CrystEngComm Blog

By looking at the structures of halogen-bonded infinite chains with two diiodoperfluoroalkanes and a bent bis(pyrid-4′-yl)oxadiazole, Giuseppe Resnati and colleagues have investigated the influence that halogen bond directionality has on supramolecular design.  The bent geometry of the pyridyl pendant rings in the structures were found to translate into the angle between the formed halogen bonds, taking precedence over parameters that might affect the crystal packing.

Download their HOT CrystEngComm communication today to find out more…

Halogen bond directionality translates tecton geometry into self-assembled architecture geometry
Marco Saccone, Gabriella Cavallo, Pierangelo Metrangolo, Andrea Pace, Ivana Pibiri, Tullio Pilati, Giuseppe Resnati and Giancarlo Terraneo
CrystEngComm, 2013
DOI: 10.1039/C3CE40268A, Communication

This communication is part of a themed issue on Halogen bonding (guest edited by Giuseppe Resnati, Mark Taylor and William Pennington) which is due to go online next week.

Noriaki Kubota and colleagues have modelled the effects of sensitivity and resolution of a nucleation detector on metastable zone width. 

The metastable zone width has been somewhat ambiguously defined as “the supercooling at which the first crystals or uncontrolled spontaneous crystallisation is detected when the solution temperature is lowered at a constant rate”. In order to pin down the specifics, a couple of groups have defined the metastable zone width as the supercooling that occurs when the number density of crystals reaches a fixed value – which in effect is determined by the sensitivity of the detection method.

To find out what effect the sensitivity and resolution of a detector has on metastable zone width readings, the team have employed analytical and numerical methods. A deeper understanding of this is neccesary to enable better control of crystallisation processes.

Download the article today to find out more…

Analytical and numerical study of detector sensitivity and resolution effects on metastable zone width
Noriaki Kubota, Masanori Kobari and Izumi Hirasawa
CrystEngComm, 2013, 15, 2091-2098
DOI: 10.1039/C2CE26968F, Paper

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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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

Robert LaDuca, and colleagues at Michigan State University, have hydrothermally synthesised divalent metal coordination polymers featuring the ligand, 3-pyridylisonicotinamide (3-pina).  The 3-pina ligand has a hydrogen bonding donor and acceptor locus at its central amide, making supramolecular structure direction achievable, something that is not possible using the regularly tested ligand, 4,4′-bipyridine.

The 3-pyridylisonicotinamide ligand has a kinked disposition of its nitrogen atoms.

The team discuss 3 very diverse structures featuring the 3-pina ligand, showing that the dimensionality in the resulting coordination polymers very much depends on the metal coordination environment and the sulfate binding mode that occurs in each case.

Download the paper now to find out more:

Metal dependent dimensionality in sulfate coordination polymers containing 3-pyridylisonicotinamide
Jacqueline S. Lucas, Jacob W. Uebler and Robert L. LaDuca
CrystEngComm, 2012
DOI: 10.1039/C2CE26333E, Paper

Take a look at some of the teams other recent CrystEngComm articles:

Topological diversity in zinc coordination polymers with 5-substituted isophthalate and bis(4-pyridylmethyl)piperazine ligands
Amy L. Pochodylo and Robert L. LaDuca
CrystEngComm, 2011,13, 2249-2261
DOI: 10.1039/C0CE00715C, Paper

Metal and ligand binding mode dependent topologies in phthalate coordination polymers with bis(4-pyridylformyl)piperazine co-ligands
Curtis Y. Wang, Zachary M. Wilseck, Ronald M. Supkowski and Robert L. LaDuca
CrystEngComm, 2011,13, 1391-1399
DOI: 10.1039/C0CE00632G, Paper

Cadmium bis(4-pyridylformyl)piperazine coordination polymers: layered nets and a novel 3,5-connected binodal lattice
Jacqueline S. Lucas, Amy L. Pochodylo and Robert L. LaDuca
CrystEngComm, 2010,12, 3310-3317
DOI: 10.1039/C0CE00117A, Paper

Drugs, as with many molecular compounds, often exist in different crystal forms, and in these different forms they will exhibit different chemical and physical properties.  Different solubilities and dissolution rates result in different absorption rates so the ability to control what form crystals take on, is of key importance throughout many stages of the pharmaceutical industry.

This HOT paper from Braga, Grepioni et al. looks at the crystal structures of four crystal forms of the synthetic antibiotic rifaximin.  The study increases our understanding of how water molecules interact with rifaximin and/or amongst themselves in the crystal packing as well as providing information on the phase relationship of the hydration-dehydration process.

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The structure–property relationship of four crystal forms of rifaximin
Dario Braga, Fabrizia Grepioni, Laura Chelazzi, Manuela Campana, Donatella Confortini and Giuseppe C. Viscomi
CrystEngComm, 2012
DOI: 10.1039/C2CE25920F, Paper

You might also find our recent themed issue on Crystal engineering and crystallography in the pharmaceutical industry interesting.

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Nacre, a material found on the outer-coating of pearls, has incredible mechanical strength thanks to its arrangement of parallel laminars of inorganic layers separated by organic layers of macromolecules.

Scientists at Zhejiang University, China, have combined calcium phosphate and sodium bis(2-ethylhexyl)sulfosuccinate in the presence of bovine serum albumin to create hybrid crystals with a nacre-like structure. 

The hybrid crystals grew by a classical screw growth mechanism which is similar to the actual biological pathway for nacre formation. Further development of such biomimetic pathways will progress research into new, and perhaps stronger, organic-inorganic composites.

Download the manuscript which will be free to access for 4 weeks.

Lamellar organic–inorganic architecture via classical screw growth
Yan Quan, Halei Zhai, Zhisen Zhang, Xurong Xu and Ruikang Tang
CrystEngComm, 2012
DOI: 10.1039/C2CE25805F, Paper

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