Dipole-Moment Modulation in New Incommensurate Ferrocene

Abstract

Despite 70 years of research on metallocenes and their applications, there are still unresolved regions in its phase diagram of the prototypic sandwich compound, ferrocene Fe2+[C5H5]− 2 (FeCp2), and its molecular 5-fold symmetry cannot be reconciled with the dielectric response of this crystal. We found a new phase I″ of ferrocene, which reveals the relationships between the molecular conformation, intermolecular interactions, and electric permittivity of this compound. Between 172.8 and 163.5 K, the conformational disorder of ferrocene molecules transforms into the incommensurate modulation. The structure of phase I″ is described in the (3+2)-dimensional superspace, where the molecular conformations, rotations and inclinations of the Cp rings, molecular tilts, and displacements of the Fe2+ cations, as well as the CH···π bonds in the crystal environment, are modulated. These geometric changes combine into the FeCp2 bending distortion, breaking the 5-fold symmetry and generating waves of molecular dipole moments with their amplitudes approaching 4 × 10–30 C·m.

Giant Deformation between Osmocene Phases Induced by Anagostic Bonds Promoted under High Pressure

“…However, the clearly lowest H-affinity of Fe corroborates the exceptional stability of this structure in the low-temperature region, as well as the preference for the high-pressure structure of phase I′-FeCp 2 dominated by hydrogen bonds CH···π . The dielectric response of ferrocene crystals, , as well as the conformational features recently revealed in the new modulated structure of phase I″ of ferrocene, suggests a contribution of dipole–dipole cohesion forces, which until recently were not considered. The weaker anagostic interactions and a stronger contribution of other types of cohesion forces can contribute to the presently known distinctly higher number of crystal phases (I, I′, I″, II, and III) of ferrocene compared to other simple metallocenes, e.g., only two phases are known for osmocene, ruthenocene, and nickelocene.…”

A theoretical study of ferrocene based on combined configuration interaction singles (CIS) and time-dependent density functional theory (TDDFT) approach

“…The investigation of Ferrocene proposed a new direction in computational science and build up a new organometallic compound with different characteristics. Various investigations show that Ferrocene is reactive and have potential applications in the field of material science [5][6][7][8][9][10][11][12][13][14][15][16][17]. The important utilization of Ferrocene and its other derivatives are smokeless combustion of fules [8], anti-oxidant and catalyst for various organic reaction [9] and different physical and atomic characteristics [10].…”