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 |
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| Authors: | Santokh S Tandon Neil Patel Scott D Bunge Esther C Wang Rachel Thompson Laurence K Thompson |
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| Institution: | 1.Department of Chemistry and Biochemistry, Kent State University - Salem Campus, Salem, OH 44460, USA;2.Department of Chemistry and Biochemistry, Kent State University, Kent, OH 44242, USA; (N.P.); (S.D.B.); (E.C.W.); (R.T.);3.Department of Chemistry, Memorial University, St. John’s, NL A1B 3X7, Canada; |
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| Abstract: | 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. |
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| Keywords: | self-assembly of Co(II) Co(III) mixed-valence Co(II)/Co(III) complexes of Schiff base ligands dinuclear tetranuclear polynuclear Co(II) Co(III) Co(II)/Co(III) complexes mixed-valence Co(II)/Co(III) complexes Cobalt(II)/Cobalt(III) complexes of Schiff base ligands with incomplete double cubane core H-bonding-directed formation of cobalt supramolecular architectures with1D-single chains and 2D-sheet structures |
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