Thiacalix[4]arene based reconfigurable molecular switches: set-reset memorized sequential device.

The fluorescent chemosensors 3, 5 and 7 based on thiacalix[4]arene bearing naphthyl groups have been designed and synthesized. The optical chemosensor 3 based on a thiacalix[4]arene of cone conformation behaves as "turn-on" optical chemosensor for Fe(3+) and F(-) ions. However, chemosensors 5 and 7 based on a thiacalix[4]arene of 1,3-alternate conformation demonstrate "turn-on" optical behaviour for Hg(2+), F(-) ions (with receptor 5 as turn-on for K(+) ions also) and "turn-off" behaviour for Fe(3+) ions. The simultaneous presence of Fe(3+) and Hg(2+) or K(+) or F(-) ions results in formulation of reversible "on-off" switches. Various molecular logic gates developed in response to molecular switching between these chemical inputs have been integrated into sequential logic circuits with memory function in a feedback loop which mimics "set-reset" molecular level information processing device.