II) chloride, 1,10-phenanthroline (phen), and methylene diphosphonic acid (MDP). The structure of 1 was characterized by single crystal X-ray diffraction and spectroscopy. Compound 1 crystallizes in the triclinic system, P1¯ space group and its crystal structure consists of neutral centrosymmetric tetranuclear copper(II)-methylene diphosphonate units where each peripheral {Cu(phen)(P2O6CH2)}2− fragment adopts the bidentate(Oeq-P-Oeq)/monodentate (Oax) bridging mode towards each of the two inner {Cu(phen)}2+ entities resulting in a “clamshell”-like orientation. The two crystallographically independent copper(II) ions in 1 (Cu1/Cu2) are five-coordinate with two nitrogen atoms from a bidentate phen molecule and two phophonate-oxygens building the basal plane (Cu1/Cu2) and either a water molecule (Cu2) or a phosphonate-oxygen (Cu1) filling the apical position of somewhat distorted square pyramidal surroundings. The values of the intramolecular copper–copper separation are 3.3219(8) and 3.2062(8) Å for Cu1⋯Cu2 and Cu1⋯Cu1i, respectively. Cryomagnetic measurements on a polycrystalline sample of 1 reveal the occurrence of an overall antiferromagnetic behaviour leading to a diamagnetic low-lying spin state. The values of the intramolecular magnetic interactions are J1 = −22.60(4) cm−1 (across the bis-bidentate methylene diphosphonate) and J2 = +4.9(3) cm−1 (through the double-oxo(phosphonate) bridge), the spin Hamiltonian being defined as H = −J1(SCu1·SCu2 + SCu1i·SCu2i) − J2(SCu1·SCu1i). These values are analyzed through simple orbital symmetry considerations and compared with those for related systems in the literature.

Decarboxylative Trifluoromethylating Reagent [Cu(O2 CCF3 )(phen)] and Difluorocarbene Precursor [Cu(phen)2 ][O2 CCF2 Cl

This article describes the new economic decarboxylative trifluoromethylating reagent [Cu(phen)(O2 CCF3 )] (1; phen=1,10-phenanthroline) and the efficient difluorocarbene precursor [Cu(phen)2 ][O2 CCF2 Cl] (2). Treatment of copper tert-butoxide with phen and subsequent addition of trifluoroacetic acid or chlorodifluoroacetic acid afforded air-stable complexes 1 and 2, respectively, which were characterized by X-ray crystallography. The copper(I) ion in 1 is coordinated by a bidentate phen ligand, a monodentate trifluoroacetate group, and a molecule of CH3 CN in a distorted tetrahedral coordination geometry. The molecular structure of 2 adopts an ionic form that consists of a [Cu(phen)2 ]+ cation and a chlorodifluoroacetate anion. Complex 1 reacted with a variety of aryl and heteroaryl halides to form trifluoromethyl (hetero)arenes in good yields. The corresponding Hammett plot exhibited a linear relationship and a reaction parameter (ρ)=+0.56±0.02, which indicated that the trifluoromethylation reaction proceeded via a nucleophilic reactive species. Complex 2 reacts with phenols to produce aryl difluoromethyl ethers in modest-to-excellent yields. Mechanistic investigations revealed that the difluoromethylation reaction proceeds by initial copper-mediated formation of difluorocarbene and subsequent concerted addition of difluorocarbene to the phenol to form a three-center transition state.

Structural diversity of lanthanum saccharinates induced by 1,10-phenanthroline: A synthetic and X-ray crystallographic study

Four new lanthanum(III) complexes of formulae [La(sac)3(phen)2(H2O)2]·(phen)(H2O)2 (1), [La(sac)3(phen)2(H2O)2]·(phen) (2), [La(sac)2(phen)(H2O)4]·(sac) (3) and [La(sac)2(phen)2(H2O)3]·(sac)(phen)(H2O) (4) (phen=1,10 phenanthroline, sac=saccharinate) have been synthesised and characterised by single crystal X-ray diffraction, IR, elemental analysis and thermogravimetric analysis. The binding mode of the sac anion was manipulated through the use of phen as structure inducer. In all four complexes the La(III) ion is in a nine-coordinate environment. The structures of 1 and 2 are similar, comprising of three sac anions coordinating in a monodentate fashion through the carbonyl O-atom, two bidentate phen and two water molecules coordinating directly to the same La(III) ion; a third, uncoordinated phen moiety also forms part of the unit cell. In addition, 1 is characterized by the presence of two crystallization water molecules which are absent in 2. In compound 3 the coordination sphere of La(III) is completed by a bidentate chelating sac through the N- and carbonyl O-atoms, a monodentate sac, a bidentate phen and four water ligands; a third, uncoordinated sac is also present in the crystal lattice. Compound 4 contains two bidentate phen, three water ligands and two monodentate O(carbonyl) sac ligands. The presence of three sac anions coordinating to the same lanthanide ion as well as a bidentate N–Ln–O chelating sac, confirmed by single crystal X-ray crystallography, is unprecedented for rare-earth saccharinates.

Synthesis, crystal structure, spectroscopic and biological properties of mixed ligand complexes of zinc(II) valproate with 1,10-phenanthroline and 2-aminomethylpyridine

Mononuclear zinc(II) complexes with mixed ligands formulating [Zn(valp)2(1,10-phen)H2O] (2), and [Zn(valp)(2-picam)2](valp) (3) (valp=valproate, phen=1,10-phenanthroline, 2-picam=2-aminomethylpyridine (2-picolylamine)) have been synthesized and characterized using IR, 1H NMR, 13C{1H} NMR and UV–Vis spectroscopic techniques, as well as single-crystal X-ray diffraction. Zn(II) cation in 2 exhibits a distorted octahedral environment resulting from one bidentate phen ligand, one valproate ligand with asymmetric chelating mode, and another one with monodentate mode and a molecule of water. Complex 3 has two bidentate 2-ampic ligands and two valproate ligands. Only one of the carboxylate ligands was bonded to Zn(II) in a monodentate mode. The second valproate ligand acted as a counter ion and was bonded to the NH2 groups of 2-picam through hydrogen bonding. The Zn(II) cation in 3 has a distorted trigonal bipyramidal arrangement. The complexes were also evaluated for their anti-bacterial activity using in vitro agar diffusion method. Three Gram-positive (Micrococcus luteus, Staphylococcus aureus, and Bacillus subtilis) and three Gram-negative (Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis) species of bacteria were used for testing anti-bacterial activities. Complex 2 showed considerable activity against all tested microorganisms. The effect of complexation on the anti-bacterial activity of the parent ligand of 2 was also investigated. The anti-bacterial activity of 1,10-phen against both Gram-positive and Gram-negative bacteria was reduced upon complexation with zinc valproate. Complex 3 showed weak inhibition activity against S. aureus, B. subtilis, E. coli and K. pneumoniae.

Synthesis, Characterization, Fluorescence and Antibacterial Activity of the Re(VII) Complex [ReO3(phen)(H2PO4)]・H2O

Single crystals of a Re(VII) complex, the dihydrogenophosphato phenanthroline trioxo-rhenium monohydrate of formula [ReO3(phen)(H2PO4)]⋅H2O (phen=1,10-phenanthroline), were prepared in aqueous solution. X-Ray analysis shows that it crystallizes in the monoclinic space group P21/c with the unit cell parameters: a=8.611(2), b=13.881(2), c=14.502(4) Å , β =120:87(2)°, V =1487.9(6) Å3 and Z = 4. In the neutral complex, the rhenium is in the oxidation state +VII, coordinated by two nitrogen atoms of the bidentate phen, three terminal oxygen atoms and, for the first time, one oxygen atom of the mono-deprotonated phosphoric acid ligand H2PO- 4 , forming a squarebased bipyramidal coordination geometry. The thermal stability, IR, UV/Vis and fluorescence spectroscopic properties are given. The complex shows antimicrobial activity against five different microbes.

Synthesis, X-ray structures, properties and SOD-like activity of ternary copper(II) complexes showing the N4O2 coordination with a combination of monodentate and bidentate N-donor ligands

A series of novel copper(II) complexes with the composition of [Cu(H2O)2(L1–5)2(phen)]·2MeOH (1–5), where HL1=6-(2-fluorobenzylamino)purine, HL2=6-(3-fluorobenzylamino)purine, HL3=6-(4-fluorobenzylamino)purine, HL4=6-(2-chlorobenzylamino)purine, HL5=6-(3-chlorobenzylamino)purine, phen=1,10-phenanthroline, was synthesized and characterized by elemental analysis, electronic and infrared spectroscopy, magnetic and conductivity measurements. Single-crystal X-ray analysis of complexes 1–4 showed the distorted octahedral geometry in the vicinity of the copper(II) atom, which is coordinated by four nitrogen atoms (two from the bidentate phen ligand and the other two from monodentate 6-(benzylamino)purine derivatives) and two oxygen atoms from the aqua ligands, which together form the N4O2 donor set. The antiradical activity of the prepared complexes was tested by an in vitro SOD-like assay. The IC50 values were found ranging between 104 and 146μM, which represents ca. 0.5% of the native bovine Cu, Zn-SOD effect.

A photochromic dinuclear compound: aquatetrakis(μ-2,3-diphenylprop-2-enoato)bis(2,3-diphenylprop-2-enoato)ethanolbis(1,10-phenanthroline)dilanthanum(III)

The title dinuclear complex, (aqua-1κO)tetrakis(μ-2,3-diphenylprop-2-enoato-1:2κ(2)O:O')bis(2,3-diphenylprop-2-enoato)-1κO;2κO-(ethanol-2κO)bis(1,10-phenanthroline)-1κ(2)N,N';2κ(2)N,N'-dilanthanum(III), [La(2)(C(15)H(11)O(2))(6)(C(12)H(8)N(2))(2)(C(2)H(5)OH)(H(2)O)], contains two similar La(III) centres with distorted [LaO(6)N(2)] bicapped triganol-prismatic coordination polyhedra formed by six phenylcinnamate (PCA(-) or 2,3-diphenylprop-2-enoate) ligands, two 1,10-phenanthroline (phen) ligands, a coordinating ethanol molecule and a coordinating water molecule. The two metal centres are bridged by four μ-PCA(-) ligands, with the remaining two PCA(-) ligands coordinated in a monodentate fashion. The noncoordinated carboxylate O atoms on the terminal PCA(-) ligands form O-H···O hydrogen bonds with the coordinated solvent molecules. Each La centre is also coordinated by a bidentate phen ligand. The PCA(-) ligands all adopt syn-syn orientations, with the two phenyl rings presenting dihedral angles of about 70°. The compound displays photochromic behaviour both in solution and in the solid state.

Chloridobis(1,10-phenanthroline-κ2N,N′)copper(II) tetrakis(nitrato-κ2O,O′)(1,10-phenanthroline-κ2N,N′)terbate(III)

The title complex salt, [CuCl(C12H8N2)2][Tb(NO3)4(C12H8N2)], consists of discrete [CuCl(phen))2]+ cations and [Tb(NO3)4(phen)]− anions (phen is 1,10-phenanthroline). The [CuCl(phen))2]+ cation contains a five-coordinate Cu2+ ion, ligated by two bidentate phen ligands and one Cl− ion, exhibiting a distorted CuN4Cl trigonal–bipyramidal geometry. In the [Tb(NO3)4(phen)]− anion, the Tb3+ ion is coordinated by one chelating phen ligand and four chelating nitrates, forming a distorted TbN2O8 bicapped dodeca­hedral configuration. The anions and cations are assembled into a three-dimensional network by weak C—H⋯Cl and C—H⋯O hydrogen bonds. There is also a significant π–π stacking inter­action, with a centroid–centroid distance of 3.635 (2) Å.

Speciation of cobalt, nickel and zinc-ethylenediaminediacetate complexes with N-heterocycle ligand – Synthesis, spectroscopic and structural studies

Cobalt, nickel and zinc N-heterocycle chelated ethylenediaminediacetates [Co(edda)(phen)]·(NH 4Cl)·1/3H 2O ( 1), [Ni(edda)(phen)]·3H 2O ( 2), [Co(edda)(bpy)]·(NH 4Cl)·2H 2O ( 3), [Ni(edda)(bpy)]·4H 2O ( 4), [Zn(edda)(bpy)]·4H 2O ( 5) (H 2edda = ethylenediaminediacetic acid, phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine) were isolated in pure forms and characterized spectroscopically. The X-ray structural analyses reveal that neutral mononuclear complexes contain both edda and phen/bpy ligands. Divalent metal ions are octahedrally bound by a bidentate phen or bpy ligand, and a tetradentately edda through carboxyl and amine groups. The co-existences of phen/bpy and edda in the complexes show no decomposition between phen/bpy and edda ligands. This is supported by the trace of 13C NMR spectra with less-bound zinc complex. Further comparisons of the bond distances between Co 2+/Ni 2+/Zn 2+ ions with edda indicate that cobalt and nickel interact much stronger than those of zinc complexes.

Crystal Structure, Spectroscopy and Crystal Field Analysis of Substituted 1,10‐Phenanthroline–Europium Complexes

AbstractCrystal structures and vibrational and electronic spectroscopic data are reported for europium(III) complexes with 5(or 4)‐R‐1,10‐phenanthroline (phen) ligands (R = chloro, methyl, nitro, amino). All complexes comprise a 10‐coordinate Eu3+ ion with three chelating nitrato anions and two bidentate phen ligands. The crystal structures are of three distinct types with space groups C2/c, P21/n and P. The room‐temperature emission spectra are dominated by the forced electric dipole 5D0 → 7F2 emission of Eu3+. The excitation spectra show that the triplet donor state of the nitro‐substituted complex has a lower energy than the other complexes and the lower luminescence quantum efficiency of this complex is rationalized. The emission spectra recorded at 10 K have been compared with those of the corresponding Eu3+‐doped yttrium complexes using different excitation lines as a criterion of sample purity. The spectrum of the unsubstituted phen complex is more clearly resolved than those of the other complexes and this has been attributed to disorder resulting in inhomogeneous broadening. A detailed crystal field analysis is given for the phen complex from the fitting of 24 crystal field energy levels. A comparison with other complexes has been made through derived second‐rank crystal field strengths. No simple relationships have been derived from comparisons of energy levels, spectral line positions, or second‐rank crystal field strengths with crystallographic data or Taft constants.

Low-temperature X-ray diffraction study of [CuII(1,10-C12H8N2)3]2+{CoIII[η5-(3)-1,2-C2B9H11]2} 2 − ·CH3CN

Single crystal XRD is used to study the crystal structure of a new compound containing the dicarbollyl cluster anion Co(III) with the composition [CuPhen3][Co(C2B9H11)2]2·CH3CN, where Phen is 1,10-phenanthroline. The crystallographic data: C46H71B36N7Co2Cu, M = 1292.66, monoclinic system, P21/c space group, unit cell parameters a = 14.7178(2) A, b = 19.5640(4) A, c = 22.8663(5) A, β = 106.6601(7)°, V = 6307.75(33) A3, Z = 4, dx = 1.361 g/cm3, T = 100 K, μ = 0.90 mm−1. The structure is solved by the direct method and refined by the full-matrix LSM in an anisotropic-isotropic (for H atoms) approximation up to the final agreement factors R1 = 0.0370, wR2 = 0.0869 for 13,807 Ihkl ≥ 2 σI out of 18,295 measured Ihkl. The structure consists of [CuPhen3] cations, Co(C2B9H11)2 anions, and acetonitrile molecules MeCN. The central Cu atom in the cation in the general position, and its coordination geometry is a distorted extended octahedron formed by six nitrogen atoms of the three bidentate Phen ligands. The coordination of Cu(II) in the cation is (2+2+2) with two long axial and four shorter equatorial Cu-N bonds, whose average lengths are 2.239(2) A and 2.077(1) A respectively. Each anion has its own position of the -C2-groups; for Co(1), it is a quasi-gauche-configuration; for Co(2), a quasi-trans-configuration.

Catena-Poly[[[(1,10-phenanthroline)copper(I)]-μ-cyanido] ethanol hemisolvate

In the title coordination polymer, {[Cu(CN)(C12H10N2)]·0.5C2H5OH}n, there are two CuI ions, two 1,10-phenanthroline (phen) ligands and two cyanide ions in the asymmetric unit along with a highly disordered ethanol solvent mol­ecule, which was modelled as being disordered over two sets of sites in a 0.829 (7):0.171 (7) ratio. The orientation/ordering of the C and N atoms of the cyanide ions could not be determined in the present refinement and they were modelled as being statistically disordered. Both copper ions are coordinated by an N,N′-bidentate phen ligand and two cyanide ligands, generating distorted tetra­hedral CuN2 Q 2 (Q = C or N) tetra­hedra. The μ-cyanide ligands link the metal ions, forming a zigzag chain propagating in [001]. The chains are cross-linked by numerous aromatic π–π stacking contacts between adjacent phen rings [minimum centroid–centroid separation = 3.620 (3) Å].

DNA photocleavage and anticancer activity of terpyridine copper(II) complexes having phenanthroline bases

Copper(II) complexes [Cu(ph-tpy)(B)](ClO 4) ( 1– 3), where ph-tpy is (4′-phenyl)-2,2′:6′,2″-terpyridine and B is N, N-donor phenanthroline base, viz. 1,10-phenanthroline (phen, 1), dipyridoquinoxaline (dpq, 2), and dipyridophenazine (dppz, 3), were prepared and characterized from analytical and spectral data. Complex 1, characterized by X-ray crystallography, shows a distorted square-pyramidal (4 + 1) CuN 5 coordination geometry having the tridentate ph-tpy ligand at the basal plane and bidentate phen bound to the axial-equatorial sites. The complexes display a d– d band near 650 nm in aqueous DMF. The complexes are avid binders to calf thymus DNA giving the binding order: 3 (dppz) > 2 (dpq) > 1 (phen). The dpq and dppz complexes show photo-induced DNA cleavage activity in red light via photo-redox pathway forming hydroxyl radicals. The cytotoxicity of the dppz complex 3 was studied by MTT assay in HeLa cancer cells. The IC 50 values are 3.7 and 12.4 μM in visible light of 400–700 nm and dark, respectively.

Synthesis and Properties of Dinuclear Ru(II)/Os(II) Complexes Based on a Heteroditopic Phenanthroline−Terpyridine Bridging Ligand

The synthesis and characterization of a series of mono- and dinuclear ruthenium(II) and osmium(II) polypyridyl complexes based on the heteroditopic bridging ligand PT are reported. This ligand incorporates bidentate phen (1,10-phenanthroline) and terdentate tpy (2,2':6',2''-terpyridine) units directly connected by their 3 and 5 positions, respectively. The dinuclear complexes have been synthesized via a Pd(0) catalyzed cross-coupling reaction between a bromo-substituted Ru-phen complex and a tpy derivative incorporating a boronate ester, followed by Ru(II) or Os(II) complexation. The compounds obtained are fully characterized using spectroscopic and electrochemical measurements. The electrochemical studies do not yield any evidence for interaction between the two metal centers in the dinuclear compounds. Emission studies indicate, however, energy transfer from the phen moiety to the tpy center. For the ruthenium/osmium species, this process is relatively slow, resulting in a dual emission. The emission of the mononuclear ruthenium compound is enhanced by the addition of Zn(II).

Synthesis, spectroscopic, thermal, crystal characterization and biological activity of [Ni(phen)3][Ni(dipic)2]2.17H2O (H2dipic:pyridine-2,6-dicarboxylic acid, phen: 1,10-phenanthroline)

The new [Ni(phen)3][Ni(dipic)2]2.17H2O (1) (phen = 1,10-phenanthroline, dipic = dipicolinate)) has been prepared and characterized by elemental analysis, IR, UV-Vis, magnetic measurement and single crystal X-ray diffraction. The complex consists of two tris(1,10-phenanthroline)nickel(II) cations, two bis(dipicolinato)nickelate(II) anions and seventeen uncoordinated water molecules. The Ni(II) complex crystallizes in the triclinic space group P-1. The complex consisting of cation has distorted octahedral coordination by three bidentate phen ligands. In the complex anion, each dipic ligand simultaneously exhibits tridentate coordination modes through N atom of pyridine ring and oxygen atoms of the carboxylate groups. The crystal packing of 1 is a composite of intermolecular hydrogen bonding, π-π and C-Hπ interactions. The complex has also been investigated in terms of biological activity and it showed high activity against S. aureus from Gram positive bacteria and C. albicans from yeast tested.

Synthesis, Crystal Structure and IR Spectra of Complexes of Mn(II) by Indole-2-Carboxylic or Isoquinoline-1-Carboxylic Acids and 1,10-Phenanthroline

Two ternary complexes of manganese(II) indole-2-carboxylate (2-IC−) or isoquinolinecarboxylate (IQC−) with 1,10-phenanthroline (phen) in methanol or in dimethylacetamide (DMA) were synthesized and studied by X-ray diffraction and IR spectra. [Mn(C9H6NO2)2(C12H8N2)2]·CH4O (1) crystallizes in the triclinic space group P-1 with cell parameters of a = 10.548(2) A, b = 14.168(3) A, c = 14.580(3) A, α = 62.35(2)°, β = 69.16(2)°, γ = 78.61(2)°, V = 1802.4(6) A3 and Z = 2; [Mn(C10H6NO2)2(C12H8N2)].C4H9NO (2) crystallizes in the monoclinic space group P21/a with cell parameters of a = 15.304(5) A, b = 12.871(5) A, c = 17.421(5) A, β = 114.39(1), V = 3125(2) A3 and Z = 4. In 1, Mn is six-coordinate by two bidentate phen ligands and two 2-IC− ligands and exhibits a very distorted octahedral geometry. This complex is solvated by methanol involved in hydrogen bonding. In 2, Mn atom is surrounded by one bidentate phen ligand and two bidentate IQC− ligands. The complex exhibits a distorted octahedral geometry around the MnII atom. The crystal structure is completed by a disordered DMA solvate molecule. The IR spectra of both compounds are slightly different in the range 4000–2400 cm−1 which may be attributed to hydrogen bond lack in 2. Two ternary complexes of manganese(II) indole-2-carboxylate (2-IC−) or isoquinolinecarboxylate (IQC−) with 1,10-phenanthroline (phen) in methanol or in dimethylacetamide (DMA) were synthesized, their X-ray crystal structures were determined and some IR spectra were recorded.

Photocytotoxicity and DNA cleavage activity of l-arg and l-lys Schiff base oxovanadium(iv) complexes having phenanthroline bases

Oxovanadium(IV) complexes [VO(sal-argH)(B)]Cl (1-3) and [VO(sal-lysH)(B)]Cl (4-6), where sal-argH2 and sal-lysH2 are N-salicylidene-L-arginine and N-salicylidene-L-lysine Schiff bases and B is a phenanthroline base, viz. 1,10-phenanthroline (phen in 1 and 4); dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in 2 and 5) and dipyrido[3,2-a:2',3'-c]phenazine (dppz in 3 and 6), have been prepared, characterized and their DNA photocleavage activity studied. Complex 1, characterized by X-ray crystallography, shows the presence of a vanadyl group in V(IV)O3N3 coordination geometry with a tridentate Schiff base having a pendant guanidinium moiety and bidentate phen ligand. The complexes exhibit a d-d band at 715 nm in 20% DMF-Tris-HCl buffer. The complexes are redox active showing cathodic and anodic responses near -1.0 V and 0.85 V (vs. SCE) for the V(IV)-V(III) and V(V)-V(IV) couples, respectively, in DMF-Tris-HCl buffer. The complexes bind to calf thymus DNA giving Kb values in the range of 3.8 x 10(4) to 1.6 x 10(5) M(-1). Thermal denaturation and viscosity data suggest DNA groove binding nature of the complexes. The complexes do not show any "chemical nuclease" activity in dark in the presence of 3-mercaptopropionic acid or H2O2. The dpq and dppz complexes are efficient photocleavers of plasmid DNA in UV-A (365 nm) and red light (676 nm) via singlet oxygen pathway. The dppz complexes exhibit photocytotoxicity in HeLa cancer cells giving IC50 values of 15.4 microM for 3 and 17.5 microM for 6 in visible light while being non-toxic in dark giving IC50 values of >100 microM.

Fe(phen)(CN)4]−: a suitable metalloligand unit to build 3d–4f heterobimetallic complexes with mixed bpym-cyano bridges (phen = 1,10-phenantroline, bpym = 2,2′-bipyrimidine)

The synthesis, crystal structure and magnetic properties of a new series of mixed 3d–4f complexes with the formula [{FeIII(phen)(CN)3(μ-CN)}4Ln2III(NO3)2(H2O)6(μ-bpym)]·nH2O [Ln = Eu (1), Gd (2), Dy (3) and Ho (4); n = 8 (1, 3 and 4) and 11 (2); phen = 1,10-phenantroline; bpym = 2,2′-bipyrimidine] are discussed here. Compounds 1–4 are centrosymmetric hexanuclear species whose structure is made up of two cyano-bridged {Fe2IIILnIII} heterobimetallic moieties which are connected through a bis-bidentate bpym molecule between the two rare-earth centers. The values of the iron–lanthanide distance across the single cyano-bridge are Fe(1)⋯Eu(1) = 5.5587(8) and Fe(2)⋯Eu(1) = 5.4908(8) A (1), Fe(1)⋯Gd(1) = 5.5456(6) and Fe(2)⋯Gd(1) = 5.4831(6) A (2), Fe(1)⋯Dy(1) = 5.5223(7) and Fe(2)⋯Dy(1) = 5.4509(7) A (3) and Fe(1)⋯Ho(1) = 5.5094(12) and Fe(2)⋯Ho(1) = 5.4420(14) A (4), whereas those of the lanthanide–lanthanide separation through the bpym bridge are 6.8196(8) (1), 6.7971(6) (2), 6.7511(7) (3) and 6.7395(6) A (4). The two crystallographically independent iron(III) ions in 1–4 are six-coordinated with two nitrogen atoms from a bidentate phen ligand and four carbon atoms from four cyanide groups building somewhat distorted octahedral surroundings. The trivalent lanthanide cations in 1–4 are nine-coordinated with two bpym and two cyano-nitrogen atoms, three water molecules and a chelating nitrate describing distorted monocapped square antiprism environments. Compounds 1–4 are isomorphous species where the neutral hexanuclear motifs are assembled through an extensive network of hydrogen bonds involving all the water molecules to afford a supramolecular three-dimensional structure. Interestingly, the crystal packing of 2 shows the occurrence of unprecedented centrosymmetric twelve-atom water aggregates which are integrated by two interlinked pentanuclear water rings, each one having a dangling water molecule. The investigation of the magnetic properties of 1–4 in the temperature range 1.9–300 K reveals the presence of intramolecular magnetic interactions for 2–4 [antiferro- (through single cyano and bpym bridges) in 2 and ferromagnetic (across single cyano and/or bpym bridges) in 3 and 4] whereas the magnetic behaviour of 1 corresponds to that of the magnetically isolated low-spin iron(III) and europium(III) centers.

“Living” radical polymerization of styrene catalyzed by cyclometalated ruthenium(II) complexes bearing nonlabile ligands

AbstractCationic substitutionally inert cyclometalated ruthenium (II) and osmium (II) complexes, ([Mt(o‐C6H4‐2‐py)(LL)2]PF6), where LL‐1,10‐phenanthroline (phen) or 2,2′‐bipyridine (bipy), were used for radical polymerization of styrene. Gradual modification of the complexes within the series allowed comparison of the catalytic activity and the redox properties. There was no correlation between the reducing powers of the complexes and their catalytic activities. The osmium compound of the lowest reduction potential was not active. All the ruthenium complexes catalyzed the polymerization of styrene in a controlled manner; but the level of control and the catalytic activity were different under the same polymerization conditions. [Ru(o‐C6H4‐2‐py)(phen)2]PF6 demonstrated the best catalytic performance though its redox potential was the highest. It catalyzed the “living” polymerization with a reasonable rate at a catalyst‐to‐initiator ratio of 0.1. 1 equiv. of Al(OiPr)3 accelerated the polymerization and improved the control, but higher amount of Al(OiPr)3 did not speed up the polymerization and moved the process into the uncontrollable regime. Under the most optimal conditions, the controlled polymerization occurs fast without any additive and the catalyst degradation. Added free ligands inhibited the polymerization suggesting that the catalytically active ruthenium intermediates are generated via the reversible dechelation of bidentate phen or bipy ligands. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3814–3828, 2009