Indole based push-pull dyes bearing azo and dimethine: Synthesis, spectroscopic, NLO, anion affinity properties and thermal characterization

[Display omitted] •A series of novel chromophores containing azo and dimethine were synthesized in high yield.•The synthesized dyes showed colorimetric change towards F−, AcO−, CN−, and H2PO4− anions.•The dyes have highly selectivity to CN− anion in ACN:Water (9:1) and DMSO:Water (8:2) binary mixtures.•The proposed sensing mechanisms were explained by DFT and 1H-NMR studies. A series of novel indole based push-pull dyes bearing azo and dimethine chromophores in same structure were synthesized and characterized by Fourier Transform Infrared (FT-IR), 1H/13C nuclear magnetic resonance (NMR), and mass spectrometry. The photophysical properties of the dyes were determined in three solvents in UV–vis and theoretical studies. Their chemosensor and nonlinear optic (NLO) properties were also investigated. Anion selectivity and sensitivities of dyes were studied with some selected anions in ACN and interaction mechanisms were confirmed by spectrophotometric and 1H NMR titration techniques. While the dyes showed affinity to F−, AcO−, CN−, and H2PO4− in the organic solvents such as DMSO and ACN and they showed selective behaviour only to CN- in partial aqueous solution. The thermal stabilities obtaining with thermogravimetric analysis (TGA) showed that the dyes have a good thermal stability up to around 300 °C.