Highly Selective Colorimetric Naked-Eye Cu(II) Detection Using an Azobenzene Chemosensor

<UFIGR ID="ol0498951n00001">Colorimetric azobenzene based chemosensors <BO>1</BO> and <BO>2</BO> were designed for detection of transition-metal ions such as Cu(II) under physiological pH conditions. The internal charge transfer (ICT) sensors are highly colored, absorbing in the green. For <BO>1</BO>, the Cu(II) recognition gives rise to red-to-yellow color changes that are visible to the naked-eye and reversible upon addition of EDTA, whereas for <BO>2</BO>, which lacks the aromatic o-methoxy chelating group, no such changes were observed.