Integrated gold-disk microelectrode modified with iron(II)-phthalocyanine for nitric oxide detection in macrophages

An integrated gold-disk microelectrode (IGME) was fabricated and modified with Fe(II)-phthalocyanine (Fe(II)-PC) for NO detection in biological media. Microanalysis of NO using square wave anodic stripping voltammetry (SWASV) in 0.01 M HClO₄ was optimal at the initial potential of 0.1 V, frequency of 100 Hz, pulse amplitude of 25 mV, and a scan rate of 200 mV/s. When the electrode was modified with Fe(II)-phthalocyanines, the anodic peak current and sensitivity of NO were remarkably increased due to the catalytic oxidation of NO. The calibration curve had good linearity in the range from 3.6×10⁻⁵ to 7.2×10⁻⁷ M, and the detection limit was (5.7±1.2)×10⁻⁷ M. Fe(II)-phthalocyanine modified gold-disk microelectrode coated with Nafion was applied to determination of NO released from macrophage cell.     

The valence structure analysis for dirhodium(II) tetracarboxylato complexes with nitric oxide as axial ligand

Density functional theory has been used to study the trans-influence of Rh–Rh and Rh–L bonds in dirhodium(II) tetracarboxylates with axial ligands L=H₂O, pyridine, CO, triphenylphosphine, NO and NO₂. The absence of the chemical bond between metal atoms in Rh₂(μ-O₂CR)₄(NO)₂ complexes and the formation of two covalent Rh–NO bonds explain the very long Rh–Rh and very short Rh–N distances in these compounds.     

The spin-states and spin-transitions of mononuclear iron(II) complexes of nitrogen-donor ligands

A survey of mononuclear iron(II) complexes with heterocyclic N-donor ligation is presented. A brief introduction to spin-crossover chemistry and low-temperature spin-trapping is provided, since many of these compounds undergo thermal spin-transitions upon cooling or heating. These are highlighted, and the structural changes underlying spin-crossover are discussed where this is known. Materials showing spin-trapping behaviour following thermal quenching or irradiation at very low temperatures are also described.     

Interaction of nitric oxide with tetrathiolato iron(II) complexes: relevance to the reaction pathways of iron nitrosyls in sulfur-rich biological coordination environments

The mechanism of formation of dinitrosyl iron complexes (DNICs) coordinated by cysteine residues at iron-sulfur protein sites has received little attention in the chemical literature. As a logical first step toward elucidating this mechanism and characterizing new iron-nitrosyl intermediates, we investigated the interaction of NO (g) and NO+ with iron-sulfur complexes chosen to mimic sulfur-rich iron sites in biology. The reaction of NO (g) with [Fe(StBu)4]2- cleanly affords the mononitrosyl complex, [Fe(StBu)3(NO)]- (1), a previously unknown species evoked in this chemistry. Reaction of [Fe(StBu)4]2- with NO derivatives, such as NO+, yields the corresponding dinitrosyl S-bridged Roussin red ester [Fe2(mu-StBu)2(NO)4] (2). The nitrosyl complexes 1 and 2 can chemically convert to the DNIC, [Fe(StBu)2(NO)2]- (3). The results should aid in the spectroscopic identification and elucidation of reaction pathways for the nitrosylation of iron in biologically related sulfur-rich coordination environments.     

Mesogenic and magnetic behavior in cobalt(II) and iron(II) compounds with long alkyl chains

Abstract  Metal complexes with long alkyl chains [Co(C16-terpy)₃](BF₄)₂ (1), [Fe(C16-terpy)₂](BF₄)₂ (2), [Co(C16-terpy)₂](BPh₄)₂ (3), [Co(C14-terpy)₂](BF₄)₂ (4), and [Fe(C12C10C5-terpy)₂](BF₄)₂ (5) were synthesized and their physical properties characterized, where C16-terpy, C14-terpy, and C12C10C5-terpy are 4′-hexadecyloxy-2,2′:6′,2′′-terpyridine, 4′-tetradecyloxy-2,2′:6′,2′′-terpyridine, and 4′-5′′′-decyl-1′′′-heptadecyloxy-2,2′:6′,2″-terpyridine, respectively. Complexes 1, 2, and 5 exhibited liquid–crystal properties in the temperature ranges of 371–528 K and 466–556 K, and 88–523 K, respectively. Variable-temperature magnetic susceptibility measurements revealed that the Co(II) complexes 1 and 4 exhibited unique spin transitions (T _1/2↓ = 217 K and T _1/2↑ = 260 K for 1 and T _1/2↓ = 250 K and T _1/2↑ = 307 K for 4), so-called ‘reverse spin transition,’ induced by structural phase transitions. Complex 3 exhibited gradual spin-crossover behavior (T _1/2 = 160 K.), and complex 5 exhibited spin transitions (T _1/2↑ = 288 K and T _1/2↓ = 284 K) at the liquid crystal transition temperature. Compounds with multifunction, i.e., magnetic and liquid–crystal properties, are important in the development of molecular materials. Graphical Abstract  

Kinetics of nitric oxide reduction by carbon monoxide in the presence of cobalt(II) complexes

Kinetic studies of nitric oxide reduction by carbon monoxide in the presence of Co(II) complexes indicate that the reaction is first order with respect to catalyst, carbon monoxide, and nitric, oxide. Co(AC₂)(OH) ₂ ^– complexes have the highest catalytic activity. A reduction mechanism is proposed.

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Co(II). , , . Co(Ac₂)(OH) ₂ ^– . .

     

Reversible release of nitric oxide from an iron(II) nitrosyl complex containing a biomimetic S4N chelate. A facile release of nitric oxide

The release of NO by [Fe(NO)(Et₂NpyS₄)], where (Et₂NpyS₄)^2? = 2,6-bis(2-mercaptophenylthiomethyl)-4-substituted pyridine(2-), has been studied in the absence and presence of a trapping agent. The results show that [Fe(NO)(Et₂NpyS₄)] releases NO spontaneously in solution with a slow rate, k_-NO = 1.7 × 10^?4 s^?1 at 23 °C, in a reversible reaction. NO release becomes faster when the reaction intermediate [Fe(Et₂ NpyS₄)] was trapped by CO, thereby preventing the back reaction. The release of NO was studied as a function of CO concentration and temperature. The reported activation parameters, especially the positive activation entropy values for the release of NO, favor the operation of a dissociative interchange (I_d) mechanism. Thus, [Fe(NO)(Et₂NpyS₄)] can serve as a NO deliverer.     

Kinetics of the reaction of cobalt(II) phthalocyanine complexes with functionalized organosilicas

The kinetics of the reaction of cobalt(II) phthalocyanine complexes with functionalized aminoorganosilicas was studied. Comparison of the kinetic parameters of the reactions studied provided additional information on the reaction mechanism and structure of the supported metal complexes, permitting delineation between the diffusion and kinetic regions of the reaction.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 31, No. 5, pp. 303–307, September–October, 1995.     

Kinetics and thermodynamics of the reaction of deoxyhemerythrin with nitric oxide

Deoxyhemerythrin reacts with NO to form a 1:1 adduct shown spectrophotometrically. The kinetics of the formation have been studied directly by stopped-flow measurements at four different temperatures (0.0-23.6 degrees C). The kinetics of the dissociation have been studied, also by stopped-flow techniques, at five different temperatures (4.0-35.1 degrees C) using three different scavengers [Fe(II)(edta)2-, O2 and sperm whale deoxymyoglobin], which gave similar values. For the formation kf = (4.2 +/- 0.2) x 10(6) M-1 s-1, delta Hf not equal = 44.3 +/- 2.3 kJ mol-1, delta Sf not equal to = 30 +/- 8 J mol-1 K-1 and for the dissociation kd = 0.84 +/- 0.02 s-1, delta Hd not equal to 95.6 +/- 2.1 kJ mol-1 delta Sd not equal to = 74 +/- 7 J mol-1 K-1 (25 degrees C, I = 0.2 M and pH 7-8.1). From the kinetic data the thermodynamic data for the formation of HrNO were calculated: Kf = (5.0 +/- 0.3) x 10(6) M-1, delta H = -51.3 +/- 3.1 kJ mol-1 and delta S = -44 +/- 11 J mol-1 K-1 (25 degrees C). The kinetic data suggest that NO occupies the same iron(II) site in deoxyhemerythrin as oxygen does. The equilibrium constant for the formation of Fe(II)(edta)(NO)2- has been redetermined: K1 = (1.45 +/- 0.07) x 10(7) M-1, delta H = -77.5 +/- 1.5 kJ and mol-1 and delta S = -123.5 J mol-1 K-1 (25 degrees C).     

Electronic structure of dinuclear iron nitrosyl complexes with different ligands at two iron centers

The electronic structures of three dinuclear iron complexes were determined with the DFT method. The complexes contain a {Fe(NO)₂}⁹ unit and thiolate, nitrosyl, carbonyl and amine ligands at the second iron atom. The two iron atoms are bridged by thiolate ligands. In the lowest energy states of these complexes, the iron atoms possess spin S = 1, 3/2 or 5/2, depending on the coordinated ligands and their mutual arrangement. Nitrosyl is coordinated as NO⁻ antiferromagnetically coupled to iron, and the two iron units are antiferromagnetically coupled to each other.     

Synthesis and characterization of two binuclear iron(III) complexes of aminoethanol derivatives of aminophenol as models for non-heme iron enzymes active sites

Two aminoethanol derivatives of aminophenol ligands were synthesized and characterized by IR and ¹H NMR spectroscopies. The binuclear iron(III) complexes of these ligands have been prepared and characterized by IR, ¹H NMR and UV-Vis spectroscopic techniques, cyclic voltammetry, single crystal X-ray diffraction and magnetic susceptibility studies. X-ray analysis revealed binuclear complexes, Fe₂(L₂), in which Fe(III) centers are surrounded by two phenolate and hydroxyl oxygen atoms, and amine nitrogens of the ligands. The metal active sites of both complexes are held together by the two above mentioned hydroxyl bridges. Variable temperature magnetic susceptibility indicates antiferromagnetic coupling between the iron centers of both complexes. This exchange coupling is stronger for Fe₂(L^ae)₂, such that it shows a room temperature strong coupling between the two iron centers. The investigated complexes undergo irreversible electrochemical oxidation and reduction.     

Spin Transition of 1D, 2D and 3D Iron(II) Complex Polymers The Tug-of-War between Elastic Interaction and a Shock-Absorber Effect

Summary.  The structures of linear chain Fe(II) spin-crossover compounds of α,β- and α,ω-bis (tetrazol-1-yl)alkane type ligands are described in relation to their magnetic properties. The first threefold interlocked 3-D catenane Fe(II) spin-transition system, [μ-tris(1,4-bis(tetrazol-1-yl)butane-N1,N1′) iron(II)] bis(perchlorate), will be discussed. An analysis is made among the structures and the cooperativity of the spin-crossover behaviour of polynuclear Fe(II) spin-transition materials. Corresponding author. E-mail: koning@iacgu7.chemie.uni-mainz.de Received April 8, 2002; accepted April 18, 2002     

Nature of the intermediate product of the reaction of the pentacyanocobaltate(II) ion with nitric oxide

The reaction of the pentacyanocobaltate(II) ion with nitric oxide in aqueous solution was studied. Infrared spectroscopy and mass spectrometry with bombardment by fast atoms showed that the intermediate product formed in this reaction is a binuclear complex of cobalt containing bridge NO^– groups.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 2, pp. 176–180, March–April, 1992.     

Solid complexes of iron(II) and iron(III) with rutin

Solid complex compounds of Fe(II) and Fe(III) ions with rutin were obtained. On the basis of the elementary analysis and thermogravimetric investigation, the following composition of the compounds was determined: (1) FeOH(C₂₇H₂₉O₁₆)·5H₂O, (2) Fe₂OH(C₂₇H₂₇O₁₆)·9H₂O, (3) Fe(OH)₂(C₂₇H₂₉O₁₆)·8H₂O, (4) [Fe₆(OH)₂(4H₂O)(C₁₅H₇O₁₂)SO₄]·10H₂O. The coordination site in a rutin molecule was established on the basis of spectroscopic data (UV–Vis and IR). It was supposed that rutin was bound to the iron ions via 4C=O and 5C—oxygen in the case of (1) and (3). Groups 5C–OH and 4C=O as well as 3′C–OH and 4′C–OH of the ligand participate in binding metals ions in the case of (2). At an excess of iron(III) ions with regard to rutin under the synthesis conditions of (4), a side reaction of ligand oxidation occurs. In this compound, the ligands’ role plays a quinone which arose after rutin oxidation and the substitution of Fe(II) and Fe(III) ions takes place in 4C=O, 5C–OH as well as 4′C–OH, 3′C–OH ligands groups. The magnetic measurements indicated that (1) and (3) are high-spin complexes.     

Gaseous iron(II) and iron(III) complexes with BINOLate ligands

Electrospray ionization (ESI) of dilute solutions of 1,1'-bi-2-naphthol (BINOL) and iron(II) or iron(III) sulfate in methanol/water allows the generation of monocationic complexes of iron and deprotonated BINOL ligands with additional methanol molecules in the coordination sphere, and the types of complexes formed can be controlled by the valence of the iron precursors used in ESI. Thus, iron(II) sulfate leads to [(BINOLate)Fe(CH3OH)n]+ complexes (n=0-3), whereas usage of iron(III) sulfate allows the generation of [(BINOLdiate)-Fe(CH3OH)n]+ cations (n=0-2); here, BINOLate and BINOLdiate stand for singly and doubly deprotonated BINOL, respectively. Upon collision-induced dissociation, the mass-selected ions with n>0 first lose the methanol ligands and then undergo characteristic fragmentations. Bare [(BINOLdiate)Fe]+, a formal iron(III) species, undergoes decarbonylation, which is known as a typical fragmentation of ionized phenols and phenolates either as free species or as the corresponding metal complexes. The bare [(BINOLate)Fe]+ cation, on the other hand, preferentially loses neutral FeOH to afford an organic C20H12O+* cation radical, which most likely corresponds to ionized 1,1'-dinaphthofurane.     

Comparative IR study of nitric oxide reactions with sublimed layers of iron(II)- and ruthenium(II)-meso-tetraphenylporphyrinates

The interactions of nitric oxide gas with thin layers of Fe(II)(TPP) and Ru(II)(TPP), obtained by sublimation onto low-temperature substrate (77 K), has been investigated by means of IR spectroscopy (TPP = meso-tetraphenylporphyrinate). Only simple addition of NO to form Fe(TPP)(NO) is observed for the iron-porphyrin Fe(II)(TPP), while, in contrast, Ru(II)(TPP) promotes NO disproportionation to form the nitrosyl-nitrito complex Ru(TPP)(NO)(ONO) and N(2)O. Thin layers of Fe(TPP)(NO) are inert to further reaction with excess NO; however, the nitrosyl-nitro complex Fe(TPP)(NO)(NO(2)) is readily formed when traces of dioxygen are added to the NO atmosphere. When the NO(2) concentrations in the NO/NO(2) mixture are relatively high, the nitrato complex Fe(TPP)(NO(3)) is also formed. Spectral data are given indicating that moderate shifts in the nitrosyl stretching frequency of Fe(TPP)(NO) are due to crystal packing effects, rather than to the H-bonding of coordinated NO with protic contaminants suggested in an earlier publication. Removal of NO by exhaustive evacuation from layers containing Fe(TPP)(NO)(NO(2)) leads to formation of Fe(TPP)(NO) and Fe(TPP)(NO(3)).     

Kinetics and mechanism of the reaction betweencis-dichlorobisbipyridineruthenium(II) and nitric acid in water-methanol solutions

Summary The kinetics of the reaction betweencis-dichlorobisbipyridineruthenium(II) and nitric acid have been investigated spectrophotometrically in the 25°–40° range in the presence of 0.03 to 0.2 mol dm^–3 HNO₃. The reaction proceeds with the stepwise formation of monoaqua and diaqua products. Only the formation of the monoaqua intermediate was followed as this species could not be obtained in a pure state. Aquation proceeds through a dissociative process. The second order rate constants are 11.8 (25°), 17.5 (30°); 30.0 (35°) l mol^–1 s^–1. Activation parameters are H 52±3 kJ mol^–1; S–108±8 JK^–1 mol^–1.     

Mechanistic studies of nitric oxide reactions with water soluble iron(II), cobalt(II), and iron(III) porphyrin complexes in aqueous solutions: implications for biological activity.

The reactions of nitric oxide and carbon monoxide with water soluble iron and cobalt porphyrin complexes were investigated over the temperature range 298-318 K and the hydrostatic pressure range 0.1-250 MPa [porphyrin ligands: TPPS = tetra-meso-(4-sulfonatophenyl)porphinate and TMPS = tetra-meso-(sulfonatomesityl)porphinate]. Large and positive DeltaS(double dagger) and DeltaV(double dagger) values were observed for NO binding to and release from iron(III) complexes Fe(III)(TPPS) and Fe(III)(TMPS) consistent with a dissociative ligand exchange mechanism where the lability of coordinated water dominates the reactivity with NO. Small positive values for Delta and Delta for the fast reactions of NO with the iron(II) and cobalt(II) analogues (k(on) = 1.5 x 10(9) and 1.9 x 10(9) M(-1) s(-1) for Fe(II)(TPPS) and Co(II)(TPPS), respectively) indicate a mechanism dominated by diffusion processes in these cases. However, reaction of CO with the Fe(II) complexes (k(on) = 3.6 x 10(7) M(-1) s(-1) for Fe(II)(TPPS)) displays negative Delta and Delta values, consistent with a mechanism dominated by activation rather than diffusion terms. Measurements of NO dissociation rates from Fe(II)(TPPS)(NO) and Co(II)(TPPS)(NO) by trapping free NO gave k(off) values of 6.3 x 10(-4) s(-1) and 1.5 x 10(-4) s(-1). The respective M(II)(TPPS)(NO) formation constants calculated from k(on)/k(off) ratios were 2.4 x 10(12) and 1.3 x 10(13) M(-1), many orders of magnitude larger than that (1.1 x 10(3) M(-1)) for the reaction of Fe(III)(TPPS) with NO.