TY - JOUR
T1 - Hirshfeld atom refinement for modelling strong hydrogen bonds
AU - Woinska, Magda
AU - Jayatilaka, Dylan
AU - Spackman, Mark
AU - Edwards, A.J.
AU - Dominiak, P.M.
AU - Woźniak, K.W.
AU - Nishibori, E.
AU - Sugimoto, K.
AU - Grabowsky, Simon
PY - 2014/9
Y1 - 2014/9
N2 - High-resolution low-temperature synchrotron X-ray diffraction data of the salt l-phenylalaninium hydrogen maleate are used to test the new automated iterative Hirshfeld atom refinement (HAR) procedure for the modelling of strong hydrogen bonds. The HAR models used present the first examples of Z′ > 1 treatments in the framework of wavefunction-based refinement methods. l-Phenylalaninium hydrogen maleate exhibits several hydrogen bonds in its crystal structure, of which the shortest and the most challenging to model is the O - H⋯O intramolecular hydrogen bond present in the hydrogen maleate anion (O⋯O distance is about 2.41Å). In particular, the reconstruction of the electron density in the hydrogen maleate moiety and the determination of hydrogen-atom properties [positions, bond distances and anisotropic displacement parameters (ADPs)] are the focus of the study. For comparison to the HAR results, different spherical (independent atom model, IAM) and aspherical (free multipole model, MM; transferable aspherical atom model, TAAM) X-ray refinement techniques as well as results from a low-temperature neutron-diffraction experiment are employed. Hydrogen-atom ADPs are furthermore compared to those derived from a TLS/rigid-body (SHADE) treatment of the X-ray structures. The reference neutron-diffraction experiment reveals a truly symmetric hydrogen bond in the hydrogen maleate anion. Only with HAR is it possible to freely refine hydrogen-atom positions and ADPs from the X-ray data, which leads to the best electron-density model and the closest agreement with the structural parameters derived from the neutron-diffraction experiment, e.g. the symmetric hydrogen position can be reproduced. The multipole-based refinement techniques (MM and TAAM) yield slightly asymmetric positions, whereas the IAM yields a significantly asymmetric position. © 2014 International Union of Crystallography.
AB - High-resolution low-temperature synchrotron X-ray diffraction data of the salt l-phenylalaninium hydrogen maleate are used to test the new automated iterative Hirshfeld atom refinement (HAR) procedure for the modelling of strong hydrogen bonds. The HAR models used present the first examples of Z′ > 1 treatments in the framework of wavefunction-based refinement methods. l-Phenylalaninium hydrogen maleate exhibits several hydrogen bonds in its crystal structure, of which the shortest and the most challenging to model is the O - H⋯O intramolecular hydrogen bond present in the hydrogen maleate anion (O⋯O distance is about 2.41Å). In particular, the reconstruction of the electron density in the hydrogen maleate moiety and the determination of hydrogen-atom properties [positions, bond distances and anisotropic displacement parameters (ADPs)] are the focus of the study. For comparison to the HAR results, different spherical (independent atom model, IAM) and aspherical (free multipole model, MM; transferable aspherical atom model, TAAM) X-ray refinement techniques as well as results from a low-temperature neutron-diffraction experiment are employed. Hydrogen-atom ADPs are furthermore compared to those derived from a TLS/rigid-body (SHADE) treatment of the X-ray structures. The reference neutron-diffraction experiment reveals a truly symmetric hydrogen bond in the hydrogen maleate anion. Only with HAR is it possible to freely refine hydrogen-atom positions and ADPs from the X-ray data, which leads to the best electron-density model and the closest agreement with the structural parameters derived from the neutron-diffraction experiment, e.g. the symmetric hydrogen position can be reproduced. The multipole-based refinement techniques (MM and TAAM) yield slightly asymmetric positions, whereas the IAM yields a significantly asymmetric position. © 2014 International Union of Crystallography.
U2 - 10.1107/S2053273314012443
DO - 10.1107/S2053273314012443
M3 - Article
C2 - 25176996
SN - 2053-2733
VL - A70
SP - 483
EP - 498
JO - Acta Crystallographica. Section A
JF - Acta Crystallographica. Section A
IS - 5
ER -