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Unique Electronic and Stereochemical Properties of Salen Complexes
Published in Atsushi Nagai, Koji Takagi, Conjugated Objects, 2017
A salen ligand is readily obtained in a multigram scale by thecondensation of a salicylaldehyde and a diamine, typically in refluxing EtOH (Fig. 1.1).1 Nonsymmetrical salen ligands couldalso be selectively prepared.2 Resulting salen ligands are usuallypure enough without a tedious purification procedure. Metalinsertion reactions could be carried out under mild conditions,which is particularly important in preparing nonsymmetrical salencomplexes without isomerization. The complexation with metalproduces a robust structure that is resistant to the hydrolysis. Theease of synthesis is one of the great benefits in using the salen system.
Synthesis, structures, and computational studies of methoxydisubstituted bis(salamo)-type homopolynuclear Cu(II) and Co(II) complexes
Published in Journal of Coordination Chemistry, 2023
Yu-Xin Wei, Shi-Zhen Li, Ying Huang, Li Wang, Wen-Kui Dong
The design of various ligands to coordinate to metal(II/III) ions for the synthesis of structurally novel complexes and the application of such complexes in various fields has been extensively studied, especially for ligands containing N, O, and S donors [1–3]. Salen ligands were originally formed by condensation of salicylaldehyde and ethylenediamine. Salamo-type ligands were obtained by introducing O atoms to the imine bonds of salen-type Schiff base ligands; their substituted derivatives contain (R–CH = N–O–(CH2)n–O–N = CH–R) structural units that can make the ligands more stable [4]. Salamo-type ligands have been used with different metal(II/III) ions to synthesize a variety of mononuclear [5–7], polynuclear [8–12] and heteropolynuclear [13–19] complexes with potential applications in catalysis [20], magnetism [21], bioactivity [22] and chemical sensors [23–26].
Ni(II), Zn(II), and Fe(III) complexes derived from novel unsymmetrical salen-type ligands: preparation, characterization and some properties
Published in Journal of Coordination Chemistry, 2022
Eylem Dilmen Portakal, Yeliz Kaya, Emire Demirayak, Elif Karacan Yeldir, Ayşe Erçağ, İsmet Kaya
Metal complexes of tetradentate Salen-type ligands, consisting of two imino nitrogen and two phenolic oxygen donors, are stable due to their chelating effect and are used as homogeneous and heterogeneous catalysts in various organic conversion reactions [1–4]. Unsymmetrical salen ligands and their complexes find widespread applications in catalysis compared to their symmetrical counterparts with higher activity and recyclable catalysts [2, 5–7]. These compounds exhibit a variety of bioactive properties in addition to their catalyst and sensing properties [8–11]. After discovering asymmetric structures in metal-containing enzymes, interest in non-symmetrical Schiff base ligands and their metal complexes increased. These compounds are models for composition and geometry of metal ion binding sites in metalloproteins [12]. The apoptotic activities of Fe(III)-salen complexes increase when aromatic diamine is used instead of ethylenediamine [13]. In addition, methoxy substituted Fe(III)-salen or salen complexes are more biochemically active, probably due to their easy penetration through the cell membrane [14, 15].