Reversible photocontrol of molecular assemblies of metal complex containing azo-amphiphiles

• Published in: Thin solid films 2005-12, Vol.493 (1-2), p.230-236
• Main Authors: Einaga, Yasuaki, Mikami, Rie, Akitsu, Takashiro, Li, Guangming
• Format: Article
• Language: English
• Subjects: Chemistry; Cis–trans; Exact sciences and technology; General and physical chemistry; Photochemistry; Photoillumination; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); UV and visible light
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2004.06.198

Photo-controllable molecular systems, [M(en)2][Pt(en)2Cl2](1)4 (M2+=Pt2+, Pd2+ and en=ethylenediamine), have been designed by the self-assembly of chloride-bridged platinum/palladium complexes and photochromic amphiphiles of the azobenzene derivative, 4-[4-(N-methyl-N-n-dodecylamino)phenylazo]benzene sulfonic acid (designated as compound 1). Reversible structural changes caused by cis–trans photoisomerization of azo groups in compound 1 were observed by alternating illumination of UV and visible light. Visible illumination resulted in the formation of the plate-like structures, whereas UV illumination resulted in fragmentation of the assembling structures. Reversible changes were observed in the electronic states of the chloride-bridged platinum/palladium complexes; the plate-like structures exhibited charge transfer absorption of chloride-bridged platinum complexes and delocalized Pt(II)/Pt(IV) states, while the fragments of the separated complexes exhibited no charge transfer bands. As a consequence, we have discovered that the reversible structural changes in this system could be controlled by photoillumination.