Spiro-MeOTAD (207739-72-8): Properties & Research Significance

Introduction to Spiro-MeOTAD (CAS 207739-72-8)

Spiro-MeOTAD, formally known as 2,2′,7,7′-Tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene, and identified by CAS Number 207739-72-8, is a complex organic molecule that has garnered significant attention in the field of materials science. While primarily celebrated for its role as a highly efficient hole transport material (HTM) in advanced electronic applications like perovskite solar cells (PSCs) and organic light-emitting diodes (OLEDs), its nature as a sophisticated organic compound also positions it as a substance of interest in broader chemical synthesis and research, which can tangentially extend to the pharmaceutical research and development landscape. Understanding Spiro-MeOTAD (CAS 207739-72-8) is important for researchers and chemists exploring advanced materials and complex organic synthesis, as its unique structure and properties can offer insights for developing novel compounds. It is crucial to note from the outset that Spiro-MeOTAD itself is not an active pharmaceutical ingredient (API) or a therapeutic drug; its relevance to the pharmaceutical field is primarily as a high-purity chemical for laboratory research and as a potential intermediate or building block in the synthesis of new chemical entities that could undergo investigation for medicinal properties.

Chemical Properties of Spiro-MeOTAD

Spiro-MeOTAD (CAS 207739-72-8) possesses several distinct chemical and physical properties that are key to its functionality in its primary applications and its utility in research:

• Appearance: It is typically a light yellow to tan or pale brown powder or crystalline solid.
• Molecular Formula: C81​H68​N4​O8​
• Molecular Weight: Approximately $1225.43\text{ g/mol}$.
• Solubility: Spiro-MeOTAD is soluble in several organic solvents such as dimethylformamide (DMF), chlorobenzene, toluene, and chloroform (slightly). It is sparingly soluble in aqueous solutions.
• Stability: It exhibits good thermal stability, with a high glass transition temperature and melting point typically reported in the range of 234−249∘C. This stability is crucial for device longevity in its electronic applications.
• Structure: The “spiro” aspect of its name refers to the two fluorene systems linked by a single common carbon atom. This unique spiro-structure contributes to its morphological stability (resistance to crystallization) and its ability to form amorphous films, which is beneficial for electronic devices.
• Electronic Properties: As a hole transport material, it has suitable HOMO (Highest Occupied Molecular Orbital) energy levels (around -5.0 eV to -5.1 eV) that align well with the energy levels of other materials in solar cells and OLEDs, facilitating efficient movement of positive charge carriers (holes).
• Purity: For its applications in electronics and research, Spiro-MeOTAD is often required in high purity (e.g., >99%, sometimes >99.8% via sublimation).

These properties, particularly its complex structure and purity, make Spiro-MeOTAD (CAS 207739-72-8) a valuable compound for researchers synthesizing or investigating complex organic molecules.

Uses & Applications of Spiro-MeOTAD (CAS 207739-72-8)

The primary and most well-established applications of Spiro-MeOTAD (CAS 207739-72-8) lie outside the direct pharmaceutical domain:

• Perovskite Solar Cells (PSCs): This is arguably the most significant application. Spiro-MeOTAD is one of the most successful and widely used hole transport materials (HTMs) in PSCs, contributing to their high power conversion efficiencies. It helps extract “holes” from the perovskite absorber layer and transport them to the electrode.
• Organic Light-Emitting Diodes (OLEDs): It also serves as an HTM in some OLED configurations, contributing to device efficiency and stability.
• Solid-State Dye-Sensitized Solar Cells (ssDSSCs): Before the rise of PSCs, Spiro-MeOTAD was instrumental in advancing ssDSSCs by replacing liquid electrolytes.
• Organic Photovoltaics (OPVs) & Other Organic Electronics: Its properties make it suitable for various other research applications in organic electronic devices.

Role in Pharmaceutical Research and Development:

It’s important to reiterate that Spiro-MeOTAD (CAS 207739-72-8) is not used as a medication. However, its role in the broader chemical and pharmaceutical research context can be understood as:

• Laboratory Research Chemical: It is sold by chemical suppliers for research and development purposes only. Products are often explicitly labeled “FOR RESEARCH USE ONLY – NOT FOR HUMAN OR VETERINARY DIAGNOSTIC OR THERAPEUTIC USE.”
• Intermediate in Organic Synthesis: Due to its complex, well-defined structure, Spiro-MeOTAD or its precursors could serve as starting materials or intermediates in the laboratory synthesis of novel organic compounds. Some of these newly synthesized molecules might then be investigated for potential pharmaceutical properties, though this is a step removed from Spiro-MeOTAD itself being a pharmaceutical.
• Development of Diagnostic Tools: While not a current mainstream application, materials with unique electronic properties like Spiro-MeOTAD could theoretically be explored in the research and development of new types of biosensors or diagnostic devices, although this remains speculative for this specific compound.

Currently, Spiro-MeOTAD (CAS 207739-72-8) is generally considered an investigational material in the broadest sense when it comes to any application beyond its established roles in electronics. There are no known therapeutic uses or formulations where it acts as an Active Pharmaceutical Ingredient (API).

Benefits of Spiro-MeOTAD in its Fields of Application

The advantages offered by Spiro-MeOTAD (CAS 207739-72-8) are most evident in its primary field of organic electronics:

• High Hole Mobility: Facilitates efficient charge transport, leading to better device performance in solar cells and OLEDs.
• Good Film-Forming Properties: Its ability to form stable, amorphous films with good pore-filling capability is advantageous for creating uniform layers in electronic devices.
• Appropriate Energy Level Alignment: Its HOMO energy level aligns well with many perovskite materials and other components in organic electronic devices, optimizing charge extraction and minimizing energy loss.
• Thermal and Morphological Stability: The spiro-structure contributes to a high glass transition temperature and good morphological stability, which can enhance the operational lifetime of devices.
• High Solubility in Organic Solvents: Allows for solution processing, which can simplify device fabrication.

Indirect Benefits in a Broader Research Context (including potential pharmaceutical R&D):

• Availability as a High-Purity Chemical: Researchers have access to a well-characterized, complex organic molecule for various synthetic or materials science investigations.
• Platform for New Molecular Design: The core spirobifluorene structure with its amine functionalities could inspire the design of new molecules with tailored properties for various applications, potentially including medicinal chemistry research if derivatives were to show biological activity.

Safety Profile of Spiro-MeOTAD: General Handling & Precautions (CAS 207739-72-8)

As a research chemical, Spiro-MeOTAD (CAS 207739-72-8) should be handled with care, following standard laboratory safety protocols. Specific safety data can be found in the Safety Data Sheet (SDS) provided by the supplier. General precautions include:

• Handling: Avoid inhalation of dust or vapors. Avoid contact with skin, eyes, and clothing. Use in a well-ventilated area or with appropriate exhaust ventilation (e.g., fume hood).
• Personal Protective Equipment (PPE): Wear appropriate PPE, such as gloves, safety glasses, and a lab coat.
• Storage: Store in a cool, dry place, typically at room temperature, sealed in its original container, and often under an inert atmosphere (like nitrogen) to maintain purity.
• Toxicity: Detailed toxicological data for Spiro-MeOTAD is not extensively published in the context of human health effects, as it’s not intended for human consumption or therapeutic use. Some supplier SDSs indicate it is not classified as a hazardous substance according to certain regulations (e.g., Regulation (EC) No. 1272/2008), while others may note potential for skin or eye irritation. Symptoms of poisoning may occur after several hours; therefore, medical observation may be needed after significant exposure.
• Disposal: Dispose of in accordance with local, regional, and national environmental regulations.

Crucially, this information is not exhaustive. Always consult the official Safety Data Sheet (SDS) from the supplier and adhere to good laboratory practices. This chemical is for research use only and is not intended for human or veterinary diagnostic or therapeutic use.

Manufacturing Overview of Spiro-MeOTAD

The synthesis of Spiro-MeOTAD (CAS 207739-72-8) is a multi-step organic chemistry process. While specific proprietary details may vary between manufacturers, the general approach involves creating the spirobifluorene core and then attaching the N,N-di-p-methoxyphenylamine arms. Key steps typically involve:

1. Formation of the Spirobifluorene Core: This is a critical part of the synthesis, often involving coupling reactions to create the central spiro linkage.
2. Functionalization/Amination: The spirobifluorene core is then functionalized, commonly through bromination, followed by Buchwald-Hartwig amination reactions (or similar C-N coupling reactions) to attach the four diarylamine groups (N,N-di-p-methoxyphenylamine).
3. Purification: High purity is essential for its applications, especially in electronics. Purification methods often include column chromatography, recrystallization, and, for very high purity grades, sublimation.

Quality control throughout the manufacturing process is vital, with techniques like HPLC (High-Performance Liquid Chromatography) and NMR (Nuclear Magnetic Resonance) spectroscopy used to verify purity and structure. The complexity of the synthesis contributes to its relatively high cost compared to simpler organic compounds.

FAQ Section about Spiro-MeOTAD

Q1: What is Spiro-MeOTAD (CAS 207739-72-8) primarily used for?

A: Spiro-MeOTAD (CAS 207739-72-8) is primarily used as a hole transport material (HTM) in organic electronic devices, most notably in perovskite solar cells and organic light-emitting diodes (OLEDs), due to its excellent electronic and physical properties.

Q2: Is Spiro-MeOTAD (CAS 207739-72-8) used in any medicines or drugs?

A: No, Spiro-MeOTAD itself is not an active pharmaceutical ingredient (API) and is not used directly in any medicines or drugs. It is a research chemical. While it could theoretically be used as an intermediate in the laboratory synthesis of new compounds that might be investigated for pharmaceutical properties, Spiro-MeOTAD itself is not for human therapeutic use.

Q3: Why is Spiro-MeOTAD important for solar cells?

A: In perovskite solar cells, Spiro-MeOTAD plays a crucial role in efficiently extracting positive charge carriers (holes) from the light-absorbing perovskite layer and transporting them to the electrode. This function is vital for achieving high power conversion efficiencies in these types of solar cells.

Q4: Is Spiro-MeOTAD (CAS 207739-72-8) safe to handle?

A: Spiro-MeOTAD (CAS 207739-72-8) is a chemical compound intended for laboratory research and should be handled with appropriate safety precautions as outlined in its Safety Data Sheet (SDS). This includes using personal protective equipment and working in a well-ventilated area. It is not intended for consumption or direct application to the body.

Q5: Where can reliable information about Spiro-MeOTAD (CAS 207739-72-8) be found?

A: Reliable information can be found in scientific journals focusing on materials science, organic electronics, and chemistry. Chemical supplier websites (e.g., Sigma-Aldrich, Cayman Chemical, Ossila, TCI Chemicals) also provide product specifications, safety data sheets (SDS), and summaries of its applications. For research purposes, scientific databases like SciFinder, Reaxys, and Google Scholar are valuable resources.