Synthesis and crystal structure of dinuclear nickel (Ⅱ) complex

The crystal structure of Ni(Ⅱ) complex with 3-hydroxyl-1, 5-diazacycloheptane-N, N'-diacetate was determined by X-ray diffraction method. Crystal data for Ni2 (C9H14N2O5)2·2H2O: monoclinic, space group P21/n, a = 1.1717(5), b = 0.9794(3), c = 1.2971(2) nm, β= 96.62(3), V= 1.4786(7) nm3, Dc = 1.377 g/cm3, Z = 2,μ=13.321 cm-1 (Mo-Kα), F(000)=640. The final R and Rw are 0.075 and 0.089 respectively. The Ni(Ⅱ) ion forms 2:2 complex with ligand. Two ligands are bridged by two Ni(Ⅱ) atoms which are bridged by two O atoms. Every Ni(Ⅱ) is coordinated by two N atoms and four 0 atoms. The coordination polyhedron of the Ni(Ⅱ) ion is a distorted octahedron.     

Bent dinuclear platinum(II) halo-bridged carbonyl complexes

Crystals of trans-Pt?(μ-X)?X?(CO)? (X = Br, I) have been grown and their molecular and crystalline structures have been solved by X-ray diffraction methods. In both cases the dinuclear molecules are bent, with a bending angle of 164.6° and 156.5° for the bromide and the iodide, respectively. While the structure of the bromo-derivative is reported here for the first time, a modification of trans-Pt?(μ-I)?I?(CO)? with planar centrosymmetric molecules is known. This appears to be a rare case of a platinum(II) halo-bridged derivative structurally characterized in both bent and planar forms.     

Synthesis of pendant-type anthraquinone-bridged cofacial dinuclear platinum(II) complexes and their emission properties

Anthraquinone-bridged mononuclear and dinuclear complexes, [PtCl(AQ-amide-tpy)](PF6) (1), [Pt2Cl2(AQ-amide-tpy2)](PF6)2 (2), and [Pt2Cl2(AQ-eth-tpy2)](PF6)2 (3), were synthesized and their photochemical properties were investigated. Amide-bound mononuclear complex 1 exhibited only metal-to-ligand charge transfer (MLCT) absorption and emission, whereas dinuclear complex 2 exhibited a low-energy emission around 700 nm at room temperature. Emission lifetime analysis indicated that this emission was originated from the metal-metal-to-ligand charge transfer (MMLCT) excited state, implying the existence of an intramolecular Pt-Pt interaction at the photoexcited state. 3 with rigid ethynylene linkers showed a low-energy absorption around 520 nm (epsilon = approximately 1100 M(-1) cm(-1)) in addition to an 1MLCT absorption, which was ascribed to a 3MLCT absorption from the consideration of the Pt-Pt distance on a geometry-optimized structure. The emission of 3 appeared at 600 nm, which is higher in energy compared with the emission of 2. It is postulated that the restriction of the Pt-Pt distance flexibility in the rigid structure of 3 prevents the significant increase of the Pt-Pt interaction at the excited state.     

Synthesis and DNA-binding properties of dinuclear platinum(II)-amine complexes of 1,7-dicarba-closo-dodecaborane(12)

The first examples of platinum(II)-amine complexes containing a dicarba-closo-dodecaborane(12) (carborane) moiety are described; preliminary in vitro DNA-binding experiments indicate that the complexes are capable of targetting plasmid DNA.     

Interactions of nitrogen-donor bio-molecules with dinuclear platinum(II) complexes

Substitution reactions of the dinuclear Pt(II) complexes, [{Pt(en)Cl}₂(μ-pz)]²⁺ (1), [{Pt(dach)Cl}₂(μ-pz)]²⁺ (2) and [{Pt(dach)Cl}₂(μ-4,4?-bipy)]²⁺ (3), and corresponding aqua analogs with selected biologically important ligands, viz. 1,2,4-triazole, L-histidine (L-His) and guanosine-5?-monophosphate (5?-GMP) were studied under pseudo-first-order conditions as a function of concentration and temperature using UV–vis spectrophotometry. The reactions of the chloride complexes were followed in aqueous 25 mmol L^?1 Hepes buffer in the presence of 40 mmol L^?1 NaCl at pH 7.2, whereas the reactions of the aqua complexes were studied at pH 2.5. Two consecutive reaction steps, which both depend on the nucleophile concentration, were observed in all cases. The second-order rate constants for both reaction steps indicate a decrease in the order 1 > 2 > 3 for all complexes. Also, the pK_a values of all three aqua complexes were determined. The order of the reactivity of the studied ligands is 1,2,4-triazole > L-His > 5?-GMP. ¹H NMR spectroscopy and HPLC were used to follow the substitution of chloride in the dichloride 1, 2, and 3 complexes by guanosine-5?-monophosphate (5?-GMP). This study shows that the inert and bridging ligands have an important influence on the reactivity of the studied complexes.     

Synthesis and characterization of dinuclear pyrazolato bridged platinum(IV) complexes

Reactions of [PtMe₃(OCMe₂)₃](BF₄) and [(PtMe₃I)₄] with pyrazole (pzH) afforded mononuclear pyrazole platinum(IV) complexes [PtMe₃(pzH)₃](BF₄) (1) and [PtMe₃I(pzH)₂] (2), respectively. The formation of dinuclear pyrazolato bridged platinum(IV) complexes (PPN)[(PtMe₃)₂(μ-pz)₃] (3), (PPN)[(PtMe₃)₂(μ-I)(μ-pz)₂] · 1/2Et₂O (4) and [K(18C6)][(PtMe₃)₂(μ-I)(μ-pz)₂] (5) was achieved by the reaction of each 1 and 2 with [PtMe₃(OCMe₂)₃](BF₄) in the presence of KOAc followed by reaction with (PPN)Cl (PPN⁺ = bis(triphenylphosphine)iminium cation) and 18C6, respectively. The reaction of complex 4 with AgO₂CCF₃ followed by addition of RSR′ (R/R′ = Me/Me, Me/Ph) resulted in the formation of complexes [(PtMe₃)₂(μ-pz)₂(μ-RSR′)] (R/R′ = Me/Me, 6; Me/Ph, 7). All complexes were characterized unambiguously by microanalysis and NMR (¹H, ¹³C) spectroscopic investigations. Additionally, crystal structures of complexes 3 and 4 as well as DFT calculation are presented. Furthermore, in vitro studies on the anti-proliferative activity of complexes 2 and 5 were carried out.     

Synthesis,crystal structure and fluorescence properties of two dinuclear zinc(II) complexes incorporating tridentate (NNO) Schiff bases

Reactions of hydrated zinc(II) trifluoroacetate and sodium azide with two tridentate Schiff bases HL¹ (2-((E)-(2-(dimethylamino)ethylimino)methyl)-4-chlorophenol) and HL² (2-((E)-(2-(dimethylamino)ethylimino)methyl)-4-bromophenol) under the same reaction conditions yielded two dinuclear isostructural zinc(II) complexes, [Zn(L¹)(N₃)]₂ (1) and [Zn(L²)(N₃)]₂ (2), respectively. The complexes were characterized systematically by elemental analysis, UV–Vis, FT-IR, and ¹H NMR spectroscopic methods. Single-crystal X-ray diffraction studies reveal that each of the dinuclear complexes consists of two crystallographically independent zinc(II) ions connected by double bridging phenoxides. All zinc(II) ions in 1 and 2 are surrounded by similar donor sets and display distorted square–pyramidal coordination geometries. The ligands and complexes reveal intraligand ¹(π → π*) flourescence. The enhancement of the fluorescence intensities for the complexes compared to the ligands indicates their potential to serve as photoactive materials.     

Synthesis,crystal structures and phosphodiesterase activities of alkoxide-bridged asymmetric dinuclear nickel(II) complexes

An asymmetric dinuclear ligand, N-4-methyl-homopiperazine-N′-[N-(2-pyridylmethyl)-N-2-(2-pyridylethyl)amine]-1,3-diaminopr-opan-2-ol (HL) and two dinuclear Ni(II) complexes [Ni₂L(DNBA)₂]ClO₄ (1) and [Ni₂L(BPP)₂]ClO₄·2H₂O (2) (3,5-dinitrobenzoic acid, bisphenyl phosphate) have been synthesized and characterized. Single crystal X-ray crystallographic analysis reveals that the coordination environments of the two Ni(II) atoms in complexes 1 and 2 are five and six coordinate, respectively. The phosphodiesterase activity of a di-Ni(II) complex Ni₂L formed in situ from a 2:1 mixture of Ni²⁺ and HL was investigated using bis(4-nitrophenyl) phosphate (BNPP) as the substrate. The pH dependence of the rate of BNPP cleavage in aqueous buffer indicates a bell-shaped profile with an optimum at about pH 8.4, which is parallel to the formation of the dinuclear species [Ni₂LOH]²⁺ according to UV–vis spectroscopy. At pH 8.4 and 25 °C, the k _cat (7.40 × 10^?5 s^?1) is ca.10⁶-fold higher than that of the uncatalyzed reaction. A possible mechanism for BNPP cleavage promoted by Ni₂L is proposed.     

Synthesis and crystal structures of phenylalanine ester-introduced palladium(II) and platinum(II) complexes and their cytotoxicities

Research on Chemical Intermediates - Phenylalanine ester-introduced palladium(II) and platinum(II) complexes were synthesized. Taking advantage of the formation of Schiff bases by amino acids as an...     

Synthesis and anti-cancer activity of dinuclear platinum(II) complexes containing bis(thioalkyl)dicarba-closo-dodecaborane(12) ligands

A series of novel, dinuclear (2,2':6',2'-terpyridine)platinum(ii) complexes containing bis(thioalkyl)-dicarba-closo-dodecaborane(12)(carborane) ligands were prepared and characterised, and their preliminary anti-cancer characteristics have been determined in vitro; the complexes are the first examples of bis-intercalator complexes containing a boron-rich carborane cage.     

Novel dinuclear platinum(II) complexes containing mixed nitrogen-sulfur donor ligands

A series of novel dinuclear platinum(II) complexes were synthesized containing a mixed nitrogen-sulfur donor bidentate chelate system in which the two platinum centers are connected by an aliphatic chain of variable length. The bidentate chelating ligands were selected to stabilize the complex toward decomposition. The pK(a) values and reactivity of the four synthesized complexes, namely, [Pt(2)(S(1),S(4)-bis(2-pyridylmethyl)-1,4-butanedithioether)(OH(2))(4)](4+) (4NSpy), [Pt(2)(S(1),S(6)-bis(2-pyridylmethyl)-1,6-hexanedithioether)(OH(2))(4)](4+) (6NSpy), [Pt(2)(S(1),S(8)-bis(2-pyridylmethyl)-1,8-octanedithioether)(OH(2))(4)](4+) (8NSpy), and [Pt(2)(S(1),S(10)-bis(2-pyridylmethyl)-1,10-decanedithioether)(OH(2))(4)](4+) (10NSpy), were investigated. This system is of special interest because only little is known about the substitution behavior of dinuclear platinum complexes that contain a bidentate chelate that forms part of the aliphatic bridging ligand. Moreover, the ligands as well as the dinuclear complexes were examined in terms of their cytotoxic activity, and the 10NSpy complex was found to be active. Spectrophotometric acid-base titrations were performed to determine the pK(a) values of all the coordinated water molecules. The substitution of coordinated water by thiourea was studied under pseudo-first-order conditions as a function of nucleophile concentration, temperature, and pressure, using stopped-flow techniques and UV-vis spectroscopy. The results for the dinuclear complexes were compared to those for the corresponding mononuclear reference complex [Pt(methylthiomethylpyridine)(OH(2))(2)](2+) (Pt(mtp)), by which the effect of the increasing aliphatic chain length of the bridged complexes could be investigated. The results indicate that there is a clear interaction between the two platinum centers, which becomes weaker as the chain length between the metal centers increases. Furthermore, differences and similarities of the N,S-system were compared to the corresponding dinuclear N,N-system studied previously in our group. In addition, quantum chemical calculations were performed to support the interpretation and discussion of the experimental data.     

Syntheses, crystal structure and spectroscopic characterization of new platinum(II) dithiocarbimato complexes

The reaction of 4-iodobenzenesulfonamide or 4-fluorobenzenesulfonamide with CS₂ and KOH in dimethylformamide yielded the potassium N-R-sulfonyldithiocarbimates, K₂(RSO₂NCS₂) [R = 4-IC₆H₄ (1) and 4-FC₆H₄ (2)]. These salts reacted with K₂[PtCl₄] in water/methanol to yield complex anions bis(N-R-sulfonyldithiocarbimato)platinate(II), which were isolated as their tetrabutylammonium salts, (Bu₄N)₂[Pt(RSO₂NCS₂)₂] [R = 4-IC₆H₄ (3) and 4-FC₆H₄ (4)]. The structures of 2–4 were determined by X-ray crystallography. The Pt²⁺ in both complexes 3 and 4 lies at the inversion centre and the PtS₄ moiety has a distorted square-planar configuration. The compounds were also characterized by IR, ¹H NMR and ¹³C NMR spectroscopies, and elemental analyses. The molar conductance data are consistent with the fact that 3 and 4 are dianionic complexes.     

Synthesis, characterization, and electrochemical relationships of dinuclear complexes of platinum(II) and platinum(III) containing ortho-metalated tertiary arsine ligands

Reaction of 2-Li-4-MeC6H3AsPh2 with [PtCl2(SEt2)2] gives two isomeric dinuclear platinum(II) complexes, one containing a half-lantern structure with two chelating and two bridging C6H3-5-Me-2-AsPh2 ligands, [Pt2(kappa2As,C-C6H3-5-Me-2-AsPh2)2(mu-kappaAs,kappaC-C6H3-5-Me-2-AsPh2)2], and the other, a full-lantern with four bridging C6H3-5-Me-2-AsPh2 ligands, [Pt2(mu-kappaAs,kappaC-C6H3-5-Me-2-AsPh2)4]. The lantern structure of the latter is retained in the dihalodiplatinum(III) complexes that are formed by oxidative addition of chlorine, bromine, or iodine to the isomeric mixture. The dichloro derivative undergoes metathesis reactions with silver or sodium salts, yielding the corresponding cyano, thiocyanato, cyanato, and fluoro species. The structures of all complexes have been determined by single-crystal X-ray analysis. The oxidative addition products have Pt-Pt distances in the range 2.65-2.79 A (cf. 2.89 A in the lantern diplatinum(II) structure), consistent with the presence of a Pt-Pt bond. Electrochemical data lead to the conclusion that an initial rapid one-electron process and subsequent chemical reactions produce the dihalodiplatinum(III) lantern structure when mixtures of the lantern and half-lantern complexes are oxidized by halogens. The electrochemical data also explain why chemical reduction of the dihalodiplatinum(III) complex produces only the lantern diplatinum(II) complex.     

Synthesis and characterization of platinum(II) complexes with 2-imidazolidinethione. X-ray crystal structure of tetra(2-imidazolidinethione- S )platinum(II) iodide dimethylsulfoxide solvate monohydrate

Preparations of trans-[PtX₂(Imt)₂] (Imt =?2-imidazolidinethione, X=Cl^? or I^?) and [Pt(Imt)₄]I₂ are described. These complexes were characterized by elemental analysis, thermal analysis, mid- and far-IR spectroscopy, and NMR (¹H and ¹³C) spectroscopy. The crystal and molecular structure of [Pt(Imt)₄]I₂ ·?DMSO ·?H₂O was determined by X-ray diffraction methods. The structural data reveal the following features: (a) the platinum atom in [Pt(Imt)₄]²⁺ is essentially in a square-planar environment, (b) the entire dication possesses approximately C _2h symmetry, (c) no appreciable hydrogen bonding exists between the iodide ions and the Imt ligands in the dication, (d) two pairs of two mutually cis Imt ligands are arranged above and below the PtS₄ plane, respectively, and (e) two planes defined by two trans Imt rings are perpendicular to each other.     

Synthesis and in vitro cytotoxicity of novel dinuclear platinum(II) complexes containing a chiral tetradentate ligand

A series of novel dinuclear platinum(II) complexes with a chiral tetradentate ligand, (1R,1′R,2R,2′R)-N¹,N¹′-(1,2-phenylenebis(methylene))dicyclohexane-1,2-diamine (HL), and mono-carboxylic acid derivatives as ligands have been designed, synthesized, and characterized. In vitro cytotoxicity evaluation of synthesized complexes against human HepG-2, A549, HCT-116, and MCF-7 cancer cell lines has been conducted by MTT assays. All compounds showed antitumor activity to HepG-2 and HCT-116 cell lines. Compound L2 exhibited better cytotoxicity than that of carboplatin against HepG-2 and A549 cell lines and also showed comparable activity against HCT-116 cell line.     

Synthesis and X-ray crystal structure of cis-dichloro(cyclopentylamine) (dimethyl sulphoxide)platinum(II)

Summary cis-Dichlorocyclopentylamine(dimethyl sulphoxide)-platinum(II) is obtained, in addition to small quantities of the corresponding trans compound, by reaction of K₂PtCl₄ with cyclopentylamine in DMSO solution, where it is formed as the thermodynamically favoured isomer. An X-ray crystal structure analysis confirms the cis configuration. Coordination around the metal centre is square planar, and the ligand bond angles at the Pt atom are close to the expected values of 90 and 180°. The DMSO ligand is S-coordinated to Pt. The Pt-Cl bond lengths, 2.299(2) and 2.317(2) Å, are normal for structures of this type, as are the Pt-N and Pt-S bond distances, 2.059(5) and 2.191(2) Å, respectively.Author to whom all correspondence should be directed.     

Acid Co(II) and Ni(II) trifluoroacetate complexes: Synthesis and crystal structure

Anhydrous and partially hydrated acid trinuclear trifluoroacetates of divalent transition metals of the composition [M₃(CF₃COO)₆(CF₃COOH)₆)](CF₃COOH) and [M₃(CF₃COO)₆(CF₃COOH)₂(H₂O)₄)](CF₃COOH)₂, respectively, where M = Co (I, III) Ni (II, IV), were synthesized and studied by X-ray diffraction. Complexes I and II were obtained by crystallization from solutions of M(CF₃COO)₂ · 4H₂O in trifluoroacetic anhydride; complexes III and IV were synthesized under the same conditions with the use of 99% trifluoroacetic acid as a solvent. Crystals I are triclinic: space group $P\bar 1$ , a = 13.199(6) Å, b = 14.649(6) Å, c = 15.818(6) Å, α = 90.04(4)°, β = 114.32(4)°, γ = 108.55(4)°, V = 2611.3(19) ų, Z = 2, R = 0.0480. Crystals II are trigonal: space group $R\bar 3$ , a = 13.307(2) Å, c = 53.13(1) Å, V = 8148(2) ų, Z = 6, R = 0.1112. Crystals III are triclinic: space group $P\bar 1$ , a = 9.001(8) Å, b = 10.379(9) Å, c = 12.119(9) Å, α = 83.67(5)°, β = 72.33(5)°, γ = 83.44(5)°, V = 1068.3(15) ų, Z = 1 Å, R = 0.1031. Crystals IV are triclinic: space group $P\bar 1$ , a = 9.121(18) Å, b = 10.379(2) Å, c = 12.109(2) Å, α = 84.59(3)°, β = 72.20(3)°, γ = 82.80(3)°, V = 1080.94(40) ų, Z = 1, R = 0.0334.     

Synthesis,characterization, crystal structure and antiproliferative activity of platinum(II) complexes with 2-acetylpyridine-4-cyclohexyl-thiosemicarbazone

New platinum complexes have been synthesized by the reaction of Na₂PtCl₄ with 2-acetylpyridine-4-cyclohexyl-thiosemicarbazone, HAc4CyclHexyl (1). The new complexes [Pt(Ac4CyclHexyl)Cl] (2) and [Pt(Ac4CyclHexyl)₂] (3) have been characterized by elemental analyses and spectroscopic studies. The crystal structure of the complex [Pt(Ac4CyclHexyl)Cl] · DMF has been solved by single-crystal X-ray diffraction. The anion of Ac4CyclHexyl coordinates in a planar conformation to the central platinum(II) through the pyridyl N, azomethine N and thiolato S atoms. The crystal packing is determined by double intermolecular hydrogen interactions, π–π, Pt–C and Pt–π contacts. The cytotoxic activities of 1–3 have been evaluated for antiproliferative activity in vitro against the cells of three human cancer cell lines: MCF-7 (human breast cancer cell line), T24 (bladder cancer cell line), A-549 (non-small cell lung carcinoma) and a mouse L-929 (a fibroblast-like cell line cloned from strain L). The compounds 1–3 display IC₅₀ values in a μM range better than that of the antitumor drug cisplatin and are considered as agents with potential antitumor activity candidates for further stages of screening in vitro and/or in vivo.     

Synthesis and X-ray crystal structure of oxamido-bridged heterobinuclear Ni(Ⅱ)-Cu(Ⅱ) complexes

The two complexes [Ni(oxen)Cu(L)2](ClO4)2.xH2O (L=2,2'-bipyridyl(bpy), 1,10-phenanthroline(phen)) have been synthesized, where oxen is N,N'-bis(2-aminoethyl)oxamido di-anion. The crystal structure of [Ni(oxen)Cu(bpy)2](ClO4)2.CH3OH has been determined by X-ray diffraction method. The crystal is triclinic system, space group P1 with a=12.179(1),b=12.298(2), c=11.476(2) A, a=97.57(1), B=97.52(1), 7=80.29(2), V=1669.04(67) A3, Z=2, Dcalcd=1.667 g/cm3. The structure has been refined to final R of 0.076 and Rw of 0.080, respectively. The complexes have an extended oxamido-bridged structure and consist of Ni(Ⅱ) ion in a square planar environment and Cu(Ⅱ) ion in a distorted octahedral environment.