Synthesis and spectral properties of near-IR polymethine dyes derived from tris(2,2,3,3,4,4,5,5-octafluoropenty1)-9H-fluorene-2,4,7-trisulfonate

A vinylogous series of anionic polymethine (cyanine) dyes has been synthesized based on tris(2,2,3,3,4,4,5,5-octafluoropentyI)-9H-fluorene-2,4,7-trisulfonate. It has been found that their longest wavelength and most intense electronic transition has the polymethinic origin, unlike the analogous polynitrofluorene dyes. As established, the corresponding absorption band, in contrast to that of classical cyanines, remains quite intense and narrow in the near-IR spectral region even in highly polar solvents. The nature of electronic transitions and relevant molecular orbitals as well as excitation-induced electron density redistributions have been studied by the DFT and TDDFT methods at the GAM-B3LYP/6-31G(d,p) level. (C) 2017 Elsevier Ltd. All rights reserved.