Unveiling the photophysical and morphological properties of an acidochromic thiophene flanked dipyrrolopyrazine-based chromophore for optoelectronic application.

A series of dipyrrolopyrazine (DPP) based chromophores featuring thiophene and varied donor (N,N-dimethylamine, NH2, OMe) and acceptor (CF3, CN, NO2) appendages have been synthesized. The structures and properties of the chromophores were investigated by absorption spectroscopy, electrochemistry, differential scanning calorimetry, and thermogravimetric analysis. X-ray crystallographic analysis indicates a planar geometry for the molecule 7g. Surface morphological studies reveal the formation of microrods and nanorods. The acidochromic behavior of the chromophore which shows a prominent red-shift in the absorption spectra owing to the protonation of the pyrazine segment provides a valuable opportunity to assess the sensory response. Acid dependent spectral changes could be successfully applied to detect pH in biological fluids and acid impurities in solvents.