Synthesis and characterisation of pendant-arm amino derivatives of 1,4,7-triazacyclononane and alkyl-bridged bis(1,4,7-triazacyclononane) macrocycles and complexation to Cu(II)

摘要

The new pentadentate and bis(pentadentate) ligands 1-methyl-4,7-bis(3-aminopropyl)-(1,4,7-triazacyclononane 6 and 1,2-bis[4,7-bis(3-aminopropyl)-1,4,7-triazacyclonon-1-yl]ethane 14 have been synthesised by reaction of acrylonitrile with the corresponding macrocyclic precursors and subsequent reduction of the nitrile groups with BF_3 (centre dot) THF. Cu(II) complexes of the two ligands having formulations [Cu(6)][BF_4])_2 and [Cu_2(14)][PF_6]_4 (centre dot) 6MeCN, respectively, have been prepared and structurally characterised. Both complexes exhibit distorted square-based pyramidal geometries about the metal centres with the two primary amino groups belonging to the pendant arms occupying basal positions [Cu-N_(ap) 2.257(6), Cu-N_(eq) 2.026(6) A for [Cu(6)]~(2+), and 2.337(2) and 2.038(3)-2.085(3) A for [Cu_2(14)]~(4+)]. The binuclear complex [Cu_2(14)]~(4+) is centrosymmetric about the ethane bridge with the two pentdentate compartments oriented away from one another to give a transoid anti-configuration with a MeCN molecule interacting with each Cu(II) centre at 2.710(4) A. both complexes have also been characterised by electronic and EPR spectro-macrocyclic ligands having 2-methylpyridyl pendant arms.