화학공학소재연구정보센터
Inorganic Chemistry, Vol.50, No.8, 3697-3706, 2011
Metal-Free and Dicopper(II) Complexes of Schiff Base [2+2] Macrocycles Derived from 2,2'-Iminobisbenzaldehyde: Syntheses, Structures, and Electrochemistry
Three new bis-terdentate Schiff base [2 + 2] macrocycles (H2LEt, H2LPr, and H2LBu) have been prepared in high yields by 1:1 condensation of 2,2'-iminobisbenzaldehyde with 1,2-diaminoethane, 1,3-diaminopropane, and 1,4-diaminobutane, respectively. Metalation of these macrocycles yields the corresponding dicopper(II) acetate (1, 2, and 3) and tetrafluoroborate (4, 5, and 6) complexes. The structures of H2LEt, H2LPr, H2LBu, [(Cu2Li)-L-II(OAc)(2)]center dot solvents (where i is Et, Pr or Bu) and [(Cu2LPr)-L-II(DMF)(4)] (BF4)(2)center dot 0.5H(2)O are reported. Intramolecular hydrogen bonding is a feature of the metal-free macrocycles. The copper(II) centers in [(Cu2Li)-L-II(OAc)(2)]center dot solvents are four coordinate, and the macrocycles have U-shaped (Et, Bu) or stepped (Pr) conformations. Complex 5 crystallizes with two dimethylformamide (DMF) molecules bound per five coordinate copper(II) center. Electrochemical studies revealed ligand based oxidations for all of the macrocycles and complexes. Complexes 1 and 2 undergo two quasi-reversible oxidations in DCM which are associated with the deposition of a visible film on the electrode after multiple scans in this oxidative region, suggestive of electropolymerization. Complexes 4-6, studied in MeCN, have Cu-II -> Cu-I redox potentials at more positive potentials than for 1-3.