An Al3+ and H2PO4-/HSO4- selective conformational arrest and bail to a pyrimidine-naphthalene anchored molecular switch

A pyrimidine-naphthalene anchored Schiff base (receptor 1) showed Al3+ selective conformational arrest by inhibition of its C=N isomerization (cis-trans) leading to its fluorescent switching in aqueous medium. Nevertheless the H2PO4 /HSO4 bailed receptor 1 from the Al3+ arrest leading to its switching 'off'. This conformational arrest and bail of receptor 1 were highly specific as no other ion pairs were able to do the same. The detection limit of the receptor 1 towards Al3+ is 1.49 x 10(-9) M and is the second highest for the same reported to date in the literature, while the same for H2PO4- and HSO4- were found to be 2.27 x 10(-7) and 2.91 x 10(-6), respectively. The mechanistic details of 'on-off' switching of the receptor 1 by the analytes have been explored through various spectroscopic studies along with theoretical calculations at density functional theory (DFT) level. The 'on-off' switching of receptor 1 through inputs Al3+ and H2PO4-/HSO4- led it to mimic with INH logic function.