One-Dimensional Mercury Halide Coordination Polymers Based on A Semi-Rigid N-Donor Ligand: Reversible Structural Transformation

Abstract

Four one-dimensional (1D) mercury(II) halide coordination polymers have been synthesized by using a semi-rigid N-donor ligand, 2,2′-(1,4-phenylene)-bis(N-(pyridin-3-yl)acetamide) (1,4-pbpa). While [Hg(1,4-pbpa)Cl2·CH3OH]n, 1, forms a sinusoidal chain, the complexes [Hg(1,4-pbpa)X2]n (X = Cl, 2; Br, 3; I, 4) are helical. The sinusoidal 1 undergoes reversible structural transformation with helical 2 upon removal and uptake of CH3OH, which was accompanied with the conformation adjustment of the 1,4-pbpa ligand from trans anti-anti to trans syn-anti. Pyridyl ring rotation of the 1,4-pbpa ligand that results in the change of the ligand conformation is proposed for the initiation of the structural transformation.

Impact of Isomeric Dicarboxylate Ligands on the Formation of One-Dimensional Coordination Polymers and Metallocycles: A Novel cis→trans Isomerization

“…Structural transformations in CPs initiated by various methods, such as the removal and uptake of solvents, and the exchange of solvents and guest molecules, are intriguing due to their potential applications as switches and sensors [25][26][27][28]. Such changes are not common for the CPs because of the rearrangement of the coordinate and/or covalent bonds [25,26] that require significant energy adjustment and the factors that govern the structural change remain scarcely investigated.…”

Structural Diversity of Mercury(II) Halide Complexes Containing Bis-pyridyl-bis-amide with Bulky and Angular Backbones: Ligand Effect and Metal Sensing

“…Previously, we reported several bis-pyridyl-bis-amide (bpba)-based 1D Hg(II) halide CPs [ 14 , 15 , 16 , 17 ]. By using the rigid and isomeric 2,2-(1,2-phenylene)-bis(N-pyridin-3-yl)acetamide (1,2-pbpa), 2,2’-(1,3-phenylene)-bis(N-(pyridin-3-yl)acetamide (1,3-pbpa), and 2,2-(1,4-phenylene)-bis(N-(pyridin-3-yl)acetamide (1,4-pbpa), several CPs showing 1D zigzag, helical, mesohelical, and sinusoidal structures were prepared [ 14 , 15 , 16 ], while using the rigid N,N’ -di(pyridin-3-yl)naphthalene-1,4-dicarboxamide (dpndc) afforded isostructural and helical CPs [ 17 ]. The structural diversity of these Hg(II) halide CPs containing rigid bpba are thus subject to the ligand types, whereas the role of the halide anions is only suggestive [ 14 , 15 , 16 , 17 ].…”

“…By using the rigid and isomeric 2,2-(1,2-phenylene)-bis(N-pyridin-3-yl)acetamide (1,2-pbpa), 2,2’-(1,3-phenylene)-bis(N-(pyridin-3-yl)acetamide (1,3-pbpa), and 2,2-(1,4-phenylene)-bis(N-(pyridin-3-yl)acetamide (1,4-pbpa), several CPs showing 1D zigzag, helical, mesohelical, and sinusoidal structures were prepared [ 14 , 15 , 16 ], while using the rigid N,N’ -di(pyridin-3-yl)naphthalene-1,4-dicarboxamide (dpndc) afforded isostructural and helical CPs [ 17 ]. The structural diversity of these Hg(II) halide CPs containing rigid bpba are thus subject to the ligand types, whereas the role of the halide anions is only suggestive [ 14 , 15 , 16 , 17 ]. On the other hand, the pairs of supramolecular isomers with the flexible N,N’ -di(3-pyridyl)adipoamide (L), [HgBr 2 (GAG-L)] n and [HgBr 2 (AAA-L)] n and [HgI 2 (GAG-L)] n and [HgI 2 (AAA-L)] n , exhibit mesohelical, helical, sinusoidal, and helical chains, respectively [ 18 ].…”

“…Although there are already several organic ligand-supported Hg(II) halide complexes reported, research towards understanding the general effect of the halide anion on their structural diversity is less. Moreover, it is well known that the bpba ligands may easily be tailored to form structures with different flexibility and different shapes [ 14 , 15 , 16 , 17 , 18 ]; thus, in this report, we intend to investigate the effect of the halide anion on the structural types of the Hg(II) halide complexes containing bpba ligands with a bulky and angular backbone. We prepared two bpba ligands with bulky backbones, namely N,N’ -bis(3-pyridyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diamide ( L 1 ), Figure 1 a, and N,N’ -bis(4-pyridylmethyl)bicyclo(2,2,2,)oct-7-ene-2,3,5,6-tetracarboxylic diamide ( L 2 ), Figure 1 b, as well as a bpba ligand with an angular backbone, namely 4,4′-oxybis(N-(pyridine-3-yl)benzamide) ( L 3 ), Figure 1 c. Their corresponding reactions with Hg(II) halide salts were carried out.…”