4,7-Bis(pinacol boronate)-benzothiadiazole: FAQ & Uses
4,7-Bis(pinacol boronate)-benzothiadiazole: FAQ & Uses
4,7-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,1,3-benzothiadiazole is a bifunctional pinacol boronate ester monomer widely employed as an electron-deficient acceptor building block in Suzuki–Miyaura polycondensation reactions for constructing donor–acceptor conjugated polymers and small molecules intended for organic electronics applications.
- CAS Number
- 361453-97-6
- Molecular Formula
- C₂₀H₂₄BN₂O₄S (approximate; two pinacol boronate groups on benzothiadiazole core)
- Functional Groups
- Two pinacol boronate ester groups at the 4- and 7-positions of 2,1,3-benzothiadiazole
- Primary Application
- Suzuki–Miyaura cross-coupling and polycondensation to build donor–acceptor conjugated polymers for OPV, OLED, and OFETs
- Key Electronic Feature
- Strong electron-withdrawing benzothiadiazole core lowers LUMO, enabling low-bandgap polymer design
- Storage Recommendation
- Store in a cool, dry place under inert atmosphere; protect from moisture to preserve boronate ester integrity
What Is 4,7-Bis(pinacol boronate)-2,1,3-benzothiadiazole and Why Is It Important?
4,7-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,1,3-benzothiadiazole (SKU B152841) is a symmetrical, bifunctional organoboron compound in which two pinacol boronate ester groups are installed at the 4- and 7-positions of the 2,1,3-benzothiadiazole (BTZ) heterocycle. The BTZ core is a well-established electron-acceptor (A) unit owing to the strong electron-withdrawing character of the thiadiazole ring fused to benzene.
Because both reactive sites are boronate esters rather than free boronic acids, this compound offers improved air stability, easier handling, and compatibility with standard Suzuki–Miyaura coupling protocols. Researchers use it as the acceptor monomer in alternating donor–acceptor (D–A) copolymerizations, pairing it with electron-rich comonomers (e.g., fluorene, carbazole, or thiophene-based donors) to tune optical bandgap and energy levels for applications in organic photovoltaics (OPV), organic light-emitting diodes (OLEDs), and organic field-effect transistors (OFETs).
How Is This Compound Used in Suzuki–Miyaura Polycondensation?
In a typical Suzuki–Miyaura polycondensation, 4,7-bis(pinacol boronate)-benzothiadiazole is combined in an equimolar ratio with a dihalogenated donor monomer (e.g., a dibromo-fluorene or dibromo-carbazole derivative). A palladium catalyst system — commonly Pd(PPh₃)₄ or Pd₂(dba)₃ with a phosphine ligand — and an aqueous base (e.g., K₂CO₃ or Cs₂CO₃) are used in a mixture of toluene or THF with water or DMF.
Key practical considerations include:
- Strict monomer ratio: Achieving high molecular weight requires precise 1:1 stoichiometry between the diboronate and dihalide monomers.
- Catalyst loading: Typically 1–3 mol% Pd; higher loadings can introduce metallic impurities detrimental to device performance.
- Deoxygenation: All solvents and solutions must be thoroughly degassed to prevent palladium catalyst poisoning and undesired oxidation of the boronate ester.
- Reaction temperature: Reactions are generally run at 80–100 °C under reflux for 12–48 hours to achieve sufficient chain growth.
The resulting alternating D–A conjugated polymer is typically purified by Soxhlet extraction and characterized by GPC, NMR, and UV-Vis spectroscopy.
What Are the Key Properties and Handling Requirements?
Physical properties: The compound is typically a pale yellow to off-white solid at room temperature. The pinacol boronate ester groups confer greater hydrolytic stability compared to free boronic acids, but prolonged exposure to moisture can still result in partial hydrolysis to the boronic acid form, potentially causing premature protodeboronation or dimerization.
Storage: Store under an inert atmosphere (nitrogen or argon) in a tightly sealed container at 2–8 °C or at room temperature in a cool, dry location away from light and moisture. Check the certificate of analysis (CoA) supplied with each lot for specific purity data.
Safety: Handle with standard laboratory precautions — gloves, eye protection, and a lab coat. Avoid inhalation of dust. Consult the Safety Data Sheet (SDS) for full hazard information before use. This compound is not classified as highly toxic, but as with all fine chemicals, minimize unnecessary exposure.
Purity considerations: For high-performance polymer synthesis, high monomer purity (≥97%) is critical. Trace halide or palladium impurities in the monomer can act as chain terminators, limiting polymer molecular weight and adversely affecting electronic device performance.
What Applications Benefit from This Building Block?
The electron-deficient BTZ unit in this monomer makes it particularly valuable across several research domains:
- Organic Photovoltaics (OPV): D–A polymers incorporating BTZ display broad absorption in the visible and near-IR regions due to intramolecular charge transfer (ICT), facilitating efficient solar light harvesting.
- Organic Light-Emitting Diodes (OLEDs): BTZ-based emitters can display green-to-red emission depending on the donor unit; the D–A architecture allows tuning of emission color and efficiency.
- Organic Field-Effect Transistors (OFETs): The lowered LUMO of BTZ-containing polymers supports n-type or ambipolar charge transport.
- Chemical and biological sensing: Conjugated BTZ-based fluorophores have been explored as fluorescent probes for ion sensing and bioimaging due to their tunable emission and photostability.
- Non-fullerene acceptor synthesis: The BTZ core is a component in small-molecule non-fullerene acceptors (NFAs) for next-generation OPV devices.
Ordering, Availability, and Quality Assurance at Aladdin Scientific
SKU: B152841 — 4,7-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,1,3-benzothiadiazole is available from Aladdin Scientific. Visit the product page to view current pack sizes, pricing, and stock availability.
Quality assurance: Each lot is accompanied by a Certificate of Analysis (CoA) specifying purity (typically determined by HPLC or NMR), appearance, and lot-specific testing results. Researchers requiring additional characterization data (e.g., melting point, elemental analysis) should contact Aladdin Scientific's technical support team.
Bulk and custom quantities: For scale-up projects or custom purity specifications, please contact our sales team to discuss bulk pricing and lead times.
Returns and queries: If the product does not meet the specifications stated on the CoA, please contact customer service within the applicable return window. Refer to Aladdin Scientific's returns and refund policy for full details.
Frequently asked questions
What is the difference between this diboronate ester and the corresponding diboronic acid form of benzothiadiazole?
The pinacol boronate ester form (SKU B152841) is significantly more stable toward hydrolysis and oxidation compared to the free diboronic acid, making it easier to handle, weigh, and store under standard laboratory conditions. In Suzuki coupling reactions, boronate esters and boronic acids are generally interchangeable in reactivity, though ester forms may require slightly modified base conditions (e.g., stronger or aqueous base) to achieve efficient transmetalation. For polymer synthesis where precise stoichiometry is critical, the ester form's superior shelf stability and well-defined molecular weight are practical advantages.
Which palladium catalyst and conditions are recommended for Suzuki coupling with this compound?
Pd(PPh₃)₄ is among the most commonly reported catalysts for Suzuki–Miyaura couplings and polycondensations involving BTZ diboronate monomers, typically used at 1–3 mol% loading in toluene/aqueous K₂CO₃ at 80–90 °C. Pd₂(dba)₃ combined with tri(o-tolyl)phosphine or SPhos ligand is also reported for polymerization applications and can give higher molecular weights in some systems. All reactions should be conducted under strict inert atmosphere (Ar or N₂) with degassed solvents to avoid catalyst deactivation and ensure reproducible results. Aladdin Scientific recommends consulting primary literature for the specific donor comonomer being used, as optimal conditions vary.
How should I store SKU B152841 to maintain purity and prevent degradation?
Store B152841 in a tightly sealed vial under an inert gas (nitrogen or argon) at 2–8 °C or in a cool, dark, dry environment at room temperature away from moisture and light. Pinacol boronate esters are susceptible to slow hydrolysis upon repeated exposure to ambient humidity, which converts them to the boronic acid and can lead to further protodeboronation over time. It is advisable to aliquot the material upon first opening to minimize repeated exposure to air and moisture. Always check the CoA for the recommended storage conditions specific to each lot.
Is this compound suitable for small-molecule synthesis in addition to polymer applications?
Yes. While 4,7-bis(pinacol boronate)-benzothiadiazole is most widely used in polymer synthesis, it is equally applicable to small-molecule Suzuki coupling reactions for the preparation of D–A–D or A–D–A type conjugated small molecules. Such small molecules are of interest as non-fullerene acceptors, fluorescent dyes, and molecular probes. The symmetry of the compound allows efficient double coupling with two equivalents of a donor aryl halide in a single reaction step to give symmetric D–A–D architectures.
What purity grade is available and why does purity matter for organic electronics applications?
Aladdin Scientific supplies B152841 with a purity specification detailed in the lot-specific CoA; researchers should verify the exact purity value on the CoA for their batch. In organic electronics, even sub-percent levels of impurities — particularly residual palladium, halides, or regioisomeric byproducts — can function as charge-carrier traps or chain terminators that significantly reduce device performance, lower polymer molecular weight, and introduce batch-to-batch variability. High-purity (≥97%) monomer is therefore strongly recommended for device-grade polymer synthesis.
References
- Jeffries-El, M.; Kobilka, B. M.; Hale, B. J. Optimizing the Performance of Conjugated Polymers in Organic Photovoltaic Cells by Traversing Group 16 of the Periodic Table. Macromolecules 2014, 47 (21), 7253–7271.
- Günes, S.; Neugebauer, H.; Sariciftci, N. S. Conjugated Polymer-Based Organic Solar Cells. Chem. Rev. 2007, 107 (4), 1324–1338. doi:10.1021/cr050149z
- Miyaura, N.; Suzuki, A. Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds. Chem. Rev. 1995, 95 (7), 2457–2483. doi:10.1021/cr00039a007
- Aladdin Scientific Product Page: 4,7-Bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,1,3-benzothiadiazole, SKU B152841.
Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.
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