Larger Ring Size Research Articles

A molecular sheaf: doubly threaded [6]rotaxane.

We report that the use of a hydrogen-bonded pyrimidine-macrocycle complex can efficiently facilitate the threading of two bispyridinium ethylenes into four rings, as evidenced by X-ray crystallography of its precursor, offering a rare example of a doubly threaded [6]rotaxane in 91% yield. The unusual architecture is found to be stable with no dethreading despite the large ring size of the macrocycle with respect to the stopper.

Ring Transformation of α‐Amino‐β‐oxoesters to δ‐Butyrolactams

Abstractδ‐Butyrolactams with an exocyclic ester moiety in the δ‐position were accessed by reduction of 1‐azido‐2‐cyclopentanone carboxylates with PBu3 or Zn−AcOH. The ring transformation proceeded readily under the conditions of this reduction which is an unprecedented process. Primary amines formed by catalytic hydrogenation of α‐azido‐β‐oxoesters with larger ring sizes or with benzannulation do not show this rearrangement under the conditions of the azide reduction. In these cases, the ring transformation to respective lactams was achieved by treatment of the α‐amino‐β‐oxoesters with a stoichiometric amount of lithium diisopropylamide.

An analytical, mathematical annuloplasty ring curvature model for planning of valve-in-ring transcatheter mitral valve replacement.

An increasing number of high-risk patients with previous mitral valve annuloplasty require transcatheter mitral valve replacement due to recurrent regurgitation. Annulus dilation with a transcatheter balloon is often performed before valve-in-ring transcatheter mitral valve replacement, which is believed to reduce misalignment and paravalvular leakage, yet little evidence exists to support this practice. Our objective was to generate intuitive annuloplasty ring analyses for improved valve-in-ring transcatheter mitral valve replacement planning. We generated a mathematical model that calculates image-tracked differential ring curvature to build quantifications for improved planning for valve-in-ring procedures. Carpentier-Edwards Physio M24 and M30 (n=2 each), Physio II M24 and M26 (n=3 each), LivaNova AnnuloFlex M26 (n=2), and Edwards Geoform M28 (n=2) rings were tested with a 30-mm Toray Inoue balloon inflated to maximum rated pressures. Curvature variance reduces with larger ring sizes, indicating that larger rings are initially more circular than smaller ones. Evaluated semi-rigid and rigid rings showed little to no difference between pre- and post-dilation states. Annuloflex rings (flexible band) showed a postdilation variance reduction of 32.83% (P<.001) followed by an increase after 10minutes of relaxation that was still reduced by 19.62% relative to the initial state (P<.001). We discovered that balloon dilation does not significantly deform evaluated semi-rigid or rigid rings at maximum rated balloon pressures. This may mean that dilation for these conditions before valve-in-ring transcatheter mitral valve replacement is unnecessary. Our mathematical approach creates a foundation for extended classification of this practice, providing meaningful quantification of ring geometry.

Rotaxane Formation of Multicyclic Polydimethylsiloxane in a Silicone Network: A Step toward Constructing “Macro‐Rotaxanes” from High‐Molecular‐Weight Axle and Wheel Components

AbstractRotaxanes consisting of a high‐molecular‐weight axle and wheel components (macro‐rotaxanes) have high structural freedom, and are attractive for soft‐material applications. However, their synthesis remains underexplored. Here, we investigated macro‐rotaxane formation by the topological trapping of multicyclic polydimethylsiloxanes (mc‐PDMSs) in silicone networks. mc‐PDMS with different numbers of cyclic units and ring sizes was synthesized by cyclopolymerization of a α,ω‐norbornenyl‐functionalized PDMS. Silicone networks were prepared in the presence of 10–60 wt % mc‐PDMS, and the trapping efficiency of mc‐PDMS was determined. In contrast to monocyclic PDMS, mc‐PDMSs with more cyclic units and larger ring sizes can be quantitatively trapped in the network as macro‐rotaxanes. The damping performance of a 60 wt % mc‐PDMS‐blended silicone network was evaluated, revealing a higher tan δ value than the bare PDMS network. Thus, macro‐rotaxanes are promising as non‐leaching additives for network polymers.

Rotaxane Formation of Multicyclic Polydimethylsiloxane in a Silicone Network: A Step toward Constructing "Macro-Rotaxanes" from High-Molecular-Weight Axle and Wheel Components.

Rotaxanes consisting of a high-molecular-weight axle and wheel components (macro-rotaxanes) have high structural freedom, and are attractive for soft-material applications. However, their synthesis remains underexplored. Here, we investigated macro-rotaxane formation by the topological trapping of multicyclic polydimethylsiloxanes (mc-PDMSs) in silicone networks. mc-PDMS with different numbers of cyclic units and ring sizes was synthesized by cyclopolymerization of a α,ω-norbornenyl-functionalized PDMS. Silicone networks were prepared in the presence of 10-60 wt % mc-PDMS, and the trapping efficiency of mc-PDMS was determined. In contrast to monocyclic PDMS, mc-PDMSs with more cyclic units and larger ring sizes can be quantitatively trapped in the network as macro-rotaxanes. The damping performance of a 60 wt % mc-PDMS-blended silicone network was evaluated, revealing a higher tan δ value than the bare PDMS network. Thus, macro-rotaxanes are promising as non-leaching additives for network polymers.

Alignment & stability challenges for FCC-ee

In order to achieve its ultra-low vertical emittance (1 pm) and high luminosity (of up to 230 times 10^{34}text{ cm}^{-2}text{ s}^{-1} per collision point), the e+e− Future Circular Collider (FCC-ee) requires a well-informed alignment strategy, powerful correction methods, and good understanding of the impact of vibrations. The large ring size, high natural chromaticity, small beta ^{*}, and the low coupling ratio make the FCC-ee design susceptible to misalignment and field errors, which if not properly addressed, threaten to increase the horizontal and vertical emittances and adversely affect the luminosity. Tight alignment tolerances around the 100 km ring would be a major cost driver and therefore alignment and stability need to be carefully studied. In this paper we present a status update, in which we apply analytical estimate methods, verified with simulation data, to determine the influence of the alignment of specific magnet types with the result informing the relative alignment tolerances. This is followed by simulations of a correction strategy that includes a large set of magnet misalignments and field errors. Finally, we also consider the tolerances on vibrations of quadrupoles through evaluating three cases: coherent vibration due to external seismic motion, vibrations resonant with the betatron frequency, and non-resonant, incoherent vibration.

Expanded triazolophanes: a topological analysis of vesicular assembly.

Triazolophanes with larger ring sizes such as 40- and 42- were designed and synthesized. Ultramicroscopic studies on a variety of expanded triazolophanes and larger acyclic systems revealed vesicular self-assembly. The role of molecular topology on vesicular assembly was systematically investigated by studying a series of molecules with increasing curvature.

Hexagonal Planar [B6H6] within a [B6H12] Borate Complex: Structure and Bonding of [(Cp*Ti)2(μ‐ɳ6 : ɳ6‐B6H6)(μ‐H)6

AbstractIsolation of planar [B6H6] is a long‐awaited goal in boron chemistry. Several attempts in the past to stabilize [B6H6] were unsuccessful due to the domination of polyhedral geometries. Herein, we report the synthesis of a triple‐decker sandwich complex of titanium [(Cp*Ti)2(μ‐η6 : η6‐B6H6)(μ‐H)6] (1), which features the first‐ever experimentally achieved nearly planar six‐membered [B6H6] ring, albeit within a [B6H12] borate. The small deviation from planarity is a direct consequence of the predicted structural pattern of the middle ring in 24 Valence Electron Count (VEC) triple‐decker complexes. The large ring size of [B6H6] in 1 brings the metal–metal distance into the bonding range. However, significant electron delocalization from the M−M bonding orbital to the bridging hydrogen and B−B skeleton in the middle decreases its bond strength.

Hexagonal Planar [B6 H6 ] within a [B6 H12 ] Borate Complex: Structure and Bonding of [(Cp*Ti)2 (μ-ɳ6 : ɳ6 -B6 H6 )(μ-H)6

Isolation of planar [B6 H6 ] is a long-awaited goal in boron chemistry. Several attempts in the past to stabilize [B6 H6 ] were unsuccessful due to the domination of polyhedral geometries. Herein, we report the synthesis of a triple-decker sandwich complex of titanium [(Cp*Ti)2 (μ-η6 : η6 -B6 H6 )(μ-H)6 ] (1), which features the first-ever experimentally achieved nearly planar six-membered [B6 H6 ] ring, albeit within a [B6 H12 ] borate. The small deviation from planarity is a direct consequence of the predicted structural pattern of the middle ring in 24 Valence Electron Count (VEC) triple-decker complexes. The large ring size of [B6 H6 ] in 1 brings the metal-metal distance into the bonding range. However, significant electron delocalization from the M-M bonding orbital to the bridging hydrogen and B-B skeleton in the middle decreases its bond strength.

Efficient Synthesis and Cyclic Molecular Topology of Ultralarge-Sized Bicyclic and Tetracyclic Polymers

Cyclic polymers have been extensively studied because of their unique topology and physical properties, while the methods for efficient synthesis of well-defined bicyclic and multicyclic polymers are limited. Herein, an effective strategy was developed to synthesize ultralarge-sized bicyclic polymers by a ring-opening metathesis polymerization (ROMP)-based blocking-cyclization technique in a simplified feeding procedure, using the short ladderphane bearing four living ends as the initial motif. The molecular topology of the bicyclic polymer was clarified by pieces of evidence and validated by theoretical simulation. Importantly, the visualized eight-shaped molecular topology was observed. Meanwhile, the bicyclic polymer exhibited stronger thermal, fluorescence emission, and mechanical properties and better dielectric and energy storage performance than its four-arm counterpart, which elucidated the difference in molecular topology between bicyclic and four-arm polymers. Moreover, a tetracyclic polymer with a large ring size could be readily obtained. Therefore, this designed strategy opens new horizons for building bicyclic and multicyclic polymers using the conventional ROMP and commercial Grubbs catalyst.

Integrated Coherent Tunable Laser (ICTL) With Ultra-Wideband Wavelength Tuning and Sub-100 Hz Lorentzian Linewidth

This paper describes the design, fabrication, and record performance of a new class of ultra-wideband wavelength tuning, ultra-low noise semiconductor laser, the Integrated Coherent Tunable Laser (ICTL). The ICTL device is designed for, and fabricated in, a CMOS foundry based Silicon Photonics platform, utilizing heterogeneous integration of III-V material to create the integrated gain section of the laser&#x2013;enabling high-volume mass-market manufacturing at low cost and with high reliability. The ICTL incorporates three or more ultra-low loss micro-ring resonators, with large ring size, in a Sagnac loop reflector geometry, creating exceptional laser reflector performance, plus an extended laser cavity length that enables highly-coherent output; ultra-low linewidth and phase noise. This paper describes record integrated laser performance; 118 nm wavelength tuning, covering S-, C- and L-bands, with Lorentzian linewidth &lt;100 Hz, and with excellent relative intensity noise (RIN) of &#x2264; &#x2212;155 dBc&#x002F;Hz. The remarkable performance of the ICTL device, coupled with the high volume&#x002F;low cost capability of the Silicon Photonics platform enables next-generation applications including ultra-wideband WDM transmission systems, fiber-optic and medical-wearable sensing systems, and automotive FMCW LiDAR systems utilizing wavelength scanning.

Synthesis of ester-free type poly(trimethylene carbonate) derivatives bearing cycloalkyl side groups

Our ultimate goal is to create a library of ester-free type trimetylene carbonate derivatives, so that we can design and produce poly(trimethylene carbonate) (PTMC) derivatives that meet application needs. Herein we introduced cycloalkyl groups (cyclopentyl, cyclohexyl and cycloheptyl groups) into the side chain of an ester-free type PTMC. Previously, ester-free type PTMC derivatives with aromatic rings in the side chain have been reported from our group, but there have been no reports of aliphatic cyclic compounds introduced with ether linkage into their side chains. This research makes possible the production of more versatile ester-free PTMC derivatives using cycloalkyl groups. The effect of ring size was also investigated. All of the monomers gave homopolymers with Mn of a few thousands, improving the thermal degradation temperatures, compared to unmodified PTMC. We found a tendency towards increasing glass transition temperature with larger ring size.

Conformer Separation of Dibenzo-Crown-Ether Complexes with Na+ and K+ Ions Studied by Cryogenic Ion Mobility-Mass Spectrometry.

We performed cryogenic ion mobility-mass spectrometry (IM-MS) to study conformations of dibenzo-crown-ether complexes with Na+ and K+ ions at 86 K in the gas phase. Four dibenzo-crown-ethers (dibenzo-18-crown-6, dibenzo-21-crown-7, dibenzo-24-crown-8, and dibenzo-30-crown-10) with different cavity ring sizes were investigated. For dibenzo-18-crown-6 complexes with Na+ and K+, only one type of conformer was assigned by comparing the experimental collision cross sections with those predicted theoretically for candidate structures. In this conformer, the distance between two benzene rings in the complexes was long due to the open form of the dibenzo-18-crown-6. This open conformer was consistent with the previous laser spectroscopic studies of the cold complex ions in the gas phase. For dibenzo-21-crown-7 and dibenzo-24-crown-8 complexes with Na+ and K+, two types of conformers were clearly separated by IM-MS. These two conformer types were assigned to "open" and "closed" forms in which benzene-benzene distances were long and short, respectively. Observed relative abundances of the open and closed conformers qualitatively agreed with the Boltzmann distribution using Gibbs energies of the conformers calculated by quantum chemical calculations. For the Na+(dibenzo-30-crown-10) complex, open and closed conformers were also observed in IM-MS. On the other hand, only the closed conformer was observed for the K+(dibenzo-30-crown-10) complex. This closed conformer was similar to the "wraparound" structure, which was proposed in the previous studies in the solution. In conclusion, the closed conformers were formed by the deformation of flexible crown ethers with large cavity ring sizes. In addition, the diameter of the K+ ion was suitable to form the closed conformer by deformation of the molecular structure of dibenzo-30-crown-10.

Stability of magnetic rings

Linear stability of magnetic rings consisting of permanently magnetized particles p of the same magnetization is studied. Employing Lagrange’s approach and multipole moments, we determine the stability criterion in closed form. We then apply this criterion to characterize the stability for two scenarios in which the ring is i) compressed by dipolar loading due to a central point dipole and ii) compressed by mechanical loading. In contrast to previous works which show break up of magnetic rings under homogenous external magnetic field when instability occurs, we find that the ring does not break up when instability arises in both situations considered. However, the loading scenario decides instability modes via which the magnetic ring first loses its stability. For the first scenario, the ring deforms into planar but noncircular shapes via in-plane instability modes, regardless of ring sizes. For the other scenario, the ring deforms into planar but noncircular or nonplanar shapes via in-plane or out-of-plane instability modes for, respectively, small ring sizes or sufficiently large ring sizes. Finally, a simple experiment for the case of dipolar loading is proceeded and experimental results show good agreement with theoretical predictions.

Self-assembly of cyclic grafted copolymers with rigid rings and their potential as drug nanocarriers

Enhancing the performance of polymer micelles by purposeful regulation of their structures is a challenging topic that receives widespread attention. In this study, we systematically conduct a comparative study between cyclic grafted copolymers with rigid and flexible rings in the self-assembly behavior via dissipative particle dynamics (DPD) simulation. With a focus on the possible stacking ways of rigid rings, we propose the energy-driven packing mechanism of cyclic grafted copolymers with rigid rings. For cyclic grafted copolymers with large ring size (14 and 21-membered rings), rigid rings present a novel channel-layer-combination layout, which is determined by the balance between the potential energy of micelles (Emicelle) and the interaction energy between water and micelles (Eint). Based on this mechanism, we further regulate a series of complex self-assembling structures, including curved rod-like, T-shape, annular and helical micelles. Compared with flexible copolymers, cyclic grafted copolymers with rigid rings provide a larger and loose hydrophobic core and higher structural stability with micelles due to the unique packing way of rigid rings. Therefore, their micelles have a great potential as drug nanocarriers. They possess a better drug loading capacity and disassemble more quickly than flexible counterparts under acidic tumor microenvironment. Furthermore, the endocytosis kinetics of rigid micelles is faster than the flexible counterparts for the adsorption and wrapping process. This study may provide a reasonable idea of structural design for polymer micelles to enhance their performance in biomedical applications.

Clinical impact of the repair technique for posterior mitral leaflet prolapse: Resect or respect?

Leaflet resection and chordal reconstruction are established repair techniques for posterior mitral valve (MV) prolapse. This study aimed to compare the clinical results of the resect and respect approaches, with a particular focus on MV hemodynamics. Overall, 291 patients who underwent elective MV repair for isolated posterior leaflet prolapse between 2012 and 2020 were enrolled. Patients who underwent leaflet resection alone were classified as the "resection" group (n = 166), while patients who underwent neochordal replacement with/without limited leaflet resection were classified as the "respect" group (n = 125). Early postoperative MV hemodynamics and midterm repair durability were compared between the groups. The annuloplasty ring size was significantly larger in the respectgroup than in the resection group (31.0 ± 2.1vs. 30.4 ± 2.0 mm, p = .028). The respectgroup showed significantly lower mean MV gradient (2.6 ± 1.1vs. 3.0 ± 1.4 mmHg, p = .03) and larger effective orifice area (EOA) (1.86 ± 0.48vs. 1.66 ± 0.47 cm2 , p < .001) than the resection group. Multivariable analysis identified the respect approach, younger age, female sex, larger ring size, and partial band as independent determinants of larger EOA. The rate of freedom from moderate or greater recurrent mitral regurgitation 5 years postoperatively was 90.9% in both groups. The respect approach allowed for a lower MV gradient and a larger EOA than the resection approach, which is possibly due to the capability of implanting a larger annuloplasty ring.

Rational design of cell-permeable cyclic peptides containing a d-Pro-l-Pro motif

Cyclic peptides are capable of binding to challenging targets (e.g., proteins involved in protein-protein interactions) with high affinity and specificity, but generally cannot gain access to intracellular targets because of poor membrane permeability. In this work, we discovered a conformationally constrained cyclic cell-penetrating peptide (CPP) containing a d-Pro-l-Pro motif, cyclo(AFΦrpPRRFQ) (where Φ is l-naphthylalanine, r is d-arginine, and p is d-proline). The structural constraints provided by cyclization and the d-Pro-l-Pro motif permitted the rational design of cell-permeable cyclic peptides of large ring sizes (up to 16 amino acids). This strategy was applied to design a potent, cell-permeable, and biologically active cyclic peptidyl inhibitor, cyclo(YpVNFΦrpPRR) (where Yp is l-phosphotyrosine), against the Grb2 SH2 domain. Multidimensional NMR spectroscopic and circular dichroism analyses revealed that the cyclic CPP as well as the Grb2 SH2 inhibitor assume a predominantly random coil structure but have significant β-hairpin character surrounding the d-Pro-l-Pro motif. These results demonstrate cyclo(AFΦrpPRRFQ) as an effective CPP for endocyclic (insertion of cargo into the CPP ring) or exocyclic delivery of biological cargos (attachment of cargo to the Gln side chain).

Tuning the thermal properties of poly(ethylene)‐like poly(esters) by copolymerization of ε‐caprolactone with macrolactones, in the presence of a pyridylamidozinc(II) complex

ABSTRACTLinear aliphatic poly(ester)s, as thermoplastic materials, are more and more envisaged as the potential “green” alternative to traditional plastics. Aliphatic polyesters having long methylene chain behave as “polyethylene‐like” materials and can be prepared by ring‐opening polymerization (ROP) of macrolactones. A pyridylamidozinc(II) complex was used for the ROP of ε‐caprolactone (CL) and of two large ring size lactones, the ω‐6‐hexadecenlactone (6HDL) and the ω‐pentadecalactone (PDL). High turnover frequencies were observed for the CL polymerization, while for the macrolactones, an entropy‐driven behavior was recognized. Random copolymerizations of the PDL with 6HDL and of the macrolactones with CL were successfully achieved, and the copolymer microstructure was ascertained by NMR and MALDI analyses. The copolymer melting temperatures, measured by DSC, and the thermal degradation behavior, studied by TGA in nitrogen and air atmosphere, were dependent on the copolymer's composition. © 2020 Wiley Periodicals, Inc. J. Polym. Sci.2020,58, 528–539

Molecular mechanism of the expansion of silica glass upon exposure to moisture

AbstractMolecular dynamics simulations show that the expansion of silica glass occurs by the presence of the hydroxyl (SiOH) groups present in the glass as opposed to intact water (H2O) molecules, providing an accurate molecular description of the experimentally observed volume changes in silica glass exposed to water. Using a robust and accurate reactive potential, the simulations show that the expansion is caused by the rupture of siloxane (Si–O–Si) linkages in the glass via reactions with water molecules, forming SiOHs. Such reactions remove smaller rings and form larger rings, with a decrease in the overall number of rings smaller than a prescribed large ring size in comparison to dry glasses. This change in ring structure overcomes the inherently stronger hydrogen bonding in the glasses containing SiOH in comparison to the glasses containing predominantly intact H2O molecules. This stronger H‐bonding of the SiOH also causes a shift to lower frequencies in the high‐frequency OH vibrational spectrum for the silanols, as shown in previous ab‐initio calculations. This introduces a question about assuming the lower frequency part of the high‐frequency peak is only due to intact H2O molecules. A slight decrease in volume occurred in the glasses containing the largest concentration of intact H2O molecules. There is no change in the ring size distribution between the H2O glasses and dry glasses. Rather, the slight decrease in volume in the H2O system is caused by a decrease in siloxane bond angles caused by the formation of H‐bonds between the H2O molecules and the glass O in the siloxane cages surrounding the H2O molecules.

Friction and Wear Behavior of Environmentally Friendly Ionic Liquids for Sustainability of Biolubricants

The sustainability of biolubricants as green alternatives for industrial and machinery lubrication is questionable due to their unreliable oxidative stability, high pour point, and easy accumulation of contaminants that affect their tribological performance. Bio-based ionic liquid (IL) lubricants, which are environmentally friendly liquid state salts, have overcome these concerns related to conventional biolubricants. The present study investigates the effect of varying cation–anion moieties in ILs to understand their tribological performance and industrial viability. The industrial viability was analyzed by scaling their friction and wear behaviors against conventional biolubricants, and petroleum-based oils. The study investigated both bio- and nonbio-based ILs. Among the ILs examined, P666,14Saccharinate, P666,14Salicyate, and P666,14Benzoate were found to have superior tribological properties. The presence of large alkyl cation chain length and large aromatic anion ring size in ILs can effectively reduce friction and wear. This study details the mechanism by which the structural combinations of anion and cation in ILs define the tribological behavior of the bulk IL. Additionally, this study also highlights the environmentally benign nature of IL lubricants for possible industrial applications.