Synthesis of New Pyridinoazacrown Ethers Containing Aromatic and Heteroaromatic Proton Ionizable Substituents
作者:Andrei V. Bordunov、Paul C. Hellier、Jerald S. Bradshaw、N. Kent Dalley、Xiaolan Kou、Xian Xin Zhang、Reed M. Izatt
DOI:10.1021/jo00124a022
日期:1995.9
Methods for the synthesis of pyridinocrowns functionalized with various proton ionizable groups have been elaborated. Sixteen new ligands containing pyridine rings as part of the macrocycle or as a side arm have been prepared. Different interactive abilities of the OH and NH functions of 3,9-dioxa-6-azaundecane-1,11-diol (3) in strong base allowed the synthesis of pyridinoazacrowns 1 and 2 by cyclization with 2,6-bis((tosyloxy)methyl)pyridine (4) and THP-protected 4-hydroxy-2,6-bis(tosyloxy)methyl)pyridine (5). Pyridinoazacrown 1 was functionalized with different proton ionizable side arms by treatment first with formaldehyde in methanol to form the N-methoxymethyl derivative 6 and then treating 6 with 5-chloro-8-hydroxyquinoline or the appropriate substituted phenol. Pyridinoaza-18-crown-6 ligands containing p-methylphenol (7), p-methoxyphenol (8), p-chlorophenol (9),p-fluorophenol (10),p-cyanophenol (11), 2-formyl-4-bromophenol (12), or 5-chloro-8-hydroxyquinoline (13) groups were prepared by this process. Pyridinoazacrowns 1 and 2 were alkylated with 2-hydroxy-5-nitrobenzyl chloride or 5-chloro-8-methoxy-2-(bromomethyl)quinol followed by removal of the protecting groups to form p-nitrophenol- and 5-chloro-8-hydroxy-2-quinolinyl-substituted ligands (16, 18, and 21). Macrocycles 22 and 23 containing proton ionizable triazole and phenol functions inside the macrocyclic cavity and a pyridine side arm were prepared by cyclization of the appropriate dihalide with 6-(2'-pyridylmethyl)-3,9-dioxa-6-azaundecane-1,11-diol followed by cleavage of the THP or methoxy protecting groups. Preliminary complexation data show that the phenol-substituted pyridinoaza-18-crown-6 ligands form strong complexes with various metal cations and exhibit high selectivity toward Ag+. Macrocycle 16 containing a p-nitrophenol substituent formed a complex with benzylamine. The crystal structures for 16 and its benzylamine complex are also given here.
Origins of ‘on–off’ fluorescent behavior of 8-hydroxyquinoline containing chemosensors
作者:R. Todd Bronson、Marco Montalti、Luca Prodi、Nelsi Zaccheroni、Randy D. Lamb、N. Kent Dalley、Reed M. Izatt、Jerald S. Bradshaw、Paul B. Savage
DOI:10.1016/j.tet.2004.08.062
日期:2004.11
Derivatives of 8-hydroxyquinoline were used as model compounds to probe the pathways of non-radiative relaxation of fluorophores in two fluorescent chemosensors. Results suggest that both photo-induced proton transfer and photo-induced electron transfer contribute to quenching the fluorescence of the chemosensors. Crystal structures of an 8-hydroxyquinoline-containing chemosensor complexed to various metal ions indicate that a proton shift occurs concomitant with complex formation. This proton shift precludes both photo-induced proton and electron transfer allowing fluorescence emission from chemosensor-metal ion complexes. (C) 2004 Elsevier Ltd. All rights reserved.
Efficient Immobilization of a Cadmium Chemosensor in a Thin Film: Generation of a Cadmium Sensor Prototype
作者:R. Todd Bronson、David J. Michaelis、Randy D. Lamb、Ghaleb A. Husseini、Paul B. Farnsworth、Matthew R. Linford、Reed M. Izatt、Jerald S. Bradshaw、Paul B. Savage
DOI:10.1021/ol050027t
日期:2005.3.1
The development of an ion-selective chemosensor for Cd2+ allows generation of a "real-time" sensor, Immobilization of the chemosensor on quartz was achieved in a simple monolayer and in a thin film using a polymer intermediary. As intended, the thin film contains much more chemosensor than the monolayer and provides measurable responses to aqueous Cd2+ concentrations below 1 mu M. Alkali and alkaline earth ions do not interfere with Cd2+ sensing; Zn2+ and Cu2+ are potential interferents.