Aggregate Manganese Schiff Base Moieties by Terephthalate or Acetate:  Dinuclear Manganese and Trinuclear Mixed Metal Mn₂/Na Complexes

Abstract

A reaction system consisting of terephthalic acid, NaOH, inorganic Mn(II) or Mn(III) salt, and salicylidene alkylimine resulted in dinuclear manganese complexes (salpn)(2)Mn(2)(mu-phth)(CH(3)OH)(2) (1, salpn = N,N'-1,3-propylene-bis(salicylideneiminato); phth = terephthalate dianion), (salen)(2)Mn(2)(mu-phth)(CH(3)OH)(2) (2, salen = N,N'-ethylene-bis(salicylideneiminato)), (salen)(2)Mn(2)(mu-phth)(CH(3)OH)(H(2)O) (3), and (salen)(2)Mn(2)(mu-phth) (4), while the absence of NaOH in the reaction led to a mononuclear Mn complex (salph)Mn(CH(3)OH)(NO(3)) (5, salph = N,N'-1,2-phenylene-bis(salicylideneiminato)). In addition, a trinuclear mixed metal complex H[Mn(2)Na(salpn)(2)(mu-OAc)(2)(H(2)O)(2)](OAc)(2) (6) was obtained from the reaction system by using maleic acid instead of terephthalic acid. Five-coordinate Mn ions were found in 4 giving rise to an intermolecular interaction and constructing a one-dimensional linear structure. Antiferromagnetic exchange interactions were observed for 1-3, and a total ferromagnetic exchange of 4 was considered to stem from intermolecular magnetic coupling. (1)H NMR signals of phenolate ring and alkylene (or phenylene) backbone of the diamine are similar to those reported in the literature, and the phth protons are at -2.3 to -10.1 ppm. Studies on structure, bond valence sum analysis, and magnetic properties indicate the oxidation states of the Mn ions in 6 to be +3, which are also indicated by ESR spectra in dual mode. Ferromagnetic exchange interaction between the Mn(III) sites was observed with J = 1.74 cm(-1). A quasireversible redox pair at -0.29V/-0.12V has been assigned to the redox of Mn(2)(III)/Mn(III)Mn(II), implying the intactness of the complex backbone in solution.

Magnetic assemblies based on Mn(III) salen analogues

“…A carboxylate-bridged dinuclear Mn(III) complex, in which the opposite coordination sites were capped by H 2 O and EtOH, exhibited a weak antiferromagnetic interaction (4.75μ B at 300 K, 3.82μ B at 5 K) [57]. Liu et al synthesized terephthalate-bridged dinuclear Mn(III) complexes [58]. By capping the opposite coordination sites with a MeOH molecule, discrete di-Mn(III) complexes were obtained: [{Mn III (SB)(MeOH)} 2 (-phth)] (SB = salen 2− and salpn 2− ) (Fig.…”

“…Pecoraro et al first reported this type of compound using N,N -disalicylidene-2- there is a negligible magnetic interaction between the Mn(III) ions via the diamagnetic Na + ion, but there is a significant effect of anisotropy attributed to the Mn(III) ion (D = −6.13 cm −1 ) leading to a drop of χT at low temperature [59]. On the other hand, Liu et al [58] reported the presence of ferromagnetic exchange in the same core with the salpn 2− ligand (J = +1.74 cm −1 as H = −JS Mn1 S Mn2 ), where the decrease of χT was treated using the contribution of inter-molecular antiferromagnetic interactions (zJ = −0.125 cm −1 ) without taking into account the anisotropy of the Mn(III) ion. …”

“…Indeed, structural evidence of both species has been obtained from the crystallization of similar reactions: for example, there is a monomer [ Table 2 Pertinent bond distances (Å) and Angles ( • ) for Mn(III) out-of-plane dimeric complexes and magnetic parameters obtained from the simulation of the magnetic susceptibility (F = ferromagnetic interaction, AF = antiferromagnetic interaction, NI = non-interaction, nd = no data in the literature) Table 3 Pertinent bond distances (Å) and angles ( • ) for Mn(III) salen out-of-plane dimeric cores in metal-assembled compounds and magnetic parameters obtained from the simulation of the magnetic susceptibility (F = ferromagnetic interaction, AF = antiferromagnetic interaction, NI = non-interaction, nd = no data in the literature) The Mn(III) salen out-of-plane dimers are of great interest from a magnetic point of view. A number of such compounds have been structurally characterized and magnetically investigated so far [66,[93][94][95][96][97][98][99][100][101][102][103][104][105]58,48,41,67,94,11,49,76,45,51]. Furthermore, hetero-metal assembled compounds containing the Mn(III) dimer moiety were also designed (Section 5).…”

Synthesis, characterization and spectra studies on Zn(II) and Cu(II) complexes with thiocarbamide ligand containing Schiff base group

“…In addition, Schiff base complexes have been extensively studied in great detail as a result of their prospective applications in catalysis, magnetic properties, molecular architectures and materials chemistry by coordination chemists at all times [3][4][5][6]. Numerous reports on metal-organic frameworks based on Schiff base ligands have been reported [7][8][9][10]. Recently, Schiff base complexes have also been found to present good nonlinear optical (NLO) property [11].…”

Hydrothermal Synthesis, Conversion Reaction, and Crystal Structure of 2-D 2-bromo-1,4-benzenedicarboxylate Copper(II) Complex with 2,2′-bipyridine

“…Network diversity of coordination polymers is currently under intensive exploration due to the important relationship between structures and properties as functional materials [1][2][3][4]. In the system of Cu 2+ / 4,4¢-bipy/salicylic acid, six networks covering 0-D, 1-D, 2-D, and 3-D were successfully constructed due to partly and fully deprotonated properties of the combination of hydroxyl and carboxylic groups [5][6][7], while for binary carboxylic acid, such as benzene-1, 4-dicarboxylic acid, networks with partly deprotonated ligands are sparse.…”