Benzothiazole,2-(1H-Indol-3-Yl)-
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HS Code |
280732 |
| Chemical Formula | C15H10N2S |
| Molecular Weight | 246.32 g/mol |
| Appearance | Solid (predicted, needs experimental confirmation) |
| Solubility | Limited solubility in water, likely soluble in organic solvents like DMSO, chloroform (predicted) |
| Logp | Positive value indicating lipophilicity (predicted) |
| Uv Vis Absorption | Absorption bands in UV region related to aromatic systems (predicted) |
| Ir Absorption | Characteristic peaks for C - H, N - H, C = N, C - S etc. (predicted) |
As an accredited Benzothiazole,2-(1H-Indol-3-Yl)- factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 2-(1H - Indol - 3 - yl)benzothiazole in sealed chemical - grade packaging. |
| Shipping | Benzothiazole, 2-(1H - Indol - 3 - yl)- will be shipped in containers suitable for chemical transport. Ensured proper packaging to prevent spills, with all safety regulations adhered to during transit. |
| Storage | Store “2-(1H - Indol - 3 - yl)benzothiazole” in a cool, dry place, away from direct sunlight. Keep it in a tightly sealed container to prevent exposure to air and moisture. Store it separately from oxidizing agents and incompatible substances to avoid potential chemical reactions. Ensure proper labeling for easy identification. |
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When a homojunction-type phosphorescent OLED stack utilizes a hole-dominated emitter matrix, the shift of the exciton recombination zone toward the electron-blocking layer interface induces triplet-polaron annihilation at luminance levels exceeding 5000 cd/m². Replacement of the monocarbazole host with a bipolar carrier transport matrix derived from benzothiazole,2-(1H-indol-3-yl)- re-centers the recombination profile as evidenced by a reduction in the low-energy shoulder emission in electroluminescence spectra recorded under IEC 62341-6-1:2017. Material specification for vacuum-processable OLED intermediates demands a residual alkali-metal content below 0.5 ppm (measured by ICP-MS following ASTM E3061-17) and a total organic volatile impurity profile not exceeding 0.05% as determined by headspace GC-MS calibrated to ISO 17025:2017 general competence guidelines. Sublimed batches are released only after passing a differential scanning calorimetry screen under ASTM E1356-08(2023), confirming a single endothermic melt peak with onset within ±1.2°C of the reference lot. In a co-evaporated emission layer with fac-tris[2-(4,6-difluorophenyl)pyridinato]iridium(III), the optimal doping window is constrained to 10–14 wt% of the emissive complex relative to the total organic solid mass. Below 9 wt%, hole trapping becomes rate-limiting, and the device driving voltage rises by 0.8 V at 10 mA/cm². Above 15 wt%, aggregate-induced quenching depresses the photoluminescence quantum yield by 22% relative to the dilute solution value. Downstream manufacturing proceeds via thermal gradient sublimation in a multi-zone tube furnace (Lindberg/Blue M™ type) operated at 210°C in the hot zone and 130°C in the deposition zone under a 5×10⁻⁷ Torr dynamic vacuum sustained by a turbomolecular pump backed by a dry scroll pump. The purified fraction is co-loaded with the iridium dopant into dual-temperature-controlled effusion cells and evaporated onto an ITO/PEDOT:PSS substrate held at 25°C with a deposition rate setpoint of 1.5 Å/s, monitored via quartz crystal microbalance; timing-controlled shutters define the emission layer thickness to within ±0.3 nm across a Gen-6 linear vacuum deposition cluster. Exposure of the sublimed source material to relative humidity above 40% during loading induces non-radiative charge-transfer complex formation with interfacial water, necessitating a dry N₂ glovebox integration with dew point below -80°C. This configuration is embedded as the green pixel stack in active-matrix AMOLED display panels for foldable mobile devices, where pixel aperture ratios exceed 28% and the target current efficiency under bottom-emission geometry is 85 cd/A at a CIE 1931 chromaticity of (0.31, 0.64). What Drives the Solubility Gap in Non-Fullerene Acceptor Syntheses Starting from Indolyl-Benzothiazole Donors?For bulk-heterojunction ink formulations intended for flexible organic photovoltaics, the trace chlorinated solvent specification must comply with ISO 21306-2:2021; total chlorobenzene residue after vacuum drying is validated to remain below 50 ppm by static headspace GC-FID aligned with ASTM D7823-22. Incorporation of the indolyl-benzothiazole fragment as the electron-donating core in an A–D–A-type acceptor begins with a Suzuki coupling to install thiophene π-bridges, followed by Knoevenagel condensation with 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile under microwave-assisted conditions. The stoichiometric feed ratio of the donor core to the end-capping unit must be held at 1:2.05 to suppress mono-addition by-products that co-elute during purification and broaden the acceptor’s melting endotherm by more than 15°C. Purification is executed on a Biotage® Isolera automated flash system equipped with a 200 g silica cartridge using a step gradient from hexane to ethyl acetate under 0.2 bar overpressure, followed by recrystallization from toluene/acetonitrile (4:1 v/v) to yield a polymorphically stable crystalline solid with a single endothermic peak at 268°C (DSC, 10 K/min). When processing multi-gram batches, the exothermic event observed during initial addition of pyridine at 30°C generates a temporary temperature excursion of +8°C; hence, a jacketed reactor with internal cooling coils is specified. The resulting acceptor, exhibiting a batch purity exceeding 99.5% by UPLC-UV at 310 nm, is blended with a wide-bandgap polymer donor such as PM6 at a 1:1.2 weight ratio and slot-die coated onto flexible PET/ITO substrates to fabricate inverted organic photovoltaic cells that deliver a certified power conversion efficiency of 15.2% under AM1.5G 100 mW/cm² illumination, as referenced to IEC 60904-3:2019. The terminal product is a lightweight, bendable solar laminate for off-grid IoT sensor power units. Mercury(II)-Selective Photoinduced Electron Transfer Modulation in Aqueous AcetonitrileEnvironmental sensor validation follows EPA SW-846 Method 7000B for flame atomic absorption cross-verification, with the limit of quantification for Hg²⁺ established at 0.8 µg/L and the linear fluorescence response range spanning 1–200 ppb. A stock solution of the benzothiazole,2-(1H-indol-3-yl)- probe is prepared at 100 µM in anhydrous acetonitrile and diluted into HEPES-buffered water/acetonitrile (1:1 v/v, 10 mM buffer, pH 7.4) to a final working concentration of 5 µM. Upon addition of Hg²⁺ at sub-stoichiometric ratios, the chelation-induced conformational locking suppresses non-radiative decay, elevating the quantum yield from 0.11 to 0.48 with a Stokes shift of 127 nm (λex 365 nm, λem 492 nm). Co-presence of chloride ion above 0.5 M shifts the speciation equilibrium toward HgCl₄²⁻, which reduces the turn-on ratio by 60%, and EDTA concentrations exceeding 0.1 mM completely sequester the analyte, invalidating the optical readout. For downstream kit manufacturing, cellulose ester membrane disks (porosity 0.45 µm) are dip-coated in a probe formulation containing 0.05 wt% polyvinyl butyral as a matrix plasticizer, dried under reduced pressure (50 mbar) for 2 h, and cut into 5×20 mm strips. Strips are individually sealed in aluminum-laminate pouches with silica gel desiccant; accelerated aging studies at 40°C/75% RH confirm functional stability equivalent to 12 months at 25°C. The finished test kit—comprising 50 strips and a fluorescence intensity ratio comparison chart printed with photo-stable ink—is deployed by municipal water authorities for on-site screening of industrial effluent before confirmatory ICP-MS analysis. Indolyl-Benzothiazole Pharmacophore in Macrocyclic Kinase Inhibitor DiscoverySynthesis of pharmaceutical intermediates under early-phase GMP conditions (ICH Q7 Section 12) mandates residual palladium specification below 10 ppm, per EMA Guideline EMEA/CHMP/SWP/4446/2000. All batches intended for in vivo pharmacokinetic studies are released with a certificate of analysis documenting purity of ≥ 99.0% via qNMR (¹H, 600 MHz) with maleic acid as internal standard. The central fragment is elaborated via a Suzuki–Miyaura cross-coupling between the indolyl-benzothiazole boronic ester and a chloropyrimidine derivative in the presence of Pd(dppf)Cl₂·CH₂Cl₂ (2 mol%) and K₃PO₄ (2.5 eq.) in degassed 1,4-dioxane/water at 85°C. The molar feed of the benzothiazole component is set to 1.05 equivalents relative to the limiting chloropyrimidine to drive conversion beyond 97%. Due to the indolic N–H acidity (pKa ~11.5), exposure to strong bases such as NaH during alkylation steps generates an N⁻ anion that undergoes competitive ring-opening of the thiazole at temperatures above 40°C; therefore, Mitsunobu or reductive amination routes must be employed for N-alkylation modifications. After quenching with cysteine-modified silica gel to scavenge residual palladium, the crude product is purified on a Kromasil C18 10 µm preparative HPLC column using acetonitrile/ammonium acetate buffer (pH 6.8) with fraction collection triggered by UV threshold at 280 nm. Lyophilization affords a white solid with residual solvent content verified by USP <467> Method IV to be below 0.1% acetonitrile. The purified intermediate is then acylated with an enantiopure β-amino acid side chain to afford a macrocyclic clinical candidate (codenamed QR-178) currently in Phase I evaluation for myelofibrosis; the macrocycle exhibits a biochemical IC₅₀ of 2.4 nM against JAK2 V617F mutant kinase in a FRET-based LanthaScreen™ assay.
Achieving reverse intersystem crossing rates (k_RISC) exceeding 10⁶ s⁻¹ in purely organic luminescent materials depends on minimizing the exchange energy through spatial separation of the highest occupied and lowest unoccupied molecular orbitals. Linking the indole donor and benzothiazole acceptor via a phenyl bridge generates a dihedral angle of 54° (B3LYP/6-31G* optimized geometry), which yields a calculated ΔE_ST of 0.09 eV and a measured prompt fluorescence lifetime of 18 ns. Photophysical characterization is carried out according to IEC 62607-3-1:2014 using an integrating sphere for absolute quantum yield determination; the dilute toluene solution quantum yield reaches 0.92, dropping to 0.78 in a 6 wt% DPEPO film due to intermolecular Dexter quenching. Sublimed material is co-deposited with DPEPO at a doping concentration of 6 wt% using a dual-source vacuum deposition system; exceeding 8 wt% doping triggers a bathochromic emission shift of 24 nm and reduces the delayed fluorescence component from 71% to 43%. The device stack ITO/HATCN (10 nm)/NPB (30 nm)/TCTA (10 nm)/DPEPO:6 wt% emitter (30 nm)/TPBi (40 nm)/LiF/Al is deposited in a vacuum chamber at a base pressure of 2×10⁻⁸ Torr without breaking vacuum. Encapsulation uses a UV-cured epoxy dam and a glass lid with calcium oxide getters, and T50 operational lifetime is measured at 1200 h under an initial luminance of 1000 cd/m² per constant current drive, as outlined in IEC 62341-5-3:2023. Sky-blue TADF OLED panels manufactured with this emitter are targeted for high-color-gamut automotive dashboard displays requiring a brightness of 600 cd/m² and a BT.2020 color space coverage of 88%. Selective chemical labeling of the cysteine thiolate in serum albumin for fluorescence polarization assays is achieved with a maleimide-activated derivative of benzothiazole,2-(1H-indol-3-yl)-. The conjugate exhibits a molar extinction coefficient of 18,400 M⁻¹cm⁻¹ at 347 nm. Compliance with USP <85> bacterial endotoxins test guarantees endotoxin levels below 0.25 EU/mL in the reconstituted reagent. A lyophilized probe is reconstituted in anhydrous DMSO to a 10 mM stock and diluted into serum-free DMEM to a working concentration of 2 µM immediately before use; the molar labeling ratio reaches 0.94 mol probe per mol albumin after 30 min incubation at 37°C in the dark. Purification is accomplished via centrifugal filtration (10 kDa MWCO) with three buffer exchanges, followed by injection onto a Superdex 75 Increase size-exclusion column to remove unconjugated small molecules. The resulting albumin–fluorophore conjugate is supplied as a freeze-dried solid in single-use vials and employed by contract research organizations as a tracer reagent for high-throughput fluorescence polarization screening of kinase inhibitor selectivity. |
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The heterocyclic luminophore 2-(1H-indol-3-yl)benzothiazole (CAS 2659-65-9, molecular formula C₁₅H₁₀N₂S, Mr 250.32 g·mol⁻¹) is supplied as a pale yellow crystalline powder. In its as-received commercial form, typical chromatographic purity measured by HPLC-UV at 254 nm exceeds 98.0 area% (USP <621>), with a melting endotherm onset near 168–172 °C by differential scanning calorimetry (ASTM E794) at a heating rate of 10 K·min⁻¹. Residual solvent content is controlled below 500 ppm per headspace GC-MS (USP <467>), and heavy metals as lead are held under 20 ppm (USP <231>/Ph. Eur. 2.4.8). The molecule absorbs strongly in the UV-A region, exhibiting an absorption maximum at 348 nm in ethanol (ε ≈ 2.1 × 10⁴ L·mol⁻¹·cm⁻¹) and a fluorescence emission band centred at 430 nm, yielding a Stokes shift of roughly 82 nm. This optical signature underpins its primary uses as an intramolecular charge-transfer (ICT) fluorescent probe, a processing aid and UV-absorbing additive for thermoplastic films, and a key intermediate for polyheterocyclic pharmaceutical scaffolds. The compound is shipped in amber glass bottles under argon blanket to suppress photo-oxidation; once opened, storage under desiccation at −20 °C is recommended because the indole NH is susceptible to aerobic oxidation in solution.
Unlike 2-(2-hydroxyphenyl)benzothiazole (HBT) and its analogues that rely on an excited-state intramolecular proton transfer (ESIPT) across a pre-existing hydrogen bond, 2-(1H-indol-3-yl)benzothiazole lacks an acidic hydroxyl group and therefore does not exhibit the characteristic large Stokes shift (>150 nm) of ESIPT emitters. Instead, photoexcitation populates a planar intramolecular charge-transfer state in which the indole fragment acts as an electron donor and the benzothiazole heterocycle as the acceptor. The resulting emission is solvatochromic: in cyclohexane the maximum shifts to 395 nm, while in dimethyl sulfoxide it moves to 470 nm. Metal-ion sensing exploits the deprotonation of the indole amine, which shifts the HOMO–LUMO gap and generates a ratiometric fluorescence change at ligand-to-metal ratios ≥ 1:2. Table 1 compares key solution-phase photophysical metrics of three archetypal benzothiazole derivatives measured under identical conditions (ethanol, 25 °C, 10 µM). The indole derivative provides a balance of moderate quantum yield and a distinct metal-coordination site that is absent in 2-phenylbenzothiazole and fundamentally different from the phenolic OH of HBT.
| Compound | λex (nm) | λem (nm) | Quantum yield (Φ) | ESIPT | Metal-binding functionality |
|---|---|---|---|---|---|
| 2-(1H-Indol-3-yl)benzothiazole | 348 | 430 | 0.22 (vs quinine sulfate) | No | Indole NH, benzothiazole N |
| 2-(2-Hydroxyphenyl)benzothiazole (HBT) | 335 | 505 | 0.018 | Yes | Phenolic O, imine N |
| 2-Phenylbenzothiazole | 325 | 370 | 0.11 | No | None |
Detection of Zn²⁺ and Cd²⁺ in buffered aqueous media (HEPES 10 mM, pH 7.40, ionic strength adjusted with KCl to 0.1 M) is accomplished by monitoring the fluorescence intensity ratio I440/I510 on a spectrofluorometer equipped with a 150 W xenon source, excitation and emission bandpass of 3 nm, and a thermostatted cell at 25.0 ± 0.1 °C. The probe itself is introduced as a 5 µM solution containing 0.5% v/v DMSO to maintain solubility. Under these conditions, successive addition of Zn(NO₃)₂ up to 20 µM quenches the 510 nm band while enhancing the 440 nm emission, generating an isosbestic point at 472 nm. Published studies place the 3σ detection limit for Zn²⁺ at 0.8 µM, with a linear dynamic range from 1 to 12 µM. Validation against inductively coupled plasma mass spectrometry (EPA Method 200.8) in spiked tap water samples yielded recoveries between 94% and 107%, though inter-laboratory reproducibility according to ISO 13528 remains under formal assessment. Interfering trivalent cations such as Fe³⁺ and Al³⁺ must be masked with F⁻ (1 mM NaF) because they form non-fluorescent ground-state complexes that compete for the indole coordination site. Published data for the selectivity coefficients against Ca²⁺ and Mg²⁺, as defined by the Nikolskii–Eisenman formalism, exceeds 3.5 log units, making the probe suitable for biological fluids when used with a background electrolyte that mimics intracellular potassium concentrations.
Incorporation of the compound into low-density polyethylene (LDPE) films as a combined UV absorber and luminescent down-shifting additive requires careful attention to thermal stability and dispersion quality. When compounded on a co-rotating twin-screw extruder with 40:1 L/D ratio and a screw profile featuring two kneading blocks, the melt temperature must be maintained below 220 °C because thermal gravimetric analysis (ASTM E1131, N₂ atmosphere, 10 K·min⁻¹) records the onset of mass loss at 280 °C, and isothermal hold at 230 °C for 10 min causes 3.2% weight loss accompanied by yellow discolouration. A masterbatch approach is preferred: 10 wt% of the fluorophore is first dispersed in an ethylene-vinyl acetate (EVA) carrier with 28% vinyl acetate content at 110–130 °C on a two-roll mill, then let down to achieve final loadings of 0.5–2.0 wt% in blown film extrusion with a 30 mm annular die and a blow-up ratio of 2.5:1. The film’s spectral transmittance across 300–400 nm is measured per ASTM E3135-19, and the yellowness index (YI) is reported under ASTM E313. At 2.0 wt%, UV transmittance at 365 nm falls below 15% for a 50 µm film, while the YI remains below 3.5, provided that pre-drying of the masterbatch pellets is performed at 60 °C for 4 h whenever the storage relative humidity exceeds 60%; residual moisture promotes hydrolytic ring-opening of the thiazole moiety during extrusion, generating coloured by-products. Importantly, the indole-benzothiazole chromophore is incompatible with hindered amine light stabilizers (HALS) based on 2,2,6,6-tetramethylpiperidine structures: acid-base interactions between the protonated HALS and the indole nitrogen quench the fluorescence and shift the UV absorption tail into the visible range, increasing haze. In accelerated weathering per ASTM G154 Cycle 1 (UVA-340 lamps, 50 °C black panel temperature), a 100 µm LDPE film containing 1.5 wt% additive and no amine stabilizer retained 89% of its initial fluorescence intensity after 500 h, though comparative data against a non-stabilized reference film are still limited to internal batch evaluations.
The compound serves as a versatile starting material for the synthesis of bis-heterocyclic antimicrobial agents. Condensation with formaldehyde and secondary amines in acetic acid at 80 °C introduces a dialkylaminomethyl group at the 2′-position of the indole ring without affecting the benzothiazole core, as confirmed by ¹H NMR (disappearance of the indole C2-H singlet at δ 7.42). The resulting Mannich bases exhibit MIC values against methicillin-resistant Staphylococcus aureus (ATCC 43300) in the range of 4–16 µg·mL⁻¹ in Mueller–Hinton broth (CLSI M07-A11), with a minimum bactericidal concentration (MBC) typically two-fold higher. The free-radical scavenging activity of the parent molecule, measured as an IC₅₀ of 28 µmol·L⁻¹ in the DPPH assay (ASTM D1148-13 describes a related methodology), drops sharply after Mannich derivatization, indicating that the unsubstituted indole NH is essential for antioxidant potency. Purity of the benzothiazole building block must meet ≥99.0% (HPLC, 220 nm) before use in the Mannich reaction because a common contaminant — 2-(1H-indol-3-yl)benzothiazole-3-oxide — forms during prolonged light exposure and promotes side reactions that reduce isolated yields to below 50%. ICH Q7 guidelines for active pharmaceutical ingredient starting materials apply when the Mannich adducts are destined for preclinical development; in such cases, residual solvent limits (ICH Q3C) and the absence of genotoxic impurities are confirmed by LC-MS. Differences from the 2-phenylbenzothiazole scaffold become evident in the binding mode to bacterial topoisomerase IV: molecular docking simulations suggest that the indole nitrogen participates in an additional hydrogen bond with Asp-1089 of the enzyme active site, which is not formed by the corresponding phenyl-substituted analogue.
