Rate and Mechanistic Investigation of Eu(OTf)₂‑Mediated Reduction of Graphene Oxide at Room Temperature

We describe a fast, efficient, and mild approach to prepare chemically reduced graphene oxide (rGO) at room temperature using divalent europium triflate {Eu­(OTf)₂}. The characterization of solution-processable reduced graphene oxide has been carried out by various spectroscopic (FT-IR, UV–visible absorption, and Raman), microscopic (TEM and AFM), and powder X-ray diffraction (XRD) techniques. Kinetic study indicates that the bimolecular rate constants for the reduction of graphene oxide are 13.7 ± 0.7 and 5.3 ± 0.1 M^–1 s^–1 in tetrahydrofuran (THF)–water and acetonitrile (ACN)–water mixtures, respectively. The reduction rate constants are <i>two orders</i> of magnitude higher compared to the values obtained in the case of commonly used reducing agents such as the hydrazine derivative, sodium borohydride, and a glucose–ammonia mixture. The present work introduces a feasible reduction process for preparing reduced graphene oxide at ambient conditions, which is important for bulk production of GO. More importantly, the study explores the possibilities of utilizing the unique chemistry of divalent lanthanide complexes for chemical modifications of graphene oxide

Effect of Crown Ethers on the Ground and Excited State Reactivity of Samarium Diiodide in Acetonitrile

Electron transfer from the ground and excited states of Sm­[15-crown-5]₂I₂ complex to a series of electron acceptors (benzaldehyde, acetophenone, benzophenone, nitrobenzene, benzyl bromide, benzyl chloride, 1-iodohexane, and 1,4-dinitrobenzene) was investigated in acetonitrile. Electron transfer from the ground state of the Sm­(II)-crown system to aldehydes and ketones has a significant inner sphere component indicating that the oxophilic nature of Sm­(II) prevails in the system even in the presence of bulky ligands such as 15-crown-5 ether. Activation parameters for the ground state electron transfer were determined, and the values were consistent with the proposed mechanistic models. Since crown ethers stabilize the photoexcited states of Sm­(II), the photochemistry of Sm­[15-crown-5]₂I₂ system in solution state has been investigated in detail. The results suggest that photoinduced electron transfer from Sm­(II)-crown systems to a wide variety of substrates is feasible with rate constant values as high as 10⁷ M^–1 s^–1. The results described herein imply that the present difficulty of manipulating the extremely reactive excited state of Sm­(II) in solution phase can be overcome through stabilizing the excited state of the divalent metal ion by careful design of the ligand systems