Employing tripodal carboxylate ligand to construct Co(ii) coordination networks modulated by N-donor ligands: syntheses, structures and magnetic properties

Abstract

Hydrothermal reaction of a tripodal bridging ligand, 5-(4-carboxyphenoxy)isophthalic acid (H₃cpia) with cobalt salts modulated by N-donor neutral ligands leads to the formation of six novel coordination networks formulated as {[Co_1.5(cpia)(o-bix)](H₂O)_1.5}_n (1), {[Co₂(cpia)(μ-OH)(m-bix)]H₂O}_n (2), {[Co_1.5(cpia)(m-bix)]}_n (3), {[Co_1.5(cpia)(p-bix)_0.5(H₂O)]H₂O}_n (4), {[Co_2.5(cpia)(Hcpia)(4,4′-bpy)_2.5](H₂O)₃}_n (5), and {[Co₃(cpia)₂(bpp)₂]H₂O}_n (6). Compound 1 exhibits a two-dimensional, (3,8)-connected layered architecture composed of trinuclear cobalt clusters. Compound 2 possesses a three-dimensional dense framework with (3,8)-connected tfz-d topology built from butterfly-shaped tetranuclear Co₄(μ₃-OH)₂⁶⁺ clusters. Similar to compound 1, trinuclear Co clusters act as secondary building units to construct the final 2D layered structure modulated by m-bix and bpp ligands in compounds 3 and 6. In compound 4, trinuclear Co clusters connected by cpia³⁻ anions give rise to two-dimensional layers, which are further pillared by p-bix ligands to the three-dimensional framework. Compound 5 features a 2D, (3,4,6)-connected molecular network assembled from alternate binuclear and mononuclear Co building blocks. The magnetic investigation indicates that strong antiferromagnetic interactions between cobalt ions are dominant in compounds 2 and 6.