[4][5][6][7] . The majority of these studies use ensemble techniques in solution, such as electrochemistry and absorption, electron paramagnetic resonance and nuclear magnetic resonance spectroscopy. The scanning tunneling microscope (STM) has proven to be a promising tool to study reactions at the molecular level [8][9][10][11][12] , and initial experiments have been reported in which the reactive properties of metal porphyrins were studied on a surface at the single molecule level by STM in ultrahigh vacuum (UHV) [13][14][15][16][17] and under ambient conditions 18,19 .Here we report detailed STM studies of the complex redox chemistry of reactions between 10,15,R,R,porphyrin manganese(III) chloride (Mn1Cl, Fig. 2a) and different oxygen donors at a solid/liquid interface. Although the dynamic nature of the molecules at this interface complicates the use of techniques that are typically being used under UHV conditions, such as X-ray 3 Photoelectron Spectroscopy (XPS), STM can provide extremely high spatial resolution and insight into changes in the electronic properties of molecules with a liquid medium over them.These liquid conditions make the system far more comparable with processes taking place in biological systems than the UHV conditions, where solvent-mediated factors such as the diffusion and concentration of reactants are fully absent. It is in principle possible with STM to monitor single molecules at the highest detail while they are involved in multistep chemical reactions with STM, and to image and identify reactants, intermediates and products in the most direct way, i.e. by imaging. This approach allows the study of reaction dynamics in realspace and real-time, which may provide unique information about reaction mechanisms that remains hidden in ensemble measurements at the macroscopic scale. STM may reveal variations in reactivity of single molecules, the relation of these variations to molecular adsorption geometry, and cooperativity effects at the nanometre scale.An overview of the possible reaction pathways involving manganese porphyrins and oxygen, based on the literature 1-3,18,20-29 and the observations described here, is depicted in Figure 1 In a first experiment we deposited a droplet of a ~10 −5 M solution of Mn1Cl in 1-octanoic acid at the basal plane of a freshly cleaved highly oriented pyrolytic graphite (HOPG) sample under ambient conditions. Related alkyl-functionalised free base porphyrin molecules are known to form well-ordered monolayers on the same substrate 30,31 . STM revealed the 5 instantaneous self-assembly of the molecules of Mn1Cl in extended lamellar arrays, in which the porphyrin planes are adsorbed parallel to the surface and the alkyl chains interdigitated (Fig. 2B). The orientation of the lamellae and the alkyl chains with respect to the main crystallographic directions of the graphite surface is identical to that observed for the corresponding free base derivative. 30 When the surface was scanned under ambient conditions at a negative bias voltage of −800 mV and ...

Poly­(oxazolidone) is an emerging class of polyurethanes (PUs) that is easily accessible by an isocyanate-free pathway via the step-growth copolymerization of CO2-based monomers (bis­(α-alkylidene cyclic carbonate)­s) with primary diamines at room temperature. Here, we explore the scope and limitation of this process by investigating the influence of the diamine and the reaction conditions on the structure and macromolecular parameters of the polymer. Less hindered diamines (aliphatic and benzylic) provide selectively poly­(hydroxyoxazolidone)­s, whereas the bulkier ones (cycloaliphatic) furnish polymer chains bearing two types of linkages, oxo-urethane and hydroxyoxazolidone ones. The increase of the reaction temperature or the addition of DBU as a catalyst enables to accelerate the polymerizations. The quantitative polymer dehydration is also achieved by refluxing in acetic acid, providing a new class of unsaturated poly­(oxazolidone)­s composed of α-alkylidene oxazolidone linkages (for hindered polymers) or a mixture of α- and β-alkylidene oxazolidone linkages (for the less hindered ones). These unsaturated poly­(oxazolidone)­s present a high glass transition temperature (90 °C ≤ T g ≤ 130 °C) and a remarkable thermal stability (T d > 360 °C), rendering these polymers attractive for applications requiring high temperatures. This work is therefore opening an avenue to novel functional isocyanate-free PUs, with the pendant hydroxyl or olefin groups that are expected to be easily derivatized.

Self-assembled monolayers of meso-5,10,15,20-tetrakis(undecyl)porphyrin copper(II) on a graphite/1-octanoic acid interface have been studied by Scanning Tunnelling Microscopy. Four distinct polymorphs were observed, varying in their unit cell size. Arrays of unit cells of the various polymorphs seamlessly connect to each other via shared unit cell vectors. The monolayers are not commensurate, but coincident with the underlying graphite substrate. The seamless transition between the polymorphs is proposed to be the result of an adaptation of the molecular conformations in the polymorphs and at the boundaries, which is enabled by the conformational freedom of the alkyl tails of these molecules.

The installation of both oxazolidone and thiocarbonate linkages within a single polymer backbone remains elusive by simple procedures under mild conditions. In this work, we report the construction of copolymers...

Designing easily degradable polymers has become a new challenge to overcome the post-consumer plastic waste accumulation in the environment. Polycarbonates are important polymers that can be chemically recycled; however, most often, their degradation requires high temperatures and/or the use of catalysts. In this work, we report the facile chemical recycling of regioregular polycarbonates prepared by the organocatalyzed copolymerization of CO2-sourced exovinylene biscyclic carbonates (BisαCC) with diols derived from biomass. These polymers, thanks to their pending ketone groups, are rapidly (<30 min) and totally deconstructed into the parent diol and a bis­(oxazolidinone) by catalyst-free aminolysis at 25 °C. By using 3-propanolamine for the aminolysis, a hydroxy-functionalized bis­(oxazolidinone) is recovered, which can be copolymerized with BisαCC to yield a polymer alternating carbonate and oxazolidinone linkages. Importantly, the same bis­(oxazolidinone) scaffold is recovered as the main product by aminolysis of this copolymer, offering a close-loop recycling scenario for this polymer. This work illustrates that these polycarbonates are prone to facile and complete aminolysis under mild and catalyst-free conditions, but can also be exploited to prepare new building blocks for the synthesis of novel degradable polymers. The mechanism of formation of these heterocycles is studied by model reactions and rationalized by density functional theory (DFT) calculations.