Preparation and structural characterization of hetero-dinuclear Schiff base copper(II)–zinc(II) complexes and their inhibition studies on Helicobacter pylori urease

Metal(II) Complexes of Compartmental Polynuclear Schiff Bases Containing Phenolate and Alkoxy Groups

“…Mononuclear complexes with O 2 -O 2 bonding site mode are very rare but they have been observed in a few cases with H 2 L OR -en Schiff bases with K + [61] and especially with Ln(NO 3 ) 3 (Ln = Ho, Sm, Nd) when the imino groups are protonated [62,63]. Large number of dinuclear metal complexes were formed through the incorporation of metal ions into the two coordination sites N 2 -O 2 and O 2 -O 2 including the two alkoxy groups, especially with the bi-compartmental Schiff bases (H 2 L OR -en, H 2 L OR -tn, H 2 L OR -dmtn) derived from aliphatic diamines [5,6,26,27,33,34,39,41,42,[64][65][66][67][68][69][70][71][72][73][74][75][76][77][78]. Other di-and poly-nuclear complexes were obtained through assembly of the Schiff bases or through bridging ligands [29,32,34,[36][37][38]41,64,67,68,[78][79][80][81][82][83][84].…”

“…The brownish yellow crystalline [Ni(L OEt -ambza)] (5) complex, the analog of 4, was obtained from the reaction of the ligand with Ni(NO 3 ) 2 .6H 2 O (1:1 molar ratio) in slightly basic ethanolic solution (Et 3 N, pH~9). In the 1-5 compounds, Cu(II) or Ni(II) ions are bound to the N 2 -O 2 coordination sites (see X-ray section) and many similar mononuclear [6,[20][21][22]32] [3][4][5][6][7][14][15][16]19,[25][26][27][28][29][32][33][34][35][36][37][38][39]41,42]. The rigidity associated with the Schiff bases derived from 1,2-diaminobenzene (H 2 L OR -phda) and 2-aminobenzylamine (H 2 L OEt -ambza) make the two phenolate rings not coplanar with the central benzene ring and as a result the two alkoxy groups are pointing away.…”

“…Among many of these compounds which are widely used are those emerged through the Schiff base condensation reactions of diamines (ethylenediamine, en; propylenediamine, tn; 2,2-dimethylpropylenediamine, dmtn; o-phenylenediamine, phda and o-aminobenzylamine, ambza) with 2-hydroxy-3-alkoxybenzaldehyde (Scheme 1) in ethanol or methanol [1][2][3][4][5][6][7][8][9][10][11][12][13]. This is most likely attributed to not only to their ease of preparation but also to the bridging capability of the deionized phenolic group (pK a = [8][9][10][11][12] to bind two metal ions in close proximity [1][2][3][4][5][6][14][15][16][17].…”

“…Among many of these compounds which are widely used are those emerged through the Schiff base condensation reactions of diamines (ethylenediamine, en; propylenediamine, tn; 2,2-dimethylpropylenediamine, dmtn; o-phenylenediamine, phda and o-aminobenzylamine, ambza) with 2-hydroxy-3-alkoxybenzaldehyde (Scheme 1) in ethanol or methanol [1][2][3][4][5][6][7][8][9][10][11][12][13]. This is most likely attributed to not only to their ease of preparation but also to the bridging capability of the deionized phenolic group (pK a = [8][9][10][11][12] to bind two metal ions in close proximity [1][2][3][4][5][6][14][15][16][17]. In addition, these compartmental Schiff base ligands utilize two bonding coordination sites: N 2 -O 2 + O 2 -O 2 for transition metal ions and lanthanides as well as for alkali metal ions, resulted in the formation of discrete mononuclear, homo-showed a wide variety of potential applications ranging from mimic of biologically important molecules [8,27], biomedical field [5,24], catalysis [9,11,17,23,28] to magnetic materials [14,19,26,29,30,…”

“…This is most likely attributed to not only to their ease of preparation but also to the bridging capability of the deionized phenolic group (pK a = [8][9][10][11][12] to bind two metal ions in close proximity [1][2][3][4][5][6][14][15][16][17]. In addition, these compartmental Schiff base ligands utilize two bonding coordination sites: N 2 -O 2 + O 2 -O 2 for transition metal ions and lanthanides as well as for alkali metal ions, resulted in the formation of discrete mononuclear, homo-showed a wide variety of potential applications ranging from mimic of biologically important molecules [8,27], biomedical field [5,24], catalysis [9,11,17,23,28] to magnetic materials [14,19,26,29,30,[33][34][35][36][37][38][39] and particularly in single molecular magnets (SMM) [26,[35][36][37]. The rich diversity of the Schiff base metal complexes constructed from 3-alkoxysalicylaldehyde led to the isolation of fascinating coordination compounds [14,[29][30]…”