A highly selective and sensitive near-IR chemosensor having a chromenylium-cyanine backbone for the detection of Cu2+ in aqueous samples has been designed and synthesized. The sensor has exhibited linear optical response to copper ions at the range of 0-4.9 x 10(-6) M in the presence of other competing metal ions, such as Na+, K+, Mg2+, Ca2+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Zn2+, Al3+, Cd2+, Ag+, Sr2+, Pb2+, Hg2+ and Ba2+. The limit of detection (LOD) was calculated as 1.28 x 10(-8) M which was lower than that of previously reported analogues. The sensor allows detection of the copper(II) ion through the spirocyclic ring-opening reaction by coordination of Cu2+. (C) 2019 Elsevier B.V. All rights reserved.