Silver(I)-mediated isomerisation of trans-[RuCl2(P-P)2] (P-P=4-membered ring chelate diphosphine ligand) and its application in the syntheses of [RuCl(L)(P-P)2]+ (L=neutral ligand)

Conversion of trans-[RuCl₂(P-P)₂] (P-P=4-membered chelate diphosphine) to cis is facilitated by treatment with AgOTf or AgBF₄ in 1,2-dichloroethane, which gives mixtures of Ru–Cl–Ag heterobimetallic complexes with cis stereochemistry at Ru(II), characterised by ³¹P{¹H} and ¹H NMR spectroscopy and by FAB mass spectrometry. Treatment of these mixtures with neutral ligands (CO, CH₃CN) gives cis-[RuCl(L)(P-P)₂]⁺, whereas simultaneous treatment of trans-[RuCl₂(P-P)₂] with L and Ag(I) salt gives trans-[RuCl(L)(P-P)₂]⁺.     

The trigonal-bipyramidal [ReOI2(PPh3)2] — The first monomeric oxorhenium(IV) complex with monodentate ligands only

The reaction of cis-[Re^VO₂I(PPh₃)₂] with 2-(3,5-dimethylpyrazol-1-yl)benzothiazole (dbt) in ethanol led to the isolation of the trigonal-bipyramidal oxorhenium(IV) complex trans-[ReOI₂(PPh₃)₂] (1). The complex is the first example of a monomeric oxo complex of rhenium(IV). Complex 1 was characterized by FTIR, ¹H NMR, microanalysis and single crystal X-ray diffraction.     

Synthesis and characterization of trans-[Ru(NO)Cl(L)4](PF6)2 (L = isonicotinamide; 4-acetylpyridine) and related species

The trans-[RuCl₂(L)₄], trans-[Ru(NO)Cl (L)₄](PF₆)₂ (L = isonicotinamide and 4-acetylpyridine) and trans-[Ru(NO)(OH)(py)₄]Cl₂ (py = pyridine) complexes have been prepared and characterized by elemental analysis, UV–visible, infrared, and ¹H NMR spectroscopies, and cyclic voltammetry. The MLCT band energies of trans-[RuCl₂(L)₄] increase in the order 4-acpy < isn < py. The reduction potentials of trans-[RuCl₂(L)₄] and trans-[Ru(NO)Cl(L)₄]²⁺ increase in the order py < isn < 4-acpy. The stretching band frequency, ν_NO, of the nitrosyl complexes ranges from 1913 to 1852 cm^?1 indicating a nitrosonium character for the NO ligand. Due to the large π-acceptor ability of the equatorial ligands, the coordinated water is much more acidic in the water soluble trans-[Ru(NO)(H₂O)(py)₄]³⁺ than in trans-[Ru(NO)(H₂O)(NH₃)₄]³⁺.     

Isomerism in bis(phenylselenolato)bis(triphenylphosphine)platinum(II): the crystal and molecular structures of cis- and trans-[Pt(SePh)2(PPh3)2]

The reaction of cis-[PtCl₂(PPh₃)₂] and NaSePh in benzene produces a mixture of cis- and trans-isomers of the monomeric platinum complex [Pt(SePh)₂(PPh₃)₂]. The low-temperature X-ray structures of both isomers are reported. The structure of cis-[Pt(SePh)₂(PPh₃)₂] is the first crystallographic characterized cis-isomer of mononuclear platinum(II) complex containing only non-chelating organoselenolato and phosphine ligands.     

Stereoselective ion association of [Co(en)2(phen)]3+ with metal complex anions

Ion association constants of Λ- and Δ-[Co(en)₂(phen)]³⁺ (en=ethylenediamine and phen=1,10-phenanthroline) with Δ-[Co(mal)₂(gly)]²⁻ (mal=malonate and gly=glycinate), Δ-[Co(ox)₂(gly)]²⁻ (ox=oxalate), and Δ-C₁-cis(N)-[Co(ox)(gly)₂]⁻ in aqueous solution were determined at 25°C and an ionic strength of 0.01 M by the conductivity method. The preferred ion pair between [Co(en)₂(phen)]³⁺ and the above three complex anions was ΔΔ (homochiral combination), contrasting with a heterochiral (ΛΔ) preference for the ion pair between [Co(en)₃]³⁺ and the same complex anions. In addition, the discrimination factors, K(ΔΔ)/K(ΛΔ), in the [Co(en)₂(phen)]³⁺ systems were appreciably larger than those in the corresponding [Co(en)₃]³⁺ systems. The results are interpreted in terms of the interaction mode different from that of [Co(en)₃]³⁺, and the ion association model responsible for the chiral recognition by [Co(en)₂(phen)]³⁺ is proposed.     

A tungstoantimonate coordinated by dmso groups, [Sb2W20(OH)2(dmso)2O66]8−

A novel dmso-coordinated heteropolytungstate [Sb₂W₂₀(OH)₂(dmso)₂O₆₆]⁸⁻ (1) has been successfully isolated as [Ru(bpy)₃]²⁺ salts by routine synthetic reaction in mixed solutions with dmso and water. The compound was characterized by spectroscopic methods as well as by X-ray single crystal structure analysis. The compound represents a tungstoantimonate framework with two W–O–S(CH₃)₂ bonds.     

A new 2D HgII coordination polymer containing novel coordination mode of 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo) ligand, [Hg(μ-bpo)2(N3)2]n: Spectroscopic,thermal, fluorescence and structural studies

A new two-dimensional Hg^II coordination polymer containing 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (bpo) and azide anions, [Hg(μ-bpo)₂(N₃)₂]_n, has been synthesized and characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR spectroscopy and structurally determined by X-ray single-crystal diffraction. The thermal stability of compound [Hg(μ-bpo)₂(N₃)₂]_n was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The single-crystal X-ray data shows that ligand bpo is bridged via one pyridyl nitrogen and one oxadiazole nitrogen atom, as a novel coordination mode of the ligand bpo. Furthermore, the ligand and complex are luminescent in the solid state, with emission maxima in the visible light region (λ_max = 470 nm for both bpo and [Hg(μ-bpo)₂(N₃)₂]_n).     

Polymeric structures of a pair of linear,dicarboxylate (tpy)2Ru2+ analogues

The preparation and solid-state structures of homoleptic Ru(II) complexes based on the ligands 4′-(4-carboxyphenyl)tpy (L₁) (where tpy = 2,2′:6′,2″-terpyridine) and 4′-(4-carboxyphenyl)-4,4″-di-(tert-butyl)tpy (L₂) are described. Both complexes are found to possess polymeric solid-state structures due to hydrogen-bonding interactions. The first complex, [Ru(L₁)₂]²⁺, exhibits a more closely-packed structure relative to that of [Ru(L₂)₂]²⁺, which was found to have a porous solid-state structure due to the steric bulk of the tert-butyl groups.     

pH responsive “off–on–off” luminescent switch of a novel ruthenium(II) complex [Ru(bpy)2(pipipH2)]2+

A novel ruthenium(II) complex, [Ru(bpy)₂(pipipH₂)](ClO₄)₂ · H₂O (1) (pipipH₂ = 2-(4-(1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)-1H- imidazo[4,5-f][1,10] phenanthroline, bpy = 2,2^′-bipyridine) has been found to act as a luminescent pH switch with extraordinary sensitivity through protonation and deprotonation of the bis-imidazole-containing ligand pipipH₂ in aqueous solution at room temperature.     

Oxotungsten(VI) complexes with amino(phenolate)alcoholate ligand

The reaction between tungsten(VI) complex [W(eg)₃] (eg = 1,2-ethanediolato dianion) and a phenolic ligand precursor 2,4-di-tert-butyl-6-(((2-hydroxyethyl)(methyl)amino)methyl)phenol (H₂L) affords a monomeric oxotungsten complex [WO(eg)(L)]. This complex reacts further with Me₃SiCl, which leads to the displacement of ethanediolato ligand from the complex unit and formation of cis- and trans-isomers of corresponding dichloro complex [WOCl₂(L)]. Identical dichloro complexes were also prepared by the reaction between H₂L and WOCl₄. Molecular structure of [WO(eg)(L)] was verified by X-ray crystallography.     

Reactions of benzene based half sandwich ruthenium(II) complex with 2,6-bis((phenylseleno)methyl)pyridine: Preferential substitution of ring resulting in a catalyst of high activity for oxidation of alcohols

[2,6-Bis((phenylseleno)methyl)pyridine] (L) a (Se, N, Se) pincer ligand synthesized by reacting PhSe^? (in situ generated) with 2,6-bis(chloromethyl)pyridine reacts with [{(η⁶-C₆H₆)RuCl(μ-Cl)}₂] (2:1 molar ratio) by preferential substitution of ring resulting in the first Ru-(Se, N, Se) pincer ligand complex, mer-[Ru(CH₃CN)₂Cl(L)][PF₆](1).H₂O. Similar reaction in 4:1 molar ratio results in mer-[Ru(L)₂][ClO₄]₂(2). The ¹H, ¹³C{¹H} and ⁷⁷Se{¹H} NMR spectra of L, 1 and 2 were found characteristic. The single crystal structures of 1 and 2 were studied by X-ray crystallography. The geometry of Ru in both the complexes is distorted octahedral. The Ru–Se distances are in the ranges 2.4412(16)–2.4522(16) and 2.4583(14)–2.4707(15) ? respectively for 1 and 2. The structural solutions from the crystal data in case of 2, due to inferior quality of its crystals, are suitable for supporting bonding mode of L with Ru(II) only. The 1 shows high catalytic activity for oxidation of primary and secondary alcohols (TON up to 9.7 × 10⁴).     

Synthesis and characterization of Cu(I) and Zn(II) complexes with new sulfur-bearing isoxazole- or pyrazole-based ligands

The synthesis of the new ligands 6-(5-methyl-1,2-oxazol-3-yl)-2,3-dihydro-5H-[1,4] dithiino[2,3-c]pyrrole-5,7(6H)-dione (isox′) and 6-(3-methyl-1H-pyrazol-5-yl)-2,3-dihydro-5H-[1,4]dithiino[2,3-c]pyrrole-5,7(6H)-dione (pyraz′) and their coordination chemistry toward Cu(I) and Zn(II), was studied. The ligands and their complexes were characterized using a combination of either multinuclear NMR (¹H and ¹³C{¹H}), HRMS, FTIR or Uv–Vis spectroscopy. The solid state structures of ligand isox′ and complexes [Cu(pyraz′)₂]OTf and [Zn(OOCCF₃)₂(pyraz′)₂] were determined. Interestingly, isox′ presents a yellow luminescence in its free form. Additionally, the ability of isox′ to coordinate as an N–O bidentate ligand or as an N–S bridge between two copper centers, forming a coordination polymer, is studied. The solid state structure of this Cu(I)-isox′ 1D coordination polymer is also reported.     

Initial use of 1,1′-oxalyldiimidazole for inorganic synthesis: Decomposition of the ligand as a means to the preparation of an imidazole- and oxalate(-2)-containing, 1D copper(II) complex

The use of 1,1′-oxalyldiimidazole, (im)COCO(im), for the synthesis of coordination complexes is explored for the first time. The [Cu₂(O₂CMe)₄(H₂O)₂]/(im)COCO(im) reaction system in 96% EtOH yields the new, 1D coordination polymer [Cu(ox)(Him)₂]_n (1), where Him is the neutral imidazole and ox^2? is the oxalate(-2) ligand. A mechanism for the hydrolytic decomposition of the ligand is proposed. Complex 1 comprises neutral, zigzag chains with the η¹:η¹:η¹:η¹:μ (2.1111 using Harris notation) ox^2? ligand bridging two neighboring Cu^II centers; two cis Him groups complete a Jahn–Teller distorted octahedral geometry at the metal. The dc, variable-temperature magnetic susceptibility data for the complex reveal antiferromagnetic Cu^II?Cu^II exchange interactions.     

Effect of conformation of the arylamine-DNA adduct on the sensitivity of [Ru(phen)2(dppz)]2 + complex

DNA damage by endogenous/exogenous chemicals and ionizing radiation results in the formation of abasic sites, alkylation products, oxidative lesions and covalent-DNA adducts. The covalent DNA adducts adopt different conformations that might lead to various types of mutations. In the present study, we investigated the interaction of different Ru(II) polypyridyl complex, [Ru(phen)₂(dppz)]^2 + (phen: 1,10-phenanthroline; dppz: dipyrido[3,2-a:2′,3′-c]phenazine) with oligonucleotide sequences containing either [N-(2′-deoxyguanosin-8-yl)-2-aminofluorene] (AF-dG) or [N-(2′-deoxyguanosin-8-yl)-2-acetylaminofluorene] (AAF-dG) adduct. The modification of the oligonucleotides with the arylamines was characterized by UV–visible and MALDI-TOF spectroscopy. The results of thermal denaturation studies of oligonucleotide with Ru(II) complex indicate that Ru(II) complex stabilize the arylamine adducts better than control oligonucleotide. The integrated luminescence intensity of the Ru(II) complex was increased two-fold in AAF-dG adduct compared to control while a reverse trend was observed with AF-dG adduct. The addition of quencher enhanced the luminescence ratio between AF-modified and control duplex by 1.5 fold compared to 3.6 to 6-fold in AAF-dG adduct. The results from this study demonstrate the role of conformational heterogeneity of the arylamine-dG adduct in the binding of the Ru(II) complex and also provides us insight on the development of new probes.     

Homoleptic complexes [Ru(L-L)3]2+ (L-L=diphosphine,diarsine)

Homoleptic Ru(II)–diphosphine and Ru(II)–diarsine complexes [Ru(L-L)₃](OTf)₂ (L-L=Me₂P(CH₂)_nPMe₂; n=1, dmpm; n=2, dmpe) and 1,2-C₆H₄(AsMe₂)₂ (diars) have been isolated, in which the Ru(II) state is stabilised to an unprecedented degree, and the crystal structure of [Ru(diars)₃]Cl₂ has been determined.     

Coexistence of two distinct axial ligands and their thermo-induced substitution in trans-[FeL2(NCS)2][FeL2(CH3OH)2](NCS)2 (L = 4-amino-3-(p-chlorophenyl)-5-(2-pyridyl)-1,2,4-triazole)

A novel iron(II) complex, trans-[FeL₂(NCS)₂][FeL₂(CH₃OH)₂](NCS)₂ (1) with 4-amino-3-(p-chlorophenyl)-5-(2-pyridyl)-1,2,4-triazole (L) has been successfully synthesized and characterized. X-ray crystallography analysis shows that 1 is the first example in the mononuclear triazole-based complexes consisting of two distinct molecules: trans-[FeL₂(NCS)₂] and trans-[FeL₂(CH₃OH)₂](NCS)₂ with each octahedral iron(II) center coordinated axial by two NCS⁻ ions in Fe1 but two MeOH molecules in Fe2. Moreover, 1 can lose two MeOH molecules at 220 °C to form trans-[FeL₂(NCS)₂] (2) which can be transformed to 1 when recrystallizing 2 in methanol. Both 1 and 2 are high-spin species in the range of 1.8–300 K.     

Synthesis and characterization of half-sandwich Ir and Ru complexes containing Mnt ligand (Mnt = maleonitriledithiolate)

The reaction of [Cp¹IrCl₂]₂ and [(p-Cymene)RuCl₂]₂ with disodium maleonitriledithiolate (Na₂Mnt) yield the 16-electron complexes Cp¹Ir(Mnt) (1) and [(p-Cymene)Ru(Mnt)] (2). Complexes 1 and 2 can further react with PPh₃ to form the corresponding 18-electron complexes Cp¹Ir(Mnt)PPh₃ (3) and [(p-Cymene)Ru(Mnt)PPh₃] (4). All complexes have been fully characterized by IR and NMR spectroscopy, as well as elemental analysis. The molecular structures of 1 and 4 have been confirmed by X-ray crystallography.     

Dendrimer-like cyanoruthenate anions with high potential connectivity derived from a [Ru(bpym)3]2+ core

Reaction of [Ru(bpym)₃]²⁺ (bpym = 2,2′-bipyridmidine) with hexacyanoruthenate under forcing conditions affords a mixture of the trinuclear species [(bpym)Ru{(µ-bpym)Ru(CN)₄}₂]^2?, [1]^2?, and the tetranuclear species [Ru{(µ-bpym)Ru(CN)₄}₃]^4?, [2]^4?, in which two or three (respectively) of the peripheral vacant bpym binding sites of [Ru(bpym)₃]²⁺ are occupied by {Ru(CN)₄}^2? fragments. Thus, [1]^2? and [2]^4? have eight and twelve externally-directed cyanide groups respectively for use in forming high connectivity coordination networks. The crystal structure of HK[1]·2MeOH·6.5H₂O reveals a one-dimensional ladder structure in which [1]^2? anions are connected by (i) cyanide/K⁺ and (ii) bpym/K⁺ coordination interactions.     

Ruthenium Complexes with 2-Pyridin-2-yl-1H-benzimidazole as Potential Antimicrobial Agents: Correlation between Chemical Properties and Anti-Biofilm Effects

Antimicrobial resistance is a growing public health concern that requires urgent action. Biofilm-associated resistance to antimicrobials begins at the attachment phase and increases as the biofilms maturate. Hence, interrupting the initial binding process of bacteria to surfaces is essential to effectively prevent biofilm-associated problems. Herein, we have evaluated the antibacterial and anti-biofilm activities of three ruthenium complexes in different oxidation states with 2-pyridin-2-yl-1H-benzimidazole (L₁ = 2,2′-PyBIm): [(η⁶-p-cymene)Ru^IIClL₁]PF₆ (Ru(II) complex), mer-[Ru^IIICl₃(CH₃CN)L₁]·L₁·3H₂O (Ru(III) complex), (H₂L₁)₂[Ru^IIICl₄(CH₃CN)₂]₂[Ru^IVCl₄(CH₃CN)₂]·2Cl·6H₂O (Ru(III/IV) complex). The biological activity of the compounds was screened against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa strains. The results indicated that the anti-biofilm activity of the Ru complexes at concentration of 1 mM was better than that of the ligand alone against the P. aeruginosa PAO1. It means that ligand, in combination with ruthenium ion, shows a synergistic effect. The effect of the Ru complexes on cell surface properties was determined by the contact angle and zeta potential values. The electric and physical properties of the microbial surface are useful tools for the examined aggregation phenomenon and disruption of the adhesion. Considering that intermolecular interactions are important and largely define the functions of compounds, we examined interactions in the crystals of the Ru complexes using the Hirshfeld surface analysis.     

Use of HPLC in the identification of cis and trans-diaquabis(2,2′-bipyridine)ruthenium(II) complexes: crystal structure of cis-[Ru(H2O)2(bpy)2](PF6)2

[Ru(H₂O)₂(bpy)₂](PF₆)₂ complex was obtained by reacting HPF₆ in a [Ru(CO₃)(bpy)₂] aqueous solution. The complex can exist as cis and trans isomers and usually has been used in the preparation of several ruthenium–bipyridine species. Despite the possibility to have contamination of a specie in another, there is no analytical control involving the characterization of both complexes. Based on this we have proposed the use of high-performance liquid chromatography (HPLC) as an analytical technique to control the purity of cis and trans isomers. The separation was performed using a CLC-ODS column. The cis isomer eluted at 9.4 min while trans isomer eluted at 4.3 min. In aqueous solution the trans and cis isomer configurations were confirmed by NMR spectra (¹H). The attribution of cis isomer was also made based on the X-ray crystal structure (monoclinic, P2_1/c, a=12.320(2), b=13.852(2), c=34.220(3) Å, β=91.89(1)°, Z=8) which is reported. The six-coordinated ruthenium atom is chelated by two bipyridines and two molecules of H₂O.