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Electron Distribution and Molecular Motion in Crystalline Benzene: An Accurate Experimental Study Combining CCD X‐ray Data on C 6 H 6 with Multitemperature Neutron‐Diffraction Results on C 6 D 6
Author(s) -
Bürgi HansBeat,
Capelli Silvia C.,
Goeta Andrés E.,
Howard Judith A. K.,
Spackman Mark A.,
Yufit Dmitrii S.
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020802)8:15<3512::aid-chem3512>3.0.co;2-z
Subject(s) - quadrupole , neutron diffraction , crystal (programming language) , chemistry , multipole expansion , charge density , atomic physics , molecular physics , crystal structure , crystallography , physics , quantum mechanics , computer science , programming language
The electronic properties of the benzene molecule, for example its quadrupole moment and the electric field gradients (EFG's) at the H nuclei, are of fundamental importance in theoretical and experimental chemistry. With this in mind, single‐crystal X‐ray diffraction data on C 6 H 6 were collected with a charge‐coupled device detector at T ≈110 K. As accurate modelling of the thermal motion in the crystal was regarded as vital, especially for the hydrogen atoms, anisotropic‐displacement parameters (ADP's) for the C and H atoms in C 6 H 6 were derived in a straightforward fashion from analysis of the temperature dependence of ADP's for the C and D atoms in C 6 D 6 at 15 K and 123 K obtained by neutron diffraction. Agreement between C‐atom ADP's derived from thermal‐motion analysis of neutron data and those obtained from multipole refinement by using the X‐ray data is extraordinarily good; this gives confidence in the modelling of vibrational motion for the H atoms. The molecular quadrupole moment derived from the total charge density of the molecule in the crystal is (−29.7±2.4)×10 −40 C m 2 , in excellent agreement with measurements made in the gas phase and in solution. The average deuterium nuclear quadrupole coupling constant (DQCC) derived from EFG tensors at H atoms is 182±17 kHz, also in excellent agreement with independent measurements. The strategy employed in this work may be of more general applicability for future accurate electron density studies.