Metalla-Supramolecular Rectangles as Electron Reservoirs for Multielectron Reduction and Oxidation

Abstract

The electron-transfer capacity of molecular rectangle ions [Pt(II)(4)(PEt(3))(8)(mu-anth(2-))(2)(mu-L)(2)](4+) with anth = anthracene-1,8-diyl and L = 4,4'-bipyridine (bp) or 1,2-bis(4-pyridyl)ethene (bpe) was investigated in acetonitrile and dichloromethane using cyclic voltammetry, EPR, and UV-vis-near-IR spectroelectrochemistry. The compounds can be reversibly reduced, first in a two-electron process and then via two closely separated one-electron steps. Oxidation was also possible at rather low potentials in a reversible two-electron step, followed by an electrochemically irreversible process. The spectroscopic results indicate reduction at the neutral acceptor ligands L and oxidation at the formally dianionic anthracene "clips". In contrast, the prototypical molecular square ([Pt(triphos)(mu-bp)](4))(8+) undergoes only irreversible reduction.

Linear homobimetallic palladium complexes with end-capped SC(O)Me units

“…A similar behavior was previously reported for related compounds with similar bridging units between ruthenium ions [28]. In addition, complexes 8a-8d show, depending on the nature of the bridging N \ N moieties, one to three reduction peaks in the anodic region between À1.10 and À1.75 V. A similar electrochemical behavior was found for [((PEt 3 ) 2 ) 4 (l-4,4 0 -bpy) 2 (anthracenyl) 2 Pt] 4+ [29]. The ligand reductions in 8a-8d are shifted to substantially less negative potentials in comparison with free 7a-7d (see Table 4) [30].…”

Ligand‐based Reduction in a Molecular Rectangle with Four Organplatinum(IV) Vertices

“…The presence of four reversibly reducible bridging ligands in the complex ion 2 4+ conveys potential "electron reservoir" capability of the molecule [8][9][10][11]. Therefore, electrochemical and spectroelectrochemical studies were performed for 2(OTf) 4 .…”

“…Molecular squares, rectangles, and other supramolecular constructions have been assembled during the last years by combining metal centered complex fragments as vertices and bridging ligands as edges [1][2][3]. Whereas the bridges often involved molecules with conjugated π systems, the close to square-planar d 8 configurations of platinum(II) or palladium(II) were frequently used to effect the defined supramolecular structures by inert coordination using cis substitution patterns. In addition to the fascinating shapes, the capability of detecting substrates [4], the interaction with light (antenna function) [5], and the intramolecular magnetic exchange coupling [6] are other attractive aspects of such systems.…”

“…In addition to the fascinating shapes, the capability of detecting substrates [4], the interaction with light (antenna function) [5], and the intramolecular magnetic exchange coupling [6] are other attractive aspects of such systems. Selective interaction of these supramolecular macrocycles with potential guest molecules (molecular recognition) has been studied as well as the potential electroactivity [7][8][9]. For example, tetranuclear cis-bis(triorganophosphine)platinum(II) macrocycles with oxidizable anthracene-1,8-diyl donor "clips" and with reducible 4,4'-bipyridine or oxidizable ferrocenyl sites were investigated spectroelectrochemically with respect to the location of electron transfer [8,9].…”

Metallasupramolecular architectures, an overview of functional properties and applications

“…13), first in a two-electron process and then via two separated one-electron steps. 44 Oxidation was also possible at rather low potentials in a reversible two-electron step, followed by an electrochemically irreversible process. This indicates that reduction occurred at the neutral acceptor ligands and that the oxidation took place at the formally dianionic anthracene moiety.…”