Syntheses and metal ion complexation of novel 8-hydroxyquinoline-containing diaza-18-crown-6 ligands and analogues

Ten new 8-hydroxyquinoline-containing diaza-18-crown-6 ligands and analogue s were synthesized via a one-pot or stepwise Mannich reaction, reductive am ination, or by reacting diaza-18-crown-6 with 5, 7-dichloro-2-iodomethyl-8- quinolinol in the presence of N,N-diisopropylethylamine. The Mannich reacti on of N,N'-bis(methoxymethyl) diaza-18-crown-6 with 4-chloro-2-(1H-pyrazol- 3-yl)phenol gave the NCH2N-linked bis(3-(5-chloro-2-hydroxy)pyrazol-1-ylmet hyl)-substituted diazacrown ether (14) in a 98% yield. The reaction of bis( N,N'-methoxymethyldiaza)-18-crown-6 with 2.2 equiv of 10-hydroxybenzoquinol ine gave only the monosubstituted diazacrown ether ligand (8). Interaction of some of the ligands with various metal ions was evaluated by a calorimet ric titration technique at 25 degrees C in MeOH. Bis(8-hydroxyquinoline-2-y lmethyl)-substituted ligand 13 forms a very strong complex with Ba2+ (log K = 11.6 in MeOH) and is highly selective for Ba2+ over Na+, K+, Zn2+, and C u2+ (selectivity factor > 10(6)). The H-1 NMR spectral studies of the Ba2complexes with bis(8-hydroxyquinoline-2-ylmethyl)- and bis(5,7-dichloro-8-h ydroxyquinoline-2-ylmethyl)-substituted diaza-18-crown-6 ligands (13 and 10 ) suggest that these complexes are cryptate-like structures with the two ov erlapping hydroxyquinoline rings forming a pseudo second macroring. UV-visi ble spectra of the metal ion complexes with selected ligands suggest that t hese ligands might be used as chromophoric or fluorophoric sensors.