Reactions of 2-(arylazo)aniline with iridium trichloride: Synthesis, characterization and structure of new cyclometallated complexes of iridium(III)

Reactions of 2-(arylazo)aniline, HL (H represents the dissociable protons upon orthometallation and HL is p-RC₆H₄NNC₆H₄-NH₂; RH for HL¹; CH₃ for HL² and Cl for HL³) with IrCl₃ in methanol afforded orthometallated complexes of composition (L)(HL)IrCl₂ (2) and (L)(MeOH)IrCl₂ (3), respectively. Complex (L)(MeOH)IrCl₂ (3) converted into (L)(CH₃CN)IrCl₂ (4) upon refluxing in acetonitrile. The X-ray structure of the complexes (L¹)(HL¹)IrCl₂ (2a) and (L³)(CH₃CN)IrCl₂ (4c) have been determined and characterized unequivocally. The anionic L⁻ binds the metal in tridentate (C, N, N) manner for all the complexes.     

Syntheses, characterization, and DFT investigation of new mononuclear acetonitrile- and chloro-ruthenium(II) terpyridine complexes

A series of mononuclear acetonitrile complexes of the type [Ru(CH₃CN)(L)(terpy)]²⁺ {L = phen (1), dpbpy (3), and bpm (5)}, and their reference complexes [RuCl(L)(terpy)]⁺ {L = phen (2), dpbpy (4), and dpphen (6)} were prepared and characterized by electrospray ionization mass spectrometry, UV-vis spectroscopy, and cyclic voltammograms (CV). Abbreviations of the ligands (Ls) are phen = 1,10-phenanthroline, dpbpy = 4,4′-diphenyl-2,2′-bipyridine, bpm = 2,2′-bipyrimidine, dpphen = 4,7-diphenyl-1,10-phenanthroline, bpy = 2,2′-bipyridine, and terpy = 2,2′:6′,2″-terpyridine. The X-ray structures of the two complexes 2 and 3 were newly obtained. The metal-to-ligand charge transfer (MLCT) bands in the visible region for 1, 3, and 5 in acetonitrile were blue shifted relative to those of the reference complexes [RuCl(L)(terpy)]⁺. CV for all the [Ru(CH₃CN)(L)(terpy)]²⁺ complexes showed the first oxidation wave at around 0.95 V, being more positive than those of [RuCl(L)(terpy)]⁺. The time-dependent-density-functional-theory approach (TDDFT) was used to interpret the absorption spectra of 1 and 2. Good agreement between computed and experimental absorption spectra was obtained. The DFT approach also revealed the orbital interactions between Ru(phen)(terpy) and CH₃CN or Cl⁻. It is demonstrated that the HOMO-LUMO energy gap of the acetonitrile ligand is larger than that of the Cl⁻ one.     

Dinuclear bis(terpyridine)ruthenium(II) complexes by amide coupling of ruthenium amino acids: Synthesis and properties

Two redox-asymmetric amide-bridged bis(terpyridine)ruthenium(II) complexes (3a, 3b) have been prepared by amide coupling of a carboxylic acid functionalized complex with an amine substituted complex and they were fully characterized by spectroscopic analyses. They emit at 692 and 750 nm at room temperature in fluid solution with quantum yields larger than 10⁻³ and ³MLCT lifetimes of 22 ns. Ru···Ru distances were estimated from DFT models as 17.7 and 13.4 Å for 3a and 3b, respectively. Cyclic voltammetry gives two oxidation potentials for the differently substituted ruthenium sites with splittings of 0.10 and 0.23 V for 3a and 3b, respectively. Oxidation of 3b with Ce^IV ions gives the corresponding mixed-valent Ru^II-Ru^III system which is valence-localized according to NIR spectroscopic and theoretical analyses.     

Synthesis, crystal structures and magnetic properties of the copper(II) complexes containing isophthalate anion as coligand

Two new dinuclear isophthalato-bridged copper(II) complexes [Cu₂(ntb)₂(μ-ipt)](ClO₄)₂·4CH₃OH·0.33H₂O (1), [Cu₂(bbma)₂(μ-ipt)(NO₃)(CH₃OH)]NO₃·CH₃OH (2) and one mononuclear complex [Cu(bbma)(ipt)(CH₃OH)_0.67(H₂O)_0.33]·2CH₃OH (3) containing tetradentate and tridentate poly-benzimidazole ligands were synthesized, where ntb is tris(2-benzimidazolylmethyl)amine, bbma is bis(benzimidazol-2-yl-methyl)amine and ipt is isophthalate dianion. All of the complexes were characterized by elemental analysis, IR spectra and X-ray crystallography. The structures of complexes 1 and 2 consist of μ-ipt bridging two Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry around the Cu(II) ions of both compounds has a distorted square pyramidal geometry. The Cu···Cu distances are 9.142 and 10.435 Å for 1 and 2, respectively. Complex 3 has a distorted square pyramidal geometry achieved by the three N-atoms of the bbma ligand, one isophthalate-oxygen atom and one oxygen atom from a coordinated methanol molecule. The magnetic susceptibility measurements at variable temperature over the 2-300 K range for complexes 1 and 2 are reported, with J values to be −0.013 and −0.32 cm⁻¹, respectively. The results show that the two complexes exhibit very weak antiferromagnetic interactions between the dinuclear copper(II) centers.     

Micellar effect on the photophysics of heteroleptic ruthenium(II)–phenanthrolinedisulfonato complexes

Luminescent heteroleptic ruthenium(II) complexes of type RuL_nX_3–n [L = 1,10‐phenanthroline (phen), X = 4,7 diphenyl phenanthroline disulfonate, (dpsphen) n = 0,1,2,3] were synthesized and their photophysical properties investigated in homogeneous and cationic (CTAB), anionic (SDS) and nonionic (Triton X‐100) micelles. The luminescent quantum yield and lifetime of the complexes were found to increase in the presence of micellar media and on the introduction of a disulfonate ligand into the coordination sphere. Both electrostatic and hydrophobic interactions play an important role in the micellar media. Thus, by changing the nature of the ligands and the medium, we were able to tune the photophysical properties of Ru(II) complexes. Copyright © 2015 John Wiley & Sons, Ltd.     

Manganese(II) complexes with croconate and 2-(2-pyridyl)imidazole ligands: Syntheses, X-ray structures and magnetic properties

The mixed-ligand complexes of manganese(II) of formula [Mn(pyim)₂(C₅O₅)] (1) and [Mn(pyim)(H₂O)(C₅O₅)]_n · 2.5nH₂O (2) [pyim = 2-(2-pyridyl)imidazole and  = croconate (dianion of 4,5-dihydroxy-4-cyclopentene-1,2,3-trione)] have been prepared and their structures determined by X-ray crystallographic methods. Compound 1 is a tris-chelated mononuclear complex where the manganese atom is six-coordinate: four nitrogen atoms from two pyim molecules and two oxygen atoms from a croconate group build a somewhat distorted octahedral surrounding around the metal atom. The resulting neutral mononuclear units are linked to each other through double bridges which are constituted by the imidazole N-H and the metal-coordinated croconate-oxygen atom, the metal-metal separation through this supramolecular pathway being 7.6856(11) Å. Compound 2 is a croconato-bridged manganese(II) uniform chain with an intrachain metal-metal distance of 7.5118(9) Å. A bidentate pyim group, a water molecule and four oxygen atoms from two bis-bidentate croconate ligands build an irregular seven-coordination polyhedron around each manganese atom in 2. The investigation of the magnetic properties of 2 in the temperature range 1.9-295 K has shown the occurrence of a weak antiferromagnetic interaction [J = −0.066 cm⁻¹ with the Hamiltonian defined as H = −J ∑_i S_i · S_i+1] through the bis-bidentate croconate. The ability of the bis-chelating croconate to mediante magnetic interactions between paramagnetic first-row transition metal ions is discussed and compared to that of the related oxalate ligand.     

Syntheses and electrochemical properties of ruthenium(II) complexes with 4,4-bipyrimidine and 4,4-bipyrimidinium ligands

The syntheses and electrochemical properties of novel ruthenium(II) polypyridyl complexes with 4,4^′-bipyrimidine, [Ru(trpy)(bpm)Cl](X) ([1](X; X=PF₆⁻, BF₄⁻)) and with a quaternized 4,4^′-bipyrimidinium ligand, [Ru(trpy)(Me₂bpm)Cl](BF₄)₃ ([2](BF₄)₃) (trpy=2,2^′:6^′,2″-terpyridine, bpm=4,4^′-bipyrimidine, Me₂bpm=1,1^′-dimethyl-4,4^′-bipyrimidinium) are presented. The bpm complex [1]⁺ was prepared by the reaction of Ru(trpy)Cl₃ with 4,4^′-bipyrimidine in EtOH/H₂O. The structural characterization of [1]⁺ revealed, that the bpm ligand coordinated to the ruthenium atom with the bidentate fashion. Diquaternization of the non-coordinating nitrogen atoms on bpm of [1]⁺ by (CH₃)₃OBF₄ in CH₃CN gave [2](BF₄)₃. The electrochemical and spectroelectrochemical properties of the complexes are described.     

Synthesis and structure of heteroleptic ytterbium (II) tetrahydroborate complexes

The synthesis and characterization of (Tp^tBu,Me)Yb(BH₄)(THF)_n (n = 0, 3; n = 1, 4) complexes are reported. The compounds represent rare examples of lanthanide (II) tetrahydroborate complexes. The X-ray crystal structure of complex 4 has been determined and it shows a monomeric, formally seven coordinate ytterbium center, bearing one κ³ bonded Tp^tBu,Me ligand, a tetrahydroborate ligand and a coordinated THF molecule. The tetrahydroborate ligand binds in a κ³ fashion, via three bridging hydrogen atoms. IR spectroscopy data are consistent with the solid-state structure and the corresponding BD₄ analog of 4 shows the expected IR isotope shifts. The ¹H NMR spectra of 3 and 4 shows one set of resonances each for the BH₄ and the pyrazolylborate ligands indicating dynamic solution behavior. For complex 3, although X-ray quality crystals could not be obtained, the IR and NMR data are consistent with its formulation as the solvent-free analog of complex 4 with κ³-bonded BH₄ ligand.     

DNA binding property, nuclease activity and cytotoxicity of Zn(II) complexes of terpyridine derivatives

Two zinc(II) terpyridine complexes Zn(atpy)₂(PF₆)₂ (1) (atpy = 4′-p-N9′-adeninylmethylphenyl-2,2′:6,2′′-terpyridine) and Zn(ttpy)₂(PF₆)₂ (2) (ttpy = 4′-p-tolyl-2,2′:6,2′′-terpyridine) have been synthesized and characterized by elemental analysis, ¹H NMR and electrospray mass spectroscopy. The structure of complex 2 was also determined by X-ray crystallography, which revealed a ZnN₆ coordination in an octahedral geometry with two terpyridine acting as equatorial ligands. The circular dichroism data showed that complex 1 exhibited an ICD signal at around 300 nm and induced more evident disturbances on DNA base stacking than complex 2, reflecting the impact of the adenine moiety on DNA binding modes. Complex 1 exhibited higher cleavage activity to supercoiled pUC 19 DNA than complex 2 under aerobic conditions, suggesting a promotional effect of adenine moiety in DNA nuclease ability. Interestingly, both complexes demonstrated potent in vitro cytotoxicity against a series human tumor cell lines such as human cervix carcinoma cell line (HeLa), human liver carcinoma cell line (HepG2), human galactophore carcinoma cell line (MCF-7) and human prostate carcinoma cell line (pc-3). The cytotoxicity is averagely 10 times more active than the anticancer drug cisplatin. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis and photophysical properties for fluorescent hexameric metallomacrocycles: Zinc(II)-mediated self-assembly of bis(terpyridine) ligands

Two types of hexameric metallomacrocycles, [Zn₆(1)₆(PF₆)₁₂] and [Zn₆(2)₆(PF₆)₁₂], where 1 is 1,3-bis(2,2′:6′,2″-terpyridine)-5-tert-butylbenzene and 2 is 1,3-bis(2,2′:6′,2”-terpyridinylethynyl)-5-tert-butylbenzene, were self-assembled by capitalizing on terpyridine-Zn(II)-terpyridine connectivity. Their structural compositions were established by ¹H and ¹³C NMR, UV-Vis, and mass spectrometry. Incorporation of an ethynyl group in the metallomacrocycle can play a role as an electron trapping site to enhance the molar extinction coefficiency and photocurrent generation.     

Synthesis and characterization of new ruthenium(II) complexes containing coupled di(2-pyridyl) and 1,3-dithiole units

Two new ruthenium (II) complexes containing coupled di(2-pyridyl) and 1,3-dithiole units, cis-[Ru(Medpydt)₂(NCS)₂] (2, Medpydt = dimethyl 2-(di(2-pyridyl)methylene)-1,3-dithiole-4,5-dicarboxylate) and cis-[Ru(H₂dpydt)₂(NCS)₂] (3, H₂dpydt = 2-(di(2-pyridyl)methylene)-1,3-dithiole-4,5-dicarboxylate), have been synthesized and characterized. The structure of complex 2 has been determined by X-ray crystallography. There exist intermolecular H-bonding interactions between carbomethoxy groups on neighboring pyridine rings giving rise to 2D H-bonded arrays. The metal-to-ligand charge-transfer (MLCT) absorptions were observed around 480 nm. Redox properties of ruthenium complexes have been investigated by cyclic voltammetry. Solar cells involving thin films of anatase TiO₂ impregnated with cis-[Ru(H₂dpydt)₂(NCS)₂] were prepared, and the photovoltaic performance was preliminarily investigated.     

Photochemical and photophysical properties of ruthenium(II) bis-bipyridine bis-nitrile complexes: Photolability

The electrochemical and photophysical properties of two bis-nitrilo ruthenium(II) complexes formulated as [Ru(bpy)₂(L)₂](PF₆)₂, where bpy is 2,2′-bipyridine and L is AN = CH₃CN and sn = NC-CH₂CH₂-CN, have been investigated. Electrochemical data are typical of Ru-bpy complexes with two reversible reduction peaks located near −1.3 and −1.6 V assigned to each bipyridine ligand and one Ru^II/Ru^III oxidation wave centered at approximately +1.5 V. The sn derivative is both IR and Raman active with its coordinated CN stretch appearing at 2277 cm⁻¹ and 2273 cm⁻¹, respectively. The UV/Vis absorption spectrum of the sn derivative is dominated by an intense (ε_max ∼ 58700 M⁻¹ cm⁻¹) absorption band at 287 nm assigned as a LC (π → π∗) transition. The peak observed at 418 nm (ε ∼ 10 400 M⁻¹ cm⁻¹) is an MLCT band while the one at 244 nm (ε ∼ 23 600 M⁻¹ cm⁻¹) is of LMLCT character. The AN derivative behaves similarly. Both complexes show low-temperature emission at around 537 nm with a lifetime near 10.0 μs. ¹H and ¹³C assignments are consistent with the formulation of the complexes. The complexes undergo photosubstitution of solvent with quantum efficiencies near one. Calculated and experimental results support replacement of the nitrile ligands by solvent. Based on DFT calculations, the electron density of the HOMO lies on the metal center, the bipyridine ligands and the nitrile ligands and electron density of the LUMO resides primarily on the bipyridine ligands. The electronic spectra obtained from TDDFT calculations closely match the experimental ones.     

Syntheses and crystal structures of three Mn(II) complexes with 2-hydroxynicotinate

Three new Mn(II) complexes [Mn(HnicO)₂(H₂O)₂] (1), [Mn₂(HnicO)₂SO₄(H₂O)₂]_n (2), and [NaMn(HnicO)₃]_n (3) (H₂nicO = 2-hydroxynicotinic acid) have been synthesized and determined by X-ray diffraction. For complex 1, the mononuclear units with two bidentate HnicO⁻ ions and two water molecules are assembled into a 3D architecture via hydrogen bonding and π-π interactions. For 2, Mn(II) ions are connected by μ₃-HnicO⁻ and bridging ligands, producing a 2D (6,3) coordination network. For 3, binuclear Na(I)-Mn(II) units with three carbonyl oxygen bridges are interlinked by carboxylate groups, resulting in a 3D 6-connected coordination network with distorted α-Po topology. The magnetic properties of 2 are discussed.     

Syntheses, crystal structures, spectroscopic, fluorescence and thermal properties of silver(I) 5,5-diethylbarbiturato complexes with some aminopyridines

Three new silver(I) complexes of 5,5-diethlybarbiturate (barb), [Ag(barb)(apy)]·H₂O (1), {[Ag(μ-ampy)][Ag(μ-barb)₂]}_n (2) and [Ag(barb)(dmamhpy)] (3) [apy = 2-aminopyridine, ampy = 2-aminomethylpyridine and dmamhpy = 2-(dimethylaminomethyl)-3-hydroxypyridine] have been synthesized and characterized by elemental analysis and FT-IR. Single crystal X-ray diffraction analyses showed that complexes 1 and 3 are mononuclear. In 1, the silver(I) ion is linearly coordinated by a barb anion and a ampy ligand, while a bidentate dmamhpy ligand together with an N-coordinated barb anion forms a trigonal coordination geometry around silver(I) in 3. Complex 2 is a one-dimensional coordination polymer in which silver(I) ions are bridged by ampy ligands, leading to a cationic chain . The [Ag(barb)₂]⁻ units contains two N-bonded barb ligands, bridging the silver centers in the cationic and anionic units via the carbonyl O atoms. Thus, complex 2 contains two-coordinated and four-coordinated silver ions. All complexes display hydrogen-bonded network structures and exhibit appreciable fluorescence at room temperature. Thermal analysis (TG-DTA) data are in agreement with the structures of the complexes.     

Selective recognition of homocysteine and cysteine based on new ruthenium(II) complexes

A series of the new ruthenium(II) complexes with different number of aldehyde groups have been synthesized and characterized for the simple and selective sensing of homocysteine (Hcy) and cysteine (Cys). The reaction of these ruthenium(II) complexes with Hcy and Cys afforded thiazinane or thiazolidine derivatives which resulted in the obvious changes in the UV-visible spectra and strong enhancement of the luminescence intensity of the system. The luminescence enhancement of [Ru(dmb)₂(L2)]²⁺ (dmb: 4,4′-dimethyl-2,2′-bipyridine) showed a good linearity in the concentration of 4.2-350 μM and 6-385 μM with the detection limits of 0.3 μM and 1 μM for Hcy and Cys, respectively. The absorption and emission bands from metal-to-ligand charge transfer transition in the visible region and the large Stokes shift of the ruthenium(II) complex chromophore made it suitable for biological applications.     

Interaction of Pt(II) and Pd(II) complexes of terpyridine with 1-methylazoles: A combined experimental and density functional study

The synthesis and characterization of several complexes of the composition [{M(terpy)}_n(L)](ClO₄)_m (M = Pt, Pd; L = 1-methylimidazole, 1-methyltetrazole, 1-methyltetrazolate; terpy = 2,2′:6′,2″-terpyridine; n = 1, 2; m = 1, 2, 3) is reported and their applicability in terms of a metal-mediated base pair investigated. Reaction of [M(terpy)(H₂O)]²⁺ with 1-methylimidazole leads to [M(terpy)(1-methylimidazole)](ClO₄)₂ (1: M = Pt; 2: M = Pd). The analogous reaction of [Pt(terpy)(H₂O)]²⁺ with 1-methyltetrazole leads to the organometallic compound [Pt(terpy)(1-methyltetrazolate)]ClO₄ (3) in which the aromatic tetrazole proton has been substituted by the platinum moiety. For both platinum(II) and palladium(II), doubly metalated complexes [{M(terpy)}₂(1-methyltetrazolate)](ClO₄)₃ (4: M = Pt; 5: M = Pd) can also be obtained depending on the reaction conditions. In the latter two compounds, the [M(terpy)]²⁺ moieties are coordinated via C5 and N4. X-ray crystal structures of 1, 2, and 3 are reported. In addition, DFT calculations have been carried out to determine the energy difference between fully planar [Pd(mterpy)(L)]²⁺ complexes Ip-IVp (mterpy = 4′-methyl-2,2′:6′,2″-terpyridine; L = 1-methylimidazole-N3 (I), 1-methyl-1,2,4-triazole-N4 (II), 1-methyltetrazole-N3 (III), or 3-methylpyridine-N1 (IV)) and the respective geometry-optimized structures Io-IVo. Whereas this energy difference is larger than 70 kJ mol⁻¹ for compounds I, II, and IV, it amounts to only 0.8 kJ mol⁻¹ for the tetrazole-containing complex III, which is stabilized by two intramolecular C-H?N hydrogen bonds. Of all complexes under investigation, only the terpyridine-metal ion-tetrazole system with N3-coordinated tetrazole appears to be suited for an application in terms of a metal-mediated base pair in a metal-modified oligonucleotide.     

Syntheses, structures and magnetic properties of three new ion-pair complexes containing transition metal bis(malconitriledithiolate) anion and radical cations

Three new ion-pair complexes (m-MPYNN)₂Ni(mnt)₂ (1), (p-MPYNN)₂Ni(mnt)₂ (2) and (p-MPYNN)₂Cu(mnt)₂ (3) (m- or p-MPYNNI = [3- or4- (4,4,5,5-tetramethyl-1-oxido-3-oxyl-4,5-dihydro-3H-imidazol-2′-yl)-1-methylpyridinium] iodide, mnt = maleonitriledithiolate) have been prepared and characterized by elemental analyses, IR, single crystal X-ray diffraction and magnetic susceptibility. In complex 1, the m-MPYNN cations form a centrosymmetric dimer, and the [Ni(mnt)₂]²⁻ anion lies on a center of inversion. Complexes 2 and 3 show layered packing, and the p-MPYNN cations lie between the layers of the anions. Magnetic susceptibility measurements in the temperature range 2-300 K show that the three complexes exhibit weak antiferromagnetic behaviors. The behavior of complex 1 was explained with the singlet-triplet model.     

Synthesis of novel mononuclear and dinuclear ruthenium(II) complexes with terpyridine and acetylacetonate ancillary ligands and cyanamide derivative ligands

Several new mononuclear and dinuclear ruthenium(II) complexes - incorporating 2,2′:6′,2″-terpyridine and acetylacetonate as ancillary ligands and phenylcyanamide derivative ligands - of the type [Ru(tpy)(acac)(L)] and [{Ru(tpy)(acac)}₂(μ-L′)] (where tpy = 2,2′:6′,2″-terpyridine, acac = acetylacetonate, L = hmbpcyd = 4-(3-hydroxy-3-methylbutynyl)phenylcyanamide anion (2) and epcyd = 4-ethynylphenylcyanamide anion (3) and L′ = bcpda = bis(4-cyanamidophenyl)diacetylene dianion (4) and bcpea = 9,10-bis(4-cyanamidophenylethynyl)anthracene dianion (5)) were synthesized in a stepwise manner starting from [Ru(tpy)(acac)(Ipcyd)] (1), where Ipcyd = 4-iodophenylcyanamide anion. Tetraphenylarsonium salts of the phenylcyanamide derivative ligands were also prepared. The four complexes have been characterized by UV-Vis, IR, ES-MS, electrochemistry and ¹H NMR. Mononuclear complexes 2 and 3 were further characterized by ¹³C NMR. The single crystal X-ray structure of 2 was determined, it crystallized with one molecule of water with empirical formula of C₃₂H₃₁N₅O₅Ru, in a monoclinic crystal system and space group of P2₁/n with a = 17.642(5) Å, b = 9.634(2) Å, c = 20.063(7) Å, β = 92.65(3)°, V = 3406(2) Å³ and Z = 4. The structure was refined to a final R factor of 0.040. The Ru(III/II) couple of 1-3 appeared around 0.34 V versus the saturated calomel electrode in dimethylformamide and at a slightly higher potential, around 0.36-0.37 V for 4 and 5. Spectroelectrochemical studies were also performed for 4 and 5, no intervalence transition was observed despite all attempts.     

Syntheses, structures and properties of copper(II) complexes containing N-(2-hydroxybenzyl)-amino amide ligands

Four copper(II) complexes containing the reduced Schiff base ligands, namely, N-(2-hydroxybenzyl)-glycinamide (Hsglym) and N-(2-hydroxybenzyl)-l-alaninamide (Hsalam) have been synthesized and characterized. The crystal structures of [Cu₂(sglym)₂Cl₂] (1), [Cu₂(salam)₂(NO₃)₂] · H₂O (3), [Cu₂(salam)₂(NO₃)(H₂O)](NO₃) · 1.5H₂O (4), [Cu₂(salam)₂](ClO₄)₂ · 2H₂O (5) show that the Cu(II) atoms are bridged by two phenolato oxygen atoms in the dimers. The sglym ligand bonded to Cu(II) in facial manner while salam ligand prefers to bind to Cu(II) in meridonal geometry. Variable temperature magnetic studies of 3 showed it is antiferromagnetic. These Cu(II) complexes and [Cu₂(sglym)₂(NO₃)₂] (2), exhibit very small catecholase activity as compared to the corresponding complexes containing acid functional groups.     

Syntheses and crystal structures of mononuclear and dinuclear (pentamethylcyclopentadienyl)iridium(III) complexes containing 2-mercaptobenzimidazole

A reaction of [Cp*IrCl₂]₂ {Cp* = η⁵-C₅(CH₃)₅} and 2-mercaptobenzimidazole (H₂bimt) in methanol in a 1:2 molar ratio gave a yellow complex of [Cp*IrCl₂(H₂bimt)]·CH₃OH (1). In compound 1 the H₂bimt acts as a monodentately S-donating (κS) ligand. A similar reaction of [Cp*IrCl₂]₂ and H₂bimt in the presence of NaOCH₃ (molar ratio of 1:2:2) gave an orange product (2) on addition of excess amount of NH₄PF₆. Compound 2 was composed of an unsymmetrical dinuclear complex cation, [(Cp*IrCl)₂(μ-Hbimt)(μ-H₂bimt)]⁺, a PF₆⁻ anion, and water molecules of crystallization. In the complex cation, H₂bimt bridges two Ir^III centers by S atom in the μ-κS:κS mode, while the monodeprotonated Hbimt⁻ ligand bridges via S and N atoms in the μ-κS:κN¹ mode.