SUPRAMOLECULAR CHEMISTRY, Vol. 7, pp. 61-66 Reprints available zyxwvutsrq directly from the publisher Photocopying permitted by license only zyxwvutsr 0 1996 OPA (Overseas Publishers Association) Amsterdam B.V. Published in The Netherlands under license by Gordon and Breach Science Publishers SA Printed in Malaysia Coloured aza-cages for lithium encapsulation zyx CARLA BAZZICALUPI', ANDREA BENCINI', zyxwvu MARIO CIAMPOLINI*', VIEW FUSI', MAURO MICHELONI*', NICOLETTA NARDI', ILARIA RAZZOLINI and BARBARA VALTANCOLI' zyxw Department of Chemistry, University of Florence, Via Maragliano 75, I-50144 Italy and 21nstitute of Chemical Sciences, University of Urbino, P u a Rinascimento 6, I-61 029 Urbino, Italy (Received June 9, 1995) The two azacages 1-2,~dinitrobenzene-7,13~ethyl-1,4,7,10,13- pentaazabicyclo[5.5.5]eptadecane (1) and 1-2,4-dinitroben-zene-l- 2,4-dinitrobenzcne-8,l~ethyl-l~,8,ll,l~~n~bi~clo [7.5. Slnonadecane (2) have been synthesized by two Merent synthetic routes. The basidty behavior in mixed water/DMSO solution has been studied by potentiometry (25 "C, I zyxwvutsrq = 0.10 mol dm-'1): 106, = 12.76(8), lo%<, = 3.84(5) for (1). The low solubility of (2) prevents the accurate basicity constants determination. Crystals of (2) are monoclinic, space group PZ,/a, with a = 11.944(3), b = 13.587(6), c = 15.034(4) A, 8 = 9036(2)" and Z = 4; final R = 0.059 (wR2 = 0.1632) for 1211 unique observed retlections with I > 2u(I). Both cages are able to encapsulate Li+ ion, the 'Li NMR spectra (CD,OD) of [Li(l)J+and [Li(2)]+ show sharp sign& at 3.52 and 2.50 ppm respectively and indicative of high deshielded cation. INTRODUCTION The main aim of the present work is to investigate the possibility of employing aza-cages as selective lithium chromoionophores,'4 having much studied a family of aza-cages able to encapsulate lithium ion in aqueous solution with total discrimination toward sodium This is quite an unusual property, obtained by shaping a small rigid cavity in these molecules, which allow the exclusive insertion of the small lithium ion, being all the other alkaline metal ions simply too big to be inserted into the cavity. We want modify these molecules attach- ing to their periphery a chromophor sensible to the presence of the Li+ into the cavity. The overall molecular framework has not to be altered because the complexing characteristics must be preserved. Mainly for synthetic reasons we have started with nitrobenzene group deriva- tives. The two compounds 1-2,4-dinitrobenzene-7,13- dimethyl-l,4,7,10,13-pentaazabicyclo [5.5.5] eptadecane (1) and 1-2,4-dinitrobenzene-8,14-dimethy1-1,5,8,11,14- pentaazabicyclo[7.5.5]nonadecane (2) have been syn- thesized (see scheme 1). EXPERIMENTAL SECTION General Methods The 'H, 13Cand 7Li, NMR spectra were recorded at 200, 50, and 77.78 MHz respectively. Dioxane was used as standard in I3C NMR (8 = 67.4 ppm). In 'H spectra in D,O peak positions are reported relative to HOD at 4.75 ppm. LiCl aqueous solution mol dm-3) was used as standard in 7Li NMR. No2 I *To whom correspondence should be addressed. 61 Scheme 1