Diverse Structures and Dimensionalities in Zn(II), Cd(II), and Hg(II) Metal Complexes with Piperonylic Acid

Abstract

Reaction of M(MeCO2)2 (M = Zn(II), Cd(II), and Hg(II)) with 1,3-benzodioxole-5-carboxylic acid (HPip) in methanol (MeOH) yields four piperonylate compounds, one of Zn(II) ([Zn(Pip)2(H2O)2] (1c)), two of Cd(II) ([Cd(μ-Pip) 2(H2O)]n (2) and [Cd3(μ-Pip)6(MeOH)2]n (3)), and one of Hg(II) ([Hg(μ-Pip) 2]n (4)). The obtention of compounds 1c and 4 was independent of the M/L ratio. These four compounds were characterized by analytical and spectroscopic techniques. In addition, the thermal stability of 1c, 2, and 4 has been studied, and the structure of all the complexes has been determined by the single crystal X-ray diffraction method. The Zn(II) compound displayed a monomeric structure, while Cd(II) and Hg(II) complexes exhibited three polymeric arrays. The Zn(II) (1c) and Hg(II) (4) centers are four-and eight-coordinated in a tetrahedral or squareantiprism geometry, respectively. Furthermore, the Cd(II) ions are either six-(2) or six-and seven-(3) coordinated in a octahedral or both octahedral and pentagonal bipyramid geometries, respectively. In these compounds, the Pip ligand presents different coordination modes: μ1-η1 (1c); μ2-η1:η1 and μ2-η2:η1 (2); μ2-η1:η1, μ2-η2:η1 and μ3-η2:η1:η1 (3); μ1-η2 and μ2-η2:η1 (4). The extended structures were also analyzed. Their photoluminescence properties have been examined, and the quantum yields have been calculated.

Exploring the reactivity of α-Acetamidocinnamic acid and 4-Phenylpyridine with Zn(II) and Cd(II)

“…Despite these two effects, it seems that the quenching of the 4-Phpy is higher than the enhancement of the HACA and, therefore, compounds 3 and 4 present very low quantum yield values. The calculated quantum yield values of the complexes are comparable to other compounds with d 10 metal ions reported in the literature and could be promoted by their diversity on nuclearity, coordination modes and supramolecular structures [75,83,84].…”

“…From 290ºC, the compound continues its decomposition ending at 425ºC. In previous research [74,75], we recorded the photoluminescence spectra of two Zn(II) and two Cd(II) complexes with Pip and 3-phenylpyridine (3-Phpy) or 4-Phpy ligands [74]. Moreover, the photoluminescence spectra of one Zn(II), two Cd(II) and one Hg(II) piperonylate compounds were measured and their quantum yields calculated [75].…”

A Hg(i) corrugated sheet assembled by auxiliary dioxole groups and Hg⋯π interactions

“…Examples of interactions or coordination of dioxole groups to metal centers are scarce and only d 10 metal ions have exhibited such an ability. A reported case in the literature with Zn( ii ) 20 and one in our group with Hg( ii ) 21 have been found hitherto. In our case, Hg( ii )–O dioxole promoted the formation of a 3D supramolecular assembly.…”

Steric and Electronic Effects on the Structure and Photophysical Properties of Hg(II) Complexes

“…Recently, we have reported the reaction between Zn­(II), Cd­(II), Hg­(II), and HPip, leading to the formation of one Zn­(II) monomer ([Zn­(Pip) 2 (H 2 O) 2 ]) and three coordination polymers (two of Cd­(II): [Cd­(μ-Pip) 2 (H 2 O)] n and [Cd 3 (μ-Pip) 6 (MeOH) 2 ] n and one of Hg­(II): [Hg­(μ-Pip) 2 ] n ]). All of them showed different topologies, coordination numbers, and modes, depending on the metal preferences …”