Expanding the polymethine paradigm: evidence for the contribution of a bis-dipolar electronic structure.

摘要: Although it has been reported in a few instances that the spectroscopic properties of cyanine dyes were strongly dependent on nature chemical substitution their central carbon atom, there not to date any systematic study specifically aimed at rationalizing this behavior. In article, such is carried out an extended family 17 polymethine carrying different substituents carbon, some those being synthesized for study, similar previously compounds, sake comparison. Their absorption properties, which spread over whole visible near-infrared spectral range, are seen be dramatically electron-donating character substituent. By correlating behavior NMR spectroscopy and (vibronic) TD-DFT calculations, we show results from profound modification ground state electronic configuration, namely, progressive localization cationic charge as substituent increased.