Supramolecular self-assembly of two Cu(II) complexes with 1,2,4-triazole derivatives: syntheses,crystal structures and magnetic properties

Two two-dimensional coordination complexes, {[Cu₄(BTM)₆(OPA)₄] · 4DMF · 3H₂O} _n (1) and {[Cu(BDTM)(OH)](ClO₄) · 2H₂O} _n (2) (BTM = bis(1,2,4-triazol-1-yl)methane, BDTM = bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane, OPA²⁻ = ortho-phthalic dianion, DMF = N,N-dimethylformamide), were synthesized and structurally characterized. Each Cu(II) ion locates in a distorted square pyramidal geometry in 1, in which OPA²⁻ ligands bridge Cu²⁺ ions along a axis to form a magnetic transmission chain and BTM ligands act as flexible spacers to construct the two-dimensional layer structure. In 2, each Cu²⁺ ion adopts tetra-coordination geometry to two hydroxyl groups and two triazolyl nitrogen atoms from two different BDTM ligands. Two hydroxyl groups bridge two Cu²⁺ ions to form a rhombic diamond, and four BDTM ligands connect four diamonds to form a 36-membered macrocyclic structure with large channels along a axis. Magnetic properties revealed that both OPA²⁻ and OH⁻ mediate anti-ferromagnetic interactions between Cu²⁺ ions with J = − 0.06(3) and −301.9(2) cm⁻¹ for 1 and 2, respectively. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Coordination polymers with adamantanediacetate bridges: syntheses, structures, and magnetic properties

Abstract  Two new coordination polymers, [CoL(bpp)] _n (1) and [MnL(bipy)] _n ·0.25nH₂L·0.5nH₂O (2) (H₂L = 1,3-adamantanediacetic acid, bpp = 1,3-bis(4-pyridyl)propane, bipy = 4,4′-bipyridine), were synthesized and characterized by single crystal X-ray diffraction, IR spectroscopy, and thermal analysis. Complex 1 is an one-dimensional (1D) chain structure of Co(II) bridged by L²⁻ as well as bpp. Complex 2 consists of a two-dimensional (2D) (3,6)-connected topology layer structure. Variable temperature magnetic susceptibility measurements in the range of 2–300 K reveal the existence of weak antiferromagnetic interactions in two complexes with J = −1.74 cm⁻¹, g = 2.26 for 1 and J = −0.10 cm⁻¹, g = 1.67 for 2. Index abstract  Two mental-organic frameworks, namely [CoL(bpp)] _n (1) and [MnL(bipy)] _n ·0.25nH₂L·0.5nH₂O (2) (H₂L = 1,3-adamantanediacetic acid, bpp = 1,3-bis(4-pyridyl)propane, bipy = 4,4′-bipyridine), have been synthesized based on 1,3-adamantanediacetic acid and N-donor coligand with metal ions Co(II) and Mn(II). The magnetic measurement of the two polymers reveals typical antiferromagnetism exchange. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Extraction and DFT study on the complexation of the cesium cation with a hexaarylbenzene-based receptor

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Cs⁺(aq) + A⁻(aq) + 1(nb) ⇆ 1·Cs⁺(nb) + A⁻ (nb) taking part in the two-phase water–nitrobenzene system (A⁻ = picrate, 1 = hexaarylbenzene-based receptor; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K _ex (1·Cs⁺, A⁻) = 2.8 ± 0.1. Further, the stability constant of the hexaarylbenzene-based receptor·Cs⁺ complex (abbrev. 1·Cs⁺) in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β _nb (1·Cs⁺) = 4.7 ± 0.1. By using quantum mechanical DFT calculations, the most probable structure of the 1·Cs⁺ complex species was solved. In this complex having C ₃ symmetry, the cation Cs⁺ synergistically interacts with the polar ethereal oxygen fence and with the central hydrophobic benzene bottom via cation–π interaction. Finally, the calculated binding energy of the resulting complex 1·Cs⁺ is −220.0 kJ/mol, confirming relatively high stability of the considered cationic complex species.     

Theoretical studies on anionic clusters of sulfate anions and carbon dioxide, SO 4?1/?2 (CO2)n, n?=?1?4

Geometry optimizations were performed on monoanionic and dianionic clusters of sulfate anions with carbon dioxide, SO₄^−1/−2(CO₂) _n , for n = 1–4, using the B3PW91 density functional method with the 6-311 + G(3df) basis set. Limited calculations were carried out with the CCSD(T) and MP2 methods. Binding energies, as well as adiabatic and vertical electron detachment energies, were calculated. No covalent bonding is seen for monoanionic clusters, with O₃SO–CO₂ bond distances between 2.8 and 3.0 ?. Dianionic clusters show covalent bonding of type [O₃S–O–CO₂]⁻², [O₃S–O–C(O)O–CO₂]⁻², and [O₂C–O–S(O₂)–O–CO₂]⁻², where one or two oxygens of SO₄⁻² are shared with CO₂. Starting with n = 2, the dianionic clusters become adiabatically more stable than the corresponding monoanionic ones. Comparison with SO₄^−1/−2(SO₂) _n and CO₃^−1/−2(SO₂) _n clusters, the binding energies are smaller for the present SO₄^−1/−2(CO₂) _n systems, while stabilization of the dianion occurs at n = 2 for both SO₄⁻²(CO₂) _n and SO₄⁻²(SO₂) _n , but only at n = 3 for CO₃⁻²(SO₂) _n .     

Synthesis, Crystal Structure, Photophysical Properties, and DFT Calculations of a Bis(tetrathia-calix[4]arene) Tetracadmium Complex

Abstract  

Thiacalix[4]arenes are a unique family of polydentate ligands that offer a combination of four soft sulfur atoms together with four hard phenol oxygen atoms for binding to metal ions. In this study, the tetranuclear cadmium (II) complex Cd₄^II(tca)₂·1.5CH₂Cl₂ (tca⁴⁻ = tetra-anionic p-tert-butylthiacalix[4]arene) (1) was synthesized by reaction of a deprotonated p-tert-butylthiacalix[4]arene and various Cd^II salts. The structure of 1 was established by single crystal X-ray diffraction analysis. The neutral complex 1 contains a square arrangement of four cadmium (II) ions sandwiched between two tca⁴⁻ ligands that have a ‘cone’ conformation similar to that of the free ligand. The absorption and emission properties of the free ligand H₄tca and complex 1 have been recorded and explained by DFT calculations of the molecular orbitals and electronic transitions between them.     

Thiolate-bridged Trinuclear Heterobimetallic Complexes [Cd(μ-SPh-4-Me)4{M(PPh3)2}2] (M?=?Cu, Ag) and [Sn(μ-SPh)6(AgPPh3)2]

Abstract  

Reaction of the [Me₄N]₂[Cd(SPh-4-Me)₄] with two equivalents of [M(PPh₃)₂NO₃] afforded the neutral linear trinuclear complexes [Cd(μ-SPh-4-Me)₄{M(PPh₃)₂}₂] (M = Cu 1, Ag 2) in which two [M(PPh₃)₂]⁺ fragments chelate with the opposite edges of a tetrahedral [Cd(SPh-4-Me)₄]²⁻ moiety via the sulfur atoms of the Me-4-PhS⁻ species. Treatment of [Sn(SPh)₄] with two equivalents of [Ag(PPh₃)₂NO₃] gave the neutral linear trinuclear complex [Sn(μ-SPh)₆(AgPPh₃)₂] (3) that is composed of a central distorted SnS₆ octahedron sharing two opposite planes with two slightly distorted AgS₃P tetrahedrons. Complexes 2 and 3 are air and optically stable. Their nonlinear optical absorption and refraction were investigated under the same conditions. The nonlinear optical absorption and refraction of complex 2 were determined to be α ₂ = 3.11 × 10⁻¹¹ m/W and n ₂ = 4.15 × 10⁻¹² esu, respectively. The nonlinear optical absorption and refraction of complex 3 were determined to be α ₂ = 8.36 × 10⁻¹¹ m/W and n ₂ = 1.47 × 10⁻¹¹ esu, respectively.     

Thermodynamic and NMR studies of mixed-ligand complex formation of cadmium ethylenediaminetetraacetate with diamines in an aqueous solution

The mixed-ligand complex formation in the systems Cd2 + Edta4–(CH₂) _n (NH₂)₂, n = 2 (En), 6 (L) has been NMR and calorimetrically studied in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO₃). The thermodynamic parameters of formation of the CdEdtaL²⁻, CdEdtaHL⁻, (CdEdta)₂L⁴⁻, and (CdEdta)₂En⁴⁻ complexes have been determined. The most probable coordination mode for the complexone and the diamine ligand in the mixed-ligand complexes was discussed.     

Steric distortion of planar NiP<Subscript>2</Subscript>N<Subscript>2</Subscript> chromophores: a spectral,cyclic voltammetric and single crystal X-ray structural study

The complexes trans-[Ni(4-MP)₂(NCS)₂]·MeCN (1) and trans-[Ni(3-MP)₂(NCS)₂] (2) (4-MP = tri(4-methylphenyl)phosphine, 3-MP = tri(3-methylphenyl)phosphine) were prepared and characterized by IR, UV–visible, NMR spectra, CV, TGA and single crystal X-ray crystallography. Both the complexes have planar geometry and are diamagnetic. The Ni–P distances in both complexes are relatively short as a result of strong back donation from nickel to phosphorus. The phenyl rings in the 3-MP analogue (2) show increased pitching with reference to the plane formed by the ipso carbons due to increased steric effects. For complex (2), the N–Ni–N and P–Ni–P angles are significantly lower than the almost linear N–Ni–N and N–Ni–P angles observed for both complex (1) and trans-[Ni(PPh₃)₂(NCS)₂]. This observation indicates that the 3-methylphosphine ligand forces complex (2) to distort towards a tetrahedral geometry. IR spectra of both complexes show strong bands around 2,090 cm⁻¹ due to N-coordinated thiocyanate, while the electronic spectra contain d–d transitions around 452 nm. Cyclic voltammograms show that the irreversible one-electron reduction potentials increase in the following order: trans- [Ni(PPh₃)₂(NCS)₂] < trans- [Ni(3-MP)₂(NCS)₂] < trans-[Ni(4-MP)₂(NCS)₂], revealing the electron releasing effect of the methyl groups. The planar complexes exhibit interallogony in coordinating solvents.     

DNA-binding and photocleavage, cytotoxicity, apoptosis and antioxidant activity studies of ruthenium(II) complexes

Two ruthenium(II) polypyridyl complexes, namely [Ru(phen)₂(DMDPPZ)](ClO₄)₂ 1 (phen = 1,10-phenanthroline, DMDPPZ = 3,6-dimethyldipyrido[3,2-a:2′,3′-c]phenazine) and [Ru(dmp)₂(DMDPPZ)](ClO₄)₂ 2 (dmp = 2,9-dimethyl-1,10-phenanthroline), have been synthesized and characterized. The DNA-binding properties of the complexes were investigated by spectrophotometric methods, viscosity measurements, and photoactivated cleavage studies. The DNA-binding constants for complexes 1 and 2 have been determined as 8.78 (±0.94) × 10⁵ M⁻¹ (s = 3.02) and 1.26 (±0.35) × 10⁵ M⁻¹ (s = 1.69), respectively. The results suggest that these complexes bind to calf thymus DNA through intercalation. When irradiated at 365 nm, the complexes promote the photocleavage of pBR322 DNA, and complex 1 cleaves DNA more effectively than complex 2 under comparable experimental conditions. The cytotoxicities of complexes 1 and 2 have been evaluated by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) method. Complex 2 shows higher anticancer potency than complex 1 against four tumor cell lines. The apoptosis-inducing activity was assessed by acridine orange/ethidium bromide staining assay, and the antioxidant activities of these complexes against hydroxyl radical were also explored.     

Synthesis, structure, and properties of a binuclear Fe(III) complex with N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine

Mannich reaction of 2-Amino propanol, 2-tert-butyl-4-methylphenol, and formaldehyde in the ratio of 1:2:2 provides a new compound, N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L), which has been characterized by X-ray crystallography and elemental analysis. In the presence of Et₃N, the reaction of H₃L and FeCl₃·6H₂O gives a dinuclear Fe(III) complex [Fe₂L₂] 1, which has been characterized by X-ray crystallography, magnetic measurement, and cyclic voltammetry. The value of μ_eff at room temperature (5.97 μ_B) is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ZS(S + 1)]^1/2], indicating there are strong coupling interactions between Fe³⁺ ions. The magnetic behavior of 1 denotes the occurrence of intramolecular antiferromagnetic interactions (J = −13.35 cm⁻¹ ). CV of 1 reveals two reversible waves at 0.433 and 1.227 V versus AgCl/Ag, which can be ascribed to the successive redox coupling of Fe^IIFe^II/Fe^IIIFe^II and Fe^IIIFe^II/Fe^IIIFe^III, respectively.     

Structure and properties of μ<Subscript>2</Subscript>-<Emphasis Type="Italic">S</Emphasis>-[bis(benzenethiolato)tetranitrosyldiiron] in solution

Dinuclear iron tetranitrosyl complex with the composition [Fe₂(SPh)₂(NO)₄] (1) was synthesized and its single crystals and polycrystals were studied by X-ray diffraction, IR spectroscopy, and elemental analysis. The decomposition products of complex 1 were investigated by electrochemical method and mass spectrometry. The mass spectrum of a solution of complex 1 shows two groups of ions: the primary decomposition products of 1 in solution (the complex ions [Fe(SPh)(NO)₂(NO₂)]⁻, [Fe(SPh)₂(NO)]⁻, and [Fe(SPh)₂(NO)₂]⁻) and a series of the ions [FeO₂ + n(NO)]⁻ and [FeO₃ + n(NO)]⁻ (n = 0–4), which are formed in secondary reactions. The structures of the complexes, which were formed through the Fe-NO bond dissociation and the replacement of the NO ligand by aqua and oxygen ligands in complex 1, and the structure of the complex [FeO₃]⁻ were studied by quantum chemical modeling.     

A bimetallic cyano-bridged complex based on nickel(II) and pentacyanidonitrosylferrate(II) precursors: characterization, crystal structure, and magnetic properties

A heterobimetallic cyano-bridged 1D coordination polymer of the composition [Ni(baepn)(μ-NC)Fe(CN)₃(NO)(μ-CN)]_n·3H₂O has been synthesized by the reaction of nickel(II) nitrate hexahydrate, baepn (baepn = N, N′-bis(2-aminoethyl)-1,3-propanediamine), and sodium nitroprusside dihydrate in a methanol–water mixture. The complex was characterized by physicochemical and spectroscopic methods. The crystal structure was established by single-crystal X-ray diffraction analysis. It reveals cyano-bridged heterometallic chains consisting of alternating arrays of Ni(II) and Fe(II) atoms, both being embedded in distorted octahedral environments. Low-temperature susceptibility measurements show the presence of weak antiferromagnetic exchange interactions between paramagnetic Ni(II) centers (J = −0.46 cm⁻¹) through long diamagnetic [Fe(CN)₅(NO)]²⁻ bridges. Spin state of the iron atom was established by ⁵⁷Fe M?ssbauer spectroscopy.     

Synthesis,crystal structures,and magnetic properties of two manganese(II) coordination polymers bearing 1,1′-biphenyl-3,3′-dicarboxylate ligands

Two Mn(II) coordination polymers, namely [Mn(bpda)] _n (1) and [Mn(bpda)(bpy)_0.5] _n (2) (H₂bpda = 1,1′-biphenyl-3,3′-dicarboxylic acid and bpy = 4,4′-bipyridine), have been synthesized from H₂bpdc, bpy, and MnSO₄·2H₂O under hydrothermal conditions. The complexes were characterized by physicochemical and spectroscopic methods, as well as by X-ray crystallography. Compound 1 possesses a 3D structure consisting of carboxylate-bridged edge-sharing Mn–O–Mn double chains. Compound 2 features a 3D open structure with a dinuclear Mn(II) secondary building unit. Magnetic susceptibility measurements of compounds 1 and 2 exhibit antiferromagnetic interactions between the nearest Mn(II), with J = –11.3 cm⁻¹ and g = 2.12 for 1, and J = –13.5 cm⁻¹ and g = 2.12 for 2.     

Electrospray Ionization Based Methods for the Generation of Polynuclear Oxo- and Hydroxo Group 6 Anions in the Gas-Phase

Electrospray ionization (ESI) of the Lindqvist (n-Bu₄N)₂[M₆O₁₉] (M = Mo, W) polyoxometalates provides a straightforward entry for the generation of an assortment of oxo- and hydroxo anions in the gas-phase. In particular, the series of oxo dianions of general formula [(MO₃) _n O]²⁻ (n = 2–6; M = Mo, W), monoanions, namely [(MO₃) _n O]⁻ (n = 1, 2) and [(MO₃) _n ]⁻ (n = 1, 2), and the hydroxo [(MO₃) _n (OH)]⁻ (n = 1–6) species can be readily generated in the gas-phase upon varying the solvent composition as well as the ionisation conditions (typically the U_c cone voltage). Complementary tandem mass experiments (collision induced dissociation and ion–molecule reactions) are also used aimed to investigate the consecutive dissociation of these species and their intrinsic gas-phase reactivity towards methanol. Special emphasis is paid to some of the key factors of these group 6 anions related to the gas-phase activation of methanol, such as molecular composition, open vs closed shell electronic nature and cluster size.     

Experimental and theoretical study on the complexation of the cesium cation with dibenzo-30-crown-10

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Cs⁺ (aq) + A⁻ (aq) + 1(nb) \rightleftarrows \rightleftarrows 1·Cs⁺(nb) + A⁻(nb) taking place in the two-phase water–nitrobenzene system (A⁻ = picrate, 1 = dibenzo-30-crown-10; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K _ex (1·Cs⁺, A⁻) = 4.0 ± 0.1. Further, the stability constant of the 1·Cs⁺ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log β _nb (1·Cs⁺) = 5.9 ± 0.1. Finally, by using quantum–mechanical DFT calculations, the most probable structure of the resulting cationic complex species 1·Cs⁺ was derived.     

DNA-binding and nuclease activity of 1,10-phenanthroline-based thiocyanato,acetato, azido and benzoato bridged dinuclear copper(II) complexes

The mononuclear Cu(II) complex [Cu(phen)(H₂O)(NO₃)₂] (1), obtained by the reaction of 1,10-phenanthroline with Cu(NO₃)₂·3H₂O in methanol solution, reacts with anionic ligands SCN⁻, AcO⁻, N₃ ⁻ and PhCO₂ ⁻ in MeOH solution to form the stable binuclear complexes [Cu₂(H₂O)₂(phen)₂(μ-X)₂]₂ (NO₃)₂, where X = SCN⁻ (2), AcO⁻ (3), N₃ ⁻ (4) or PhCO₂ ⁻(5). The molecular structure of complex 3 was determined by single-crystal X-ray diffraction studies. These complexes were characterized by electronic, IR, ESR, magnetic moments and conductivity measurements. The electrochemical behaviour of the complexes was investigated by cyclic voltammetry. The interactions of these complexes with calf thymus DNA have been investigated using absorption spectrophotometry. Their DNA cleavage activity was studied on double-stranded pBR322 plasmid DNA using gel electrophoresis experiments in the absence and presence of H₂O₂ as oxidant.     

DNA-binding,antioxidant activity and in vitro cytotoxicity induced by ruthenium(II) complexes containing polypyridyl ligands

Two new ruthenium(II) polypyridyl complexes, [Ru(dmp)₂(maip)](ClO₄)₂ 1 (maip = 2-(3-aminophenyl)imizado[4,5-f][1,10]phenanthroline and [Ru(dmp)₂(paip)](ClO₄)₂ 2 (paip = 2-(4-aminophenyl)imidazo[4,5-f][1,10]phenanthroline, dmp = 2, 9-dimethyl-1,10-phenanthroline) have been synthesized and characterized. The DNA-binding behaviors of complexes 1 and 2 were studied by viscosity measurements, thermal denaturation, and absorption titration. The results show that the two complexes intercalate between the base pairs of DNA. The DNA-binding constants K _b for complexes 1 and 2 were determined to be 3.23 ± 0.16 × 10⁴ M⁻¹ (s = 0.97) and 4.34 ± 0.65 × 10⁴ M⁻¹ (s = 1.13). The cytotoxicity of these complexes has been evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. The IC₅₀ values are 35.70, 41.04, 55.25 and 37.50 for complex 1 and 37.02, 103.08, 130.07 and 37.80 for complex 2 against BEL-7402, C-6, HepG-2 and MCF-7 cell lines, respectively. The antioxidant activity against hydroxyl radical (OH•) was also investigated.     

Syntheses,crystal structures,and magnetic properties of three coordination polymers based on manganese(II) and 2,6-naphthalenedicarboxylate

Three novel coordination polymers, namely, [Mn(ndc)(bpy)] _n  · n(H₂O) (1), [Mn(ndc)(phen)] _n (2), and [Mn₃(ndc)₃(bpy)₂] _n (3) (H₂ndc = 2,6-naphthalenedicarboxylic acid, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline) have been hydrothermally synthesized and characterized by elemental analysis, IR, and single-crystal X-ray diffraction analysis. Complexes 1–3 exhibit three-dimensional metal-organic frameworks (MOFs); 1 and 2 are assemblies of the same secondary building units (SBUs), linear infinite chains {Mn(CO₂)₂} _n , forming one-dimensional channel, while complex 3 is constructed by trinuclear clusters {Mn₃(CO₂)₆} SBUs. Magnetic properties of complexes 1 and 3 are also discussed with respect to the bridging mode of the carboxylate groups.     

Cis-coordination of the chromate anions in helical Co/Ni block-type polymeric systems. Structural and spectroscopic characteristics of catena(μ-CrO4-O,O′)[Co(HIm)3H2O] and catena(μ-CrO4-O,O′)[Co0.43Ni0.57(HIm)3H2O]

Two polymeric complexes: catena(μ-CrO₄-O,O′)[Co(HIm)₃H₂O] (1) and catena(μ-CrO₄-O,O′)[Co_0.43Ni_0.57(HIm)₃H₂O] (2) (where HIm=imidazole) with a cis-bridging coordination mode of the CrO₄ ²⁻ anion have been synthesized and characterized by X-ray and spectroscopic methods. These crystals were isolated from nine systems of varying reagent molar ratios and three excluding anions: Cl⁻, NO₃ ⁻ and SO₄ ²⁻ exclusively as mer [M(HIm)₃O₃]-type isomers. The unit cell of these isostructural complexes (monoclinic crystal system P2₁ /n) contains two independent helixes, left- and right handed, stabilized by intrahelical and interhelical hydrogen bonding and π–π interaction between pairs of the imidazole rings from neighbouring helixes. The Raman spectra at 77 K of 1 and 2 deconvoluted into lorentzian components revealed the block-type polymeric structure of the complexes. Moreover, the solution studies at millimolar concentrations of 1 and 2 indicated their complete decomposition in water. Four K electronic spectral analysis of the crystals (band deconvolution into gaussian components) enhanced with the data obtained in the polarized light allowed for assignment of the bands to the respective d–d transition (D_4h symmetry). It was found that the metallic centres are independently absorbing species, which supports the suggestion of a block-type structure of the polymers. The respective crystal field parameters for Co and Ni were calculated.     

Synthesis,structure, and NO-donor activity of the paramagnetic complex [Fe<Subscript>2</Subscript>(SC<Subscript>3</Subscript>H<Subscript>5</Subscript>N<Subscript>2</Subscript>)<Subscript>2</Subscript>(NO)<Subscript>4</Subscript>] as a model of nitrosyl [2FE-2S] proteins

The neutral dinuclear iron nitrosyl complex [Fe₂(SC₃H₅N₂)₂(NO)₄] (1) of the “g = 2.03” family with a ligand analogous to natural mercaptohistidine was synthesized by the metathesis reaction of the thiosulfate ligands in the [Fe₂(S₂O₃)₂(NO)₄]²⁻ anion with imidazolidine-2-thiolate ligands. The electrochemical determination of nitrogen oxide in solution showed that compound 1 has a lower NO-donor ability compared to the iron complexes with 1-methylimidazole-2-thiol and imidazole-2-thiol synthesized earlier. Study of the magnetic properties of polycrystals of 1 demonstrated that the effective magnetic moment at room temperature is ca. 2.45 μ_B and corresponds to a molecule containing a pair of the noninteracting spins S = 1/2. This is evidence that each iron coordination unit in complex 1 contains one unpaired electron, and the iron atom is in the low-spin state. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 28–34, January, 2007.