Novel antitumor dinuclear platinum (II) complexes with a new chiral tetradentate ligand as the carrier group

Seven dinuclear platinum(II) complexes with a novel chiral tetradentate ligand, (1R,1′R,2R,2′R)‐N¹,N^1′‐(1,4‐phenylenebis(methylene))dicyclohexane‐1,2‐diamine, were designed, synthesized and spectrally characterized. All the complexes were evaluated for their in vitro cytotoxicity against human HepG‐2, A549, HCT‐116 and MCF‐7 cancer cell lines. The results indicated that all compounds showed positive biological activity against HepG‐2, A549 and HCT‐116 cancer cell lines. In particular, compounds D7 and D2 showed better activity than carboplatin against HepG‐2 and A549 and compound D7 also showed an activity close to that of oxaliplatin. Copyright © 2015 John Wiley & Sons, Ltd.     

Self-assembly as a route to dinuclear lanthanide complexes with rare coordination pattern of salen-type ligand

The self-assembled formation of dinuclear lanthanide salicylaldimines is proved by the X-ray diffraction analysis of europium and gadolinium nitrate complexes containing N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine (H₂L). The [Eu₂(H₂L)₂(μ-H₂L)₂(NO₃)₆] complex, isostructural with the gadolinium complex, displays nine-coordinate distorted tricapped trigonal prism geometry with a different coordination mode of four undeprotonated salicylaldimines, which act as terminal monodentate and μ-bridging ditopic ligands using exclusively the oxygens as donor atoms with the nitrogen atoms not being involved in the coordination environment. These complexes along with similar lanthanum, erbium, thulium, and lutetium complexes were prepared in situ in a one-step metal promoted condensation reaction between salicylaldehyde and 4-methyl-1,3-phenylenediamine in the presence of lanthanide nitrates. They were isolated and characterized by microanalysis and spectroscopic (IR, ESI–MS, UV–Vis, and ¹H NMR) data with reference to the preformed N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine, which was obtained separately and structurally determined by single crystal X-ray analysis.     

Synthesis and luminescence properties of lanthanide complexes with a new aryl amide bifunctional bridging ligand

A new aryl amide type bifunctional bridging ligand 4,4'-bis{[(2'-benzylaminoformyl)phenoxyl]methyl}-1,1'-biphenyl (L) and its complexes with lanthanide ions (Ln=Pr, Eu, Gd, Tb, Ho, Er) were synthesized and characterized by elemental analysis, infrared spectra, conductivity measurements and thermal analysis. At the same time, the luminescence properties of the Eu and Tb complexes in acetone solutions were investigated. Under the excitation of UV light, these two complexes exhibited characteristic emission of europium and terbium ions. And the lowest triplet state energy level T1 of this ligand matches better to the lowest resonance energy level of Tb(III) than to Eu(III) ion.     

Some lanthanide complexes of N-(2-pyridyl) acetamide

The complexes formed in the reaction between some lanthanide perchlorates and N-(2-pyridyl)acetamide (aapH) have been prepared and characterized. The compounds have the formulae [Ln(aapH)₄] (ClO₄)₃ (where Ln  Pr, Nd, Eu, Gd, Ho, Yb and Lu) and are solid crystalline substances. The new compounds were characterized by means of chemical analyses, molar conductivities, vibrational spectra, thermograviemetry and electronic absorption and emission spectra. The vibrational spectra and molar conductances indicate that the perchlorate groups are ionic and that aapH acts as a bidentate ligand through the carbonyl oxygen and the ring nitrogen. The PMR of La(aapH)₄ (ClO₄)₃ and [Lu(aapH)₄]ClO₄)₃ reveals that the ligands are planar and corroborates the vibrational evidence that they coordinate in a bidentate manner. The oscillator strength (P_exp) of the hypersensitive transition of the Nd(III) complex has been studied and the nephelauxetic effect has been evalauted. The emission of the Eu(III) complex at 77° is very intense and a tentative assignment of its symmetry has been made.     

Metal-metal interactions in dinuclear ruthenium complexes containing bridging 4,5-di(2-pyridyl)imidazolates and related ligands

The dinuclear bis(2,2'-bipyridine)ruthenium complex of 4,5-di(2-pyridyl)imidazolate has been prepared and separated into its (meso and rac) diastereoisomers. The 2-phenyl substituted analogue forms the meso isomer selectively. All three complexes have been characterised by 1H NMR and X-ray crystallography. Electrochemical measurements and spectroelectrochemistry of the mixed-valence states reveal strong metal-metal interactions and IVCT bands that are highly dependent on the electrolyte.     

Preparation, characterization and luminescent properties of lanthanide complexes with a new aryl amide bridging ligand

A new aryl amide type bridging ligand 1,4-bis{[(2'-benzylaminoformyl)phenoxyl]ethoxyl}benzene (L) and its complexes with lanthanide ions (Ln=Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er) were synthesized and characterized by elemental analysis, infrared spectra and electronic spectra. At the same time, the luminescent properties of the Sm, Eu, Tb and Dy complexes in solid state and the Tb complex in solvents were also investigated. At room temperature, these four complexes exhibited characteristic luminescence emissions of the central metal ions under UV light excitation and could be significant in the field of supramolecular photonic devices.     

Sensitized luminescence in dinuclear lanthanide(III) complexes of bridging 8-hydroxyquinoline derivatives with different electronic properties

Three new dinuclear lanthanide(III) complexes {Eu(hfac)(3)(H(2)O)}(2)(μ-HPhMq)(2) (2) and {Ln(hfac)(3)(H(2)O)}(2)(μ-HMe(2)NC(6)H(4)Mq)(2) (Ln = Eu, 3; Nd, 4) with 8-hydroxylquinoline derivatives in μ-phenol mode were synthesized and characterized, where hfac(-) = hexafluoroacetylacetonate, HPhMq = 2-methyl-5-phenylquinolin-8-ol, and HMe(2)C(6)H(4)Mq = 5-(4-(dimethylamino)phenyl)-2-methylquinolin-8-ol. Compared with that (400 nm) for {Eu(hfac)(3)}(2)(μ-HMq)(2) (1, HMq = 2-methy-8-hydroxylquinoline), the excitation wavelength for sensitized lanthanide luminescence is extended to ca. 420 nm for 2, and 500 nm for 4 by introducing a phenyl or 4-(dimethylamino)phenyl to 8-hydroxylquinoline. These dinuclear lanthanide(III) complexes exhibit distinctly fluoride-induced lanthanide(III) emission enhancement in both intensity and lifetime due to replacing coordination water molecules or formation of strong O-H···F hydrogen bonds with coordinated H(2)O and μ-phenol, thus suppressing significantly the non-radiative O-H oscillators.     

Synthesis, crystal structure, spectroscopy and magnetic properties of a dinuclear Cu complex with 3,5-bis(2-pyridyl)pyrazole bridging ligand

A dinuclear Cu^II complex [Cu₂(bpp)₂(H₂O)₂](ClO₄)₂ (1) with 3,5-bis(2-pyridyl)pyrazole (Hbpp), has been synthesized and characterized by elemental analyses, thermal analysis, conductance, UV-vis and IR spectra. The crystal structure of 1, determined by X-ray diffraction technique, reveals that two centrosymmetric Cu^II centers are bridged by a pair of tetradentate anionic bpp ligands, adopting a square-pyramidal environment with the water ligand occupying the axial site. An interesting feature of this structure is the formation of a two-dimensional supramolecular network through O-H?O hydrogen bonds between the water moieties of the cationic [Cu₂(bpp)₂(H₂O)₂]²⁺ subunits and perchlorate anions. The magnetic properties of 1 have been investigated by variable-temperature magnetic susceptibility and EPR measurements. Very strong antiferromagnetic interaction between the Cu^II centers (with H=−JS₁S₂, J=−368.3 cm⁻¹) has been observed, and the magneto-structural correlations was analyzed.     

Design,synthesis and in vitro cytotoxicity of novel dinuclear platinum(II) complexes with a tetradentate carrier ligand

Four novel dinuclear platinum complexes with a tetradentate ligand, (1R,1′R,2R,2′R)‐N¹,N^1′‐(1,2‐phenylenebis(methylene))dicyclohexane‐1,2‐diamine, as the carrier group, have been designed, synthesized and characterized, and their in vitro cytotoxicity against HepG‐2, A549, HCT‐116 and MCF‐7 cell lines evaluated using MTT assay. Results indicate that the targeted dinuclear platinum complexes H1 , H2 , H3 , H4 exhibit significant growth inhibitory properties against HepG‐2, A549 and HCT‐116 cell lines, but none of them show activity against MCF‐7 cell line. Compound H4 shows better antitumor activity than carboplatin against HepG‐2, A549 and HCT‐116 cell lines. Copyright © 2015 John Wiley & Sons, Ltd.     

Tricarbonylrhenium(I) and -technetium(I) complexes with bis(2-pyridyl)phenylphosphine and tris(2-pyridyl)phosphine

(NEt₄)₂[Re(CO)₃Br₃] or (NEt₄)₂[Tc(CO)₃Cl₃] react with bis(2-pyridyl)phenylphosphine (PPhpy₂) or tris(2-pyridyl)phosphine (Ppy₃) under formation of neutral tricarbonyl complexes of the composition [M(CO)₃X(L)] (M = Re, X = Br; M = Tc, X = Cl; L = PPhpy₂ or Ppy₃). In all isolated products, the ligands coordinate solely via two of their nitrogen atoms. All attempts to force a tripodal coordination of the phosphinopyridines failed. Removal of the bromo ligands from (NEt₄)₂[Re(CO)₃Br₃] by the addition of AgNO₃ in THF/water, and subsequent reaction of the resulting [Re(CO)₃(THF)₃](NO₃)with Ppy₃ yielded the complex [Re(CO)₃(NO₃)(Ppy₃-N,N′)] with a monodentate coordinated nitrato ligand. The products have been characterized spectroscopically and by X-ray structure analyses.     

Synthesis and luminescent properties of iridium(III) ionic binuclear complexes with 1,4-bis[2-(2-pyridyl)benzimidazolato]butane as a bridging ligand

New ionic binuclear complexes of iridium(III) containing 1,4-bis[2-(2-pyridyl)benzimidazolato]butane as a bridging ligand were synthesized. These compounds exhibit intensive photo- and electroluminescence of yellow-green, green-yellow, and pink colors. The maximal electroluminescence brightness was 4565 cd/m².     

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.     

Reactions of tris(2-pyridyl)phosphines and tris(2-pyridyl)phosphine oxides with some electrophiles

Treatment of tris(2-pyridyl)phosphine or tris(2-pyridyl)phosphine oxide with electrophiles such as chlorine, bromine, deuterium chloride, or benzenediazonium chloride gave unusual coupling products, i.e., 5-chloro-, 5-bromo-, 5-deuterio-, or 5-phenylazo-2,2′-bipyridyls, respectively, as a major coupling product in each case. This is considered to be the result of electrophilic substitution on a pyridyl ring in a pentacovalent phosphorane intermediate formed in each reaction. © 1997 John Wiley & Sons, Inc. Heteroatom Chem 8: 439–449, 1997     

Metal-metal interactions as a function of bridging ligand topology: an electrochemical,spectroelectrochemical, and magnetic study on dinuclear Oxo-Mo(V) complexes with various isomers of dihydroxynaphthalene as bridging ligand

Reaction of [MoV(TpMe,Me)(O)Cl2] with 1,3-, 1,5-, 1,6-, 2,6-, and 2,7-dihydroxynaphthalene affords the dinuclear complexes [[Mo(TpMe,Me)(O)Cl]2(mu-C10H6O2)], abbreviated as 1,3-Mo2, 1,5-Mo2, 1,6-Mo2, 2,6-Mo2, and 2,7-Mo2, according to the substitution pattern of the bridging ligand. Electrochemical, UV-vis/NIR spectroscopic, and variable-temperature magnetic susceptibility studies have been used to probe the effects of the bridging-ligand topology on the metal-metal electronic and magnetic interactions. The complexes can be split into two classes according to the properties of the bridging ligands. Complexes 1,3-Mo2, 1,6-Mo2, and 2,7-Mo2 all have bridging ligands that are topologically equivalent to meta-substituted bridging ligands such as 1,3-dihydroxybenzene, in that (i) there is an odd number of C atoms separating the two oxygen atoms, regardless of the pathway that is taken through the ligand skeleton, and (ii) the doubly oxidized from of the bridging ligand is a diradical. These complexes are classified as being "T-meta" (= topologically equivalent to meta). Complexes 1,5-Mo2 and 2,6-Mo2 have bridging ligands that are topologically equivalent to para-substituted groups such as 1,4-dihydroxybenzene, in that (i) there is an even number of C atoms separating the two oxygen atoms, whichever pathway is taken through the ligand skeleton, and (ii) the doubly oxidized form of the bridging ligand is a diamagnetic quinone. These complexes are classified as "T-para". Electrochemical studies show that the comproportionation constants for the Mo(V)/Mo(IV) mixed-valence states of the T-meta complexes are smaller than those for the T-para complexes. Spectroelectrochemical studies show that the Mo(V)/Mo(IV) mixed-valence states of the T-para complexes show pronounced Mo(IV)-->Mo(V) IVCT transitions, whereas those of the T-meta complexes do not show these transitions. Magnetic susceptibility studies show that the T-meta complexes all display ferromagnetic exchange between the metal centers, whereas the T-para complexes all display antiferromagnetic exchange. Thus, both the electronic and the magnetic properties of these complexes show a clear demarcation into two sets according to the bridging-ligand topology.     

The elusive tripodal tris(2-pyridyl)borate ligand: a strongly coordinating tetraarylborate

Tris(2-pyridyl)borates are introduced as a new robust and tunable "scorpionate"-type ligand family. A facile synthesis of this hitherto unknown ligand and its complexation to Fe(II) are described; the optical and electrochemical properties of the resulting iron complex are compared to complexes derived from tris(pyrazolyl)borate, tris(2-pyridyl)aluminate, and corresponding charge-neutral ligands.     

The bridging function of an apparently nonbridging ligand: dinuclear rhodium complexes with Rh(mu-SbR3)Rh as a molecular unit

Novel dinuclear rhodium complexes of the general composition [Rh2Cl2(mu-CRR')2(mu-SbiPr3)] (4-6) were prepared by thermolysis of the mononuclear precursors trans-[RhCl(=CRR')(SbiPr3)2] in excellent yield. The X-ray crystal structure analysis of 4 (R = R' = Ph) confirms the symmetrical bridging position of the stibane ligand. Related compounds [Rh2Cl2(mu-CPh2)(mu-CRR')(mu-SbiPr3)] (7, 8) with two different carbene units were obtained either from trans-[RhCl(=CPh2)(SbiPr3)2] (1) and RR'CN2 or by a conproportionation of 4 and 5 (R = R' = p-Tol) or 4 and 6 (R= Ph, R' = p-Tol), respectively. While CO reacts with 4 to give the polymeric product [[RhCl(CPh2)(CO)]n] (9), tert-butyl isocyanide replaces the bridging stibane and yields [Rh2Cl2(mu-CPh2)2(mu-CNtBu)] (10). The reaction of 4 with tertiary phosphanes PR3 leads to complete bridge cleavage and affords the mononuclear compounds trans-[RhCl(=CPh2)(PR3)2] (11-15). In contrast, treatment of 4 with SbMe3 and SbEt3 yields the related triply bridged complexes [Rh2Cl2(mu-CPh2)2(mu-SbR3)] (16, 17) by substitution of SbiPr3 for the smaller stibanes. The displacement of the chloro ligands in 4-6 and 10 by n5-cyclopentadienyl gives the dinuclear complexes [(n5-C5H5)2Rh2(mu-CRR')2] (18-20) and [(n5-C5H5)2Rh2(mu-CPh2)2(mu-CNtBu)] (21), of which 18 (R = R' = Ph) was characterized crystallographically.     

Binuclear nickel(II) complexes with a bridging carbonato ligand

Three nickel(II) dinuclear carbonato-bridged complexes: (-CO3)[Ni(TAA)]2(ClO4)2·4H2O (1), (-CO3)[Ni(TTA)]2- (ClO4)2·2H2O (2), (-CO3)[Ni(cyclam)]2(ClO4)2 (3) [TAA =N(CH2CH2NH2)3,TTA=triethylenetetramine,cyclam = 1,4,8,11-tetraazacyclotetradecane] have been prepared. The temperature dependence of the magnetic susceptibility for (1), (2) and (3) were measured over the 77–300K range and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator (H= –2JS1S2), giving the exchange integral J=–7.75cm–1 for (1), J=–1.23 cm–1 for (2) and J=–40.26cm–1 for (3).     

Tin(iv) and lead(iv) complexes with a tetradentate redox-active ligand

The coordination chemistry of a tetradentate redox-active ligand, glyoxal-bis(2-hydroxy-3,5-di-tert-butylanil) (H(2)L), was investigated with the diorganotin(iv) and diphenyllead(iv) moieties. Complexes R(2)SnL (R = Me (), Et (), (t)Bu (), Ph ()) and Ph(2)PbL () have been prepared and characterized. The molecular structures of compounds , and have been determined by single crystal X-ray diffraction. The diamagnetic octahedral complexes bear a tetradentate O,N,N,O redox-active ligand with a nearly planar core. Complexes demonstrate solvatochromism in solution. The CV of complexes reveals four one-electron redox processes. The spin density distribution in the chemically generated cations and anions of was studied by X-band EPR spectroscopy. The experimental data agree well with the results of DFT calculations of electronic structures for , its pyridine adduct ·Py, cation and anion .