Two new two-photon absorbing near-infrared (NIR) emitting 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivatives, DDC and SDC, were designed for one- and two-photon fluorescence microscopy imaging. Linear and nonlinear photophysical properties, including UV/Vis absorption, fluorescence, excitation anisotropy, photostability, and two-photon absorption cross sections, of the dyes were investigated to assess the potential of using the new probes as bioimaging agents. Cell viability and colocalization studies of DDC with Lysotracker Red, in COS 7 and HCT 116 cells demonstrated not only low toxicity but also selective targeting of lysosomes. SDC was encapsulated in silica-based nanoparticles for in vitro and ex vivo fluorescence bioimaging. The nanoparticles were modified with an RGD peptide to target α_Vβ₃ integrin. The nanoprobe exhibited good biocompatibility and highly selective uptake in α_Vβ₃ integrin-overexpressing cancers.

A new ladder-conjugated star-shaped oligomer electron-transporting material TetraPDI-PF, with four perylene diimide (PDI) branches and a fluorene core, was efficiently synthesized. The oligomer is highly soluble in dichlorobenzene with a solubility of 155 mg mL⁻¹, which is higher than those of PDI (35 mg mL⁻¹) and PDI-Phen (70 mg mL⁻¹). Demonstrated by thermogravimetric analysis (TGA), the oligomer exhibits excellent thermal stability with the decomposition temperature (T_d) of 291.2 °C, which is 65 °C higher than that of PDI. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed to investigate the electrochemical properties. Although the CV curves of TetraPDI-PF are successively scanned for 15 cycles, they still remain invariable reduction potentials. The oligomer also shows outstanding photostability, even better than PDI, which maintains 99 % fluorescence intensity after irradiation for 10 min using maximum laser intensity. In the steady-state space-charge-limited current (SCLC) devices, TetraPDI-PF exhibits higher intrinsic electron mobility of 2.22×10⁻⁵ cm² V⁻¹ s⁻¹, three orders of magnitude over that of PDI (3.52×10⁻⁸ cm² V⁻¹ s⁻¹). The bulk heterojunction (BHJ) organic solar cells (OSCs) using TetraPDI-PF as non-fullerene acceptors and P3HT as donors give optimum power conversion efficiency (PCE) of 0.64 %, which is 64 times that of the PDI:P3HT BHJ cells.

Herein, we present the synthetic route and the photophysical, electrochemical as well as laser properties of novel red-emitting boron-dipyrromethenes (BODIPYs) bearing arylethyne moieties. Such functionality is added along the main axis of the chromophore leading to single- and double-substituted derivatives. The relationship between the dye structure and the lasing properties is studied in detail with the help of the photophysical and electrochemical properties as well as quantum mechanical simulations. The asymmetric substitution of the parent dye induces inhomogeneities in the charge distribution, which leads to an overall loss of the fluorescence capacity, mainly in polar media. Such non-radiative deactivation processes can be softened by decreasing the electron-donor ability of the substituent or even avoided by symmetrical substitution. Thus, grafting of the arylethyne moieties at the longitudinal axis of the indacene core results in an effective strategy to develop red-edge BODIPYs with highly efficient and photostable laser emission.

We have connected a borondipyrromethene (BODIPY) donor to the 5′ position of a tetramethylrhodamine (TMR) acceptor to form a high efficiency (over 99 %) intramolecular fluorescence resonance energy transfer (FRET) cassette, BODIPY–rhodamine platform (BRP). While the good spectral overlap between the emission of BODIPY and the absorption of TMR was one favorable factor, another feature of this FRET system was the rigid and short biphenyl spacer that favored efficient through-bond energy transfer. More importantly, in this system, the 2′-carboxyl group of the rhodamine unit was preserved for the further modifications, which was as convenient as those carbonyl groups on the original rhodamines without connection to donors. For this reason, BRP is clearly differentiated from the previous ratiometric sensors based on donor rhodamine systems. To illustrate its value as a versatile platform, we introduced typical Hg²⁺ receptors into BRP, through convenient one-pot reactions on the 2′-carboxyl group, and successfully developed two ratiometric sensors, BRP-1 and BRP-2, with different spirocyclic receptors that recognized Hg²⁺ on different reaction mechanisms. Upon excitation at a single wavelength (488 nm), at which only BODIPY absorbed, both of the FRET sensors exhibited clear Hg²⁺-induced changes in the intensity ratio of the two strong emission bands of BODIPY and rhodamine. It should be noted that these ratiometric Hg²⁺ sensors exhibited excellent sensitivity and selectivity Hg²⁺, as well as pH insensitivity, which was similar to the corresponding ‘turn-on’ rhodamine sensors. While both ratiometric probes were applicable for Hg²⁺ imaging in living cells, BRP-1 exhibited higher sensitivity and faster responses than BRP-2. Our investigation indicated that on a versatile platform, such as BRP, a large number of highly efficient ratiometric sensors for transition-metal ions could be conveniently developed.