A New Approach to Chemosensors for Anions Using MCM-41 Grafted with Amino Groups** By Ana B. Descalzo, Diego Jimenez, M. Dolores Marcos , Ramón Martínez-Mµæez,* Juan Soto, Jamal El Haskouri, Carmen GuillØm, Daniel Beltrµn, Pedro Amorós ,and M. Victoria Borrachero Anionsplayafundamentalroleinawiderangeofchemical reactions and processes, and a great effort has been devoted towards the synthesis of new abiotic receptors for the selec- tive binding of anions. [1] In most cases, the development of systems able to sense the presence of target anions has been basedonsupramolecularchemistryconcepts.Onefundamen- talideainthiscontextadmitsthattheshapeoftheanionisan important parameter to take into account: for instance, one approachtoselectiveanionrecognitionisthedevelopmentof receptors having suitable cavities that fit with certain target guests.Thisidea,whichtriesinsomeaspectstomimictheac- tive sites concept known in biological systems, has been mainlyappliedtothedevelopmentofmolecular-basedrecep- tors that work in solution. A different approach to this idea could be to obtain such fitting receptors by moulding pre- formedcavitiesoforganizedsolidswithsuitableorganicmol- ecules. A proper coupling between the inorganic matrix and the organic molecules could satisfy not only the binding de- mandsoftheguests,butalsotheshape.Theuseofsuchhybrid organic±inorganic materials could be of interest in the search for new methodologies for anion recognition and sensing. In this sense, we have followed here, to the best of our knowl- edge, a new approach for the development of chemosensors foranions.Ourstrategyinvolvesthegraftingofaminoanthra- cene groups onto mesoporous silica materials. Amino groups are well-known as suitable anion coordination sites, whereas the anthracene moiety has been included as a signaling sub- unit,inordertodetecttheanion±solidinteraction.Asthein- organicsupport,wehavebeeninterestedintakingadvantage (fromamongtheavailableinorganicmatricesshowingalarge specificsurface)ofthehomogeneousporosityofthemesopo- roussilicasknownasMCM-41. [2] Inconcrete,wehavechosen aninorganicmatrixconsistingofMCM-41mesoporousnano- sized particles joined together in micrometric conglomer- ates. [3] This special topology provides, in addition to the high specific active surface of the MCM-41 solids, an important textural porosity in the range of 20 to 70 nm that may facili- tate the movement of the active species through the solid (Fig. 1). Mesostructured compounds doped with fluorescent groups [4] ordyes [5] haveattractedinterestwithrespecttopos- sibleopticalsensingapplications;however,asfarasweknow, noexampledealingwithanionsensingusingmesostructurally orderedsolidshasbeenreported. [6] Fig. 1. Characterization of solid 1:a)X-rayspectrum;b)arepresentativeSEM image(whitebarisequivalentto1 lm);c) 29 SiMASNMRspectrum. TheMCM-41solidwasconvertedtoasuitableanionrecep- tor by a straightforward reaction with 3-aminopropyltrieth- oxysilaneandfurtherreactionwith9-anthraldehydetoobtain the solid 1 (Scheme 1a). A comparative thermal analysis of the intermediate and final solids gave a functionalization of ca. 0.88 mM of complete aminoanthracene groups per gram of functionalized solid. 29 Si magic angle spinning (MAS) COMMUNICATIONS 966 Ó WILEY-VCHVerlagGmbH,D-69469Weinheim,2002 0935-9648/02/1307-0966$17.50+.50/0 Adv.Mater. 2002, 14,No.13±14,July4 ± [*] Dr. R. Martínez-Mµæez,A. B. Descalzo,D. Jimenez,Dr. M. D. Marcos, Dr.J.Soto GDDS,DepartamentodeQuímica UniversidadPolitØcnicadeValencia CaminodeVeras/n.,E-46071Valencia(Spain) E-mail:rmaez@qim.upv.es Dr.J.ElHaskouri,Dr.C.GuillØm,Prof.D.Beltrµn,Dr.P.Amorós InstitutdeCinciadelsMaterials delaUniversitatdeValncia(ICMUV) POBox2085,E-46071Valencia(Spain) Dr.M.V.Borrachero GIQIMA,DepartamentodeIngenieríadelaConstrucciónyProyectosde Ingeniería,UniversidadPolitØcnicadeValencia CaminodeVeras/n.,E-46071Valencia(Spain) [**] We thank the DGICYT (PB95-1121-C02-02, 1FD97-0508-C03-01, and AMB99-0504-C02-01)andtheSpanishMinisteriodeCienciayTecnología (MAT2000-1387-C02)forsupport.ABDthankstheMinisteriodeCiencia yTecnologíaforaDoctoralFellowship.