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A series of simple logic gates based on a water-soluble porphyrin molecule, 5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin (TPPS₄) is designed. Logic operations, including OR, NOR, INHIBIT and AND, have been built by two inputs of acid/base or metal ions (Al³⁺ and/or Sn⁴⁺) and two outputs of UV-vis absorption and fluorescent spectra. An OFF–ON switch triggered by Al³⁺ ion in vitro is developed based on TPPS₄.

A julolidine-based boron-phenylpyrrin small molecule has been designed and synthesized through a one-pot condensation-complexation procedure. Systematic optical studies show that this compound displays two distinct optical responses to the addition of HCl and Fe${}^{\mathrm{\text{3+}}}$ in succession: the addition of HCl induces an obvious red shift in its maximum absorption and fluorescence emission bands accompanied with the fluorescence quenching, whereas after synchronously adding H${}^{\mathrm{\text{+}}}$ and Fe${}^{\mathrm{\text{3+}}}$, the maximum absorption and fluorescence emission wavelength were found to shift little but with an obvious decrease in the absorbance and fluorescence intensity, suggesting the dual-detecting nature of this compound to H${}^{\mathrm{\text{+}}}$ and Fe${}^{\mathrm{\text{3+}}}$ under acid conditions. More interestingly, based on the HCl/Fe${}^{\mathrm{\text{3+}}}$-mediated absorption and fluorescence signal features, JBPP can function as AND, NAND, INH and IMP logic gates which can be further developed into a 2:4 digital demultiplexer These will endow this small molecule compound with great potential for applications in molecular logic material, chemosensors and biological fields.