Synthesis, structure and properties of [Co(L)(NO₃)]ClO₄.2H₂O (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)