Synthesis, structure and magnetic property of a new mixed-valence copper(I/II) complex derived from 3,5-bis(pyridin-2-yl)-1,2,4-triazole

Di- and Tri-nuclear VIII and CrIII Complexes of Dipyridyltriazoles: Ligand Rearrangements, Mixed Valency and Ferromagnetic Coupling

The first dinuclear and trinuclear chromium(III) and dinuclear vanadium(III) complexes of N⁴-R-substituted-3,5-di(2-pyridyl)-1,2,4-triazole (Rdpt) ligands have been prepared by solvothermal complexations under inert atmospheres, and characterized. The reactions of Cr^III and V^III with adpt (R = amino) resulted in deamination of the ligand and yielded the dinuclear doubly-triazolate bridged complexes [V2III(dpt⁻)₂Cl₄] (1) and [Cr2III(dpt⁻)₂Cl₄] (2). In the case of the Cr^III complex 2 this bridging results in a rare example of ferromagnetic coupling for a dinuclear Cr^III compound. DFT studies confirm that in 2 the ferromagnetic coupling pathways dominate over the antiferromagnetic pathways, whereas in 1 the reverse occurs, consistent with the observed overall antiferromagnetic coupling in that case. It was also found that the use of different additives in the reaction allows the nuclearity of the Cr^III product to be manipulated, giving either the dinuclear system, or the first example of a trinuclear circular helicate for a Rdpt complex, [Cr3III(dpt)₃Cl₆]·1¾MeCN·¼DCM (3). Reaction of N⁴-pydpt (R = 4-pyridyl) with V^III led to an unusual shift of the pyridyl substituent from N⁴ to N¹ of the triazole, forming the ligand isomer N¹-pydpt, and giving a dinuclear doubly-triazole bridged complex, [V2III(N¹-pydpt)₂Cl₆]·2MeCN (4). Reaction with Cr^III results in loss of the 4-pyridyl ring and a mixture of the di- and trinuclear complexes, 2 and 3. Interestingly, partial oxidation of the V^III in dinuclear complex 4 to vanadyl V^IV=O was identified by crystallographic analysis of partially oxidized single crystals, [(V^IVO)_0.84(V^III)_1.16(N¹-pydpt)₂Cl_5.16]·0.84H₂O·1.16MeCN (5).

Synthesis, Spectroscopic Characterization, Molecular Docking, and Evaluation of Antibacterial Potential of Transition Metal Complexes Obtained Using Triazole Chelating Ligand

Mononuclear chelates of Ni(II), Co(II), Fe(III), Cd(II), and Cu(II) derived from triazole novel tridentate ligands were prepared and characterized by different spectroscopic methods. The metal to ligand ratio was 1 : 2, which was revealed by elemental analysis. All the complexes were electrolytic in nature as suggested by the conductivity measurements. IR pointed out that the coordination of the triazole ligand toward the metal ions was carried out through N amino and S thiophenolic atoms. The complexes were found to have octahedral geometry, and their thermal stability was also studied. The XRD spectrum of Co(II) and Fe(III) complexes concluded their crystalline structure. The parent ligand and its chelates were investigated for antimicrobial potential. Bioassay of all triazole complexes showed increased activity as compared to that of the ligand. The complexes having Ni(II), Co(II), and Cu(II) ions as metal center exhibited superior antibacterial activity in opposition to Gram-positive (B. subtilis and S. pyogenes) and Gram-negative (E. coli and P. vulgaris) bacterium as compared to standard.

A cyanide-bridged heterometallic coordination polymer constructed from square-planar [Ni(CN)4]2−: synthesis, crystal structure, thermal decomposition, electron paramagnetic resonance (EPR) spectrum and magnetic properties

Square-planar complexes are commonly formed by transition metal ions having ad8electron configuration. Planar cyanometallate anions have been used extensively as design elements in supramolecular coordination systems. In particular, square-planar tetracyanometallate(II) ions,i.e.[M(CN)4]2−(MII= Ni, Pd or Pt), are used as good building blocks for bimetallic Hofmann-type assemblies and their analogues. Square-planar tetracyanonickellate(II) complexes have been extensively developed withN-donor groups as additional co-ligands, but studies of these systems usingO-donor ligands are scarce. A new cyanide-bridged CuII–NiIIheterometallic compound, poly[[diaquatetra-μ2-cyanido-κ8C:N-nickel(II)copper(II)] monohydrate], {[CuIINiII(CN)4(H2O)2]·H2O}n, has been synthesized and characterized by X-ray single-crystal diffraction analyses, vibrational spectroscopy (FT–IR), thermal analysis, electron paramagnetic resonance (EPR) and magnetic moment measurements. The structural analysis revealed that it has a two-dimensional grid-like structure built up of cationic [Cu(H2O)2]2+and anionic [Ni(CN)4]2−units connected through bridging cyanide ligands. The overall three-dimensional supramolecular network is expanded by a combination of interlayer O—H...N and intralayer O—H...O hydrogen-bond interactions. The first decomposition reactions take place at 335 K under a static air atmosphere, which illustrates the existence of guest water molecules in the interlayer spaces. The electron paramagnetic resonance (EPR) spectrum confirms that the CuIIcation has an axial coordination symmetry and that the unpaired electrons occupy thed_{{{{x}^2}-y^2} orbital. In addition, magnetic investigations showed that antiferromagnetic interactions exist in the CuIIatoms through the diamagnetic [Ni(CN)4]2−ion.

Guanine-copper coordination polymers: crystal analysis and application as thin film precursors

Three copper-N9-modified guanine complexes are reported with structures ranging from a discrete trinuclear motif to a mixed-valence coordination polymer. These complexes were used as precursors for the deposition and growth of copper oxide thin films on Si(100), at two different annealing temperatures, by using a CVD technique. Subsequent resistivity measurements suggest the formation of conductive thin films, raising the possibility of using nucleobase-metal complexes as versatile thin film precursors.

Diaquabis[5-(pyrazin-2-yl-κN1)-3-(pyridin-3-yl)-1,2,4-triazolido-κN1]zinc

In the title compound, [Zn(C11H7N6)2(H2O)2], the ZnIIcation, located on an inversion center, isN,N′-chelated by two 5-(pyrazin-2-yl)-3-(pyridin-3-yl)-1,2,4-triazolide anions and is further coordinated by two water molecules in a distorted N4O2octahedral geometry. In the anionic ligand, the pyrazine and pyridine rings are twisted with respect to the central triazole ring by 5.77 (10) and 11.54 (10)°, respectively. In the crystal, classical O—H...N and weak C—H...O hydrogen bonds and π–π stacking interactions between aromatic rings [the centroid–centroid distances between triazole and pyrazine rings, and between triazole and pyridine rings are 3.623 (2) and 3.852 (2) Å, respectively] connect the molecules into a three-dimensional supramolecular architecture.

Building a two-dimensional network from mixed-valence copper units held together by acetone bridges

The mixed-valence supramolecular product di-μ2-acetone-di-μ3-trifluoroacetato-deca-μ2-trifluoroacetato-octacopper(I)dicopper(II), [Cu10(C2F3O2)12(C3H6O)2] or {[Cu(I)4(O2CCF3)4]2-{μ2-OC(CH3)2}2-[Cu(II)2(O2CCF3)4]}, was prepared by co-deposition of two building units, namely a bis-acetone adduct of [Cu(II)2(O2CCF3)4] and a very electrophilic tetranuclear [Cu(I)4(O2CCF3)4] complex. The asymmetric unit contains one molecule of the compound with a total of ten independent Cu atoms. Acetone molecules serve as bridges between the [Cu(II)2(O2CCF3)4] and [Cu(I)4(O2CCF3)4] units. Additionally, the tetracopper(I) trifluoroacetate units are involved in intermolecular Cu···O interactions, forming a layered two-dimensional network in the extended structure.

Diaquabis[5-(pyrazin-2-yl-κN1)-3-(pyridin-3-yl)-1,2,4-triazolido-κN1]cadmium

In the title compound, [Cd(C₁₁H₇N₆)₂(H₂O)₂], the Cd^II cation is located on an inversion center and is coordinated by four N atoms from two 5-(pyrazin-2-yl)-3-(pyridin-3-yl)-1,2,4-triazol­ide anions and two water mol­ecules in a distorted octa­hedral geometry. The triazolide ligand is nearly planar: the central triazole ring is oriented at dihedral angles of 4.63 (13) and 8.41 (13)° with respect to the pyrazine and pyridine rings. Inter­molecular O—H⋯N hydrogen bonds link the mol­ecules into a two-dimensional supra­molecular network parallel to (001).

Synthesis, controlled release properties, and increased antifungal activities of novel cis- and trans-racemate complexes of propiconazole

Twenty novel metal complexes M(1)(cis-L)(2)Y(2), M(1)(trans-L)(2)Y(2,) M(2)(cis-L)(4)Y(2), and M(2)(trans-L)(4)Y(2) (M(1) = Zn(II), Co(II), Cu(II); M(2) = Mn(II), Ni(II); Y = OAc, Cl, ClO(4), and NO(3)) were synthesized by reacting bivalent transitional metal salt MY(2).nH(2)O (n = 0-6) with ligands cis-racemate of propiconazole (cis-L) and trans-racemate of propiconazole (trans-L), respectively. All of these synthesized complexes were identified by atomic absorption spectrometry, elemental analysis, and IR and UV spectra. The cumulative release studies of some selected complexes in static water were performed; all determined complexes were found to exhibit attractive controlled release properties, yet the ligand release rates of cis-L complexes were slower than those of trans-L complexes. Meanwhile, it was found that the release rate of ligand cis-L from representative complex Zn(cis-L)(2)Cl(2) was affected obviously by different conditions, such as temperature, pH, and PVA film coating. The antifungal activities of the ligands and their complexes against five selected plant pathogenic fungi were evaluated; the results demonstrated that the toxicity of cis-L was 3.39-5.95 times greater than that of trans-L, and all of the synthesized complexes showed superior activities of 1.19-6.36 times to those of their ligands, especially Zn complexes having toxicities 2.62-6.36 times greater than those of their ligands. Moreover, the cis-L complexes had more sensitive activities than their relevant trans-L complexes; for example, Zn(cis-L)(2)Cl(2) appeared to be 5.00-8.67 times stronger than Zn(trans-L)(2)Cl(2) complex. In addition, the mechanism of increased antifungal activities of the title complexes in comparison with their ligands was discussed preliminarily.