1,1′-Bis(pyrazol-3-yl)ferrocene: A Clip Ligand That Forms Supramolecular Aggregates and Prismatic Hexanuclear Coinage Metal Complexes
2015-07-20T00:00:00Z (GMT) by
Two ferrocene derivatives with appended pyrazole substituents, namely, 1,1′-bis(5-methyl-1H-pyrazol-3-yl)ferrocene (H2LH) and 1,1′-bis(5-trifluoromethyl-1H-pyrazol-3-yl)ferrocene (H2LF), were synthesized. In solid state they form distinct H-bonded dimers with orthogonal (H2LH, C2 symmetry) or antiparallel (H2LF, C2h symmetry) arrangement of the two ferrocene/pyrazole hybrid molecules. Supramolecular dimerization was also detected in solution at low temperatures, though diffusion-ordered spectroscopy and variable-temperature NMR spectroscopy revealed several dynamic processes. Redox potentials of the ferrocene derivatives are affected by the nature of the pyrazole substituent (Me, CF3). In their deprotonated form [LR]2–, both ferrocene/pyrazole hybrids serve as ligands and form oligonuclear CuI, AgI, and AuI complexes that were identified by matrix-assisted laser desorption ionization mass spectrometry. X-ray crystallography revealed the structures of Cu6L3H and Ag6L3F, which both contain two parallel and eclipsed [M(μ-pz)]3 metallamacrocycles (M = Cu, Ag) linked by three ferrocene units. MI···MI distances between the two triangular M3N6 decks are shorter in Ag6L3F (3.28–3.30 vs 3.44–3.51 Å in the case of Cu6L3H), indicating substantial intramolecular closed-shell Ag(d10)–Ag(d10) interactions. However, Cu6L3H features close intermolecular Cu···Cu contacts as short as 3.37 Å. Mössbauer data for both the ligands and complexes were collected, and electrochemical properties were measured; preliminary luminescence data are reported.
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