Functional Supramolecular Devices: [M₄^IIL₄]⁸⁺ [2×2]‐Grid‐Type Complexes as Multilevel Molecular Electronic Species

Abstract

The [M(4)(II)L(4)](8+) [2 x 2]-grid-type complexes 1-8 present a set of features of particular interest for potential applications. All complexes exhibit multiple reduction levels at low reduction potentials paired with rather high stability. The modulation of the reduction potentials is possible by introduction of appropriate substituents on the ligands. The Co(II)(4) complexes 1-5 present a remarkable regularity in the disposition of the reduction levels, indicating the ability of the Co(II) sites to transmit electronic interactions between reduced ligands. In general, all investigated molecular systems 1-8 show characteristics typical for multilevel supramolecular electronic devices.

Homo‐ and Heterometallic [2×2] Grid Arrays Containing RuII, OsII, and FeII Subunits and their Mononuclear RuII and OsII Precursors: Synthesis, Absorption Spectra, Redox Behavior, and Luminescence Properties

“…[6] As far as the heterometallic grids are concerned, it can be noted that the reduction pattern of Ru 2 Fe 2 (Table 2, Figure 6 top) is very similar to that of Fe 2 Fe 2 , with the exception that the seventh process coincides with adsorption at the electrode. The assignment of the observable reduction processes of this species is therefore identical to the corresponding processes of Fe 2 Fe 2 .…”

“…The separation between the second and third reduction processes (about 500 mV), correlates with the pairing energy in the lowest p* orbital of 1, which is in agreement with the values for the pairing energy of similar polypyridine ligands. [6,25] On passing to the grid complexes, we have to recall that the reductions of bridging ligands in polynuclear complexes are usually shifted to less negative potentials relative to the reductions of the same ligands in mononuclear complexes; this is a consequence of the stabilization in bridging ligand orbitals induced by the additional metal(s). For Fe 2 Fe 2 (Table 2, Figure 5 top), the first reduction most likely involves a ligand orbital that has a large contribution from the pyrimidine ring, which, beside having its LUMO lower than those of the pyridine rings, is also coordinated by two metal centers.…”

“…[5,6] An additional feature of these assemblies is the possibility of directing their deposition onto solid substrates through secondary molecular recognition motifs, such as hydrogen bonding. [7a,b] In light of this, the design of advanced grid-type architectures containing different metal ions localized in a specific arrangement represents a significant step forward in the development of functional molecular devices.…”

A Double‐Switching Multistable Fe4 Grid Complex with Stepwise Spin‐Crossover and Redox Transitions

“…The third and fourth oxidations then occur between the already oxidized (formally) Fe III centers. [16] Given the robustness of the present tetrairon grid in various oxidation states, the di-mixed-valence species 1 6+ has been synthesized on a preparative scale by the addition of an excess of AgBF 4 to 1(BF 4 ) 4 in nitromethane solution at 508. The color of the reaction mixture quickly changed from deep red to deep blue, and crystalline material of 1(BF 4 ) 6 ·3MeCN could be obtained by slow diffusion of diethyl ether into an acetonitrile solution of the product.…”

Self-organization by selection: Generation of a metallosupramolecular grid architecture by selection of components in a dynamic library of ligands

“…Octahedral [2 ϫ 2] grid-type architectures based on predesigned ligands were investigated extensively in our laboratory and exhibit remarkable electronic and magnetic properties (27)(28)(29). The present species 1(M) (Fig.…”