Design and synthesis of 4,4′-π-conjugated[2,2′]-bipyridines: a versatile class of tunable chromophores and fluorophores
Abstract
A series of 4,4′-disubstituted[2,2′]-bipyridines, featuring π-conjugated substituents such as donor-(acceptor-) substituted styryl, thienylvinyl, phenylimino and phenylazo groups, have been synthesized. X-Ray structures are provided for three ligands containing –CC–, –C
N– and –N
N– linkers, respectively. These chromophores display good to excellent thermal stabilities with decomposition temperatures of up to 350 °C. The strong influence of the nature of the endgroups and π-linkers on the optical properties is discussed. The stepwise protonation of 4,4′-dibutylaminostyryl-[2,2′]-bipyridine and its coordination behavior to different metallic moieties [Zn(II), Hg(II), Pd(II), Re(I), Re(VII)]
have also been investigated. It is found that the absorption and emission maxima can be easily tuned by these exogenous additives over a wide range of wavelengths (360 < λabs < 560 nm ; 482 < λem < 646 nm).