Palladium–Schiff Base Complexes Encapsulated in Zeolite-Y Host: Functionality Controlled by the Structure of a Guest Complex

Abstract

A series of palladium complexes of tetradendate Schiff base ligands L1 (N,N′-bis(salicylidene)phenylene-1,3-diamine) and its derivatives L2 and L3 have been synthesized by using the "flexible ligand method" within the supercage of zeolite-Y. These complexes in both their free and encapsulated states have been thoroughly characterized with the help of different characterization tools such as XRD, SEM-EDS, BET, thermal analysis, XPS, IR, and UV−vis spectroscopic studies. All these encapsulated complexes are identified with a dramatic red shift of the d−d transition in their electronic spectra when compared with their free states. Theoretical as well as experimental studies together suggest a substantial modification of the structural parameters of square planar Pd(II)−Schiff base complexes upon encapsulation within the supercage of zeolite-Y. Encapsulated complexes are also subject to show modified catalytic activities toward the Heck reaction. These heterogeneous catalysts can easily be separated from the reaction mixture and reused.

Lanthanide Complexes with N,N-Bis-(2-hydroxy-5-nitrobenzylidene)-1,2-phenylenediamine Schiff Base Ligand: Synthesis, Characterization, Photophysical Properties, and Biological Activity

“…IR spectrum of H 2 L exhibited a strong absorption band at 1616 cm -1 (C=N) (Table 2) [19]. In the spectrum of Tb_L complex the ν(C=N) absorption band was redshifted to 1602 cm -1 [18,19] due to the fact that Tb(III) ion could act as a Lewis acid, pulling away the electron density at the C=N group (Lewis base) due to coordination which weakened the C=N double bond character. Phenol 2) [18,22,33].…”

“…S. Dalapati and co-authors [15] demonstrated that H 2 L ligand can act as a colorimetric receptor selectively detecting AcOand Fions by UV-Vis spectral changes as well as by naked eye colour change (colourless to yellow). Several groups reported synthesis and characterization of H 2 L ligand and its transition metal complexes {Ni(II), Co(II), Co(III), Cu(II), and Zn(II)}, [16][17][18][19][20][21]. Supported by spectral techniques, such as UV-Vis, FT-IR, and NMR spectra, X-ray crystallography, elemental and molar conductivity analysis, H 2 L ligand was characterised as a tetradentate N 2 O 2 type bounding to metal atoms through oxygen and nitrogen atoms of the hydroxyl and imine groups, respectively.…”

Enhanced three-photon activity triggered by the AIE behaviour of a novel terpyridine-based Zn(ii) complex bearing a thiophene bridge

“…2a). 24 In addition, in contrast to the weak fluorescence in good solvent conditions (acetonitrile), the complex DZ1 exhibited strong fluorescence in ethyl acetate (poor solvent), which attracted our attention. We envisioned that DZ1 had AIE in ethyl acetate/acetonitrile mixtures.…”

Mesoporous Palladium N,N’-Bis(3-Allylsalicylidene)o-Phenylenediamine-Methyl Acrylate Resins as Heterogeneous Catalysts for the Heck Coupling Reaction

“…However, the catalytic mechanism for the Pd-SALOPHEN catalysts could involve the formation of intermediates Pd(II)-Pd(0) [67,68], or different reaction states based on the participation of Pd(II)-Pd(IV) intermediates [69,70]. Recently, Venkateswarlu et al proposed a modified mechanism for the Heck reaction, which involves the use of a Pd(II)-porphyrin tetradentate N 4 complex [71], as shown in Scheme 2.…”

“…In the case of PdAS(1)-MA and PdAS(2)-MA, lower activities were observed for these catalysts compared with Pd-SALOPHEN due to the steric constraints provided by the resin influencing the geometry of the Pd-SALOPHEN complex, and consequently modifying the catalyst’s electronic and redox properties [67]. TEM characterization was then carried out on the used PdAS(1)-MA and PdAS(2)-MA catalysts, as shown in Figure 8c,d.…”