Magnetic Properties and Redox Isomerism for 4,4‘-Bis(semiquinone) Complexes of Copper

Abstract

Polymeric [CuII(SQMe−SQMe)] n has been prepared with a bridging 4,4‘-bis(semiquinone) ligand. Temperature-dependent magnetic properties result from ferromagnetic and antiferromagnetic coupling interactions involving the metal and the diradical ligands. Monomeric (bpy)CuII(CatMe−BQMe) and (PPh3)2CuI(SQMe−BQMe) show that the bis(quinone) ligand is capable of intramolecular modulation of charge distribution.

Orientation-Induced Redox Isomerism in Planar Supramolecular Systems

“…For clarity, only flattened images (512 × 512 pixels) are shown. Figure 2 shows the π−A compression isotherms of non substituted and substituted phtalocyaninates, CePc 2 and Ce[(15C5) 4 Pc] 2 , respectively, and proposed model of molec ular orientation and aggregate structures that are formed in the monolayer at different surface pressure values. As shown in this figure, the substitution induces strong changes in the isotherm, with a shift of the isotherm to higher mean molecular areas and a change in the slope of the isotherm.…”

“…15,31−35 The coexistence of cerium complexes with tetrapyrrole ligands in two neutral forms (two redox isomers) that differ by the valent state of the cerium atom (III/IV) and the corresponding charge of the ligands was described earlier. 15,34,35 Unusual physicochemical and electrochemical properties of cerium bis [tetra (15 crown 5) phthalocyaninate] (Ce [(15C5) 4 Pc] 2 ; Figure 1) in comparison with other rare earth element complexes have been described recently in solution, Langmuir monolayers and Langmuir−Blodgett (LB) films. 34,36 In particular, changes in the UV−visible spectra of Ce [(15C5) 4 Pc] 2 monolayers that can be hypothetically attributed to IET were observed.…”

“…15,34,35 Unusual physicochemical and electrochemical properties of cerium bis [tetra (15 crown 5) phthalocyaninate] (Ce [(15C5) 4 Pc] 2 ; Figure 1) in comparison with other rare earth element complexes have been described recently in solution, Langmuir monolayers and Langmuir−Blodgett (LB) films. 34,36 In particular, changes in the UV−visible spectra of Ce [(15C5) 4 Pc] 2 monolayers that can be hypothetically attributed to IET were observed. 37,38 Nevertheless, theoretical under pinning and experimental proofs are not available to confirm this hypothesis.…”

“…In this context, a better understanding of the mechanisms inducing such changes (which could be the first example of orientation induced redox isomerism) could allow to control the physical process and the subsequent rational design of information storage materials. Herein we combined different complementary methods to study the behavior of the Ce[(15C5) 4 Pc] 2 complex organized in Langmuir monolayers as well as in LB films transferred at different surface pressures. We give experimental proofs of this IET and describe the driving forces inducing this transfer occurring at the air−water interface in highly ordered planar monolayers of Ce[(15C5) 4 Pc] 2 .…”

“…Herein we combined different complementary methods to study the behavior of the Ce[(15C5) 4 Pc] 2 complex organized in Langmuir monolayers as well as in LB films transferred at different surface pressures. We give experimental proofs of this IET and describe the driving forces inducing this transfer occurring at the air−water interface in highly ordered planar monolayers of Ce[(15C5) 4 Pc] 2 . 43 and unsubstituted CePc 2 37 was performed according to previously described procedures.…”