Bridging polymer architecture, printability, and properties by digital light processing of block copolycarbonates.

CO-based aliphatic polycarbonates (aPCs), produced through the alternating copolymerization of epoxides with CO, present an appealing option for sustainable polymeric materials owing to their renewable feedstock and degradable characteristics. An ongoing challenge in working with aPCs is modifying their mechanical properties to meet specific demands. Herein, we report that monomer ratio and polymer architecture of aPCs impact not only printability by digital light processing (DLP) additive manufacturing, but also dictate the thermomechanical and degradation properties of the printed objects.

Bond Trading: Intramolecular Metal and Ligand Exchange within a NO/Ni/Co Complex.

With the goal of generating hetero-redox levels on metals as well as on nitric oxide (NO), metallodithiolate (N S )Co (NO ), N S = N,N- dibenzyl-3,7-diazanonane-1,9-dithiolate, is introduced as ligand to a well-characterized labile [Ni (NO) ] synthon. The reaction between [Ni (NO )] and [Co (NO )] has led to a remarkable electronic and ligand redistribution to form a heterobimetallic dinitrosyl cobalt [(N S )Ni ∙Co(NO) ] complex with formal two electron oxidation state switches concomitant with the nickel extraction or transfer as Ni into the N S ligand binding site. To date, this is the first reported heterobimetallic cobalt dinitrosyl complex.

Micellar catalysis: Polymer bound palladium catalyst for carbon-carbon coupling reactions in water.

Metallosurfactants, defined here as hydrophobic metal-containing groups embedded in hydrophilic units when dispersed in water, emanate in the formation of metallomicelles. This approach continues to attract great interest for its ability to serve as micellar catalysts for various metal-mediated chemical transformations in water. Indeed, relevant to green chemistry, micellar catalysis plays a preeminent function as a replacement for organic solvents in a variety of chemical reactions.

Structural Metamorphoses of d-Xylose Oxetane- and Carbonyl Sulfide-Based Polymers during Ring-Opening Copolymerizations.

Polymers constructed from copolymerizations of carbohydrates with C1 feedstocks are promising targets that provide transformation of sustainably sourced building blocks into next-generation, environmentally degradable plastic materials. In this work, the initial intention was to expand beyond polycarbonates prepared by the copolymerization of oxetanes derived from d-xylose with CO and incorporate sulfur atoms through the establishment of monothiocarbonates that would provide the ability to modulate the backbone compositions and result in unique effects upon the chemical, physical, and mechanical properties. Therefore, the syntheses of poly(1,2--isopropylidene-α-d-xylofuranose monothiocarbonate)s were investigated by ring-opening copolymerizations of 3,5-anhydro-1,2--isopropylidene-α-d-xylofuranose with carbonyl sulfide (COS) facilitated by (salen)CrCl/cocatalyst systems.

Enabling New Approaches: Recent Advances in Processing Aliphatic Polycarbonate-Based Materials.

Aliphatic polycarbonates (aPCs) have become increasingly popular as functional materials due to their biocompatibility and capacity for on-demand degradation. Advances in polymerization techniques and the introduction of new functional monomers have expanded the library of aPCs available, offering a diverse range of chemical compositions and structures. To accommodate the emerging requirements of new applications in biomedical and energy-related fields, various manufacturing techniques have been adopted for processing aPC-based materials.

Bifunctional organoboron-phosphonium catalysts for coupling reactions of CO and epoxides.

Recent years have witnessed intensive research activity in exploring novel metal-free organocatalysts for catalyzing the coupling reactions of CO and epoxides to afford cyclic or polymeric carbonates. In this direction, herein we report a series of boron-phosphonium organocatalysts for catalyzing the coupling reactions of CO and epoxides. These organophosphonium catalysts were synthesized in high yields by following a two step protocol involving Menschutkin and hydroboration reactions in succession.

Chirality-Guided Isomerization of MnS Diamond Core Complexes: A Mechanistic Study.

Occasioned by the discovery of a ligand transfer from M(NS) to Mn in Mn(CO)Br, the resulting HNS ligand-tethered dimanganese complex, (μ-,'-ethylenebis(mercaptoacetamide))[Mn(CO)], was found to have myriad analogues of the type (μ-S-E)[Mn(CO)], making up an under-studied class containing MnS rhombs. The attempt to synthesize a nontethered version resulted in a solid-state structure in an -conformation. However, a direct comparison of the Fourier-transform infrared spectra of the tethered versus nontethered complexes in combination with theoretical frequency calculation suggested the coexistence of - and -isomers and their interconversion in solution.

3D Printed CO -Based Triblock Copolymers and Post-Printing Modification.

We report the facile synthesis and 3D printing of a series of triblock copolymers consisting of soft and hard blocks and demonstrate that alkene pendant groups of the hard block can be covalently modified. The polymers are prepared using a salenCo(III)TFA/PPNTFA binary catalyst system and 1,2-propanediol as a chain transfer agent, providing an efficient one-pot, two-step strategy to tailor polymer thermal and mechanical properties. Thixotropic inks suitable for direct ink write printing were formulated by dissolving the block copolymers in organic solvent and dispersing NaCl particles.

Amphiphilic Polycarbonate Micellar Rhenium Catalysts for Efficient Photocatalytic CO Reduction in Aqueous Media.

A triblock amphiphilic polymer derived from the copolymerization of CO and epoxides containing a bipyridine rhenium complex in its backbone is shown to effectively catalyze the visible-light-driven reduction of CO to CO. This polymer provides uniformly spherical micelles in aqueous solution, where the metal catalyst is sequestered in the hydrophobic portion of the nanostructured micelle. CO to CO reduction occurs in an efficient visible-light-driven process in aqueous media with turnover numbers up to 110 (>99 % selectivity) in the absence of a photosensitizer, which is a 37-fold enhancement over the corresponding molecular rhenium catalyst in organic solvent.

Kinetic and Computational Analysis of CO Substitution in a Dinuclear Osmium Carbonyl Complex: Intersection between Dissociative and Dissociative-Interchange Mechanisms.

The mechanism for the CO substitution reaction involving the diosmium carbonyl sawhorse complex Os(μ-OCH)(CO), which contains an Os-Os single bond, two axial CO ligands, and four equatorial CO ligands, was investigated experimentally and theoretically. Kinetic measurements show CO axial substitution proceeding by a dissociative reaction that is first-order in the complex and zero-order in CO but with an unexpectedly negative entropy of activation. The corresponding electronic structure calculations yield an enthalpy of activation for axial CO dissociation that is much larger than that determined by the kinetic experiments, but in agreement with the complex's stability with respect to CO loss.

TEMPO Containing Radical Polymonothiocarbonate Polymers with Regio- and Stereo-Regularities: Synthesis, Characterization, and Electrical Conductivity Studies.

We report the synthesis of a (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl) (TEMPO) appended polymonothiocarbonates through the ring-opening copolymerization of (4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl) (GTEMPO) in the presence of carbonyl sulfide under ambient conditions. We have prepared the atactic and isotactic versions of this polymer, using enantiopure R or S forms of the GTEMPO monomer in the latter instances. Cyclic voltammetry studies revealed both oxidation and reduction events that were characteristic of TEMPO radicals.

Randomly Distributed Sulfur Atoms in the Main Chains of CO -Based Polycarbonates: Enhanced Optical Properties.

Polymeric materials possessing both high refractive indices and high Abbe numbers are much in demand for the development of advanced optical devices. However, the synthesis of such functional materials is a challenge because of the trade-off between these two properties. Herein, a synthetic strategy is presented for enhancing the optical properties of CO -based polycarbonates by modifying the polymer's topological structure.

Zwitterionic Alternating Polymerization to Generate Semicrystalline and Recyclable Cyclic Polythiourethanes.

Synthesis of cyclic, semicrystalline, and recyclable polythiourethanes was realized via the catalyst-free zwitterionic alternating copolymerization of -alkyl aziridines with carbonyl sulfide (COS) under mild conditions. The copolymerization proceeded efficiently at room temperature and generated copolymers with fully alternating linkages in more than 99% selectivity in 5 min under solvent-free conditions. Notably, the copolymers are typical semicrystalline thermoplastics with melting temperatures up to 137 °C (-butyl-substituted) or 170 °C (ethyl-substituted).

Synthetic Metallodithiolato Ligands as Pendant Bases in [FeFe], [Fe[Fe(NO)]], and [(μ-H)FeFe] Complexes.

The development of ligands with specific stereo- and electrochemical requirements that are necessary for catalyst design challenges synthetic chemists in academia and industry. The crucial aza-dithiolate linker in the active site of [FeFe]-Hase has inspired the development of synthetic analogues that utilize ligands which serve as conventional σ donors with pendant base features for H binding and delivery. Several MNS complexes (M = Ni, [Fe(NO)], [Co(NO)], etc.

Metal-Templated, Tight Loop Conformation of a Cys-X-Cys Biomimetic Assembles a Dimanganese Complex.

With the goal of generating anionic analogues to MN S ⋅Mn(CO) Br we introduced metallodithiolate ligands, MN S prepared from the Cys-X-Cys biomimetic, ema ligand (ema=N,N'-ethylenebis(mercaptoacetamide); M=Ni , [V ≡O] and Fe ) to Mn(CO) Br. An unexpected, remarkably stable dimanganese product, (H N (CH C=O(μ-S)) )[Mn(CO) ] resulted from loss of M originally residing in the N S pocket, replaced by protonation at the amido nitrogens, generating H ema . Accordingly, the ema ligand has switched its coordination mode from an N S cavity holding a single metal, to a binucleating H ema with bridging sulfurs and carboxamide oxygens within Mn-μ-S-CH -C-O, 5-membered rings.

Cyanide Docking and Linkage Isomerism in Models for the Artificial [FeFe]-Hydrogenase Maturation Process.

Linkage isomerization of the cyanide on the [2Fe] subsite of the [FeFe]-Hase active site was reported to occur during the docking of various synthetic diiron complexes onto a carrier protein, apo-HydF, as the initial step for the artificial maturation of the [FeFe]-Hase enzyme (Berggren et al., Nature, 2013, 499, 66-70). An investigation of our triiron organometallic models (FeFe-CN/NC-Fe') revealed that, once a Fe-CN-Fe connection is formed, high barriers prevent such cyanide linkage isomerization ( Chem.

Perfectly Alternating and Regioselective Copolymerization of Carbonyl Sulfide and Epoxides by Metal-Free Lewis Pairs.

The preparation of perfectly alternating and regioslective copolymers derived from the copolymerization of carbonyl sulfide (COS) and epoxides by metal-free Lewis pair catalysts composed of a Lewis base (amidine, guanidine, or quaternary onium salts) and a Lewis acid (triethyl borane) is described. Colorless and highly transparent copolymers of poly(monothiocarbonate) were successfully obtained with over 99 % tail-to-head content and high molecular weight (up to 92.5 kg mol ).

Directed Self-Assembly of Polystyrene-b-poly(propylene carbonate) on Chemical Patterns via Thermal Annealing for Next Generation Lithography.

Directed self-assembly (DSA) of block copolymers (BCPs) combines advantages of conventional photolithography and polymeric materials and shows competence in semiconductors and data storage applications. Driven by the more integrated, much smaller and higher performance of the electronics, however, the industry standard polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) in DSA strategy cannot meet the rapid development of lithography technology because its intrinsic limited Flory-Huggins interaction parameter (χ). Despite hundreds of block copolymers have been developed, these BCPs systems are usually subject to a trade-off between high χ and thermal treatment, resulting in incompatibility with the current nanomanufacturing fab processes.

Poly(monothiocarbonate)s from the Alternating and Regioselective Copolymerization of Carbonyl Sulfide with Epoxides.

Carbonyl sulfide (COS) is an air pollutant that causes acid rain, ozonosphere damage, and carbon dioxide (CO) generation. It is a heterocumulene and structural analogue of CO. Relevant to organic synthesis, it is a source of C═O or C═S groups and thus an ideal one-carbon (C1) building block for synthesizing sulfur-containing polymers through the similar route of CO copolymerization.

Environmentally Benign CO2-Based Copolymers: Degradable Polycarbonates Derived from Dihydroxybutyric Acid and Their Platinum-Polymer Conjugates.

(S)-3,4-Dihydroxybutyric acid ((S)-3,4-DHBA), an endogenous straight chain fatty acid, is a normal human urinary metabolite and can be obtained as a valuable chiral biomass for synthesizing statin-class drugs. Hence, its epoxide derivatives should serve as promising monomers for producing biocompatible polymers via alternating copolymerization with carbon dioxide. In this report, we demonstrate the production of poly(tert-butyl 3,4-dihydroxybutanoate carbonate) from racemic-tert-butyl 3,4-epoxybutanoate (rac-(t)Bu 3,4-EB) and CO2 using bifunctional cobalt(III) salen catalysts.

Construction of Versatile and Functional Nanostructures Derived from CO2 -based Polycarbonates.

The construction of amphiphilic polycarbonates through epoxides/CO2 coupling is a challenging aim to provide more diverse CO2 -based functional materials. In this report, we demonstrate the facile preparation of diverse and functional nanoparticles derived from a CO2 -based triblock polycarbonate system. By the judicious use of water as chain-transfer reagent in the propylene oxide/CO2 polymerization, poly(propylene carbonate (PPC) diols are successfully produced and serve as macroinitiators in the subsequent allyl glycidyl ether/CO2 coupling reaction.

Thermal and photochemical reactivity of manganese tricarbonyl and tetracarbonyl complexes with a bulky diazabutadiene ligand.

The manganese tricarbonyl complex fac-Mn(Br)(CO)3((i)Pr2Ph-DAB) (1) [(i)Pr2Ph-DAB = (N,N'-bis(2,6-di-isopropylphenyl)-1,4-diaza-1,3-butadiene)] was synthesized from the reaction of Mn(CO)5Br with the sterically encumbered DAB ligand. Compound 1 exhibits rapid CO release under low power visible light irradiation (560 nm) suggesting its possible use as a photoCORM. The reaction of compound 1 with TlPF6 in the dark afforded the manganese(I) tetracarbonyl complex, [Mn(CO)4((i)Pr2Ph-DAB)][PF6] (2).

Light-enhanced displacement of methyl acrylate from iron carbonyl: investigation of the reactive intermediate via rapid-scan Fourier transform infrared and computational studies.

The thermal displacement of methyl acrylate from Fe(CO)4(η(2)-CH2=CHCOOMe) by phosphine ligands is a relatively slow reaction requiring several hours at elevated temperatures. In the present study, it is observed that photolysis of the tetracarbonyl complex with UV light activates the process such that the reaction is complete within a few seconds. This rate enhancement is due to the formation of an intermediate η(4) complex where the organic C=O and C=C units of methyl acrylate occupy axial and equatorial coordination sites on the Fe center, respectively, following photochemical CO loss.

Construction of ultrastable porphyrin Zr metal-organic frameworks through linker elimination.

A series of highly stable MOFs with 3-D nanochannels, namely PCN-224 (no metal, Ni, Co, Fe), have been assembled with six-connected Zr6 cluster and metalloporphyrins by a linker-elimination strategy. The PCN-224 series not only exhibits the highest BET surface area (2600 m(2)/g) among all the reported porphyrinic MOFs but also remains intact in pH = 0 to pH = 11 aqueous solution. Remarkably, PCN-224(Co) exhibits high catalytic activity for the CO2/propylene oxide coupling reaction and can be used as a recoverable heterogeneous catalyst.