Self-Assembled Zn(II) Coordination Complexes Based
on Mixed V‑Shaped Asymmetric Multicarboxylate and N‑Donor
Ligands
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Abstract
Hydrothermal
reaction between Zn(OAc)<sub>2</sub>·2H<sub>2</sub>O and three
asymmetric semirigid V-shaped multicarboxylate ligands
H<sub>3</sub>L<sup>1–3</sup> with the help of a 4,4'-bipyridine
(4,4'-bpy) or 1,4-bis(imidazol-1-ylmethyl)benzene (bix)
linker
led to the isolation of six new coordination polymers, including [Zn<sub>3</sub>(L<sup>1</sup>)<sub>2</sub>(4,4′-bpy)<sub>2</sub>]<sub><i>n</i></sub>·(H<sub>2</sub>O)<sub>2<i>n</i></sub> (<b>1</b>), [Zn<sub>3</sub>(L<sup>2</sup>)<sub>2</sub>(4,4′-bpy)(H<sub>2</sub>O)<sub>2</sub>]<sub><i>n</i></sub>·(H<sub>2</sub>O)<sub>2<i>n</i></sub> (<b>2</b>), [Zn<sub>3</sub>(L<sup>3</sup>)<sub>2</sub>(4,4′-bpy)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>]<sub><i>n</i></sub>·(H<sub>2</sub>O)<sub>6<i>n</i></sub> (<b>3</b>), [Zn<sub>3</sub>(L<sup>1</sup>)<sub>2</sub>(bix)<sub>3</sub>]<sub><i>n</i></sub>·(H<sub>2</sub>O)<sub>7<i>n</i></sub> (<b>4</b>), [Zn<sub>3</sub>(L<sup>2</sup>)<sub>2</sub>(bix)<sub>3</sub>]<sub><i>n</i></sub>·(H<sub>2</sub>O)<sub>4<i>n</i></sub> (<b>5</b>), and [Zn<sub>3</sub>(HL<sup>3</sup>)<sub>2</sub>(bix)<sub>2</sub>]<sub><i>n</i></sub> (<b>6</b>), where H<sub>3</sub>L<sup>1</sup>, H<sub>3</sub>L<sup>2</sup>, H<sub>3</sub>L<sup>3</sup> ligands
represent 3-(2-carboxyphenoxy)phthalic acid, 4-(2-carboxyphenoxy)phthalic
acid, 3-(4-carboxyphenoxy)phthalic acid, respectively. Single crystal
X-ray diffraction analysis reveals a three-dimensional (3D) network
for <b>1</b> and <b>3</b>–<b>5</b> but a
two-dimensional (2D) structure for <b>2</b> and <b>6</b>. Despite the construction from the polymetallic chains connected
by the 4,4′-bpy ligands for both compounds <b>1</b> and <b>2</b>, a 3D architecture was revealed for the former species while
a 2D configuration for the latter one. Complex <b>3</b> contains
open nanotube building units composed of sole 44-numbered metallomacrocycles.
For <b>4</b>, the 20-numbered metallomacrocycle subunits linked
by Zn ions give a 1D chain, which further form a 3D polymeric structure
with the help of the other cyclic-shaped subunits made from the bix
ligands and Zn ions. A 3D framework of <b>5</b> is generated
from the 2D sheets simplified as a (6,3) net bound by the bix ligands.
Compound <b>6</b> shows a 2D corrugated framework simplified
as a (4,4) net assembled by the bix ligand and dinuclear zinc unit
as node. These results seem to suggest that the diversity in the building
subunits formed in <b>1</b>–<b>6</b> actually originates
from the intrinsic nature of the three asymmetric V-shaped tricarboxylate
ligands together with the tunable coordination geometry and molecular
configurations of ligands by the N-donor ligand employed. In addition,
the thermal stability and luminescence properties for the series of
six complexes have also been investigated
