Head-to-tail regioregular poly­(4-alkylthiazole)­s containing silylethers in the side-chains were synthesized via Kumada-Coupling polycondensation of “reversed” monomers, that were metalated at the sterically hindered 5-position. Their optical, electrochemical, and bulk properties have been studied, and evidence is presented that indicates the occurrence of quasi-living chain-growth behavior in the polymerization process. Two polymers, PTzTIP and PTzDIBO, featuring triisopropylsilyl and diisobutyloctadecylsilyl side chains, respectively, were prepared. PTzTIP is largely insoluble, while PTzDIBO is fully soluble in common organic solvents, including hexane, and readily gave number-averaged molecular weights exceeding 100 kDa, corresponding to an average degree of polymerization greater than 200, as determined via gel-permeation chromatography (GPC) in CHCl3. The formation of a regular head-to-tail regiostructure could be confirmed through comparison with a head-to-head–tail-to-tail regioregular polybithiazole (PBTzTIP), synthesized via Yamamoto-polymerization of a head-to-head-linked bithiazole. Regioregular PTzDIBO could be obtained via different polymerization protocols, including external initiation with two new aryl-nickel-complexes, which furnished material with particularly low polydispersities (<1.4 at M n > 100 kDa). Furthermore, a direct correlation between the obtained molecular weight and the monomer/catalyst ratio was observed in series of batch polymerization experiments, in agreement with a chain-growth polycondensation process. The incorporation of the precatalyst–aryl moiety into the polymer chains could be proven by comparison with a model compound. The functionalized end-groups allowed to independently determine the molecular weight via 1H NMR, which gave good agreement with the values obtained from GPC, further corroborating the occurrence of chain-growth.

In this work we report on a preparative strategy that allows the facile tuning of the electron affinities of π-conjugated organic n-type materials via intramolecular N→B coordination: 2fold hydroboration of a pyrazine-derived substrate with 9Hborabicyclo[3.3.1]nonane (9H-BBN) and Piers' borane ((C 6 F 5 ) 2 BH) furnishes the intramolecularly N→B-coordinated compounds PzBBN and PzBPF in high yield. For each borane racemic mixtures of the respective chiral derivatives and achiral meso compounds have been isolated, and their electrochemical, optical, and structural properties have been investigated and complemented by DFT calculations. The boranes exhibit high electron affinities with electrochemical LUMO energy levels of −3.69 and −4.30 eV, respectively. The corresponding radical anions PzBBN •− and PzBPF •− can be reversibly generated and are stable in solution at ambient temperature. Analysis of the radical species by EPR spectroscopy and single-crystal analysis of [PzBPF] •− [CoCp 2 ] + allowed further corroboration of the π-delocalized nature of these radicals.

Objective Patients undergoing transcatheter aortic valve implantation (TAVI) frequently present with chronic kidney disease and are therefore particularly susceptible to nephrotoxic influences like iodinated contrast media. Acute kidney injury after TAVI is a severe complication that independently predicts short- and long-term mortality. The present study investigates the feasibility of a contrast-free approach by using intravascular ultrasound (IVUS) in conjunction with fluoroscopy. Methods Six domestic pigs (60 ± 5 kg) were anesthetized and underwent transapical implantation of a balloon-expandable transcatheter heart valve. In the control group ( n = 3), the procedures were guided by fluoroscopy/angiography. In the study group ( n = 3), the procedures were guided by IVUS for preimplantation evaluation, intra-procedural guidance, and post-implantation evaluation, in conjunction with fluoroscopy without contrast. The procedures were evaluated by IVUS, fluoroscopy, aortic root angiography, and explantation and dissection of the hearts. Results Relevant anatomical landmarks for correct implantation were assessed by IVUS. The following annulus measurements were obtained: area (359.67 ± 29.58 mm2), perimeter (68.28 ± 2.63 mm), maximum diameter (22.20 ± 1.22 mm), minimum diameter (20.43 ± 1.12 mm), mean diameter (21.32 ± 0.70 mm), ellipticity index (1.09 ± 0.10), and area-derived diameter (21.39 ± 0.87 mm). IVUS-guided valve deployment resulted in correct expansion within the aortic annulus without signs of paravalvular leak, compromised mitral valve, or coronary obstruction. IVUS-guided post-implantation assessment confirmed circular expansion (25.88 ± 0.30 mm) of the valves. Conclusions IVUS-guided, contrast-free transapical TAVI is feasible in a porcine model.