Evidence for room temperature mesomorphism in a mi×ed-valent diruthenium(II,III) quintapalmitoleate polymer

Electronic, Magnetic, and Spectroscopic Properties of Binuclear Diruthenium Tetracarboxylates: A Theoretical and Experimental Study

“…The electronic characteristics of the individual dimers are nicely reflected in their magnetic behavior, which shows the presence of 3 and 2 unpaired electrons for the (II,III) and (II,II) compounds, respectively. ,,, This fact was first interpreted by Norman, Renzoni, and Case (NRC) 5 on the basis of their Xα calculations. They proposed a (π*) 2 (δ*) 1 configuration as the ground state for the mixed-valent compounds, and a (π*) 3 (δ*) 1 configuration for the ground state of the divalent analogues.…”

“…The magnetic properties, on the other hand, have challenged the researchers for many years, since the classical MO description of MMMB ,, has not been able to offer an interpretation for their room-temperature magnetic moment. From a materials chemistry point of view, these carboxylates are of importance thanks to their physical properties, that make them suitable candidates for the design of advanced molecular materials, such as their liquid crystalline character and magnetic properties. 6a,c, …”

“…Even if this theoretical conclusion is not very well supported, as only the first state has been corrected by means of the adition of Generalized Valence Bond pairs, further experimental results supported a (π*) 2 (δ*) 2 ground-state configuration. Indeed, magnetic measurements, carried out on a wide temperature range, have shown the presence of a very strong zero-field splitting (ZFS) in both the divalent 6a,, and the mixed-valent 7a-d,g systems. Cotton et al have shown 12 that the ZFS of the (II,II) compounds could not arise from the 3 E term of a (π*) 3 (δ*) 1 configuration, giving further support to a ground-state assignment compatible with a (π*) 2 (δ*) 2 electron distribution.…”

“…It follows from the previous discussion that the subject is still a matter of investigation. Numerous experimental studies (mainly magnetic and spectroscopic measurements) were carried out in the past in order to understand the electronic structure of these species. 6a,7a,b, Moreover, several research groups are currently investigating the spectroscopic properties of these compounds both in solution ,, and in the solid state 7c-g,8,14…”

A liquid crystal derived from ruthenium(II,III) and a long-chain carboxylate

“…Mixed-valence diruthenium(II,III) tetracarboxylates, [Ru 2 -(O 2 CR) 4 X] (X À is an anion), have been extensively studied in recent years because they exhibit interesting electronic structures, spectroscopic features, magnetic behaviour and liquid crystalline (LC) properties (Aquino, 1998). In particular, LC phases (mesophases) have been obtained with longchain carboxylates, provided that an appropriate combination of the equatorial carboxylate (RCO 2 À ) and axial anion (X À ) is used (Cukiernik, Ibn-Elhaj et al, 1998;Chaia et al, 1999;Caplan et al, 1999). For example, aliphatic equatorial carboxylates combined with long-chain axial anions, such as dodecylsulfate or an aliphatic carboxylate, induce mesomorphic behaviour (Cukiernik, Ibn-Elhaj et al, 1998).…”