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 Al(3+) selective conformational arrest by inhibition of its C=N isomerization (cis-trans) leading to its fluorescent switching in aqueous medium. Nevertheless the H(2)PO(4)(-)/HSO(4)(-) bailed receptor 1 from the Al(3+) 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 Al(3+) is 1.49 × 10(-9) M and is the second highest for the same reported to date in the literature, while the same for H(2)PO(4)(-) and HSO(4)(-) were found to be 2.27 × 10(-7) and 2.91 × 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 Al(3+) and H(2)PO(4)(-)/HSO(4)(-) led it to mimic with INH logic function.