Molecular engineering of logic gate types by module rearrangement in 'Pourbaix Sensors': the effect of excited-state electric fieldsElectronic supplementary information (ESI) available: Synthetic details, NMR, IR, HRMS, DFT frontier molecular orbital diagrams, UV-visible absorption, fluorescence decay curves and spectra. See DOI: 10.1039/c8ob00485d

• Main Authors: Spiteri, Jake C, Denisov, Sergey A, Jonusauskas, Gediminas, Klejna, Sylwia, Szaci owski, Konrad, McClenaghan, Nathan D, Magri, David C
• Format: Article
• Language: English
• ISSN: 1477-0520; 1477-0539
• DOI: 10.1039/c8ob00485d

Two types of fluorescent logic gates are accessed from two different arrangements of the same modular components, one as an AND logic gate ( 1 ) and the other as a PASS 0 logic gate ( 2 ). The logic gates were designed with an 'electron-donor-spacer 1 -fluorophore-spacer 2 -receptor' format and demonstrated in 1 : 1 (v/v) methanol/water. The molecules consist of ferrocene as the electron donor, 4-aminonaphthalimide as the fluorophore and a tertiary alkylamine as the receptor. In the presence of high H + and Fe 3+ levels, regioisomers 1a and 1b switch 'on' as AND logic gates with fluorescence enhancement ratios of 16-fold and 10-fold, respectively, while regioisomers 2a and 2b are functionally dormant, exhibiting no fluorescence switching. The PASS 0 logic of 2a and 2b results from the transfer of an electron from the excited state fluorophore to the ferrocenium unit under oxidising conditions as predicted by DFT calculations. Time-resolved fluorescence spectroscopy provided lifetimes of 8.3 ns and 8.1 ns for 1a and 1b , respectively. The transient signal recovery rate of 1b is ∼10 ps while that of 2b is considerably longer on the nanosecond timescale. The divergent logic attributes of 1 and 2 highlight the importance of field effects and opens up a new approach for regulating logic-based molecules. Two types of fluorescent logic gates are accessed from different arrangements of the same module components: AND and PASS 0 logic gates.