Invited for the cover of this issue is the group of Vicente del Amo, Alejandro Presa Soto and Joaquín García-Álvarez (QuimSinSos Group) at the University of Oviedo. The image depicts the use of the Fe -based deep eutectic mixture [FeCl ⋅6 H O/Gly (3:1)] (Gly = glycerol) as both promoter and solvent for the straightforward and selective hydration of alkynes, working under mild (45 °C), bench-type reaction conditions (air) and in the absence of ligands, co-catalysts or co-solvents. Read the full text of the article at 10.
View Article and Find Full Text PDFAn efficient, simple and general protocol for the selective hydration of terminal alkynes into the corresponding methyl ketones has been developed by using a cheap, easy-to-synthesise and sustainable Fe -based eutectic mixture [FeCl ⋅ 6H O/Gly (3 : 1)] as both promoter and solvent for the hydration reaction, working: i) under mild (45 °C) and bench-type reaction conditions (air); and ii) in the absence of ligands, co-catalysts, co-solvents or toxic, non-abundant and expensive noble transition metals (Au, Ru, Pd). When the final methyl ketones are solid/insoluble in the eutectic mixture, the hydration reaction takes place in 30 min, and the obtained methyl ketones can be isolated by simply decanting the liquid Fe -DES, allowing the direct isolation of the desired ketones without VOC solvents. By using this straightforward and simple isolation protocol, we have been able to recycle the Fe -based eutectic mixture system up to eight consecutive times.
View Article and Find Full Text PDFAn efficient and selective N-functionalization of amides is first reported via a CuI-catalyzed Goldberg-type C-N coupling reaction between aryl iodides and primary/secondary amides run either in Deep Eutectic Solvents (DESs) or water as sustainable reaction media, under mild and bench-type reaction conditions (absence of protecting atmosphere). Higher activities were observed in an aqueous medium, though the employment of DESs expanded and improved the scope of the reaction to include also aliphatic amides. Additional valuable features of the reported protocol include: (i) the possibility to scale up the reaction without any erosion of the yield/reaction time; (ii) the recyclability of both the catalyst and the eutectic solvent up to 4 consecutive runs; and (iii) the feasibility of the proposed catalytic system for the synthesis of biologically active molecules.
View Article and Find Full Text PDFDuring the last number of years a variety of crystallization-driven self-assembly (CDSA) processes based on semicrystalline block copolymers have been developed to prepare a number of different nanomorphologies in solution (micelles). We herein present a convenient synthetic methodology combining: (i) The anionic polymerization of 2-vinylpyridine initiated by organolithium functionalized phosphane initiators; (ii) the cationic polymerization of iminophosphoranes initiated by -PRCl; and (iii) a macromolecular nucleophilic substitution step, to prepare the novel block copolymers poly(bistrifluoroethoxy phosphazene)--poly(2-vinylpyridine) (PTFEP--P2VP), having semicrystalline PTFEP core forming blocks. The self-assembly of these materials in mixtures of THF (tetrahydrofuran) and 2-propanol (selective solvent to P2VP), lead to a variety of cylindrical micelles of different lengths depending on the amount of 2-propanol added.
View Article and Find Full Text PDFThe direct chemical functionalization of poly(spirophosphazene) [NP(O C H )] (1) can be performed by the lithiation of the aromatic rings at low temperature using Schlosser's base (Li Bu/KO Bu or "superbase"), and the subsequent reaction with various electrophiles such as ClSiMe , ClPPh , or MeOB(O C H ) (MeOBpin). The functionalized polymers, isolated in very high yields (>90%) and without degradation of the polymeric chains, have an average degree of substitution per repeat unit ranging from 0.3 (random copolymers) to a maximum of 1.
View Article and Find Full Text PDFWe herein report the formation of two complex nanostructures, toroidal micelles and bicontinuous nanospheres, by the self-assembly of the single structurally simple crystalline-b-coil diblock copolymer poly[bis(trifluoroethoxy)phosphazene]-b-poly(styrene), PTFEP-b-PS, in one solvent (THF) and without additives. The nature of these nanostructures in solution was confirmed by DLS and cryo-TEM experiments. The two morphologies are related by means of a new type of reversible morphological evolution, bicontinuous-to-toroidal, triggered by changes in the polymer concentration.
View Article and Find Full Text PDFThe self-assembly in thin films of polyphosphazene block copolymers [N = P(O2C12H8)]n-b-[N = PMePh]m (O2C12H8 = 2,2'-dioxy-1,1'-biphenyl; : n = 50, m = 35; : n = 20, m = 70, and : n = 245, m = 60), having different volume fractions of the rigid [N = P(O2C12H8)]n block, has been studied. BCP spontaneously self-assembled into well-defined round-shaped macroporous films, observing also, as a minor morphology, spherical vesicles in regions where the film was not formed. A detailed study by SEM, TEM and AFM of the structure of the vesicles, the morphology of the pores (inverted mushroom-shaped), and the behaviour of the copolymers with shorter () and longer () [N = P(O2C12H8)]n rigid blocks provided sufficient experimental evidence to propose a vesicle-to-pore morphological evolution as the most likely mechanism to explain the pore formation during the self-assembly of .
View Article and Find Full Text PDFThe preparation of long-term-stable giant unilamellar vesicles (GUVs, diameter ≥ 1000 nm) and large vesicles (diameter ≥ 500 nm) by self-assembly in THF of the crystalline-b-coil polyphosphazene block copolymers [N=P(OCH2CF3)2 ]n-b-[N=PMePh]m (4 a: n=30, m=20; 4 b: n=90, m=20; 4 c: n=200, m=85), which combine crystalline [N=P(OCH2CF3)2] and amorphous [N=PMePh] blocks, both of which are flexible, is reported. SEM, TEM, and wide-angle X-ray scattering experiments demonstrated that the stability of these GUVs is induced by crystallization of the [N=P(OCH2CF3)2] blocks at the capsule wall of the GUVS, with the [N=PMePh] blocks at the corona. Higher degrees of crystallinity of the capsule wall are found in the bigger vesicles, which suggests that the crystallinity of the [N=P(OCH2CF3)2] block facilitates the formation of large vesicles.
View Article and Find Full Text PDFA random phosphazene copolymer {[N = P((CH2)7-Br)Ph]0.5[N = PMePh]0.5}n (2) and a block copolyphosphazene {[N = P((CH2)7-Br)Ph]0.
View Article and Find Full Text PDFNew advances into the chirality effect in the self-assembly of block copolymers (BCPs) have been achieved by tuning the helicity of the chiral-core-forming blocks. The chiral BCPs {[N=P(R)-O2C20H12](200-x)[N=P(OC5H4N)2](x)}-b-[N=PMePh]50 ((R)-O2C20H12 = (R)-1,1'-binaphthyl-2,2'-dioxy, OC5H4N = 4-pyridinoxy (OPy); x = 10, 30, 60, 100 for 3 a-d, respectively), in which the [N=P(OPy)2] units are randomly distributed within the chiral block, have been synthesised. The chiroptical properties of the BCPs ([α]D vs.
View Article and Find Full Text PDFWe describe a new and very versatile method to place chosen chemical functionalities at the edge of the pores of macroporous materials. The method is based on the synthesis and self-assembly of inorganic block copolymers (BCPs) having chiral rigid segments bearing controllable quantities of randomly distributed functional groups. The synthesis of a series of optically active block copolyphosphazenes (PP) with the general formula [N=P(R-O2C20H12)(0.
View Article and Find Full Text PDFA series of optically active helical polyphosphazene block copolymers of general formula R-[N=P(O2C20H12)]n-b-[N=PMePh]m (R-7 a-c) was synthesized and characterized. The polymers were prepared by sequential living cationic polycondensation of N-silylphosphoranimines using the mono-end-capped initiator [Ph3 P=N=PCl3][PCl6] (5) and exhibit a low polydispersity index (ca. 1.
View Article and Find Full Text PDFThe counteranion associated with the cationic initiator [Cl(3)P═N═PCl(3)](+) ([4](+)) generated during the PCl(5)-initiated living, cationic chain growth polycondensation of the N-silylphosphoranimine Cl(3)P═NSiMe(3) (3) to give poly(dichlorophosphazene), [N═PCl(2)](n) (2), has been found to have a dramatic effect on the polymerization. When the counteranion of [4](+) was changed from PCl(6)(-) or Cl(-) to the weakly coordinating anions [BAr*(F)(4)](-) and [BAr(F)(4)](-) (Ar*(F) = 3,5-{CF(3)}(2)C(6)H(3), Ar(F) = C(6)F(5)) instead of the polymerization of 3 being complete in 4-6 h, no reaction was observed after 24 h. Remarkably, the polymerization of 3 may be initiated by Cl(-) anions even in the absence of an active cation such as [4](+).
View Article and Find Full Text PDFThe metallation of the cyclopentadienyl (Cp) ligands of poly(ferrocenyldimethylsilane) (PFDMS) can be performed by reaction with the Schlosser's base pair t-BuLi/KOt-Bu in THF. Subsequent treatment with a series of electrophiles affords a range of Cp-substituted polymers with up to an average of 1.8 new substituents per repeating unit.
View Article and Find Full Text PDFThis Perspective discusses the development of new routes to polyphosphazenes, [R(2)P[double bond, length as m-dash]N](n), that occur at ambient temperature and, in some cases, allow molecular weight control and access to narrow molecular weight distributions and block copolymers. For example, the room temperature silyl-carborane initiated ring-opening polymerisation of (NPCl(2))(3) is described together with chain growth condensation polymerisations of phosphoranimines Cl(3)P[double bond, length as m-dash]NSiMe(3) and BrMePhP[double bond, length as m-dash]NSiMe(3). Recent works on donor-stabilised cationic phosphoranimines are also discussed.
View Article and Find Full Text PDFA simple and convenient one-pot synthesis of THF solutions of high molecular weight poly(dichlorophosphazene) [NPCl(2)](n), or the (15)N isotopomer [(15)NPCl(2)](n), starting directly from PCl(5) and NH(4)Cl or (15)NH(4)Cl in a solution of 1,2,4-trichlorobenzene in the presence of sulfamic acid and calcium sulfate dihydrate, is described. The solutions of [NPCl(2)](n) in THF, which are obtained free of poly(tetrahydrofuran) by preparing them in the presence of K(2)CO(3), can be reacted directly with phenols, biphenols, or even HO-CH(2)CF(3) in the presence of K(2)CO(3) or Cs(2)CO(3) to obtain, after a very simple workup, the corresponding polyphosphazene derivatives almost free of chlorine.
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