Convenient syntheses and preliminary photophysical properties of novel 8-aminoquinoline appended diaza-18-crown-6 ligands

Novel 7,16-bis(8-amino-2-quinohnylmethyl)- and 7,16-bis(8-amino-7-quinoliny lmethyl)-diaza-18-crown-6 ligands (12 and 16) have been synthesized by redu ctive amination of 8-(di-tert-butoxycarbonyl)amino-2-quinolinecarboxaldehyd e (followed by removal of the Boc protecting groups) or 8-amino-7-quinoline carboxaldehyde with diaza-18-crown-6 using triacetoxyborohydride (NaBH(OAc) (3)) as the reducing agent. The crystal structure of ligand 16 is also give n. The absorption spectra of 12 and 16 are dominated by two intense bands a t 250 +/-5 and 238 +/-1 nm which are blue shifted upon addition of alkaline earth and heavy metal ions in acetonitrile. In addition, intensities of th e fluorescence bands of 12 and 16 are reduced in the presence of metal ions . (C) 2001 Elsevier Science Ltd. All rights reserved.