Vb. Arion et al., Anion recognition by nickel(II) and cobalt(III) complexes with quadridentate ligands based on isothiosemicarbazide, POLYHEDRON, 18(3-4), 1998, pp. 451-458
New nickel(II) and cobalt(III) complexes of quadridentate ligands based on
S-substituted isothiosemicarbazides [Ni(H2L1)]PF6 (5), [Ni(H2L2)]PF6 (6), [
Ni(H2L3)]PF6 (7) and [Co(L-4)Py-2]PF6 (8), where H3L1 = pentane-2,3-dione b
is(S-methylisothiosemicarbazone), H3L2 = pentane-2,4-dione bis(S-dodecyliso
thiosemicarbazone), H3L3 = pentane-2,4-dione bis(S-ethylphenylisothiosemica
rbazone) and H2L4 = 3-oxo-pentane-2,4-dione bis(S-methylisothiosemicarbazon
e), have been prepared from the corresponding iodide salts 1-4 and used for
anion binding studies. The crystal structure of 8 has been determined by X
-ray crystallography. For hosts 5-7 reasonable binding of chloride anion in
DMSO has been found. The stability constants elucidated by H-1 NMR titrati
on are 60-100 M-1. The cobalt(III) host 8 forms a stronger complex with chl
oride (K-a = 220 M-1) compared to nickel(II) species. In addition much stro
nger binding of CH3COO- (K-a = 4420 M-1) has been observed. (C) 1998 Elsevi
er Science Ltd. All rights reserved.