TY - JOUR
T1 - Indolizine–Squaraines
T2 - NIR Fluorescent Materials with Molecularly Engineered Stokes Shifts
AU - McNamara, Louis E.
AU - Rill, Tana A.
AU - Huckaba, Aron J.
AU - Ganeshraj, Vigneshraja
AU - Gayton, Jacqueline
AU - Nelson, Rachael A.
AU - Sharpe, Emily Anne
AU - Dass, Amala
AU - Hammer, Nathan I.
AU - Delcamp, Jared H.
N1 - Publisher Copyright:
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2017/9/12
Y1 - 2017/9/12
N2 - The development of deep red and near infrared emissive materials with high quantum yields is an important challenge. Several classes of squaraine dyes have demonstrated high quantum yields, but require significantly red-shifted absorptions to access the NIR window. Additionally, squaraine dyes have typically shown narrow Stokes shifts, which limits their use in living biological imaging applications due to dye emission interference with the light source. Through the incorporation of indolizine heterocycles we have synthesized novel indolizine squaraine dyes with increased Stokes shifts (up to >0.119 eV, >50 nm increase) and absorptions substantially further into the NIR region than an indoline squaraine benchmark (726 nm versus 659 nm absorption maxima). These materials have shown significantly enhanced water solubility, which is unique for squaraine dyes without water-solubilizing substituents. Absorption, electrochemical, computational, and fluorescence studies were undertaken and exceptional fluorescence quantum yields of up 12 % were observed with emission curves extending beyond 850 nm.
AB - The development of deep red and near infrared emissive materials with high quantum yields is an important challenge. Several classes of squaraine dyes have demonstrated high quantum yields, but require significantly red-shifted absorptions to access the NIR window. Additionally, squaraine dyes have typically shown narrow Stokes shifts, which limits their use in living biological imaging applications due to dye emission interference with the light source. Through the incorporation of indolizine heterocycles we have synthesized novel indolizine squaraine dyes with increased Stokes shifts (up to >0.119 eV, >50 nm increase) and absorptions substantially further into the NIR region than an indoline squaraine benchmark (726 nm versus 659 nm absorption maxima). These materials have shown significantly enhanced water solubility, which is unique for squaraine dyes without water-solubilizing substituents. Absorption, electrochemical, computational, and fluorescence studies were undertaken and exceptional fluorescence quantum yields of up 12 % were observed with emission curves extending beyond 850 nm.
KW - NIR dyes
KW - emissive materials
KW - fluorescence quantum yield
KW - indolizine
KW - squaraine
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U2 - 10.1002/chem.201702209
DO - 10.1002/chem.201702209
M3 - Article
C2 - 28699321
AN - SCOPUS:85029211306
SN - 0947-6539
VL - 23
SP - 12494
EP - 12501
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 51
ER -