Novel lanthanide coordination polymers based on bis-tridentate chelator pyrazine-2,3,5,6-tetracarboxylate with nano-channels and water clusters

A hexagonal C3-symmetric (H2O)7 guest fits well into a C3-symmetric terbium complex cavity

“…Stoeckli-Evans et al predicted that pztc may not coordinate to metal ions with bistridentate chelating mode due to the steric hindrance between the carbonyl groups [10]. In fact very recently, there have three examples of bis-tridentate chelating mode to be reported by our group [6,11] and Wang et al [12]. Two of them [11,12], incompletely deprotonated H 2 pztc 2− adopts a bis-tridentate coordinating mode, the hydrogen bond between two neighboring carboxyls of the H 2 pztc 2− playing a steady role in reducing the steric hindrance between the carbonyl groups.…”

“…After that, studies on H 4 pztc complexes passed through a long time pausing till to recent years. However, most of them are transition metal-based coordination polymers, the reports on the lanthanide-based coordination polymers remain few except three Er, Lu, Yb isomorphous complexes reported by our group very recently [6].Herein we report a novel terbium complex, {[Tb 2 (pztc) 3 ]⋅6.5H 2 O} n (1), which has 2D layer structure with hexagonal honeycomb-like cavity just like the structure of graphite. Every six Tb(III) ions are connected into a hexagon with C 3 -symmetry, in the hexagonal cavity, the C 3 -symmetry (H 2 O) 7 cluster embedded in it very fitly.…”

“…After that, studies on H 4 pztc complexes passed through a long time pausing till to recent years. However, most of them are transition metal-based coordination polymers, the reports on the lanthanide-based coordination polymers remain few except three Er, Lu, Yb isomorphous complexes reported by our group very recently [6].…”

“…Two of them [11,12], incompletely deprotonated H 2 pztc 2− adopts a bis-tridentate coordinating mode, the hydrogen bond between two neighboring carboxyls of the H 2 pztc 2− playing a steady role in reducing the steric hindrance between the carbonyl groups. The third of them [6], the completely deprotonated pztc ligand cannot form an intramolecular hydrogen bond to stabilize the structure. So the uncoordinated carboxylic O atoms comparatively deviating from the pyrazine plane (0.6806 Å) resulted in the enlargement of the distance of uncoordinated carboxylate O atoms (2.825 Å, 2.919 Å) and reducing of the steric hindrance.…”

Synthesis, Crystal Structure, Luminescent and Photocatalytic Properties of a Cd(II) Coordination Polymer with (3, 6)-Connected rtl Topology

“…Generally, coordination polymers are constructed by the self-assembly of metal ions and multidentate organic linkers via the coordination bonds under hydro(solvo)thermal conditions [6][7][8][9]. During the self-assembly process, many unpredictable factors, such as reaction temperatures, co-ligands, solvents, templates and so on, may influence the final structures [10][11][12][13]. It have been well documented that judicious selection of appropriate organic ligands and metal ions plays an important role in achieving the expected coordination polymers with the desired structures and promising properties [14,15].…”