Coordinatively saturated cyclometallated Pt(IV) azobenzene complexes: synthesis and mesomorphic behaviour

• Published in: Liquid crystals 2000-10, Vol.27 (10), p.1277-1283
• Main Authors: Ghedini, Mauro, Pucci, Daniela, Barberio, Giovanna
• Format: Article
• Language: English
• ISSN: 0267-8292; 1366-5855
• DOI: 10.1080/026782900423313

The mesomorphic 4,4-bis[4-n-octyloxybenzoyloxy]azobenzene dinuclear chloro-bridged cycloplatinated complex [(Azo)Pt(mu;-Cl)]2 (smectic C between 263 and 342 C) has been reacted with different chelating ligands, giving rise to a family of square-planar ortho-platinated derivatives, [(Azo)Pt(L)] (L = tropolonate, 8-hydroxyquinolinate and 1,1,1,5,5,5-hexafluoro2,4-pentanedionate). Thermotropic mesomorphism is preserved for these mononuclear complexes which exhibit at least a nematic mesophase and transition temperatures lower by over 100° C than that of the corresponding dimeric precursor. Oxidative addition to the Pt(II) [(Azo)Pt(L)] species of electrophilic substrates such as I 2 or CH 3 I eventually led to the corresponding octahedral [(Azo)Pt(L)(I)(X)] products. The introduction of two further ligands leads to Pt(IV) derivatives showing smectic and nematic mesophases for all L ligands. For the hexacoordinated [(Azo)Pt(L)(I)(CH 3 )] complexes it has been verified that the oxidative addition of methyl iodide is a thermally reversible process, indicating that these species have potential applications as switchable systems.