Mixed 8-oxyquinolinecalix[4]arene/phenanthroline receptors as luminescence sensors for zinc(II) ions Izilda A. Bagatin a, * , Eduardo S. de Souza b , Amando S. Ito b , Henrique E. Toma a,1 a Instituto de Qu  ımica, Universidade de S~ ao Paulo, C.P. 26077, 05513-470 S~ ao Paulo, SP Brazil b Instituto de F  ısica, Universidade de S~ ao Paulo, C.P. 66318, 05315-970 S~ ao Paulo, SP Brazil Received 10 August 2002; accepted 17 November 2002 Abstract The luminescence behavior of bis-(8-oxyquinoline)calix[4]arene is practically centered on the quinoline chromophore, but in- volves efficient energy transfer from the calix[4]arene moiety. In the presence of Zn 2þ ions, coordination of the quinoline groups is observed, leading to characteristic changes in the absorption, fluorescence and NMR spectra. Energy transfer from the calix[4]arene moiety is precluded by the coordination of the Zn 2þ ions. In the resulting complex, a significant decrease in the emission quantum yields takes place. However, by incorporating an additional batho-phenanthroline ligand, a great emission enhancement has been detected, revealing the occurrence of synergistic effects in the bis-(8-oxyquinoline)calix[4]arene(batho-phenanthroline)zinc(II) complex. Ó 2002 Elsevier Science B.V. All rights reserved. Keywords: 8-Oxyquinoline; Calix[4]arene; Fluorescence sensors; Luminescence 1. Introduction Calixarene-based molecules containing organic functions such as phosphines [1,2], amides and imines [3], are attractive species for the build up of supramo- lecular structures incorporating transition metal centers. In particular, by modifying calixarenes with photolu- minescent organic groups, new interesting fluorescent receptors [4] have been devised for specific metal ions. Along this line, numerous publications have appeared focusing on the design and development of luminescent sensors for cation recognition [5,6], photoinduced in- tramolecular energy transfer [7], and photoinduced electron transfer [8] processes. Efficient metal ion luminescence in these complexes can arise upon ligand excitation, followed by ligand-to- metal energy transfer [9,10]. Recently, we have reported the synthesis and characterisation of a novel bis- (8-oxyquinoline)calix[4]arene species [11], specially de- signed for photophysical applications in supramolecular chemistry; as illustrated by their luminescence and en- ergy transfer properties in the presence of coordinated Eu 3þ and Tb 3þ ions. In this work, the influence of the closed shell, non- luminescent Zn 2þ ions, in the emission properties of bis- (8-oxyquinoline)calix[4]arene has been investigated, using single photon timing techniques. In spite of the observed decrease in the emission quantum yields, the functionalised calix[4]arene receptor has provided an useful luminescence probe, in combination with an an- cillary batho-phenanthroline ligand in the complex (as illustrated in Fig. 1). 2. Experimental 2.1. Synthesis and preparations All solvents were HPLC grade, or purified prior to use and stored under nitrogen. Unless otherwise stated, commercial grade chemicals were used without further purification. Inorganic Chemistry Communications 6 (2003) 288–293 www.elsevier.com/locate/inoche * Corresponding author. Tel.: +55-11-3091-3819; fax: + 55-11-3815- 5579. E-mail addresses: ibagatin@iq.usp.br (I.A. Bagatin), henetoma@ iq.usp.br (H.E. Toma). 1 Also corresponding author. 1387-7003/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S1387-7003(02)00756-6