Benzene and tropilium metal complexes. Intra- and intermolecular interaction evidenced by vibrational analysis: The blue-shift hydrogen bond

Vibrational IR and Raman spectra of several organometallic complexes of benzene and tropyilium have been investigated. Comparisons between the vibrational features of free and coordinated ligands and between solution and solid-state spectra of the complexes have been performed. Similar sets of bands observed in the typical diagnostic regions suggest a weak kinematic coupling between the ligand vibrational modes. The high sensitivity of the frequency of the vibrations to electron charge density distributed throughout the complexes provides evidence of the intermolecular interactions characterizing the solid-state architecture. Noteworthy are the different types of C-H⋯X hydrogen bond, displaying both the blue- and red-shift of the CH stretching vibrations.