Showing papers on "Denticity published in 2012"

Formate modulated solvothermal synthesis of ZIF-8 investigated using time-resolved in situ X-ray diffraction and scanning electron microscopy

Abstract: Time-resolved investigations using in situ energy-dispersive X-ray diffraction in tandem with ex situscanning electron microscopy revealed that solvothermal crystallisation of ZIF-8 in methanol solvent and in the presence of sodium formate as a simple monodentate ligand (modulator) is a rapid process yielding big, high-quality single crystals in short time (<4 h). Kinetic analysis of crystallisation curves was performed by applying the Avrami–Erofe'ev and Gualtieri models. The analyses revealed that the weakly basic formate modulator acts as a base in deprotonation equilibria (deprotonation of the bridging 2-methylimidazole ligand) rather than as a competitive ligand in coordination equilibria at the metal (Zn2+) centres. This is in contrast to the coordination modulation function of formate in ZIF-8 synthesis at room temperature. Crystal shape evolves with time in the presence of formate from cubes with truncated edges to rhombic dodecahedra. The latter shape represents most likely the stable equilibrium morphology of ZIF-8.

Dual-Emission from a Single-Phase Eu–Ag Metal–Organic Framework: An Alternative Way to Get White-Light Phosphor

Abstract: A new bifunctional NTB (tris(benzimidazol-2-ylmethyl)amine)-type ligand incorporating coordination discriminable tripodal benzimidazolyl and monodentate pyridyl groups, tris((pyridin-3-ylmethyl)benzoimidazol-2-ylmethyl)amine (3-TPyMNTB), has been prepared to assemble 4d–4f heterometallic three-dimensional metal–organic frameworks (MOFs) in a stepwise route: (1) direct reaction of 3-TPyMNTB with Ln(ClO4)3 affords monomeric complexes [Eu(3-TPyMNTB)2](ClO4)3·2.5MeCN (1-Eu) and [Gd(3-TPyMNTB)2](ClO4)3·2MeCN·2CHCl3 (1-Gd), and (2) assembly of the precursors 1-Eu and 1-Gd with AgClO4 gives rise to infinite MOFs [EuAg3(3-TPyMNTB)2(H2O)(MeCN)](ClO4)6·4MeCN (2-Eu-Ag) and [GdAg3(3-TPyMNTB)2(H2O)(MeCN)](ClO4)6·4MeCN (2-Gd-Ag), respectively. In monomer 1-Eu, the ligand shows an antenna effect to transfer absorbed energy to Eu3+ center to emit characteristic red luminescence, while in 4d–4f heterometallic MOF 2-Eu-Ag, the ligand centered emission is resensitized by Ag+ ions to generate dual emissions, coming up with t...

How amidoximate binds the uranyl cation.

Abstract: This study identifies how the amidoximate anion, AO, interacts with the uranyl cation, UO(2)(2+). Density functional theory calculations have been used to evaluate possible binding motifs in a series of [UO(2)(AO)(x)(OH(2))(y)](2-x) (x = 1-3) complexes. These motifs include monodentate binding to either the oxygen or the nitrogen atom of the oxime group, bidentate chelation involving the oxime oxygen atom and the amide nitrogen atom, and η(2) binding with the N-O bond. The theoretical results establish the η(2) motif to be the most stable form. This prediction is confirmed by single-crystal X-ray diffraction of UO(2)(2+) complexes with acetamidoxime and benzamidoxime anions.

Manganese(II) Complexes as Potential Contrast Agents for MRI

Abstract: Mn2+ has five unpaired d electrons, a long electronic relaxation time, and labile water exchange, which make it an attractive alternative to Gd3+ in the design of contrast agents for medical Magnetic Resonance Imaging. In order to ensure in vivo safety and high contrast agent efficiency, the Mn2+ ion has to be chelated by a ligand that provides high thermodynamic stability and kinetic inertness of the complex and has to have at least one free coordination site for a water molecule. Unfortunately, these two requirements are contradictory, as lower denticity of the ligands, which leads to more inner-sphere water molecules often implies a decreased stability of the complex, and, therefore, it is necessary to find a balance between both requirements. In the last decade, a large amount of experimental data has been collected to characterize the physico-chemical properties of Mn2+ chelates with variable ligand structures. They now allow for establishing trends of how the ligand structure, the rigidity of the ligand scaffold, and its donor–acceptor properties influence the thermodynamic, kinetic, and redox stability of the Mn2+ complex. This microreview surveys the current literature in this field.

Further observations on water oxidation catalyzed by mononuclear Ru(II) complexes.

Abstract: A family of 28 mononuclear Ru(II) complexes have been prepared and characterized by 1H NMR, electronic absorption, and cyclic voltammetry. These complexes are studied as catalysts for water oxidation. All the catalysts possess one tridentate ligand, closely related to 2,2′;6,2″-terpyridine (tpy) and may be divided into two basic types. In the type-1 catalyst, the three remaining coordination sites are occupied by a bidentate closely related to 2,2′-bipyridine (bpy) and a monodentate halogen (Br, Cl, or I) or water molecule. In the type-2 catalyst, the three remaining coordination sites are occupied by two axial 4-picoline molecules and an equatorial halogen or water. In general the type-2 catalysts are more reactive than the type-1. The type-2 iodo-catalyst shows first-order behavior and, unlike the bromo- and chloro-catalysts, does not require water–halogen exchange to show good activity. The importance of steric strain and hindrance around the metal center is examined. The introduction of three t-butyl ...

Sensing of Aqueous Fluoride Anions by Cationic Stibine–Palladium Complexes

Abstract: Turn on the lantern! The stibine donor ligand of a cationic palladium complex acts as a Lewis acid and reacts with a fluoride anion to afford the corresponding fluorostiboranyl-palladium species (see scheme). Bindung of the fluoride anion to the antimony center induces a change in denticity of the triphosphine unit and leads to a bright-orange trigonal-bipyramidal d(8) lantern complex.

“Click-Triazole” Coordination Chemistry: Exploiting 1,4-Disubstituted-1,2,3-Triazoles as Ligands

Abstract: Access to readily functionalized ligand architectures is of crucial importance in a range of different areas including catalysis, metallopharmaceuticals, bioimaging, metallosupramolecular chemistry, mechanically interlocked architectures, and molecular machines. The mild and modular Cu(I)-catalyzed 1,3-cycloaddition of terminal alkynes with organic azides (the CuAAC “click” reaction) allows the ready formation of functionalized 1,4-disubstituted-1,2,3-triazole scaffolds, and this has led to an explosion of interest in the coordination chemistry of these heterocycles. The parent 1,4-disubstituted-1,2,3-triazole units can potentially act as monodentate or bridging ligands. Examples of both the monodentate (through either the N3 nitrogen or C5 carbon positions of the 1,2,3-triazole) and bridging (through the N2 and N3 nitrogen atoms) coordination modes have been structurally characterized. A diverse array of bi-, tri-, and polydentate ligands incorporating 1,4-disubstituted-1,2,3-triazole units have also been synthesized and characterized. When the chelate pocket involves coordination through the N3 nitrogen atom of the 1,2,3-triazole, these are called “regular” click ligands. While these are the most common type of “click” chelate, “inverse” ligands in which the 1,2,3-triazole unit coordinates through the less electron-rich N2 nitrogen atom have also been synthesized and characterized. The resulting “click” complexes are beginning to find applications in catalysis, metallosupramolecular chemistry, photophysics, and as metallopharmaceuticals and bioimaging agents.

Highly enhanced affinity of multidentate versus bidentate zwitterionic ligands for long-term quantum dot bioimaging.

Abstract: High colloidal stability in aqueous conditions is a prerequisite for fluorescent nanocrystals, otherwise known as “quantum dots”, intended to be used in any long-term bioimaging experiment. This essential property implies a strong affinity between the nanoparticles themselves and the ligands they are coated with. To further improve the properties of the bidentate monozwitterionic ligand previously developed in our team, we synthesized a multidentate polyzwitterionic ligand, issued from the copolymerization of a bidentate monomer and a monozwitterionic one. The nanocrystals passivated by this polymeric ligand showed an exceptional colloidal stability, regardless of the medium conditions (pH, salinity, dilution, and biological environment), and we demonstrated the affinity of the polymer exceeded by 3 orders of magnitude that of the bidentate ligand (desorption rates assessed by a competition experiment). The synthesis of the multidentate polyzwitterionic ligand proved also to be easily tunable and allowed ...

Synthesis, crystal structure, and luminescent properties of 2-(2,2,2-trifluoroethyl)-1-indone lanthanide complexes.

Abstract: A new β-diketone, 2-(2,2,2-trifluoroethyl)-1-indone (TFI), which contains a trifluorinated alkyl group and a rigid indone group, has been designed and employed for the synthesis of two series of new TFI lanthanide complexes with a general formula [Ln(TFI)3L] [Ln = Eu, L = (H2O)2 (1), bpy (2), and phen (3); Ln = Sm, L = (H2O)2 (4), bpy (5), and phen (6); bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline]. X-ray crystallographic analysis reveals that complexes 1–6 are mononuclear, with the central Ln3+ ion eight-coordinated by six oxygen atoms furnished by three TFI ligands and two O/N atoms from ancillary ligand(s). The room-temperature photoluminescence (PL) spectra of complexes 1–6 show strong characteristic emissions of the corresponding Eu3+ and Sm3+ ions, and the substitution of the solvent molecules by bidentate nitrogen ligands essentially enhances the luminescence quantum yields and lifetimes of the complexes.

Bis[N,N'-diisopropylbenzamidinato(-)]silicon(II): a silicon(II) compound with both a bidentate and a monodentate amidinato ligand.

Abstract: Well looked-after: reductive HCl elimination of the λ(6)-silicon(IV) complex 1 leads to the λ(3)-silicon(II) species 2, a novel type of donor-stabilized silylene. Reaction of 2 with [W(CO)(6)] and with I(2) yields the λ(5)-silicon(II) complex 3 and the λ(6)-silicon(IV) complex 4, respectively.

Molybdenum(VI) dioxo complexes employing Schiff base ligands with an intramolecular donor for highly selective olefin epoxidation.

Abstract: Reaction of [MoO(2)(η(2)-tBu(2)pz)(2)] with Schiff base ligands HL(X) (X = 1-5) gave molybdenum(VI) dioxo complexes of the type cis-[MoO(2)(L(X))(2)] as yellow to light brown solids in moderate to good yields. All ligands coordinate via its phenolic O atom and the imine N atom in a bidentate manner to the metal center. The third donor atom (R(2) = OMe or NMe(2)) in the side chain in complexes 1-4 is not involved in coordination and remains pendant. This was confirmed by X-ray diffraction analyses of complexes 1 and 3. Complexes 1, 3, and 5 exist as a mixture of two isomers in solution, whereas complexes 2 and 4 with sterically less demanding substituents on the aromatics only show one isomer in solution. All complexes are active catalysts in the epoxidation of various internal and terminal alkenes, and epoxides in moderate to good yields with high selectivities are obtained. In the challenging epoxidation of styrene, complexes 1 and 2 prove to be very active and selective. The selectivity seems to be influenced by the pendant donor arm, as complex 5 without additional donor in the side chain is less selective. Experiments prove that the addition of n-butyl methyl ether as intermolecular donor per se has no influence on the selectivity. The basic conditions induced by the NMe(2) groups in complexes 3 and 4 lead to lower activity.

Ligand Controlled Highly Selective Copper-Catalyzed Borylcuprations of Allenes with Bis(pinacolato)diboron

Abstract: Copper-catalyzed highly selective borylcuprations of allenes with bis(pinacolato)diboron produce two different types of alkenylboranes by applying a ligand effect. In the presence of tris(para-methoxyphenyl)phosphine [P(C6H4OMe-p)3], the reaction of aryl-1,2-dienes affords 2-alken-2-yl boronates as the only product with exclusive Z-geometry; the regioselectivity is switched to afford the 1-alken-2-yl boronates as the major products when the bidentate phosphine 2,2′-bis(diphenylphosphino)biphenyl is used as the ligand.

The art of filling protein pockets efficiently with octahedral metal complexes.

Abstract: Complicated natural products, with their structures and properties evolved over millions of years, frequently display specific biological modes of action which can often be traced back to their highly preorganized three dimensional structures that perfectly complement the shape and functional group presentation of their target protein pockets.[1] A recent study analyzed the protein binding properties of compounds from natural as well as synthetic sources and found that protein binding selectivity correlated with shape complexity (defined as the relative content of sp3-hybridized carbons) and stereochemical complexity (defined as the relative content of stereogenic carbons).[2] Octahedral metal complexes may offer an attractive alternative strategy to sophisticated globular and rigid structural templates. They are constructed from a powerful single metal stereocenter with chelating ligands limiting the degree of conformational flexibility, thus achieving “natural-product-like” structural complexities and strinkingly high target specificities as demonstrated by us in several previous studies.[3–6] An important aspect regarding the design of such metal-templated protein binders –which has not been articulated in the past– is the globular space requirement of an octahedral center. The latter significantly increases the demand for a proper design, mainly because the metal must be located at a specific position within the active site in order to be useful. For example, if the metal is located too far within the active site or too close to the protein backbone there will not be enough space available to accommodate the space-demanding octahedral coordination sphere, whereas if the metal is located too far towards the solvent, the metal center cannot easily impact on binding affinity and selectivity. A clear indicator for an advantageous metal position within the protein pocket is a strong influence of the metal coordination sphere on binding affinity and selectivity. We have identified such a priviledged position of the metal within the ATP-binding site of protein kinases by using the now well established staurosporine-inspired metallo-pyridocarbazole scaffold.[3–7] For example, the octahedral organoruthenium complex Λ-FL172 was designed as a selective inhibitor for the p21-activated kinase 1 (PAK1)[8] in which the bidentate pyridocarbazole ligand of the ruthenium complex occupies the adenine pocket.[4] By interacting with the so-called hinge region it places the ruthenium center at a defined position within the ribose binding site, where the additional CO, chloride, and bidentate iminopyridine ligands can form important contacts with other parts of the active site and thereby strongly contribute to binding affinity and selectivity (Figure 1).[4,6] In order to better understand the design of metal-based enzyme inhibitors, we wondered if this design is unique or whether other scaffolds with metals located at other positions within the active site could yield similar or even better results. To address this question, we designed new scaffolds[9] and uncovered a simple ruthenium complex (R)-1 which places the metal at a distinct position within the ATP-binding site, contains a completely different set of coordinating ligands, but at the same time shows an improved affinity for PAK1 compared to the much more complicated, previously established pyridocarbazole complex Λ-FL172. Figure 1 Complicated versus simple design for metal-templated inhibitors of the protein kinase PAK1. Ruthenium complex 1 is based on a simple pyridylphthalimide scaffold, which can be synthesized in just a few steps (Scheme 1). Accordingly, a Suzuki cross-coupling of bromophthalimide 2 with 2-trimethylstannylpyridine afforded the pyridylphthalimide 3 (49%), which was subsequently reacted with the ruthenium complex [Ru(C6H12S3)(MeCN)3](CF3SO3)2 under basic conditions, followed by the addition of NaSCN to afford the racemic complex 1 (38% over two steps). A crystal structure of the N-benzylated derivative of 1 is shown in Figure 2 and demonstrates the formation of a C-Ru bond. This cyclometallation reduces the requirement for metal-coordinating heteroatoms and is thus crucial for the short and efficient synthesis. Figure 2 Structure of the N-benzylated derivative of complex 1 (1Bn). Disordered solvent and a disordered position of S101 are not shown. ORTEP drawing with 50% probability thermal ellipsoids. Selected bond distances (A): C15-Ru1 = 2.033(4), N1-Ru1 = 2.098(3), ... Scheme 1 Synthesis of pyridylphthalimide ruthenium complex 1. The racemic complex 1 displays an IC50 value of 83 ± 20 nM (1 µM ATP) against PAK1, which is slightly more potent than the previously reported Λ-FL172 (IC50 = 130 nM, 1 µM ATP)[4] (Figure 3). Interestingly, the pyridylphthalimide ligand itself is not an inhibitor for PAK1 at all (IC50 > 100 µM), thus demonstrating the importance of the entire coordination sphere for protein kinase binding. Figure 3 IC50 curves with PAK1 of ligand 4, complex 1, and some derivative complexes 5–7. ATP concentration was 1 µM. PAK1 harbors a very atypical, open ATP-binding site which is probably responsible for the difficulties to develop high affinity inhibitors of this kinase.[4,8,10] A cocrystal structure at the resolution of 2.0 A reveals the binding of the (R)-enantiomer of 1 to the ATP binding site of PAK1 (amino acids 249–545 with mutation Lys299Arg)[11] (Figures 4 and ​and5).5). The van der Waals surface representation shown in Figure 4 demonstrates how nicely the ATP-binding site is filled with (R)-1 in a shape complementary fashion with the phthalimide moiety additionally forming two hydrogen bonds with the hinge region (Glu345 and Leu347) and one water-mediated contact to Thr406 (Figure 5). Interestingly, superimposition of this structure with the recently disclosed PAK1/Λ-FL172[4] cocrystal structure demonstrates that even though both compounds are ATP-competitive binders, they significantly differ in there binding modes (Figure 6). While both form the canonical hydrogen bonds between the maleimide moieties of the inhibitor and the hinge region of the kinase, the aromatic heterocycles are rotated towards each other by approximately 30° demonstrating the range that is possible for the directionality of hydrogen bonds. Furthermore, the metals of the two inhibitor scaffolds are 3.0 A apart from each other and point the monodentate ligands into different areas of the active site. Whereas the CO of FL172 is located right below the center of the glycine-rich loop (P-loop), the NCS ligand of 1 points towards the interface of the glycine-rich loop (connecting strands β1 and β2) and the methylene groups of Arg299 of the β-sheet strand β3 and thereby perfectly filling a small hydrophobic pocket as visualized in the van der Waals representation of Figure 4. The importance of the NCS ligand is manifested by the loss of the binding affinity of related complexes, which carry instead a SeCN (IC50 = 0.625 ± 0.06 µM, 7.5-fold weaker inhibitor), NCO (IC50 = 15.7 ± 2 µM, 193-fold weaker inhibitor), or CO (IC50 = 12.7 ± 2 µM, 153-fold weaker inhibitor) ligand (Figure 3). This intriguing example demonstrates how a different position of the metal within the active site, even if it is just shifted by 3.0 A, requires a completely different coordination sphere to fill the protein pocket in a comparable fashion. Figure 4 Cocrystal structure of PAK1 (amino acids 249–545 with mutation Lys299Arg) and (R)-1 at 2.0 A with displayed van der Waals surfaces. Coordinates of the structure have been deposited in the Protein Data Bank (PDB ID: 4DAW). Figure 5 Hydrogen bonding of (R)-1 within the ATP-binding site of PAK1. Figure 6 Relative binding position of (R)-1 and Λ-FL172 (PDB ID: 3FXZ) within the ATP-binding site of PAK1. Superimposed with the PyMOL Molecular Graphics System, Version 1.3, Schrodinger, LLC. In conclusion, the here presented metal-based enzyme inhibitor design together with the analysis of an X-ray cocrystal structure reveals the scope of fitting octahedral metal complexes within an enzyme active site. Despite the shortness of the synthesis (overall only 6 steps) and simplicity of the structure (only two stereoisomers possible), complex 1 displays an IC50 value of 83 nM (1 µM ATP) which is superior to FL172, a complex that is much more tedious to synthesize (>15 steps) and contains a much higher stereochemical complexity (20 possible stereoisomers). To date, the ruthenium phthalimide complex 1 described here belongs to the most potent ATP-competitive inhibitors known for the protein kinase PAK1,[12] demonstrating the advantages of filling large or open pockets with globular octahedral metal complexes.

Zinc complexes supported by claw-type aminophenolate ligands: synthesis, characterization and catalysis in the ring-opening polymerization of rac-lactide.

Abstract: A series of zinc silylamido complexes bearing claw-type multidentate aminophenolate ligands, [LZnN(SiMe3)2] (L = –OAr1-CH2N[(CH2)nNR2]CH2Ar2, n = 2 or 3; R = Me or Et (1a–3a, 5a, 7a and 8a); L = –OC6H2-4,6-tBu2-2-CH2N[(CH2)2OMe]2 (9a)), have been synthesized via the reaction of Zn[N(SiMe3)2]2 and 1 equiv. of corresponding aminophenol. The reaction of Zn[N(SiMe3)2]2 with the proligand L6H (2-{N-(2-methoxybenzyl)-N-[3-(N′,N′-dimethylamino)propyl]aminomethyl}-4-methyl-6-tritylphenol) resulted in the formation of bisphenolate zinc complex 6 regardless of the stoichiometric ratio of the two starting materials. Complex 4b with an initiating group of 3-tert-butyl-2-methoxy-5- methylbenzyloxy was obtained and further studied via the X-ray diffraction method to be monomeric. Zinc ethyl complex 2c was also prepared from the reaction of ZnEt2 and 1 equiv. of proligand L2H as the representative complex with an alkyl initiating group. All zinc silylamido complexes efficiently initiated the ring-opening polymerization of rac-lactide in the presence or absence of isopropanol at ambient temperature. The steric and electronic characteristics of the ancillary ligands significantly influenced the polymerization performance of the corresponding zinc complexes. The introduction of bulky ortho- substituents on the phenoxy moiety resulted in an apparent decrease of catalytic activity while a slightly enhanced isotactic selectivity. Meanwhile, the elongation of the pendant amine arm to three-carbon-atom linkage led to significant decline of the catalytic activity in the absence of isopropanol. The zinc ethyl complex 2c was not such an efficient initiator as the silylamido ones, but the alkoxy complex 4b gave an obviously faster and better controlled polymerization when compared to the zinc silylamido complexes.

Synthesis and Characterization of a Novel Schiff Base Metal Complexes and their Application in Determination of Iron in Different Types of Natural Water

Abstract: A novel, simple approach to the synthesis of macrocyclic Schiff base ligand resulted from the condensation of bisaldehyde and ethylenediamine was prepared (7, 8, 15, 16, 17, 18-hexahydrodibenzo (a, g) (14) annulene) (L) and its complexes were synthesized and characterized using different physicochemical studies as elemental analysis, FT-IR, 1H NMR, conductivity, magnetic properties, thermal analysis, and their biological activities. The spectroscopic data of the complexes suggest their 1:1 complexe structures which are investigated by elemental analysis, FT-IR, 1H NMR, conductivity, magnetic properties, thermal analysis, and their biological activities. The spectroscopic studies suggested the octahedral structure for the all complexes. The spectroscopic data of the complexes suggest their structure in which (N2O2) group act as a tetradentate ligand and two chlorides as monodentate ligands. Also electronic spectra and magnetic susceptibility measurements indicate octahedral structure of these complexes. The synthesized Schiff base and its metal complexes also were screened for their antibacterial and antifungal activity. Here we report the effect of a neutral chelating ligand on the complexation with iron to determine it in different types of natural water using recovery test. The activity data show that the metal complexes to be more potent/ antibacterial than the parent Schiff base ligand against one or more bacterial species.

Structurally diverse copper(II) complexes of polyaza ligands containing 1,2,3-triazoles: site selectivity and magnetic properties.

Abstract: Copper(II) acetate mediated coupling reactions between 2,6-bis(azidomethyl)pyridine or 2-picolylazide and two terminal alkynes afford 1,2,3-triazolyl-containing ligands L1–L6. These ligands contain various nitrogen-based Lewis basic sites including two different pyridyls, two nitrogen atoms on a 1,2,3-triazolyl ring, and the azido group. A rich structural diversity, which includes mononuclear and dinuclear complexes as well as one-dimensional polymers, was observed in the copper(II) complexes of L1–L6. The preference of copper(II) to two common bidentate 1,2,3-triazolyl-containing coordination sites was investigated using isothermal titration calorimetry and, using zinc(II) as a surrogate, in 1H NMR titration experiments. The magnetic interactions between the copper(II) centers in three dinuclear complexes were analyzed via temperature-dependent magnetic susceptibility measurements and high-frequency electron paramagnetic resonance spectroscopy. The observed magnetic superexchange is strongly dependent on...

Self-assembly of the Oxy-tyrosinase Core and the Fundamental Components of Phenolic Hydroxylation

Abstract: A functional active-site mimic of the oxy-tyrosinase enzyme forms through self-assembly of monodentate imidazole ligands, copper(I) and oxygen at −125 °C. The fidelity of this copper–dioxygen complex to the native enzyme, its inherent stability and hydroxylation reactivity suggest that an organizational role of the protein matrix suffices to realize function.

Synthesis of iridium and ruthenium complexes with (N,N), (N,O) and (O,O) coordinating bidentate ligands as potential anti-cancer agents.

Abstract: Several Ru-arene and Ir–Cp* complexes have been prepared incorporating (N,N), (N,O) and (O,O) coordinating bidentate ligands and have been found to be active against both HT-29 and MCF-7 cell lines. By incorporating a biologically active ligand into a metal complex the anti-cancer activity is increased.

Novel N^C^N-cyclometallated platinum complexes with acetylide co-ligands as efficient phosphors for OLEDs

Abstract: Two new cyclometallated platinum(II) complexes have been prepared that incorporate a terdentate N^C^N-coordinating ligand and a monodentate acetylide co-ligand. The complexes, namely [PtL3–CC–C6H3F2] and [PtL6–CC–C6H3F2] (where HL3 = 5-methyl-1,3-di(2-pyridyl)benzene; HL6 = 5-mesityl-1,3-di(2-pyridyl)benzene; H–CC–C6H3F2 = 3,5-difluorophenylacetylene), were prepared by ligand metathesis from the corresponding chloro complex PtLnCl. Both of the new complexes are intensely luminescent in solution, displaying quantum yields superior to PtLnCl. OLEDs have been prepared using the new compounds as phosphorescent emitters. Although both lead to efficient devices, the best electroluminescence quantum efficiencies are obtained with the derivative of HL6, having the mesityl group on the cyclometallated phenyl ring. The superior performance with this complex can be rationalised in terms of the greater steric hindrance that serves to reduce aggregate-induced quenching.

Syntheses, DNA binding and anticancer profiles of L-glutamic acid ligand and its copper(II) and ruthenium(III) complexes.

Abstract: A new multidentate ligand (L) has been synthesized by the controlled condensation of L-glutamic acid with formaldehyde and ethylenediamine. Cu(II) and Ru(III) metal ion complexes of the synthesized ligand have also been prepared. The ligand and the metal complexes were purified by chromatography and characterized by spectroscopy and other techniques. Molar conductance measurements suggested ionic nature of the complexes. The ligand and the complexes are soluble in water with quite good stabilities; essential requirements for effective anticancer drugs. DNA binding constants (Kbs) for copper and ruthenium complexes were 1.8 x 103 and 2.6 x 103 M-1 while their Ksv values were 7.9 x 103, and 7.3 x 103; revealing strong binding of these complexes with DNA. Hemolytic assays of the reported compounds indicated their significantly less toxicity to RBCs than the standard anticancer drug letrazole. Anticancer profiles of all the compounds were determined on HepG2, HT-29, MDA-MB-231 and HeLa human cancer cell lines. All the compounds have quite good activities on HeLa cell lines but the best results were of CuL on HepG2, HT-29 and MDA-MB-231 cell lines.