As the processing and curation of CSD structures takes a finite and not insignificant period of time, the CCDC has decided to take advantage of the new Web-based architecture in WebCSD and start releasing structures to the public before they are fully curated. These structures have been automatically processed using our specialist in-house software to ensure a certain level of quality, but may not have had any manual input. As they have not been fully processed by a CCDC editor yet it is likely that some will contain errors and some of the entries won't contain fields that are added during the curation process, such as 'recrystallisation solvent' and 'bioactivity'. New structures will be added in batches on a regular basis as they are received and these uncurated structures will appear in WebCSD as a separate database designated "CSD X-Press". The intention is that the early access to these structures will be beneficial to users in spite of the possible errors in the "Structures Pending", especially in the handling of disorder and diagram generation.

More about Structures Pending:

  • CSD X-Press: The structures that are pending curation are kept in a separate database within the WebCSD architecture named "CSD X-Press". This means that it is simple to perform searches or extract results based on only the fully curated CSD, only the structures pending, or both sets of structures using the checkboxes provided in the Settings tab of WebCSD.
  • Refcode Format: The reference code for a regular CSD structure has the format of six letters followed by an optional two digits (e.g. AABHTZ or AACRUB01). For structures pending, the temporary refcodes assigned will always end in '00' to indicate that the structure has not yet been fully curated. Please bear in mind that these refcodes are temporary and the code will either be changed completely or the '00' will be removed.
  • Citing a Structure Pending: If you would like to refer to a CSD X-Press entry within a scientific publication, please report the CCDC reference number (e.g. CCDC 747743) rather than the temporary refcode. For example use one of the following styles:
    • For published structures, write in the body text "(CCDC 747743)", then cite the original paper in your references section.
    • Or, for CSD Communications use a reference like so: "S. Parsons, C. Grant, R. Winpenny, R. Gould & P. Wood (2004). Private communication to CSD, CCDC 248052".
  • Reliability Score: This score indicates the level of reliability assigned automatically to a structure based on the curation status of the entry and the likelihood of complications in the automatic processing. The reliability score does not reflect the quality of the crystallography/science and is purely based on the difficulty of processing the particular entry.
    • 4 stars (****) are given to all fully curated entries in the main CSD. This rating represents a wide-ranging set of professionally-edited structures containing molecules with a broad level of complexity.
    • 3 stars (***) will be given to CSD X-Press entries which encountered a low number of complications during automatic processing and typically represent entries with simple chemistry/crystallography.
    • 2 stars (**) will be given to CSD X-Press entries for which a moderate number of automatic processing problems were discovered, normally representing entries with more complicated chemistry/crystallography.
    • 1 star (*) will be given to CSD X-Press entries for which a high number of automatic processing problems were discovered, normally representing larger entries with complex chemistry/crystallography.

Entries can be sorted on reliability score in the Results Browser applet by clicking on the 'Reliability' column heading.

  • 2D Diagrams: If there is a match in the CSD based on structural topology, the chemical diagram for this match will be used as a template - the majority of 2D diagrams are derived using this method. Diagram generation for any new structural topologies is automated using Marvin (a ChemAxon package); entries for which acceptable diagrams cannot be automatically generated are simply shown with no diagram. The automatically generated diagrams do not necessarily reflect the exact 3D geometry of the structure.
  • Compound Name: This field will be populated if anything has been supplied in the author's original deposited CIF, or if a name can be generated automatically using ACD/Name Batch (an ACD/Labs product) based on the chemical connectivity. Clearly any automatically generated compound names will be subject to possible errors, especially in the case of disordered structures or highly complicated connectivities.
  • Disorder: Any disorder will be identified and processed automatically, but it is likely that some structures will require manual checking and editing to fully characterise the disorder.
  • Feedback: If you have any questions or comments relating to this new functionality, please e-mail the CSD X-Press Team at

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