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IRMOF-10, derived from biphenyl-4,4′-dicarboxylic acid and zinc, is a prototype for an open cubic structure prone to interpenetration. Interpenetration can compromise MOF pore volume and surface area which drives the need to develop strategies to synthesize non-interpenetrated MOFs. In this work, an additive design strategy was employed to suppress interpenetration of IRMOF-10. The presence of the additive during traditional solvothermal synthesis yielded an activated material with the highest surface area reported to date and enabled the determination of the single crystal structure. In situ monitoring of the nucleation of crystals under polarized light provided insights into the mechanism behind interpenetration in the IRMOF-9/10 system. This work provides a roadmap to suppress interpenetration more generically in other MOFs and achieve improved surface areas and pore volumes for this prominent class of porous sorbents. [ABSTRACT FROM AUTHOR]

Materials that lack inversion symmetry (noncentrosymmetric) demonstrate a diversity of desirable optical and electronic properties in bulk such as second harmonic generation, chiral emission, and piezo-, pyro-, and ferro-electricity. Unfortunately, it is challenging to reliably access noncentrosymmetric packing motifs because the closest packing of molecules is often achieved through inversion symmetry operators, leading to the relatively low occurrence of noncentrosymmetry in organic crystals. In this study, the occurrence of noncentrosymmetry in materials that adopt planar packing motifs is investigated because molecular species achieve closest packing in two dimensions through rotations and (or) glides, symmetry operators that do not individually lead to centrosymmetry. It is found that of the 18 crystal structures investigated here adopting planar packing motifs, 13 structures (72%) are noncentrosymmetric showing in-plane polarization. The 13 noncentrosymmetric crystal structures differ from the centrosymmetric structures by directional halogen bonding interactions or steric collisions that align the polarization directions of neighboring layers, leading to bulk structural polarity. The results from this investigation will be of use for designing noncentrosymmetric materials for application in optical and electronic devices. Key words: noncentrosymmetry, cocrystal, plane group symmetry, charge transfer. Les structures depourvues de symetrie d'inversion (non centrosymetriques) presentent une diversite de proprietes optiques et electroniques desirables a l'echelle du materiau, notamment la generation de seconde harmonique, des proprietes d'emission chirale ainsi que des proprietes piezo-, pyro- et ferro-electriques. Il est malheureusement difficile d'acceder de maniere fiable a des motifs d'empilement non centrosymetriques, car l'empilement le plus compact de molecules s'obtient souvent par des operations de symetrie d'inversion, ce qui explique que la non-centrosymetrie s'observe dans un nombre relativement faible de cristaux organiques. Dans la presente etude, nous avons etudie la presence de non-centrosymetrie dans des materiaux qui adoptent des configurations d'empilement planaires, car les especes moleculaires s'organisent de la maniere la plus compacte en deux dimensions par des operations de symetrie de rotation et de translation qui ne permettent pas individuellement de donner lieu a la centrosymetrie. Nous avons observe que, parmi les 18 structures cristallines que nous avons etudiees qui adoptent des configurations d'empilement planaires, 13 (72 %) sont non centrosymetriques et presentent une polarisation dans le plan. Ces 13 structures cristallines non centrosymetriques se distinguent des structures centrosymetriques par le caractere directionnel de leurs liaisons halogene ou par les collisions steriques qui alignent les directions de polarisation des couches voisines, ce qui donne lieu a une polarite structurale de l'ensemble. Les resultats de cette recherche pourront servir a la conception de materiaux non centrosymetriques destines a des applications dans des dispositifs optiques et electroniques. [Traduit par la Redaction] Mots-cles: non-centrosymetrie, cocristal, groupe de symetrie planaire, transfert de charge., Introduction Crystallographic noncentrosymmetry is a key property of solid-state materials in numerous optical and electronic applications such as second harmonic generation and piezo-, pyro-, and ferroelectricity. (1-6) Although most current [...]

Cocrystallization assembles multicomponent crystals in defined ratios that are held together by intermolecular interactions. While cocrystals have seen extensive use in the pharmaceutical industry for solving issues with stability and solubility, extension to the field of energetic materials for improved properties has proven difficult. Predicting successful coformers remains a challenge for systems lacking well‐understood synthons that promote reliable intermolecular assembly. Herein, an alternative method is investigated for altering energetic properties that operates in the absence of well‐defined interactions by molecular doping. An impact sensitive primary explosive, cyanuric triazide (CTA), was selected as the dopant to test if less impact sensitive secondary explosives could gain increased sensitization to impact when CTA is inserted into their crystal lattices. Molecular doping was successful in sensitizing three melt‐castable energetics: 2,4,6‐trinitrotoluene (TNT), 2,4‐dinitroanisole (DNAN), and 1,3,3‐trinitroazetidine (TNAZ). CTA could also be incorporated as a stabilized inclusion to sensitize DNAN further. These results demonstrate how the judicious choice of dopant can lead to specific property improvements, providing a method for creating energetic materials with new properties to access metal‐free primary explosives and physical hot spot models for explosive ignition. [ABSTRACT FROM AUTHOR]

Artificial phantoms used in photothermal near-infrared laser lithotripsy research generally fail to mimic both the chemical and the physical properties of human stones. Though high-energy, 1 J pulses are capable of fracturing hard human stones into several large fragments along natural boundaries, similar behavior has not been observed in commonly used gypsum plasters like BegoStone. We developed a new brushite-based plaster formulation composed of ≈90% brushite that undergoes rapid fracture in the manner of human stones under fragmentation pulse regimes. Single-pulse (1 J) ablation crater volumes for phantoms were not significantly different from those of pure brushite stones. Control over crater volumes was demonstrated by varying phosphorous acid concentration in the plaster formulation. Fragmentation of cylindrical brushite phantoms was filmed using a high-speed camera which demonstrated rapid fragmentation in < 100 µs during the bubble expansion phase of a short pulse from a high-powered Ho:YAG laser (Lumenis Pulse 120 H). The rapid nature of observed fracture suggests increasing laser pulse energy by increasing laser pulse duration will not improve fragmentation performance of laser lithotripters. Brushite plaster phantoms are a superior alternative to gypsum plasters for laser lithotripsy research due to their better mimicry of stone composition, controllable single-pulse crater volumes, and fragmentation behavior. [ABSTRACT FROM AUTHOR]

In contrast to the mature predictive frameworks applied to neutral cocrystals, ionic cocrystals, those including an ion pair, are difficult to design. Furthermore, they are generally excluded categorically from studies which correlate specific molecular properties to cocrystal formation, leaving the prospective ionic cocrystal engineer with few clear avenues to success. Herein ammonium nitrate, an energetic oxidizing salt, is targeted for cocrystallization in a potential coformer group selected based on likely interactions with the nitrate ion as revealed in the Cambridge Structural Database; six novel ionic cocrystals were discovered. Molecular descriptors previously identified as being related to neutral cocrystal formation were examined across the screening group but showed no relationship with ionic cocrystal formation. High packing coefficient is shown to be a constant among the successful coformers in the set and is utilized to directly target two more successful coformers, bypassing the need for a large screening group. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) are demonstrated to be readily activated by treatment with the low surface tension, low boiling point solvent dimethyl ether (DME). The mildness of the method enables access to high surface areas by avoiding structural changes in the framework that often plague thermal activation methods. A distinction from previous methods is that DME activation succeeds for materials with coordinatively unsaturated sites (CUS) and non‐CUS MOFs as well. DME displaces solvent molecules occupying the pores of the MOF as well as those coordinated to metal centers; reducing evacuation temperature by using a coordinating, yet highly volatile guest enables low temperature activation with structural retention as demonstrated surface area measurements that match or exceed existing activation protocols. [ABSTRACT FROM AUTHOR]

Introduction: Laser lithotripsy can cause excessive heating of fluid within the collecting system and lead to tissue damage. To better understand this effect, it is important to determine the percentage of applied laser energy that is converted to heat and the percentage used for stone ablation. Our objective was to calculate the percentage of laser energy used for stone ablation based on the difference in fluid temperature measured in an in vitro model when the laser was activated without and with stone ablation. Methods: Flat BegoStone disks (15:5) were submerged in 10 mL of deionized water at the bottom of a vacuum evacuated double-walled glass Dewar. A Moses 200 D/F/L laser fiber was positioned above the surface of the stone at a distance of 3.5 mm for control (no stone ablation) or 0.5 mm for experimental (ablation) trials. The laser was activated and scanned at 3 mm/second across the stone in a preprogrammed pattern for 30 seconds at 2.5 W (0.5 J × 5 Hz) for both short-pulse (SP) and Moses distance (MD) modes. Temperature of the fluid was recorded using two thermocouples once per second. Results: Control trials produced no stone ablation, while experimental trials produced a staccato groove in the stone surface, simulating efficient lithotripsy. The mean temperature increase for SP was 1.08°C ± 0.04°C for control trials and 0.98°C ± 0.03°C for experimental trials, yielding a mean temperature difference of 0.10°C ± 0.06°C (p = 0.0005). With MD, the mean temperature increase for control trials was 1.03°C ± 0.01°C and for experimental trials 0.99°C ± 0.06°C, yielding a smaller mean temperature difference of 0.04°C ± 0.06°C (p = 0.09). Conclusions: Even under conditions of energy-efficient stone ablation, the majority of applied laser energy (91%–96%) was converted to heat. [ABSTRACT FROM AUTHOR]

Emissions from higher excited states are of theoretical and experimental interest but rare. A series of pure organic phosphors, 2,5-dihexyloxy-4-bromobenzaldehyde (Br6A) derivatives, show intriguing dualphosphorescence characteristics. Their phosphorescence emissions are blue-shifted by 20 nm at room temperature compared to those at 78 K. These shifts are accompanied by increasing contributions from a fast-decaying component. The mechanism responsible for the emission shifts observed for Br6A was studied in a 2,5-dihexyloxy-4-bromobenzene (Br6) solid matrix and solvents of various polarities. While the decay curve for Br6A in the Br6 matrix showed a single slow process, pure Br6A exhibited an additional faster decay. We demonstrated that the faster decay of pure Br6A arises from the T2 state, while Br6A in the Br6 matrix emits solely from T1. Compared to the T1 state (π, π*), the n, π* character of the T2 state ensures more efficient spin-orbit coupling with the ground state, which facilitates faster decay. The larger polarity of Br6A compared to that of Br6 leads to a lower T2 level and a smaller T2-T1 energy gap in pure Br6A, but not when in the Br6 solid matrix, which enables a T1 to T2 thermal population shift in pure Br6A at room temperature. Consistently, the emissions from the Br6A solutions gradually red-shifted with increasing solvent polarity at 78 K. Moreover, the decay curves of Br6A in solvents of low polarity were single-exponential unlike the double-exponential ones observed in polar solvents. These results provide insight into the effect of the environment on the dual phosphorescence emissions of pure organic phosphors. [ABSTRACT FROM AUTHOR]

In spite of their exceptional performance, energetic peroxosolvates are rare. Research in this area is slowed by the poor availibility of concentrated hydrogen peroxide solutions. Presented here is an efficient peroxosolvate discovery method that is applied in the discovery of the first ternary cocrystal comprising only energetic components. [ABSTRACT FROM AUTHOR]

The self-assembly of a range of 1,3-disubstituted benzenes is examined by scanning tunneling microscopy and computational modeling. Intermolecular interactions related to the observation of several molecules in the asymmetric unit and stabilization of pseudopolymorphs are identified.

Author(s): Hee K. Chae [1, 4]; Diana Y. Siberio-Pérez [1, 2]; Jaheon Kim [1]; YongBok Go [1]; Mohamed Eddaoudi [1]; Adam J. Matzger [1, 2]; Michael O'Keeffe (corresponding author) [3, [...]

Remarkable methane uptake is demonstrated experimentally in three metal‐organic frameworks (MOFs) identified by computational screening: UTSA‐76, UMCM‐152 and DUT‐23‐Cu. These MOFs outperform the benchmark sorbent, HKUST‐1, both volumetrically and gravimetrically, under a pressure swing of 80 to 5 bar at 298 K. Although high uptake at elevated pressure is critical for achieving this performance, a low density of high‐affinity sites (coordinatively unsaturated metal centers) also contributes to a more complete release of stored gas at low pressure. The identification of these MOFs facilitates the efficient storage of natural gas via adsorption and provides further evidence of the utility of computational screening in identifying overlooked sorbents. [ABSTRACT FROM AUTHOR]

Hydrate formation is often unavoidable during crystallization, leading to performance degradation of pharmaceuticals and energetics. In some cases, water molecules trapped within crystal lattices can be substituted for hydrogen peroxide, improving the solubility of drugs and detonation performance of explosives. The present work compares hydrates and hydrogen peroxide solvates in two ways: (1) analyzing structural motifs present in crystal structures accessed from the Cambridge Structural Database and (2) developing potential energy surfaces for water and hydrogen peroxide interacting with functional groups of interest at geometries relevant to the solid state. By elucidating fundamental differences in local interactions that can be formed with molecules of hydrogen peroxide and/or water, the analyses presented here provide a foundation for the design and selection of candidate molecules for the formation of hydrogen peroxide solvates. [ABSTRACT FROM AUTHOR]

Varying the degree of ethylene oxide (EO) functionalization of the zirconium MOF UiO-68 affords two novel MOFs; UiO-68-EO and UiO-68-2EO exhibit solvent-free ionic conductivity upon loading LiTFSI in their pores. Incorporating EO chains provides a pathway for lithium ion migration between the coordinated sites and results in an ionic conductivity of 3.8 × 10−7 S cm−1 and 3.9 × 10−4 S cm−1 at 90 °C for UiO-68-EO/LiTFSI and UiO-68-2EO/LiTFSI respectively. [ABSTRACT FROM AUTHOR]

Exerting morphological control over metal‐organic frameworks (MOFs) is critical for determining their catalytic performance and to optimize their packing behavior in areas from separations to fuel gas storage. A mechanism‐based approach to tailor the morphology of MOFs is introduced and experimentally demonstrated for five cubic Zn4O‐based MOFs. This methodology provides three key features: 1) computational screening for selection of appropriate additives to change crystal morphology based on knowledge of the crystal structure alone; 2) use of additive to metal cluster geometric relationships to achieve morphologies expressing desired crystallographic facets; 3) potential for suppression of interpenetration for certain phases. [ABSTRACT FROM AUTHOR]

Halogen‐bonded complexes are often designed by consideration of electrostatic potential (ESP) predictions. ESP predictions do not capture the myriad variables associated with halogen bond (XB) donors and acceptors; thus, binding interaction cannot be quantitatively predicted. Here, a discrepancy between predictions based on ESP energy difference (ΔVs) and computed gas phase binding energy (ΔEbind) motivated the experimental determination of the relative strength of halogen bonding interactions in solution by Raman spectroscopic observation of complexes formed from interacting five iodobenzene‐derived XB donors and four pyridine XB acceptors. Evaluation of ΔEbind coupled with absolutely‐localized molecular orbital energy decomposition analysis (ALMO‐EDA) deconvolutes halogen bonding energy contributions and reveals a prominent role for charge transfer (CT) interactions. Raman spectra reveal ΔEbind accurately predicts stronger interactions within iodopentafluorobenzene (IPFB) complexes than with 1‐iodo‐3,5‐dinitrobenzene (IDNB) complexes even though IPFB has similar electrostatics to IDNB and contains a smaller σ‐hole. [ABSTRACT FROM AUTHOR]