TY - JOUR
T1 - Synthesis and spectral properties of near-infrared cyanine dyes showing enhanced Stokes shift
T2 - A paradigm of ICT dipolar state polymethine chromophoric systems
AU - Kurutos, Atanas
AU - Citterio, Daniel
N1 - Funding Information:
6b shows a featureless broad single peak in all solvents. Intriguingly, 6c features a red-shifted shoulder in most solvents with exception for the two low polarity solvents. Mulliken assigned similar shoulders for polyenes to C-C stretch vibrations. In the reports he has explained how any low-frequency deformations of a planar polyene could eventually account for the enhanced Stokes shift and band broadening [55–57] . This assumption was also supported by other research groups [ 58 , 59 ].
Publisher Copyright:
© 2021 Elsevier B.V.
PY - 2022/1/5
Y1 - 2022/1/5
N2 - Three benzothiazole-derived heptamethine cyanine dyes were prepared via nucleophilic substitution at meso-position along the polymethine backbone. The synthetic route to the title polymethines includes a total of four steps starting from inexpensive commercially available materials. Structural elucidation of the newly synthesized chromophores was achieved using 1H-NMR, 13C-NMR and high-resolution mass spectrometry (HRMS) in ESI mode. Current functionalized amino-derived NIR dyes exhibit significant Stokes shift (Δν up to 1835 cm−1, 108 nm) compared to the parent unsubstituted chromophore (Δν = 303 cm−1, 23 nm). The probability of solvatochromism was determined from the correlation between the Stokes shift against the Dimroth-Reichardt ET (30) and the Lippert–Mataga function (ΔfLM) of orientation polarizability. Based on the experimental findings, this large Stokes shift presumably reflects a solvatochromic intramolecular charge transfer (ICT) across the molecule, which is induced by the introduced secondary amine.
AB - Three benzothiazole-derived heptamethine cyanine dyes were prepared via nucleophilic substitution at meso-position along the polymethine backbone. The synthetic route to the title polymethines includes a total of four steps starting from inexpensive commercially available materials. Structural elucidation of the newly synthesized chromophores was achieved using 1H-NMR, 13C-NMR and high-resolution mass spectrometry (HRMS) in ESI mode. Current functionalized amino-derived NIR dyes exhibit significant Stokes shift (Δν up to 1835 cm−1, 108 nm) compared to the parent unsubstituted chromophore (Δν = 303 cm−1, 23 nm). The probability of solvatochromism was determined from the correlation between the Stokes shift against the Dimroth-Reichardt ET (30) and the Lippert–Mataga function (ΔfLM) of orientation polarizability. Based on the experimental findings, this large Stokes shift presumably reflects a solvatochromic intramolecular charge transfer (ICT) across the molecule, which is induced by the introduced secondary amine.
KW - Intramolecular charge transfer
KW - Meso-substituted heptamethine dyes
KW - NIR chromophores
KW - Optical spectroscopy
KW - Solvatochromism
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U2 - 10.1016/j.molstruc.2021.131381
DO - 10.1016/j.molstruc.2021.131381
M3 - Article
AN - SCOPUS:85114160717
SN - 0022-2860
VL - 1247
JO - Journal of Molecular Structure
JF - Journal of Molecular Structure
M1 - 131381
ER -