Mixed-Valence Tetra- and Hexanuclear Manganese Complexes from the Flexibility of Pyridine-Containing β-Diketone Ligands

Abstract

The reactions of [Mn3O(O2CCCl3)6(H2O)3] with 1-phenyl-3-(2-pyridyl)propane-1,3-dione (HL(1)) and 1-(2-pyridly)-3-(p-tolyl)propane-1,3-dione (HL(2)) in CH2Cl2 afford the mixed-valence Mn(II)2Mn(III)2 tetranuclear complexes [Mn4O(O2CCCl3)6(L(1))2] (1) and [Mn4O(O2CCCl3)6L2(2)] (2), respectively. Similar reactions employing [Mn3O(O2CPh)6(H2O)(py)2] with HL(1) and HL(2) give the Mn(II)3Mn(III)3 hexanuclear complexes [Mn6O2(O2CPh)8(L(1))3] (3) and [Mn6O2(O2CPh)8L3(2)] (4), respectively. Complexes 1.2CH2Cl2, 2.2CH2Cl2.H2O, 3.1.5CH2Cl2.Et2O.H2O, and 4.2CH2Cl2 crystallize in the triclinic space group P1, monoclinic space group P2(1)/c, monoclinic space group P2 1/ n, and monoclinic space group P2(1)/n, respectively. Complexes 1 and 2 consist of a trapped-valence tetranuclear core of [Mn(II)2Mn(III)2(mu4-O)](8+), and complexes 3 and 4 represent a new structural type, possessing a [Mn(II)3Mn(III)3(mu4-O)2](11+) core. The magnetic data indicate that complexes 3 and 4 have a ground-state spin value of S = 7/2 with significant magnetoanisotropy as gauged by the D values of -0.51 cm (-1) and -0.46 cm (-1), respectively, and frequency-dependent out-of-phase signals in alternating current magnetic susceptibility studies indicate their superparamagnetic behavior. In contrast, complexes 1 and 2 are low-spin molecules with an S = 1 ground state. Single-molecule magnetism behavior confirmed for 3 the presence of sweep-rate and temperature-dependent hysteresis loops in single-crystal M versus H studies at temperatures down to 40 mK.

Cadmium and tin complexes of Schiff-base ligands

“…Different complexes have been investigated for the treatment of diseases, such as trypanosomiasis [85] and jaundice [86]. Pyridine ligands, which have been used in the coordination chemistry of a variety of metals [87][88][89][90][91], occupy a unique position in the synthesis of biologically active compounds [92]. The chemistry of organostannyl carboxylates is one of the most fascinating fields, and pyridine tin carboxylates are the focus of many studies due to their different coordination geometries and their structural diversity, which depends upon the reaction conditions.…”

Syntheses, structures and magnetic properties of tetranuclear and trinuclear nickel(II) complexes with β-diketone-functionalized pyridinecarboxylate ligand

“…The results imply that the anions of Ni(II) salts have an important role and significant influence on the structure of complexes. Recently, Tsai and co-workers reported synthesis, crystal structure and magnetic property of mixed valence tetra-and hexa-nuclear manganese complexes [14]. These complexes were prepared by the reaction of mixed valence trinuclear …”

“…The presence of transition metals in such systems yields the potential for exhibiting additional functionality, including unusual optical, magnetic, photoactive, catalytic and electrochemical properties. The pyridine containing b-diketones have been known in organic chemistry for a long time [8], but their uses to date in coordination chemistry have been very few [9][10][11][12][13][14]. Recently, metal complexes of functionalized b-diketones ligands have been well reviewed by Tamburini and co-workers [15], some polynuclear complexes and coordination polymers with bis-b-diketones have been reported [16][17][18][19][20][21][22][23][24].…”

Penta- and heptacoordinated tin(IV) compounds derived from pyridine Schiff bases and 2-pyridine carboxylate: Synthesis and structural characterization

“…Pyridine ligands, which have been used in the coordination chemistry of a variety of metals [26][27][28][29][30], occupy a unique position in the synthesis of biologically active compounds [31]. The chemistry of organostannyl carboxylates is one of the more fascinating fields, and pyridine tin carboxylates are the focus of many studies due to their different coordination geometries and their structural diversity, which depends upon the reaction conditions.…”