Thiophoshonates

Introduction Acetyl-protected thiols Coupling reagents Disulfides Dithiols for nanoparticle assembly Fluorinated thiols and silanes Functionalized thiols Graphene derivatives Ligands for iron oxide surfaces MOFs Photoswitchable thiols Silanes Thiolated Carbohydrates (mimicking glycans) Thiolated crown ethers Thiols and disulfides for fluorescent SAMs and NPs Thiols for bioresistant and biospecific SAMs Thiols for electroactive SAMs Thiophoshonates Ultra-bioresistant Zwitterionic ligands Useful synthetic precursors and building blocks

Alkylphosphonic and alkylphosphoric acids are less often characterized compared to silanes and thiols, but they are the becoming of great practical interest because of their ability to produce SAMs on a range of metal oxide surfaces (TiO₂ [1], ZrO₂ [2], Al₂O₃ [2], Ta₂O₅ [2], Nb₂O₅ [2], ITO[3], MgO[4] ect.). The reaction of long-chain alkylphosphonic [5] or phosphoric [6] acids with metal oxide supports leads to dense, well-ordered SAMs. Phosphonates and phosphonic acids form SAMs on metal surfaces by the formation of metal-O-P bonds. The deposition technique is based on SAMs made from aqueous alkyl phosphate solutions, which has the advantage of not using organic solvents [2]. However, well-ordered SAMs can be also obtained from organic solutions as well. Advantages of these SAMs compared to silane ones are a higher hydrolytic stability under physiological conditions and the fact that no surface conditioning (i.e., acid treatment) is required to obtain high coverage[7]. We have developed the a range of alkylthiophosphates bearing additional functional groups (OH, EG₃OH, NH2, COOH, CONHS) at terminal position, what allows further elaboration of SAMs by chemical attachment of relevant molecules.

[1] M. Gnauck, E. Jaehne, T. Blaettler, S. Tosatti, M. Textor, H. J. P. Adler, Carboxy-Terminated Oligo(ethylene glycol)-Alkane Phosphate: Synthesis and Self-Assembly on Titanium Oxide Surfaces, Langmuir, 2007, 23, 377-381.

[2] R. Hofer, M. Textor and N. D. Spencer, Alkyl Phosphate Monolayers Self-Assembled from Aqueous Solution onto Metal Oxide Surfaces, Langmuir, 2001, 17, 4014-4020.

[3] A. Jedaa, M. Burkhardt, U. Zschieschang, H. Klauk, D. Habich, G. Schmid, M. Halik, The impact of self-assembled monolayer thickness in hybrid gate dielectrics for organic thin-film transistors, Org. Electron., 2009, 10, 1442-1447. [4] T. Ishizaki, M. Okido, Y. Masuda, N. Saito, M. Sakamoto, Corrosion Resistant Performances of Alkanoic and Phosphonic Acids Derived Self-Assembled Monolayers on Magnesium Alloy AZ31 by Vapor-Phase Method, Langmuir, 2011, 27, 6009-6017

[5] C. Queffelec, M. Petit, P. Janvier, D. A. Knight, B. Bujoli, Surface Modification Using Phosphonic Acids and Esters, Chem. Rev. , 2012, 112, 3777-3807.

[6] S. Tosatti, R. Michel, M. Textor and N. D. Spencer, Self-Assembled Monolayers of Dodecyl and Hydroxy-Dodecyl Phosphates on Both Smooth and Rough Titanium and Titanium Oxide Surfaces, Langmuir, 2002, 18, 3537-3548.

[7] B. M. Silverman, K. A. Wieghaus, and J. Schwartz, Comparative Properties of Siloxane vs Phosphonate Monolayers on A Key Titanium Alloy, Langmuir, 2005, 21, 225-228.