Synthesis and structural characterization of nitrite-coordinating CoII and CoIII complexes as models for the reaction center of Co-substituted nitrite reductase

Co^II and Co^III complexes containing nitrite and tridentate aromatic amine compounds [bis(6-methyl-2-pyridylmethyl)amine (Me₂bpa) and bis(2-pyridylmethyl)amine (bpa)] have been prepared as models of the catalytic center in Co-substituted nitrite reductase: [Co^II(Me₂bpa)(NO₂)Cl]₂ · acetone (2), Co^II(Me₂bpa)(NO₂)₂ (3), Co^II(bpa)(NO₂)Cl (4), Co^II(bpa)(NO₂)₂ (5), Co^III(Me₂bpa)(NO₂)(CO₃) (6), and Co^III(bpa)(NO₂)₃ (7). The X-ray crystal structure analyses of these Co^II and Co^III complexes indicated that the geometries of the cobalt centers are distorted octahedral and the Me₂bpa and bpa with three nitrogen donors exhibit mer- (2, 3, and 7) and fac-form (4 and 6). The coordination mode of nitrite depends on the cobalt oxidation state, to Co^II through the oxygen (nitrito coordination, O- and O,O-coordination) and to Co^III through nitrogen (nitro coordination, N-coordination mode). These findings are consistent with the results of their IR spectra, except that another oxygen of the O-coordinated nitrito group in 3 might interact weakly with Co^II according to its IR spectrum. Reductions of the nitrite in 2, 3, 4, and 5 to nitrogen monoxide were not accelerated in the presence of proton, perhaps due to the nitrito coordination in these Co^II complexes.     

Syntheses,crystal structures,and electrochemical studies of dinuclear coordination compounds with the Fe2(CO)6 core

Reaction of 2-C₅H₄ NCOSPh, generated from 2-C₅H₄NCO₂H and PhSH in the presence of DCC, with Fe₃(CO)₁₂ affords (μ-κ²C,N-2-C₅H₄N)(μ-PhS)Fe₂(CO)₆ (1) and (μ-PhS)₂Fe₂(CO)₆ (2). Reaction of (NC)₂C=C(SMe)₂, formed from NCCH₂CN, CS₂, and MeI in the presence of NaOH, with Fe₃(CO)₁₂ provides (μ-κ²C,S-(NC)₂C=CSMe)(μ-MeS)Fe₂(CO)₆ (3) and (μ-MeS)₂Fe₂(CO)₆ (4). All complexes have been fully characterized by EA, IR, ¹H NMR, and ¹³C NMR spectroscopy and structurally determined by X-ray crystallography. In 1 and 3, the group attached to the bridging S is at the equatorial position. In 2, two phenyl groups are at equatorial positions. Two isomers of 4, ae-4 and ee-4, can be separated by thin-layer chromatography. DFT calculations reveal that the Gibbs energy difference between ae-4 and ee-4 is ?2.17 kcal mol^?1 in THF and ?2.29 kcal mol^?1 in benzene, and the isomerization barrier between ae-4 and ee-4 is 14.92 kcal mol^?1 in THF and 16.84 kcal mol^?1 in benzene. All these results suggest that ae-4 is more stable than ee-4 in either THF or benzene, and the two isomers do not interconvert. Electrochemical studies of 1 and 3 demonstrate that using HOAc as a proton source 1 and 3 can catalyze H₂ production.     

Titanium-Substituted Heteropolytungstates as Model Catalysts for Studying the Mechanisms of Selective Oxidation by Hydrogen Peroxide

The ³¹P NMR method shows that four forms of titanium(IV)-monosubstituted Keggin-type heteropolytungstate (Ti–HPA) exist in MeCN: the dimer (Bu₄N)₇[{PTiW₁₁O₃₉}₂OH] (in the abbreviated form, (PW₁₁Ti)₂OH or H1), its conjugate base (PW₁₁Ti)₂O (1), and two monomers, PW₁₁TiO (2) and PW₁₁TiOH (H2). The ratio between the forms depends on the concentrations of H⁺and H₂O. Dimer H1is produced from 2in MeCN when H⁺(1.5 mol) is added, and monomer H2is the key intermediate in this process. The catalytic activity of Ti–HPA in the oxidation of thioethers by H₂O₂correlates with their activity in peroxo complex formation and decreases in the order H2> H1> 2. The reaction of 2with H₂O₂in MeCN occurs slowly to form the inactive peroxo complex PW₁₁TiO₂(A). The addition of H₂O₂to H1and H2most likely results in the formation of the active hydroperoxo complex PW₁₁TiOOH (B). Complexes Aand Btransform into each other when H⁺or OH^–(1 mol) is added per 1 mol of Aor B, respectively. The activity of Btoward thioethers in the stoichiometric reaction is proven by ³¹PNMR and optical spectroscopy.     

NMR and theoretical study on the linking properties of peroxovanadium(V) complexes with the 3-aminomethyl-pyridine derivatives

To understand the substitution effects of 3-aminomethyl-pyridine on the reaction equilibrium, the interactions between a series of 3-aminomethyl-pyridine derivatives and peroxovanadium(V) complex [OV(O₂)₂(D₂O)]^?/[OV(O₂)₂(HOD)]^? in solution were explored by the combined use of multinuclear (¹H, ¹³C, and ⁵¹V) magnetic resonance spectroscopy together with HSQC in 0.15 M NaCl ionic medium for mimicking the physiological conditions. Some direct NMR data are given for the first time. The relative reactivity among the 3-aminomethyl-pyridine derivative ligands are N-(pyridin-3-ylmethyl)acetamide (1) ≈ N-(pyridin-3-ylmethyl)propionamide (2) > N-(pyridin-3-ylmethyl)pivalamide (3) > t-butyl(pyridin-3-ylmethyl)carbamate (4). The competitive coordination results in the formation of a series of new six-coordinate peroxovanadium species [OV(O₂)₂L]^? (L = 1–4). The results of density functional calculations indicated that the solvation effects play an important role in these reactions, providing a reasonable explanation on the relative reactivity of the 3-aminomethyl-pyridine derivatives.     

Two new clusters with MnII-MnIV magnetic exchange from the use of polyalcohol ligands

Two mixed-valence Mn(II,IV) complexes, [Mn^II₄Mn^IV₃(teaH)₃(tea)(thmeH)₃(thme)](ClO₄)₂·3MeCN (1) and [Mn^II₂Mn^IV₂(edteH)₂(peolH)₂]·4MeOH (2), where H₄edte = N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine, teaH₃ = tris(2-hydroxyethyl)amine, H₄peol = pentaerythritol, and H₃thme = 1,1,1-tris(hydroxymethyl)ethane, were prepared from the corresponding manganese salts and mixed ligands with polyalcohols. The two clusters consist of a trapped-valence polynuclear core comprising 4Mn^II and 3Mn^IV for 1, 2Mn^II and 2Mn^IV ions for 2. Complex 1 crystallizes in the rhombohedral space group R3c, while 2 crystallizes in the monoclinic space group P2₁/c. Complex 1 consists of a near-planar Mn₇ unit that comprises a Mn₆ hexagon of alternating Mn^II and Mn^IV ions surrounding a central Mn^II ion. The remaining coordinated sites are occupied by eight different deprotonation degrees of H₃tea or H₃thme. The tetranuclear cluster of 2 consists of a fused defective dicubane Mn₄O₆ core, and the four Mn ions are coordinated by oxygens from edteH^3? and peolH^3? into an unusual butterfly-like [Mn^II₂Mn^IV₂] topology. The two clusters are also characterized by mass spectra and X-ray photoelectron spectroscopy. Direct current magnetization studies reveal ferromagnetic interactions within both Mn clusters.     

ESR and quantum-chemical studies of the structure and thermal transformations of vinylcyclopropane radical cations in irradiated frozen Freon matrices. Simulation of radical processes in the gas phase

Thermal trasfomations of vinylcyclopropane (VCP) radical cations (RC) in X-ray irradiated frozen Freon matrices, CFCl₂CF₂Cl and CFCl₃, were studed by ESR. Radical processes involving VCP^.+ in very rarefied and moderately thickened gaseous VCP were simulated. Monomolecular cleavage of the cyclopropane ring ofgauche-VCP^.+ (1) occurs to give the more thermally stable distonic radical cationdist(0.90)-C₅H₈ ^.+ (3). As the density of VCP increases RC3 adds at the double bond ofanti-VCP to give the distonic RC,^.CH₂CH₂CHCH(CH₂)₃CHCHCH₂ ⁺ (5). Under the same conditions, the less thermally stableanti-VCP^.+(2) undergoes monomolecular isomerization into RC1 or reacts withanti-VCP with the rearrangement (as in the condensed phase) to give its distonic form,dist(90.0)-C₅H₈ ^.+ (4). The MNDO-UHF method was adapted for quantum-chemical analysis of the constants of isotropic hyperfine coupling with¹H and¹³C nuclei in neutral and charged hydrocabon radicals, since the standard version of this method inadequately reproduces the structural parameters of low-symmetry (C ₁,C _s) paramagnetic species. A quantum-chemical analysis of the radiospectroscopic information and of the stereoelectronic control of thermal transformations of conformers of RC1 and2 into their structurally nonequivalent distonic forms3 and4, respectively, was carried out.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 212–235, February, 1995.This work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 93-03-04075).     

Studies on the manganese and copper complexes derived from chiral Schiff base: synthesis,structure, cytotoxicity and DNA/BSA interaction

Abstract

Three new manganese and copper complexes, [Mn(ONO-(S)L¹)₂] (1), [Cu(ONO-(R)L²)]₄·2CH₃OH (2), and [Mn₃(ONO-(S)L³)₄(OAc)₄(H₂O)₂] (3), {[H₂L¹ = (S)-2-phenyl-2-(2-hydroxy-5-chlorobenzylideneamino)ethane-1-ol], H₂L² = (R)-2-(2-hydroxy-5-chlorobenzylideneamino)butane-1-ol] and H₂L³ = (S)-2-phenyl-2-(2-hydroxy-3-methoxybenzylideneamino)ethane-1-ol]}, have been synthesized. The crystal structures of 1–3 were determined through single-crystal X-ray diffraction. The structure of mononuclear 1 shows a six-coordinate octahedral geometry around the manganese ion. Complex 2 is a five-coordinate tetranuclear copper complex with the central Cu atoms adopting distorted square pyramidal geometry. Complex 3 shows a trinuclear structure with the six-coordinate Mn ions surrounded by four L³ ligands and acetate ions. The in vitro cytotoxicity screening revealed that the 1–3 had substantial cytotoxicity against three cancer cell lines (HepG2, MDA-MB-231, and A549), even higher than that of cisplatin. Inspiringly, 2 derived from (R)-Schiff base ligand H₂L² was more potent against MDA-MB-231 cells. Interaction of 1–3 with calf-thymus DNA (CT-DNA) has been investigated using UV-vis, viscosity and thermal denaturation experiments. It was found that 1 binds with DNA through intercalation while 2 and 3 interact with DNA probably through groove-binding and electrostatic mode. In addition, the capability of the complexes to bind with bovine serum albumin was monitored using some spectral techniques. The metal ions, chiral and nuclearity have significant influences on the properties of the title compounds.     

Syntheses,characterization of and studies on the electrochemical behaviour of ferrocenyl dithiophosphonates and 4-methoxyphenyl dithiophosphonates

Some 1,3-dithiadiphosphetane 2,4-disulfides (X₂P₂S₄, X: Fc, FcLR; X: CH₃O?C₆H₄?, LR) were allowed to react with alcohols to obtain dithiophosphonic acids (X(OR)PS₂H). These were converted to the corresponding ammonium salts. The salts were of the structures [Fc(OR)PS₂]^?[NH₄]⁺, R: 3-methyl-1-butyl- for I; 1-phenyl-1-propyl- for II; 3-pentyl- for III; 3-phenyl-1-propyl- for IV and [CH₃O?C₆H₄(OR)PS₂]^?[NH₄]⁺, R: 3-methyl-1-butyl- for V and 1-phenyl-1-propyl- for VI. To the best of our knowledge, all the compounds except V were prepared for the first time.

The compounds synthesized were characterized by elemental analysis, NMR (¹H, ¹³C, ³¹P), MS, FTIR, and Raman spectroscopies. Electrochemical behaviors of I–VI at disposable pencil graphite electrode (PGE) were investigated by using cyclic voltammetry (CV) and square-wave voltammetry (SWV). Adsorption and diffusion patterns of all the compounds on the PGE were also studied.

Two electroactive groups were identified in the compounds I–IV and only one in V and VI. The ferrocenyl groups of I-IV were oxidized at around 0.4 V. The same compounds display a second, more intense CV band at 0.8 V. The corresponding band for the compounds V–VI appears at around 0.6 V with a much weaker intensity. It is suggested that the ferrocenyl group introduced into the structures stabilizes the radical species formed as the product of the oxidation of the dithiophosphonato group.     

Synthesis and thermodynamic studies of the dinuclear adducts between dimethyltin(IV) dichloride with SalenH2 and MII(Salen) complexes in chloroform

A UV-Vis spectrophotometric study of adduct formation of SalenH₂ (1) and M^II(Salen), where M?=?Mn (2), Fe (3), Co (4), Ni (5) and Cu (6) as donors with Me₂SnCl₂ as acceptor have been investigated in chloroform. Adducts (1a–6a) have been characterized by ¹H, ¹³C and ¹¹⁹Sn NMR, IR and electronic spectroscopy and microanalysis. Formation constants and thermodynamic parameters were measured for 1 : 1 and 2 : 1 adducts at various temperatures (T?=?278 to 308 K). The data refinement was carried out with the SQUAD 84 program. The trend of formation constants of M^II(Salen) complexes with Me₂SnCl₂ follows the order: Mn>Fe>Cu>Co>Ni. The formation constants for the free 1 and M^II(Salen) with Me₂SnCl₂ changes according to the following trend: M^II(Salen)>SalenH₂     

NMR and theoretical study on the coordination interactions between peroxovanadium(V) complex and bisubstituted pyridine ligands

To understand the substitution effects of pyridine ligands on coordination equilibrium, the coordination interactions between a series of bisubstituted pyridine ligands and peroxovanadium(V) [OV(O₂)₂(D₂O)]^?/[OV(O₂)₂(HOD)]^? in solution have been investigated by multinuclear (¹H, ¹³C, and ⁵¹V) magnetic resonance and HSQC. A series of new six-coordinate peroxovanadate complexes [OV(O₂)₂L] ^{n ?} (L?=?2, 3, 4, n?=?1 or 3) have been observed, and the coordination ability of the bisubstituted pyridines to peroxovanadium(V) is 3,4-dimethylpyridine (2)?>?3,5-dimethylpyridine (3)?>?pyridine-3,5-dicarboxylate (4)???2,3-dimethylpyridine (1). The coordination interactions among title system have been further studied by DFT (density functional theory) calculations, and the results indicate that solvent may play an important role in these coordination interactions.     

DFT analysis of the active site in catalytic metabolic redox reactions of mononuclear molybdenum enzymes

Abstract

Model complexes [Mo^VIO₂(S₂C₂Me₂)SMe]^? (A, derived from the X-ray crystal structure of native sulfite oxidase (SO)) and [Mo^VIO₂(mnt)₂]^2? (B, coordination mode similar to the active site of selenate reductase (SeR)) were computed at the COSMO-B3LYP/SDDp//B3LYP/Lanl2DZ(p) energy level of Density Functional Theory in order to study their behavior in oxidation of selenite (Se^IV) and sulfite (S^IV) to selenate (Se^VI) and sulfate (S^VI), respectively. For the oxidation of sulfite, computational model A, which resembles the SO active site, is clearly the best choice (lowest barrier, minor exothermicity). For the reduction of selenate, a smaller activation is computed for model A; however, the reaction is less exothermic with model B, which resembles the SeR active site.     

High-temperature spin transition in the iron(II) trifluoromethylsulfonate,perrhenate, and tetraphenylborate complexes with tris(pyrazol-1-yl)methane

New coordination compounds of iron(II) trifluoromethylsulfonate, perrhenate, and tetraphenylborate with tris(pyrazol-1-yl)methane (HC(Pz)₃) of the composition [Fe(HC(Pz)₃)₂]A₂ (A = CF₃SO₃ ⁻ (I), ReO₄ ⁻ (II), and B(C₆H₅)₄ ⁻ (III)) were synthesized and studied by the method of static magnetic susceptibility and IR and electronic spectroscopies. The crystal and molecular structures of compounds I and II were determined by X-ray diffraction analysis. The magnetochemical study of complexes I—III in the interval from 275 to 500 K showed that they possessed the high-temperature spin transition ¹ A ₁ ⇄ ⁵ T ₂ accompanied by thermochromism.     

NMR parameters of the tetrahedrane [Fe2(CO)6(μ-SNH)], studied by experiment and DFT

The intramolecular dynamic behavior of the tetrahedrane-type cluster [Fe₂(CO)₆(μ-SNH)] 1 was studied by ¹³C NMR spectroscopy. The ⁵⁷Fe chemical shift of 1 and the coupling constants ¹ J(⁵⁷Fe,¹³C) were measured. These NMR parameters, and also ¹ J(⁵⁷Fe,¹⁵N), were found to be in good agreement with data calculated by using density functional theory (DFT) methods (B3LYP), based on the geometry calculated at the 6-311+G(d,p) level of theory. The isolobal replacement of the Fe(CO)₃ with BH fragments leads to the tetrahedranes [Fe(CO)₃(BH)(μ-SNH)] 2 and [(HB)₂(μ-SNH)] 3. Both were identified by calculations as minima on the respective potential energy surface (PES). However, the tetrahedrane-type structure of 3 is much higher in energy when compared with the planar cyclic isomers 3a and 3b.     

Solvent effects on the dimensionality of oxamato-bridged manganese(II) compounds

Abstract

Two new oxamate-containing manganese(II) complexes, [{Mn(H₂edpba)(H₂O)₂}₂]_n (1) and [Mn(H₂edpba)(dmso)₂]?dmso?CH₃COCH₃?H₂O (2) (H₄edpba = N,N′-ethylenediphenylenebis(oxamic acid) and dmso = dimethylsulfoxide), have been synthesized and the structures of 1 and 2 were characterized by single crystal X-ray diffraction. The structure of 1 consists of neutral honeycomb networks in which each manganese(II) is six-coordinate by one H₂edpba^2? ligand and two carboxylate–oxygens from two other H₂edpba^2? ligands building the equatorial plane. Each manganese is connected to its nearest neighbor through two carboxylate(monoprotonated oxamate) bridges in an anti-syn conformation. A dmso solution of single crystals of 1 was placed under acetone atmosphere affording 2, whereas putting 2 in equimolar water:ethanol mixture results in 1. The molecular structure of 2 is made up of mononuclear manganese(II) units which are interlinked by weak C–H?π and edge-to-face π-stacking interactions leading to supramolecular chains along the crystallographic b axis. Magnetic measurements reveal the occurrence of an antiferromagnetic coupling between two manganese(II) ions through anti-syn carboxylate bridges for 1 [J = ?1.18 cm^?1, the Hamiltonian being defined as H = ?J S₁^.S₂] and very weak intrachain ferromagnetic interactions in 2 [J = + 0.046 cm^?1, H = ?J ∑_iS_i^.S_i + 1].     

An Examination of the Coordination Chemistry of L2Pt(1,2-DITHIOLENES) Using Atmospheric Pressure Chemical Ionization Mass Spectrometry

Abstract

Atmospheric pressure chemical ionization mass spectrometry (APCI–MS) has been utilized in the characterization of two series of platinum dithiolene complexes, (COD)Pt(dt) 1, (COD)–Pt(edt) 2, (COD)Pt(dmid) 3, (COD)Pt(mnt) 4, (COD)Pt(eddo) 5, (COD)Pt(dddt) 6 and (Ph₃P)₂Pt(dt) 7, (Ph₃P)₂Pt(edt) 8, (Ph₃P)₂Pt(dmid) 9, (Ph₃P)₂Pt(dmit) 10, (Ph₃P)₂Pt(mnt) 11 (where COD = 1,5–cyclooctadiene, dt = ethane–1,2–dithiolate, edt = ethylene–1,2–dithiolate, dmid = 1,3–dithiole–2–oxo–4,5–dithiolate, dmit = 1,3–dithiole–2–thione–4,5–dithiolate, mnt = maleonitrile–1,2–dithiolate, eddo = 4–(ethylene–1′,2′–dithiolate)–1,3-dithiole–2–one, and dddt = 5,6–dihydro–1,4–dithiin–2,3–dithiolate). The series that contains triphenylphosphine is labile toward the loss of HPPh₃ ⁺. In addition, an orthometallated species involving the platinum and triphenylphosphine is identified. A dimer is identified for 2, which is shown to be a product of the experiment and not present in the parent material. In addition, a 1:1 adduct with NH₄ ⁺ is identified for 4 and 11 where the NH₄ ⁺ originates from the acid hydrolysis of acetonitrile. Finally, a highly unique ion, Pt⁺, a bare platinum ion, is observed in all COD complexes indicating that a radical mechanism must accompany the decomposition of the COD complexes during the fragmentation process.     

Ring opening in epichlorohydrin and β-methylepichlorohydrin under the action of the [PtCl4]2– anion in aqueous solutions

Oxidative addition of epoxides to [PtCl₄]^2– in aqueous acids affords the platinum(iv) derivatives [PtCl₅(CH₂CR(OH)CH₂Cl)]^2– (R = H (1) and Me (2)). Complex 1 was isolated as a cesium salt and characterized by IR spectroscopy. The complex is stable in acidic media; under basic conditions, the original epoxide and platinum(ii) are recovered. The formation of complex 2 was detected by ¹H NMR spectroscopy.     

Formation of phosphonates and pyrophosphates in the reactions of chlorophosphate esters with strong organic bases

The compounds S(6-t-Bu-4-Me-C₆H₂O)₂P(O)Cl (1), CH₂(6-t-Bu-4-Me-C₆H₂O)₂P(O)Cl (2) and (2,2′-C₂₀H₁₂O₂)P(O)Cl (3) react with diazabicycloundecene (DBU) to give rise to, predominantly, the phosphonate compounds [S(6-t-Bu-4-Me-C₆H₆O)₂P(O)(DBU)]⁺[Cl]⁻ (4), [CH₂(6-t-Bu-4-Me-C₆H₂O)₂P(O) (DBU)]⁺[Cl]⁻ (5) and [(2,2′-C₂₀Hi₂O₂)P(0)(DBU)]⁺[Cl]^- (6). The first two compounds could be isolated in the pure state. In analogous reactions of 1 and 2 with diazabicyclononene (DBN) or N-methyl imidazole, only the pyrophosphates [S(6-t-Bu-4-Me-C₆H₂O)₂P(O)]₂O (7) and [CH₂(6-t-Bu-4-Me-C₆H₂O)₂P(O)]₂O (8) could be isolated, although the reaction mixture showed several other compounds in the phosphorus NMR. A possible pathway for the formation of phosphonate salts is proposed. The X-ray crystal structures of4,7 and8 are also discussed.     

Stacking reactions of the borole complex Cp*Rh(η5-C4H4BPh) with the dicationic fragments [Cp*M]2+ (M = Rh or Ir)

The reaction of the (borole)rhodium iodide complex [(η-C₄H₄BPh)RhI]₄ with Cp^*Li afforded the sandwich compound Cp^*Rh(η-C₄H₄BPh) (4). The reactions of compound 4 with the solvated complexes [Cp^*M(MeNO₂)₃]²⁺(BF ₄ ⁻ )₂ gave triple-decker cationic complexes with the central borole ligand [Cp^*Rh(η-η⁵:η⁵-C₄H₄BPh)MCp^*]²⁺(BF ₄ ⁻ )₂ (M = Rh (5) or Ir (7)). The structure of complex 4 was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1525–1527, September, 2006.     

Ten complexes constructed by two reduced Schiff base tetraazamacrocycle ligands: syntheses,structures, magnetic and luminescent properties

Ten new complexes, [Cu₂(L¹)(NO₃)₂]·2H₂O (1), [Cu₄(L¹)₂]·4ClO₄·H₂O (2), [Cu₂(L¹)(H₂O)₂]·(adipate) (3), [Cu₆(L¹)₂(m-bdc)₄]·2DMF·5H₂O (4), [Cu₂(L¹)(Hbtc)]·5H₂O (5), [Cu₂(L¹)(H₂O)₂]·(ntc)·3H₂O (6), [Co₂(L²)]·[Co(MeOH)₄(H₂O)₂] (7), [Co₃(L²)(EtOH)(H₂O)] (8), [Ni₆(L²)₂(H₂O)₄]·H₂O (9) and [Zn₄(L²)(OAc)₂]·0.5H₂O (10), have been synthesized. 1 displays a [Cu₂(L¹)(NO₃)₂] monomolecular structure. 2 shows a supramolecular chain including [Cu₂L¹]²⁺. In 3, two Cu(II) ions are connected by L¹ to form a [Cu₂(L¹)(H₂O)₂]²⁺ cation. In 4, the m-bdc anions bridge Cu(II) ions and L¹ anions to form a layer. Both 5 and 6 display 3-D supramolecular structures. 7 consists of both [Co₂L²]^2? and [Co(MeOH)₄(H₂O)₂]²⁺ units. 8 and 9 show infinite chain structures. In 10, Zn(II) dimers are linked by L² to generate a 3-D framework. The magnetic properties for 4 and 8 and the luminescent property for 10 have been studied.     

Iron(II) complexes containing the 2,6-bis-iminopyridyl moiety. Synthesis,characterization, reactivity,and DNA binding

Two iron(II) complexes, [Fe^II(py^tBuN₃)₂](FeCl₄) (1) and [Fe^II(py^tBuMe₂N₃)Cl₂] (2), with sterically constrained py^tBuN₃ and py^tBuMe₂N₃ chelate ligands (py^tBuN₃ = 2,6-bis-(aldiimino)pyridyl; py^tBuMe₂N₃ = 2,6-bis-(ketimino)pyridyl), have been synthesized and characterized by elemental analysis, IR, UV–vis spectra, and preliminary X-ray single-crystal diffraction. The latter revealed that Fe(II) in 1 is six-coordinate by six nitrogen donors from two bisiminopyridines in a distorted octahedron. Complex 2 reacts with thiourea with a second-order rate constant k₂ = (2.50 ± 0.05) × 10^?3 M^?1 s^?1 at 296 K, and the reaction seemed to be slow. In a similar way, the interaction of 2 and DNA was studied by fluorescence and absorption spectroscopy. The results revealed that 2 caused fluorescence quenching of DNA through a dynamic quenching procedure. The binding constants K_A, K_app, and K_SV as well as the number of binding sites between 2 and DNA were determined.