A novel polymeric chemosensor: dual colorimetric detection of metal ions through click synthesis.

A highly colored polystyrene derivative bearing side chain chromophores composed of dialkylanilino donor and cyano-based acceptor groups, prepared by atom-economic click postfunctionalization, displays the dual colorimetric detection behavior of several metal ions based on the specific interactions with different nitrogen atoms. Hard to borderline metal ions, such as Fe(3+) , Fe(2+) , and Sn(2+) , are always recognized by the dialkylanilino nitrogen atom, resulting in a decrease in the charge-transfer (CT) band intensity of the donor-acceptor chromophores. On the other hand, the recognition site of a soft metal ion of Ag(+) is the cyano nitrogen atom due to the readily formed multivalent coordination, which produces a bathochromic shift of the CT band.