One-Pot Self-Assembly of Dinuclear, Tetranuclear, and H-Bonding-Directed Polynuclear Cobalt(II), Cobalt(III), and Mixed-Valence Co(II)/Co(III) Complexes of Schiff Base Ligands with Incomplete Double Cubane Core.

The reaction of 2,6-diformyl-4-methylphenol (DFMF) with 1-amino-2-propanol (AP) and tris(hydroxymethyl)aminomethane (THMAM) was investigated in the presence of Cobalt(II) salts, (X = ClO4-, CH3CO2-, Cl-, NO3-), sodium azide (NaN3), and triethylamine (TEA). In one pot, the variation in Cobalt(II) salt results in the self-assembly of dinuclear, tetranuclear, and H-bonding-directed polynuclear coordination complexes of Cobalt(III), Cobalt(II), and mixed-valence CoIICoIII: [Co2III(H2L-1)2(AP-1)(N3)](ClO4)2 (1), [Co4(H2L-1)2(µ3-1,1,1-N3)2(µ-1,1-N3)2Cl2(CH3OH)2]·4CH3OH (2), [Co2IICo2III(HL-2)2(µ-CH3CO2)2(µ3-OH)2](NO3)2·2CH3CH2OH (3), and [Co2IICo2III (H2L12-)2(THMAM-1)2](NO3)4 (4). In 1, two cobalt(III) ions are connected via three single atom bridges; two from deprotonated ethanolic oxygen atoms in the side arms of the ligands and one from the1-amino-2-propanol moiety forming a dinuclear unit with a very short (2.5430(11) Å) Co-Co intermetallic separation with a coordination number of 7, a rare feature for cobalt(III). In 2, two cobalt(II) ions in a dinuclear unit are bridged through phenoxide O and µ3-1,1,1-N3 azido bridges, and the two dinuclear units are interconnected by two µ-1,1-N3 and two µ3-1,1,1-N3 azido bridges generating tetranuclear cationic [Co4(H2L-1)2(µ3-1,1,1-N3)2(µ-1,1-N3)2Cl2(CH3OH)2]2+ units with an incomplete double cubane core, which grow into polynuclear 1D-single chains along the a-axis through H-bonding. In 3, HL2- holds mixed-valent Co(II)/Co(III) ions in a dinuclear unit bridged via phenoxide O, µ-1,3-CH3CO2-, and µ3-OH- bridges, and the dinuclear units are interconnected through two deprotonated ethanolic O in the side arms of the ligands and two µ3-OH- bridges generating cationic tetranuclear [Co2IICo2III(HL-2)2(µ-CH3CO2)2(µ3-OH)2]2+ units with an incomplete double cubane core. In 4, H2L1-2 holds mixed-valent Co(II)/Co(III) ions in dinuclear units which dimerize through two ethanolic O (µ-RO-) in the side arms of the ligands and two ethanolic O (µ3-RO-) of THMAM bridges producing centrosymmetric cationic tetranuclear [Co2IICo2III (H2L1-2)2(THMAM-1)2]4+ units which grow into 2D-sheets along the bc-axis through a network of H-bonding. Bulk magnetization measurements on 2 demonstrate that the magnetic interactions are completely dominated by an overall ferromagnetic coupling occurring between Co(II) ions.

Self-Assembly of Antiferromagnetically-Coupled Copper(II) Supramolecular Architectures with Diverse Structural Complexities.

The self-assembly of 2,6-diformyl-4-methylphenol (DFMP) and 1-amino-2-propanol (AP)/2-amino-1,3-propanediol (APD) in the presence of copper(II) ions results in the formation of six new supramolecular architectures containing two versatile double Schiff base ligands (H3L and H5L1) with one-, two-, or three-dimensional structures involving diverse nuclearities: tetranuclear [Cu4(HL2-)2(N3)4]·4CH3OH·56H2O (1) and [Cu4(L3-)2(OH)2(H2O)2] (2), dinuclear [Cu2(H3L12-)(N3)(H2O)(NO3)] (3), polynuclear {[Cu2(H3L12-)(H2O)(BF4)(N3)]·H2O}n (4), heptanuclear [Cu7(H3L12-)2(O)2(C6H5CO2)6]·6CH3OH·44H2O (5), and decanuclear [Cu10(H3L12-)4(O)2(OH)2(C6H5CO2)4] (C6H5CO2)2·20H2O (6). X-ray studies have revealed that the basic building block in 1, 3, and 4 is comprised of two copper centers bridged through one µ-phenolate oxygen atom from HL2- or H3L12-, and one µ-1,1-azido (N3-) ion and in 2, 5, and 6 by µ-phenoxide oxygen of L3- or H3L12- and µ-O2- or µ3-O2- ions. H-bonding involving coordinated/uncoordinated hydroxy groups of the ligands generates fascinating supramolecular architectures with 1D-single chains (1 and 6), 2D-sheets (3), and 3D-structures (4). In 5, benzoate ions display four different coordination modes, which, in our opinion, is unprecedented and constitutes a new discovery. In 1, 3, and 5, Cu(II) ions in [Cu2] units are antiferromagnetically coupled, with J ranging from -177 to -278 cm-1.

A Flexible Strategy for Modular Synthesis of Curcuminoid-BF2 /Curcuminoid Pairs and Their Comparative Antiproliferative Activity in Human Cancer Cell Lines.

A facile protocol that enables synthetic interconversion of CUR-BF2 and CUR compounds is described that significantly widens the preparative scope of curcuminoids, providing access to larger libraries of compounds, thus enabling comparative antiproliferative and apoptotic study of a larger library of synthetic analogs in cancer cell lines.