Photophysical and Electrochemical Properties of a Zinc(II) [2×2] Metallogrid and its Bis(hydrazone) Ditopic Ligand

Abstract

Herein we describe the synthesis and structural characterization of a [2x2] metallogrid of Zinc(II) and its ditopic bis(hydrazone) ligand, as well as the evaluation of their photo‐physical and electrochemical properties. The synthesis of the bis(hydrazone) involves an aromatic nucleophilic substitution followed by a condensation. Then, through complexation with Zinc(II) ions the [2x2] metallogrid was obtained. The bis(hydrazone) was subjected to UV light‐induced E/Z isomerization determining its kinetic constants through Nuclear Magnetic Resonance (NMR). A clear effect of the metal and the structure was observed on the redox potentials of the metallogrid and its ligand when studied by Cyclic Voltammetry (CV) and Osteryoung Square Wave Voltammetry (OSWV). All compounds were also studied through UV‐Vis and Fluorescence spectroscopy, observing, in some cases, a pronounced pH‐effect. Our results indicate that the photophysical properties of metallogrid can be tuned through the elimination of the acidic protons from the bis(hydrazone) ligands and, together with their electrochemical properties can be used as molecular switches.

Versatility of the Amino Group in Hydrazone‐Based Molecular and Supramolecular Systems

“…Recently, without a templated mechanism, two different architectures were obtained from the self‐assembly of two structurally related bis(hydrazones) with Fe(II) under identical reaction conditions [49] . As mentioned earlier, in equimolar reaction media, symmetric bis(hydrazones) with the primary structure py‐pym‐py (pyridine‐pyrimidine‐pyridine) lead to grid‐like complexes (M 4 L 4 ) as a result of their interaction with octahedral metal ions [37,50,51] . In this case, both hydrazone arms acquire a coordinating conformation.…”

“…[49] As mentioned earlier, in equimolar reaction media, symmetric bis(hydrazones) with the primary structure py-pym-py (pyridine-pyrimidine-pyridine) lead to gridlike complexes (M 4 L 4 ) as a result of their interaction with octahedral metal ions. [37,50,51] In this case, both hydrazone arms acquire a coordinating conformation. However, the volume of the substituents on the amino group of the hydrazone moiety plays an important leading role in the self-assembly process if there are highly mobile groups near the coordination sites since it causes only one of said arms to acquire the coordinating conformation, while the other does not.…”

Electronic Effect of the [Au(PPh3)]+ Fragment in the Stabilization of Imidazolium Salts and the Destabilization of NHCs

“…[39] pKa's were determined using a direct approach at the same level of theory, [40] which has been used before in several systems. [41][42][43] Natural Bond Orbital analysis, which provided mechanistic details of the activation reaction, was performed by using the NBO Version 3.1 [44] implemented in Gaussian 16. Bond properties were determined according to the formalism of reference.…”

An Alternate [2×2] Grid Constructed Around TiO4N2 Units

“…[9][10][11][12][13] Metallosupramolecular grids [14][15][16] are a particular class of self-assembled architectures that have attracted major interest due to their redox, magnetic or spin-state transition properties. [17][18][19][20][21][22][23][24][25] The construction of such metal ion arrays is based on the mutual recognition of directional ligands (L) and metal ions (M) leading to an orthogonal arrangement of the ligands at each metal corner. The [2 × 2] grids (Figure 1) are archetypes of this family of molecules.…”

“…Thus, an impressive variety of self‐assembled metallo‐architectures have been reported including linear and circular helicates, [3,4] topological non‐trivial molecules, [5–7] metallo‐squares, [8] cages or giant spheres [9–13] . Metallosupramolecular grids [14–16] are a particular class of self‐assembled architectures that have attracted major interest due to their redox, magnetic or spin‐state transition properties [17–25] . The construction of such metal ion arrays is based on the mutual recognition of directional ligands (L) and metal ions (M) leading to an orthogonal arrangement of the ligands at each metal corner.…”