Host-guest interaction aided Zinc carry and delivery by ESIPT active 2-(2′-hydroxyphenyl)benzoxazole

Abstract

The effect of solvents and supramolecular hosts on the binding of metal ion with an excited state intramolecular proton transfer (ESIPT) active fluorophore 2-(2′-hydroxyphenyl)benzoxazole (HPBO) are investigated to scrutinize a possible metal ion carry and delivery system. The fluorophore forms strong fluorescent complex with Zn2+ ion. In aqueous medium, β-cyclodextrin (β-CD) breaks the HPBO–Zn2+ complex and encapsulate the freed fluorophore. Hence, the initially blocked ESIPT process is restored by forming an inclusion complex with the host molecules. However, in dimethyl sulphoxide (DMSO), β-CD does not break the complex. But cucurbit[7]uril (CB-7) breaks the complex in both DMSO and water. The tuned emission characteristics are considered for constructing different molecular logic gates. BUFFER, NOT, PASS, IMPLICATION and INHIBIT logic operations are substantiated based on Zn2+, CB-7 and β-CD response.