Self-assembly of mixed-valence Co(ii/iii) and Ni(ii) clusters: azide-bridged 1D single chain coordination polymers comprised of tetranuclear units, tetranuclear Co(ii/iii) complexes, ferromagnetically coupled azide-bridged tetranuclear, and hexanuclear Ni(ii) complexes: synthesis, structural, and magnetic properties

Abstract

One-pot reactions between 2,6-diformyl-4-methylphenol (DFMP) and 2-aminoethanol (AE) in the presence of cobalt(II) salts [Co(ClO4)2, CoCl2, Co(CH3CO2)2, Co(NO3)2] and sodium azide result in the self-assembly of novel one-dimensional single chain mixed-valence cobalt coordination polymers {[Co2(II)Co2(III) (HL)2(OCH3)2(N3)3]ClO(4).5H2O.CH3OH}n (1), {[Co2(II)Co2(III) (HL)2(OCH3)2(N3)3]Cl.H2O}n (2) in which tetra-cobalt cationic units are bridged by symmetrical 1,3-azides, forming single chains; mixed valence neutral tetranuclear clusters [Co2(II)Co2(III) (HL)2(OCH3)2(N3)4]CH3OH.2H2O (3), [Co2(II)Co2(III)(HL)2(OCH3)2(N3)2(CH3CO2)2].2CH3OH.2H2O (4), and the cationic cluster [Co2(II) Co2(III) (HL)2(OCH3)2(CH3OH)2(N3)2](NO3)2 (5). In all these reactions, H3L, the potentially pentadentate (N2O3), trianionic double Schiff base ligand 2,6-bis[(2-hydroxy-ethylimino)-methyl]-4-methylphenol is formed. The reaction between DFMP and AE in the presence of nickel(ii) salts and sodium azide in methanol-water mixture results in the self-assembly of ferromagnetically coupled hexanuclear complexes [Ni6(H2L)2(HL-1)2(H2O)2(N3)6](ClO4)(2).2CH3OH (6), and [Ni6(H2L)2(HL-1)2(CH3OH)2(N3)6](BF4)2 (7), involving double (H3L) and single (H2L-1) Schiff base ligands, and a neutral tetranuclear complex [Ni4(H2L)2(OCH3)2(CH3CO2)2(N3)2] (8) with only double Schiff-base (H3L). In these complexes, the nature of the anion and the reaction conditions seem to play an important role in directing the formation of tetranuclear, hexanuclear or polymeric clusters. All complexes involve divacant double cubane-type cores containing three to four different types of bridging ligands (phenoxy, azido, methoxy/alkoxy, and acetate). Variable temperature magnetic properties of these spin coupled clusters have been investigated and magneto-structural correlations have been established.

Syntheses, structures, and properties of two mononuclear cobalt(III) azido complexes containing a tetradentate N-donor Schiff base as end-capping ligand

“…The study of mono-, di-, and polynuclear complexes of cobalt in its varied oxidation states has been a topic of current research because of their interesting synthetic, structural, spectroscopic, magnetic, and optoelectronic features [1][2][3][4][5]. The essential prerequisites for such research are the judicious choice [6] of organic spacers and inorganic/organic terminals/bridges that may lead to properties of interest.…”

Versatile coordination behaviour of a multi-dentate Schiff base with manganese(II), copper(II) and zinc(II) ions and their corrosion inhibition study

“…The main reason for scientists to be interested in building coordination polymers is the creation of new tunable functional materials with unique physical and chemical properties [6,7]. Incorporating metal ions in supra-molecular networks allow controlling metal atom positions in the final material, and adding properties to the material which are not only based alone on the metal ions, but also on the interplay between both binding partners.…”

From Molecular Magnets to Magnetic Nanomaterials – Deposition of Co7 Single‐Molecule Magnet; Theoretical Investigation of the Exchange Interactions

“…The electronic spectra of 1 was recorded by solution techniques with MeOH as the solvent and as a Nujol mull. The green MeOH solution of 1 shows a broad band at 590 nm (log ϵ = 2.68), which can be ascribed to d–d transitions of the low‐spin d 6 Co III ions and high‐spin d 7 Co II ions in accordance with the mixed‐valence state in octahedral geometry in this cluster 47,48. There are no significant differences in the shapes and positions of the peaks of the UV spectra of the complex recorded as a solid and in MeOH solution (Figure S1, Supporting Information).…”