Structures and Magnetostructural Correlation Analyses for Two Novel Hexanuclear Complexes Based on a Pentadentate Schiff Base Ligand

Abstract

have been synthesized, structurally characterized and magnetically studied. X-ray diffraction analyses indicated that the potentially pentadentate symmetric ligand affords variable coordination conformations. The copper ions are bound into hexameric moieties with helix-like arrangement whereas cobalts with four face-sharing monovacant distorted cubanes. Magnetic investigations revealed that within the hexanuclear unit, compound 1 exhibits antiferromagnetic interactions with the best fit parameters of J 1 =-17.96 cm À1 , J 2 =-22.26 cm À1 , zJ =-0.56 cm À1 and R = 1.1 3 10 À5 , while compound 2 affords ferromagnetic intramolecular couplings with the best simulation parameters of J 1 = +0.10 cm À1 ; J 2 = +0.15 cm À1 ; J x = J y = 0.1 cm À1 ; J z = 0.02 cm À1 ; D 1 =-0.50; D 2 =-0.45; g 1 = 2.67; g 2 = 2.57. Furthermore, the compound 2 displays slow magnetic relaxation behaviour detected by ac magnetic measurement under a 600 Oe field.

The Crystal Structure and Physicochemical Properties of New Complexes Containing a CuII-LnIII-CuII Core

“…By analyzing the coordination abilities of Schiff bases in terms of the possibility of attaching single metal ions, it can be observed that most Schiff bases formed in the reaction of diamines and their derivatives with o-hydroxyaromatic aldehydes/ketones coordinate a 3d ion in the tetradentate cavity of N 2 O 2 . It is possible to obtain mono- [12,13], di- [14][15][16][17][18], tri- [19,20], tetra- [16,21], and even hexanuclear [22] complexes (Figure 2). In the homodinuclear compounds, the metal:ligand ratio can be 2:1, 2:2, 3:2.…”

Mixed-Valent Trinuclear CoIII-CoII-CoIII Complex with 1,3-Bis(5-chlorosalicylideneamino)-2-propanol

“…Such mononuclear Mn III , Ni II , Cu II , and Pd II complexes were found in the literature [30][31][32][33][34][35][36], and a hydrolyzed product of mononuclear Co III species was also derived from a reaction of a Schiff-base ligand with cobalt salt [37]. In the other case, the mononuclear species are further connected to form trinuclear Cu II 3 [36], Zn II 3 [38], Cd II 3 [39], and Co II Co III 2 [40]; tetranuclear Mn II 2 Mn III 2 [42,43], Mn III 4 [44], Co II 4 [39,45], Co II 2 Co III 2 [46], Ni II 4 [39,46], and Zn II 4 [39,41]; hexanuclear Co II 4 Co III 2 [47] and Cu II 6 [47], octanuclear Mn II 2 Mn III 6 [48], and polynuclear Mn III complexes [25,35]. Among these oligonuclear and polynuclear metal complexes, we have focused on the trinuclear metal systems important as the first step to polynucleation, especially the Co II Co III 2 species because of the mixed-valent state.…”