CrystEngComm Blog

Guanidinium-based synthons are useful for building ordered supramolecular structures due to their large number of charge-assisted hydrogen bonds (the guanidinium cation has 6 active H bonds). However, due to this plethora of potential intermolecular interactions, it can be a tricky to predict and design resultant structures – which is what crystal engineering is all about…

In their latest CrystEngComm Communication, Yadav and Gorbitz have endeavoured to restrict the modes of hydrogen bonding by substituting with TBD (see below). TBD has only 2 N-H donors which is much more manageable for these purposes! They partnered the TBD with dicarboxylic acid, 2,2′-bipyridine-5,5′ dicarboxylic acid (BPDA) to form a 2:1 complex. Additional acceptor sites at the carboxylate lone pairs means that 4 water molecules can co-crystallise along with the structure, leading to extended water channels or open organic networks containing clusters of water.

Read more now…

A supramolecular 2:1 guanidinium–carboxylate based building block for generation of water channels and clusters in organic materials
Vitthal N. Yadav and Carl Henrik Görbitz
CrystEngComm, 2013, DOI: 10.1039/C2CE26572A

The researchers identified and characterised three anhydrous co-crystal polymorphs, one co-crystal hydrate and one DMSO co-crystal solvate, and also highlighted a novel co-crystallisation technique at the interface between two immiscible solutions, yielding a pure phenazine:mesaconic acid co-crystal form.   Traditional solvent-based methods usually used for polymorphism screening were inappropriate for this system due to the large differences in solubility of phenazine and mesaconic acid.

Read more about this study for FREE at:

Screening for polymorphs of cocrystals: a case study
Mark D. Eddleston, Saranja Sivachelvam and William Jones
CrystEngComm, 2012, Advance Article
DOI: 10.1039/C2CE26496J

You may also be interested in other recent work on co-crystals by the Jones group:

Cocrystal dissociation and molecular demixing in the solid state
Mark D. Eddleston, Gareth O. Lloyd and William Jones
Chem. Commun., 2012, 48, 8075-8077
DOI: 10.1039/C2CC33412G, Communication

A hydrogen bonded cocrystal with an unusual interweaving between the adjacent triple-helices
Amit Delori and William Jones
CrystEngComm, 2011, 13, 6315-6318
DOI: 10.1039/C1CE05534H, Communication

Observation of a two-dimensional halogen-bonded cocrystal at sub-monolayer coverage using synchrotron X-ray diffraction
Stuart M. Clarke, Tomislav Frišcic, William Jones, Anasuya Mandal, Chenguang Sun and Julia E. Parker
Chem. Commun., 2011, 47, 2526-2528
DOI: 10.1039/C0CC04400H, Communication

Yu Huang, S. Roger Qiu and colleagues have used in situ atomic force microscopy to investigate how the growth of calcium oxalate monohydrate is inhibited by 6-residue linear aspartic acid peptides. 

Analysis of the step speed data showed that the aspartic acid enantiomers block active kink sites through step-pinning.

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Growth inhibition of calcium oxalate monohydrate crystal by linear aspartic acid enantiomers investigated by in situ atomic force microscopy
Kang R. Cho, E. Alan Salter, James J. De Yoreo, Andrzej Wierzbicki, Selim Elhadj, Yu Huang and S. Roger Qiu
CrystEngComm, 2013
DOI: 10.1039/C2CE25936B, Paper