No abstract

A new class of 2,6-bis(2-anilinoethynyl)pyridine-based bisureas forms 1 : 1 complexes with halides; protonation enhances binding by over one order of magnitude, alters the binding selectivity, and provides a colorimetric indication of anion binding.

A new phenyl-acetylene receptor containing a carbonaceous hydrogen bond donor activates anion binding in conjunction with two stabilizing ureas. The unusual CH···Cl– hydrogen bond is apparent in solution by large 1H NMR chemical shifts and by a short, linear contact in the solid state.

Urea and sulfonamide derivatives of 1 exhibit ON-OFF and OFF-ON switchable fluorescent and colorimetric responses upon protonation. The magnitude of the fluorescence event is dictated by the anion, resulting in a rare, fully organic “turn-on” fluorescent sensor for chloride.