Cationic Complexes Research Articles

Diphosphene with a phosphineborane tether and its rhodium complex.

A diphosphene ligand possessing a PP bond and a phosphineborane moiety in its molecule was synthesized. The reaction of the new bidentate diphosphene-phosphineborane ligand with [Rh(cod)2]BF4 provided a cationic diphosphene-rhodium complex with cis-coordination through the η1-PP and η2-BH3 moieties. The complex was applied to the coupling reaction of benzimidazole with cyclohexylallene. The complex also underwent a ligand exchange reaction with N-donor reagents such as N-methylpyrrolidine and N,N,N,N-tetramethylethylenediamine. In particular, the addition reaction of pyridine with the rhodium complex provided an equilibrium mixture of the rhodium complex, pyridine, the diphosphene-phosphineborane ligand, and [Rh(pyridine)2(cod)]BF4.

Influence of nature and macromolecular characteristics of carrier polymer on immobilization of bolaform ions

The study of the interactions of polyelectrolytes with organic ions and especially with ions of physiologically active substances is of particular. There are wide ranges of polymers used for these purposes, the most convenient “substrate” is considered to be synthetic carriers that are easily regulated during production. The object of research was the antiprotozoal drug azidine, widely used in veterinary practice, which, when dissolved in water, forms a complex bolaform cation: 4.41-diamidinodiazoaminobenzene. To develop a prolonged dosage form for veterinary medicine, the binding of this substance with various synthetic polymers such as polyvinylpyrrolidone, polyvinyl alcohol, polyacrylic, and polymethacrylic acids are important. In addition; their copolymers, was studied using physical and chemical methods. The influence of the nature of the carrier polymer, the molecular weight, and the conformation of macromolecules on the process of binding organic ions were also examined.The results obtained were confirmed by in vivo tests on cattle. A pattern is shown between the strength of the bond of the drug substance with the polymer carrier and the time of its preventive action.

DLPNO-CCSD(T) and DFT study of the acetate-assisted C-H activation of benzaldimine at [RuCl2(p-cymene)]2: the relevance of ligand exchange processes at ruthenium(II) complexes in polar protic media.

To gain mechanistic insights into the acetate-assisted cyclometallations of arylimines promoted by [RuCl2(p-cymene)]2 in polar protic media, DFT geometry optimizations (with M06 and ωB97X-D3 functionals and the cc-pVDZ-PP[Ru] basis set) followed by DLPNO-CCSD(T)/CBS energy evaluations were performed using benzaldimine as a model substrate and methanol as the solvent (with CPCM or SMD models). The calculation results show that coordination of the imine to an acetate ruthenium precursor is followed by anion (chloride or acetate) dissociation as the rate-determining step of the process. H-Bonding of two explicit MeOH to the anion reduces the calculated activation energy to ca. 23 kcal mol-1, in good agreement with the experimental half-life at room temperature. Subsequent AMLA/CMD C-H activation of the intermediate cationic complexes is a faster, reversible process. Alternative reaction pathways involving neutral diacetate ruthenium complexes offer AMLA/CMD transition state structures of lower energy but are precluded due to higher energy barriers for the initial ligand exchange processes at ruthenium. Solvent assistance accelerates the final chloride/acetate exchange processes on the cycloruthenate intermediates, particularly when compression in the condensed phase is taken into consideration. The performance of six DFT functionals (with the aug-pVTZ-PP[Ru] basis set) was assessed using the DLPNO-CCSD(T)/CBS reference energies. Neutral diacetate ruthenium complexes were incorrectly predicted as being kinetically relevant when using hybrid DFT methods (PBE0-D3(BJ), M06-2X or ωB97M-V). Good agreement between the calculated barrier heights and our benchmark energy results was obtained by using double-hybrid DFT methods. PWPB95 with D3(BJ) or D4 dispersion energy corrections was found to be the most accurate (ΔG≠ MUE of ca. 1 kcal mol-1). This study may aid our understanding of and help with further experimental investigations of synthetically useful carboxylate-assisted C-H bond functionalizations involving (N,C)-cyclometallated (p-cymene)Ru(II) intermediate complexes in sustainable polar protic solvents.

Dibenzoazepine hydrazine is a building block for N-alkene hybrid ligands: exploratory syntheses of complexes of Cu, Fe, and Li.

The new hydrazine 5H-dibenzo[b,f]azepin-5-amine (2) reacts with P- and Si-electrophiles via deprotonation to afford P(III)-, P(V)-, and TMS-hydrazides 3-8 and with carbonyl electrophiles via acid-free condensation to the N-substituted hydrazones 9-12 that are potential N-alkene ligands. While β-ketohydrazone 9 and α-dihydrazone 10 react with [Mes(Cu)]4, [Cu(NCCCH3)4]2PF6, and FeCl2(THF)1.5 to afford complexes devoid of alkene interaction, [Cu(OTf)]2·C6H6 reacts with the α-keto hydrazone 11 or with N,N dimethyl-hydrazone 12 to form the neutral dimeric Cu(I) complex 18 with bridging Cu(I)-alkene interactions or the tetrahedral cationic complex 19 in which 12 binds as a bidentate hydrazone-alkene ligand, respectively. The surprising stability of the alkene coordination in complexes 18 and 19 prevents substitutions with, e.g., PPh3.

Chiral Au(III) chelates exhibit unique NCI-60 cytotoxicity profiles and interactions with human serum albumin.

Au(III) bis(pyrrolide-imine) chelates are emerging as a class of versatile, efficacious metallodrug candidates. Here, we synthesised two enantiopure chiral ligands H2L1 and H2L2 (tetradentate cyclohexane-1,2-diamine-bridged bis(pyrrole-imine) derivatives). Metallation of the ligands with Au(III) afforded the chiral cationic complexes AuL1 and AuL2. The in vitro cytotoxicities of AuL1 and AuL2 determined in the NCI-60 single-dose drug screen were 56.5% and 89.1%, respectively. AuL1 was subsequently selected for a five-dose NCI-60 screen, attaining GI50, IC50, and LC50 values of 4.7, 9.3 and 39.8 μM, respectively. Hierarchical cluster analysis of the NCI-60 data indicated that the profile for AuL1 was similar to that of vinblastine sulfate, a microtubule-targeting vinca alkaloid. Reactions of AuL1 with glutathione (GSH) in vitro confirmed its susceptibility to reduction, Au(III) → Au(I), by intracellular thiols. Because human serum albumin (HSA) is responsible for transporting clinically deployed and investigational drugs, we studied the uptake of AuL1 and AuL2 by HSA to delineate how chirality impacts their protein-binding affinity. Steady-state fluorescence quenching data acquired on the native protein and data from site-specific probes showed that the compounds bind at sites close enough to Trp-214 (subdomain IIA) of HSA to quench the fluorophore. The bimolecular quenching rate constants, Kq, were ca. 102 times higher than the maximum diffusion-controlled collision constant of a biomolecule in water (1010 M-1 s-1), confirming that static fluorescence quenching was the dominant mechanism. The Stern-Volmer constants, KSV, were ∼104 M-1 at 37 °C, while the affinity constants, Ka (37 °C), measured ∼2.1 × 104 M-1 (AuL1) and ∼1.2 × 104 M-1 (AuL2) for enthalpy-driven ligand uptake targeting Sudlow's site I. Although far- and near-UV CD spectroscopy indicated that both complexes minimally perturb the secondary and tertiary structure of HSA, substantial shifts in the CD spectra were recorded for both protein-bound ligands. This study highlights the role of chirality in determining the cytotoxicity profiles and protein binding behaviour of enantiomeric Au(III) chelates.

A phenazine-based conjugated microporous polymer as a high performing cathode for aluminium-organic batteries.

One of the possible solutions to circumvent the sluggish kinetics, low capacity, and poor integrity of inorganic cathodes commonly used in rechargeable aluminium batteries (RABs) is the use of redox-active polymers as cathodes. They are not only sustainable materials characterised by their structure tunability, but also exhibit a unique ion coordination redox mechanism that makes them versatile ion hosts suitable for voluminous aluminium cation complexes, as demonstrated by the poly(quinoyl) family. Recently, phenazine-based compounds have been found to have high capacity, reversibility and fast redox kinetics in aqueous electrolytes because of the presence of a CN double bond. Here, we present one of the first examples of a phenazine-based hybrid microporous polymer, referred to as IEP-27-SR, utilized as an organic cathode in an aluminium battery with an AlCl3/EMIMCl ionic liquid electrolyte. The preliminary redox and charge storage mechanism of IEP-27-SR was confirmed by ex situ ATR-IR and EDS analyses. The introduction of phenazine active units in a robust microporous framework resulted in a remarkable rate capability (specific capacity of 116 mA h g-1 at 0.5C with 77% capacity retention at 10C) and notable cycling stability, maintaining 75% of its initial capacity after 3440 charge-discharge cycles at 1C (127 days of continuous cycling). This superior performance compared to reported Al//n-type organic cathode RABs is attributed to the stable 3D porous microstructure and the presence of micro/mesoporosity in IEP-27-SR, which facilitates electrolyte permeability and improves kinetics.

Intercalating a potassium-aqua complex cation into an α-MoO3 layer without reducing molybdenum: a potential storage system.

We have demonstrated a green aqueous synthesis of rod-shaped MoO3 material, [MoVI3O9{K(H2O)4}(CH3COO)]·H2O (2) intercalating potassium-aqua-complex acetate into its lamellar space, simply by ion-exchange of Co(II)-aqua-complex in compound [MoVI4O12(CH3COO)2{CoII(H2O)6}]·2H2O (1) by {K(H2O)4}+ in an aqueous solution of 1 and KCl. Compound 2 acts as a potential storage system of alkali metal ions.

Cyanido-bridged diplatinum(ii) complexes: ligand and solvent effect on aggregation and luminescence.

The association of platinum(ii)-based luminophores, which is caused by metal⋯metal and π-π stacking interactions, has been actively exploited in supramolecular construction of photofunctional molecular materials. Herein, we describe a series of bimetallic complexes [{Pt(C^N^/*N)}2(CN)][BAr4F], containing cyanido-bridged cyclometalated Pt(ii) chromophore fragments (HC^N^N = 6-phenyl-2,2'-bipyridine, (benzyltriazolyl)-phenylpyridine, and pyrazolyl-phenylpyridine; HC^N*N = N-pentyl-6-phenyl-N-(pyridin-2-yl)pyridin-2-amine; ^/* denote five/six-membered metallocycles). These compounds are intensely phosphorescent at room temperature showing quantum yields up to 0.73 in solution and 0.62 in the solid state, which are generally higher than those of the mononuclear relatives [Pt(C^N^/*N)(CN)]. The complex cations bearing sterically unhindered -C^N^N ligands readily assemble in solution, reaching the tetrameric species [{Pt(C^N^N)}2(CN)]44+ as suggested by diffusion NMR spectroscopy. The size of the aggregates can be regulated by the concentration, temperature, and polarity of the solvent that allows to alter the emission from green to near-IR. In the solid state, the maximum of low-energy luminescence is shifted up to 912 nm. The results show that photophysical properties of discrete complexes and the intermolecular aggregation can be substantially enhanced by utilizing the rigid bimetallic units giving rise to novel dynamic light emitting Pt(ii) systems.

Magnetic anisotropy and slow relaxation of magnetisation in double salts containing four- and six-coordinate cobalt(II) complex ions.

Four novel Co(II) coordination compounds 1-4 of the general formula [Co(Ln)2][Co(NCY)4]·mCH3CN (where Ln are tridentate ligands L1 = 2,6-bis(1-hexyl-1H-benzimidazol-2-yl)pyridine for 1 and 2; L2 = 2,6-bis(1-octyl-1H-benzimidazol-2-yl)pyridine for 3; L3 = 2,6-bis(1-dodecyl-1H-benzimidazol-2-yl)pyridine for 4, Y = O for 1, 3, and 4 and Y = S for 2; m = 0 for 1 and 3, m = 0.5 for 2 and m = 2 for 4) were prepared and characterised. The molecular structures of all four compounds consist of the hexacoordinate complex cation [Co(Ln)2]2+ and tetracoordinate complex anion [Co(NCY)4]2-, with distorted octahedral and tetrahedral symmetry of coordination polyhedra, respectively. The electronic structures of all compounds feature an orbitally non-degenerate ground state well-separated from the lowest excited state, which allows the analysis of the magnetic anisotropy by the spin Hamiltonian model. ZFS parameters, derived from both CASSCF-NEVPT2 calculations and magnetic data analysis, indicate that tetrahedral anions [Co(NCY)4]2- exhibit small axial parameters |D| spanning the range of 2.2 to 7.7 cm-1, while octahedral cations [Co(Ln)2]2+ display significantly larger |D| parameters in the range of 37 to 95 cm-1. For 1-3, the Fourier-transform infrared magnetic spectroscopy (FIRMS) revealed a reasonable transmission with a magnetic absorption around the expected value for the ZFS accompanied by features allowing to identify phonon frequencies and simulate spin-phonon couplings. Dynamic magnetic investigations unveiled the field-induced slow relaxation of magnetisation, with maximal relaxation times (τ) of 92(2) μs for 2 at 2 K and BDC = 0.3 T. The temperature evolution of τ was analysed using a combination of Orbach, direct and Raman relaxations (Ueff = 8(1) K (5.6 cm-1)) or Orbach, direct and spin-phonon induced relaxations (Ueff = 10.3(9) K (7.2 cm-1)). The rest of the complexes, namely 1, 3, and 4 show field-induced slow relaxation of magnetisation with τ smaller than 16 μs.

Studies on the behavior of the bis-complex of Pt(IV) with the tridentate ligand all-cis-2,4,6-triaminocyclohexane-1,3,5-triol in aqueous solutions

NMR spectroscopy and high-resolution mass spectrometry were applied to study the stability of the complex cation [Pt(taci)2]4+ known as ditaciplatin in aqueous solutions at varying acidity and in the presence of monodentate ligands. Ditaciplatin is a cationic part of the bis-complex of Pt(IV) with the tridentate ligand all-cis-2,4,6-triaminocyclohexane-1,3,5-triol (taci) with a composition [Pt(taci)2](CO3)2·6H2O (2A). It was found that the ditaciplatin complex is stable in solution at all of the studied conditions within the period of 7 days. Three new compounds were isolated in the experiments in solution, namely: [Pt(taci)2](CO3)1.5(OH)·7H2O (2B), [Pt(taci)2](Cl)4·H2O (2C) and [Pt(taci)2](NO3)4·2H2O (2D). 2B and 2C crystalize in triclinic crystal system P-1 and 2D – in monoclinic Р21/n. The cationic part of the compounds is ditaciplatin and the counterions depend on the synthetic conditions.

Synthesis, structural and magnetic properties of cobalt(ii) complexes with pyridine-based macrocyclic ligand containing two pyridine pendant arms.

With the aim of tuning the magnetic anisotropy, a series of Co(ii) complexes with the general formula of complex cations [Co(L)X]+, where X = Br- (1); I- (2); NCO- (3); NCS- (4a); N3 - (5), and [Co(L)(NCS)2] (4b), (L = a 17-membered pyridine-based N3O2-macrocyclic ligand containing two pyridin-2-ylmethyl pendant arms) were prepared and thoroughly characterized. The molecular structures for all complexes showed strongly distorted geometry in between octahedral and trigonal prismatic. The magnetic studies confirmed substantial magnetic anisotropy with positive values of D, the axial zero-field splitting parameter, but E/D ratios close to 1/3. This was supported by theoretical CASSCF calculations showing no significant effect of the co-ligands. Complex 4b was found to behave as a field-induced SMM.

Synergistic effect of metal cation and 1-dimethylamino-2-propanol on copper corrosion protection in alkaline solution

BackgroundCopper (Cu) has versatile applications in microelectronic industry and its corrosion protection in the manufacturing process is an important reliability issue. MethodsIn this study, mixed type corrosion inhibitor is formulated by complexation of metal cation (Ni2+) and tertiary amine (1-dimethylamino-2-propanol), and its synergistic effect on the corrosion protection of Cu in alkaline solution is systematically investigated. Electrochemical, microstructural, and chemical state analyses of the Cu surfaces with and without the inhibitor protection are performed to realize the protection efficacy of the mixed type inhibitor against corrosion. Significant findingsThe results show that the polarization resistance of the Cu surface is increased with the introduction of mixed type inhibitor (Ni2+-1-dimethylamino-2-propanol), achieving a higher inhibition efficiency of 48 % compared to the cation-free inhibitor (1-dimethylamino-2-propanol) of 25 %. The higher inhibition efficiency is attributed to the stronger adsorption capability of mixed type inhibitor on the Cu surface as confirmed by the X-ray photoelectron spectroscopy analysis and quantum chemical calculations.

Zirconium based metal-organic framework as highly efficient and acid-stable adsorbent for the rapid removal of Sr2+ and Cs+ from solution

Herein we present acid stable [Zr6(µ3-O)4(µ3-OH)4(OBA)4(OH)3(H2O)3(Me2NH2)]n (OBA = 4,4-oxy bis(benzoic acid)) (Zr(OBA) MOF) with the presence of cationic dimethyl ammonium groups were charge balanced with anionic Zr(OBA)nn– that is effective for removing Sr2+ and Cs+. This MOF shows distribution coefficients and record-high absorption capacities (Qm) of 353 mg/g for Sr2+ and 432.91 mg/g for Cs+ at pH 4, 112.75 mg/g for Sr2+ and 141.24 mg/g for Cs+ under 4 M HNO3 circumstances, and 221.5 mg/g for Sr2+ and 253.77 mg/g for Cs+ from simulated seawater. It was demonstrated that a significant excess of complex cations had no substantial influence on the removal of Sr2+ and Cs+ from simulated seawater and nuclear waste, which have been included with Sr2+ and Cs+. The Langmuir isotherm was well suited for Sr2+ and Cs+ adsorption onto MOF, confirming the existence of monolayer adsorption. This finding was made possible by investigating the Langmuir, Freundlich, and Temkin adsorption isotherms. The results of the experiments agree very well with pseudo-second-order kinetic studies, which leads one to believe that chemisorption is the primary mechanism. The measurement of zeta potential has indicated an electrostatic connection between the negatively charged surface of the MOF and positively charged Sr2+/Cs+ at various pH values. This interaction demonstrates that the adsorption capacity is relatively high. SEM-EDS elemental mapping, IR, and XPS analysis confirm the presence of Sr2+ and Cs+ on MOF - of Zr(OBA)@Sr and Zr(OBA)@Cs MOF after adsorption studies. Sr2+/Cs+ exchanged MOF were improved in order to get a clear image of the ion exchange process, and the binding energies of −87.31 for Zr(OBA)@Sr and −113.75 kJ/mol for Zr(OBA)@Cs, respectively. The dose, initial concentration of metal ions, pH solution, contact time, and other ions of Na+, K+, Ca2+, and Mg2+ that were already present affected the adsorption of Sr2+ and Cs+. Recycle studies of Zr(OBA) MOF show 80 % recovery of Sr2+ and Cs+ even after eight cycles.

Facile Access to Cationic Methylstannylenes and Silylenes Stabilized by E-Pt Bonding and their Methyl Group Transfer Reactivity.

We describe a family of cationic methylstannylene and chloro- and azidosilylene organoplatinum(II) complexes supported by a neutral, binucleating ligand. Methylstannylenes MeSn:+ are stabilized by coordination to PtII and are formed by facile Me group transfer from dimethyl or monomethyl PtII complexes, in the latter case triggered by concomitant B-H, Si-H, and H2 bond activation that involves hydride transfer from Sn to Pt. A cationic chlorosilylene complex was obtained by formal HCl elimination and Cl- removal from HSiCl3 under ambient conditions. The computational studies show that stabilization of cationic methylstannylenes and cationic silylenes is achieved through weak coordination to a neutral N-donor ligand binding pocket. The analysis of the electronic potentials, as well as the Laplacian of electron density, also reveals the differences in the character of Pt-Si vs. Pt-Sn bonding. We demonstrate the importance of a ligand-supported binuclear Pt/tetrel core and weak coordination to facilitate access to tetrylium-ylidene Pt complexes, and a transmetalation approach to the synthesis of MeSnII :+ derivatives.

Extension of Pt–Ag cluster units by incorporating silver salts

Abstract A sterically controlled Z-shaped Pt2Ag2 complex showed a metalation reaction with a Ag ion via the formation of the thermodynamically unfavorable Pt2Ag2 complex with U-shaped configuration. Multiple dative bond formation between Pt and an additional Ag ion endowed enough thermodynamic stability on the Pt2Ag3 cluster to overcome the unfavorable steric effect from bulky substituents on the ligands in the U-shaped structure. A single crystal X-ray structural analysis revealed dimerized structure of the cationic Pt2Ag3 complex units bridged by [Ag2(OTf)4]2− (OTf− = triflate anion) via strong Ag–π coordination with pyrazole moiety in the solid state. The heteropolynuclear complexes showed photoluminescence properties depending on the structure of the Pt–Ag clusters.

Structural Characterization, DFT Analysis and Catalysis by Highly Active Cationic Fe(II)‐Cu(I) Complexes in the Green Synthesis of Triazoles in Water

AbstractTwo bimetallic Fe(II)‐Cu(I) complexes, with tetrahedral Cu(I) center stabilized in a S2P2 environment, were synthesized and fully characterized using single crystal X‐ray diffraction, multinuclear NMR, IR and UV‐Visible spectroscopy techniques. Density functional theory with PBE0‐D3(BJ) functional was employed to elucidate the electronic features of these novel metal complexes. The computational analysis revealed that while all Cu(I) complexes adopted a tetrahedral geometry in the gas phase with shorter P−Cu(I) bonds than the S−Cu(I) bonds. These cationic complexes were highly active in the catalytic cycloaddition reaction of azides onto terminal alkynes. The CuAAC reaction were carried out at room temperature with as low as 1 mg (0.1 mol %) of catalyst loading to deliver high yields of the corresponding 1,4 adducts of 1,2,3‐triazoles in water under aerobic conditions.

Crystallographic Structure and Quantum-Chemical Analysis of Biologically Active Co(III)-Pyridoxal–Isothiosemicarbazone Complex

Semicarbazones and their transition metal complexes have been investigated as biologically active compounds. This study explores the synthesis, X-ray crystallographic structure, and characterization of a novel Co(III) complex cation with a pyridoxal-isothiosemicarbazone (PLITSC) ligand, [Co(PLITSC-2H)(NH3)3]+. The structure of the complex was further elucidated by the elemental analysis and spectroscopic techniques (IR and UV–VIS). Hirshfeld surface analysis was applied for the investigation of intermolecular interactions governing crystal structure. Optimization was performed at the B3LYP/6-31 + G(d,p)(H,C,N,O,S)/LanL2DZ(Co) level of theory without any geometrical constraints. The selected level of theory’s applicability was proven after comparing experimental and theoretical bond lengths and angles. The antibacterial activity of the complex towards E. coli and B. subtilis was determined and qualified as moderate compared to Streptomycin. The formation of free radical species in the presence of the complex was further verified in the fluorescence microscopy measurements. The molecular docking towards neural nitric-oxide synthase in the brain has shown that the complex structure and relative distribution of ligands were responsible for the binding to amino acids in the active pocket.

Four New Terpyridine Complexes Based Polyoxometalates with [W10O32]4– Anions as High‐Efficiency Dual‐Site Catalysis for Thioether Oxidation Reaction†

Comprehensive SummaryPolyoxometalates modified with complex cations have attracted increasing attention because of the fascinating properties and the controllable structures. By adjusting the synthesis conditions, four new terpyridine complexes based hybrid POMs, [(TPY‐H)CuCl]4 [W10O32]·2DMF·2H2O (1), [(TPY‐H)Cu(DMSO)(H2O)]2[W10O32]·2H2O (2), [(TPY‐H)2Cu]2[W10O32]·6DMSO·8H2O (3) and [(TPY‐Br)CuCl (DMSO)(H2O)]2[(TPY‐Br)CuCl]2[W10O32]·2DMSO·4H2O (4), were prepared by using ‘one‐pot’ method. Sing‐crystal X‐ray diffraction analyses, infrared radiation, etc., revealed the structural composition of compounds 1—4, which indicates that synthesis conditions have a directional regulatory effect on the compounds synthesis. Thioether oxidation catalytic reactions show 1—4 have good catalytic activities, and powder X‐ray diffraction and thermogravimetry analysis show 1—4 have superduper catalytic stability. Moreover, 4 has better catalytic activity because of the different structure of terpyridine complexes. Therefore, a possible mechanism of dual‐site catalysis by both cations and anions is proposed.

Synthesis and Structural Characterization of Zn(II) and Co(III) Complexes of Picolinoyl(4-ethylthiosemicarbazide)

Reaction of ZnCl2 and two equivalents of picolinoyl(4-ethylthiosemicarbazide), HL, in MeOH in the presence of a supporting base like Et3N results in the neutral complex [Zn(L)2] (1). A similar reaction of CoCl2, however, brings about a cobalt(III) cationic complex, which could be separated as its chloride salt [Co(L)2]Cl (2). The spectroscopic studies and X-ray structure analyses indicate that in 1 and 2, the metal ions are octahedrally coordinated by two (Npyridine, S, N1) chelates belonging to two singly deprotonated tridentate ligands {L–}.

Cytotoxic Activity of Some Half‐sandwich Rhodium(III) Complexes Containing 4,4’‐disubstituted‐2,2’‐bipyridine Ligands

AbstractThe synthesis and characterization of three compounds [Rh(η5‐C5Me5)Cl(N^N)]PF6 (N^N=4,4’‐disubstituted‐2,2’‐bipyridines, 1–3) are described. The cationic complexes contain the bidentate ligands N^N=4,4'‐di‐tert‐butyl‐2,2'‐bipyridine (1), N^N=4,4'‐dinonyl‐2,2'‐bipyridine (2) and N^N=4,4'‐diamino‐2,2'‐bipyridine (3). The complex salts were obtained by the bridge‐splitting reaction from the precursor [{Rh(η5‐C5Me5)(μ‐Cl)Cl}2] and subsequent salt metathesis affording their corresponding hexafluorido phosphate salts. All compounds were characterized by elemental analysis and spectroscopic means. Additionally, the molecular structure of compound 3 in the solid was determined by a single‐crystal X‐ray diffraction study. The cytotoxicity of all three compounds was examined by MTT assay against two cancer cell lines – HT‐29 (colon adenocarcinoma) and MCF‐7 (human breast adenocarcinoma) ‐ and normal human fibroblast cells (GM5657T). Compound 1 has moderate cytotoxicity against both cell lines, while compound 2 is seven to nine times more cytotoxic than cisplatin against MCF‐7 and HT‐29, respectively. In contrast to cisplatin, both compounds are more active against cancer cells than fibroblasts, thus showing some cancer selectivity.