Preparation, Characterization, Molecular and Electronic Structures, TDDFT, and TDDFT/PCM Study of the Solvatochromism in Cyanovinylferrocenes

Cis and trans isomers of ferrocene-based donor−acceptor assemblies, Fc−C(I)CH(I), Fc−C(I)CH(CN), and
Fc−C(CN)CH(CN) (Fc is ferrocene), along with the Fc−C(CN)C(CN)2 complex have been prepared and
characterized by 1H, 13C, gHMQC, and gHMBC NMR spectra, IR, UV−vis, and MCD spectroscopy methods, as
well as elemental analyses. The oxidation potentials, investigated by cyclic voltammetry, of all donor−acceptor
assemblies are in agreement with the electron-acceptor strength of the substituents attached to the ferrocene core.
X-ray crystallography studies of cis and trans isomers of Fc−C(I)CH(CN) and Fc−C(CN)CH(CN) reveal a
significant rotational flexibility of the cyanovinyl group, which was explained on the basis of semiempirical PM3
calculations. Electronic structures and solvatochromic properties of all complexes were investigated by UV−vis
spectroscopy, density functional theory (DFT), time-dependent DFT (TDDFT), and polarized continuum model (PCM)
TDDFT approaches. The calculated vertical excitation energies and magnitudes of solvatochromic effect are consistent
with the experimental data and clearly suggest the dominance of metal-to-ligand charge-transfer bands in the
visible region of the UV−vis spectra for all complexes.