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Author: Popov, Alexey A. × End date: 2022 × Start date: 2022 × Publisher: Washington, DC : ACS Publications ×

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Now showing 1 - 3 of 3
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    Optical Anisotropy and Momentum-Dependent Excitons in Dibenzopentacene Single Crystals
    (Washington, DC : ACS Publications, 2022) Graf, Lukas; Liu, Fupin; Naumann, Marco; Roth, Friedrich; Debnath, Bipasha; Büchner, Bernd; Krupskaya, Yulia; Popov, Alexey A.; Knupfer, Martin
    High-quality single crystals of the organic semiconductor (1,2;8,9)-dibenzopentacene were grown via physical vapor transport. The crystal structure─unknown before─was determined by single-crystal X-ray diffraction; polarization-dependent optical absorption measurements display a large anisotropy in the ac plane of the crystals. The overall Davydov splitting is ∼110 meV, which is slightly lower than that in the close relative pentacene (120 meV). Momentum-dependent electron energy-loss spectroscopy measurements show a clear exciton dispersion of the Davydov components. An analysis of the dispersion using a simple 1D model indicates smaller electron- and hole-transfer integrals in dibenzopentacene as compared to pentacene. The spectral weight distribution of the excitation spectra is strongly momentum-dependent and demonstrates a strong momentum-dependent admixture of Frenkel excitons, charge-transfer excitons, and vibrational modes.
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    Triangular Monometallic Cyanide Cluster Entrapped in Carbon Cage with Geometry-Dependent Molecular Magnetism
    (Washington, DC : ACS Publications, 2016) Liu, Fupin; Gao, Cong-Li; Deng, Qingming; Zhu, Xianjun; Kostanyan, Aram; Westerström, Rasmus; Wang, Song; Tan, Yuan-Zhi; Tao, Jun; Xie, Su-Yuan; Popov, Alexey A.; Greber, Thomas; Yang, Shangfeng
    Clusterfullerenes are capable of entrapping a variety of metal clusters within carbon cage, for which the entrapped metal cluster generally keeps its geometric structure (e.g., bond distance and angle) upon changing the isomeric structure of fullerene cage, and whether the properties of the entrapped metal cluster is geometry-dependent remains unclear. Herein we report an unusual triangular monometallic cluster entrapped in fullerene cage by isolating several novel terbium cyanide clusterfullerenes (TbNC@C82) with different cage isomeric structures. Upon varying the isomeric structure of C82 cage from C2(5) to Cs(6) and to C2v(9), the entrapped triangular TbNC cluster exhibits significant distortions as evidenced by the changes of Tb–C(N) and C–N bond distances and variation of the Tb–C(N)–N(C) angle by up to 20°, revealing that the geometric structure of the entrapped triangular TbNC cluster is variable. All three TbNC@C82 molecules are found to be single-ion magnets, and the change of the geometric structure of TbNC cluster directly leads to the alternation of the magnetic relaxation time of the corresponding TbNC@C82 clusterfullerene.
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    (BB)-Carboryne Complex of Ruthenium: Synthesis by Double B-H Activation at a Single Metal Center
    (Washington, DC : ACS Publications, 2016) Eleazer, Bennett J.; Smith, Mark D.; Popov, Alexey A.; Peryshkov, Dmitry V.
    The first example of a transition metal (BB)-carboryne complex containing two boron atoms of the icosahedral cage connected to a single exohedral metal center (POBBOP)Ru(CO)2 (POBBOP = 1,7-OP(i-Pr)2-2,6-dehydro-m-carborane) was synthesized by double B-H activation within the strained m-carboranyl pincer framework. Theoretical calculations revealed that the unique three-membered (BB)>Ru metalacycle is formed by two bent B-Ru σ-bonds with the concomitant increase of the bond order between the two metalated boron atoms. The reactivity of the highly strained electron-rich (BB)-carboryne fragment with small molecules was probed by reactions with electrophiles. The carboryne-carboranyl transformations reported herein represent a new mode of cooperative metal-ligand reactivity of boron-based complexes.