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 (CoCoIII)-Co-II: [Co-2(III)(H2L-1)(2)(AP(-)(1))(N-3)](ClO4)(2) (1), [Co-4(H2L-1)(2)(mu(3)-1,1,1-N-3)(2)(mu-1,1-N-3)(2)Cl-2(CH3OH)(2)]Greek ano teleia4CH(3)OH (2), [(Co2Co2III)-Co-II(HL-2)(2)(mu-CH3CO2)(2)(mu(3)-OH)(2)](NO3)(2)Greek ano teleia2CH(3)CH(2)OH (3), and [(Co2Co2III)-Co-II (H(2)L1(2)(-))(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) angstrom) 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 mu(3)-1,1,1-N-3 azido bridges, and the two dinuclear units are interconnected by two mu-1,1-N-3 and two mu(3)-1,1,1-N-3 azido bridges generating tetranuclear cationic [Co-4(H2L-1)(2)(mu(3)-1,1,1-N-3)(2)(mu-1,1-N-3)(2)Cl-2(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, mu-1,3-CH3CO2-, and mu(3)-OH- bridges, and the dinuclear units are interconnected through two deprotonated ethanolic O in the side arms of the ligands and two mu(3)-OH- bridges generating cationic tetranuclear [(Co2Co2III)-Co-II(HL-2)(2)(mu-CH3CO2)(2)(mu 3-OH)(2)](2+) units with an incomplete double cubane core. In 4, H(2)L1(-2) holds mixed-valent Co(II)/Co(III) ions in dinuclear units which dimerize through two ethanolic O (mu-RO-) in the side arms of the ligands and two ethanolic O (mu(3)-RO-) of THMAM bridges producing centrosymmetric cationic tetranuclear [(Co2Co2III)-Co-II (H(2)L1(-)(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.