[2,2'-Binaphthalene]-6,6'-dicarboxylic Acid: Lab Guide

[2,2'-Binaphthalene]-6,6'-dicarboxylic acid is a C2-symmetric, axially chiral dicarboxylic acid derived from the binaphthyl scaffold, valued in asymmetric synthesis, chiral resolution studies, and as a ditopic carboxylate linker for the construction of metal–organic frameworks (MOFs).

Chemical Name

[2,2'-Binaphthalene]-6,6'-dicarboxylic acid

Aladdin SKU

B590755

Molecular Formula

C22H14O4

Molecular Weight

346.34 g/mol

Key Structural Feature

Axially chiral biaryl backbone with two terminal carboxylic acid groups at the 6 and 6' positions

Primary Applications

Chiral ligand precursor, MOF/coordination polymer synthesis, asymmetric catalysis, supramolecular chemistry

Chemical Identity and Structural Properties

[2,2'-Binaphthalene]-6,6'-dicarboxylic acid consists of two naphthalene rings connected via a C2–C2' single bond, bearing carboxylic acid groups at the 6 and 6' positions. This positional arrangement places the functional groups distal to the biaryl bond, resulting in an elongated, rod-like geometry that is particularly well suited for use as a ditopic linker in porous framework construction.

The restricted rotation around the central biaryl bond—arising from steric interactions between the peri-hydrogen atoms on each naphthalene ring—gives rise to axial chirality and the existence of stable atropisomers (Ra and Sa enantiomers). The barrier to racemization is sufficiently high at ambient temperature to permit isolation and use of individual enantiomers or the racemate, depending on the intended application.

The compound is typically a white to off-white solid. Its planar aromatic system confers strong UV absorption, which is useful for analytical monitoring by HPLC. Solubility is limited in water but moderate in polar aprotic solvents such as DMF and DMSO, and in alkaline aqueous media upon deprotonation.

Synthesis and Purification Considerations

The binaphthyl-6,6'-dicarboxylic acid scaffold is commonly prepared by oxidation of the corresponding dimethyl or dialdehyde precursors, or via directed metalation and carboxylation strategies starting from 2,2'-binaphthyl. Enantiopure material can be accessed through resolution of the racemate using chiral amines or via asymmetric synthesis, though specific procedural details should be verified against primary literature.

Purification is typically achieved by recrystallization from appropriate solvent systems (e.g., acetic acid/water mixtures) or by column chromatography. Enantiomeric purity, when relevant, should be confirmed by chiral HPLC or by optical rotation measurements, as racemization can occur under harsh acidic or basic conditions at elevated temperatures.

When handling the compound, standard laboratory precautions for fine organic solids apply: use of personal protective equipment (gloves, safety glasses, lab coat), work in a well-ventilated area or fume hood, and avoid generating dust. Refer to the Safety Data Sheet (SDS) for compound-specific hazard information prior to use.

Research Applications

Metal–Organic Frameworks and Coordination Polymers: The two carboxylate groups act as coordination sites for metal ions (e.g., Zn²⁺, Cu²⁺, Zr⁴⁺), enabling assembly of porous MOFs and coordination polymers. The elongated geometry and potential chirality of the linker can impart large pore channels and enantioselective recognition properties to the resulting framework, making it relevant for chiral separation, asymmetric heterogeneous catalysis, and gas adsorption studies.

Asymmetric Synthesis and Chiral Ligand Design: As a chiral diacid, it serves as a precursor for the synthesis of chiral bis-amide, bis-imide, or mixed-function ligands. Such ligands find use in enantioselective transition-metal catalysis and organocatalysis, where the axially chiral environment controls facial selectivity.

Supramolecular Chemistry: The rigid, ditopic nature of the compound supports the self-assembly of discrete supramolecular cages, capsules, and macrocycles when combined with appropriate metal nodes or amine partners. These assemblies are of interest for host–guest chemistry, molecular recognition, and drug encapsulation research.

Analytical and Materials Science: The UV-active aromatic core enables its use as a fluorescent or UV-absorbing structural motif in functional materials, sensors, and probe design.

Storage, Stability, and Quality Assurance

[2,2'-Binaphthalene]-6,6'-dicarboxylic acid is chemically stable under standard storage conditions. Store the compound in a tightly sealed container at room temperature, protected from moisture and direct light. Desiccated storage is recommended if the laboratory environment is humid, as hygroscopic uptake can affect weighing accuracy for sensitive applications.

The compound shows good thermal stability typical of fused aromatic carboxylic acids; however, prolonged exposure to strong oxidizing agents, strong bases, or high temperatures should be avoided to prevent decomposition or racemization of enantiomerically pure material.

Aladdin Scientific's product B590755 is supplied with a product specification sheet. Researchers requiring specific purity data, NMR spectra, or HPLC traces for quality verification should consult the batch-specific certificate of analysis (CoA), available upon request from Aladdin Scientific. All quality-related inquiries can be directed to Aladdin's technical support team.

Frequently asked questions

What distinguishes [2,2'-Binaphthalene]-6,6'-dicarboxylic acid from [2,2'-Binaphthalene]-2,2'-dicarboxylic acid?

The 6,6'-isomer bears carboxylic acid groups at the distal (6 and 6') positions of the naphthalene rings, providing a longer molecular span and reduced steric crowding near the biaryl bond compared with the 2,2'-isomer, where functional groups are adjacent to the pivotal bond. This geometry makes the 6,6'-acid particularly effective as an elongated ditopic MOF linker, whereas the 2,2'-acid is more commonly used as a direct chiral auxiliary or in sterically demanding coordination environments.

Is the compound available as a single enantiomer, and how should enantiomeric purity be verified?

Availability as a single enantiomer versus racemate depends on the specific lot supplied; please consult the product listing or contact Aladdin Scientific to confirm the stereochemical form of SKU B590755. Enantiomeric purity is most reliably verified by chiral stationary-phase HPLC or by polarimetry (optical rotation measurement) against a literature reference value.

Which solvents are recommended for dissolving this compound in typical MOF synthesis protocols?

For MOF solvothermal synthesis, N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) are commonly employed due to the compound's good solubility in polar aprotic media. Aqueous alkaline solutions (e.g., dilute NaOH) can also be used to generate the dicarboxylate salt form. Solvent choice should be optimized based on the target metal ion, reaction temperature, and desired framework topology.

What safety precautions are necessary when handling [2,2'-Binaphthalene]-6,6'-dicarboxylic acid?

As a fine organic powder, the compound may cause irritation upon contact with skin, eyes, or the respiratory tract. Always wear appropriate PPE including nitrile gloves, safety glasses, and a lab coat. Handle in a well-ventilated area or fume hood to avoid inhalation of dust. Consult the current Safety Data Sheet (SDS) provided by Aladdin Scientific for comprehensive hazard, first-aid, and disposal information specific to this product.

References

1. General principles of axial chirality in biaryl systems: March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 7th ed. Wiley, 2013.
2. Metal–organic frameworks based on dicarboxylate linkers: Yaghi, O. M. et al. Reticular synthesis and the design of new materials. Nature 2003, 423, 705–714. doi:10.1038/nature01650
3. Chiral binaphthyl-based linkers in asymmetric MOFs: Cui, Y. et al. Metal-organic frameworks as platforms for functional materials. Accounts of Chemical Research 2016, 49, 483–493. doi:10.1021/acs.accounts.5b00530

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