CrystEngComm Blog

Halogen vs. hydrogen bonding

16 Jan 2013

This article is HOT as recommended by the referees. And we’ve made it free to access for 4 weeks.

Competing hydrogen-bond and halogen-bond donors in crystal engineering

In this HOT article by Aakeröy et al, relevant hydrogen-bond and halogen-bond acceptors and donors were selected to study the competition between these two molecular interactions in supramolecular assembly. Twelve co-crystals were synthesized based on two different azobipyridines as acceptors and six donor molecules possessing both hydrogen-bond and halogen-bond moieties. The key conclusions which could be drawn from the study were: (i) the hydrogen-bond is the principal driving force in the formation of 3,3′-azabipyridine co-crystals whereas hydrogen and halogen bonds do indeed compete in the formation of the 4,4′-azabipyridine co-crystals; (ii) the iodine donor appears to be a better halogen-bond donor than bromine; and (iii) the three different hydrogen-bond donors studied (–COOH, –OH and –CN(R)OH) behave similarly.

December Crystal Clear: A Crystal Snowflake

14 Jan 2013

By Matthew Cude, Development Editor.

SEM image of a dendritic copper(I) oxide crystal deposited on an ITO substrate in a stirred electrolyte

Last month’s crystal clear is a wintry image of a Cu₂O crystal.

The group from the Taiyuan University of Technology were investigating the growth of Cu₂O crystals along the <110> direction. Copper(I) oxide is a p-type semi-conductor with applications from solar-cells to water splitting and catalysis. The physical properties of Cu₂O crystals are greatly influenced by their morphology, which has generated considerable interested among crystal engineers.

The study by Wei Liang et al. reports the synthesis of dendritic crystals using a pulsed galvanostatic method and an electrolyte containing only Cu(Ac)₂, the controlled growth along the <110> directions produces these eye-catching nano-structures. The team reported the full details of their research in Issue 23 of CrystEngComm. You can download the full article below, which is free to access for 4 weeks.

Are you a budding crystal engineer? Keep up to date with latest developments by following us on twitter @CrystEngComm.

Crystallization behavior and formation mechanism of dendrite Cu₂O crystals
Jinbo Xue, Wei Liang, Xuguang Liu, Qianqian Shen and Bingshe Xu

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IUPAC Provisional Recommendations on Metal-Organic Framework and Coordination Polymer Terminology

08 Jan 2013

By Matthew Cude, Development Editor.

The IUPAC task group: Coordination polymers and metal organic frameworks: terminology and nomenclature guidelines have published provisional recommendations. The article can be accessed directly here and any comments can be directed to the task group chair, Professor Lars Öhrström.

The task group was set-up in 2009 to document, analyse and evaluate the use of nomenclature and terminology in the areas of coordination polymers and metal-organic frameworks. As well as meeting on three occasions the group also published a Highlight article detailing the need for terminology guidelines and the provisional recommendations, which include the following definitions:

Term	Definition
Coordination Polymer	A coordination compound continuously extending in 1, 2 or 3 dimensions through coordination bonds
Coordination Network	A coordination compound extending, through coordination bonds, in 1 dimension, but with cross-links between two or more individual chains, loops or spiro-links, or a coordination compound extending through coordination bonds in 2 or 3 dimensions
Metal-Organic Framework	Metal-Organic Framework, abbreviated to MOF, is a Coordination Polymer (or alternatively Coordination Network) with an open framework containing potential voids

There are also recommendations on net and network topology, topology descriptors, nomenclature and the use of other terms (which explicitly discourages the term “hybrid organic-inorganic materials”)

Download the full article for the complete recommendations and take a look at the Highlight article published last year

Coordination polymers, metal–organic frameworks and the need for terminology guidelines
Stuart R. Batten, Neil R. Champness, Xiao-Ming Chen, Javier Garcia-Martinez, Susumu Kitagawa, Lars Öhrström, Michael O’Keeffe, Myunghyun Paik Suh and Jan Reedijk
CrystEngComm, 2012, 14, 3001-3004
DOI: 10.1039/C2CE06488J

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Releasing the electronic potential in aluminium nitride

13 Dec 2012

By Jennifer Newton, Publishing Editor.

This article is HOT as recommended by the referees. And we’ve made it free to access for 4 weeks.

Photo of free-standing AlN wafer

The use of aluminium nitride in solid-state optoelectronic devices has been hindered by high defect levels limiting the output power, efficiency and lifetimes of mid-UV LEDs. Now, there is a possible solution, thanks to the method described in this HOT CrystEngComm paper.

R. Radhakrishnan Sumathi from Ludwig Maximilians University reports a physical vapour transport growth method using silicon carbide as a foreign substrate. The result is a more homogeneous structure than afforded by previous methods with uniform levels of defects and impurities across the wafer.

Read more now…

Bulk AlN single crystal growth on foreign substrate and preparation of free-standing native seeds
R. Radhakrishnan Sumathi
CrystEngComm, 2013
DOI: 10.1039/C2CE26599K

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Crystallising Plaster of Paris

07 Dec 2012

By Fiona McKenzie, Executive Editor.

It wasn’t so long ago when Plaster of Paris was used for plaster bandages when a patient broke their arm or leg. Nowadays, synthetic polymer materials tend to be used for such purposes but Plaster of Paris still finds wide use for building materials.

When Plaster of Paris (also known as bassanite or for those of us chemists not so familiar with this material, CaSO₄.1/2H₂O) is mixed with water, the less soluble compound, gypsum is formed (CaSO₄.2H₂O). This precipitates out of solution to produce interlocking, needle-like crystals. There have been many studies looking into this crystallisation reaction, however most real-life applications rely on crystallisation onto a solid support and as such, the studies to date are arguably not so industrially-relevant.

Now, in their latest CrystEngComm article, Stephen Mann and colleagues from the University of Bristol report on Plaster of Paris crystallisation onto inert films of cellulose. They found that the films can be made active by pre-treating them with a solution of Ca²⁺. Mann et al. say that such pre-treatment may have important implications for using Plaster of Paris materials in a wide range of industrial applications.

To read more about this work, download the article:
Calcium sulfate hemihydrate-mediated crystallization of gypsum on Ca²⁺-activated cellulose thin films
Stephen Mann, Mei Li, Tomi Nissinen and Nelly Brielles
CrystEngComm, 2013

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Guanidinium-based building blocks

29 Nov 2012

By Fiona McKenzie, Executive Editor.

This article is HOT as recommended by the referees. And we’ve made it free to access for 4 weeks.

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

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November Crystal Clear: Seeing Red

23 Nov 2012

By Matthew Cude, Development Editor.

Mid-infrared lasers are of particular interest for a variety of applications including sensing, defence applications and laser surgery tools such as the laser scalpel.

This month’s crystal clear is a very bright image of a CaErAlO₄ crystal.

The team from the Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, led by Professor Chaoyang Tu have been investigating new materials for mid-infrared lasers. Lasers in this range of the spectrum are of particular interest for a variety of applications including sensing, defence applications such as heat seeking missile counter measures and laser surgery tools such as the laser scalpel.

The crystal was successfully grown using the Czochralski method and the absorption and emission properties compared to those of existing InGaAs laser diodes and Er:YAG lasers. For more details on the team’s research findings, including the photochemical properties and crystal structure, you can read the full article which was published in Issue 21 of CrystEngComm.

Growth, structure and spectral properties of a novel crystal CaErAlO₄ for 2.7 μm lasers
Zhaojie Zhu, Huiyi Zeng, Jianfu Li, Zhenyu You, Yan Wang, Zixiang Huang and Chaoyang Tu
CrystEngComm, 2012, 14, 7423-7427
DOI: 10.1039/C2CE26013A

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Polymorphism co-crystal screening

15 Nov 2012

By Helen Lunn, Publishing Editor.

This article is HOT as recommended by the referees. And we’ve made it free to access for 4 weeks.

In their HOT article, Jones and co-workers at the University of Cambridge present a comprehensive crystal form screen for the phenazine:mesaconic acid system, employing a variety of different co-crystallisation methods.

: Phenazine:mesaconic acid system

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.

Role of aspartic acid in regulating the growth of common kidney stones

13 Nov 2012

By Jennifer Newton, Publishing Editor.

This article is HOT as recommended by the referees. And we’ve made it free to access for 4 weeks.

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.

Calcium oxalate monohydrate is the main inorganic component in the most common types of kidney stones, so preventing their formation is of great clinical importance.

October Crystal Clear: A Sparkling Crystal

31 Oct 2012

By Matthew Cude, Development Editor.

This month’s crystal clear is a barium borate crystal.

Inorganic borates are of interest due to their physical properties in the ultraviolet range of the electromagnetic spectrum, making them potentially useful materials in non-linear optics. The image is of a crystal created by T. B. Bekker et al from the Siberian Branch of Russian Academy of Sciences and published in Issue 20 of CrystEngComm.

The team were studying the BaB₂O₄–BaF₂–BaO system and discovered the new non-centrosymmetric solid-solution series Ba₇(BO₃)_4−xF_2+3x. For more information on the group’s discoveries you can download the full paper which is free to access for 4 weeks.

Phase formation in the BaB₂O₄–BaF₂–BaO system and new non-centrosymmetric solid-solution series Ba₇(BO₃)_4−xF_2+3xT. B. Bekker, S. V. Rashchenko, V. V. Bakakin, Yu. V. Seryotkin, P. P. Fedorov, A. E. Kokh and S. Yu. Stonoga
CrystEngComm, 2012, 14, 6910-6915
DOI: 10.1039/C2CE26122G

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CrystEngComm Blog

Halogen vs. hydrogen bonding

December Crystal Clear: A Crystal Snowflake

IUPAC Provisional Recommendations on Metal-Organic Framework and Coordination Polymer Terminology

Releasing the electronic potential in aluminium nitride

Crystallising Plaster of Paris

Guanidinium-based building blocks

November Crystal Clear: Seeing Red

Polymorphism co-crystal screening

Role of aspartic acid in regulating the growth of common kidney stones

October Crystal Clear: A Sparkling Crystal

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