Travels with Alex: Music for viola obbligato and various ensembles

Travels with Alex is a cycle of nine pieces for viola obbligato and various combinations drawn from an ensemble of 24 musicians (including two performers on Tibetan instruments). Ideally these compositions are to be played as a complete cycle, given the use of a large-scale durational interval succession to derive the relative durations of the individual pieces and sections within them. However, performance individually or in smaller combinations is also possible. The initial inspirations were twofold: the gift to the composer of a Tibetan thangka, and the travel writings of the French Buddhist, Alexandra David-Néel (1868-1969). Musically speaking, the cycle explores a range of methods, serial and otherwise, for ‘composing out’ from small, modal, mantric motifs. In Buddhist traditions, these and others like them have been used to invoke the presence of a particular bodhisattva (a ‘patron deity’, or mythical being, committed to guiding humanity towards Enlightenment) — in this case, Tārā or Jetsun Dölma, amongst whose attributes devotees prize her protection of travellers. The supporting commentary explains how these micro-elements are used to build a musical structure lasting around an hour. The commentary credits a compositional lineage featuring particular works of Tōru Takemitsu, Karlheinz Stockhausen, Peter Maxwell Davies and Jonathan Harvey. Specific technical indebtedness is also ascribed to other twentieth-century figures such as Igor Stravinsky, Michael Tippett, Elliott Carter, Witold Lutosławski, Luciano Berio and Pierre Boulez. Amongst the original features of the cycle is the juxtaposition of typical Western orchestral instruments with instruments used in Tibetan Buddhist ritual practices (played in the recording by Tibetan monks) and the inclusion of poetry in French inspired by David-Néel’s writings. The latter appears in two of the nine pieces, involving the addition of a countertenor to the instrumental ensemble

Effects of coating spherical iron oxide nanoparticles

International audienceWe investigate the effect of several coatings applied in biomedical applications to iron oxide nanoparticles on the size, structure and composition of the particles. The four structural techniques employed – TEM, DLS, VSM, SAXS and EXAFS – show no significant effects of the coatings on the spherical shape of the bare nanoparticles, the average sizes or the local order around the Fe atoms. The NPs coated with hydroxylmethylene bisphosphonate or catechol have a lower proportion of magnetite than the bare and citrated ones, raising the question whether the former are responsible for increasing the valence state of the oxide on the NP surfaces and lowering the overall proportion of magnetite in the particles. VSM measurements show that these two coatings lead to a slightly higher saturation magnetization than the citrate

Phosphasalen group IV metal complexes: synthesis, characterization and ring opening polymerization of lactide

International audienceWe report the synthesis of a series of Zr and Ti complexes bearing phosphasalen which differs from salen by the incorporation of two P atoms in the ligand backbone. The reaction of phosphasalen proligands (1a-1c)H2 with Zr(CH2Ph)4 led to different products depending on the nature of the N,N-linker in the ligand. In case of ethylene-linked phosphasalen, octahedral Zr complex 2a formed as a single stereoisomer in trans geometry. With the phenylene linker, it was shown by dynamic NMR spectroscopy that complex 2b exists as a mixture of trans and cis-β isomers in solution, both enantiomers (Δ and Λ) of the cis-β isomer being in fast equilibrium with respect to the NMR timescale. The use of a propylene-linked phosphasalen proligand 1cH2 led to a mixture of complexes among which a binuclear Zr complex 2c bridged only by one phosphasalen ligand could be isolated and characterized. Addition of 2 equiv of i PrOH to 2a and 2b afforded diisoproxy Zr complexes 3a and 3b as a mixture of trans and cis-β isomers, the latter undergoing fast Δ/Λ isomerization in solution. Addition of B(C6F5)3 to 2a and 2b gave cationic monobenzyl Zr complexes 4a and 4b which have been further converted into cationic alkoxy Zr complexes 5a-b and 6a-b by alcoholysis with i PrOH and (S)-methyl-lactate, respectively. The reaction of the phosphasalen proligands with Ti(NMe2)4 proceeded diastereoselectively giving rise to Ti complexes 7a-c in octahedral geometry with cis-β wrapping of the ligand. The complexes have been tested for the ROP of rac-lactide. The neutral phosphasalen Ti and Zr complexes showed only poor activity probably due to the encumbered and electron donating nature of the phosphasalen ligand. In contrast, the cationic Zr alkoxides 5a, 6a and 6b are effective initiators for the controlled and hetero-selective ROP of rac-lactide

Phosphasalen group IV metal complexes: synthesis, characterization and ring opening polymerization of lactide

We report the synthesis of a series of Zr and Ti complexes bearing phosphasalen which differs from salen by the incorporation of two P atoms in the ligand backbone. The reaction of phosphasalen proligands(1a-1c)H2with Zr(CH2Ph)4led to different products depending on the nature of the N,N-linker in the ligand. In the case of ethylene-linked phosphasalen, octahedral Zr complex2aformed as a single stereoisomer intransgeometry. With the phenylene linker, it was shown by dynamic NMR spectroscopy that complex2bexists as a mixture oftransandcis-ß isomers in solution, both enantiomers (? and ?) of thecis-ß isomer being in fast equilibrium with respect to the NMR time-scale. The use of a propylene-linked phosphasalen proligand1cH2led to a mixture of complexes among which a binuclear Zr complex2cbridged only by one phosphasalen ligand could be isolated and characterized. Addition of 2 equiv. ofiPrOH to2aand2bafforded diisoproxy Zr complexes3aand3bas a mixture oftransandcis-ß isomers, the latter undergoing fast ?/? isomerization in solution. Addition of B(C6F5)3to2aand2bgave cationic monobenzyl Zr complexes4aand4bwhich have been further converted into cationic alkoxy Zr complexes5a-band6a-bby alcoholysis withiPrOH and (S)-methyl-lactate, respectively. The reaction of the phosphasalen proligands with Ti(NMe2)4proceeded diastereoselectively giving rise to Ti complexes7a-cin octahedral geometry withcis-ß wrapping of the ligand. The complexes have been tested for the ROP ofrac-lactide. The neutral phosphasalen Ti and Zr complexes showed only poor activity probably due to the encumbered and electron donating nature of the phosphasalen ligand. In contrast, the cationic Zr alkoxides5a,6aand6bare effective initiators for the controlled and hetero-selective ROP ofrac-lactide

Phenoxyamidine Zn and Al Complexes: Synthesis, Characterization, and Use in the Ring-Opening Polymerization of Lactide

International audienceHerein we report the synthesis of new ditopic ligands, which consist of a phenoxy group and N,N,N'trisubstituted amidines linked by a methylene spacer (L1-L4). Their coordination chemistry has been studied/investigated with Zn(II) and Al(III). Alkane elimination route between the phenol-amidine proligands (L1H-L4H) and Et2Zn led to dinuclear complexes [(L1-L4)ZnEt]2 (1a-4a) in which the Zn centers are chelated by phenoxyamidine ligands and bridged through the oxygen atom of the phenoxy groups. Salt metathesis reaction between two equivalents of the sodium amidine phenate L1Na and ZnCl2 led to a bis-chelate chiral spiro-complex (L12Zn) 1a'. Analogous alkane elimination route between AlMe3 and the phenol-amidine proligands L1H-L4H allowed the preparation of the mononuclear complexes [(L1-L4)AlMe2] (1b-4b). The phenoxyamidine-Al and Zn complexes have been characterized by NMR spectroscopy, elemental analysis and/or high resolution ESI-MS. The solid state structures of the proligands [L1H2][Br] and L2H as well as of six complexes have been established by single crystal X-ray diffraction analysis. Fluxional properties of the proligands L1H-L2H and of the complexes 1a and 2b have been investigated by VT NMR experiments. In the presence of an alcohol source, complexes 1a-4a and 1b-4b were used as initiators for the controlled ring-opening polymerization (ROP) of rac-lactide to afford atactic polylactic acid (PLA)