Electrochemical synthesis and magnetic studies of neutral transition metal imidazolates and pyrazolates

Abstract

The single-step electrochemical synthesis of neutral transition metal complexes of imidazole, pyrazole and their derivatives has been achieved at ambient temperature. The metal was oxidized in an MezCO solution of the diazole to yield complexes of the general formula: [M(Iz)2 ] (where M = Co, Ni, Cu, Zn; Iz = imidazolate); [M(MeIz)2 ] (where M = Co, Ni, Cu, Zn; MeIz = 4-methylimidazolate); [M(priIz)2] (where M = Co, Ni, Cu, Zn; priIz = 2-isopropylimidazolate); [M(pyIz).] (where M = Co m, Cu n, Znll; pyIz = 2-(2'-pyridyl)imidazolate); [M(PZ)n ] (where M = Co hI, Ni n, Cu n, Znn; Pz = pyrazolate); [-M(C1Pz)n ] and [M(IPz)~] (where M = Co m, Ni", Cu n, Zn"; CIPz = 4-chloropyrazolate; IPz = 4-iodopyrazolate); [M(Me2Pz),] (where M = Co n, Cu ~, Zn"; MezPz = 3,5-dimethylpyrazolate) and [M(BrMezPz)J (where M = Co n, Ni n, Cu I, Znn; BrM%Pz = 3,5-dimethyl-4-bromopyrazolate). Vibrational spectra verified the presence of the anionic diazole and electronic spectra confirmed the stereochemistry about the metal centre. Variable temperature (360-90 K) magnetic measurements of the cobalt and copper chelates revealed strong antiferromagnetic interaction between the metal ions in the lattice. Data for the copper complexes were fitted to a Heisenberg (S = 1/2) model for an infinite one-dimensional linear chain, yielding best fit values of J=-62--65cm -x and 9=2.02-2.18. Data for the cobalt complexes were fitted to an Ising (S = 3/2) model with J = --4.62---11.7 cm-z and g = 2.06-2.49.

Metal transition complexes of tridentate Schiff base ligands derived from 2-hydrazinopyridine: synthesis, spectroscopic characterization and X-ray structures

“…For this, both the synthesis of the ligand and that of the complex must be controlled [18,19]. In this context, the Schiff bases 1-(pyridin-2-ylmethylidene)-2-(pyridin-2-yl)hydrazine (HL 1 ) [20,21], which provide three soft donating N atoms from two pyridine rings and one imino nitrogen atom were used together with metal transition salts to yield metal transition complexes in which acetate and nitrate anions can act with hard oxygen-binding sites. The synthetic procedures adopted are essential for yielding complexes with peculiar structure.…”

Numerical Simulations of the Ising Model on the Union Jack Lattice

“…The Ising model has been applied to a great variety of other physical systems such as absorption of gases on to solid surfaces, order-disorder transitions in alloys, concentrated solutions of liquids, the helix-coil transition polypeptides and the absorption of oxygen by haemoglobin. [VS95,Man88,BD06] An example, taken from [Man88], of an order-disorder transition in alloys is the binary alloy of Copper and Zinc, brass. Brass has many forms depending on the atomic percentage (that is, the number of atoms) of these metals and type of lattice.…”

Magnetic Properties of Polymorphic Cu(C3H3N2)2 Complexes

“…The transition metal (M) cations such as Co 2+ , Ni 2+ , Cu 2+ and Zn 2+ and imidazole (Im) anions (C 3 H 3 N 2 ) − form a family of organic polymers of the formula [M(C 3 H 3 N 2 ) 2 ] n [1,2,3,4]. The polymeric nature of these complexes is closely associated with the equivalence of the two nitrogen atoms in the imidazole ring, which allows the diazolate to bridge between metal centers, forming tetrahedral ... M Im Im M ... chains.…”