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

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)2(6+) 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 cpia(3-) 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.