Refcodes Used

From the Cambridge Structural Database for short-format references, see Appendix B 

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REFCODES used in the text are listed with biographical information at the end of this book. 

The Cambridge Crystallographic Data Base was an indispensible source of data and we are grateful for permission to use the Refcodes for indexing. 

In the following sections, our first-principles bottom-up methodology will be described from a physical perspective (a full description on mathematical terms can be found in Ref. [7]). Then, the use of this methodology will be illustrated on the a-2-hydro nitronyl nitroxide [8] (hereafter called a-HNN), the simplest member of the nitronyl nitroxide family (R = H in Figure 1). The macroscopic magnetic properties and crystal structure of this compound are well known (its crystal structure is stored in the Cambridge Crystallographic Database [9] with refcode name TOLKEK). 

Table A.2. Table of average bond lengths in organometallic compounds and coordination complexes of the d- and f-block metals (The following special symbols are used (tt) Refer to the full publication [10] for more complete information, including CSD refcodes and short format references to most excluded values (t) See Figure A.5 ( ) Cluster complexes, no coordination number assigned.) The numbers in column Note refer to the entries in Table A.5...

These molecules are chosen fairly randomly from the set of small organic, essentially rigid molecules containing C, H, N and O only, where an approximately room temperature (T ) and low temperature (T2) crystal structure is available. The crystal structures used are denoted by their refcodes in the Cambridge Structural Database. The contractions are defined by ... 

As an example, application of IsoQuest to the compound PhsSiCl [CSD refcode (Nov 2006 version) BARNUD] yields a list of 16 CSD entries, of which 12 are unique structures (Table 1.3) [48]. It is noticeable that the list contains structures determined at different temperatures, illustrating the ability of the WCC procedure to handle temperature-related shifts in peak positions. There are also instances of triclinic structures with unit cells half the volume of the monoclinic structures. These would not have been identified by a standard ConQuest search using the reduced cell. Overlaying the monoclinic and triclinic structures (Figure 1.13) shows clearly the structural similarity-the... 

Table 1.3 Results of an IsoQuest search using the compound PhsSiCI [CSD refcode (Nov. 2006 version) BARNUD], listed according to decreasing similarity. The structure of BARNUD is reported in the nonstandard space group P2iA). The triclinic unit cells have half the volume of the monoclinic unit cells...

In an effort to develop a fully automated procedure that can be used to screen the entire CSD, van de Streek and Motherwell considered that some CSD entries are likely to contain errors, which are more likely to be in the atomic coordinates than in the unit-cell parameters. To eliminate the contribution of the unit-cell contents, the structure factor of each reflection in the simulated PXRD profile was set to an arbitrary constant value, thereby producing a normalised reduced-cell PXRD profile that was used for comparison using the WCC procedure. Applying this methodology to the CSD prior to November 2004 produced a list of 2862 unique refcode families which contain reliable pairs of polymorphic structures, amounting to ca. 1 % of all unique chemical compounds in the CSD. Numerous strict criteria were applied in the process, so that the list represents a minimum number of reliable observations rather than an exhaustive list. 

Figure 2.3 Overlay of the X-ray determined crystal structure (black) [23] of oxazolidlne-2,5-dione (CSD refcode OXAZDO) and the lowest energy predicted crystal structure after lattice energy minimization using an atomic multipole-based model potential (grey)...

CrystalLographic data were retrieved from the Cambridge Structure Database (CSD). References to structures (REFCODE) are provided in itahc capital letters. Powder diffractograms have been simulated on the basis of the coordinates deposited in the CSD using the Mercury program." ... 

Two example structures, one coordination polymer containing [Zn(isonicotinato)2] (CSD refcode VACFUB)[1] and a hydrogen bonded net of 3,3, 5,5 -tetramethyl-4,4 -bipyrazolyl (CSD refcode UDAYUT) [2], will be employed to explain how to use these programs. The 2D and 3D views of both structures can be found in Figures 13.1-2. Since all programs are not suited to analyse both types of nets, both examples are not used with all software. 

The majority of the top ten structures found using an all-path search for AADRIB, a fairly small-sized, cycHc structure with acychc side chains, were very similar to the query (again, the query structure, and the two other occurrences of the structure under different refcodes in the file, were ranked to the top of the hst). 

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