Metal complexes of a dipyridine octaazamacrocycle: stability constants, structural and modelling studies
authors Cruz, C; Carvalho, S; Delgado, R; Drew, MGB; Felix, V; Goodfellow, BJ
nationality International
journal DALTON TRANSACTIONS
keywords 14-MEMBERED TETRAAZA MACROCYCLES; SCHIFF-BASE LIGANDS; X-RAY-DIFFRACTION; MOLECULAR-MECHANICS; CRYSTAL-STRUCTURE; BARIUM(II) COMPLEX; PYRIDINE; COPPER(II); NICKEL(II); ION
abstract Two 28-membered octaazamacrocycles, [28]py(2)N(6) and Me-2[28]py(2)N(6), have been synthesized. The protonation constants of the N-methyl. derivative and the stability constants of its complexes with Ni2+, Cu2+, Zn2+, Cd2+, and Pb2+ were determined at 25degreesC in 0.10 mol dm(-3) KNO3. The high overall basicity of Me-2[28]py(2)N(6) is ascribed to the weaker repulsion between protonated contiguous charged ammonium sites separated by propyl chains. These studies together with NMR, UV-vis and EPR spectroscopies indicated the presence of mono- and di-nuclear species, The single crystal structure of the complex [Ni-2([28]py(2)N(6))(H2O)(4)]Cl-4.3H(2)O was determined, and showed each nickel centre in a distorted octahedral co-ordination environment. The nickel centres are held within the macrocycle at a large distance of 6.991(g) Angstrom from each other. The formation of mononuclear complexes was evaluated theoretically via molecular mechanics (MM) and molecular dynamics (MD) calculations and showed that these large macrocycles have sufficient flexibility to encapsulate metal ions with different stereo-electronic sizes. Structures for small and large metal ions are proposed.
publisher ROYAL SOC CHEMISTRY
issn 1477-9226
year published 2003
issue 16
beginning page 3172
ending page 3183
digital object identifier (doi) 10.1039/b304381a
web of science category Chemistry, Inorganic & Nuclear
subject category Chemistry
unique article identifier WOS:000184935200005
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journal impact factor 4.099
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