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UV/Vis to NIR Photoconduction in Cyclopalladated Complexes
Author(s) -
Godbert Nicolas,
Dattilo Davide,
Termine Roberto,
Aiello Iolinda,
Bellusci Anna,
Crispini Alessandra,
Golemme Attilio,
Ghedini Mauro
Publication year - 2009
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200900023
Subject(s) - photochemistry , materials science , optoelectronics , chemistry
Funky discotics : Photoconductivity is measured in newly synthesized cyclopalladated metallomesogens exhibiting hexagonal columnar mesophases at room temperature. The tuning of the HOMO/LUMO energy levels by modification of the chain/core linkage (ester 1 vs ether 2 ) makes compound 2 photoconductive across the whole UV/Vis/NIR range.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 °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 ( σ / I ∼8×10 −13 S cm W −1 with E =10 V μm −1 at λ =370 nm). Moreover, complex 2 shows a normalized photoconductivity σ / I =8.5×10 −13 S cm W −1 at λ =760 nm. Organic photoconductors in such a high wavelength spectral range are not common and are usually assembled by mixing dyes with organic semiconductors.