REVIEW: Biomedical applications of Schiff base metal complexes

Cu(ii), Mn(ii) and Zn(ii) complexes of hydrazones with a quaternary ammonium moiety: synthesis, experimental and theoretical characterization and cytotoxic activity

“…IR spectra. The IR spectroscopy data confirm that the HL 1 Cl ligand (Fig. S4) is coordinated in a deprotonated form, since the ν(N-H) band at 2955 cm -1 is absent in the spectrum of all complexes 31 .…”

“…In the case of complex 2 additional weak band at 2111 cm -1 is assigned to bridging azido ligand. Instead of the ν(C=O) band at 1701 cm -1 , observed in the spectrum of the ligand HL 1 Cl, the new bands at 1698 cm -1 , 1688 cm -1 and 1690 cm -1 appeared in the spectra of complexes 1, 2 and 3, respectively, being assigned to the ν(-O-C=N) vibrations of the deprotonated hydrazide moieties. Coordination of azomethine nitrogen atoms results in the shift of ν(C=N) band from 1612 cm -1 in the spectrum of the ligand HL 1 Cl to 1604 cm -1 , 1595 cm -1 , and 1600 cm -1 in the spectra of complexes 1, 2 and 3, respectively.…”

“…S10), indicating that the ligand is coordinated in deprotonated zwitter-ionic form. Coordination of thiazole nitrogen in the Zn(II) complex can be confirmed from a downfield shift of C3-H from 7.93 ppm in the spectrum of HL 1 Cl to 8.04 ppm in the spectrum of Zn(II) complex. Due to the carbonyl oxygen atom's coordination, the carbonyl carbon (C6) signal is shifted downfield from 167.04 ppm in the spectrum of HL 1 Cl (Fig.…”

“…complexes 1-3 (Scheme 1). Reaction of the ligand HL 1 Cl with metal salts Cu(BF 4 )‧6H 2 O / MnCl 2 ‧4H 2 O / Zn(BF 4 )‧6H 2 O and NaN 3 in mole ratio 1 : 1 : 4 in methanol results in formation of mononuclear Cu(II) complex (1) with composition [CuL 1 (N 3 )(CH 3 OH)]BF 4 , binuclear Mn(II) complex 2, with composition [Mn 2 L 1 2 (µ -1,1-N 3 ) 2 (N 3 ) 2 ]2CH 3 OH, and mononuclear Zn(II) complex (3) with composition [ZnL 1 (N 3 ) 2 ] (Scheme 1). The ligand is coordinated in a deprotonated formally neutral zwitter-ionic form via NNO donor set atoms in all three complexes.…”

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

“…Among the innumerable known Schiff bases, the most used, studied, and applied are the polydentate ones, in which other coordinative sites are combined with the iminic nitrogen atom within the organic ligand skeleton. In fact, metal complexes with macrocyclic [8][9][10][11][12][13][14][15][16][17][18] and acyclic [10,13,[17][18][19][20][21] polydentate Schiff base ligands show enhanced thermodynamic stability due to the chelating effect [22]. The most famous acyclic Schiff base is the tetradentate N 2 O 2 N,N'-bis(salicylidene)ethylenediamine, H 2 salen (Figure 1), which is obtained by the condensation of two moles of salicylaldehyde, H-salH, and one mole of ethylenediamine, en, which has been now known for almost one century [23].…”