Bis-conjugation of Bioactive Molecules to Cisplatin-like Complexes through (2,2′-Bipyridine)-4,4′-Dicarboxylic Acid with Optimal Cytotoxicity Profile Provided by the Combination Ethacrynic Acid/Flurbiprofen

A facile route to Pt^II complexes doubly functionalized with bioactive molecules through a bipyridine-type ligand is described. Initially, ligands L ^EE (containing two ethacrynic acid units), L ^EF (ethacrynic acid+flurbiprofen) and L ^EB (ethacrynic acid+biotin) were obtained in moderate to good yields from 2,2′-bipyridine-4,4′-dicarboxylic acid. Subsequent reaction of the ligands with [PtCl₂(DMSO)₂] afforded complexes [PtCl₂( L ^EE )] ( 2 ), [PtCl₂( L ^EF )] ( 3 ) and [PtCl₂( L ^EB )] ( 4 ) in high yields. All compounds were fully characterized by analytical and spectroscopic methods. Complexes 2 – 4 are highly stable in water/DMSO solution at 37 °C after 72 h, whereas progressive release of the bioactive fragments was detected in a cell culture medium. The compounds were assessed for their in vitro antiproliferative activity towards tumorigenic A2780, A2780cisR and Y79 cells and non-tumourigenic HEK293 cells. In particular, the combination of ethacrynic acid and flurbiprofen in 3 overcomes cisplatin-based resistance and provides strong cancer cell selectivity. Enzyme inhibition assays on human GST P1 and human COX-2 and cross-experiments with complex 1 , analogous to 2 – 4 but lacking bio-groups, revealed a clear synergy between the Pt^II frame and the bioactive organic components.     

Luminescent Cyclometalated Alkynylplatinum(II) Complexes with a Tridentate Pyridine‐Based N‐Heterocyclic Carbene Ligand: Synthesis,Characterization, Electrochemistry,Photophysics, and Computational Studies

A new class of luminescent alkynylplatinum(II) complexes with a tridentate pyridine‐based N‐heterocyclic carbene (2,6‐bis(1‐butylimidazol‐2‐ylidenyl)pyridine) ligand, [Pt^II(C^N^C)(C?CR)][PF₆], and their chloroplatinum(II) precursor complex, [Pt^II(C^N^C)Cl][PF₆], have been synthesized and characterized. One of the alkynylplatinum(II) complexes has also been structurally characterized by X‐ray crystallography. The electrochemistry, electronic absorption and luminescence properties of the complexes have been studied. Nanosecond transient absorption (TA) spectroscopy has also been performed to probe the nature of the excited state. The origin of the absorption and emission properties has been supported by computational studies.     

Palladium(II) Acetylide Complexes with Pincer‐Type Ligands: Photophysical Properties,Intermolecular Interactions,and Photo‐cytotoxicity

Two classes of cationic palladium(II) acetylide complexes containing pincer‐type ligands, 2,2′:6′,2′′‐terpyridine (terpy) and 2,6‐bis(1‐butylimidazol‐2‐ylidenyl)pyridine (C^N^C), were prepared and structurally characterized. Replacing terpy with the strongly σ‐donating C^N^C ligand with two N‐heterocyclic carbene (NHC) units results in the Pd^II acetylide complexes displaying phosphorescence at room temperature and stronger intermolecular interactions in the solid state. X‐ray crystal structures of [Pd(terpy)(C≡CPh)]PF₆ ( 1 ) and [Pd(C^N^C)(C≡CPh)]PF₆ ( 7 ) reveal that the complex cations are arranged in a one‐dimensional stacking structure with pair‐like Pd^II⋅⋅⋅Pd^II contacts of 3.349 Å for 1 and 3.292 Å for 7 . Density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) calculations were used to examine the electronic properties. Comparative studies of the [Pt(L)(C≡CPh)]⁺ analogs by ¹H NMR spectroscopy shed insight on the intermolecular interactions of these Pd^II acetylide complexes. The strong Pd−C_carbene bonds render 7 and its derivative sufficiently stable for investigation of photo‐cytotoxicity under cellular conditions.     

Observation of the Properties of a Single Unit of a Limited CDW Structure in a PtII/PtIV Host–Guest Binary System Based on a Square‐Shaped Complex

A macrocyclic tetranuclear platinum(II) complex [Pt(en)(4,4′‐bpy)]₄(NO₃)₈ ( 1 ?(NO₃)₈; en=ethylenediamine, 4,4′‐bpy=4,4′‐bipyridine) and a mononuclear platinum(IV) complex [Pt(en)₂Br₂]Br₂ ( 2 ?Br₂) formed two kinds of Pt^II/Pt^IV mixed valence assemblies when reacted: a discrete host–guest complex 1 ? 2 ?Br₁₀ ( 3 ) and an extended 1‐D zigzag sheet 1 ?( 2 )₃?Br₈(NO₃)₆ ( 4 ). Single crystal X‐ray analysis showed that the dimensions of the assemblies could be stoichiometrically controlled. Resonance Raman spectra suggested the presence of an intervalence interaction, which is typically observed for quasi‐1‐D halogen‐bridged M^II/M^IV complexes. The intervalence interaction indicates the presence of an isolated {Pt^II???X? Pt^IV? X???Pt^II} moiety in the structure of 4 . On the basis of electronic spectra and polarized reflectance measurements, we conclude that 4 exhibits intervalence charge transfer (IVCT) bands. A Kramers–Kronig transformation was carried out to obtain an optical conductivity spectrum, and two sub‐bands corresponding to slightly different Pt^II–Pt^IV distances were observed.     

Synthesis and Photophysical Properties of a Series of Biscyclometalated Platinum(II) Complexes on the Basis of a Tridentate 2,6-Diphenylpyridine

The complexes C,C-trans-[Pt(C^N^C)L] ^z [C^N^C is bisdeprotonated 2,6-diphenylpyridinate (dppy^2-); L = CO, Me2SO (dmso), ethylenediamine (en), CN^-, pyrazine (pz), P(C₆F₅)₃, 4,4'-bipyridine (4,4'-bpy)] were synthesized and characterized by ¹H NMR, electronic, and emission spectroscopy. Spectralluminescence properties of the chromophoric group (platinum-cyclometalating ligand) in the C,C-trans-bis-cyclometalated complexes depend on the nature of the noncyclometalating ligand L, which is explained by its donor-acceptor effects on the form of existence of the complex in solution.     

Mechanochemical synthesis of platinum(<Emphasis Type="SmallCaps">IV</Emphasis>) complexes with <Emphasis Type="Italic">N</Emphasis>-heterocyclic carbenes

A new method for the synthesis of complexes Pt^IV(NHC)X₄L (NHC is N-heterocyclic carbene of imidazole or benzimidazole series; X = Cl, Br; L is N-coordinated pyridine or NHC) based on mechanochemical oxidation of complexes Pt^II(NHC)X₂L with dichloroiodobenzene (PhICl₂) or pyridinium hydrobromide perbromide (PyHBr₃) was proposed. Mechanochemical activation led to reduction in the synthesis time and increase in the selectivity of halogenation and yields of the target Pt^IV complexes (74–98%) as compared to the reaction in solutions.     

Design,synthesis, pharmacological evaluation and DNA interaction studies of binuclear Pt(II) complexes with pyrazolo[1,5‐a]pyrimidine scaffold

Substituted pyrazolo[1,5‐a]pyrimidine ligands were synthesized by cyclization, using 3‐(thiophen‐2‐yl)‐1H‐pyrazol‐5‐amine with substituted enones (3‐phenyl‐1‐(pyridin‐2‐yl)prop‐2‐en‐1‐one) in presence of KOH and DMF as solvent to form cyclic aromatic compounds. The substituted pyrazolo[1,5‐a] pyrimidine based binuclear Pt^II complexes containing neutral tetradentated ligands have general formula [Pt₂(5a–5f)Cl₄], (where, (5a ‐5f) = pyrazolo[1,5‐a] pyrimidine ligand). This compounds were characterized by physicochemical and spectroscopic method like elemental analyses, UV‐Visible, FT‐IR, EDX, TGA, molar conductivity, magnetic susceptibility measurements, mass spectroscopy, ¹H and ¹³C NMR method. The square planar geometry was predicted by electronic spectral study. All Pt^II compounds were evaluated by antimicrobial assay, in vitro brine shrimp assay, in vivo cellular level bioassay using S. Pombe cells and anti‐tuberculosis study. LC₅₀ (50% lethal concentration) values of compounds are observed between 6.450 ‐ 102.07 μg/mL. UV‐vis absorption titration, competitive displacement assay, molecular docking and viscosity measurement were carried out to examine the binding type and binding strength of complexes. The binding studies suggest partial intercalative binding mode of the complexes and the observed binding constant (K_b) values are found in the order of 6d > 6b > 6c > 6a > 6e > 6 f. The anti‐proliferative cytotoxicity of the synthesized Pt^II complexes (6a‐6f) were tested against the HCT‐116 (Human Colorectal Carcinoma) cancer cell line.     

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.     

Novel platinum pyridinehydroxamic acid complexes: Synthesis,characterisation, X-ray crystallographic study and nitric oxide related properties

Herein, we describe the synthesis and characterisation of a novel class of Pt^II and Pt^IV pyridinehydroxamic acid (pyhaH) complexes of general formula cis-[Pt^IICl₂(x-pyhaH)₂] and cis-[Pt^IVCl₄(x-pyhaH)₂], respectively (where x = 3 or 4) in which the pyridinehydroxamic acid is coordinated to the platinum ion via the pyridine nitrogen only leaving the hydroxamic acid free to potentially release cytotoxic nitric oxide (NO). The crystal structure of the Pt^IV derivative, cis-[PtCl₄(4-pyhaH)₂] · 2CH₃OH is reported. To establish the biological effect of the uncoordinated hydroxamic acid moiety in the Pt^II compounds synthesised, the corresponding pyridinecarboxylic acid (pycaH) complexes of general formula cis-[Pt^IICl₂(x-pycaH)₂] (where x = 3 or 4) and the Pt^II pyridine (py) complex, cis-[Pt^IICl₂(py)₂] were synthesised and served as reference standards. The NO-releasing properties of each of the Pt^II compounds, the pyhaH and the pycaH ligands were studied. The Pt^II pyridinehydroxamic acid derivatives were found to induce potent in vitro effects attributable to either NO-release from the hydroxamic acid moiety and/or stimulation of inducible nitric oxide synthase of endothelial cells.     

Synthesis and characterization of platinum(II) and (IV) complexes containing hexamethyleneimine ligand: crystal structure of [Pt(hexamethyleneimine)2(cyclobutanedicarboxylato)]·H2O

A series of new platinum(II) and platinum(IV) complexes of the type [Pt^II(HMI)₂X] (where HMI=hexamethyleneimine, X=dichloro, sulfato, 1,1-cyclobutanedicarboxylato [CBDCA], oxalato, methylmalonato, or tatronato) and [Pt^IV(HMI)₂Y₂Cl₂] (where Y=hydroxo, acetato, or chloro) were synthesized and characterized by infrared (IR) spectroscopy, ¹³C and ¹⁹⁵Pt nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. Among the complexes synthesized, [Pt^II(hexamethyleneimine)₂(1,1-cyclobutanedicarboxylato)]·H₂O was examined by single-crystal X-ray diffraction. The slightly distorted square planar coordination environment of the platinum metal includes the amino group of the hexamethyleneimine (HMI) molecule and the oxygen atoms of the carboxylato ligand. The cyclobutanedicarboxylic acid (CBDCA) molecule adopts six-member chelating rings with platinum. Hydrogen bonding plays an important part in holding the crystal lattice together.     

Stabilization of Human Telomeric G‐Quadruplex and Inhibition of Telomerase Activity by Propeller‐Shaped Trinuclear PtII Complexes

Two novel propeller‐shaped, trigeminal‐ligand‐containing, flexible trinuclear Pt^II complexes, {[Pt(dien)]₃(ptp)}(NO₃)₆ ( 1 ) and {[Pt(dpa)]₃(ptp)}(NO₃)₆ ( 2 ) (dien: diethylenetriamine; dpa: bis‐(2‐pyridylmethyl)amine; ptp: 6′‐(pyridin‐3‐yl)‐3,2′:4′,3′′‐terpyridine), have been designed and synthesized, and their interactions with G‐quadruplex (G4) sequences are characterized. A combination of biophysical and biochemical assays reveals that both Pt^II complexes exhibit higher affinity for human telomeric (hTel) and c‐myc promoter G4 sequences than duplex DNA. Complex 1 binds and stabilizes hTel G4 sequence more effectively than complex 2 . Both complexes are found to induce and stabilize either antiparallel or parallel conformation of G4 structures. Molecular docking studies indicate that complex 1 binds into the large groove of the antiparallel hTel G4 structure (PDB ID: 143D) and complex 2 stacks onto the exposed G‐quartet of the parallel hTel G4 structure (PDB ID: 1KF1). Telomeric repeat amplification protocol assays demonstrate that both complexes are good telomerase inhibitors, with IC₅₀ values of (16.0±0.4) μM and (4.20±0.25) μM for 1 and 2 , respectively. Collectively, the results suggest that these propeller‐shaped flexible trinuclear Pt^II complexes are effective and selective G4 binders and good telomerase inhibitors. This work provides valuable information for the interaction between multinuclear metal complexes with G4 DNA.     

Synthesis, characterisation and catalytic activities of manganese(III) complexes of pyridoxal-based ONNO donor tetradenatate ligands

Reaction of Mn^II(CH₃COO)₂ with dibasic tetradentate ligands, N,N′-ethylenebis(pyridoxylideneiminato) (H₂pydx-en, I), N,N′-propylenebis(pyridoxylideneiminato) (H₂pydx-1,3-pn, II) and 1-methyl-N,N′-ethylenebis(pyridoxylideneiminato) (H₂pydx-1,2-pn, III) followed by aerial oxidation in the presence of LiCl gives complexes [Mn^III(pydx-en)Cl(H₂O)] (1) [Mn^III(pydx-1,3-pn)Cl(CH₃OH)] (2) and [Mn^III(pydx-1,2-pn)Cl(H₂O)] (3), respectively. Crystal and molecular structures of [Mn(pydx-en)Cl(H₂O)] (1) and [Mn(pydx-1,3-pn)Cl(CH₃OH)] (2) confirm their octahedral geometry and the coordination of ligands through ONNO(2-) form. Reaction of manganese(II)-exchanged zeolite-Y with these ligands in refluxing methanol followed by aerial oxidation in the presence of NaCl leads to the formation of the corresponding zeolite-Y encapsulated complexes, abbreviated herein as [Mn^III(pydx-en)]-Y (4), [Mn^III(pydx-1,3-pn)]-Y (5) and [Mn^III(pydx-1,2-pn)]-Y (6). These encapsulated complexes are used as catalysts for the oxidation, by H₂O₂, of methyl phenyl sulfide, styrene and benzoin efficiently. Oxidation of methyl phenyl sulfide under the optimized reaction conditions gave ca. 86% conversion with two major products methyl phenyl sulfoxide and methyl phenyl sulfone in the ca. 70% and 30% selectivity, respectively. Oxidation of styrene catalyzed by these complexes gave at least five products namely styrene oxide, benzaldehyde, benzoic acid, 1-phenylethane-1,2-diol and phenylacetaldehyde with a maximum of 76.9% conversion of styrene by 4, 76.3% by 5 and 76.0% by 6 under optimized conditions. The selectivity of the obtained products followed the order: benzaldehyde > benzoic acid > styrene oxide > phenylacetaldehyde > 1-phenylethane-1,2-diol. Similarly, ca. 93% conversion of benzoin was obtained by these catalysts, where the selectivity of the products followed the order benzil > benzoic acid > benzaldehyde-dimethylacetal. Tests for the recyclability and heterogeneity of the reactions have also been carried. Neat complexes are equally active. However, the recycle ability of encapsulated complexes makes them better over neat ones.     

Preparation of Dimethyl and Chloro/Methyl Complexes of Platinum(II) Supported by α‐Diimine Ligands: Trends in the Ease of Oxidation to Platinum(IV)

α‐Diimine ligands react with the platinum(II) alkyl complexes [(Me₂S)PtMe₂]₂ and (Me₂S)₂PtClMe to form (RDAB^R′)PtMe₂ and (RDAB^R′)PtClMe (RDAB^R′=RN=CR′−CR′=NR; R=2,6‐Me₂Ph, 2,6‐(CHMe₂)₂Ph, 3,5‐Me₂Ph, 3,5‐(CF₃)₂Ph, C₆H₁₁; R′=Me, H). The oxidation of these complexes with Cl₂, I₂, N‐chlorosuccinimide, [PtCl₆]²⁻ and (TMEDA)PtMe₂I₂ has been investigated. Attempts to determine the oxidation potentials of the Pt^II complexes electrochemically yielded only irreversible one‐electron oxidations. However, a qualitative ordering of increasing difficulty of oxidation has been determined for the series (RDAB^R′)PtMe₂<(RDAB^R′)PtClMe<(RDAB^R′)PtCl₂≪(RDAB^R′)PtMe(solvent)]⁺. The oxidation proceeds via a two‐electron inner‐sphere electron transfer from a bridged binuclear intermediate. The oxidation of (RDAB^R′)PtMe₂ by (TMEDA)PtMe₂I₂ exhibits characteristic third‐order kinetics, first‐order each in [Pt^II], [Pt^IV] and [I⁻]. Oxidation by a one‐electron process in MeCN solution results in a rapid subsequent disproportionation to Pt^IIMe and Pt^IVMe₃ cations with MeCN occupying the fourth or sixth coordination sites. Single‐crystal X‐ray structure determinations for [(2,6‐Me₂PhDAB^Me)PtMe₃(MeCN)]⁺[PtCl₆]_0.5(MeCN) and [(CyDAB^H)PtMe₃(MeCN)]⁺[PtCl₆]_0.5(MeCN) are reported.     

Synthesis and characterization of platinum(II) and (IV) complexes containing hexamethyleneimine ligand: crystal structure of [PtII(hexamethyleneimine)2(cyclobutanedicarboxylato)]·H2O

A series of new platinum(II) and platinum(IV) complexes of the type [Pt^II(HMI)₂X] (where HMI=hexamethyleneimine, X=dichloro, sulfato, 1,1-cyclobutanedicarboxylato [CBDCA], oxalato, methylmalonato, or tatronato) and [Pt^IV(HMI)₂Y₂Cl₂] (where Y=hydroxo, acetato, or chloro) were synthesized and characterized by infrared (IR) spectroscopy, ¹³C and ¹⁹⁵Pt nuclear magnetic resonance (NMR) spectroscopy and elemental analysis. Among the complexes synthesized, [Pt^II(hexamethyleneimine)₂(1,1-cyclobutanedicarboxylato)]·H₂O was examined by single-crystal X-ray diffraction. The slightly distorted square planar coordination environment of the platinum metal includes the amino group of the hexamethyleneimine (HMI) molecule and the oxygen atoms of the carboxylato ligand. The cyclobutanedicarboxylic acid (CBDCA) molecule adopts six-member chelating rings with platinum. Hydrogen bonding plays an important part in holding the crystal lattice together.     

Cytotoxic dimeric half-sandwich Ru(II), Os(II) and Ir(III) complexes containing the 4,4′-biphenyl-based bridging ligands

A series of dinuclear half-sandwich Ru(II), Os(II) and Ir(III) complexes [Ru₂(μ-Lⁿ)(η⁶-pcym)₂Cl₂](PF₆)₂ ( 1 , 4 ), [Os₂(μ-Lⁿ)(η⁶-pcym)₂Cl₂](PF₆)₂ ( 2 , 5 ) and [Ir₂(μ-Lⁿ)(η⁵-Cp*)₂Cl₂](PF₆)₂ ( 3 , 6 ), based on 4,4′-biphenyl-based bridging Schiff base ligands N,N′-(biphenyl-4,4′-diyldimethylidyne)bis-2-(pyridin-2-yl)methanamine (L¹; for 1 – 3 ) and N,N′-(biphenyl-4,4′-diyldimethylidyne)bis-2-(pyridin-2-yl)ethanamine (L²; for 4 – 6 ) is reported; pcym = 1-methyl-4-(propan-2-yl)benzene, Cp* = pentamethylcyclopentadienyl. The complexes were characterized by relevant analytical techniques (i.e. elemental analysis, FT-IR, NMR, ESI-MS), and their in vitro cytotoxicity was assessed at six cancerous and two non-cancerous (healthy) human cell lines. Overall, complexes 4 – 6 , containing the L² bridging ligand, revealed higher cytotoxicity as compared with 1 – 3 and, thus, they were studied in greater detail. The best-performing complex 6 exceeded at least twice the in vitro cytotoxicity of cisplatin and showed high selectivity towards the cancer cells over the normal ones, including the primary culture of human hepatocytes. In contrast to cisplatin, complexes 4 – 6 did not induce the cell cycle modification of the treated A2780 human ovarian carcinoma cells (studied by flow cytometry and Western blot analysis). High levels of superoxide anion were induced by complexes 4 – 6 at the A2780 cells. The levels of activated forms of Caspase-3 and Caspase-8 at the A2780 cells treated by Ru(II) complex 4 were comparable with cisplatin, while complexes 5 and 6 had only a minor effect on activation of these caspases.     

Syntheses and structures of copper(II) and nickel(II) complexes with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-(4,4′-bithiazole-2,2′-diyl)diacetimidamide ligands: in vitro cytotoxicities and DNA-binding properties

Two complexes of general formula, [M(DABTA)]NO₃ [M = Cu^II (1) or Ni^II (2), DABTA = N,N′-(4,4′-bithiazole-2,2′-diyl)diacetimidamide], have been synthesized and characterized by elemental analyses, molar conductivity measurements, IR and electronic spectra studies and single-crystal X-ray diffraction. The crystal structures show that the two complexes have similar molecular structures in which each metal atom has a square-planar coordination environment. Hydrogen bonding interactions link each complex into a 2-D infinite network. The DNA-binding properties and cytotoxicities of the complexes were investigated. The results suggest that the two complexes can interact with DNA by intercalation, with binding affinities following the order of 1 > 2, which is consistent with their in vitro cytotoxicities.     

A one‐dimensional chloride‐bridged PtII/PtIV mixed‐valence complex with a 4‐[(4‐hydroxyphenyl)diazenyl]benzenesulfonate counter‐ion

The title compound, catena‐poly[[[bis(ethylenediamine‐κ²N,N′)platinum(II)]‐ μ‐chlorido‐[bis(ethylenediamine)platinum(IV)]‐μ‐chlorido] tetrakis{4‐[(4‐hydroxyphenyl)diazenyl]benzenesulfonate} dihydrate], {[Pt^IIPt^IVCl₂(C₂H₈N₂)₄](HOC₆H₄N=NC₆H₄SO₃)₄·2H₂O}_n, has a linear chain structure composed of square‐planar [Pt(en)₂]²⁺ (en is ethylenediamine) and elongated octahedral trans‐[PtCl₂(en)₂]²⁺ cations stacked alternately, bridged by Cl atoms, along the b axis. The Pt atoms are located on an inversion centre, while the Cl atoms are disordered over two sites and form a zigzag ...Cl—Pt^IV—Cl...Pt^II... chain, with a Pt^IV—Cl bond length of 2.3140 (14) Å, an interatomic Pt^II...Cl distance of 3.5969 (15) Å and a Pt^IV—Cl...Pt^II angle of 170.66 (6)°. The structural parameter indicating the mixed‐valence state of the Pt atom, expressed by δ = (Pt^IV—Cl)/(Pt^II...Cl), is 0.643.     

Synthesis, 119Sn, 13C and 195Pt NMR studies of five-coordinate rhodium(I), iridium(I) and platinum(II) complexes containing three trichlorostannate ligands

The synthesis and ¹¹⁹Sn NMR characteristics of new five-coordinate tris(trichlorostannato) complexes of Rh^I, Ir^I and Pt^II are reported. The Rh^I and Ir^I complexes are complex dianions of the form (PPN)₂[M(SnCl₃)₃L₂] where L can be CO, CN (cyclohexyl) or L₂, a diolefin such as 1,5-COD or NBD (norbornadiene). The anionic platinum complexes (PPN)[Pt(SnCl₃)₃L₂] contain similar L ligands. A number of neutral monotrichlorostannato complexes of type [M(SnCl₃)L₄] including [Ir(SnCl₃)(NBD)(1,5-COD)] have been prepared and characterized. Their δ(¹¹⁹Sn), δ(¹³C), δ(¹⁹⁵Pt) as well as ¹J(¹⁰³Rh, ¹¹⁹Sn), ¹J(¹⁹⁵Pt, ¹¹⁹Sn), ²J(¹¹⁹Sn, ¹¹⁷Sn) and ²J(¹¹⁹Sn, ¹³C) data are given. A trans influence series, based on ¹J(¹⁹⁵Pt, ¹¹⁹Sn), reveals the following sequence: H^? > PR₃ > AsR₃ > SnCl₃^? > olefin > Cl^?.     

Reversible Mechanical Interlocking of D‐Shaped Molecular Karabiners bearing Coordination‐Bond Loaded Gates: Route to Self‐Assembled [2]Catenanes

Complexation of 1,4‐phenylenebis(methylene) diisonicotinate, L1 , with cis‐protected Pd^II components, [Pd( L′ )(NO₃)₂], in an equimolar ratio yielded binuclear complexes, 1 a – d of [Pd₂( L′ )₂( L1 )₂](NO₃)₄ formulation where L′ stands for ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′‐bipyridine (bpy), and phenanthroline (phen). The combination of 4,4′‐bipyridine, L2 , with the cis‐protected Pd^II units is known to yield molecular squares, 2 a – d . However, 2 b – d coexist with the corresponding molecular triangles, 3 b – d . Combination of an equivalent each of the ligands L1 and L2 with two equivalents of cis‐protected Pd^II components in DMSO resulted in the D ‐shaped heteroligated complexes [Pd₂( L′ )₂( L1 )( L2 )](NO₃)₄, 4 a – d . Two units of the D ‐shaped complexes interlock, in a concentration dependent fashion, to form the corresponding [2]catenanes [Pd₂( L′ )₂( L1 )( L2 )]₂(NO₃)₈, 5 a – d under aqueous conditions. Crystal structures of the macrocycle [Pd₂(tmeda)₂( L1 )( L2 )](PF₆)₄, 4 b′′ , and the catenane [Pd₂(bpy)₂( L1 )( L2 )]₂(NO₃)₈, 5 c , provide unequivocal support for the proposed molecular architectures.     

Synthesis and antimicrobial evaluation of coordination compounds containing 2,2′-bis(3-aminopyridyl) diselenide as ligand

The reaction between 2,2′-bis(3-aminopyridyl) diselenide (L) and metal transition salts results in the formation of molecular or cluster complexes. The structural elucidation of the synthesized complexes [CuCl₂(L)] ( 1 ), [Cu(3-NH₂PySeO₂)₂]·2H₂O ( 2 ), [Cu₄(3-NH₂PySe)₄]·dimethylformamide ( 3 ), [CoCl₂(L)] ( 4 ), [ZnCl₂(L)] ( 5 ), and [Ag₆(3-NH₂PySe)₆] ( 6 ) demonstrates the coordination of nitrogen atoms to Cu^II, Co^II, and Zn^II, and that of the selenium atoms to Cu^I and Ag^I, which agrees with Pearson’s hard and soft acids and bases (HSAB) theory. Furthermore, the oxidation of selenium with the formation of 3-aminopyridylseleninate [3-NH₂PySeO₂]⁻ bonded to the copper atom was observed in complex 2 . The antimicrobial action of complexes 1 , 2 , 4 , and 5 was evaluated against Mycobacterium fortuitum, Mycobacterium massiliense, and Mycobacterium abscessus. It was observed that all these complexes have potential antimicrobial activity compared with the free ligand and metal salts used in the synthesis.