Syntheses, Structures, and Magnetic Properties of Symmetric and Dissymmetric Ester‐Functionalized 3d‐4f Schiff Base Complexes

Abstract

Ester-functionalized bicompartmental Schiff base ligands and their 3d-Ln complexes (3d = Ni II , Cu II , or Zn II and Ln = Gd III , Tb III , or Dy III ) are reported. The modularity of the Schiff base structure (i.e., symmetric ester group compared with dissymmetric ester group) is illustrated to highlight the possibility offered by the ester for facile functionalization at the periphery of the ligand, in addition to its electron-withdrawing effect

When the Metal Makes the Difference: Template Syntheses of Tridentate and Tetradentate Salen-Type Schiff Base Ligands and Related Complexes

“…Reaction of the mono-, di-and tri-nuclear copper(II) complexes with N 2 O tridentate Schiff base ligands described above, and in particular the mononuclear ones, with a differently substituted G'-salH or another carbonyl derivative allows obtaining the unsymmetrically substituted N 2 O 2 and N 3 O salen-type copper(II) complexes [62,63,[65][66][67]69,70,72,74,89]. Reaction conditions usually involve the suspension or dissolution of the half-unit complex in methanol and addition of the second G'-salH or carbonyl derivative together with a deprotonating base (Et 3 N or NaOH).…”

“…The use of the chiral diamines dpen and chxn leads to complexes that have been studied for example for their NLO properties [63,68] as well as for their in vitro anticancer activity [70]. The OMe as substituent in position 3 of the sal moieties is instead beneficial for obtaining heterooligo-nuclear clusters with 4f elements such as gadolinium [69], but also terbium and dysprosium [69,89], which are interesting for their magnetic properties and the presence of strong ferromagnetic interaction between the paramagnetic centers [90]. The formation of such derivatives occurs thanks to the second coordination pocket suitable for lanthanides given by the oxygen atoms of the OMe groups in combination with the phenoxido atoms already involved in the coordination of copper(II) acting as bridges.…”

“…Molecules of [Cu(5-A-5 -D-salen/saltn)] tend to couple in head-to-tail dimers in the solid state due to dipole-dipole alignment from the charge asymmetry caused by the different substitution, together with a fifth Cu•••O(phenoxido) apical interaction [63] (Figure 5a). Bulky substituents on the ligand, such as in dpen [70] or in 2-methyl-1,2diaminopropane [89] derivatives, reduce this tendency as they allow only weaker interactions (Figure 5b). The presence of a (CH 2 ) 3 bridge linking the iminic nitrogen atoms also confers high flexibility to the tetradentate ligands, which can lead to a variable tetrahedral distortion of the copper(II) coordination environment [63,89].…”

“…Bulky substituents on the ligand, such as in dpen [70] or in 2-methyl-1,2diaminopropane [89] derivatives, reduce this tendency as they allow only weaker interactions (Figure 5b). The presence of a (CH 2 ) 3 bridge linking the iminic nitrogen atoms also confers high flexibility to the tetradentate ligands, which can lead to a variable tetrahedral distortion of the copper(II) coordination environment [63,89]. For example, this deviation from square planar geometry can be quantified by the angle θ between the CuON planes of the two sal moieties (θ = 0 and 90 • for pure square planar and pure tetrahedral geometries, respectively); this angle reaches the value of 28.…”

Reaction of Non-Symmetric Schiff Base Metallo-Ligand Complexes Possessing an Oxime Function with Ln Ions

“…In some cases, a pure organic half-unit can be isolated. This was observed in the reaction of a diketone such as acetylacetone with 1,2 diaminoethane, that gives a half-unit leaving free the second primary diamine function [14,15] or with less reactive amine functions, as in the case of orthophenylenediamine [11,16]. The reaction of butanedione monoxime with several diamines yields organic compounds that correspond to a cyclic aminal in the solid state while an equilibrium between the cyclic form and an open chain structure is evidenced in solution [17].…”