Hydrothermal assembly, structures, topologies, luminescence, and magnetism of a novel series of coordination polymers driven by a trifunctional nicotinic acid building block.

In this work, a trifunctional N,O-building block, 5-(4-carboxyphenoxy)nicotinic acid (Hcpna), that combines three distinct types of functional groups (COOH, N-pyridyl, and O-ether) was used for the hydrothermal assembly of thirteen new coordination compounds: [Co(μ-Hcpna)] (1), [Mn(μ-cpna)(HO)] (2), [Mn(μ-cpna)(HO)] (3), [Mn(μ-cpna)(2,2'-bipy)(HO)] (4), {[Ni(μ-cpna)(2,2'-bipy)(HO)]·HO} (5), {[Cd(μ-cpna)(2,2'-bipy)]·2HO} (6), [Zn(μ-cpna)(2,2'-bipy)] (7), [Cu(μ-cpna)(2,2'-bipy)(HO)] (8), {[Mn(μ-cpna)(phen)]·6HO} (9), {[Ni(μ-cpna)(phen)(HO)]·HO} (10), [Zn(μ-cpna)(phen)] (11), {[Pb(μ-cpna)(phen)]·HO} (12), and [Ni(μ-cpna)(4,4'-bipy)(HO)] (13). These products were synthesized from the corresponding metal(ii) chlorides, Hcpna, NaOH, and optional N-donor supporting ligands or templates {bis(4-pyridyl)amine (bpa), 2,2'-bipyridine (2,2'-bipy), 4,4'-bipyridine (4,4'-bipy), or 1,10-phenanthroline (phen)}. Products 1-13 were characterized in the solid state by standard methods, including elemental and thermogravimetric analysis (TGA), IR spectroscopy, and powder (PXRD) and single-crystal X-ray diffraction. The structures of 1-13 feature distinct structural types, namely the 3D metal-organic frameworks (MOFs 1-3), the 2D coordination polymers (5, 6, 10, 12, and 13), the 1D coordination polymers (4, 8, and 9), and the 0D discrete cyclic dimers (7 and 11). Such a wide structural diversity of 1-13 is driven by various factors, including the type of the metal(ii) node, the deprotonation degree of Hcpna, and/or the type of supporting ligand or template. Notably, an addition of bpa can tune the structure of MOF 3 by the template effect. Topological classification of underlying metal-organic networks was performed, leading to several distinct topological nets: rtl (in 1), hxg-d-4-C2/m (in 2), sra (in 3), 2C1 (in 4, 8 and 9), fes (in 5, 10, and 12), hcb (in 6), and 3,4L83 (in 13). The magnetic behavior of 1-5, 8-10, and 13 was studied and theoretically modeled, disclosing antiferromagnetic interactions. The luminescence behavior of 6, 7, 11, and 12 was also investigated.