Kristin M. Hutchins

Nanocrystals of a Metal–Organic Complex Exhibit Remarkably High Conductivity that Increases in a Single-Crystal-to-Single-Crystal Transformation

Ag(I) is used to form a π-stacked metal-organic solid that exhibits remarkably high electrical conductivity. The solid undergoes a single-crystal-to-single-crystal [2+2] photodimerization to generate a 1D coordination polymer with over 40% higher conductivity. The Ag(I) complex represents the first example of an increase in conductivity resulting from a [2+2] photodimerization. Density of states calculations show a higher contribution from Ag(I) ions to the valence band in the photodimerized solid, supporting the increase in conductivity.

Resorcinol-templated head-to-head photodimerization of a thiophene in the solid state and unusual edge-to-face stacking in a discrete hydrogen-bonded assembly.

A head-to-head photodimerization of a β-substituted thiophene stacked face-to-face in the solid state using a ditopic hydrogen-bond-donor template is reported. The face-to-face stacking is attributed to contributions of intertemplate forces, which contrasts an assembly wherein the same thiophenes stack edge-to-face yet maintain a discrete hydrogen-bonded structure.

From co-crystals to functional thin films: photolithography using [2+2] photodimerization

An approach to form organic thin films that employs multicomponent solids in the form of co-crystals has been developed. The components direct an intermolecular [2+2] photodimerization that we demonstrate exhibits a change in solubility that can be exploited as a negative photoresist for use in photolithography.

Thermal expansion properties of three isostructural co-crystals composed of isosteric components: interplay between halogen and hydrogen bonds

Co-crystallization of a symmetrical azo bipyridine with isosteric resorcinols affords isostructural co-crystals that exhibit linear thermal expansion along each axis. The thermal expansions involve interplay between intra-layer halogen and hydrogen bonds.

Mechanical Properties of a Series of Macro- and Nanodimensional Organic Cocrystals Correlate with Atomic Polarizability.

A correlation between Youngs modulus, as determined by using nanoindentation atomic force microscopy (AFM), and atomic polarizability is observed for members of a series of cocrystals based on systematic changes to one cocrystal component. Time domain spectroscopy over terahertz frequencies (THz-TDS) is used for the first time to directly measure the polarizability of macro- and nanosized organic solids. Cocrystals of both macro- and nanodimensions with highly polarizable atoms result in softer solids and correspondingly higher polarizabilities.

Unlocking pedal motion of the azo group: three- and unexpected eight-component hydrogen-bonded assemblies in co-crystals based on isosteric resorcinols

Abstract Co-crystallization of 3-phenylazopyridine (3PAzP) with dihalogenated resorcinols (res) 4,6-diX res (where: X = Cl, Br, and I) yields co-crystals that support molecular pedal motion in the crystalline state. The co-crystals are sustained by hydrogen-bonded assemblies, with the pattern of hydrogen-bonding drastically different based on the res. For 4,6-diCl res, an unexpected eight-component hydrogen-bonded assembly is realized, while three-component hydrogen-bonded assemblies are observed for 4,6-diBr res and 4,6-diI res. We show the co-crystallization approach to afford pedal motion in the azo core, while no such motion is present in the absence of a res. Pure 3PAzP packs to form a noncentrosymmetric herringbone structure.

Crystal engineering [2+2] photodimerizations via templates and hydrogen bonds: case of styrylthiophenes

Crystal engineering strategies have been used to modify solid-state packings to direct [2+2] photodimerizations of olefinic compounds that are photostable as pure solids. The strategies have herein been expanded to achieve rare [2+2] photodimerizations of styrylthiophenes. Two co-crystallization approaches based on hydrogen-bond-driven self-assembly are employed to achieve the photodimerizations that yield regioisomers of a β-substituted thiophene. We expect the co-crystal strategies can be applied to modify solid-state packing as well as achieve photodimerizations of olefins substituted with other unique organic functional groups.

Head-to-tail photodimerization of a thiophene in a co-crystal and a rare adipic acid dimer in the presence of a heterosynthon

A saturated dicarboxylic acid is employed to achieve a photoreactive hydrogen-bonded assembly based on a thiophene that reacts to generate a head-to-tail photoproduct. A co-crystal that exhibits both a homo- and heterosynthon in the same co-crystal based on adipic acid and the thiophene is also presented.

Remarkable decrease in stiffness of aspirin crystals upon reducing crystal size to nanoscale dimensions via sonochemistry

Nano-dimensional single crystals of acetylsalicylic acid (aspirin) Form I are generated through sonocrystallization and are shown to exhibit Youngs modulus values in the MPa range, which is significantly softer (5-fold reduction) than macro-dimensional single crystals. The change is attributed to structural consequences of the size-dependent surface-to-volume ratio effect, particularly as related to intermolecular forces.