Acta Crystallographica Section E: Crystallographic Communications 

About: Acta Crystallographica Section E: Crystallographic Communications is an academic journal published by International Union of Crystallography. The journal publishes majorly in the area(s): Crystal structure & Ring (chemistry). It has an ISSN identifier of 2056-9890. It is also open access. Over the lifetime, 4032 publications have been published receiving 9279 citations. The journal is also known as: Crystallographic communications.

checkCIF validation ALERTS: what they mean and how to respond.

Abstract: Authors of a paper that includes a new crystal-structure determination are expected to not only report the structural results of inter­est and their inter­pretation, but are also expected to archive in computer-readable CIF format the experimental data on which the crystal-structure analysis is based. Additionally, an IUCr/checkCIF validation report will be required for the review of a submitted paper. Such a validation report, automatically created from the deposited CIF file, lists as ALERTS not only potential errors or unusual findings, but also suggestions for improvement along with inter­esting information on the structure at hand. Major ALERTS for issues are expected to have been acted on already before the submission for publication or discussed in the associated paper and/or commented on in the CIF file. In addition, referees, readers and users of the data should be able to make their own judgment and inter­pretation of the underlying experimental data or perform their own calculations with the archived data. All the above is consistent with the FAIR (findable, accessible, inter­operable, and reusable) initiative [Helliwell (2019). Struct. Dyn. 6, 05430]. Validation can also be helpful for less experienced authors in pointing to and avoiding of crystal-structure determination and inter­pretation pitfalls. The IUCr web-based checkCIF server provides such a validation report, based on data uploaded in CIF format. Alternatively, a locally installable checkCIF version is available to be used iteratively during the structure-determination process. ALERTS come mostly as short single-line messages. There is also a short explanation of the ALERTS available through the IUCr web server or with the locally installed PLATON/checkCIF version. This paper provides additional background information on the checkCIF procedure and additional details for a number of ALERTS along with options for how to act on them.

Utilizing Hirshfeld surface calculations, non-covalent inter­action (NCI) plots and the calculation of inter­action energies in the analysis of mol­ecular packing

Abstract: The analysis of atom-to-atom and/or residue-to-residue contacts remains a favoured mode of analysing the mol­ecular packing in crystals. In this contribution, additional tools are highlighted as methods for analysis in order to complement the `crystallographer's tool', PLATON [Spek (2009). Acta Cryst. D65, 148–155]. Thus, a brief outline of the procedures and what can be learned by using Crystal Explorer [Spackman & Jayatilaka (2009). CrystEngComm 11, 19–23] is presented. Attention is then directed towards evaluating the nature, i.e. attractive/weakly attractive/repulsive, of specific contacts employing NCIPLOT [Johnson et al. (2010). J. Am. Chem. Soc. 132, 6498–6506]. This is complemented by a discussion of the calculation of energy frameworks utilizing the latest version of Crystal Explorer. All the mentioned programs are free of charge and straightforward to use. More importantly, they complement each other to give a more complete picture of how mol­ecules assemble in mol­ecular crystals.

Structural characterization and Hirshfeld surface analysis of a CoII complex with imidazo[1,2-a]pyridine.

Abstract: A new mononuclear tetra­hedral CoII complex, di­chlorido­bis­(imidazo[1,2-a]pyridine-κN1)cobalt(II), [CoCl2(C7H6N2)2], has been synthesized using a bioactive imidazo­pyridine ligand. X-ray crystallography reveals that the solid-state structure of the title complex exhibits both C—H⋯Cl and π–π stacking inter­actions in building supra­molecular assemblies. Indeed, the mol­ecules are linked by C—H⋯Cl inter­actions into a two-dimensional framework, with finite zero-dimensional dimeric units as building blocks, whereas π–π stacking plays a crucial role in building a supra­molecular layered network. An exhaustive investigation of the diverse inter­molecular inter­actions via Hirshfeld surface analysis enables contributions to the crystal packing of the title complex to be qu­anti­fied. The fingerprint plots associated with the Hirshfeld surface clearly display each significant inter­action involved in the structure, by qu­anti­fying them in an effective visual manner.

Formamidinium iodide: crystal structure and phase transitions.

Abstract: At a temperature of 100 K, CH5N2+·I− (I), crystallizes in the monoclinic space group P21/c. The formamidinium cation adopts a planar symmetrical structure [the r.m.s. deviation is 0.002 A, and the C—N bond lengths are 1.301 (7) and 1.309 (8) A]. The iodide anion does not lie within the cation plane, but deviates from it by 0.643 (10) A. The cation and anion of I form a tight ionic pair by a strong N—H⋯I hydrogen bond. In the crystal of I, the tight ionic pairs form hydrogen-bonded zigzag-like chains propagating toward [20-1] via strong N—H⋯I hydrogen bonds. The hydrogen-bonded chains are further packed in stacks along [100]. The thermal behaviour of I was studied by different physicochemical methods (thermogravimetry, differential scanning calorimetry and powder diffraction). Differential scanning calorimetry revealed three narrow endothermic peaks at 346, 387 and 525 K, and one broad endothermic peak at ∼605 K. The first and second peaks are related to solid–solid phase transitions, while the third and fourth peaks are attributed to the melting and decomposition of I. The enthalpies of the phase transitions at 346 and 387 K are estimated as 2.60 and 2.75 kJ mol−1, respectively. The X-ray powder diffraction data collected at different temperatures indicate the existence of I as the monoclinic (100–346 K), ortho­rhom­bic (346–387 K) and cubic (387–525 K) polymorphic modifications.

Crystal structures of spinel-type Na2MoO4 and Na2WO4 revisited using neutron powder diffraction

Abstract: Time-of-flight neutron powder diffraction data have been collected from Na2MoO4 and Na2WO4 to a resolution of sin (θ)/λ = 1.25 A−1, which is substanti­ally better than the previous analyses using Mo Kα X-rays, providing roughly triple the number of measured reflections with respect to the previous studies [Okada et al. (1974). Acta Cryst. B30, 1872–1873; Bramnik & Ehrenberg (2004). Z. Anorg. Allg. Chem. 630, 1336–1341]. The unit-cell parameters are in excellent agreement with literature data [Swanson et al. (1962). NBS Monograph No. 25, sect. 1, pp. 46–47] and the structural parameters for the molybdate agree very well with those of Bramnik & Ehrenberg (2004). However, the tungstate structure refinement of Okada et al. (1974) stands apart as being conspicuously inaccurate, giving significantly longer W—O distances, 1.819 (8) A, and shorter Na—O distances, 2.378 (8) A, than are reported here or in other simple tungstates. As such, this work represents an order-of-magnitude improvement in precision for sodium molybdate and an equally substantial improvement in both accuracy and precision for sodium tungstate. Both compounds adopt the spinel structure type. The Na+ ions have site symmetry .-3m and are in octa­hedral coordination while the transition metal atoms have site symmetry -43m and are in tetra­hedral coordination.