This work was funded by FEDER - Fundo Europeu de Desenvolvimento Regional through the COMPETE 2020 - Operational Programme for Competitiveness and Internationalisation (POCI), and by Portuguese funds through FCT - Fundação para a Ciência e a Tecnologia in the framework of the project POCI-01-0145-FEDER-PTDC/QEQ- MED/0262/2014.), Portuguese Agency for Scientific Research. The Coimbra Chemistry Centre (CQC) is supported by FCT through project no 007630 UID/QUI/00313/2013, co-funded by COMPETE2020-UE. The FCT is also acknowledged for a post-doctoral grant to J. Pina (ref. SFRH/BPD/108469/2015). We acknowledge the UC-NMR facility for obtaining the NMR data (www.nmrccc.uc.pt), and Professor Mário N. Berberan- Santos (Instituto Superior Técnico) for valuable discussions The authors also gratefully acknowledge Perkin-Helmer, Inc. and Intrumentos de Laboratório Científico, Lda (ILC) for providing the EnSpire Multimode Plate Reader and Dr. Hans-Peter Steffens (Perkin-Helmer, Inc) for technical support. MOS acknowledges grant SFI IvP 13/1894.