Near-Infrared-Absorbing B–N Lewis Pair-Functionalized Anthracenes: Electronic Structure Tuning, Conformational Isomerism, and Applications in Photothermal Cancer Therapy

Abstract

B–N-fused dianthracenylpyrazine derivatives are synthesized to generate new low gap chromophores. Photophysical and electrochemical, crystal packing, and theoretical studies have been performed. Two energetically similar conformers are identified by density functional theory calculations, showing that the core unit adopts a curved saddle-like shape (x-isomer) or a zig-zag conformation (z-isomer). In the solid state, the z-isomer is prevalent according to an X-ray crystal structure of a C6F5-substituted derivative (4-Pf), but variable-temperature nuclear magnetic resonance studies suggest a dynamic behavior in solution. B–N fusion results in a large decrease of the HOMO–LUMO gap and dramatically lowers the LUMO energy compared to the all-carbon analogues. 4-Pf in particular shows significant absorbance at greater than 700 nm while being almost transparent throughout the visible region. After encapsulation in the biodegradable polymer DSPE-mPEG2000, 4-Pf nanoparticles (4-Pf-NPs) exhibit good water solubility, high photostability, and an excellent photothermal conversion efficiency of ∼41.8%. 4-Pf-NPs are evaluated both in vitro and in vivo as photothermal therapeutic agents. These results uncover B–N Lewis pair functionalization of PAHs as a promising strategy toward new NIR-absorbing materials for photothermal applications.

An Easily Accessible NIR‐Absorbing Tetraimide Dye and its Biotherapeutics Based Photothermal and Photodynamic Therapy

“…The plot of ‐lnθ vs time shows good linear dependency and the estimated PTCE is 50.6 % for L‐2EHex‐B (0.02 mM) (Figure S12 and Section S4.8). Notably, the PTCE of L‐2EHex‐B is better than many small molecule‐based photosensitizers reported so far [4,9b] . L‐2EHex‐B also exhibits excellent photostability as evidenced by a consistent increase in temperature up to ten cycles [22] (Figures 5a and S13).…”

Amides as modifiable directing groups in electrophilic borylation

“…3 Recently, it has been demonstrated that directed electrophilic C–H borylation using BX 3 (X = Cl, Br or I) is a viable metal-free route to install useful boron units, such as BPin, onto arenes. 1 a ,4 However, this area is less developed than metal-catalysed directed C–H borylation, particularly regarding the utilisation of the directing group (DG) post borylation. To date, the DG is kept intact in the product post electrophilic borylation (Fig.…”

“…, BX 3 ) enabling subsequent access to a borenium cation (a three coordinate borocation) that then effects C–H borylation. 1 a ,4 Several DGs used in electrophilic borylation contain unsaturated units, e.g. , CO, and in the primary product formed post C–H borylation, e.g.…”

“…2 ), the DG remains bound to a Lewis acidic boron centre. 4 Thus, the DG will be activated, e.g. at the carbonyl carbon in B, towards reaction with nucleophiles.…”

Cove-region O-annulation of arylene diimide enables ambipolar transport of a polycyclic aromatic hydrocarbon with strong NIR absorption

“…Given its superb NIR absorption capability, we envisioned that O -ADA might also serve as a promising photothermal material. 19 Therefore, the photothermal conversion properties of the two PAHs were investigated under NIR laser radiation (808 nm) in the solid-state (Fig. S5d and S9, ESI†).…”