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Nitric oxide (NO) has many important physiological functions, including its ability to inhibit platelet activation and serve as potent antimicrobial agent. The multiple roles of NO in vivo have led to great interest in the development of biomaterials that can deliver NO for specific biomedical applications. Herein, we report a simple solvent impregnation technique to incorporate a nontoxic NO donor, S-nitroso-N-acetylpenicillamine (SNAP), into a more biocompatible biomedical grade polymer, CarboSil 20 80A. The resulting polymer-crystal composite material yields a very stable, long-term NO release biomaterial. The SNAP impregnation process is carefully characterized and optimized, and it is shown that SNAP crystal formation occurs in the bulk of the polymer after solvent evaporation. LC-MS results demonstrate that more than 70% of NO release from this new composite material originates from the SNAP embedded CarboSil phase, and not from the SNAP species leaching out into the soaking solution. Catheters prepared with CarboSil and then impregnated with 15 wt % SNAP provide a controlled NO release over a 14 d period at physiologically relevant fluxes and are shown to significantly reduce long-term (14 day) bacterial biofilm formation against Staphylococcus epidermidis and Pseudonomas aeruginosa in a CDC bioreactor model. After 7 h of catheter implantation in the jugular veins of rabbit, the SNAP CarboSil catheters exhibit a 96% reduction in thrombus area (0.03 ± 0.01 cm2/catheter) compared to the controls (0.84 ± 0.19 cm2/catheter) (n = 3). These results suggest that SNAP impregnated CarboSil can become an attractive new biomaterial for use in preparing intravascular catheters and other implanted medical devices.

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 [...]

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, [...]

The CpCo-mediated cyclization of alpha,delta,omega-enediynes allows easy isomerization of strained tricyclic dienes. The double-bond rearrangement of cyclohexadiene units, controlled by CpCo, occurs through eta(super 4) to eta(super 2) shifts followed by endo-C-H activation. The H-shifts in the reaction at room temperature occur by means of the intermediate intramolecular (2+2+2) cycloaddition products. The synthesis is easy due to the strain activation of the initial tricyclic diene system.

Several reactions are conducted for the development of a series of various six-ring oligothiophenes containing one to three degrees of ring fusion. The different effects of position and extent of ring fusion on the electronic properties of the compounds are also explained.

The effect of position and degree of sulfur oxidation on the fundamental properties of a series of planarized thieno[3,2-b]thiophene S,S-dioxides derivatives are studied. Position of oxidation is found to be the most critical factor in controlling electronic properties.

The critical role of crystal form in determining the properties of chiral ligands is demonstrated for VAPOL. It is reported that the classical hydrogen bonds are absent in all three of the crystal structures of unsolvated VAPOL.

A combination of Stille and oxidative coupling reaction are used to synthesize a series of fused-ring aligothiophenes. A blue shift of the maximum emission wavelength, and a correspondingly smaller stokes shift, is the outcome of the introduction of sulfur linkage into these oligothiophenes.

The structure of S(C triplebond CH)(sub 2) was investigated by high-resolution spectroscopy, the results of which is discussed together with the high level ab initio calculations of S(C triplebond CH)(sub 2). The study revealed that the S singlebond C triplebond linkages were nonlinear in both the title compounds as if the carbons distant from the sulfur were repelling each other.

Issues concerning the interaction between topographic and electronic factors in a scanning tunneling microscopy (STM) image are discussed. STM is a useful technique for assessing the different packing arrangements of adsorbates on a surface in equilibrium with the adsorbed molecules dissolved in solution phase.

The effect of position and degree of sulfur oxidation on the fundamental properties of a series of planarized thieno[3,2-b]thiophene S,S-dioxides derivatives was studied. The optical data reveal a red shift in the longest wavelength of absorption relative to the nonoxidized analogues that is indicative of a reduced HOMO-LUMO gap. The position of oxidation rather than the extent of oxidation is the most critical factor in controlling electronic properties. Single-crystal analysis reveals that some of the oligothiophene S,S-dioxides studied present π-π interactions which are completely absent in the nonoxidized analogue. [ABSTRACT FROM AUTHOR]

This paper describes the systematic study of metal-organic framework (MOF) catalysts for the reaction of propylene oxide (PO) with carbon dioxide (CO 2 ) to generate propylene carbonate (PC). These studies began with the evaluation of MIL-101(Cr) as catalyst in a flow reactor. Under the developed flow conditions, MIL-101(Cr) was found to effectively catalyze PO carbonation in the absence of a halide co-catalyst. A systematic study of catalyst performance was then undertaken as a function of MOF synthesis technique, activation conditions, metal center, and node architecture. Ultimately, these investigations led to the identification of MIL-100(Sc) as a new, active, and stable catalyst for PO carbonation., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)