A Molecular Multiproperty Switching Array Based on the Redox Behavior of a Ferrocenyl Polychlorotriphenylmethyl Radical

Abstract

All change: Three different output signals, chromic, nonlinear optical, and magnetic, can be altered simultaneously with the molecular switch based on radical 1. The electrochemical reduction and oxidation of 1 is completely reversible. These redox cycles can be repeated several times, and the corresponding changes in the optical properties can be monitored by visible spectroscopy.

Valence Tautomerism: New Challenges for Electroactive Ligands

“…The polychlorotriphenylmethyl radical 17, derived from the valence tautomeric complex 15, by replacing the ferrocene unit by a permethylated ferrocene, has been converted into an array of three redox states that exhibit distinct physical properties by reduction into their diamagnetic anionic form 17 -and/or oxidation into the ferrocenium radical de- [83] Interest in these molecular systems is considerable since they not only exhibit variations in color and magnetic properties but also show nonlinear optical responses due to their octupolar nature and their donor-acceptor dyad topology. Indeed, the color of the [K( [18]crown-6)] + 17 -salt is deep purple, radical 17 is brown, the 17 + BF 4 -salt is yellow, and the hydrocarbon 17-H is pale pink.…”

Tetrathiafulvalene–Polychlorotriphenylmethyl Dyads: Influence of Bridge and Open‐Shell Characteristics on Linear and Nonlinear Optical Properties

“…[19][20][21][22][23][24] Thus, a few years ago, some of us reported the second-order non-linear optical (SONLO) response of a family of polychlorotriphenylmethyl (PTM) radical derivatives showing large β hyperpolarizability values. [25][26][27] Interestingly, PTM radical derivatives can act as efficient electron acceptors in front of many donor molecules. [28] In view of the donor and acceptor capabilities of both TTF and radical PTM molecules, it is of high interest to combine both units in a D-π-A molecule and theoretically evaluate its NLO response.…”

Polychlorotriphenylmethyl Radicals: Towards Multifunctional Molecular Materials

“…Moreover, PTM derivatives are electroactive molecules susceptible to being reduced or oxidized to the anionic or cationic forms, allowing, in this way, the 'on-off' switching of their magnetic character. 78, 15 To further investigate their electronic and spin transport properties at the molecular level, PTM radicals have been recently deposited on surfaces of different nature by means of different approaches and, in all cases, it was proved that the magnetic character of the molecule persists on the surface. Thus, PTM molecules have been grafted by physisorption on gold(111) and on graphite (highly ordered pyrolytic graphite, HOPG), and by chemisorption on gold(111) and silicon dioxide-based substrates (Figure 2.25), and the resulting surfaces have been characterized and studied by a variety of techniques.…”

“…PTM unit provides a source of magnetism and shows a NLO response (Section 2.2.3.2). 15 The reduction of 18 into its diamagnetic anionic form 18 − , its oxidation into the ferrocenium radical derivative 18 + , and the protonation of the carbanion species 18 − to its conjugate acid form H -18 provided four states to this switchable molecular system. Thus radical 18 can be interconverted between four forms with distinct physical properties, such as magnetism, color, NLO response, and so on.…”

“…One of the first applications of these radicals was the spin labeling of amino acids and peptides. 12 Since then, PTM radicals have been used as constitutive units of mixed valence systems that present intramolecular electron transfer phenomena, 13 bistable molecular switches, 14,15 and new valence tautomeric systems, 16 17 The particular structural and electronic characteristics of PTM radicals have permitted, not only organic open shell dendrimers with high-spin ground states and low-spin excited states, inaccessible even at room temperature, to be obtained 18, 19 but also the ability to functionalize them with one or more carboxylic groups. These radicals have been used as molecular synthons to build up open shell supramolecular structures, either with a purely organic or a metal-organic nature, which show relevant porous and magnetic properties.…”