Organic/inorganic molecular conductors based upon perylene and Lindquist-type polyoxometalates

The preparation, structures and physical properties of the organic/inorgani c radical salts based upon perylene (per) and Lindquist type polyoxometalat es (POMs) are reported. Three new hybrid salts have been prepared: (per)(5) [Mo6O19] (1), (per)(5)[W6O19] (2), and (per)(5)[VW5O19] (3). Only structure s 1 (P (1) over bar, Z = 2) and 3 (P (1) over bar, Z = 2) were fully determ ined as compound 2 was found to have unit cell parameters practically ident ical to 1 and, therefore, is considered isostructural with the latter. The structures consist of interpenetrated organic and mixed organic/inorganic l ayers in the ac plane alternating along the a direction. The organic layers present a novel packing mode of the perylene molecules that consists of cr iss-cross chains formed by two alternating dimers running along the c axis. Besides the ability to induce novel packings in the organic sublattice, th e possibility offered by the POMs of varying the charge while maintaining t he size and shape of the anion has enabled the control of the electronic ba nd filling and, therefore, of the electrical and magnetic properties. Thus, salts 1 and 2, where the anionic charge is -2, are diamagnetic and present lower room temperature conductivities, while salt 3, where the anionic cha rge is -3, has an impaired electron and presents a higher room temperature conductivity and a lower activation energy. Thermopower measurements show t hat salts 1 and 2 present hole-type conduction whereas salt 3 exhibits elec tron-dominating electrical transport.