Direct Iodination of Electron-Deficient Benzothiazoles: Rapid Access to Two-Photon Absorbing Fluorophores with Quadrupolar D-π-A-π-D Architecture and Tunable Heteroaromatic Core

Abstract

Direct iodination of benzothiazoles under strong oxidative/acidic conditions leads to a mixture of iodinated heteroarenes with 1-2 major components, which are easily separable and which structures depend on the I2 equivalents used. Among unexpected but dominant products were identified 4,7-diiodobenzothiazoles with a rare substitution pattern for SEAr reactions of this scaffold. These were employed in the synthesis of 4,7-bis(triarylamine-ethynyl)benzothiazoles  a new class of highly efficient quasiquadrupolar fluorophores displaying large two-photon absorption cross-sections (540−1374 GM) in the near-infrared region.

Derivatized Benzothiazoles as Two-Photon-Absorbing Organic Photosensitizers Active under Near Infrared Light Irradiation

“…Built upon the seminal works of Webb et al in designing and investigating organic TPA molecules and the recent development in this field, , we reasoned that organic molecules with prominent intra-molecular charge transfer are likely to exhibit appreciable two-photon absorption in the NIR region. Figure C presents the designer models of potential TPA molecules with non-centrosymmetric dipolar structures and centrosymmetric quadrupolar structures. − Encouraged by the recently reported results on benzothiazole-derived organic chromophores, which possess an excellent TPA cross section (σ 2 ) in the NIR region, − we were particularly interested in developing organic TPA photosensitizers consisting of a bibenzothiazole core as the electron acceptor, which is also conjugated with two terminal electron donors. Herein, we report the synthesis, characterization, and photophysical studies of two new benzothiazole-derived TPA photosensitizers, which can be successfully employed as photocatalysts in various organic reactions under NIR light (850 nm) irradiation.…”

Bromo‐Substituted Diazenyl‐pyrazolo[1,5‐a]pyrimidin‐2‐amines: Sonogashira Cross‐Coupling Reaction, Photophysical Properties, Bio‐interaction and HSA Light‐Up Sensor

“…This reaction has been used in various areas of chemistry, such as in synthesizing precursors for natural products, pharmaceuticals, agrochemicals, and developing molecular materials with optical and electronic properties (Figure 1). [3,5–10] …”

“…[2][3][4] This reaction has been used in various areas of chemistry, such as in synthesizing precursors for natural products, pharmaceuticals, agrochemicals, and developing molecular materials with optical and electronic properties (Figure 1). [3,[5][6][7][8][9][10] The catalytic system for this reaction has varied in the last three decades, depending on the nature of the substrate and the search for milder or more economical conditions. Numerous types of binders have been applied in this reaction type, including phosphines, carbenes, multidentate binders, palladium cycles, and non-binding versions.…”

Donor–Acceptor–Acceptor-Conjugated Dual-State Emissive Acrylonitriles: Investigating the Effect of Acceptor Unit Order and Biological Imaging

“…However, there has been an interest in finding how the acceptor positions affect the photophysical properties of D–A–A-structured molecules. Hrobárik et al reported several multipolar D–A–A dyes with regioisomeric control of their two-photon absorption or nonlinear optical properties by altering the relative position of the two acceptor units. − However, such a regioisomeric effect on D–A–A dyes still needs further investigations. Therefore, changing the relative position of acceptor units for D–A–A fluorescent dyes is crucial to have desirable photophysical properties.…”