Wide-Range Near-Infrared Sensitizing 1H-Benzo[c,d]indol-2-ylidene-Based Squaraine Dyes for Dye-Sensitized Solar Cells

Small-Molecule Phototheranostic Agent with Extended π-Conjugation for Efficient NIR-II Photoacoustic-Imaging-Guided Photothermal Therapy

Photoacoustic imaging (PAI) and photothermal therapy (PTT) conducted over the near-infrared-II (NIR-II) window offer the benefits of noninvasiveness and deep tissue penetration. This necessitates the development of highly effective therapeutic agents with NIR-II photoresponsivity. Currently, the predominant organic diagnostic agents used in NIR-II PAI-guided PTT are conjugated polymeric materials. However, they exhibit a low in vivo clearance rate and long-term biotoxicity, limiting their clinical translation. In this study, an organic small molecule (CY-1234) with NIR-II absorption and nanoencapsulation (CY-1234 nanoparticles (NPs)) for PAI-guided PTT is reported. Extended π-conjugation is achieved in the molecule by introducing donor-acceptor units at both ends of the molecule. Consequently, CY-1234 exhibits a maximum absorption peak at 1234 nm in tetrahydrofuran. Nanoaggregates of CY-1234 are synthesized via F-127 encapsulation. They exhibit an excellent photothermal conversion efficiency of 76.01% upon NIR-II light irradiation. After intravenous injection of CY-1234 NPs into tumor-bearing mice, strong PA signals and excellent tumor ablation are observed under 1064 nm laser irradiation. This preliminary study can pave the way for the development of small-molecule organic nanoformulations for future clinical applications.

Synthesis of near-infrared absorbing and fluorescent bis(pyrrol-2-yl)squaraines and their halochromic properties

1,2-Squaraines (partially conjugated neutral structure) showed blue-shifted λmax compared to the corresponding 1,3-squaraines (fully conjugated zwitterionic structure) and the mono-protonated thiophene-fused 1,3-squaraine showed λmax at 1007 nm.

Extended conjugation in stilbenoid squaraines

Squaraines, two-fold condensation products in 1,3-position of squaric acid, represent dyes or pigments of high actuality. After their first boom in electrophotography diverse applications are presently studied in a wide area of research, which reaches from electrooptical materials to biosensors and compounds used in photodynamic therapy. Absorption and/or emission ranges in the NIR are mandatory for many of these techniques. The present article deals with stilbenoid squaraines, which feature an extended conjugation in their biradicaloid D-π-A-π-D structure. Due to the charge-transfer character of the excitation, boundaries are set for the optimal length of the conjugation. The absorption maxima of the stilbenoid squaraines and their aggregates are lying in chloroform as a solvent between 600 and 1000 nm. In the solid state panchromatic absorptions can be observed, which reach far into the NIR region. The facile preparation of squaraines bearing stilbene building blocks in one or two of their arms and moreover the easy access to dyes with multiple squaraine units fixed to stilbenoid scaffolds promise a wide palette of further applications in materials science.

Thermo- and photo-stable symmetrical benzo[cd]indolenyl-substituted heptamethine cyanine dye carrying a tetrakis(pentafluorophenyl)borate that absorbs only near-infrared light over 1000 nm

Thermo- and photo-stable NIR dyes absorbing only NIR light of over 1000 nm have been investigated.

Synthesis of near-infrared absorbing and fluorescing thiophene-fused BODIPY dyes with strong electron-donating groups and their application in dye-sensitised solar cells

Thiophene-fused BODIPY dyes with two diethylaminophenyl groups as strong donors demonstrated near-infrared (NIR) absorption (λ_max: 783–812 nm, ε: 119 500–145 900) and fluorescence (F_max: 862–916 nm, Φ_f: 0.02–0.12) in dichloromethane.