Colorimetric probes based on bioactive organic dyes for selective sensing of cyanide and fluoride ions

• Eight novel azo dyes containing thiazolidinones are synthesized and fully characterized.
• The solvatochromic properties of dyes evaluated in the solvents with different polarity.
• Probe 4O can be utilized as a colorimetric chemosensor for detection of CN− or F− ions.
• Antibacterial activities of compounds were investigated.

Eight novel bioactive azo dyes containing thiazolidinone (TZD) derivatives (1O–4S) were designed and synthesized for antibacterial assays and colorimetric sensing of anions. Synthesized compounds were evaluated for their antibacterial activities using the disc diffusion technique. Majority of the compounds showed potent antibacterial activities against the tested bacterial strains in the zone assay. Moderate antibacterial activities were also exhibited in the minimum inhibitory concentration (MIC) assay. In addition, the synthesized compounds were evaluated for their colorimetric sensing of anions. In contrast to dyes with electron donating groups (EDGs), 4O having electron withdrawing groups (EWGs) showed highly selective colorimetric sensing of CN− ions. Binding interaction of 4O with CN− ions provides a remarkable colorimetric response from yellow to blue (Δλ = 186 nm), enabling naked-eye sensing without any spectroscopic instrumentation. Furthermore, the limit of detection (LOD) for 4O towards CN− was found to be 0.74 μM.

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