Colorimetric detection of aliphatic primary amines and a molecular logic gate based on a photochromic phenoxyquinone derivative

A photochromic phenoxyquinone-based, sensor for aliphatic primary amine was developed. An efficient trans-to-ana photoisomerization was occurred when 6-(4′-methoxyphenoxy)-5,12-naphthacenequinone in acetonitrile was irradiated with 365 nm UV light. The photochemically generated “ana” quinone intermediate was found to undergo nucleophilic substitution reactions by aliphatic primary amines to afford a large bathochromic shift in the absorption spectra, allowing colorimetric detection of the aliphatic primary amines. Neither aromatic nor secondary and tertiary amines were able to promote the bathochromic spectral shift of the phenoxyquinone. Removal of the phenoxy group by a primary amine was confirmed by using 1H NMR analysis and a preparative scale reaction. In addition, colorimetric detection of the aliphatic primary amine was demonstrated to be feasible with phenoxyquinone-containing PDMS films. Since the large bathochromic shift occurs only in the presence of UV light and aliphatic primary amine, the sensor system functions a molecular AND logic gate.