A　series　of　sulfonamido-substituted　phenylethylidene-3,4-dihydro-1H-quinoxalin-2-one　derivatives　in　which　both　of　the　fluorophore　and　ionophore　are　integrated　into　one　structural　unit,　have　been　investigated.　They　all　exhibit　high　selectivity　toward　Cu2+　in　ethanol　in　the　presence　of　other　metallic　ions　(Zn2+,　Mg2+,　Co2+,　Ni2+,　Mn2+,　Ca2+,　and　Ag+),　as　well　as　fast,　stable,　and　reversible　binding,　as　is　evidenced　by　the　observation　of　a　red　shift　in　the　UV-vis　spectrum,　＇ON-OFF＇　fluorescence　response.　In　addition,　titration　and　MALDI-TOF　measurements　indicated　that　a　1:1　(and　possibly　also　2:1　(organic　ligand:　Cu2+)　complexes　were　formed,　depending　on　the　relative　amount　of　Cu2+　added　to　the　solution　of　the　organic　ligand.　It　was　also　found　that　the　binding　constant　could　be　tuned　by　modifying　the　nature　and　position　of　the　substituents　attached　to　the　central　benzene　ring　in　the　quinoxalone　derivative.　In　acetonitrile,　unlike　in　ethanol,　these　ligands　undergo　oxidation-decomposition　by　Cu2+　and　therefore,　no　UV-vVis　absorption　bands　could　be　observed.　However,　due　to　color　change　(from　yellow　to　transparent)　they　could　be　useful　as　dosimeters　in　this　solvent.　(C)　2011　Elsevier　Ltd.　All　rights　reserved.