Related Experiment Video
Updated: Feb 27, 2026
The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes
Published on: April 10, 2015
Synchronized Collective Proton-Assisted Electron Transfer in Solid State by Hydrogen-Bonding Ru(II)/Ru(III)
Makoto Tadokoro1,2, Hiroyuki Hosoda1, Tomonori Inoue2
1Department of Chemistry, Faculty of Science, Tokyo University of Science , Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan.
Abstract:
A proton-coupled electron transfer (PCET) reaction was widely studied with isolated organic molecules and metal complexes in solution in view of the biological catalytic reaction, while studying this reaction in the crystalline or solid-state phase, which has a novel example, would give insight into the rather internal environment of proteins without solvation and a creation of new molecular materials. We tried to crystallize a hydrogen-bonded (H-bonded) coordination polymer with one-dimensional nanoporous channels, formed from redox-active RuIII complexes, [RuIII(Hbim)3] (Hbim- = 2,2'-biimidazolate monoanion). As a result, a synchronized collective PCET phenomenon was observed for the molecular nanoporous crystal by novel solid-state cyclic voltammetry (CV), which could be measured by only setting some crystals on the electrode surface. The nanoporous crystals, {[RuIII(Hbim)3]}n (1), are simultaneously induced to a synchronized collective RuIIRuIII mixed-valence state, {RuIIRuIII}n, with alternating arrays of RuII and RuIII complexes by PCET in a way of the reductive state of {RuIIRuII}n. Further, a new crystal with {RuIIRuIII}n, {[RuII(H2bim)(Hbim)2][RuIII(bim) (Hbim)2][K(MeOBz)6]}n (2), was also prepared, and the solid-state CV revealed the same electrochemical behavior of {RuIIRuIII}n with 1. The single crystal with {RuIIRuIII}n of 2 was unusually a semiconductor with 5.12 × 10-6 S/cm conductivity at 298 K by an impedance method (8.01 × 10-6 S/cm by a direct-current method at 277 K). Thus, an unprecedented electron-hopping conductor driven by a low-barrier proton transfer through a PCET mechanism (Ea = 0.30 eV) was realized in the H-bonding molecular crystal with {RuIIRuIII}n. Such studies on a PCET reaction in the crystalline state is not only worthwhile as a model of essential biological reactions without solvation, but also proposed to a new design of molecular materials to occur an electron transfer by using an intermolecular H-bond.
Related Concept Videos
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:42Valence Bond Theory
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
03:51Molecular Orbital Theory II
03:02Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
02:54Molecular and Ionic Solids
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...