(4-Cyanophenyl)phosphonic acid: Properties & Applications

(4-Cyanophenyl)phosphonic acid is a bifunctional arylphosphonic acid reagent featuring both a phosphonic acid group for strong surface anchoring and a para-cyano group that enables further chemical elaboration, making it a versatile building block in surface science, coordination chemistry, and functional materials research.

Chemical Name

(4-Cyanophenyl)phosphonic acid

SKU

C1035742

Molecular Formula

C7H6NO3P

Molecular Weight

183.10 g/mol

Key Functional Groups

Phosphonic acid (–PO(OH)₂) and nitrile (–CN)

Primary Application Areas

Surface modification, coordination chemistry, materials science

Supplier

Aladdin Scientific

Chemical Structure and Physicochemical Properties

(4-Cyanophenyl)phosphonic acid (molecular formula C₇H₆NO₃P, MW ≈ 183.10 g/mol) belongs to the arylphosphonic acid family. Its structure consists of a benzene ring substituted at the para position with a nitrile (–CN) group and bearing a phosphonic acid (–PO(OH)₂) moiety directly bonded to the ring carbon. This direct C–P bond confers high hydrolytic stability compared with phosphate esters, a key practical advantage for research applications.

The compound is typically obtained as a white to off-white crystalline solid. The phosphonic acid group is diprotic, with two successive pKa values characteristic of arylphosphonic acids (generally pKa1 in the range of 1–2 and pKa2 in the range of 6–7 for aryl systems; exact values for this compound should be confirmed experimentally). The para-cyano substituent is electron-withdrawing, modestly lowering the electron density on the ring and the phosphorus center relative to unsubstituted phenylphosphonic acid.

Synthesis and Handling

Arylphosphonic acids such as (4-Cyanophenyl)phosphonic acid are commonly prepared via Michaelis–Arbuzov reactions or palladium-catalyzed phosphonation of the corresponding aryl halide, followed by hydrolysis of the intermediate phosphonate ester. The cyanophenyl scaffold may alternatively be introduced by nitrile formation (e.g., from the corresponding amine via diazotization) on a preformed phenylphosphonic acid derivative.

For routine laboratory handling, standard precautions for organophosphorus reagents apply. The compound should be stored in a cool, dry environment, protected from moisture to prevent surface adsorption of water, and kept away from strong bases or nucleophiles that could react with the nitrile group. Always consult the Safety Data Sheet (SDS) before use. Researchers should wear appropriate personal protective equipment including gloves, eye protection, and lab coat.

Research Applications

Surface Functionalization: Phosphonic acids are well-established anchoring agents for metal oxide surfaces including TiO₂, Al₂O₃, ZrO₂, and ITO. (4-Cyanophenyl)phosphonic acid forms stable monolayers on such surfaces through mono-, bi-, or tridentate coordination of the –PO(OH)₂ group. The pendant nitrile group can serve as a handle for subsequent click-chemistry-type transformations, coupling reactions, or as a ligand for metal coordination, enabling the construction of multifunctional surfaces.

Coordination Chemistry and MOFs: The bifunctional nature of this compound—phosphonate donor and nitrile acceptor—makes it an attractive ligand precursor for metal–organic frameworks (MOFs) and coordination polymers. The cyano group can coordinate to soft Lewis acid metal centers or be hydrolyzed to a carboxylate, generating a mixed phosphonate/carboxylate linker in situ.

Organic Electronics and Self-Assembled Monolayers (SAMs): Arylphosphonic acid SAMs are used to tune the work function of transparent electrodes in organic photovoltaic (OPV) and organic light-emitting diode (OLED) devices. The electron-withdrawing cyano group modulates the dipole moment of the monolayer, offering a handle for systematic work-function engineering.

Probe Chemistry and Bioconjugation: Nitrile groups can participate in tetrazine–nitrile inverse electron demand cycloadditions and other bioorthogonal reactions, while the phosphonic acid portion may be used for hydroxyapatite or protein surface binding, opening possibilities in biosensor and bioconjugation research.

Ordering and Availability

(4-Cyanophenyl)phosphonic acid is available from Aladdin Scientific under SKU C1035742. Researchers requiring custom quantities, purity specifications, or bulk orders are encouraged to contact Aladdin Scientific's technical sales team for tailored quotations. Product specifications including purity grade, analytical data (NMR, HPLC), and safety information are available on the product page or upon request.

When placing an order, ensure that storage and shipping requirements for the compound are reviewed. Standard laboratory chemical shipping conditions typically apply; however, specific requirements should be confirmed with Aladdin Scientific at the time of purchase.

Frequently asked questions

What makes (4-Cyanophenyl)phosphonic acid useful for surface modification?

The phosphonic acid group forms highly stable, covalent-like bonds with metal oxide surfaces (e.g., TiO₂, Al₂O₃, ZrO₂) through mono-, bi-, or tridentate coordination, creating robust self-assembled monolayers. The hydrolytic stability of the C–P bond ensures the monolayer persists under aqueous conditions. The para-cyano group then provides a reactive handle for further functionalization.

Can the nitrile group of this compound be further chemically modified?

Yes. The nitrile (–CN) group can undergo several transformations including acid/base-catalyzed hydrolysis to a carboxylic acid or amide, reduction to a primary amine, conversion to tetrazole via [3+2] cycloaddition with azides, and participation in bioorthogonal tetrazine–nitrile reactions. These reactions make it a versatile handle for post-functionalization of surfaces or in solution-phase synthesis.

How should (4-Cyanophenyl)phosphonic acid be stored?

The compound should be stored in a tightly sealed container in a cool, dry place, away from moisture and incompatible reagents such as strong bases, strong nucleophiles, and reducing agents. Refer to the product's Safety Data Sheet (SDS) and Certificate of Analysis (CoA) available from Aladdin Scientific for specific storage temperature recommendations and shelf-life information.

Is (4-Cyanophenyl)phosphonic acid suitable for use in organic electronic device fabrication?

Yes, arylphosphonic acids with electron-withdrawing substituents are used to modify the work function of transparent conductive oxide electrodes in OPV and OLED devices. The electron-withdrawing cyano group at the para position creates a surface dipole that can shift the electrode work function, improving charge injection or extraction efficiency. Experimental optimization is recommended for each specific device architecture.

References

1. Guerrero, G.; Alauzun, J. G.; Granier, M.; Laurencin, D.; Mutin, P. H. Phosphonate coupling molecules for the control of surface/interface properties and the synthesis of nanomaterials. Dalton Trans. 2013, 42, 12569–12585. doi:10.1039/c3dt51193f
2. Hotchkiss, P. J.; Jones, S. C.; Paniagua, S. A.; Sharma, A.; Kippelen, B.; Armstrong, N. R.; Marder, S. R. The modification of indium tin oxide with phosphonic acids: mechanism of binding, tuning of surface properties, and potential for use in organic electronic applications. Acc. Chem. Res. 2012, 45, 337–346. doi:10.1021/ar200119g
3. Michaelis, A.; Kaehne, R. Ueber das Verhalten der Jodalkyle gegen die sogen. Phosphorigsäureester oder P(OR)₃-Verbindungen. Ber. Dtsch. Chem. Ges. 1898, 31, 1048–1055.

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