Akhil Kumar, M.M.Dhawale, A.Trivedi, D.R.2026-02-032025Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy, 2025, 326, , pp. -13861425https://doi.org/10.1016/j.saa.2024.125273https://idr.nitk.ac.in/handle/123456789/20423A simple and highly sensitive isatin-based colorimetric sensor ISAT 3(a-d) was synthesized through a single-step reaction. The as-prepared receptor ISAT 3b with carbonate ions (CO<inf>3</inf>2? ions) shows a significant red shift in the UV–visible absorption spectra and a visible color change from pale yellow to pink. Also, the receptor ISAT 3b shows unique solvatochromic behavior with CO<inf>3</inf>2? ions in different aprotic solvents and solvent compositions. Moreover, the receptor's pink coloration (absorption maxima at 544 nm) with CO<inf>3</inf>2? ions could be reversible by adding HSO<inf>4</inf>? ions (attain initial pale-yellow color, absorption maxima at 425 nm), which can be repeatable. The observed color changes with spectral shift and reversibility of the receptor with CO<inf>3</inf>2? ions and HSO<inf>4</inf>? ions provide “ON-OFF” switching for applying molecular logic gates. Receptors exhibited properties, such as reversibility and repeatability, benefit the design of a molecular-scale sequential memory unit with a display of “Writing-Reading-Erasing-Reading”. The real sample analysis was also carried out to prove the practical applicability of receptor (ISAT 3b) for detecting CO<inf>3</inf>2? ions. © 2024 Elsevier B.V.Canal gatesCarbonationChemical sensorsColorimetersColorimetric analysisColorimetryMolecular dockingNegative ionsRed ShiftAbsorption maximaCarbonate ionsCarbonate sensorColorimetric sensorsIsatinITS applicationsMemory unitsMolecular scaleRational designSolvatochromicLogic gatescarbonic acidionisatinsolventabsorptionarticlecolorcontrolled studydrug analysismemoryultraviolet radiation