Solid-state Dynamics Research Articles

Self-correcting mismatches in metastable hydrogen-bonded organic frameworks with an 11-fold interpenetrated array.

The polymorphic self-correction from a metastable phase to a stable one often occurs and plays crucial roles in synthesizing robust hydrogen-bonded organic frameworks (HOFs). However, identifying metastable phases and understanding the self-correcting mechanisms is a challenging venture due to their intrinsic instability. Here, we for the first time introduce 1,8-naphtholactam (Np) as a hydrogen-bonding synthon positioned on the periphery of a bicarbazole to create a versatile molecular unit for 3D HOFs. The as-synthesized NCU-HOF1, analyzed by single-crystal X-ray diffraction (SCXRD), is found to be metastable. It exhibits an 11-fold interpenetrated dia topology with a quarter of the Np units exhibiting monomeric N-H⋯O interactions between adjacent Np link sites, which readily self-correct upon desolvation to form fully dimeric ones. Consequently, the resultant NCU-HOF1a becomes highly robust in polar solvents, strong acid or alkaline aqueous solutions, and has permanent porosity with contracted cavities for selective adsorption and efficient "turn-up" fluorescent sensing of C2H4 gas. This work not only debuts a new hydrogen-bonding synthon but offers more insights into investigating solid-state dynamics in metastable HOFs.

The importance of being weak: how weak interactions trigger solid-state dynamics

The importance of being weak: how weak interactions trigger solid-state dynamics

Inhalable ceftazidime-roflumilast powder targeting infection and inflammation: Influence of incorporating roflumilast into ceftazidime-leucine co-amorphous formulation

Co-amorphization of a single drug with amino acid is a technique to improve aerosolization of inhalable spray-dried formulation for inhalation therapy. However, the incorporation of a second drug molecule into drug-amino acid co-amorphous particles to prepare combination formulations has not been explored. Here, we prepared combination powders using two model drugs, ceftazidime and roflumilast, which when concurrently used can potentially improve therapeutic outcome in non-cystic fibrosis bronchiectasis by counteracting both infection and inflammation. The study was performed using a two-step approach. The first step involved the identification of an amino acid and its concentration (% w/w) for the best aerosolization enhancement of ceftazidime by varying the ratios of leucine and tryptophan in combination (0–25 % w/w). In the second step, roflumilast (5–20 % w/w) was incorporated into the formulation containing the selected concentration of the amino acid to understand the impact of introducing a second drug into ceftazidime-amino acid(s) co-amorphous particles. In total, 10 formulations were prepared and characterized in terms of solid-state and aerosol performance. Leucine introduced surface asperity which correlated well with improved aerosolization of the particles. The best fine particle fraction (FPF) (75 %) was achieved with 25 % leucine; hence, leucine was selected as the ideal amino acid at the given concentration to understand the impact of roflumilast inclusion on ceftazidime-leucine system. The ceftazidime-roflumilast powder retained their anti-bacterial and anti-inflammatory properties following formulation. However, inclusion of roflumilast at 5 % dramatically decreased the FPF to 55 % and higher roflumilast concentration did not have much effect on FPF. The decrease in FPF ascribed to the change in particle surface as roflumilast was found to decrease surface asperity. In addition, leucine crystallized with inclusion of roflumilast. This study indicates that inclusion of a second drug into drug-amino acid amorphous matrix particles can affect its solid-state dynamics and aerosol performance; hence, such parameters should be cautiously considered while undertaking similar endeavors of preparing combination formulations.

A Spectroscopic Investigation into the Photophysics of Donor-Acceptor Emitters Intended for Use in Thermally Activated Delayed Fluorescence Based Optoelectronic Systems: A Comparison of Excited State Dynamics in Solution and Solid-State

A Spectroscopic Investigation into the Photophysics of Donor-Acceptor Emitters Intended for Use in Thermally Activated Delayed Fluorescence Based Optoelectronic Systems: A Comparison of Excited State Dynamics in Solution and Solid-State

Synthesis and Solid-State Dynamics of a Crystalline Steroid Molecular Rotor without the Alkyne Axle: Steroid Dimers Based on a 1,4-Di(1,3-dioxan-2-yl)benzene Moiety.

Two diastereomeric crystalline steroid dimers were obtained by acid-catalyzed double acetalization of (20S)-5α-pregnan-3β,16β,20-triol 3-monoacetate with terephtalaldehyde. These compounds were characterized by NMR in solution, MS, single-crystal X-ray diffraction, and variable-temperature solid-state NMR by 13C cross-polarization magic angle spinning (CPMAS). While the phenylene rotator in the SR diastereomer remains static even at 373 K, the RR isomer shows a slow rotational process of the phenylene ring at temperatures above room temperature and thus may be considered the first crystalline steroid molecular rotor without the alkyne axle.

Solid-State Dynamics and High-Pressure Studies of a Supramolecular Spiral Gear.

The structures and solid-state dynamics of the supramolecular salts of the general formula [(12-crown-4)2 ⋅DABCOH2 ](X)2 (where DABCO=1,4-diazabicyclo[2.2.2]octane, X=BF4 , ClO4 ) have been investigated as a function of temperature (from 100 to 360 K) and pressure (up to 3.4 GPa), through the combination of variable-temperature and variable-pressure XRD techniques and variable-temperature solid-state NMR spectroscopy. The two salts are isomorphous and crystallize in the enantiomeric space groups P32 21 and P31 21 . All building blocks composing the supramolecular complex display dynamic processes at ambient temperature and pressure. It has been demonstrated that the motion of the crown ethers is maintained on lowering the temperature (down to 100 K) or on increasing the pressure (up to 1.5 GPa) thanks to the correlation between neighboring molecules, which mesh and rotate in a concerted manner similar to spiral gears. Above 1.55 GPa, a collapse-type transition to a lower-symmetry ordered structure, not attainable at a temperature of 100 K, takes place, proving, thus, that the pressure acts as the means to couple and decouple the gears. The relationship between temperature and pressure effects on molecular motion in the solid state has also been discussed.

Efficient table-top beamline for attosecond molecular and solid-state dynamics at the carbon K-edge

SynopsisA harmonic continuum extending up to 375 eV is generated from 750 μJ, 9 fs mid-IR pulses centered at 1300 nm. The development of this source and its use for attosecond transient absorption spectroscopy experiments at the carbon K-edge are discussed.

Towards jitter-free ultrafast electron diffraction technology

Stroboscopic visualization of nuclear or electron dynamics in atoms, molecules or solids requires ultrafast pump and probe pulses and a close to perfect synchronization between the two. We have developed a 3 MeV ultrafast electron diffraction (UED) probe technology that nominally reduces the electron bunch duration and the arrival time jitter to the subfemtosecond level. This simple configuration uses a radiofrequency photogun and a 90° achromatic bend and is designed to provide effectively jitter-free conditions. Terahertz streaking measurements reveal an electron bunch duration of 25 fs, even for a charge as high as 0.6 pC, and an arrival time jitter of 7.8 fs, the latter limited by only the measurement accuracy. From pump–probe measurements of photoexcited bismuth films, the instrument response function was determined to be 31 fs. This pioneering jitter-free technique paves the way towards UED of attosecond phenomena in atomic, molecular and solid-state dynamics. An ultrafast electron diffraction facility with an overall temporal resolution of 31 fs root mean square is developed. Even for a charge as high as 0.6 pC, the electron bunch duration and timing jitter are 25 fs and less than 10 fs, respectively.

Characterization of H/D exchange in type 1 pili by proton-detected solid-state NMR and molecular dynamics simulations

Uropathogenic Escherichia coli invades and colonizes hosts by attaching to cells using adhesive pili on the bacterial surface. Although many biophysical techniques have been used to study the structure and mechanical properties of pili, many important details are still unknown. Here we use proton-detected solid-state NMR experiments to investigate solvent accessibility and structural dynamics. Deuterium back-exchange at labile sites of the perdeuterated, fully proton back-exchanged pili was conducted to investigate hydrogen/deuterium (H/D) exchange patterns of backbone amide protons in pre-assembled pili. We found distinct H/D exchange patterns in lateral and axial intermolecular interfaces in pili. Amide protons protected from H/D exchange in pili are mainly located in the core region of the monomeric subunit and in the lateral intermolecular interface, whereas the axial intermolecular interface and the exterior region of pili are highly exposed to H/D exchange. Additionally, we performed molecular dynamics simulations of the type 1 pilus rod and estimated the probability of H/D exchange based on hydrogen bond dynamics. The comparison of the experimental observables and simulation data provides insights into stability and mechanical properties of pili.

Investigation of structure and dynamics in a photochromic molecular crystal by NMR crystallography.

A photochromic anil, N-(3,5-di-t-butylsalicylidene)-4-amino-pyridine, has been studied by single-crystal X-ray diffraction, multinuclear magic-angle spinning NMR, and first-principles density functional theory (DFT) calculations. Interpretation of the solid-state NMR data on the basis of calculated chemical shifts confirms the structure is primarily composed of molecules in the ground-state enol tautomer, whereas thermally activated cis-keto and photoisomerised trans-keto states exist as low-level defects with populations that are too low to detect experimentally. Variable temperature 13 C NMR data reveal evidence for solid-state dynamics, which is found to be associated with fast rotational motion of t-butyl groups and 180° flips of the pyridine ring, contrasting the time-averaged structure obtained by X-ray diffraction. Comparison of calculated chemical shifts for the full crystal structure and an isolated molecule also reveals evidence for an intermolecular hydrogen bond involving the pyridine ring and an adjacent imine carbon, which facilitates the flipping motion. The DFT calculations also reveal that the molecular conformation in the crystal structure is very close to the energetic minimum for an isolated molecule, indicating that the ring dynamics arise as a result of considerable steric freedom of the pyridine ring and which also allows the molecule to adopt a favourable conformation for photochromism.

Nanoscale Organization and Solid-State Dynamics of Carbazole-[π]-Carbazole Rotors Edged with Aliphatic Chains

The aggregation behavior and its influence on the intramolecular motion of three highly conjugated solid-state molecular rotors 2–4 with alkyl groups were investigated by a combination of fluoresce...

Ultrafast demagnetization in iron: Separating effects by their nonlinearity.

The laser-driven ultrafast demagnetization effect is one of the long-standing problems in solid-state physics. The time scale is given not only by the transfer of energy, but also by the transport of angular momentum away from the spin system. Through a double-pulse experiment resembling two-dimensional spectroscopy, we separate the different pathways by their nonlinear properties. We find (a) that the loss of magnetization within 400 fs is not affected by the previous excitations (linear process), and (b) we observe a picosecond demagnetization contribution that is strongly affected by the previous excitations. Our experimental approach is useful not only for studying femtosecond spin dynamics, but can also be adapted to other problems in solid-state dynamics.

Ferroelectricity and Ferroelasticity in Organic Inorganic Hybrid (Pyrrolidinium)3[Sb2Cl9

Perovskite-like materials exhibit desirable photophysical and electric properties that make them suitable for a remarkable breadth of applications in electronics and physics. In this contribution, we report on the multiphase ferroelectric and ferroelastic phenomena in a pyrrolidinium-based hybrid metal–organic material: (C4H8NH2)3[Sb2Cl9]. The title compound is the first pyrrolidinium derivative within the halobismuthates(III) and haloantimonates(III) families that is featured by the ferroelectric property. From a structural point of view, the crystal structure is built of [Sb2Cl9]3–∞ perovskite-like layers, interdigitated by layers of pyrrolidinium cations. The rich solid-state dynamics of pyrrolidinium cations endowed (C4H8NH2)3[Sb2Cl9] with a complex sequence of temperature-dependent phase transitions. Remarkably, polar properties have been found to occur in all six phases, including room-temperature Phase I. Insights from variable-temperature single-crystal X-ray diffraction, dielectric spectroscopy, ...

Ratchet-free solid-state inertial rotation of a guest ball in a tight tubular host

Dynamics of molecules in the solid state holds promise for connecting molecular behaviors with properties of bulk materials. Solid-state dynamics of [60]fullerene (C60) is controlled by intimate intermolecular contacts and results in restricted motions of a ratchet phase at low temperatures. Manipulation of the solid-state dynamics of fullerene molecules is thus an interesting yet challenging problem. Here we show that a tubular host for C60 liberates the solid-state dynamics of the guest from the motional restrictions. Although the intermolecular contacts between the host and C60 were present to enable a tight association with a large energy gain of –14 kcal mol–1, the dynamic rotations of C60 were simultaneously enabled by a small energy barrier of +2 kcal mol–1 for the reorientation. The solid-state rotational motions reached a non-Brownian, inertial regime with an extremely rapid rotational frequency of 213 GHz at 335 K.

Rational integrals of quasi-homogeneous dynamical systems

Dynamical systems, described by quasi-homogeneous systems of differential equations with polynomial right-hand sides, are considered. The Euler–Poisson equations from solid-state dynamics, as well as the Euler–Poincaré equations in Lie algebras, which describe the dynamics of systems in Lie groups with a left-invariant kinetic energy, can be pointed out as examples. The conditions for the existence of rational first integrals of quasi-homogeneous systems are found. They include the conditions for the existence of invariant algebraic manifolds. Examples of systems with rational integrals which do not admit of first integrals that are polynomial with respect to the momenta are presented. Results of a general nature are also demonstrated in the example of a Hess–Appel’rot invariant manifold from the dynamics of an asymmetric heavy top.

Synthesis, Rotational Dynamics, and Photophysical Characterization of a Crystalline Linearly Conjugated Phenyleneethynylene Molecular Dirotor

We report the synthesis, crystal structure, solid-state dynamics, and photophysical properties of 6,13-bis((4-(3-(3-methoxyphenyl)-3,3-diphenylprop-1-yn-1-yl)phenyl)ethynyl)-5,7,12,14-tetrahydro-5,14:7,12-bis([1,2]benzeno)pentacene (1), a molecular dirotor with a 1,4-bis((4-ethynylphenyl)ethynyl)benzene (BEPEB) chromophore. The incorporation of a pentiptycene into the molecular dirotor provides a central stator and a fixed phenylene ring relative to which the two flanking ethynylphenylene rotators can explore various torsion angles; this allows the BEPEB fluorophore dynamics to persist in the solid state. X-ray diffraction studies have shown that molecular dirotor 1 is packed so that all the BEPEB fluorophores adopt a parallel alignment, this is ideal for the development of functional materials. Variable temperature, quadrupolar echo (2)H NMR studies have shown that phenylene rotator flipping has an activation energy of 9.0 kcal/mol and a room temperature flipping frequency of ∼2.6 MHz. Lastly, with measurements in solution, glasses, and crystals, we obtained evidence that the fluorescence excitation and emission spectra of the phenyleneethynylene chromophores is dependent on the extent of conjugation between the phenylene rings, as determined by their relative dihedral angles. This work provides a promising starting point for the development of molecular dirotors with polar groups whose amphidynamic nature will allow for the rapid shifting of solid-state absorption, fluorescence, and birefringence, in response to external electric fields.

Experiments in ICF, materials science, and astrophysics

We have been developing HED experiments on high power ICF lasers over the past two decades that span (1) the radiative hydrodynamics of ICF capsule physics; (2) the high pressure, high strain rate, solid-state dynamics relevant to novel concepts for ICF and hypervelocity impacts in space and on Earth; and (3) the shock driven turbulence of exploding stars (supernovae). These different regimes are separated by many orders of magnitude in length, time, and temperature, yet there are common threads that run through all of these phenomena, such as the occurrence of hydrodynamic instabilities. Examples from each of these three seemingly very disparate regimes are given, and the common theme of hydrodynamic instability evolution is explored.

Effect of pH and Excipients on Structure, Dynamics, and Long-Term Stability of a Model IgG1 Monoclonal Antibody upon Freeze-Drying

To investigate the mechanism of IgG1 mAb stabilization after freeze-drying and the interdependence of protein structural preservation in the solid state, glassy state dynamics and long-term storage stability under different formulation conditions. IgG1 mAb was formulated with mannitol at pH 3.0, 5.0, and 7.0 in the presence and absence of sucrose and stability was monitored over 1year at different temperatures. Physical and covalent degradation of lyophilized formulation was monitored using SEC, CEX, and light obscuration technique. Secondary and tertiary structure of the protein in the solid state was characterized using FTIR and fluorescence spectroscopy respectively. Raman spectroscopy was also used to monitor changes in secondary and tertiary structure, while SS-NMR (1)H relaxation was used to monitor glassy state dynamics. IgG1 mAb underwent significant secondary structural perturbations at pH 3.0 and conditions without sucrose, while pH 5.0 condition with sucrose showed the least structural change over time. The structural changes correlated with long-term stability with respect to protein aggregate formation and SbVP counts. SS-NMR data showed reduced relaxation time at conditions that were more stable. Native state protein structural preservation and optimal solid-state dynamics correlate with improved long-term stability of the mAb in the different lyophilized formulations.

Macrocyclic Molecular Rotors with Bridged Steroidal Frameworks

In this work, we describe the synthesis and solid-state dynamics of isomeric molecular rotors 7E and 7Z, consisting of two androstane steroidal frameworks linked by the D rings by triple bonds at their C17 positions to a 1,4-phenylene rotator. They are also linked by the A rings by an alkenyl diester bridge to restrict the conformational flexibility of the molecules and reduce the number of potential crystalline arrays. The analysis of the resulting molecular structures and packing motifs offered insights of the internal dynamics that were later elucidated by means of line shape analyses of the spectral features obtained through variable-temperature solid-state (13)C NMR; such analysis revealed rotations in the solid state occurring at kilohertz frequency at room temperature.

Cover Picture: Solution and Solid-State Dynamics of Metal-Coordinated White Phosphorus (Chem. Eur. J. 36/2012)

Cover Picture: Solution and Solid-State Dynamics of Metal-Coordinated White Phosphorus (Chem. Eur. J. 36/2012)