Formation of homo- and heteronuclear complexes of 1-hydroxyethylidene-1,1-diphosphonic acid with Mn<Superscript>II</Superscript> and Fe<Superscript>III</Superscript> in aqueous solutions

Systems based on 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), iron(iii)—HEDP and manganese(ii)—iron(iii)—HEDP, were studied by pH-potentiometry combined with mathematical modeling and NMR. Diverse and highly stable heteronuclear iron manganese complexes were found to exist in the heteronuclear system. The formation of the MnH₃L₂^3–, FeMnH₃L₂⁰, Fe₂MnHL₃^3–, and MnL^2– complexes was established. The relaxation efficiency coefficient REC₂ (relaxivity) of these complexes was evaluated at ~2000 mol^–1 s^–1 L. Therefore, these systems hold promise as MRI contrast agents.     

Spectroscopic and thermal investigations of complexes of Cr<Superscript>III</Superscript>, Mn<Superscript>II</Superscript>, Zn<Superscript>II</Superscript> &; Cd<Superscript>II</Superscript> - carboxamide

Complexes of Cr^III, Mn^II, Zn^II & Cd^II with the polydentate carboxamide ligandN′, N′′-bis(3-carboxy-1-oxoprop-2-enyl) 2-Amino-N-arylbenzamidine (H₂L) have been synthesized and characterized by elemental analyses, spectroscopic studies (Vibrational, electronic, ESR and ¹H-NMR), magnetic susceptibility measurements, thermal studies and powder diffraction studies. The vibrational spectral data are in agreement with coordination of amide and carboxylate oxygen of the ligands with the metal ions. The electronic spectra indicates octahedral or tetrahedral geometry around the metal ions, has been supported by magnetic susceptibility measurements. The results of electron spin resonance & ¹H-NMR spectra have supported the results of other spectral techniques. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. Powder diffraction determines the cell parameters of the complexes.     

Liquid extraction of La<Superscript>III</Superscript>, Gd<Superscript>III</Superscript>, and Yb<Superscript>III</Superscript> ions by phosphorylated calix[4]resorcinarene derivatives

New phosphorylated calix[4]resorcinarene and cavitands were synthesized. Their extraction ability toward La^III, Gd^III, and Yb^III ions was studied. The cavitands are more efficient extracting agents than octasubstituted calix[4]resorcinarenes. The nature of substituents at the nitrogen atom at the upper rim and hydrophobic substituents at the lower rim exerts a substantial effect on the solubility of the extracted complex in chloroform. Coordination of two lanthanide ions with an extragent molecule results in their efficient but non-selective extraction. The literature and our spectral (³¹P NMR) data suggested that the ligand in the extracted complex has most probably a “kite” conformation. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 303–308, February, 2007.     

Heterospin complexes of fluorinated dinuclear Cu<Superscript>II</Superscript> and Mn<Superscript>II</Superscript> triketonates with nitroxides

Dinuclear heterospin complexes of Cu^II and Mn^II 1,1,1,7,7,7-hexafluoroheptane-2,4,6-trionates ([Cu₂L₂] and [Mn₂L₂], respectively) with nitronyl nitroxides 2-R-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide 1-oxyls (NIT-R, R = H, Me, Et, m-C₅H₄N, m-NCC₆H₄, p-NCC₆H₄, PzMe) and the diradical NIT-Pz-(CH₂)₄-Pz-NIT (Pz is 1,4-pyrazolylene) were synthesized and structurally characterized. In the complexes under study, the CuII atom tends to have the square-pyramidal coordination environment, and the MnII atom is in an octahedral environment. The magnetochemical investigation of the compounds in the temperature range of 2–300 K showed that the antiferromagnetic exchange coupling dominates in the [Cu₂L₂] molecules, whereas this coupling in [Mn₂L₂] is manifested in the experimental plot μ_eff(T) at T < 100 K. The magnetic properties of the heterospin complexes of [Cu₂L₂] with NIT-R are also determined by the intramatrix antiferromagnetic exchange coupling. For the complexes of [Mn₂L₂] with NIT-R, the coordination mode of the nitroxide plays a decisive role.     

Synthesis,characterization and DNA-binding studies of 1-(pyridin-2-yl)-3-tosylurea and its Nd<Superscript>III</Superscript>, Eu<Superscript>III</Superscript> complexes

1-(Pyridin-2-yl)-3-tosylurea(HL) and its two lanthanide complexes, LnL₃ · H₂O [Ln = Nd(1), Eu(2)], have been synthesized and characterized on the base of elemental analyses, molar conductivities, IR spectra and thermal analyses. In addition, the DNA-binding properties of the two complexes have been investigated by absorption, fluorescence and viscosity measurements. The experimental results indicated that the complex (1) and (2) can bind to DNA; the binding affinity of the complex (1) is higher than that of complex (2) and the intrinsic binding constants of complex (1) and complex (2) with DNA were 1.24 × 10⁴ m ⁻¹ and 8.7 × 10³ m ⁻¹, respectively. In addition, some factors that influence the fluorescent intensity were also discussed.     

Synthesis and photophysical properties of Ir<Superscript>III</Superscript>-Ln<Superscript>III</Superscript> (Ln = Nd,Yb, Er) bimetallic complexes containing bipyrimidines as bridging ligands

Bipyrimidines have been chosen as (N∧N)(N∧N) bridging ligands for connecting metal centers. Ir^III-Ln^III (Ln = Nd, Yb, Er) bimetallic complexes [Ir(dfppy)₂(μ-bpm)Ln(TTA)₃]Cl were synthesized by using Ir(dfppy)₂(bpm)Cl as the ligand coordinating to lanthanide complexes Ln(TTA)₃·2H₂O. The stability constants between Ir(dfppy)₂(bpm)Cl and lanthanide ions were measured by fluorescence titration. The obvious quenching of visible emission from Ir^III complex in the Ir^III-Ln^III (Ln = Nd, Yb, Er) bimetallic complexes indicates that energy transfer occurred from Ir^III center to lanthanides. NIR emissions from Nd^III, Yb^III, and Er^III were obtained under the excitation of visible light by selective excitation of the Ir^III-based chromophore. It was proven that Ir(dfppy)₂(bpm)Cl as the ligand could effectively sensitize NIR emission from Nd^III, Yb^III, and Er^III.     

Heterospin Mn<Superscript>III</Superscript> complex as a reaction product of the redox-induced change in the ligand coordination mode

The reaction of Mn^II chloride with imino nitroxide radical, 2-(2-hydroxy-5-nitrophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl (HL²), affords the Mn^III complex [MnL² ₂L³]·Me₂CO, a distinctive feature of which is the simultaneous presence in the ligand shell of both the initial imino nitroxide and the product of its reduction 2-(2-hydroxy-5-nitrophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide (HL³). The reaction involves the oxidation of Mn^II to Mn^III and the reduction of the imino nitroxide radical to the corresponding amidine oxide along with a change in the coordination mode of the heterocyclic ligand on going from L² to L³. The Mn^III ion forms with L² six-membered metallocycles typical of Schiff bases, whereas with L³ Mn^III forms a seven-membered metallocycle due to the coordination of L³ by oxygen atoms of the phenol and N-oxide It was found in a similar reaction of Ni^II chloride with imino nitroxide HL² that no oxidation of the metal occurred and bis(chelate) [NiL² ₂(H₂O)₂]·2Me₂CO was formed in the solid phase. The molecular and crystal structures of the compounds were determined, and their magnetic properties were studied.     

Mixed ligand complexes of Fe<Superscript>III</Superscript> containing pseudohalides,nitrosyl and some mannich bases

Reactions of Pentapseudohalonitrosyl ferrate(II) with Morpholinobenzyl benzamide(MBB) and Piperidinobenzyl benzamide(PBB) formed complexes of the type, [Fe(X)₃(NO)(L–L)] where X = CN⁻, NCO⁻ and N ₃ ⁻ and L–L = Morpholinobenzyl benzamide(MBB) and Piperidinobenzyl benzamide(PBB). These compounds have been characterized by various physico-chemical techniques such as elemental analysis, molar conductance, magnetic susceptibility measurements, i.r., electronic spectra, thermal gravimetric analysis. The molecular modeling Studies have been carried out for structural analysis for some of the complexes have been carried out using Hyperchem release 7.52 professional version.     

Heat capacity and magnetic phase transition of two-dimensional metal-assembled complex (NEt<Subscript>4</Subscript>)[{Mn<Superscript>III</Superscript>(salen)}<Subscript>2</Subscript>Fe<Superscript>III</Superscript>(CN)<Subscript>6</Subscript>]

Summary Heat capacity measurements of the two-dimensional metal-assembled complex, (NEt₄)[{Mn^III(salen)}₂Fe^III(CN)₆] [Et=ethyl, salen= N,N’-ethylenebis(salicylideneaminato) dianion], were performed in the temperature range between 0.2 and 300 K by adiabatic calorimetry. A ferrimagnetic phase transition was observed at T_c1=7.51 K. Furthermore, another small magnetic phase transition appeared at T_c2=0.78 K. Above T_c1, a heat capacity tail arising from the short-range ordering of the spins characteristic of two-dimensional magnets was found. The magnetic enthalpy and entropy were evaluated to be ΔH=291 J mol^-1 and ΔS=27.4 J K^-1 mol^-1, respectively. The experimental magnetic entropy agrees roughly with ΔS=Rln(5·5·2) (=32.5 J K^-1 mol^-1; R being the gas constant), which is expected for the metal complex with two Mn(III) ions in high-spin state (spin quantum number S=2) and one Fe(III) ion in low-spin state (S=1/2). The heat capacity tail above T_c1 became small by grinding and pressing the crystal. This mechanochemical effect would be attributed to the increase of lattice defects and imperfections in the crystal lattice, leading not only to formation of the crystal with a different magnetic phase transition temperature but also to decrease of the magnetic heat capacity and thus the magnetic enthalpy and entropy.     

A novel Ce<Superscript>III</Superscript>-cyclam type complex and its redox chemistry in aqueous solutions

A new Ce^III complex was synthesized by mixing the ligand “dioxocyclam” with Ce^III ions at pH 8.0 and its redox properties were investigated.

Heterospin mixed-ligand heterotrinuclear Co<Superscript>II</Superscript>, Gd<Superscript>III</Superscript>, Co<Superscript>II</Superscript> complex with nitronyl nitroxide

A method was developed for the synthesis of mixed-metal heterospin compounds with the direct coordination of the nitroxide fragment based on the replacement of acetonitrile molecules in the heterotrinuclear complex [Co₂Gd(NO₃)Piv₆(CH₃CN)₂] with nitroxide molecules. The molecular and crystal structure of the heterospin mixed-ligand heterotrinuclear Co^II, Gd^III, Co^II complex [Co₂Gd(NO₃)Piv₆(NIT-Me)₂], where NIT-Me is stable nitronyl nitroxide, was established. The magnetic properties of this complex were investigated in the temperature range of 2–300 K. The coordination of nitroxide groups to Co^II ions is responsible for strong exchange interactions between the unpaired electrons in the exchange clusters {>-·O-Co^II}, resulting in the virtually complete spin coupling between each coordinated >N-·O group and one of the unpaired electrons of each Co^II ion at temperatures below 200 K. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1742–1745, September, 2007.     

Synthesis,structure, and luminescent properties of Pr<Superscript>III</Superscript> complexes with pyrazole-derived 1,3-diketone and 1,10-phenanthroline

The interaction of PrCl₃ with 1,3-bis(1,3-dimethyl-1H-pyrazol-4-yl)-1,3-propanedione in aqueous ethanol in the presence of a base and 1,10-phenanthroline was studied. It was shown that the composition of the products was dependent on the reaction conditions. The solvate [Pr(L)₃(Phen)]?3PrⁱOH crystallizes in a monoclinic crystal system (P2₁/c space group, a = 12.2239(12) Å, b = 20.3403(19) Å, c = 26.134(3) Å, β = 102.380(2)° at 150 K). Absorption spectra of the complex in solution, as well as the spectra and the kinetic parameters of photo-luminescence were investigated.     

Investigation on sonocatalytic damage of BSA under ultrasonic irradiation by Fe<Superscript>III</Superscript> complexes with some aminocarboxylic acid

The interaction of BSA and Fe^III complexes ([Fe^III(gly)(H₂O)₄]²⁺, [Fe^III(ida)(H₂O)₃]⁺, and [Fe^III(nta)(H₂O)₂], gly—glyane, ida—iminodiacetic acid, nta—triglycolamic acid) as well as the sonocatalytic damage to BSA was studied by UV-vis and fluorescence spectra. In addition, the influences of ultrasonic irradiation time and Fe^III complex concentration were also examined on the sonocatalytic damage to BSA. The results showed that the fluorescence quenching of BSA solution caused by the Fe^III complexes belonged to the static quenching process. The BSA and Fe^III complexes interacted with each other mainly through weak interaction and coordinate actions. The binding association constants (K) and binding site numbers (n) were calculated. The results were as follows: K ₁ = 0.5353 × 10⁴ l mol⁻¹ and n ₁ = 0.9812 for [Fe^III(gly)(H₂O)₄]²⁺, K ₂ = 1.4285 × 10⁴ l mol⁻¹ and n ₂ = 1.0899 for [Fe^III(ida)(H₂O)₃, and K ₃ = 0.4411 × 10⁴ l mol⁻¹ and n ₃ = 0.9471 for [Fe^III(nta)(H₂O)₂]. Otherwise, under ultrasonic irradiation the BSA were obviously damaged by the Fe^III complexes. The damage degree rose up with the increase of ultrasonic irradiation time and Fe^III complex concentration. And that, [Fe^III(nta)(H₂O)₂] exhibited in a way higher sonocatalytic activity than [Fe^III(gly)(H₂O)₄]²⁺ and [Fe^III(ida)(H₂O)₃]⁺.     

Chemical assembly of the heteronuclear pivalate complex with the Li<Superscript>I</Superscript> and Fe<Superscript>III</Superscript> ions

The heteronuclear complex [Fe₄Li₂(O)₂(Piv)10(H₂O)₂] (1, Piv is the pivalic acid anion) was obtained by refluxing Fe^III pivalates with Li^I pivalates in toluene and isolated as the 1?PhCH₃ solvate with a toluene molecule. According to X-ray diffraction data, complex 1 contains the {Fe₄Li₂O₂} core. The Mössbauer spectroscopy data indicate that the core comprises para magnetic Fe^III ions in the high-spin state located in the symmetric octahedral environment of oxygen atoms. Thermolysis of 1 studied by simultaneous thermal analysis demonstrated thermal stability of the complex up to 225 °С. The main end product of thermolysis at 600 °С is the mixed oxide LiFe₅O₈.     

New antiferromagnetic tetranuclear pivalate complex containing Fe<Superscript>III</Superscript> and Fe<Superscript>II</Superscript> atoms

The interaction of [K₂Fe^III ₄(O)₂(OOCCMe₃)₁₀(HOOCCMe₃)₂(H₂O)₂]_n with 2-pyridinecarboxaldehyde results in a mixed-valence complex Fe^IIFe^III ₃(μ₃-O)₂(μ₂-OOCCMe₃)₇L₂··2.5MeCN·3H₂O (L = 2-NC₅H₄COOH_0.75K_0.25). The structure of the complex was established by X-ray analysis. The magnetic properties of the complex were studied. Dedicated to Academician A. L. Buchachenko on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2145–2148, September, 2005.     

Reactions of N-P<Superscript>III</Superscript>-Phosphorylated Trifluoroacetamides with (Ethoxycarbonyl)triphenylmethylide

N-P^III-Phosphorylated trihaloacetamides act as phosphorylating agents with respect to (ethoxycarbonyl) triphenylmethylide. The reactions give rise to C-phosphorylated ylides and O-(diethoxyphosphino)-phosphaketene acetals.     

Crystal structure of a novel two-dimensional supramolecular network based on polyoxoanion and yttrium<Superscript>III</Superscript> coordination cation

A novel compound (NH⁴)₂Y(H₂O)₈[PMo₁₀V₂O₄₀]·10H₂O has been prepared in an aqueous solution and characterized by elemental analysis, IR, and TG-DTG analysis. X-ray diffraction analysis was carried out on (NH₄)₂Y(H₂O)₈ [PMo₁₀V₂O₄0]·10H₂O single crystal, which crystallizes in the monoclinic system of a space group P21/c witha=0. 9871 (3) nm,b=1. 5424 (5) nm,c=2.7924(9) nm, β = 94.183(5)° and Z=2. In the compound, a two-dimensional network is constructed by the PMo₁₀V₂O ₄₀ ^5? anion and the Y(H₂O) ₈ ³⁺ cation building blocks via hydrogen bonding exhibiting the porous structure.     

Polynuclear Co<Superscript>II,III</Superscript> compounds containing pivalate and hexafluoroacetylacetonate anions in the ligand shell and their heterospin complexes with nitroxides

The reaction of cobalt(II) bis(hexafluoroacetylacetonate) (Co(hfac)₂) with polynuclear Co^II or Co^II,III pivalates, [Na₂Co₄(OH)₂(Piv)₈(EtOH)₄], [Co₂(H₂O)(Piv)₄(HPiv)₄], and [Co^III ₂Co^II ₄(O)₂(Piv)₁₀(H₂O)(THF)₃]·1.5THF (Piv is pivalate), affords the previously unknown cobalt compounds containing coordinated Piv and hfac anions in the ligand shell, viz., the dinuclear complex [Na₂Co₂(hfac)₄(Piv)₂(Me₂CO)₄], the tetranuclear complex [Co₄(Piv)₄(hfac)₂(OH)₂(HPiv)₄]·HPiv, and the tetradecanuclear complex [Co^III ₄Co^II ₁₀(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(HPiv)₄]·2HPiv·2H₂O·3C₇H₁₆, respectively. The tetradecanuclear complex has an unusual ability to precipitate nitroxides from solution, due to which the following new heterospin crystalline solids were synthesized: [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(H₂O)₂(HPiv)₂]·2NIT-Me·2HPiv·C₆H₁₄, [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(HPiv)₄]·2NIT-Et·2CHCl₃, [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(HPiv)₄]·2NIT-Ph·2C₆H₁₄, [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(HPiv)₄]·2L¹·2CH₂Cl₂, and [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(HPiv)₄]·2L²·C₆H₁₄, where NIT-Me, NIT-Et, and NIT-Ph are 2-imidazoline nitroxides, L¹ is 3-imidazoline nitroxide, and L² is di-tert-butyl nitroxide. The X-ray diffraction study showed that the efficient binding of nitroxides is provided by the specific arrangement of the μ₃-OH groups in the [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(HPiv)₄] molecule, which is spatially complementary for the formation of numerous hydrogen bonds with the nitroxide moiety. The coordination of the nitroxides by terminal cobalt ions is impossible because this would lead to the impermissible spatial overlap of the atoms of the tetradecanuclear moiety and the nitroxide. The spatial characteristics of only NIT-H containing the H atom in position 2 of the 2-imidazoline ring are suitable for the direct coordination of the nitroxide, which made it possible to synthesize the complex [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(H₂O)₄(NIT-H)₂]·4HPiv·2H₂O.     

New cage-like metallasiloxane containing Fe<Superscript>III</Superscript> ions in different coordination spheres

The first cage-like ferrophenyl siloxane containing Fe^III ions in different coordination spheres (four iron ions have a trigonal-bipyramidal coordination and two iron ions have a distorted octahedral coordination) was synthesized by the exchange reaction of sodium phenylsilanolate with Fe^III chloride. An exotic lantern-like structure is formed with the involvement of two metal oxide fragments Fe—O—Fe. The structure of this compound was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 522–524, March, 2007.     

Enhancing single-molecule magnet behavior of linear Co<Superscript>II</Superscript>-Dy<Superscript>III</Superscript>Co<Superscript>II</Superscript> complex by introducing bulky diamagnetic moiety

Single-molecule magnets (SMMs) are regarded as promising candidates for ultrahigh-density storage, quantum information processing and molecular spintronics. It is a crucial challenge for chemists to modulate magnetic dynamics of SMMs. Here, we successfully synthesized two 3d-4f polynuclear compounds [Co₂Dy(TTTT^Cl)₂(MeOH)]NO₃·3MeOH (1) and [Co₂Dy(TTTT^Cl)₂ (MeOH)][Co(HTTTT^Cl)](NO₃)₂·2.5MeOH·2H₂O (2), where H₃TTTT^Cl=2,2′,2′′-(((nitrilotris(ethane-2,1-diyl)) tris(azanediyl)) tris(methylene))tris-(4-chlorophenol). On applying the approach by co-crystallization of bulky diamagnetic moiety, the effective energy barrier enhances from 401 K (1) to 536 K (2), which are both among the highest d-f heterometallic SMMs.