James Bellows’s favorite structure is:

1-bromo-4-chloronaphthalene

Source: Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry 34(11) 3256 (1978)

Why?

Because it was determined by Raman spectroscopy.  We had 1,4-dichloro- and 1,4-dibromonaphthalene structures.  It has the 1,4-dichloronaphthalene structure with broadening, indicating that the bromines and chlorines are randomly arranged.—James Bellows

sudhir mittapalli’s favorite structure is:

NaCl crystal structure

NaCl

Source: Wikipedia

Why?

The first atomic-resolution structure to be "solved" (i.e., determined) in 1914 was that of table salt. After Von Laue's pioneering research, the crystallography field developed rapidly, most notably by physicists William Lawrence Bragg and his father William Henry Bragg. In 1912–1913, the younger Bragg developed Bragg's law, which connects the observed scattering with reflections from evenly spaced planes within the crystal.The Braggs, father and son, shared the 1915 Nobel Prize in Physics for their work in crystallography.—sudhir mittapalli

Kerry Fowler’s favorite structure is:

RIG-I

rigi

Source: PDB:3TMI Image generated with PyMol

Why?

Until my current job I had worked primarily in cancer drug discovery and knew virtually nothing about the innate immune system.  This amazing first-line defense to infection includes the RNA detector RIG-I which grabs onto the invader's double helix. —Kerry Fowler

Robert Dyer’s favorite structure is:

Tartaric Acid

Tartaric Acid

Source: Dalton Trans., 2014, 43, 95-102

Why?

Enatiopurity in both research and industry is extremely important due to the potential adverse effects of enantiomers. Promising drugs like Thalomid have been completely reevaluated based on the adverse effects of the drug’s enantiomer illustrating the importance of ensuring enatiopurity in the synthesis of compounds. Using crystallization, Louis Pasteur was the first scientist to separate the enantiomers of tartaric acid by physically sorting the different crystals into D and L tartaric acid. Louis Pasteur's work helped to identify that the different crystals originated from the molecular asymmetry of the molecule, helping to discover the basis of chemical chirality.—Robert Dyer

Fabienne Schwab’s favorite structure is:

Gold face-centered cubic

Gold face-centered cubic

Source: 1. Goswami, A. M.; Ghosh, S., Biological Synthesis of Colloidal Gold Nanoprisms Using Penicillium citrinum MTCC9999. Journal of Biomaterials and Nanobiotechnology 2013, 4, (2A), 20-27.

Why?

Nano-gold is an important model particle to study the – yet very poorly understood – uptake mechanisms of nanoparticles in plants. The unique, distinct and beautiful electron diffraction pattern of gold facilitates identification of the nanoparticles without doubt by means of a conventional electron microscope in the selected area electron diffraction mode. —Fabienne Schwab

Cora Lind-Kovacs’s favorite structure is:

ZrW2O8

ZrW2O8

Source: CrystalMaker

Why?

The determination of the crystal structure of ZrW2O8 in the 1990's revealed the origins of a fairly widespread mechanism of negative thermal expansion. The structure is composed of relatively rigid, corner-sharing
polyhedra, and transverse vibrations of the approximately linearly coordinated oxygen atoms result in the overall contraction of the structure.—Cora Lind-Kovacs

Don Bruce Sullenger’s favorite structure is:

beta-rhombohedral boron

beta-rhombohedral boron

Source: Source of photo: Monsanto Research Corp., Mound Laboratory, Miamisburg, OH. (A now closed and environmentally restored DOE laboratory).

Why?

Why this is my favorite X-ray crystal structure: The beautiful, strikingly unique structure of B-rhombohedral boron has successfully withstood numerous challenges of its correctness and has for a half century experienced nearly constant investigations of its structurally implied material characteristics. Arguably the most important of the several known phases of elemental boron, this form has been found to be experimentally stable from absolute zero to its melting point. Detailed consideration of the 5-foldness of its numerous discrete and merged 12-atom regular icosahedral motifs and their extended 84-atom truncated icosahedral arrays has forced a significant modification of chemical bonding theory in attempts to explain the low density, high strength, high melting, semiconducting and other notable properties of this low atomic number element. Even the observed partial occupancy of one of its 6-fold Wyckoff sets of atoms within the structure appears to be correct and to imply intriguing electronic possibilities. As one affected colleague has remarked: "You never fully recover from a bite of the boron bug." This structure illustrates some of the allure.—Don Bruce Sullenger

Venkat Reddy Chirasani’s favorite structure is:

Crystal structure of the hyperactive Type I antifreeze from winter flounder

AFP

Why?

Generally a polypeptide chain folds into a protein by hiding hydrophobic residues in its core by expelling water from its core. But this recently crystallized anti-freeze protein has retained ~400 water molecules in its core.  This dimeric, four-helix bundle protein has putative ice-binding residues. These residues point inwards and coordinate the interior waters into two intersecting polypentagonal networks. The inter helical contacts are minimal but the bundle is stabilized by anchoring the protein's backbone carbonyl groups to semi-clathrate water monolayers. The ordered waters likely involve in ice binding by extending outwards to the protein surface. Thus, this protein fold supports both the mechanisms of expelling water from the core of the protein for proper protein folding and the adsorption of antifreeze protein through anchored-clathrate water.—Venkat Reddy Chirasani

Maya’s favorite structure is:

collagen

320px-1K6F_Crystal_Structure_Of_The_Collagen_Triple_Helix_Model_Pro-_Pro-Gly103_04

Source: Nottingham blog

Why?

Its the most abundant structural protein in animals and have wide application in biomedicine. It also holds glyscosaminoglycans in the core. GAG is again another essential element for structural consistency having pharmaceutical
application.—Maya

Michael T Deans’s favorite structure is:

tetragonal water ice

Why?

Proton ordered tetragonal ice is a variant of cubic ice, sharing the strength of diamond and crystallizing in liquid nitrogen. It undergoes a first order ferroelectric transition, lazing at ~4 micron with quanta of the same energy as nucleotide phosphodiester bonds. Forming on the Earth's poles during an extreme primordial ice age and subject to fluctuating temperatures, this coherent infrared light was polarized by multiple reflection by surface ice and ice in clouds. Shining on equatorial pools of water, selectively photophosphorylated deoxyribonucleotides polymerised to form chiral DNA.

Ice It explains the origin of life, see full  account of 47 years' research at www.scienceuncoiled.co.uk. Its most significant consequences are: [1] Predicting the value of supplementing trace elements Se, Ag, Zn, F, Cu, I, Mn and In for disease prevention. [2] Explaining the biological energy coupling involved in muscle contraction, photosynthesis and oxidative phosphorylation. [3] Suggesting a chromosome structure functioning as the chip in the brain, biological clock and cold fusion reactor.

When confirmed, emulating ice It's properties promises better health, more human-friendly computers and clean ways to generate energy. The associated relativity between conception and perception offers simple accounts of particle physics, nuclear structure and cosmology. —Michael T Deans

Dr. Gerald E. Wuenschell’s favorite structure is:

PCNA

PCNA

Why?

PCNA is a molecule of elegant symmetry, with major functionalities distributed in 3-fold fashion around the central “hole” lined with positively charged residues (orange in the image) ideally suited for threading a DNA molecule, with its negative surface, through it when acting as one of its many functions – a sliding clamp.—Dr. Gerald E. Wuenschell

Robert D. Blackledge’s favorite structure is:

Bismuth

Bismuth

Source: Image by Micha L. Rieser

Why?

Looking at the photo it’s obvious that their beauty and geometric symmetry are the main reasons my favorite crystals are those formed by bismuth. However, other metals also form beautiful crystals with interesting symmetry. But bismuth may be obtained cheaply and is comparatively safe to work with and handle. A teach may divide a class into several groups and have each group grow bismuth crystals, but have each group grow their crystals with one condition (example, cooling rate) different from the other groups. The images of the crystals grown by each group could be viewed and their digital images captured by a smart phone. Then an app on the smart phone could measure the length and width of the top of each hopper-like crystal, calculate the area of each, and determine the mean area for the crystals by each group and the standard deviation in the mean area for the crystals of each group. Comparing the results of the various groups would lead to a class discussion of statistics and of the possible effects on crystal size of each of the varying conditions. These same experiments would be of great interest to hobbyists wanting to grow bismuth crystals for insertion into items of jewelry.—Robert D. Blackledge

Michael Tsapatsis’s favorite structure is:

zeolite MFI

MFI

Source:
http://izasc.ethz.ch/fmi/xsl/IZA-SC/ftc_main_image.xsl?-db=Atlas_main&-lay=fw&STC=MFI&-find

Why?

Zeolite MFI revolutionized the chemical process industry as a catalyst and adsorbent and continues to surprise with new and emerging applications and structural variations. It is also prototypical of a series of templated zeolites which continue to find new applications in catalysis and separations. At the time of its discovery, it was also one of the most complex inorganic structures. Moreover, it included an organic cation in the pores making it a prototype of self assembled nanostructure. —Michael Tsapatsis

Kuthuru Suresh’s favorite structure is:

Andrographolide-Salicylic acid pharmaceutical cocrystal

AP-SLA cocrystal

Source: Kuthuru Suresh, N. Rajesh Goud, and Ashwini Nangia., Chem. Asian J., 2013, 8, 3032 – 3041

Why?

Bitter pill: Andrographolide the bioactive agent used in traditional medicine in China, India, and South Asian countries. It is derived from the plant leaves of Andrographis paniculata . The local plant name in India is Kalmegh. A significant drop in the bioavailability of Andrographolide is due to transformation to its metabolite namely 14-deoxy-12-(R)-sulfo andrographolide isolated from humans and rats. The bioactive agent andrographolide was screened with pharmaceutically acceptable coformers to discover a novel solid form that will solve the chemical instability and poor solubility problems of this herbal medicine. Liquid-assisted grinding of andrographolide with GRAS (generally regarded as safe) coformers in a fixed stoichiometry resulted in cocrystals with vanillin(1:1), vanillic acid (1:1), salicylic acid (1:1), resorcinol (1:1), and guaiacol(1:1). All the crystalline products were characterized by thermal, spectroscopic, and diffraction methods. Interestingly, even though the cocrystals are isostructural, their physicochemical properties are quite different. The andrographolide–salicylic acid cocrystal completely inhibited the chemical transformation of andrographolide to its inactive sulfate metabolite, and the cocrystal exhibited a three times faster dissolution rate than pure andrographolide. This is a rare example of a pharmaceutical cocrystal that resists the chemical transformation that would otherwise make the drug inactive.—Kuthuru Suresh

Ethan Charles Blocher-Smith’s favorite structure is:

CsXeF7

CsXeF7

Source: http://openmopac.net/PM7_accuracy/data_solids/Cesium_xenon_heptafluoride__CsXeF7___ICSD_404986__jmol_XRay_fs.html

Why?

Not only does this compound include an alkali metal, a halogen, and a noble gas (traditionally unexpected), but it also violates the octet rule, adopting the rarely-seen monocapped octahedron for the XeF7- anion. In addition, in the absence of solvent at 50°C it readily decays into Cs2XeF8 (stable to 400°C) and the unstable XeF6. Even a hint of water and this will decay into the highly explosive XeO3.—Ethan Charles Blocher-Smith

Tim Munsie’s favorite structure is:

Fd3m/227/Pyrochlores

Fd3m:227:Pyrochlores

Source: Photo from our lab of a stained glass pyrochlore made by the parent of one of the undergraduate researchers

Why?

The reason my favourite group is the pyrochlores is because of the wide range of physics that comes out of the underlying symmetries, especially when it comes to magnetic frustration. It is easy to explain magnetism and symmetry to almost anyone with this structure. In addition, as group names go pyrochlore just sounds impressive, and personally a pyrochlore was the very first crystal I have grown from base powders into a single crystal.—Tim Munsie

S. Sudalai Kumar’s favorite structure is:

Clonixin (BIXGIY)

Clonixin (BIXGIY)

Source: S. Sudalai Kumar and A. Nangia, Cryst. Growth Des., 2014, 14 (4), 1865–1881

Why?

This is the first polymorphic system reported for neutral and zwitterionic polymorphism in the crystal structure data base. These zwitterionic polymorphs are rare in ampholytes and have pharmaceutical importance of high solubility and stability compared to neutral polymorphs. Several drugs are amphoteric in nature. This structural-cum-solubility study of neutral and zwitterionic polymorphs provides methods for their preparation and a comparison of solubility–stability characteristics. Normally solubility and stability are inversely related for drug polymorphs. We show that the twin characteristics of high solubility and good stability may be jointly optimized in the same zwitterionic polymorph for amphoteric drugs. The high polarity and ionic nature of acidic/ basic groups promote hydrogen bonding with water (for higher solubility) as well as a tighter crystal lattice of ionized molecules (polymorph stability). All the crystal structures were fully characterized by FT-IR, Raman and ss-NMR as well as powder X-ray diffraction line pattern. The thermodynamic relationships and phase transition between the neutral and zwitterionic polymorphs was analyzed by DSC and VT-PXRD. This study provides a new direction to crystallize ionic polymorphs of amphoteric drugs for solubility enhancement. The selective crystallization of zwitterionic forms could be possible through crystallization promoter additives.—S. Sudalai Kumar

William Dichtel’s favorite structure is:

NPN-1

NPN-1

Source: Nature Chemistry (cropped from original)

Why?

This crystal structure was the first covalent organic framework to be isolated as a single crystal suitable for x-ray diffraction, ushering in a future of designed polymeric solids. I hope to see many more in the future!

Ref: Wuest and coworkers, Nature Chemistry, 2013, 5, 830–834.—William Dichtel