We report the one-step synthesis of a double-tethered metallacyclobutane molybdenum catalyst for ring expansion metathesis polymerization, a method increasingly popular for cyclic polymer production. The metallacyclobutane's geometry, based on 13C NMR and DFT analysis, suggests it should not participate in metathesis. However, polymerization of norbornene showed high activity (an upper limit of 1,000,000,000 gpolymer molcat -1 h-1). DFT studies reveal that the catalyst's slow initiation and fast propagation arise from a self-accelerating effect triggered by increasing steric demand, causing a geometry shift from square-pyramidal to trigonal bipyramidal. This insight will advance catalyst design principles and, in the future, allow for more precise control of the molecular weight, dispersity, and tacticity.

A series of polystyrene-based polymers that are randomly functionalized with Au(I) chromophores that exhibit phosphorescence and electrophosphorescence are reported. The polymers feature side-chain conjugated moieties that are based on R3P-Au(I)-C equivalent to C-Ar (where Ar = phenyl or 1-naphthyl and R = ethyl or phenyl) and a novel digold triazole functionality that is derived from an iClick reaction between R3P-Au(I)-N3 and the R3P-Au(I)-C equivalent to C-Ar units. The R3P-Au(I)-C equivalent to C-Ar substituted polymers are prepared by the reaction of R3P-AuCl with the ethynyl-functionalized polystyrenes (10 mol % ethynyl groups). Subsequently, an iClick reaction is carried out on the R3P-Au(I)-C equivalent to C-Ar functionalized polymers to afford the digold triazole functionalized polymers. The iClick reactions are monitored by in situ 1H and 31P NMR spectroscopy. Molecular dynamics (MD) simulations of the monogold R3P-Au(I)-C equivalent to C-Ar polymers reveal that there are significant attractive interactions between the metalated repeat units, especially in the polymers featuring triethylphosphine ligands at the Au(I) centers (e.g., Et3P-Au(I)-C equivalent to C-Ar). The photophysical study of the polymers reveals that the emission is dominated by phosphorescence from 3 pi,pi* excited states localized on the metalated units. The phenyl-based polymers exhibit phosphorescence in the blue region (lambda max similar to 435 nm), whereas the naphthyl-based polymers exhibit yellow-red phosphorescence (lambda max similar to 600 nm). Preliminary studies demonstrate the application of side-chain functionalized polymers in electroluminescent devices.

Photoactivation of nitroarenes has been recently reported to induce the transformation of alkenyl bonds into carbonyl functionalities. Capitalizing on this unique photochemical mechanism, this study explores the use of nitroarenes to achieve oxidative cleavage of olefinic polymers under visible light irradiation. The degradation of various olefinic polymers, including commercially available polybutadiene, polynorbornene, both linear and cyclic poly(phenylacetylene), as well as backbone-modified polyacrylates with alkenyl functionality was investigated. To elucidate the efficacy of this methodology, a series of nitroarene derivatives bearing variable substituents were screened for their degradative efficiency on polybutadiene. Varying nitroarene stoichiometry, reaction temperature, and pos-treaction workup conditions were investigated to optimize degradation conditions. The results demonstrated that photoexcited nitroarenes enable efficient oxidative degradation of olefinic polymers in a safe and sustainable manner, providing a novel strategy for mild macromolecular deconstruction.

Polyacetylene, a versatile material with an electrical conductivity that can span 7 orders of magnitude, is the prototypical conductive polymer. In this letter, we report the observation of a significant Overhauser effect at the high magnetic field of 14.1 T that operates at 100 K and room temperature in both linear and cyclic polyacetylene. Significant NMR signal enhancements ranging from 24 to 45 are obtained. The increased sensitivity enabled the characterization of the polymer chain defects at natural abundance. The absence of end methyl group carbon-13 signals provides proof of the closed-loop molecular structure of cyclic polyacetylene. The remarkable efficiency of the soliton based Overhauser effect DNP mechanism at high temperature and high field holds promise for applications and extension to other conductive polymer systems.

Antithrombin (AT) deficiency in the extracorporeal circulation during cardiac surgery leads to uncontrolled inflammation and vascular damage in patients. AT levels decrease in sepsis, major trauma, extracorporeal membrane oxygenation, and eclampsia. Monitoring plasma AT levels facilitates the accurate restoration of AT to baseline values through precise supplementation. Traditional methods of chromogenic assay and enzyme-linked immunosorbent assay (ELISA) kits encounter challenges, such as interference, inconsistency, and delayed response times, making real-time, reliable antithrombin monitoring a clinical gap. To address this critical need, we develop a heparin-bead extraction enhanced fluoroGenic aptamer-thrombin composite reporter (HExGATOR) for the rapid, sensitive, and precise detection of functional AT in plasma. Our design employs thrombin-binding aptamers and a fluorescence "turn on" technology such that a signal is produced upon the interaction of AT with the otherwise "turned off" aptamer-thrombin complex. The prominent signal-background interference originating from plasma is remarkably diminished by using a heparin-bead solid-phase extraction of AT. We achieved highly sensitive and rapid detection of AT in 5 to 20 min with a limit of detection of 15.11 nM. This approach offers a promising alternative to traditional AT tests in clinical settings, potentially facilitating personalized anticoagulant therapy.

Cyclic polymers have applications across various fields, including material science, biomedicine, and inorganic chemistry. Cyclic polymers derived from alkyne monomers have expanded the application scope to include electronic materials and polyolefins. This review highlights recent advancements in the synthesis of cyclic polymers from both mono- and disubstituted alkynes. The aim is to provide a comprehensive overview of the synthetic methodologies and the application of cyclic polymers derived from alkynes. Additionally, this review will facilitate a comparative analysis of the advantages and limitations of various synthetic methods and describe opportunities for future development of novel catalytic systems to synthesize cyclic polymers from alkynes.

Cyclooctyne reacts with the trianionic pincer ligand supported alkylidyne [tBuOCO]WCC(CH3)3(THF)2 (1) to yield tungstacyclopropene (3) and tungstacyclopentadiene (4) complexes. The ratio of 3 and 4 in the reaction mixture depends on the stoichiometry of the reaction. The maximum concentration of 3 occurs with one equiv. of cyclooctyne and 4 is the exclusive product of the reaction above three equivalents. Both complexes 3 and 4 convert to the cyclooctyne ring-opened product 5 upon heating. While the conversion of 4 to 5 is accompanied by formation of polycyclooctyne as a white precipitate during the reaction, conversion of 3 to 5 is homogeneous. Exhibiting Ring Expansion Polymerization (REP), complexes 4 and 5 initiate the polymerization of phenylacetylene to generate cyclic poly(phenylacetylene) (c-PPA).

Described here is a direct entry to two examples of 3d transition metal catalysts that are active for the cyclic polymerization of phenylacetylene, namely, [(BDI)M{κ 2 - C , C -(Me 3 SiC 3 SiMe 3 )}] ( 2-M ) (BDI=[ArNC(CH 3 )] 2 CH − , Ar=2,6- i Pr 2 C 6 H 3 ; M = Ti, V ). Catalysts are prepared in one step by the treatment of [(BDI)MCl 2 ] ( 1-M , M = Ti , V ) with 1,3-dilithioallene [Li 2 (Me 3 SiC 3 SiMe 3 )]. Complexes 2-M have been spectroscopically and structurally characterized and the polymers that are catalytically formed from phenylacetylene were verified to have a cyclic topology based on a combination of size-exclusion chromatography (SEC) and intrinsic viscosity studies. Two-electron oxidation of 2-V with nitrous oxide (N 2 O) cleanly yields a [V V ] alkylidene-alkynyl oxo complex [(BDI)V(=O){κ 1 - C -(=C(SiMe 3 )CC(SiMe 3 ))}] ( 3 ), which lends support for how this scaffold in 2-M might be operating in the polymerization of the terminal alkyne. This work demonstrates how alkylidynes can be circumvented using 1,3-dianionic allene as a segue into M−C multiple bonds.

Reported is the catalytic cyclic polymer synthesis by a 3d transition metal complex: a [VV] alkylidyne, [(dBDI)V≡CtBu(OEt2)] (1−OEt2), supported by the deprotonated β-diketiminate dBDI2− (dBDI2− = ArNC(CH3)CHC(CH2)NAr). Complex 1−OEt2 is a pre-catalyst for the polymerization of phenylacetylene to give cyclic pol-yphenylacetylene, whereas its precursor, complex [(BDI)V≡CtBu(OTf)] (2−OTf; BDI− = [ArNC(CH3)]2CH, Ar = 2,6-iPr2C6H3) and the zwitterion [((C6F5)3B−dBDI)V≡CtBu(OEt2)] (3−OEt2) exhibit low catalyst activity despite having the same alkyli-dyne ligand. Cyclic polymer topologies were verified by size-exclusion chromatography (SEC) and intrinsic viscosity studies. A component of the mechanism of the cyclic polymerization reaction was probed by isolation and full character-ization of 4- and 6-membered metallacycles as model intermediates. Metallacyclobutadiene (MCBD) and deprotio-metallacyclobutadiene (dMCBD) complexes, (dBDI)V[C(tBu)C(H)C(tBu)] (4−tBu) and (BDI)V[C(tBu)CC(Mes)] (5−Mes), respectively, were synthesized upon reaction with bulkier alkynes, tBu− and Mes−acetylene, with 1−OEt2. Furthermore, the reaction of the conjugate acid of 1−OEt2, (BDI)V≡CtBu(OTf) (2−OTf), with the conjugated base of phenylacetylene, LiC≡CPh, yields the doubly deprotio-metallabenzene complex, [Li(THF)4]{(BDI)V[C(Ph)CC(tBu)CC(Ph)]} (6). Protonation of the anionic 6-membered metallacycle 6, yields 6−H+, a catalytically active species towards the polymerization of phe-nylacetylene, for which the polymers were also confirmed to be cyclic by SEC studies. Computational mechanistic stud-ies complement the experimental observations and provide insight into the mechanism of cyclic polymer growth. The non-innocence of the supporting dBDI2− ligand and its role in proton shuttling to generate deprotio-metallacyclobutadiene (dMCBD) complexes that proposedly culminate in the formation of catalytically active [VIII] species is also discussed. This work demonstrates how a dMCBD moiety can react with terminal alkynes to form cyclic polymers.

We introduce a simplified synthesis of thick, flexible, cyclic polyacetylene films (c-PA) and study the relationship between stretchability and electrical conductivity of c-PA. Stretching the films 1.6 times their original length increases conductivity 5-fold.

An OCO-pincer supported tungsten(VI) alkylidyne exhibits diverse reactivity depending on the identity of the oxidizing agent and the stoichiometry of the reaction. Oxidation reactions are studied with azo, nitroso, and oxo compounds. Benzo(c)cinnoline facilitates migratory insertion of the alkylidyne carbon in the backbone forming a tethered tungsten (VI) alkylidene complex. Analogous azobenzene activates a CC bond in the tert—butyl group of the alkylidyne and results in a tungsten di-imido complex. Nitrosobenzene and pyridine N-oxide undergo oxygen atom transfer (OAT) reactions and result in tungsten oxo complexes. Reactions with nitrosobenzene are sensitive to stoichiometry; CC bond activation is observed in stoichiometric reactions, while only OAT occurs with excess nitrosobenzene.

Cyclic polymers exhibit different solution and bulk properties compared to their linear analogs of the same molecular weight, such as smaller hydrodynamic volumes and higher glass transition temperatures (Tg). Polymers having boron-centered Lewis acids as pendent groups have utility in sensors, biomaterials, and dynamic covalent materials. Conventional and controlled radical polymerization are the most common routes to synthesize polymers with pendent boronate ester and boronic acid functional groups. Herein, we expand the synthetic repertoire available for their synthesis by reporting the preparation of cyclic poly(4-ethynylphenylboronate ester) (c-PEPB) by ring-expansion polymerization (REP) of 4-ethynylphenylboronate ester using a pincersupported tethered tetra-anionic tungsten alkylidene complex. The polymers were successfully characterized and compared to their linear analogs using light scattering measurements, solution viscometry, and thermal analysis. In all cases, the polymer interrogation experiments reveal key differences attributed to the cyclic topology. Deprotection of the polymeric boronate esters was performed by transesterification with methylboronic acid to furnish cyclic poly(4-ethynylphenyl boronic acid) (c-PEPB-OH). The reversible reaction of boronic acids with 1,2- and 1,3-diols to form boronate esters was used to cross-link c-PEPB-OH with a polyol crosslinker to form gels from cyclic polymers.

Reactions between tungsten alkylidyne [(BuOCO)-Bu-t]W equivalent to(CBu)-Bu-t(THF)(2) 1 and sulfur containing small molecules are reported. Complex 1 reacts with CS2 to produce intermediate eta(2) bound CS2 complex [O2C((BuC)-Bu-t & boxH;)W(eta(2)-(S,C)-CS2)(THF)] 8. Heating complex 8 provides a mixture of a monomeric tungsten sulfido complex 9 and a dimeric complex 10 in a 4:1 ratio, respectively. Heating the mixture does not perturb the ratio. Addition of excess THF in a solution of 9 and 10 (4:1) converts 10 to 9 (>96%) with concomitant loss of (CS)(x). Both 9 and 10 can be selectively crystallized from the mixture. An alternative synthesis of exclusively monomeric 9 involves the reaction between 1 and PhNCS. Demonstrating ring expansion metathesis polymerization (REMP), tethered tungsten alkylidene 8 polymerizes norbornene to produce cis-selective syndiotactic cyclic polynorbornene (c-poly(NBE)).

Tethered tungsten-alkylidenes bearing azoimido ligands (M equivalent to N gamma-N beta=N alpha R) are synthesized, characterized, and tested as initiators for ring expansion metathesis polymerization (REMP). While these ligands are typically unstable and prone to dinitrogen loss, this work demonstrates that tethered alkylidene complexes bearing azoimido ligands are stable enough to be REMP initiators. Moreover, they are more efficient, long-lived, and stereoselective than their corresponding imido derivatives (M equivalent to NR). Density Functional Theory (DFT) analysis of the azoimido complexes provides insight into their unusual stability. Tethered tungsten-alkylidenes bearing azoimido ligands (M equivalent to N gamma-N beta=N alpha R), typically unstable and prone to dinitrogen loss, are stable enough to be REMP initiators, being more efficient, long-lived, and stereoselective than their corresponding imido derivatives (M equivalent to NR). DFT provides insight into their unusual stability. image

Demonstrated is the successful A2 + B2 RAFT step-growth polymerization of bis-acrylamides. The synthesized poly(acrylamides) can be degraded by simply adding excess ethanolamine or PBu3.

An easier, safer, and scalable approach to the synthesis of a trianionic pincer ligand and its use in the preparation of the Mo cyclic polymer catalyst [O2C((p-OMe-C6H4)C=)Mo(eta(2)-CH (CBu)-Bu-t)(THF)] (7) are reported. The synthesis of the [(BuOCO)-Bu-t]Me-2 (1) ligand is simplified to a reaction that allows scaling up, thus reducing the main barrier to accessing cyclic polymer catalysts. The synthesis allows for the derivatization of the C-ipso carbon of the central ring of the pincer. Taking advantage of this, a deuterium atom was substituted for kinetic isotope measurements. Complex 7 was tested for activity in the polymerization of phenylacetylene. Confirmation of the cyclic polymer topology comes from gel permeation chromatography (GPC), dynamic light scattering (DLS), and intrinsic viscosity (eta) measurements.

The synthesis, characterization, and preliminary activity of an unprecedented tethered alkylidyne tungsten complex for ring expansion alkyne metathesis polymerization (REAMP) are reported. The tethered alkylidyne 7 is generated rapidly by combining alkylidyne W(CtBu)(CH2tBu)(O-2,6-i-Pr2C6H3)2 (6) with 1 equiv of an yne-ol proligand (5). Characterized by NMR studies and nuclear Overhauser effect spectroscopy, complex 7 is a dimer. Each metal center contains a tungsten-carbon triple bond tethered to the metal center via an alkoxide ligand. The polymerization of the strained cycloalkyne 3,8-didodecyloxy-5,6-dihydro-11,12-didehydrodibenzo[a,e]-[8]annulene, 8, to generate cyclic polymers was demonstrated. Size exclusion chromatography (SEC) and intrinsic viscosity (η) measurements confirm the polymer's cyclic topology.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Reactions between imines and tungsten alkylidyne complexes are studied. The trianionic pincer ligand supported alkylidyne [tBuOCO]WCC(CH3)3(THF)2 (1) reacts with N-(R)-1-phenylmethanimine (PMI-R, R = Me, Ph, Bn, and TMS) yielding [tBuOC(H)O]W(eta 2-tBuC0000000000000000000000000000000000000000000000000000111111111111111000000000000000000011111111111111100000000000000000001111111111111110000000000000000000000000000000000000000000000000000CPh)N(R) (4-R), products from metathesis reaction. In contrast, the non-pincer alkylidyne (tBuO)3WCC(CH3)3 does not react with PMI-R imines. Reactions between imines and tungsten alkylidyne complexes are studied.

The reaction of Ph3PAuN3 with 9-Ph-9-borafluorene resulted in complexation of the azide to boron while a gold acetylide reacted with 9-Ph-9-borafluorene to insert the acetylide carbon to access a six-membered boracycle with an exocyclic double bond.