Rearrangement of Diferrocenyl 3,4-Thiophene Dicarboxylate

Treatment of 3,4-(ClC(O))(2)-(c)C4H(2)S (1) with [FcCH(2)OLi] (2-Li) (Fc = Fe(eta(5)-C5H5)(eta(5)-C5H4)) in a 1:2 ratio gave 3,4-(FcCH(2)OC(O))(2)-(C4H2S)-C-c (3). Compound 3 decomposes in solution during crystallization to produce FcCH(2)OH (2) along with 3,4-thiophenedicarboxylic anhydride (4). The cyclic voltammogram of 3 exhibits a reversible ferrocene-related redox couple (E-1/2 = 108 mV, vs. Cp2Fe/Cp2Fe+) using [NnBu(4)] [B(C6F5)(4)] as the supporting electrolyte. DFT calculations reveal that the energy values of the LUMO orbitals of 3 (3,4-thiophene core) show 1 eV higher energies than that one of 2,5-(FcCH(2)OC(O))(2)-(C4H2S)-C-c (5), both compounds' HOMO orbitals are close to each other. Compound 4 was characterized by single X-ray structure analysis. It forms a band-type structure based on intermolecular O1 center dot center dot center dot S1 interactions being parallel to (110) and (1-10) in the solid state, while electrostatic C center dot center dot center dot O interactions between the C=O functionalities of adjacent molecules connect both 3D-networks. Hirshfeld surface analysis was used to gain more insight into the intermolecular interactions in 4, the enrichment ratios (E) suggest that O center dot center dot center dot H, S center dot center dot center dot S, and O center dot center dot center dot C are the most favored intermolecular interactions, as shown by E values above 1.20. The relevance of the weak O center dot center dot center dot H, O center dot center dot center dot O, and O center dot center dot center dot C contacts in stabilizing the molecular structure of 4 was highlighted by the interaction energies between molecular pairs.

Automated summary

This study reports on the synthesis, crystallization, and cyclic voltammogram analysis of compound 3, which exhibits a reversible ferrocene-related redox couple. DFT calculations and X-ray structure analysis reveal the molecular structure and intermolecular interactions of compounds 3 and 4. Hirshfeld surface analysis provides insights into the intermolecular interactions in compound 4.