Preparation and Characterization of Di-, Tri-, and Tetranuclear Schiff Base Complexes Derived from Diamines and 3,4-Dihydroxybenzaldehyde

Abstract

A series of new di-, tri-, and tetranuclear Co(II) and Cu(II) complexes of three new diSchiff base ligands were synthesized by two different methods. The first method involved the synthesis of the three ligands from condensation reaction of 3,4-dihydroxybenzaldehyde (L′H2) with ethylenediamine (en), o-phenylenediamine (o-PD), or 4,5-dimethyl-1,2-phenylendiamine (DMPD) in a mole ratio of 2 : 1 followed by the reaction of the resulting Schiff bases ligands with Cu(II) or Co(II) ions in the presence of 2,2′-bipyridyl (L) to form the di- and trinuclear metal complexes. The second method involved the condensation of the copper complex LCu(II)L′ (L = 2,2′-bipyridyl, L′ = 4-formylbenzene-1,2-bis(olate)) with en, o-PD, or DMPD in a mole ratio of 2 : 1, respectively, followed by reaction with CuCl2 or Cu(ClO4)2 to form di-, tri-, and tetranuclear copper (II) complexes, respectively. The structures of the ligands and metal complexes were characterized by elemental analyses, NMR, and FTIR spectra. The geometries of metal complexes were suggested according to elemental analysis, electronic spectra, thermal analyses, atomic absorption, and magnetic moments and conductivity measurements.

Preparation, Characterization and Biological Study of New Boron Compound and Schiff Base Derived From 2-Aminophenol with Their Cu (II) and Pt (IV) Complexes

“…The lattice and coordinated water were observed at (3420-3404) and 759 cm -1 . [19,20] The spectra of the first ligand (L 1 ) ( Figure 2) showed a strong band at 3400 cm -1 due to stretching vibration of O-H group, this band was shifted to the lower frequency in the spectrum of C 1 complexat 3379 cm -1 as a result of complexation. [21] The band appearedat 3377 cm -1 was attributed to stretching vibration of N-H group for L 1 and which absent in spectra of C 1 and C 2 complexes because of coordinate through the N atom.…”

“…The band appeared at 1581 cm -1 refer to stretching mode of C=N in L 2 , this band change in profile and shifted to lower frequency at 1583 and 1577 cm -1 in C 3 and C 4 respectively as a result of coordinate N atom of C=N with metal ions. [19,21,25] Bands appeared at lower frequency due to stretching vibration of M-O, M-N and M-Cl. [21] 343 C2 3404 -2363 1417 --530 341 273 L2 3448 ---1581 ----C3 3440 ---1583 --387 312 C4 3400 ---1577 3420 500 435 318brg.…”

“…The 13 CNMR spectra of ligand L 1 and L 2 in DMSO showed resonance bands at δ (114.5-137.0 ppm) were assigned to aromatic carbon. [19] The carbon atoms number 1 gave peaks at δ 125 and 130.4 ppm for L 1 and L 2 respectively, while the carbon atoms number 2 have been shifted to δ 145.5 and 144 ppm for L 1 and L 2 respectively. [30,33] The L 2 spectra showed chemical shift of methyl group at δ 20 ppm.…”

“…[30,33] The L 2 spectra showed chemical shift of methyl group at δ 20 ppm. [19] The peak observed at δ 172 ppm was assigned to azomethine carbon [19] . The carbon atom of methanol (C-O) was exhibited peak at δ 49 ppm, and the carbon atom in acetone (C=O) showed a peak at δ 204 ppm [30] ,while the carbon atoms number 16 and 18 were exhibited peak at 34 ppm.…”

2,4-dihydroxy benzaldehyde derived Schiff bases as small molecule Hsp90 inhibitors: Rational identification of a new anticancer lead

“…The signal corresponding to the 2'-hydroxyl groups was shifted downfield because of intramolecular hydrogen bonding between it and the nitrogen of imine (OH----N=C) [42,43].…”