Structural and Magnetic Study of a Trinuclear Mn^II–Gd^III–Mn^II Complex

Abstract

The synthesis, structural determination and magnetic study of a trinuclear Mn II -Gd III -Mn II complex involving a Schiff base ligand are described. The structural study demonstrates that the complex presents a linear arrangement of the Mn and Gd ions, with hexacoordinate Mn ions in slightly distorted or distorted trigonal prism environments and nine-coordinate gadolinium ions. The Mn and Gd ions are linked by two phenoxido bridges for one Mn-Gd subunit and two phenoxido plus one nitrato bridges for the other Mn-Gd subunit. Ferromagnetic interactions operate in the complex. The

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

“…On the other hand, the reaction of the ligand with Cu(hfacac)2 and Dy(NO3)3·6H2O at pH ~ 9 (Et3N) afforded a complex that is similar to 3 except with different solvents of crystallization: [Cu(L OEt -ambza)]·H2O (4). Probably, one of the The rich diversity of the Schiff base metal complexes constructed from 3-alkoxysalicylaldehyde led to the isolation of fascinating coordination compounds [14,[29][30][31][32][36][37][38][39]. Moreover, aside from the existence of two coordination sites in these compounds, they showed some selectivity towards the N 2 -O 2 coordination sites at which 3d metal(II) (Mn 2+ , Ni 2+ , Cu 2+ , Zn 2+ ) and metal(III) (Mn 3+ , Fe 3+ ) are incorporated [6,14,18,[20][21][22]36,37,41,42].…”

“…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.…”

“…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]…”

“…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][31][32][36][37][38][39]. Moreover, aside from the existence of two coordination sites in these compounds, they showed some selectivity towards the N2-O2 coordination sites at which 3d metal(II) (Mn 2+ , Ni 2+ , Cu 2+ , Zn 2+ ) and metal(III) (Mn 3+ , Fe 3+ ) are incorporated [6,14,18,[20][21][22]…”

Les paradoxes de la mixité. Les conséquences de l'introduction de la mixité aux concours d'entrée des Écoles normales supérieures de Saint-Cloud, Fontenay-aux-Roses et Lyon

“…Ne bénéficiant pas des données empiriques adé-quates à la validation définitive de ce type d'hypothèse, c'est tout au plus un faisceau de causalités probables que nous esquisserons ici. Les recherches sur la féminisation des parcours scolaires scientifiques d'élite ont montré que l'admission à une grande école sous la forme d'un concours écrit était généralement défavorable aux jeunes femmes par rapport aux épreuves sur dossier avec oral (Marry, 2004b ;Costes, 2009). Il apparaît ici que cet effet négatif des concours écrits sur la réussite féminine à l'accès aux grandes écoles scientifiques est variable suivant les disciplines et surtout partiellement annulé en mathématiques en contexte de non mixité.…”