Encapsulation and characterisation of cationic benzo[a]phenoxazines in zeolite HY

Different cationic fluorochromophores were sucessfully encapsulated by ship-in-the-bottle synthesis into supercages of zeolite HY. The cationic fluorochromophores are N-(5-amino-10-methyl-9H-benzo[a]phenoxazin-9-ylidene)ethanaminium (1a), N-(10-methyl-5-(propylamino)-9H-benzo[a]phenoxazin-9-ylidene)ethanaminium (1b), N-(5-(isopentylamino)-10-methyl-9H-benzo[a]phenoxazin-9-ylidene)ethanaminium (1c) and N1-((5-(isopentylamino)-9H-benzo[a]phenoxazin-9-ylidene)propane-1,3-diaminium)monobromide (1d). The success of encapsulation was proved by TGA and N2 adsorption analysis showing that zeolite Y is an excellent host for the stabilization of these fluorochromophores. Photophysical characterisation of encapsulated fluorochromophores by UV-Visible absorption and fluorescence confirmed their location inside the zeolite supercages. Thus, it was possible to develop a new approach to synthesize materials possessing benzo[a]phenoxazinium derivatives, which are potential optical sensors with high stability, without the need for solution synthesis of fluorochromophores. The authors are grateful to FCT (Portuguese Foundation for Science and Technology), under the project UID/AGR/04033/2019 and FEDER (European Fund for Regional Development) /COMPETE/ POCI – Operational Competitiveness and Internationalization Programme, under Project POCI-01-0145-FEDER-006958 for financial support to Research Centers CQ/UM, (UID/QUI/00686/2013 and UID/QUI/0686/2016) and project‘‘n-STeP–Nanostructured systems for Tail’’, a NORTE-07-0124-FEDER-000039 supported by Programa Operacional Regional do Norte (ON.2).This work is also a result of project ‘‘AIProcMat@N2020 – Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020’’, with reference NORTE-01-0145-FEDER-000006, and Associate Laboratory LSRE-LCM – UID/EQU/50020/2019. The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by Infrastructure Project No 022161 (co-financedby FEDERthrough COMPETE2020, POCI and PORL andFCTthrough PIDDAC). We also thank Dr B. Raman Raju and the graduate student Soraia P. C. Araújo for their contribution on the synthesis of materials.