Synthesis of pyrazolylbisindoles over mesoporous Lewis acidic ZrTUD-1: Potential application in selective Cu2+ colorimetric detection

• Series of pyrazolylbisindole derivatives was achieved using Lewis acidic Zr-TUD-1.
• Pyrazolylbisindole derivatives act as selective colorimetric chemosensor for Cu2+.
• The sensor formed new absorption band at 488 nm Cu2+ detectable by naked eye.

A series of pyrazolylbisindole (PBI) derivatives were prepared by simple condensation of indole and pyrazole aldehyde utilizing amorphous mesoporous ZrTUD-1 having predominant Lewis acid sites. The applicability of pyrazolylbisindolyl derivate as a colorimetric chemosensor with high selectivity toward Cu2+ over other cations were tested. Among heavy and transition metal (HTM) ions in CH3CN solution, the probe only sensed Cu2+ detectable by naked eye. The sensor exhibited a new absorption band at 488 nm (a red shift of 206 nm from 282 nm) with a large colorimetric response and affinity to Cu2+ over other cations tested (Al3+, Pb2+, Cd2+, Mg2+, Mn2+, Zn2+, K+, Fe2+, Ca2+, Cu2+ and Hg2+).

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