Synthesis, structure and properties of [Co(L)(NO<sub>3</sub>)]ClO<sub>4</sub>.2H<sub>2</sub>O (L = tetradentate Schiff bases): Example of chelating nitrate
1565-1570The synthesis
and characterization of three mononuclear cobalt (II) complexes of the type [Co(L)(NO3
)]ClO4.2H2O [L = N,N'-(bis(pyridin -2-yl) formylidene)butane-
1 ,4-diamine (bpfd). 1 ; N,N'-(bis(pyridin -2-yl) me thylidene)butane- l,
4-diamine (bpmd). 2; and N,N' -(bis(pyridin -2-yl)benzylidene)butane-1 ,4-diamine
(bpbd), 3] are described here. In IR, the
presence of v(NO3)
band at ~1380 cm-1 with distinct splittings is strongly suggestive of
coordination of nitrate instead of its simple counter anionic view. X-ray diffraction
studies of [Co(bpfd )(NO3)] ClO4.2H2O (1),
has been made for the exact knowledge of its coordination sphere. Structural analysis
reveals cobalt(II) centre in a distorted octahedral environment with a CoN4O2
chromophore ligated by four N atoms of the tetradentate Schiff base along with two
O atoms of nitrate in a chelating fashion. The tetradenlate chelator is folded
in the butylenic pan. The mononuclear units in 1 are engaged in intermulecular
C-H. . O and O-H .. . O hydrogen bondings leading to a 2D sheet. Electrochemical
electron transfer studies in MeCN solutions show an oxidative response presumably
due to cobalt(III)-cobalt(II) couple. All the complexes display intraligand 1(π-π*)
fluorescence and intraligand 3(π-π*) phosphorescence in glassy solutions
(MeOH at 77 K)