Graph-Set Analysis Helps To Understand Charge Transfer in a Novel Ionic Cocrystal When the ΔpKa Rule Fails

2019 ◽  
Vol 19 (9) ◽  
pp. 5308-5313 ◽  
Author(s):  
Oisín N. Kavanagh ◽  
Gavin Walker ◽  
Matteo Lusi
Keyword(s):  
Charge Transfer ◽  
Graph Set ◽  
Graph Set Analysis

Polymorphism of urea–barbituric acid co-crystals

2008 ◽  
Vol 64 (5) ◽  
pp. 623-632 ◽  
Author(s):  
Marlena Gryl ◽  
Anna Krawczuk ◽  
Katarzyna Stadnicka
Keyword(s):  
Barbituric Acid ◽  
Spatial Arrangement ◽  
Structural Components ◽  
Space Groups ◽  
The Third ◽  
Tautomeric Forms ◽  
Polymorphic Forms ◽  
Graph Set ◽  
Graph Set Analysis ◽  
Level Analysis

The crystal structures of three polymorphs found for the addition complex of urea and barbituric acid are described and compared. Two polymorphs are monoclinic, space groups P21/c and Cc, whereas the third is triclinic, P\bar 1. The displacement of electron density towards the mesomeric forms, corresponding to the tautomeric forms of higher stability, of the barbituric acid molecule seem to influence the type of hydrogen bonds formed, which in turn determines the different packing topology in the polymorphs. While the polymorphic forms can be easily differentiated at the first-level graph-set analysis of their hydrogen-bonding patterns, a higher-level analysis enables important features of the mutual spatial arrangement of the structural components to be revealed.

Graph-set and packing analysis of hydrogen-bonded networks in polyamide structures in the Cambridge Structural Database

2000 ◽  
Vol 56 (5) ◽  
pp. 857-871 ◽  
Author(s):  
W. D. Samuel Motherwell ◽  
Gregory P. Shields ◽  
Frank H. Allen
Keyword(s):  
Crystal Packing ◽  
Three Dimensional ◽  
Cambridge Structural Database ◽  
Dimensional Network ◽  
Hydrogen Bond Networks ◽  
Structural Database ◽  
Graph Set ◽  
Graph Set Analysis ◽  
Packing Analysis ◽  
Hydrogen Bonded

The hydrogen-bond networks and crystal packing of 81 unique secondary di- and polyamides in the Cambridge Structural Database are investigated. Graph-set analysis, as implemented in the RPluto program, is used to classify network motifs. These have been rationalized in terms of the relative dispositions of the amide groups. Peptide and retropeptides exhibit significant conformational flexibility, which permits alternative hydrogen-bonding patterns. In peptides, dihedral angles of −ψ ≃ φ ≃ 105° allow an antiparallel ladder arrangement, containing rings of either the same or alternating sizes. For retropeptides, and diamides with an odd number of CH2 spacers, this conformation leads to a parallel ladder with rings of equal size. If φ approaches −60° and ψ 180°, ladders adopt a helical twist, and if the conformation is distorted further, a three-dimensional network is usually adopted. Diamides with aromatic or an even number of CH2 spacers generally form either antiparallel ladders or sheets, although some exhibit both polymorphs. Symmetry relationships within and between hydrogen-bonded chains, ladders and sheets in the crystal packing have also been analysed. Polyamides form considerably more complex networks, although many of the structural motifs present in the diamides occur as components of these networks.

scholarly journals Characterization of Supramolecular Hidden Chirality of Hydrogen-Bonded Networks by Advanced Graph Set Analysis

2014 ◽  
Vol 20 (9) ◽  
pp. 2392-2392
Author(s):  
Toshiyuki Sasaki ◽  
Yoko Ida ◽  
Ichiro Hisaki ◽  
Tetsuharu Yuge ◽  
Yoshiaki Uchida ◽  
...  
Keyword(s):  
Graph Set ◽  
Graph Set Analysis ◽  
Hydrogen Bonded
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