Search results for " polymer"
showing 10 items of 3533 documents
Thermal- and photo-induced spin crossover in the 1D coordination polymer [Fe(4-tBupy)3][Au(CN)2]2 (4-tBupy = 4-tert-butylpyridine)
2021
Reaction of the unidentate pyridine ligand containing a bulky t-butyl substituent with Fe2+ and [Au(CN)2]− affords a new type of spin crossover (SCO) coordination polymer in the 1D compound [Fe(4-tBupy)3][Au(CN)2]2⋅0.5H2O (1), which is formed by chains of Fe(II) complexes linked through bridging [Au(CN)2]− with three terminal 4-tBupy and one monodentate [Au(CN)2]− ligands completing the octahedral coordination around Fe(II). Longer reaction times led to the minor products [Fe(4-tBupy)2][Au(CN)2]2 (2), which presents a 2D structure more similar to that found in the other SCO compounds based on [Au(CN)2]−, and the 1D compound [Fe(4-tBupy)2(MeOH)][Au(CN)2]2 (3), in which one of the three termi…
pKa at Quartz/Electrolyte Interfaces.
2016
Acidity of silanol sites at the crystalline quartz/aqueous electrolyte (NaCl, NaI, KCl) interfaces are calculated from ab initio molecular dynamics simulations. pKa’s are found to follow a combination of the cationic and anionic Hofmeister series in the order pKa(neat solution) < pKa(NaCl) < pKa(NaI) < pKa(KCl), in agreement with experimental measurements. Rationalization of this ranking is achieved in terms of the microscopic local solvation of the protonated silanols and their conjugated bases, the silanolates SiO–. The change in the pKa is the result of both water destructuring by alkali halides, as well as of the specific cation/SiO– interaction, depending on the electrolyte. M…
Phosphasalen group IV metal complexes: synthesis, characterization and ring opening polymerization of lactide.
2020
International audience; 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)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 tim…
Cooperative N–H bond activation by amido-Ge(ii) cations
2020
N-heterocyclic carbene (NHC) and tertiary phosphine-stabilized germylium-ylidene cations, [R(L)Ge:]+, featuring tethered amido substituents at R have been synthesized via halide abstraction. Characterization in the solid state by X-ray crystallography shows these systems to be monomeric, featuring a two-coordinate C,N- or P,N-ligated germanium atom. The presence of the strongly Lewis acidic cationic germanium centre and proximal amide function allows for facile cleavage of N-H bonds in 1,2-fashion: the products resulting from reactions with carbazole feature a tethered secondary amine donor bound to a three-coordinate carbazolyl-GeII centre. In each case, addition of the components of the N…
Syntheses, Properties and Structures of [{(C 5 Me 5 ) 2 Nb} 2 NiTe 4 ] and [( t BuC 5 H 4 Nb) 2 Ni 5 Te 7 (Ph 2 PCH 2 PPh 2 ) 2 ]: The Quest for Tetr…
2007
The reaction of [Ni(COD) 2 ] with [Cp* 2 NbTe 2 H] (1; Cp * = η-C 5 Me 5 ) in the presence of Ph 2 PCH 2 PPh 2 (dppm) in boiling toluene gives black-violet [(Cp * 2 Nb) 2 NiTe 4 ] (3). If [Cp' 2 NbTe 2 H] (2; Cp' = tBuC 5 H 4 ) is used under similar conditions dark-brown [(Cp'Nb)2Ni5Te7(dppm)2] (4) is formed. The structures of 3 and 4 have been determined crystallographically. Complex 3 contains a severely distorted NiTe 4 tetrahedron to which two niobocene groups are coordinated. Density functional analysis of the electronic structure of the NiTe 4 building block shows that it is best described as an [Ni(η 2 -Te 2 ) 2 ] 2- fragment. The structure of 4 reveals the presence of two Ni 5 and T…
A Cationic Oligomer as an Organic Template for Direct Synthesis of Aluminosilicate ITH Zeolite
2020
There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet-like crystal morphology, large surface area, fully four-coordinated Al species, and abundant acidic sites. Methanol-to-propylene (MTP) tests reveal that the Al-ITH zeo…
Two bimetallic layered materials with “Cu4Fe3” defective cubane units: syntheses, structures and magnetic properties of {[CuII(tn)]2[FeII(CN)6]}3·[Na…
2005
Abstract Reactions of the [Fe III (CN) 6 ] 3− anion with the [Cu II (tn)] 2+ ion (tn = 1,3-diaminopropane) afford the compounds {[Cu II (tn)] 2 [Fe II (CN) 6 ]}3·[Na 3 Fe III (CN) 6 ]·12H 2 O (1) and {[Cu n (tn)] 2 [Fe II (CN) 6 ]}·KCl·5H 2 O (2). Despite the differences concerning their asymmetric units, both structures present strong similar features: in both structures, the Cu(II) ion presents a square-base pyramidal CuN 5 environment and each [Fe II (CN) 6 ] 4− anion is linked to six Cu(II) ions through its six N atoms leading to infinite [Cu II (tn)] 2 [Fe II (CN) 6 ] layers which can be viewed as 2-D layered arrangement generated by the defective cubane units Cu 4 Fe 3 involving Fe-CN…
Spin crossover (SCO) iron(II) coordination polymer chain: Synthesis, structural and magnetic characterizations of [Fe(abpt)2(μ-M(CN)4)] (M=PtII and N…
2013
Abstract New iron(II) coordination polymeric neutral chain of formula [Fe(abpt) 2 (μ-M(CN) 4 )], with M = Pt II ( 1 ), Ni II ( 2 ) and abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole, have been synthesized and characterized by infrared spectroscopy, X-ray diffraction and magnetic measurements. The two compounds are isostructural as deduced from a Rietveld analysis of X-ray powder diffraction data of 2 simulated from the single crystal structure of 1 . The crystal packing of 1 is formed by regular chains running along the crystallographic [−1 0 1] direction where the planar [Pt(CN) 4 ] 2− anion acts as a μ 2 -bridging ligand via two nitrogen atoms of two different trans cyano groups, whi…
Ring opening polymerization of d,l-lactide and ε-caprolactone catalysed by (pyrazol-1-yl)copper(ii) carboxylate complexes
2021
1,2-Bis{(3,5-dimethylpyrazol-1-yl)methyl}benzene (L) reacts with [Cu(OAc)2] and C6H5COOH, 4-OH-C6H4COOH, 2-Cl-C6H4COOH and (3,5-NO2)2-C6H3COOH to afford the copper complexes [Cu2(C6H5COO)4(L)2] (1), [Cu2(4-OH-C6H4COO)4(L)2] (2), [Cu2(2-Cl-C6H4COO)4(L)2]n (3) and [Cu{(3,5-NO2)2-C6H3COO}2L]n (4) which are characterised by IR, mass spectrometry, elemental analyses, and X-ray crystallography. The structural data revealed two geometries that are adopted by the complexes: (i) paddle wheel in 1, 2·7H2O, 3 and (ii) regular chains in 3 and 4. Magnetic studies show strong antiferromagnetic couplings in the paddle wheel complexes and a weak antiferromagnetic coupling in the monometallic chain one. Cat…
An investigation of photo- and pressure-induced effects in a pair of isostructural two-dimensional spin-crossover framework materials
2014
International audience; Two new isostructural iron(II) spin-crossover (SCO) framework (SCOF) materials of the type [Fe(dpms)2 (NCX)2 ] (dpms=4,4'-dipyridylmethyl sulfide; X=S (SCOF-6(S)), X=Se (SCOF-6(Se))) have been synthesized. The 2D framework materials consist of undulating and interpenetrated rhomboid (4,4) nets. SCOF-6(S) displays an incomplete SCO transition with only approximately 30 % conversion of high-spin (HS) to low-spin iron(II) sites over the temperature range 300-4 K (T1/2 =75 K). In contrast, the NCSe(-) analogue, SCOF-6(Se), displays a complete SCO transition (T1/2 =135 K). Photomagnetic characterizations reveal quantitative light- induced excited spin-state trapping (LIES…