Multi-assessment of critical steno-occlusive middle cerebral arteries: transcranial Doppler combined with magnetic resonance angiography.

Background: Accurate assessment of a stenotic or occluded middle cerebral artery (MCA) is essential before making optimal therapeutic decisions. However, complete occlusion is not always easy to determine for both magnetic resonance angiography (MRA) and neurologists. We aimed to study noninvasive technology using transcranial Doppler (TCD) combined with MRA to assess severe stenosis and occlusion of the MCA. Methods: We studied consecutive patients with severe steno-occlusive MCA by digital subtraction angiography from Oct. 2011 to Mar. 2020 in our stroke center. Hemodynamic measurements of TCD, including peak velocity (PSV), mean flow velocity (MFV) and pulse index (PI), were recorded specifically at the steno-occlusive site by MRA. Results: A total of 152 MCAs of 148 patients were enrolled (60.0 ± 11.5 y, 107 male), including 82 severe stenotic MCAs and 70 occluded MCAs (Group S & Group O) by DSA. There were 86/152 (57%) MCAs showing discontinuity in MRA, which was significantly distributed more in Group O than in Group S (84% vs. 33%, P < 0.001). The PSV and MFV in Group S were greater (264 ± 78 cm/s vs. 33 ± 34 cm/s and 182 ± 61 cm/s vs. 21 ± 23 cm/s, respectively, P < 0.001), while the PI in Group O was greater (0.98 ± 0.49 vs. 0.72 ± 0.17, P < 0.001). PSV was positively correlated with severe MCA stenosis (ß = 0.036, P < 0.001, OR = 0.965, 95% confidence interval (CI): 0.952-0.978). In severe steno-occlusive MCA, using PSV and MFV to detect MCA severe stenosis yielded areas under the curve of 0.983 (CI: 0.964-1.0) and 0.982 (CI: 0.962-1.0), respectively. The cutoff points of PSV ≥ 77 cm/s and MFV ≥ 51 cm/s both yielded an optimized sensitivity of 96.3% and specificity of 98.6%. Conclusion: The critical velocity at the steno-occlusive site is reliable for distinguishing between severe MCA stenosis and occlusion.

Conjugated polymers based on metalla-aromatic building blocks.

Conjugated polymers usually require strategies to expand the range of wavelengths absorbed and increase solubility. Developing effective strategies to enhance both properties remains challenging. Herein, we report syntheses of conjugated polymers based on a family of metalla-aromatic building blocks via a polymerization method involving consecutive carbyne shuttling processes. The involvement of metal d orbitals in aromatic systems efficiently reduces band gaps and enriches the electron transition pathways of the chromogenic repeat unit. These enable metalla-aromatic conjugated polymers to exhibit broad and strong ultraviolet-visible (UV-Vis) absorption bands. Bulky ligands on the metal suppress π-π stacking of polymer chains and thus increase solubility. These conjugated polymers show robust stability toward light, heat, water, and air. Kinetic studies using NMR experiments and UV-Vis spectroscopy, coupled with the isolation of well-defined model oligomers, revealed the polymerization mechanism.

Dynamic Polymer Network System Mediated by Radically Exchangeable Covalent Bond and Carbolong Complex.

It is appealing to develop dynamic polymer systems with multifunctionl properties. Herein, we report a polyurethane elastomer with a dynamic covalent polymer network containing a radically exchangeable 2-arylindane-l,3-dione dimer as thermally sensitive and reversible cross-links. In addition, the carbolong complex, an excellent photothermal agent, is incorporated into the dynamic network backbone. With the irradiation of NIR light, the carbolong complex rapidly generates thermal energy, which subsequently triggers the cleavage of the dynamic covalent bond to generate radicals and activate the polyurethane network. In proof-of-concept experiments, we demonstrate that the utility of a combination of radically exchangeable covalent bond and carbolong moiety brings multiple functional characteristics to the polymer network with a capability of spatiotemporal control, including thermochromism, photochromism, rewritability, malleability, and self-healing. This study holds potentials for exploring more tunable dynamics and improved material properties.

Metallapentalenofuran: Shifting Metallafuran Rings Promoted by Substituent Effects.

Bulky substituents play important roles in controlling the reaction pathways or producing selected products. This work reports that the shift of metallafuran rings in a metallapentalenofuran complex can be promoted by the substituent effect via a reversible C-H bond reductive elimination and oxidative addition. The starting osmapentalyne, a so-called 7-carbon carbolong complex, was produced by the oxidation of a metallapentalenofuran with FeCl3 . It was then allowed to react with nucleophiles, followed by a C-H activation, to give the aforementioned metallapentalenofuran complex. This work enriches the family of carbolong complexes and reveals a new strategy to promote, but not prevent reactions by the bulky substituents.

Synthesis and Characterization of Photothermal Osmium Carbolong Complexes.

Metallacycles with chelating polydentate conjugated-carbon chain ligands are called carbolong complexes, which are expected to have interesting properties. In this work, the preparation of 12-carbon carbolong complexes in which all of the coordinated atoms in the equatorial plane are carbon atoms was studied. With the help of the well-established mechanism, a new approach to prepare coplanar carbolong complexes bearing different organic functional groups was developed by adding different terminal alkynes in sequence. In the presence of HBF4 , these coplanar carbolong complexes were converted to η3 -allyl osmapentalene derivatives, which can be produced directly from the reaction of cyclopropaosmapentalene 1 with terminal alkynes in the presence of AgBF4 under anhydrous conditions. This study offers a new route for the preparation of functional osmium carbolong complexes with excellent photothermal properties, which can be used to prepare photothermal materials.

Cylindrical NIR-Responsive Metallopolymer Containing Möbius Metalla-aromatics.

Metalla-aromatic complexes are very stable and excellent light-absorbing compounds, owing to their highly conjugated frameworks. The metallopolymers containing metalla-aromatic substructures consist of a new type of functional polymer, because they exhibit characteristics of both metalla-aromatic and polymeric units. Herein, we reported a corn-like cylindrical metallopolymer, prepared from the controlled polymerization of N-isopropylacrylamide (NIPAM) by a polyrotaxane-based macroinitiator, followed by postpolymerization modification with a photothermal metalla-aromatic complex. The corn-like shape of this metallopolymer was confirmed by transmission electron microscopy (TEM). Combining the photothermal effect of the metalla-aromatic unit and the thermosensitive property of PNIPAM, the corn-like metallopolymer exhibits a NIR-responsive behavior and represents a new smart material.

A metal-bridged tricyclic aromatic system: synthesis of osmium polycyclic aromatic complexes.

Aromaticity is one of the most important concepts in organic chemistry. A variety of metalla-aromatic compounds have been recently prepared and in most of those examples, the metal participates only in a monocyclic ring. In contrast, metal-bridged bicyclic aromatic molecules, in which a metal is shared between two aromatic rings, have been less developed. Herein, we report the first metal-bridged tricyclic aromatic system, in which the metal center is shared by three aromatic five-membered rings. These metalla-aromatics are formed by reaction between osmapentalyne and arene nucleophiles. Experimental results and theoretical calculations reveal that the three five-membered rings around the osmium center are aromatic. In addition, the broad absorption bands in the UV/Vis absorption spectra of these novel aromatic systems cover almost the entire visible region. This straightforward synthetic strategy may be extended to the synthesis of other metal-bridged polycyclic aromatics.

Unusual eta2-allene osmacycle with apoptotic properties.

Screening of a library of structurally unusual osmacyclic complexes for their antiproliferate properties in HeLa cells led to the discovery of a highly cytotoxic eta2-allene osmacycle. In this remarkably stable complex, osmium constitutes part of a metallacycle through the formation of a sigma-bond to a carbon in combination with coordination to an allene moiety. The osmacycle strongly induces apoptosis in Burkitt-like lymphoma cells at submicromolar concentrations. The reduction of the mitochondrial membrane potential, the induction of DNA fragmentation, and the activation of caspases-9 and -3 reveal that programmed cell death occurs through the intrinsic mitochondrial pathway. From the lipophilic and cationic nature of the osmacycle, in addition to a low oxidation potential (E1/2=+0.27 V vs. Fc/Fc+, Fc=ferrocene) it is proposed that mitochondria are the cellular target where oxidative decomposition initiates apoptosis.

Osmabenzenes from osmacycles containing an eta2-coordinated olefin.

Treatment of HC[triple bond]CC(CH3)(OH)CH=CH2 with [OsCl2(PPh3)3] in dichloromethane yielded the eta2-olefin-coordinated osmacycle [Os{CH=C(PPh3)C(=CH2)-eta2-CH=CH2}Cl2(PPh3)2] (9). Transformations of osmacycle 9 by treatment with benzonitrile under various conditions have been investigated. Reaction of 9 with excess benzonitrile at room temperature afforded the dicationic osmacycle [Os{CH=C(PPh3)C(=CH2)-eta2-CH=CH2}(PhCN)2(PPh3)2]Cl2 (11) by ligand substitution, which reacted further to the intramolecularly coordinated eta2-allene complex [Os{CH=C(PPh3)C(CH3)=(eta2-C=CH2)}(PhCN)2(PPh3)2]Cl2 (12). In contrast, heating a chloroform solution of 9 to the reflux temperature in the presence of excess benzonitrile generated osmabenzene [Os{CHC(PPh3)C(CH3)CHCH}(PhCN)2(PPh3)2]Cl2 (14). Complexes 11, 12 and 14 are in fact isomers. In the absence of excess benzonitrile, the isolated dicationic 12 and 14 readily dissociate the benzonitrile ligands in solution to produce the neutral complex [Os{CH=C(PPh3)C(CH3)=(eta2-C=CH2)}Cl2(PPh3)2] (13) and the monocationic osmabenzene [Os{CHC(PPh3)C(CH3)CHCH}Cl(PhCN)(PPh3)2]BPh4 (15), respectively. Mechanisms for the formation of osmabenzene 14 from 11 and 12 are proposed based on DFT calculations.

Synthesis and characterization of a novel dialdehyde and cyclic anhydride.

The acid treatment of a ruthenabenzene yielded an unusual dialdehyde. Interestingly, this dialdehyde has notable anti-oxidative properties and resists even nitric acid. This stability is confirmed by chemical and electrochemical experiments. In addition, a stable cyclic anhydride is synthesized from the dialdehyde via an environmentally friendly electrochemical method.