Al3+ selective an efficient colorimetric receptor derived from 5-aminouracil

An interference-free naked-eye recognition of Al3+ at its micromolar level has been done in 5% aqueous DMSO solution employing a Schiff base 5-[(2-hydroxy-5-nitro-benzylidene)-amino]-1H-pyrimidine-2,4-dione (receptor 1) which is an intramolecular charge transfer (ICT) probe. The pyrimidine and nitrophenyl groups serve as electron rich (donor) and deficient (acceptor) pockets in receptor 1 exhibiting a broad ICT band at 434 nm (olive green). The concomitant additions of Al3+ as its chloride salt to the 5 × 10−5 M aqueous DMSO solution of the receptor 1 lead hypsochromic shifting of its ICT band to 395 nm (colorless). The same ICT band undergoes a marginal bathochromic shifting (6 nm) along with a hyperchromic shift on separate additions of a basic anion like F−, CH3COO− and H2PO4− to the receptor 1 and faced almost similar fate on concomitant additions of Al3+ as mentioned above.