Radiation Polymerization of 4-(Acryloylamido)benzonitrile: Zinc and Copper Complexes

Summary. The new polymer containing cyano groups was synthesized by γ-irradiation. The oximated polymer was prepared using hydroxylamine hydrochloride in basic medium. The characterization of monomer, polymer, and oximated ones was confirmed by infrared and nuclear magnetic resonance spectroscopy. The complex formation of the amidoxime salt towards Zn^II, Cu^II, and Zn^II/Cu^II mixture in aqueous solution was studied by atomic absorption spectroscopy, energy dispersive spectroscopy, and electron spin resonance spectrometry. The significant binding capacity of these metal ions revealed its selectivity to Zinc(II) ion. The thermal stability of polymers and complexed ones was investigated using thermogravimetry analysis. The change in their morphology was observed by scanning electron microscopy (SEM).     

Combined EXAFS and DFT Structure Calculations Provide Structural Insights into the 1:1 Multi‐Histidine Complexes of CuII,CuI, and ZnII with the Tandem Octarepeats of the Mammalian Prion Protein

The metal‐coordinating properties of the prion protein (PrP) have been the subject of intense focus and debate since the first reports of its interaction with copper just before the turn of the century. The picture of metal coordination to PrP has been improved and refined over the past decade, but structural details of the various metal coordination modes have not been fully elucidated in some cases. In the present study, we have employed X‐ray absorption near‐edge spectroscopy as well as extended X‐ray absorption fine structure (EXAFS) spectroscopy to structurally characterize the dominant 1:1 coordination modes for Cu^II, Cu^I, and Zn^II with an N‐terminal fragment of PrP. The PrP fragment corresponds to four tandem repeats representative of the mammalian octarepeat domain, designated as OR₄, which is also the most studied PrP fragment for metal interactions, making our findings applicable to a large body of previous work. Density functional theory (DFT) calculations have provided additional structural and thermodynamic data, and candidate structures have been used to inform EXAFS data analysis. The optimized geometries from DFT calculations have been used to identify potential coordination complexes for multi‐histidine coordination of Cu^II, Cu^I, and Zn^II in an aqueous medium, modelled using 4‐methylimidazole to represent the histidine side chain. Through a combination of in silico coordination chemistry as well as rigorous EXAFS curve‐fitting, using full multiple scattering on candidate structures derived from DFT calculations, we have characterized the predominant coordination modes for the 1:1 complexes of Cu^II, Cu^I, and Zn^II with the OR₄ peptide at pH 7.4 at atomic resolution, which are best represented as square‐planar [Cu^II(His)₄]²⁺, digonal [Cu^I(His)₂]⁺, and tetrahedral [Zn^II(His)₃(OH₂)]²⁺, respectively.     

Bi- and tetranuclear ligational deeds of a polyaza macrocycle having four diazine (N2) bridging components headed for CoII, NiII, CuII and ZnII ions: An emphasis on electrochemistry of non-innocent ligand system

Novel bi- and tetranuclear Co^II, Ni^II, Cu^II and Zn^II complexes having diazine bridging units have been prepared and characterised on the basis of analytical and spectroscopic techniques. With the help of electronic spectra and magnetic moment measurements, it is predicted that the Co^II and Ni^II complexes have octahedral geometry while Cu^II and Zn^II complexes found to be square pyramidal. Present Zn^II and Cu^II complexes are binuclear in nature, where as Co^II and Ni^II complexes are tetranuclear with feeble antiferromagnetic exchange interactions. UV–visible spectral studies, in the range 275–425 nm, evidence the significant blue shift in π → π* transition which provide the ease of stabilization of bonding molecular orbitals in the complexes. All complexes are monomeric in nature. Ligand and all complexes were found to be electrochemically active compounds. One electron transfer process is observed in ligand similarly, there is no significant change in the cyclic voltammograms of Co^II and Zn^II complexes, while Cu^II and Ni^II complexes show one and two electron transfer redox behaviours, respectively in the present macrocyclic ligand field.     

Synthesis and spectroscopic study of the d-metal complexes with new octa(benzo-15-crown-5)-substituted phthalocyanine

Octa(benzo-15-crown-5)-substituted phthalocyanine and its complexes with d-metals (Ni^II, Co^II, Cu^II, Zn^II, and Cd^II) have been synthesized for the first time. The compounds were studied by UV—Vis spectroscopy, MALDI-TOF mass spectrometry, NMR, ESR, IR spectroscopy, and Raman spectroscopy. The dependence of the spectral characteristics of the studied compounds on the ion radius of the complexing agent was demonstrated. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1439–1447, July, 2008.     

Metal(II) Ion Complexes with 5‐(Pyrazin‐2‐yl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione; Synthesis,Structural Characterization,Acid‐base,and Complexing Properties in Solution

The study reports the synthesis of complexes Co(HL)Cl₂ ( 1 ), Ni(HL)Cl₂ ( 2 ), Cu(HL)Cl₂ ( 3 ), and Zn(HL)₃Cl₂ ( 4 ) with the title ligand, 5‐(pyrazin‐2‐yl)‐1,2,4‐triazole‐5‐thione (HL), and their characterization by elemental analyses, ESI‐MS (m/z), FT‐IR and UV/Vis spectroscopy, as well as EPR in the case of the Cu^II complex. The comparative analysis of IR spectra of the metal ion complexes with HL and HL alone indicated that the metal ions in 1 , 2 , and 3 are chelated by two nitrogen atoms, N(4) of pyrazine and N(5) of triazole in the thiol tautomeric form, whereas the Zn^II ion in 4 is coordinated by the non‐protonated N(2) nitrogen atom of triazole in the thione form. pH potentiometry and UV/Vis spectroscopy were used to examine Co^II, Ni^II, and Zn^II complexes in 10/90 (v/v) DMSO/water solution, whereas the Cu^II complex was examined in 40/60 (v/v) DMSO/water solution. Monodeprotonation of the thione triazole in solution enables the formation of the L:M = 1:1 species with Co^II, Ni^II and Zn^II, the 2:1 species with Co^II and Zn^II, and the 3:1 species with Zn^II. A distorted tetrahedral arrangement of the Cu^II complex was suggested on the basis of EPR and Vis/NIR spectra.     

Magnetic and spectroscopic studies of bimetalliciso-propoxides of later 3d metals with aluminium

Summary The structures of the volatile bimetalliciso-propoxides of later 3d metals with the general formula, [M{Al(OPr-i)4}_n] where M=Cr^III, Mn^II, Fe^III, Co^II, Ni^II and Cu^II have been investigated by visible reflectance and electron spin resonance spectroscopy as well as magnetic measurements.     

Metal chelates of thiazole-2-ylthiourea

Summary The formation constants of 1-phenyl-3-thiazole-2-ylthiourea complexes with some bivalent metal ions (Cu^II, Ni^II, Zn^II and Mn^II) have been determined in 75% EtOH–H₂O. Complexes of Cu^II, Ni^II, Zn^II, Hg^II and Pd^II have been isolated and characterized by conductance, i.r., electronic spectra and magnetic measurements. The ligand forms ML complexes with Cu^II and Hg^II and ML₂ with Ni^II, Zn^II and Pd^II, where L is the uninegatively charged bidentate ligand and binds through the ring nitrogen and thiocarbonyl sulphur atoms.     

A Schiff-base cross-linked supramolecular polymer containing diiminophenol compartments and its interaction with copper(II) ions

We report here the preparation of a Schiff-base linked organic polymer 1 based on linkages containing the potent supramolecular aggregator benzene-1,3,5-tricarboxamide, connected through 2,6-diiminophenol metal binding pockets into a cross-linked polymer. The morphological and physical properties of this material are studied using electron microscopy techniques, thermal analysis, NMR, fluorescence spectroscopy and gas adsorption studies. The interaction of the polymer 1 with Cu^II ions is then investigated by soaking the material with methanolic copper acetate solution, and studying the resulting aggregates using EDX microscopy and FTIR spectroscopy. A small-molecule model compound 2 is also prepared and crystallographically characterised to act as a spectroscopic comparison, providing strong evidence that 1 interacts with copper ions through a nucleation/seeding mechanism for the growth of microcrystalline copper acetate deposits, rather than via chemisorption of the copper ions within the diiminophenol binding pockets. Preliminary results suggest a similar mechanism for Co^II adsorption, while Zn^II ions exhibit a separate interaction mode.     

Rational Approach Towards Designing Metallogels From a Urea‐Functionalized Pyridyl Dicarboxylate: Anti‐inflammatory,Anticancer, and Drug Delivery

A structural rationale was adopted to design a series of metallogels from a newly synthesized urea‐functionalized dicarboxylate ligand, namely, 5‐[3‐(pyridin‐3‐yl)ureido]isophthalic acid ( PUIA ), that produces metallogels upon reaction with various metal salts (Cu^II, Zn^II, Co^II, Cd^II, and Ni^II salts) at room temperature. The gels were characterized by dynamic rheology and transmission electron microscopy (TEM). The existence of a coordination bond in the gel state was probed by FTIR and ¹H NMR spectroscopy in a Zn^II metallogel (i.e., MG2 ). Single crystals isolated from the reaction mixture of PUIA and Co^II or Cd^II salts characterized by X‐ray diffraction revealed lattice inclusion of solvent molecules, which was in agreement with the hypothesis based on which the metallogels were designed. MG2 displayed anti‐inflammatory response (prostaglandin E₂ assay) in the macrophage cell line (RAW 264.7) and anticancer properties (cell migration assay) on a highly aggressive human breast cancer cell line (MDA‐MB‐231). The MG2 metallogel matrix could also be used to load and release (pH responsive) the anticancer drug doxorubicin. Fluorescence imaging of MDA‐MB‐231 cells treated with MG2 revealed that it was successfully internalized.     

Selective Coordination of Gallium(III), Zinc(II), and Copper(II) by an Asymmetric Dinucleating Ligand: A Model for Metallophosphatases

Complexation studies of the dinucleating ligand H₃L (H₃L=2‐{[bis(pyridin‐2‐ylmethyl)amino]methyl}‐6‐{[bis(6‐pivaloylamidopyridin‐2‐ylmethyl)amino]methyl}‐4‐methylphenol), with metal‐binding sites A and B, which both provide four donors to a metal ion; a tertiary amine; two pyridines (substituted with amide hydrogen‐bond donors in site B), and a bridging phenolate, with Zn^II, Cu^II, and Ga^III are reported. The titration of H₃L with the three metal ions in solution was monitored by NMR spectroscopy or EPR and UV/Vis/near‐IR spectroscopy, as well as by ESI‐MS to analyze the selectivity of the two metal‐ion sites A and B of this model ligand for metallophosphatases; the spectroscopic assignments are supported by X‐ray crystallography results. The first Zn^II ion coordinates to site A with unsubstituted pyridine donors and, upon addition of a second equivalent of Zn^II, this coordinates to the sterically less accessible site B. From a similar titration with Ga^III, it emerges that only a mononuclear complex is obtained, with the Ga^III center coordinated to site A. When one equivalent of Ga^III is reacted with the mononuclear Zn^II complex, Zn^II is forced by Ga^III to exchange the site; this results in a dinuclear complex with Ga^III in site A and Zn^II in site B. With Cu^II, two isomers are observed: one with and the other without a bridging phenolate; these differ significantly in their spectroscopic and magnetic properties.     

A Stable Organic π‐Radical of a Zinc(II)–Copper(I)–Zinc(II) Complex of Decaphyrin

A Zn^II‐Cu^I‐Zn^II heterotrimetal complex of decaphyrin was synthesized by stepwise metalations: metalation of a [46]decaphyrin with Zn^II ions to produce a 46π decaphyrin bis(Zn^II) complex and its subsequent metalation with Cu^II ion. In the second metalation step, it has been shown that Cu^II ion is reduced to a Cu^I ion in the complex and a dianionic bis(Zn^II) containing [46]decaphyrin ligand is oxidized to the corresponding monoanionic [45]decaphyrin ligand, indicating a non‐innocent nature of the decaphyrin ligand. Despite the radical nature, the heterotrimetal complex is fairly stable under ambient conditions and exhibits almost no intermolecular magnetic interaction, owing to extensive delocalization of an unpaired electron in the large π‐conjugated circuit of decaphyrin moiety.     

Synthesis,Spectral, Thermal Studies of Co(II), Ni(II), Cu(II) and Zn(II)‐arginato Complexes. Crystal Structure of Monoaquabis(arginato‐κO,κN)copper(II). [Cu(arg)2(H2O)].NaNO3

Transition metal complexes of arginine (using Co(II), Ni(II), Cu(II) and Zn(II) cations separately) were synthesized and characterized by FTIR, TG/DTA‐DrTG, UV‐Vis spectroscopy and elemental analysis methods. Cu(II)‐Arg complex crystals was found suitable for x‐ray diffraction studies. It was contained, one mole Cu^II and Na⁺ ions, two arginate ligands, one coordinated aqua ligand and one solvent NO₃^? group in the asymmetric unit. The principle coordination sites of metal atom have been occupied by two N atoms of arginate ligands, two carboxylate O atoms, while the apical site was occupied by one O atom for Cu^II cation and two O atoms for Co^II, Ni^II, Zn^II atoms of aqua ligands. Although Cu^II ion adopts a square pyramidal geometry of the structure. Co^II, Ni^II, Zn^II cations have octahedral due to coordination number of these metals. Neighbouring chains were linked together to form a three‐dimensional network via hydrogen‐bonding between coordinated water molecule, amino atoms and O atoms of the bridging carboxylate groups. Cu^II complex was crystallized in the monoclinic space group P2₁, a = 8.4407(5) Å, b = 12.0976(5) Å, c = 10.2448(6) Å, V = 1041.03(10) ų, Z = 2. Structures of the other metal complexes were similar to CuII complex, because of their spectroscopic studies have in agreement with each other. Copper complex has shown DNA like helix chain structure. Lastly, anti‐bacterial, anti‐microbial and anti‐fungal biological activities of complexes were investigated.     

The synthesis,spectroscopic and thermal study of oxamic acid compounds of some metal(II) ions

Summary The preparation of oxamic acid complexes of general formula M(H₂NCOCOO)₂·xH₂O (M = Mn^II, Co^II, Ni^II, Cu^II or Zn^II; x = 1 for Cu^II, x = 2 for the other metals) is reported. The i.r. and Raman spectra are discussed considering a trans-octahedral structure, formed by five-membered chelate rings with the amide oxygen and one carboxylic oxygen as donor atoms. The apical positions are occupied by water molecules. The thermal degradation process is very similar for the different complexes, first losing H₂O in one or different steps, then the fragments of the organic ligand to give the metal oxide as residue. The thermal degradation of the Cu^II and Zn^II compounds results in the formation of a new polymeric compound by deprotonation of the primary amide function in an endothermic process, the polymer further decomposes to form the metal oxide.     

Transition metal complexes of 5-chlorouracil

Summary Complexes of 5-chlorouracil (5-ClU) (1) with 3d metal ions were characterized by elemental analysis, various spectroscopic methods (i.r., u.v. spectroscopy) and magnetic susceptibility measurements. The spectral evidence suggest that 5-ClU behaves as bidentate ligand in Ni^II, Cu^II, Zn^II, and Cd^II compounds, coordinating through its one carbonyl oxygen and one nitrogen whereas with Mn^II and Co^II it coordinates through the carbonyl oxygen only. The insolubility of the new complexes in organic solvents suggests that these are polymeric except for the Co^II complex which is soluble in pyridine. There is probable OH bridging in the Mn^II and Cu^II complexes and the 5-ClU may bridge in the rest.     

Bispidines for Dual Imaging

The efficient transformation of the hexadentate bispidinol 1 into carbamate derivatives yields functional bispidines enabling convenient functionalization for targeted imaging. The BODIPY‐substituted bispidine 3 combines a coordination site for metal ions, such as radioactive ⁶⁴Cu^II, with a fluorescent unit. Product 3 was thoroughly characterized by standard analytical methods, single crystal X‐ray diffraction, radiolabeling, and photophysical analysis. The luminescence of ligand 3 was found to be strongly dependent on metal ion coordination: Cu^II quenches the BODIPY fluorescence, whereas Ni^II and Zn^II ions do not affect it. It follows that, in imaging applications with the positron emitter ⁶⁴Cu^II, residues of its origin from enriched ⁶⁴Ni and the decay products ⁶⁴Ni^II and ⁶⁴Zn^II, efficiently restore the fluorescence of the ligand. This allows for monitoring of the emitted radiation as well as the fluorescence signal. The stability of the ⁶⁴Cu^II? 3 complex is investigated by transmetalation experiments with Zn^II and Ni^II, using fluorescence and radioactivity detection, and the results confirm the high stability of ⁶⁴Cu^II? 3 . In addition, metal complexes of ligand 3 with the lanthanide ions Tb^III, Eu^III, and Nd^III are shown to exhibit emission of the BODIPY ligand and the lanthanide ion, thus enabling dual emission detection.     

Tailored Transition-Metal Coordination Environments in Imidazole-Modified DNA G-Quadruplexes

Two types of imidazole ligands were introduced both at the end of tetramolecular and into the loop region of unimolecular DNA G-quadruplexes. The modified oligonucleotides were shown to complex a range of different transition-metal cations including Ni^II, Cu^II, Zn^II and Co^II, as indicated by UV/Vis absorption spectroscopy and ion mobility mass spectrometry. Molecular dynamics simulations were performed to obtain structural insight into the investigated systems. Variation of ligand number and position in the loop region of unimolecular sequences derived from the human telomer region (htel) allows for a controlled design of distinct coordination environments with fine-tuned metal affinities. It is shown that Cu^II, which is typically square-planar coordinated, has a higher affinity for systems offering four ligands, whereas Ni^II prefers G-quadruplexes with six ligands. Likewise, the positioning of ligands in a square-planar versus tetrahedral fashion affects binding affinities of Cu^II and Zn^II cations, respectively. Gaining control over ligand arrangement patterns will spur the rational development of transition-metal-modified DNAzymes. Furthermore, this method is suited to combine different types of ligands, for example, those typically found in metalloenzymes, inside a single DNA architecture.     

Synthese,Struktur und EPR‐Untersuchungen von binuklearen Bis(N,N,N‴,N‴‐tetraisobutyl‐N′,N″‐isophthaloylbis(thioureato))‐Komplexen des CuII,NiII, ZnII,CdII und PdII

Synthesis, Structure and EPR Investigations of binuclear Bis(N,N,N?,N?‐tetraisobutyl‐N′,N″‐isophthaloylbis(thioureato)) Complexes of Cu^II, Ni^II, Zn^II, Cd^II and Pd^II The synthesis of binuclear Cu^II‐, Ni^II‐, Zn^II‐, Cd^II‐ and Pd^II‐complexes of the quadridentate ligand N,N,N?,N?‐tetraisobutyl‐N′,N″‐isophthaloylbis(thiourea) and the crystal structures of the Cu^II‐ and Ni^II‐complexes are reported. The Cu^II‐complex crystallizes in two polymorphic modifications: triclinic, (Z = 1) and monoclinic, P2₁/c (Z = 2). The Ni^II‐complex was found to be isostructural with the triclinic modification of the copper complex. The also prepared Pd^II‐, Zn^II‐ and Cd^II‐complexes could not be characterized by X‐ray analysis. However, EPR studies of diamagnetically diluted Cu^II/Pd^II‐ and Cu^II/Zn^II‐powders show axially‐symmetric g and A ^Cu tensors suggesting a nearly planar co‐ordination within the binuclear host complexes. Diamagnetically diluted Cu^II/Cd^II powder samples could not be prepared. In the EPR spectra of the pure binuclear Cu^II‐complex exchange‐coupled Cu^II‐Cu^II pairs were observed. According to the large Cu^II‐Cu^II distance of about 7,50Å a small fine structure parameter D = 26·10^?4 cm^?1 is observed; T‐dependent EPR measurements down to 5 K reveal small antiferromagnetic interactions for the Cu^II‐Cu^II dimer. Besides of the dimer in the EPR spectra the signals of a mononuclear Cu^II species are observed whose concentration is T‐dependent. This observation can be explained assuming an equilibrium between the binuclear Cu^II‐complex (Cu^II‐Cu^II pairs) and oligomeric complexes with “isolated” Cu^II ions.     

Versatility in the coordination behavior of a hexatopic compartmental Schiff-base ligand in the architecture of binuclear transition metal(II) complexes

Condensation of 1H-pyrazole-3,5-dicarboxylic hydrazide with 1H-indole-2,3-dione (isatin) yield the compartmental ligand, which is capable of encapsulating two transition metal ions namely Co^II, Ni^II, Cu^II, and Zn^II. The ligand is a binuclear hexadentate chelate with N₄O₂ donating sites. The pyrazole core provides the diazine fragment, which serves as an endogenous bridge between the two metal centers. In Co^II and Ni^II complexes, the ligand is in the imidol form and the subsequent coordination through the imidol oxygen. In other complexes, the lactonic oxygen takes part in ligation. All the complexes are non-electrolytes and soluble in DMSO, DMF, and acetonitrile. Spectral and magnetic studies along with analytical data suggest octahedral geometry for the Co^II and Ni^II complexes, whereas the Cu^II and Zn^II complexes are assigned square pyramidal geometry. The Cu^II and Ni^II complexes show one electron redox behavior and the rest are electrochemically inactive.     

The Coordination Chemistry of the Versatile Ligand Bis(2‐pyridylthio)methane

Bis(2‐pyridylthio)methane [bpytm, (pyS)₂CH₂] and complexes of this ligand with Zn^II, Hg^II, Cu^I, and Ag^I have been prepared and characterised by elemental analysis, by IR, Raman and ¹H and ¹³C NMR spectroscopy, and by X‐ray diffractometry. The ligand is N, N′‐didentate in the Zn^II complexes; N‐monodentate in one Hg^II complex and N, N′‐bis(monodentate) in the other; N‐mono‐N′, S‐didentate in the Cu^I complex; and N, S′‐bis(mono)‐N′, S‐didentate in the Ag^I complex. The structural parameters of the ligand in each coordination mode are compared with those of the free ligand and those of the triiodide salt of the protonated ligand.     

2-Aminoacetophenone-2-thenoylhydrazone complexes of bivalent 3d metal ions

Summary 2-Aminoacetophenone-2-thenoylhydrazone, Haath, C₄H₃SC(O)NHN=C(Me)C₆H₄NH₂-o, forms complexes with metal(II) salts of empirical compositions [VO(Haath)₂SO₄], [M(Haath)₂Cl₂] [M=Co^II, Ni^II, Cu^II or Zn^II] and [M(aath)₂] [M=V^IVO, Co^II, Ni^II, Cu^II or Zn^II] which have been characterized by elemental analyses, molar conductance, magnetic susceptibility, electronic, e.s.r., i.r. and n.m.r. (¹H and¹³C) spectral studies. X-ray and electron diffraction patterns have been obtained in order to elucidate the structure of the Cu^II complexes. Photoacoustic spectra of powder Ni^II complexes have been recorded and interpreted in the light of u.v./vis. spectra.