Synthesis, structure and properties of [Co(L)(NO₃)]ClO₄.2H₂O (L = tetradentate Schiff bases): Example of chelating nitrate

Abstract

The 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). <b>1</b> ; 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 <i>v</i>(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 (<b>1</b>), 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 <b>1</b> 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).