Oleg Dolomanov

OLEX2: a complete structure solution, refinement and analysis program

New software, OLEX2, has been developed for the determination, visualization and analysis of molecular crystal structures. The software has a portable mouse-driven workflow-oriented and fully comprehensive graphical user interface for structure solution, refinement and report generation, as well as novel tools for structure analysis. OLEX2 seamlessly links all aspects of the structure solution, refinement and publication process and presents them in a single workflow-driven package, with the ultimate goal of producing an application which will be useful to both chemists and crystallographers.

The anatomy of a comprehensive constrained, restrained refinement program for the modern computing environment - Olex2 dissected

An in-depth presentation is given of olex2.refine, the new refinement engine integrated in the Olex2 program.

iotbx.cif: a comprehensive CIF toolbox

iotbx.cif is a comprehensive toolbox for the development of applications that make use of the CIF format.

OLEX2 – a complete package for molecular crystallography

Structure Refinement can be carried out with olex2.refine. The refinement engine is based on the cctbx and provides all the functionality required for a meaningful structure refinement. A general system allows the implementation of any constraint, which has been used to provide all ShelXL constraints as well as some new constraints. All ShelX restraints have also been implemented. Of course, ShelXL can be chosen as the refinement engine as an alternative to olex2.refine.

Probing the accuracy and precision of Hirshfeld atom refinement with HARt interfaced with Olex2

Anisotropic atomic displacement parameters obtained separately from highly accurate X-ray and neutron diffraction data are compared, and it is established that Hirshfeld atom refinement of X-ray data can provide structural parameters that are as accurate as those from neutron data.

Electronic interactions in 1D-π-assemblies from TLS analysis of thermal motion

Advanced features of TLS analysis within Olex2 program package allow for a detailed analysis of electronic redistribution in supramolecular systems. Particularly, the possibility of calculating TLS tensors in user-defined coordinate systems along with qualitative graphical representation of difference thermal motion are especially useful for analysis of atomic asphericity and intraand inter-molecular electron redistribution. In addition, these features allow for a directional dynamic analysis of intermolecular motions from variable-temperature experiments. We explored the exciting new possibilities analyzing supramolecular assemblies closely resembling modern electronic materials for a series of electron donor-acceptor complexes and ion-radical salts based on aromatic octamethyl-anthracene and anti-aromatic octamethyl-biphenylene substrates. The difference TLS analysis revealed intimate details of chemical bond polarization and electronic shell expansion for acceptor components along with electronic shell contraction for donor components of the complexes indicative of intraand intermolecular charge transfer. Also, the variable-temperature analysis of relative thermal motion of the complex components in the crystals revealed some widening of the potential-energy minima in direction of the electronic overlap as a result of intermolecular pi-orbital coupling both in charge-transfer and charge-resonance supramolecular assemblies. A theoretical interpretation of the observed peculiarities was undertaken supported by respective spectroscopic data.

Small-molecule refinement using the computational crystallography toolbox (cctbx) withOLEX2

improvement of the refinement can be obtained by eliminating the badly fitted reflections and/or by correcting the model, which could be too inaccurate or involve too subtle features to be modelled depending on the quality of the observations processed. A successfully recognition of the actually influencing reflections is represented by some statistical estimators based on leverage analysis (Belsey et al., 1980, Merli, 2005). Among several exploitable estimators, there are some of them that seem to be particularly suitable in crystallographic calculations: i) Cook distance (Cook, 1977), ii) DFFTIS and iii) DFBETASij (Belsey et al., 1980). In particular, estimator i) can be used to recognize an actual outlier of the refinement, whereas estimator ii) is useful to investigate the effects when a reflection is eliminated from the data set and iii) is able to recognize the variables that are mostly influenced by each reflection. The combined analysis of these diagnostics will be presented. It will be shown how successfully it yields to the recognition of a dangerous reflection and/or the inaccurate estimate of any particular variable. Belsey, Kuth & Welsh (1980) Regression diagnostics. J. Wiley & Sons Cook(1977) Technometrics, 19, 15-18 Merli (2005) Acta Cryst. A61, 471-477