title: Quantitative analysis of intermolecular interactions in orthorhombic rubrene.
abstract: Rubrene is one of the most studied organic semiconductors to date due to its high charge carrier mobility which makes it a potentially applicable compound in modern electronic devices. Previous electronic device characterizations and first principles theoretical calculations assigned the semiconducting properties of rubrene to the presence of a large overlap of the extended π-conjugated core between molecules. We present here the electron density distribution in rubrene at 20 K and at 100 K obtained using a combination of high-resolution X-ray and neutron diffraction data. The topology of the electron density and energies of intermolecular interactions are studied quantitatively. Specifically, the presence of Cπ⋯Cπ interactions between neighbouring tetracene backbones of the rubrene molecules is experimentally confirmed from a topological analysis of the electron density, Non-Covalent Interaction (NCI) analysis and the calculated interaction energy of molecular dimers. A significant contribution to the lattice energy of the crystal is provided by H-H interactions. The electron density features of H-H bonding, and the interaction energy of molecular dimers connected by H-H interaction clearly demonstrate an importance of these weak interactions in the stabilization of the crystal structure. The quantitative nature of the intermolecular interactions is virtually unchanged between 20 K and 100 K suggesting that any changes in carrier transport at these low temperatures would have a different origin. The obtained experimental results are further supported by theoretical calculations.
authors: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University , Langelandsgade 140, Aarhus C DK-8000, Denmark.
authors: Venkatesha R
authors: VR
authors: Hathwar
authors: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University , Langelandsgade 140, Aarhus C DK-8000, Denmark.
authors: Mattia
authors: M
authors: Sist
authors: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University , Langelandsgade 140, Aarhus C DK-8000, Denmark.
authors: Mads R V
authors: MR
authors: Jørgensen
authors: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University , Langelandsgade 140, Aarhus C DK-8000, Denmark.
authors: Aref H
authors: AH
authors: Mamakhel
authors: Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , PO Box 2008 - MS 6475, Oak Ridge, TN 37831, USA.
authors: Xiaoping
authors: X
authors: Wang
authors: Chemical and Engineering Materials Division, Neutron Sciences Directorate, Oak Ridge National Laboratory , PO Box 2008 - MS 6475, Oak Ridge, TN 37831, USA.
authors: Christina M
authors: CM
authors: Hoffmann
authors: Japan Synchrotron Radiation Research Institute , I-I-I, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
authors: Kunihisa
authors: K
authors: Sugimoto
authors: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University , Langelandsgade 140, Aarhus C DK-8000, Denmark.
authors: Jacob
authors: J
authors: Overgaard
authors: Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University , Langelandsgade 140, Aarhus C DK-8000, Denmark.
authors: Bo Brummerstedt
authors: BB
authors: Iversen
keywords: electron density; interaction energy; organic semiconductor; rubrene