Synthesis and Cyclic Voltammetry Studies of Copper Complexes of Bromo- and Alkoxyphenyl-Substituted Derivatives of Tris(2-pyridylmethyl)amine:  Influence of Cation−Alkoxy Interactions on Copper Redox Potentials

Abstract

A combination of host-guest chemistry and coordination chemistry in the design of electrochemical sensors for alkali metal and ammonium ions is described. The sensor molecules are coordination complexes between a copper ion and a functionalized tripodal ligand. Upon presentation of the ion to the sensor molecule, a shift in the redox potential of the copper ion occurs. In the course of the study, three new alkoxyphenyl-substituted derivatives of the ligand tris(2-pyridylmethyl)amine (TPA) were prepared and characterized. The synthesis of the new ligands involved the preparation of bromopyridyl-TPA derivatives followed by Suzuki coupling with substituted phenylboronic acids. Cyclic voltammetry studies of copper complexes of the ligands indicated that steric effects played a dominant role in the overall determination of the copper redox couple. Studies of the alkoxyphenyl ligands indicated that small but reproducible changes in the copper redox couple occurred upon presentation of a guest cation that would be expected to form a complex with the copper-ligand complex.

Asymmetry and steric hindrance in tripodal ligands: Reaching the limit for octahedral geometry with the newly synthesized [(6-bromo 2-pyridylmethyl) (6-fluoro 2-pyridylmethyl) (2-pyridylmethyl)] amine tripod in FeCl2 complexes

“…From BrDPA, FBrTPA could easily been obtained following a standard procedure [14,19,20] as a stable white solid and in a clean way, with a 46% yield from BrDPA. The most noticeable spectroscopic feature of this compound is the splitting of the CH 2 signals in 1 H NMR into three distinct signals at d = 3.90, 3.89 and 3.84 ppm, supporting asymmetry at the central amine site.…”

The Coordination Chemistry of FeCl3 and FeCl2 to Bis[2‐(2,3‐dihydroxyphenyl)‐6‐pyridylmethyl](2‐pyridylmethyl)amine: Access to a Diiron(III) Compound with an Unusual Pentagonal‐Bipyramidal/Square‐Pyramidal Environment

“…[4] Although condensation from simple pyridyl-based precursors of the ligands may be carried out, [5,23] we started directly with the preformed Br2TPA tripod, for convenience, and treated it with 2,3-dimethoxyphenylboronic acid. The tetramethoxy derivative BDMPTPA obtained was then treated with BBr 3 to yield the catechol-containing ligand BCATTPA.…”

“…Bis[2-(2,3-Dimethoxyphenyl)-6-pyridylmethyl](2-pyridylmethyl)amine (BDMPTPA): Br 2 TPA [5] (800 mg, 1.78 mmol) and [PdA C H T U N G T R E N N U N G (PPh 3 ) 4 ] (140 mg, 0.12 mmol) were suspended in degassed toluene (100 mL) under argon. Sodium carbonate (7.2 mL of a 2 m aqueous solution) and commercially available 2,3-dimethoxyphenylboronic acid (1 g, 5.5 mmol) dissolved in ethanol (5 mL) were added under argon.…”

“…[2][3][4] Later on, more sophisticated ligands with non-innocent groups such as crown ethers or amido-, phenoxy-, or quinone-appended ligands, to mention only a few examples, were reported with more or less expected properties. [5][6][7][8][9][10] As a particularly salient illustration of this approach, ligands with 2,5-dimethoxyphenyl, 2,5-hydroquinone, or 2,5-quinone substituents have recently been prepared and their copper complexes studied in detail to gain insight into the mechanism by which protons can be displaced at the same time that the metal center undergoes redox modification. [11] TPA ligands are easily accessible, and their iron complexes have been extensively used as tools to understand the chemistry at the active site of some iron proteins, thus making this series of compounds one of the most widely investigated classes of complexes for inorganic chemists involved in the field of biomimetics.…”

Coordination and Bioinorganic Chemistry of Aryl-Appended Tris(2-Pyridylmethyl)amine Ligands

“…An alternative synthetic route involves reductive amination via treatment of the aryl-appended pyridine carboxaldehyde with a 2-(aminomethyl)pyridine derivative in the presence of NaCNBH 3 . [23,[27][28][29] The amide-appended ligand bppppa was prepared via an alkylation pathway involving N,N-bis((6-phenyl-2-pyridyl)methyl)amine and 2-bromomethyl-6-pivaloylamidopyridine. [30,31] All aryl-appended TPA ligands reported to date that have been used to generate structurally characterized metal complexes are shown in Figure 1.…”