78186-31-9Relevant academic research and scientific papers
Metal ion substitution and aldehyde exchange for CuII4 aggregates from two types of piperazine-based Schiff base ligands: Synthesis, X-ray structures, magnetic studies and theoretical validation
Basak, Dipmalya,Ray, Debashis
, (2020/01/21)
Two new tetranuclear CuII complexes [Cu4(L2)2(μ2-OH)2(H2O)2]·(ClO4)2·DMF·2H2O (1) and [Cu4(L3)2(μ2-OH)2(H2O)2]·(ClO4)2·DMF·H2O (2) have been synthesized containing piperazine based Schiff base ligands H2L2 (asymmetric) and H2L3 (symmetric). H2L2 contains one o-vanillin and a salicylaldehyde unit while H2L3 has two o-vanillin units. An interesting synthetic methodology involving transition metal ion induced aldehyde exchange reaction between two Schiff base ligands has been explored for the synthesis of H2L2 and H2L3. While the latter can be obtained by direct condensation of the respective amine and aldehyde, the former can only be synthesized by this procedure developed. Both 1 and 2 contain a piperazine ring bridging two CuII centers in chair conformation in the rare axial-equatorial mode of coordination. Two piperazine bridged Cu2 moieties are further connected via two hydroxido and two phenoxido bridges. Of the two Ophenoxido–Cu bonds one is short (basal) and the other is long (apical) while the hydroxido O bridges the two CuII centers symmetrically in basal–basal manner giving rise to a unique [Cu2O2] moiety where, of the four bonds linking the metals, three are basal (short) and one axial (long). Magnetic studies reveal weak antiferromagnetic interactions across the two piperazine bridges with an average exchange constant value of ?4.007 cm?1 and ?4.507 cm?1 for 1 and 2 respectively. The antiferromagnetic exchanges across the phenoxido–hydroxido bridges were found to be stronger with the average value being ?43.036 cm?1 for 1 and ?38.031 cm?1 for 2. Computational studies further support the experimental findings and the spin density plots in the HS configuration reveal that the exchange across the piperazine bridge takes place via through space mechanism. The spin density analysis in the HS and BS configurations also reveal that the exchange interaction is propagated mainly through the hydroxido bridge. The unsymmetrical nature of H2L2 leads to greater spin density at the hydroxido bridge in 1 leading to slightly stronger exchange interaction.
Synthesis and characterisation of some hexadentate Schiff-base ligands containing the piperazine moiety
Keypour, Hassan,Rezaeivala, Majid,Dehghani-Firouzabadi, Ahmad A.M.
experimental part, p. 126 - 128 (2009/10/15)
Ten hexadentate (N4O2, N4S2 and N6) Schiff-base ligands have been prepared by condensation of various aldehydes and two different linear tetraamines containing the piperazine moiety. The products have been characterised by melting point, elemental analysis and various spectroscopic methods such as: FT-IR, 1H, 13C NMR, and El mass spectrometry. The complex [Co{N, N'-bis[(pyridin-2-ylmethylene)ethyl]piperazine}][CIO4]2 has been prepared.
