NiII Complexes Research Articles

Light‐Promoted C–N Coupling of Aryl Halides with Nitroarenes

AbstractA photochemical C–N coupling of aryl halides with nitroarenes is demonstrated for the first time. Catalyzed by a NiII complex in the absence of any external photosensitizer, readily available nitroarenes undergo coupling with a variety of aryl halides, providing a step‐economic extension to the widely used Buchwald–Hartwig C–N coupling reaction. The method tolerates coupling partners with steric‐congestion and functional groups sensitive to bases and nucleophiles. Mechanistic studies suggest that the reaction proceeds via the addition of an aryl radical, generated from a NiI/NiIII cycle, to a nitrosoarene intermediate.

Synthesis, characterization, structure determination from powder X-ray diffraction data, and biological activity of azo dye of 3-aminopyridine and its complexes of Ni(II) and Cu(II)

In the present work azo dye ligand of 3-aminopyridine (L) and its complexes of NiII and CuII were synthesized, characterized and evaluated for antibacterial and antifungal activities in vitro. The L ligand was synthesized by reacting diazonium ion of 3-aminopyridine with 1-naphthole in presence of sodium acetate. The ligand (L) and its complexes were characterized by elemental analysis (CHN), magnetic susceptibility, molar conductivity, UV-Vis spectra, and infrared technique. The (L) azo dye exhibited high sensing for the pH changes. The color of L dye changed from red in basic medium to yellow color in acidic medium. The data of CHN, UV-Vis and magnetic susceptibility indicate that the complexes [Ni(L)2Cl2] and [Cu(L)2Cl2] are tetrahedral. The complexes of Ni(II) and Cu(II) exhibited potent activity against growth of Staphylococcus aureus and Escherichia Coli as well as against Penicillium Sp. And Aspergillus niger. Under visible irradiation (395 nm), the (L) azo dye of pyridine exhibited a significant change in the spectra under irradiation.
 
 KEY WORDS: Pyridine, Photoisomerization, Pyridylazo, Biological activity, pH sensor
 
 Bull. Chem. Soc. Ethiop. 2020, 34(3), 523-532.
 DOI: https://dx.doi.org/10.4314/bcse.v34i3.8

Ferro- vs. antiferromagnetic exchange between two Ni(II) ions in a series of Schiff base heterometallic complexes: what makes the difference?

Three new NiII/ZnII heterometallics, [NiZnL'2(OMe)Cl]2 (1), [NiZnL''(Dea)Cl]2·2DMF (2) and [Ni2(H3L''')2(o-Van)(MeOH)2]Cl·[ZnCl2(H4L''')(MeOH)]·2MeOH (3), containing three-dentate Schiff bases as well as methanol or diethanolamine (H2Dea) or o-vanillin (o-VanH), all deprotonated, as bridging ligands were synthesized and structurally characterized. The Schiff base ligands were produced in situ from o-VanH and CH3NH2 (HL'), or NH2OH (HL"), or 2-amino-2-hydroxymethyl-propane-1,3-diol (H4L'''); a zerovalent metal (Ni and Zn in 1, Zn only in 2 and 3) was employed as a source of metal ions. The first two complexes are dimers with a Ni2Zn2O6 central core, while the third compound is a novel heterometallic cocrystal salt solvate built of a neutral zwitterionic ZnII Schiff base complex and of ionic salt containing dinuclear NiII complex cations. The crystal structures contain either centrosymmetric (1 and 2) or non-symmetric di-nickel fragment (3) with NiNi distances in the range 3.146-3.33 Å. The exchange coupling is antiferromagnetic for 1, J = 7.7 cm-1, and ferromagnetic for 2, J = -6.5 cm-1 (using the exchange Hamiltonian in a form Ĥ = Jŝ1ŝ2). The exchange interactions in 1 and 2 are comparable to the zero-field splitting (ZFS). High-field EPR revealed moderate magnetic anisotropy of opposite signs: D = 2.27 cm-1, E = 0.243 cm-1 (1) and D = -4.491 cm-1, E = -0.684 cm-1 (2). Compound 3 stands alone with very weak ferromagnetism (J = -0.6 cm-1) and much stronger magnetic anisotropy with D = -11.398 cm-1 and E = -1.151 cm-1. Attempts to calculate theoretically the exchange coupling (using the DFT "broken symmetry" method) and ZFS parameters (with the ab initio CASSCF method) were successful in predicting the trends of J and D among the three complexes, while the quantitative results were less good for 1 and 3.

Studies on the Spectral, Anti-Bacterial and Anti-Fungal Activities of 1-((Dicyclohexylamino) (Phenyl) Methyl) Pyrrolidine-2, 5-Dione and Few of its Metal Complexes

1-((dicyclohexylamino)(phenyl)methyl) pyrrolidine-2,5-dione (SDB) has been synthesized as a result of succinimide, benzaldehyde and dicyclohexylamine Mannich base condensation and its CoII, NiII and CuII complexes were prepared. The structure of the Mannich Base ligand (SDB) was elucidated on the basis of FT-IR, 1H NMR, 13C NMR and Mass spectral studies. The monomeric and non-electrolytic nature of the metal complexes is evidenced by their magnetic susceptibility and low conductance data studies. Spectral tests, mainly FT-IR studies as well as elemental analysis, were carried out to verify the structures of the newly synthesized compounds. All the metal complexes possess a six-coordinate geometry. The synthesized ligand and its metal complexes have been tested against Gram-positive strains (Staphylococcus aureus and Micrococcus luteus), Gram-negative strains (Escherichia coli and Pseudomonas aeruginosa) and fungal strains (Aspergillus niger and Aspergillus fumigates) for their in vitro anti-bacterial and anti-fungal activities. Preliminary antimicrobial studies of the ligand and their metal complexes have also been carried out in order to understand the toxic effect of ligands and metal complexes against the selective microbes. The results showed that the metal chelates of the ligands showed higher antimicrobial activities than the free ligand SDB and CoII complexes possess higher activity than the other metal complexes.

Sterically Demanding 8-(Diphenylphosphino)quinoline Complexes of Group 10 Metal(II): Synthesis, Crystal Structures, and Properties in Solution.

Several series of platinum(II), palladium(II), and nickel(II) complexes bearing 8-(diphenylphosphino)quinoline (PQH) or its 2-methyl or 2-phenyl derivatives (PQMe or PQPh) were synthesized, and their crystal structures and behaviors in solution were investigated. Most of the complexes [M(PQR)2]X2 (MII = PtII, PdII, or NiII; R = H, Me or Ph; X = monoanionic ions) characterized in this study have an approximately square-planar coordination geometry with two bidentate P,N-chelating or monodentate P-donating quinolylphosphine ligands in the cis(P,P) configuration. A large steric requirement from the Me or Ph substituent introduced at the 2-position of the quinoline ring gives the resulting complexes severe distortion. The PtII and PdII complex cations maintained the square-planar coordination geometry, but the MII center was displaced from the chelating ligand plane. This bending of the chelate coordination makes the M-N(quinoline) bond weaker, as demonstrated by the longer M-N bonds. In accord with the bond weakening, the partial dissociation of the PQH or PQMe chelates by substitution with halide anions were observed using UV-vis spectroscopy and X-ray crystallography. In contrast, the PQPh complexes were stable in solution toward the addition of halide anions; the intramolecular π-π stacking interaction between the coordinating quinolyl and the 2-substituted phenyl rings protects the MII center from nucleophilic attack. In the corresponding NiII complexes, the steric congestion arising from the mutually cis-positioned PQR ligands resulted in a large tetrahedral distortion around the NiII center. However, the intramolecular π-π stacking interaction was still effective in the PQPh complex, and this interaction can explain some unusual robustness and electrochemical properties of the NiII-PQPh complex.

Selective Transformation of Nickel‐Bound Formate to CO or C−C Coupling Products Triggered by Deprotonation and Steered by Alkali‐Metal Ions

AbstractThe complexes [LtBuNi(OCO‐κ2O,C)]M3[N(SiMe3)2]2 (M=Li, Na, K), synthesized by deprotonation of a nickel formate complex [LtBuNiOOCH] with the corresponding amides M[N(SiMe3)2], feature a NiII−CO22− core surrounded by Lewis‐acidic cations (M+) and the influence of the latter on the behavior and reactivity was studied. The results point to a decrease of CO2 activation within the series Li, Na, and K, which is also reflected in the reactivity with Me3SiOTf leading to the liberation of CO and formation of a Ni−OSiMe3 complex. Furthermore, in case of K+, the {[K3[N(SiMe3)2]2}+ shell around the Ni−CO22− entity was shown to have a large impact on its stabilization and behavior. If the number of K[N(SiMe3)2] equivalents used in the reaction with [LtBuNiOOCH] is decreased from 3 to 0.5, the deprotonated part of the precursor enters a complex reaction sequence with formation of [LtBuNiI(μ‐OOCH)NiILtBu]K and [LtBuNi(C2O4)NiLtBu]. The same reaction at higher concentrations additionally led to the formation of a unique hexanuclear NiII complex containing both oxalate and mesoxalate ([O2C‐CO2‐CO2]4−) ligands.

Selective Transformation of Nickel-Bound Formate to CO or C-C Coupling Products Triggered by Deprotonation and Steered by Alkali-Metal Ions.

The complexes [LtBuNi(OCO‐κ 2 O,C)]M3[N(SiMe3)2]2 (M=Li, Na, K), synthesized by deprotonation of a nickel formate complex [LtBuNiOOCH] with the corresponding amides M[N(SiMe3)2], feature a NiII−CO2 2− core surrounded by Lewis‐acidic cations (M+) and the influence of the latter on the behavior and reactivity was studied. The results point to a decrease of CO2 activation within the series Li, Na, and K, which is also reflected in the reactivity with Me3SiOTf leading to the liberation of CO and formation of a Ni−OSiMe3 complex. Furthermore, in case of K+, the {[K3[N(SiMe3)2]2}+ shell around the Ni−CO2 2− entity was shown to have a large impact on its stabilization and behavior. If the number of K[N(SiMe3)2] equivalents used in the reaction with [LtBuNiOOCH] is decreased from 3 to 0.5, the deprotonated part of the precursor enters a complex reaction sequence with formation of [LtBuNiI(μ‐OOCH)NiILtBu]K and [LtBuNi(C2O4)NiLtBu]. The same reaction at higher concentrations additionally led to the formation of a unique hexanuclear NiII complex containing both oxalate and mesoxalate ([O2C‐CO2‐CO2]4−) ligands.

Helical water-soluble NiII complexes with pyridoxal ligand derivatives: Structural evaluation and interaction with biomacromolecules

This article deals with the synthesis of Schiff-based bis-azomethine-based ligands derived from pyridoxal and aliphatic dihydrazides and the synthesis of nickel(II) complexes C1–C4. The synthesized complexes had their structures elucidated by monocrystal X-ray diffraction and were characterized by vibrational and absorption spectroscopy. The synthesized ligands have characteristics that allow the formation of self-assembly processes, thus, the flexibility or rigidity of the coordination of organic molecules added to the orbitals of the NiII cation leads to the formation of helical complexes with double helix and a dinucler nickel(II) complex. Moreover, compounds was their interactions with CT-DNA and HSA absorption and emission analysis and molecular docking calculations.

Syntheses, crystal structures and antimicrobial activities of polynuclear CoII, NiII and ZnII complexes derived from the N,N'-bis(4-fluorosalicylidene)-1,3-propanediamine Schiff base

A series of new cobalt(II), nickel(II) and zinc(II) complexes [Co{CoL(CH3COO)}2] (1), [Ni{NiL(CH3COO)}2] (2), [Zn{ZnL(CH3COO)}2] (3), [Ni2ClL(μ2-1,5-dca)]n (4), [Zn2BrL(μ1,1-N3)]2 (5), [Zn2ClL(μ1,1-N3)]2 (6), where L is the doubly deprotonated form of N,N'-bis(4-fluorosalicylidene)-1,3-propanediamine (H2L), dca is dicyanoamide, were synthesized and characterized by elemental analyses, infrared and electronic spectroscopy, and single crystal X-ray determination. Complexes 1, 2 and 3 are isostructural acetato- and phenolato-bridged trinuclear compounds. Complex 4 is a μ2-1,5-dca and phenolato-bridged polymeric compound. Complexes 5 and 6 are isostructural end-on azido- and phenolato-bridged tetranuclear compounds. The compounds were evaluated for their antibacterial (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas fluorescens) and antifungal (Candida albicans and Aspergillus niger) activities by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) method.

High Enzyme Activity of a Binuclear Nickel Complex Formed with the Binding Loops of the NiSOD Enzyme**

Detailed equilibrium, spectroscopic and superoxide dismutase (SOD) activity studies are reported on a nickel complex formed with a new metallopeptide bearing two nickel binding loops of NiSOD. The metallopeptide exhibits unique nickel binding ability and the binuclear complex is a major species with 2×(NH2,Namide,S−,S−) donor set even in an equimolar solution of the metal ion and the ligand. Nickel(III) species were generated by oxidizing the NiII complexes with KO2 and the coordination modes were identified by EPR spectroscopy. The binuclear complex formed with the binding motifs exhibits superior SOD activity, in this respect it is an excellent model of the native NiSOD enzyme. A detailed kinetic model is postulated that incorporates spontaneous decomposition of the superoxide ion, the dismutation cycle and fast redox degradation of the binuclear complex. The latter process leads to the elimination of the SOD activity. A unique feature of this system is that the NiIII form of the catalyst rapidly accumulates in the dismutation cycle and simultaneously the NiII form becomes a minor species.

Comparison of mol-ecular structures of cis-bis-[8-(di-methyl-phosphan-yl)quinoline]-nickel(II) and -platinum(II) complex cations.

The crystal structures of the complexes (SP-4-2)-cis-bis-[8-(di-methyl-phosphan-yl)quinoline-κ2 N,P]nickel(II) bis-(perchlorate) nitro-methane monosolvate, [Ni(C11H12NP)2](ClO4)2·CH3NO2 (1), and (SP-4-2)-cis-bis-[8-(di-methyl-phos-phan-yl)quinoline-κ2 N,P]platinum(II) bis-(tetra-fluoro-borate) aceto-nitrile monosolvate, [Pt(C11H12NP)2](BF4)2·C2H3N (2), are reported. In both complex cations, two phosphanyl-quinolines act as bidentate P,N-donating chelate ligands and form the mutually cis configuration in the square-planar coordination geometry. The strong trans influence of the di-methyl-phosphanyl donor group is confirmed by the Ni-N bond lengths in 1, 1.970 (2) and 1.982 (2) Å and, the Pt-N bond lengths of 2, 2.123 (4) and 2.132 (4) Å, which are relatively long as compared to those in the analogous 8-(di-phenyl-phosphan-yl)quinoline complexes. Mutually cis-positioned quinoline donor groups would give a severe steric hindrance between their ortho-H atoms. In order to reduce such a steric congestion, the NiII complex in 1 shows a tetra-hedral distortion of the coordination geometry, as parameterized by τ4 = 0.199 (1)°, while the PtII complex in 2 exhibits a typical square-planar coordination geometry [τ4 = 0.014 (1)°] with a large bending deformation of the ideally planar Me2Pqn chelate planes. In the crystal structure of 2, three F atoms of one of the BF4 - anions are disordered over two sets of positions with refined occupancies of 0.573 (10) and 0.427 (10).

Influence of structural variation of salamo‐based ligand on supramolecular architectures, Hirshfeld analyses, and fluorescence properties of new tetranuclear NiII complexes

Two new tetranuclear NiII complexes, [Ni4(L1)2(N3)4(MeOH)2]·CH3COCH3 (1) and [Ni4(L2)2(N3)4(MeOH)2]·4CH3COCH3 (2), were synthesized using NiCl2·6H2O, NaN3, and asymmetric salamo‐based ligands H2L1 and H2L2, respectively. The structural characterization was made by elemental analyses, infrared (IR) and ultraviolet‐visible (UV‐vis) spectra, and X‐ray diffraction analyses. The results of X‐ray diffraction analyses show that the NiII atoms in complexes 1 and 2 are distorted octahedral geometries. Interestingly, the degree of distortion of the ligands in complexes 1 and 2 is different, which indicates that the interaction of NiII ions on different ligands is different. Meanwhile, the investigation of molecular packing by employing the Hirshfeld surface analysis exhibits that the percentages of C–H/H–C, O–H/H–O, and H–H/H–H contacts of the complex 1 (or 2) are calculated to be 17.7%, 7.9%, and 53.7% (or 18.8%, 13.8%, and 52.5%), respectively, where the H–H/H–H contacts have the characteristics of strong contacts whereas the O–H/H–O hydrogen bonds are considerably weak, and the studies on fluorescence properties further confirm the NiII atoms have different binding abilities to the different ligands.

Role of Coordination Number and Geometry in Controlling the Magnetic Anisotropy in FeII, CoII, and NiII Single‐Ion Magnets

Since the last decade, the focus in the area of single-molecule magnets (SMMs) has been shifting constructively towards the development of single-ion magnets (SIMs) based on transition metals and lanthanides. Although ground-breaking results have been witnessed for DyIII -based SIMs, significant results have also been obtained for some mononuclear transition metal SIMs. Among others, studies based on CoII ion are very prominent as they often exhibit high magnetic anisotropy or zero-field splitting parameters and offer a large barrier height for magnetisation reversal. Although CoII possibly holds the record for having the largest number of zero-field SIMs known for any transition metal ion, controlling the magnetic anisotropy in these systems are is still a challenge. In addition to the modern spectroscopic techniques, theoretical studies, especially ab initio CASSCF/NEVPT2 approaches, have been used to uncover the electronic structure of various CoII SIMs. In this article, with some selected examples, the aim is to showcase how varying the coordination number from two to eight, and the geometry around the CoII centre alters the magnetic anisotropy. This offers some design principles for the experimentalists to target new generation SIMs based on the CoII ion. Additionally, some important FeII /FeIII and NiII complexes exhibiting large magnetic anisotropy and SIM properties are also discussed.

Synthesis, Structure, and Magnetic Properties of Linear Trinuclear CuII and NiII Complexes of Porphyrin Analogues Embedded with Binaphthol Units

A porphyrin analogue embedded with (S)-1,1′-bi-2-naphthol units was synthesized without reducing optical purity of the original binaphthol unit. This new macrocyclic ligand provides the hexaanionic N4O4 coordination environment that enables a linear array of three metal ions. That is, it provides the square planar O4 donor set for the central metal site and the distorted square planar N2O2 donor set for the terminal metal sites. In fact, a CuII3 complex with a Cu(1)–Cu(2) distance of 2.910 Å, a Cu(1)–Cu(2)–Cu(1′) angle of 174.7°, and a very planar Cu2O2 diamond core was obtained. The variable-temperature 1H-NMR study of the CuII3 complex showed increasing paramagnetic shifts for the naphthyl protons as temperature increased, which suggests strong antiferromagnetic coupling of CuII ions. The temperature dependence of the magnetic susceptibility indicated antiferromagnetic coupling both for the CuII3 complex (J = −434 cm−1) and for the NiII3 complex (J = −49 cm−1). The linear (L)M(µ-OR)2M(µ-OR)2M(L) core in a rigid macrocycle cavity made of aromatic components provides robust metal complexes that undergo reversible ligation at the apical sites of the central metal.

Dinickel(II) complexes with pyridine-substituted bis(triazolylmethyl)amine ligands: Structures and magnetic properties

The coordination behavior of the newly prepared bis(triazolylmethyl)amine-type ligands bis[(1-R-1H-1,2,3-triazol-4-yl)methyl]amine [R = CH2Ph (L1), CH2-2-pyridyl (L2)] and 1-(1-benzyl-1H-1,2,3-triazol-4-yl)-N-((1-(pyridin-2-ylmethyl)-1H-1,2,3-triazol-4-yl)methyl)methanamine (L3) toward NiII ions was investigated. The reaction of NiCl2·6H2O with the benzyl-substituted bis(triazolylmethyl)amine ligand L1 afforded the mononuclear NiII complex Ni(L1)2Cl2 (1). On the other hand, dinuclear NiII complexes, [Ni2(L2)2Cl2]Cl2 (2) and [Ni2(L3)2Cl2]Cl2 (3), were obtained when NiCl2·6H2O was reacted with the pyridine-substituted ligands L2 and L3, respectively. Single-crystal X-ray analysis revealed that the two octahedral NiII centers in 2 and 3 are bridged by two triazole rings through nitrogen donors to generate the dinuclear complexes with a syn arrangement. Meanwhile, treatment of Ni(NO3)2 with L2 afforded the related dinickel(II) complex [Ni2(L2)2(NO3)2](NO3)2 (2′), in which two non-bridging triazole rings and two nitrate ions are positioned in an anti arrangement. Complexes 2 and 3 showed antiferromagnetic coupling between the two NiII centers (S = 1), with J values following the trend: 2′ > 2 > 3.

Nickel(II) complexes based on L-amino-acid-derived ligands: synthesis, characterization and study of the role of the supramolecular structure in carbon dioxide capture.

The formation of the symmetrical μ3-carbonate-bridged self-assembled trinuclear NiII complex Na2{[Ni(LO)2(H2O)]3(μ3-CO3)} (LO is the carboxylate anion of a L-tyrosine derivative), involves atmospheric CO2 uptake. The asymmetric unit of the complex comprises an octahedral coordination for the NiII with two L-tyrosine-based ligands, a water molecule and one O atom of the carbonate bridge. The Ni3-μ3-CO3 core in this compound is the first reported of this kind according to the Cambridge Structural Database (CSD). The supramolecular structure is mainly sustained by hydrogen bonds developed by the phenolic functionality of the L-tyrosine moiety of one ligand and the carboxylate group of a neighbouring ligand. The crystal packing is then characterized by three interpenetrated supramolecular helices associated with a diastereoisomer of the type R-supP, which is essential for the assembly process. Magnetic susceptibility and magnetization data support weak ferromagnetic exchange interactions within the novel Ni3-μ3-CO3 core. The NiII complex obtained under the same synthetic conditions but using the analogous ligand derived from the amino acid L-phenylalanine instead of L-tyrosine gives rise to to a mononuclear octahedral system. The results obtained for the different complexes demonstrate the role of the supramolecular structure regarding the CO2 uptake property for these NiII-amino-acid-based systems.

Dinickel(Ii) Complexes with Pyridine-Substituted Bis(Triazolylmethyl)Amine Ligands: Structures and Magnetic Properties

Coordination behavior of newly prepared bis(triazolylmethyl)amine-type ligands, bis[(1-R-1H-1,2,3-triazol-4-yl)methyl]amine [R = CH2Ph (L1), CH2-2-pyridyl (L2)] and 1-(1-Benzyl-1H-1,2,3-triazol-4-yl)-N-((1-(pyridin-2-ylmethyl)-1H-1,2,3-triazol-4-yl)methyl)methanamine (L3), toward NiII ions was investigated. The reaction of NiCl2·6H2O with the benzyl-substituted bis(triazolylmethyl)amine ligand L1 afforded the mononuclear NiII complex Ni(L1)2Cl2 (1). On the other hand, the dinuclear NiII complexes, [Ni2(L2)2Cl2]Cl2 (2) and [Ni2(L3)2Cl2]Cl2 (3), were obtained when NiCl2·6H2O was reacted with the pyridine-substituted ligands, L2 and L3, respectively. Single-crystal X-ray analysis revealed that two octahedral NiII centers in 2 and 3 are bridged by two triazole rings through nitrogen donors to generate the dinuclear complexes with a syn arrangement. Meanwhile, treatment of Ni(NO3)2 with L2 afforded the related dinickel(II) complex, [Ni2(L2)2(NO3)2](NO3)2 (2'), in which two non-bridging triazole rings and two nitrate ions were positioned in an anti arrangement. Complexes 2 and 3 showed the antiferromagnetic coupling between two NiII centers (S = 1), with J values following the trend: 2' > 2 > 3.

Metal Complexes of 5,15‐Porphyrinquinones: Systematic Study of Crystal Structure, Electronic Structure, and Lewis Acidity

We conducted the first systematic study on the synthesis, structure, and properties of various divalent metal complexes (NiII, CuII, ZnII, PdII, PtII, and PbII) of 5,15‐porphyrinquinone (PQ, a quinone compound of porphyrin) for diversifying the chemistry of traditional quinone‐metal complexes. Similar to electron‐accepting nature of PQ, the metal complexes studied here also exhibit it. NiII, PdII, and PtII complexes favor face‐to‐face stacked structures in the crystals, thus inducing effective PtII–PtII interaction, which has not been observed in the porphyrin analogues to date. Ultraviolet‐visible (UV/Vis) absorption spectra of the metal complexes vary widely depending on the metal ion and owing to the effective d(metal)–π(PQ) coupling in their molecular orbitals. Quantitative analyses of the axial ligation on the central metal ions (NiII and CuII) revealed significantly larger binding constants than those of the porphyrin analogues, indicating significant enhancement of their Lewis acidities due to the strong electron‐withdrawing nature of PQ.

Metal ion directed template synthesis using 2-acetyl-1,3-indandione and ethylenediamine: steric and electronic restrictions

A NiII-directed template synthesis using 2-acetyl-1,3-indandione and ethylenediamine results in formation of octahedral NiII complex, whose crystal structure has been resolved using single crystal X-ray diffraction. The structure indicates that only exocyclic enolic oxygen atom of the triketone takes part in the condensation with ethylenediamine. Quantum chemical calculations reveal insights into the observed reactivity of an initial NiII complex of 2-acetyl-1,3-indandione with ethylenediamine and point out steric effects as the main restriction for a complete cyclization into a tetraaza macrocycle.

Template Synthesis, Characterization, Antioxidant Effects, DNA Cleavage and Antimicrobial Studies of ZnII, NiII, MnII, CuII and CoII Complexes Containing Pyridazinone Moiety

Bu çalışmada template metodu ile o-aminofenol, 5-benzoil-4-hidroksi-2-metil-6-fenil-2Hpiridazin-3-on ve ZnII, NiII, MnII, CuII ve CoII metal tuzlarından türeyen beş yeni Schiff baz kompleksi sentezlenmiştir. Metal kompleksler elemental analiz, FT-IR, UV-Vis, kütle ve manyetik duyarlılık ile karakterize edilmiştir. Sentezlenen bileşiklerin antioksidan etkileri, DNA bölünmesi ve antimikrobiyal çalışmaları yapılmıştır. DPPH süpürme ve metal şelatlama aktivitesinin konsantrasyona bağlı olarak arttığı bulunmuştur. En yüksek DPPH aktivitesi ve demir iyon şelatlama aktivitesi Zn bileşiğinden elde edildi. Sentezlenen tüm bileşikler, Mn>Zn=Ni=Co>Cu sırasına gore E. hirae’ye karşı antibakteriyal aktivite sergilerken, sadece Ni bileşiği test edilen tüm organizmalara karşı, özellikle de L. pneumophila subsp. pneumophila’ya 13 mm’ye eşit inhibisyon zon değerinde antimikrobiyal aktivite göstermiştir.