Palladium(II) and platinum(II) complexes of bidentate 2-pyridyl-1,2,3-triazole “click” ligands: Synthesis,properties and X-ray structures

The synthesis and characterization of palladium(II) and platinum(II) complexes of isomeric bidentate 2-pyridyl-1,2,3-triazole “click” ligands is reported. The complexes have been fully characterized by elemental analysis, HRESI-MS, IR, UV–Vis, ¹H and ¹³C NMR spectroscopy. Additionally, the molecular structures of the Pd(II) and Pt(II) complexes of the 2-[(4-phenyl-1H-1,2,3-triazol-1-yl)methyl]pyridine ligand are confirmed by X-ray crystallography. Solution studies indicate the 2-(1-benzyl-1H-1,2,3-triazol-4-yl)pyridine ligand forms more stable complexes with Pd(II) and Pt(II) than the isomeric 2-[(4-phenyl-1H-1,2,3-triazol-1-yl)methyl]pyridine ligand.     

Synthesis and properties of ms- and β-substituted Pt(II) and Pt(IV) tetraphenylporphyrinates

The interaction of 5,10,15,20-tetraphenylporphyrin, 5,10,15,20-tetra-(4-chlorophenyl)porphyrin, 2-bromo-5,10,15,20-tetraphenylporphyrin, and 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin with platinum(II) chloride in boiling phenol has been studied. The corresponding platinum(II) porphyrinates have been synthesized; their subsequent treatment with bromine in chloroform resulted in platinum(IV) porphyrinates. The Pt(II) and Pt(IV)(Br)₂ porphyrinates have been identified by elemental analysis, electron absorption, IR, and ¹H NMR spectroscopy.     

Coordination chemistry of palladium(II) and platinum(II) complexes with bioactive Schiff bases: Synthetic,spectral, and biocidal aspects

The Schiff bases, 5-nitro-indol-2,3-dionehydrazinecarboxamide (HSCZ¹) and 7-nitro-indol-2,3- dionehydrazinecarboxamide (HSCZ²), have been synthesized by the condensation of 5-nitro-indol-2,3-dione and 7-nitro-1H-indol-2,3-dione with semicarbazide hydrochloride, respectively. The palladium(II) and platinum( II) complexes have been prepared by mixing palladium chloride and platinum chloride in 1: 2 molar ratios with monobasic bidentate Schiff bases. The ligands and complexes of palladium and platinum have been characterized by elemental analyses, melting point determinations, conductance measurements, molecular weight determinations, and IR, ¹H NMR, and UV spectral studies. These studies showed that the ligands coordinate to the metal atoms in a monobasic bidentate mode, coordinating through oxygen and nitrogen donor systems. Thus, a tetracoordinated environment around the metal atom has been proposed. Both the ligands and their complexes have been screened for their biological activity on several pathogenic fungi and bacteria and were found to possess appreciable fungicidal and bactericidal properties. Plant growth regulating activity of one of the ligands and its complexes has also been recorded on gram plant, and results have been discussed. The article is published in the original.     

A 13C and 1H NMR investigation of the bonding in norbornenyl complexes of palladium(II) and platinum(II)

The modes of bonding in several norbornenyl complexes of palladinm(II) and platinum(II) has been investigated by both ¹H and ¹³C NMR spectroscopy. Analysis of internal ¹H¹H, ¹³C¹H, and ¹⁹⁵Pt¹³C coupling constants indicate considerable distortion of the norbornenyl ligand in these complexes relative to organic norbornenes. The nature of this distortion is compatible with a π-homoallylic bonding scheme.     

Reactions of platinum nitrile complexes with cyclotriphosphazenes containing pyridylalkylamino groups

Reactions of platinum(II) and platinum(IV) nitrile complexes with polydentate ligands, such as pentaphenoxy(2-pyridylmethylamino)cyclotriphosphazene, pentaphenoxy(3-pyridylmethylamino)cyclotriphosphazene, and pentaphenoxy(2-pyridylethylamino)cyclotriphosphazene, were studied. Platinum(IV) is reduced to platinum(II) upon complex formation; the pyridine and alkylamine nitrogen atoms coordinate to platinum(II) to form chelate rings. The compounds obtained were characterized by ¹H and ³¹P NMR and IR spectroscopy, FAB mass spectrometry, and other methods.     

Geometric Photoisomerization of Chiral Platinum(II) Sulfoxide Compounds

Photochemical behavior of platinum(II) sulfoxide-containing complexes in methyl chloride was studied by polarimetry and ¹H NMR spectroscopy.     

Platinum (II) N‐heterocyclic carbene complexes: Synthesis,characterization and cytotoxic properties

Platinum (II) complexes bearing N‐heterocyclic carbene (NHC) ligands have been widely used in catalytic chemistry, but there are very few reports of biological properties of this type of complexes. A series of [PtCl₂(NHC)(PEt₃)] complexes were synthesized. The structures of all compounds were characterized by ¹H‐NMR, ¹³C‐NMR, IR and elemental analysis techniques, which supported the proposed structures. The single crystal structures of complexes 1a and 1e were determined. The title complexes show slightly distorted square‐planar coordination around the platinum (II) metal center. The cytotoxic properties of the platinum (II)–NHC complexes have been assessed in various human cancer lines, including cisplatin‐sensitive and resistant cells. IC₅₀ values of these four complexes were determined by the MTS‐based assay on three human cell lines—brain (SHSY5Y), colon (HTC116) and liver (HEP3B). These complexes have been highlighted cancer therapeutic agent with unique structures and functions.     

Gold(III) and platinum(II) complexes of hexamethylenetetramine

Gold(III) trichloride and platinum(II) dichloride form 1:1 complexes with hexamethylenetetramine. The compounds prepared were characterized by the elemental analysis, infrared,Raman,¹H-NMR, and¹³C-NMR spectroscopy, and conductivity measurements.     

Reactions of platinum(II) complexes with sulfur- and histidine-containing peptides: a model for selective platination of peptides and proteins

The reactions between two monofunctional platinum complexes [Pt(Me₄dien)Cl]⁺ (Me₄dien = 1,1,7,7-tetramethyl-diethylenetriamine) and [Pt(Et₄dien)Cl]⁺ (Et₄dien = 1,1,7,7-tetraethyldiethylenetriamine) and the peptides, N-acetylated L-methionyl-L-histidine (MeCO–Met–His) and glutathione (GSH), have been investigated by ¹H-n.m.r. spectroscopy and u.v.–vis. spectrophotometry. The reactions of the platinum(II) complexes with MeCO–Met–His were carried out at room temperature and at pH 3.0 and 7.0, whereas with GSH the reactions were studied only at pH 3.0. No binding of these two platinum complexes to the sulfur atom of methionine or to nitrogen atoms of histidine residue of MeCO–Met–His was observed during the first 24 h. When the reaction was followed further, after 24 h very slow binding of [Pt(Me₄dien)Cl]⁺ to the N3 nitrogen atom of imidazole was observed. Both platinum complexes react with the sulfur atom of the cysteine residue in GSH. Kinetic data show that GSH reacts twice as fast with [Pt(Me₄dien)Cl]⁺ than with [Pt(Et₄dien)Cl]⁺. Our findings indicate that sterically crowded platinum(II) complexes are only capable of reacting with the sulfhydryl group of the cysteine residue. This influences the design of new platinum(II) complexes for selective covalent modification of peptides and proteins.     

Addition of Tetrachloromethane to Alkenes,Catalyzed by Pt(II) Complexes

Platinum(II) complexes [dichlorobis(triphenylphosphine)platinum(II), dichlorobis(tri-m-tolylphosphine)platinum(II), dichloro(2,9-dimethyl-1,10-N, N′-phenanthroline)platinum(II), etc.] showed catalytic activity in addition of tetrachloromethane across the double bond in 1-hexene, 1-heptene, 1-octene, 1-decene, and cyclohexene. The stability of the platinum catalysts was evaluated by GLC, gas chromatography-mass spectrometry, and ³¹P NMR and IR spectroscopy; the kinetic relationships of the addition reactions were determined. A reaction mechanism involving formation of trichloromethyl radical was suggested. A correlation was revealed for the first time between the catalytic activity of platinum, palladium, and rhodium complexes and the capability of these complexes to generate hexachloroethane.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 5, 2005, pp. 778–782.Original Russian Text Copyright © 2005 by Zazybin, Khusnutdinova, Osipova, Solomonov.     

Red electrophosphorescent platinum(II) quinolinolate complexes

Abstract  

Luminescent organoplatinum complexes featuring 8-quinolinolates as chelating ligands have been synthesized and characterized. Substitution of the quinolinolate ligand has been achieved in the 5 position, where benzoyl substituents were introduced by reacting 8-hydroxyquinoline and the corresponding benzoyl chloride in a Friedel–Crafts acylation. The resulting complexes, κ²(N,C²)-(2-(4-tert-butylphenyl)pyridine)-κ²(N,O)-(5-(4-tert-butylphenyl)(8-quinolinolato-5-yl)methanone)platinum(II) and κ²(N,C²)-(3-hexyloxy-2-phenylpyridine)-κ²(N,O)-((8-quinolinolato-5-yl)phenylmethanone)platinum(II), have been investigated by nuclear magnetic resonance and infrared spectroscopy, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, X-ray analysis, thermal analysis, cyclic voltammetry, UV–vis absorption spectroscopy, and luminescence measurements in solution and in the solid state. The solid-state structures of the complexes were found to be dominated by π–π intermolecular interactions. Organic light-emitting devices based on the complexes and a matching host material gave red to near-infrared electroluminescence with low-onset voltages (4–5 V) and continuous wave luminance intensities exceeding 500 cd/m².     

The preparation and electrochemistry of manganese(II) complexes of an unsaturated pentadentate macrocyclic ligand

The preparation of a series of six and seven coordinate manganese(II) complexes [Mn^(II)(L)X]⁺, and [Mn^(II)(L)X₂]^2? (X = halide, water, triphenylphosphine oxide, imidazole, 1-methyl imidazole and pyridine) incorporating the pentadentate planar macrocylic ligand L is described. Cyclic voltammetry of these complexes in acetonitrile each shows a reversible one-electron reduction wave near - 1.4 V vs a Ag/AgNO₃ reference electrode. Quantitative reduction of these complexes by controlled potential electrolysis at a platinum gauze at - 1.4 V yields the corresponding one-electron reduction products which have been shown by ESR spectroscopy to be manganese(II)-ligand radical species, the electron being thought to reside on the di-imino pyridine moiety of the macrocyclic ligand. No metal reduced species could be isolated even in the presence of π-acceptor ligands such as CO or phosphines.     

Assembly of Palladium(II) and Platinum(II) Metallo‐Rectangles with a Guanosine‐Substituted Terpyridine and Study of Their Interactions with Quadruplex DNA

Two novel [2+2] metallo‐assemblies based on a guanosine‐substituted terpyridine ligand ( 1 ) coordinated to palladium(II) ( 2 a ) and platinum(II) ( 2 b ) are reported. These supramolecular assemblies have been fully characterized by NMR spectroscopy, ESI mass spectrometry and elemental analyses. The palladium(II) complex ( 2 a ) has also been characterized by single crystal X‐ray diffraction studies confirming that the system is a [2+2] metallo‐rectangle in the solid state. The stabilities of these [2+2] assemblies in solution have been confirmed by DOSY studies as well as by variable temperature ¹H NMR spectroscopy. The ability of these dinuclear complexes to interact with quadruplex and duplex DNA was investigated by fluorescent intercalator displacement (FID) assays, fluorescence resonance energy transfer (FRET) melting studies, and electrospray mass spectrometry (ESI‐MS). These studies have shown that both these assemblies interact selectively with quadruplex DNA (human telomeric DNA and the G‐rich promoter region of c‐myc oncogene) over duplex DNA, and are able to induce dimerization of parallel G‐quadruplex structures.     

Spectral and biocidal studies of palladium(II) and platinum(II) complexes with monobasic bidentate Schiff bases

The monobasic bidentate Schiff base complexes of palladium(II) and platinum(II) derived from 1H-indol-2,3-dione thiosemicarbazone (L¹H) and 1H-indol-2,3-dione semicarbazone (L²H) have been characterized on the basis of elemental analysis, molecular weight determinations, i.r., ¹H n.m.r. and u.v. spectral studies. Based on these studies a square planar environment around the metal atoms has been proposed. Antimicrobial effects of both the ligands and their complexes on different species of pathogenic fungi and bacteria have been recorded and these are found to possess significant fungicidal and bactericidal properties.     

Luminescent cyclometallated platinum(II) complexes with N-benzoyl thiourea derivatives as ancillary ligands

A series of cyclometallated 2-phenylpyridine Pt(II) complexes having N-benzoyl thiourea derivatives as ancillary ligands were prepared and characterised by elemental analysis, IR and UV–Vis spectroscopy, ¹H and ¹³C NMR spectroscopy as well as by X-ray diffraction on single-crystal. All complexes were obtained as a single isomer with N atom of the 2-phenylpyridine ligand and S atom of the N-benzoyl thiourea derivatives coordinated in trans positions to the platinum metal as evidenced by using X-ray crystallography and NMR spectroscopy. All Pt(II) complexes show good luminescence properties at room temperature, both in dichloromethane solution and in solid state.     

Chemistry inside a Porphyrin Skeleton: Platinacyclopentadiene from Tellurophene

Platinum(II) binds to 21,23-ditelluraporphyrin forming a side-on complex, which can be easily transformed into an aromatic metallaporphyrin, that is, 21-platina-23-telluraporphyrin, with a platinacyclopentadiene unit built in the porphyrin skeleton in place of one pyrrole ring. The central platinum(II) ion with a CCNTe square-planar coordination sphere can be oxidized to platinum(IV) by chlorine, bromine, methyl iodide or allyl chloride to yield octahedral complexes. All platinatelluraporphyrins show dynamic behavior involving the platinum ion coordination sphere fluxionality and the porphyrin skeleton deformation, both in-plane and out-of-plane, as demonstrated by ¹H NMR spectroscopy.     

Mixed dimethyl sulfoxide-thiocarbamic ester complexes of platinum(II) halides

Summary The platinum(II) halidecis-[Pt(DMTC)(DMSO)X₂] andcis-[Pt(DETC)(DMSO)X₂](X=Cl or Br; DMSO=dimethyl sulfoxide; DMTC=EtOSCN-Me₂; DETC=EtOSCNEt₂) adducts and the platinum(II) and palladium(II) halide adducts,trans-[M(DETC)₂X₂] (M=Pt or Pd; X=Cl or Br), have been prepared. The complexes were characterized by i.r., and¹H and¹³Cn.m.r. spectroscopy. Both DMTC and DETC coordinate through the sulphur atoms. The 1:2 DETC complexes present the usualtrans configuration, whereas the presence of DMSO favourscis geometry in the mixed species.     

Coordination behavior and biopotency of N and S/O donor ligands with their palladium(II) and platinum(II) complexes

Some metal complexes of Schiff bases have been prepared by the interactions of palladium(II) and platinum(II) chloride with 5-chloro-1,3-dihydro-3-[2-(phenyl)-ethylidene]-2H-indol-2-one-hydrazinecarbothioamide(L¹H) and 5-chloro-1,3-dihydro-3-[2-(phenyl)-ethylidene]-2H-indol-2-one-hydrazinecarboxamide(L²H), in bimolar ratios. All the new compounds have been characterized by elemental analyses, conductance measurements, molecular weight determinations, IR and ¹H NMR spectral studies. The spectral data are consistent with a square planar geometry around Pd(II) and Pt(II) in which the ligands act as neutral bidentate and monobasic bidentate ligands, coordinating through the nitrogen and sulfur/oxygen atoms. Free ligands and their metal complexes were screened for their antimicrobial activity on different species of pathogenic fungi and bacteria and their biopotency has been discussed.     

Organoplatinum(II) Complexes with Nucleobase Motifs as Inhibitors of Human Topoisomerase II Catalytic Activity

Platinum(II) complexes bearing acetylide ligands containing nucleobase motifs are prepared and their impact on human topoisomerase II (TopoII) is evaluated. Both platinum(II) complexes [Pt^II(C^N^N)(C≡CCH₂R)] ( 1a , 1b , 1c ) and [Pt^II(tBu₃terpy)(C≡CCH₂R)]⁺ ( 2a , 2b , 2c ) (C^N^N=6‐phenyl‐2,2′‐bipyridyl, tBu₃terpy = 4,4′,4′′‐tri‐tert‐butyl‐2,2′:6′,2′′‐terpyridyl, and R=( a ) adenine, ( b ) thymine, and ( c ) 2‐amino‐6‐chloropurine) are stable in aqueous solutions for 48 hours at room temperature. The binding constants (K) for the platinum(II) complexes towards calf thymus DNA are in the order of 10⁵ dm³ mol^?1 as estimated by using UV/Vis absorption spectroscopy. Of the complexes examined, only complexes 1a , 1b , 1c are found to behave as intercalators. Both complexes 1a , 1b , 1c and 2a , 2b , 2c inhibit TopoII‐induced relaxation of supercoiled DNA, while 2c is the most potent TopoII inhibitors among the tested compounds. Inhibition of DNA relaxation is detected at nanomolar concentrations of 2c . All of the platinum(II) complexes are cytotoxic to human cancer cells with IC₅₀ values of 0.5–13.7 μM , while they are less toxic against normal cells CCD‐19 Lu.     

Square Planar Platinum(II) Complexes with N,S-Donor Ligands: Synthesis,Characterisation, DNA Interaction and Cytotoxic Activity

The platinum(II) complexes with N,S-donor ligand have been synthesised and characterised by physiological techniques like elemental, electronic, Fourier transform infrared, hydrogen-1 nuclear magnetic resonance (¹H NMR) and liquid chromatography–mass spectrometry spectra. The synthesised complexes have been checked for their DNA binding ability by absorption titration and viscosity measurement, and the results show that the complexes binds to herring sperm DNA (HS DNA) via covalent mode of binding. The DNA cleavage activity of synthesised complexes has been carried out by gel electrophoresis experiment using supercoiled form of pUC19 DNA, showing the unwinding of the negatively charged supercoiled DNA. Brine shrimp (Artemia cysts) lethality bioassay technique has been applied for the determination of toxic property of synthesised complexes in terms of micromolars.