In previous studies, hydrazide ligands such as 1a were found to bind Al3+ in aqueous/organic solutions, giving large fluorescence turn-on response by forming complex 2. In order to further examine the potential of the ligand system, we synthesized the additional hydrazide ligands 1b and 1c. However, the binding of hydrazides 1b and 1c with Al3+ did not completely give complexes 2, but rather produced 3 as a major product after removing solvent (scheme 1). The structure of 3 was confirmed via X-ray crystallography, NMR, UV-vis and fluorescence spectroscopy. Formation of 3 revealed that sensing aluminum (III) cation with hydrazide ligands 1 could involve a more complicated pattern than one initially assumed. An interesting question is how much of 1 is converted to 3, which is contributing to the emission observed with 2? As we investigated the conversion mechanism from 1 to 3, it was discovered that the material might undergo a reaction similar to a metal catalyzed Mannich reaction.

Aluminum (III)-catalyzed synthesis of symmetrical Schiff base for aluminum sensor

254th National Meeting (2017)

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