UV/Vis to NIR photoconduction in cyclopalladated complexes.
The incorporation of a rigid core, formed by a cyclopalladated azobenzene fragment bonded to an ancillary Schiff base ligand, into molecules with 12 or 11 peripheral alkyl chains has been successfully achieved. These new complexes, 1 and 2, respectively, are columnar liquid crystals between room temperature and about 50 degrees C. Both cyclometallated and ancillary ligands have been polyalkylated through either aryl ester (electron-withdrawing group) or aryl ether (electron-releasing group) linkages, in order to tune the HOMO/LUMO energy levels. The photoconductive properties of 1 and 2 have been studied as a function of their absorption properties before and after annealing, from the UV/Vis to NIR region. Compared with the reference compounds, tris-alkynyl benzene discotics, these new materials gave similar performances (sigma/I approximately 8x10(-13) S cm W(-1) with E = 10 V microm(-1) at lambda = 370 nm). Moreover, complex 2 shows a normalized photoconductivity sigma/I = 8.5x10(-13) S cm W(-1) at lambda = 760 nm. Organic photoconductors in such a high wavelength spectral range are not common and are usually assembled by mixing dyes with organic semiconductors.
Centro di Eccellenza CEMIF.CAL, LASCAMM, CR-INSTM Unità della Calabria and Licryl, CNR-INFM, Department of Chemistry, University of Calabria, 87036, Arcavacata di Rende (CS), Italy.
Nicolas
N
Godbert
Davide
D
Dattilo
Roberto
R
Termine
Iolinda
I
Aiello
Anna
A
Bellusci
Alessandra
A
Crispini
Attilio
A
Golemme
Mauro
M
Ghedini