Search results for "Spectroscopy"
showing 10 items of 10293 documents
Hofmann-Like Frameworks Fe(2-methylpyrazine)n[M(CN)2]2 (M = Au, Ag) : Spin-Crossover Defined by the Precious Metal
2020
Hofmann-like cyanometalates constitute a large class of spin-crossover iron(II) complexes with variable switching properties. However, it is not yet clearly understood how the temperature and cooperativity of a spin transition are influenced by their structure. In this paper, we report the synthesis and crystal structures of the metal–organic coordination polymers {FeII(Mepz)[AuI(CN)2]2} ([Au]) and {FeII(Mepz)2[AgI(CN)2]2} ([Ag]), where Mepz = 2-methylpyrazine, along with characterization of their spin-state behavior by variable-temperature SQUID magnetometry and Mössbauer spectroscopy. The compounds are built of cyanoheterometallic layers, which are pillared by the bridging Mepz…
Covalently bonded layer-by-layer assembly of multifunctional thin films based on activated esters.
2009
We demonstrate that chemically stable, multifunctional polymer thin films can be obtained using the layer-by-layer (LbL) deposition based on covalent bonds between adsorbing chains. Poly(pentafluorophenyl-4-vinylbenzoate) (P1) or poly(pentafluorophenylacrylate) (P2) polymers were assembled with poly(allyl amine) (PAAm) to yield LbL multilayer films through amide bond formation by the reaction between activated esters of P1 or P2 and amine groups in PAAm, which was quantitatively monitored by Fourier transform infrared spectroscopy (FT-IR). It was found that the difference in the solubility of P1 and P2 against ethanol, which was used as the solvent for PAAm, during the LbL deposition yields…
Titanium imido complexes stabilised by bis(iminophosphoranyl)methanide ligands: the influence of N-substituents on solution dynamics and reactivity
2014
Terminal titanium imido complexes of the general formula [Ti(N(t)Bu)Cl{CH(Ph2PNR)2}] 4 (R = Ph, (i)Pr, (t)Bu) are reported. These compounds were synthesized from the corresponding Li adducts 3 of BIPMH (bis(iminophosphoranyl)methanide) and Mountford's complex [Ti(N(t)Bu)Cl2(Py)3]. The crystal structures of two of the Ti complexes (R = Ph, (t)Bu) and two of the Li compounds (R = (i)Pr, (t)Bu) are reported. Dynamic solution NMR spectroscopy reveals a dynamic isomerisation process in the case of the Ti complex 4c (R = (t)Bu). DFT studies showed that this dynamic process comes from steric repulsion between the imido ligand and the (t)Bu N-substituents on the BIPMH ligand. Complexes 4 were teste…
Corroles with Group 15 Ions. 2. Synthesis and Characterization of Octaethylcorroles Containing a Phosphorus Central Atom
2001
The synthesis, spectroscopic characterization, and electrochemistry of five new phosphorus corroles are reported. The investigated complexes contain alkyl, aryl, oxo, or hydrido axial ligands and are represented as (OEC)P(H)2, (OEC)P(CH3)2, (OEC)P(C6H5)2, (OEC)P=O, and [(OEC)P(CH3)]+ClO4-, where OEC is the trianion of octaethylcorrole. The products of electrooxidation and/or electroreduction were also characterized by UV-vis and ESR spectroscopy. Correlations are shown to exist between reversible half-wave potentials for the first oxidation and first reduction of each compound and the combined electronegativity of the central ion and the axial ligand(s). The electrochemical HOMO-LUMO gap, d…
Organotin(IV) derivatives of the ambidentate ligand 2-thiouracil. Infrared, Mössbauer, 1H and 13C NMR studies
1984
Abstract Complexes Bu 2 n Sn(s 2 UraH −2 and [Me 2 SnOH] 2 (s 2 UraH −2 have been synthesized. Comparison of infrared spectra of the solid complexes with spectra of s 2 Ura and (PhHg) 2 (s 2 UraH −2 complex and point charge calculations (Mossbauer spectra) allow assignment of structures for the complexes of this ambivalent ligand. Polymeric structures are proposed for the complexes in the solid state, where the organometallic moieties are bonded to exocyclic S and N(3) atoms of the dianionic base, with formation of a four-membered chelate ring for Bu 2 n Sn(s 2 UraH −2 ). For [Me 2 SnOH] 2 (s 2 UraH −2 , 1 H and 13 C NMR data suggest retention of penta-coordination in trifluoacetic acid sol…
A Co-monosubstituted Keggin polyoxometalate with an antenna ligand and three cobalt(II) chains as counterion
2009
Abstract A Co-monosubstituted Keggin polyoxometalate with an antenna ligand linked to the Co(II) center with a Co(II)-containing cation has been prepared. The title compound, formulated as {Co(H 2 O) 4 (4,4′-bpy)} 2 (4,4′-Hbpy) 2 [SiW 11 Co(4,4′-bpy)O 39 ] · 5H 2 O ( 1 ) (4,4′-bpy = 4,4′-bipyridine), was synthesized and characterized by elemental analysis, IR spectra, TG analysis, X-ray single crystal structure analysis and magnetic measurements. As far as we know, the title compound represents the first Co(II) substituted Keggin polyoxometalate with an antenna ligand structurally and magnetically characterized.
Rigidified Calixarenes Bearing Four Carbamoylmethylphosphineoxide or Carbamoylmethylphosphoryl Functions at the Wide Rim
2000
Conformationally rigidified tetraCMPO derivatives have been prepared from calix[4]arene bis(crown ether) 4 a in which adjacent oxygens are bridged at the narrow rim by two diethylene glycol links. Acylation of the tetraamine 4 c with the CMPO-active ester 5 b gave the tetraphosphine oxide 6 a, while the tetraphosphinate 6 b and the tetraphosphonate 6 c were obtained by Arbuzov reaction of tetrabromoacetamido derivative 7 with PhP(OEt)2 or P(OEt)3. The extraction ability of these CMPO derivatives was checked for selected lanthanides and actinides and compared with the analogous compounds 1 b, 10 b and 10 d derived from calix[4]arene tetrapentyl ether. All rigidified bis(crown ether) ligands …
Synthesis, characterization, cytotoxic activity and crystal structures of tri- and di-organotin(IV) complexes constructed from the β-{[(E)-1-(2-hydro…
2006
Abstract Reactions of potassium β-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}propionates (L1HK-L3HK) and potassium β-{[(2Z)-(3-hydroxy-1-methyl-2- butenylidene)]amino}propionate (L4HK) with R3SnCl (R = Ph and nBu) and nBu2SnCl2 yielded complexes of composition Ph3SnL1H (1), Ph3SnL2H (2), Ph3SnL4H (3), nBu3SnL1H (4), and {[nBu2Sn(L2H)]2O}2 (5) and {[nBu2Sn(L3H)]2O}2 (6), respectively. These complexes have been characterized by 1H, 13C, 119Sn NMR, ESI-MS, IR and 119mSn Mossbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of 1, 4, 5 and 6 were determined. In the solid state, compound 1 is a one-dimensional polymer built from SnPh3 moieties bridged by s…
Semiconductor Nanocrystals with Multifunctional Polymer Ligands
2002
In this letter, we describe the preparation of a versatile polymer ligand, which can be attached to CdSe/ZnS semiconductor nanocrystals via a phase transfer reaction. The ligand is based on a chain of reactive esters, which can, in principle, be substituted by any compound containing amino-functionalities. The polymer/nanocrystal complexes are characterized in terms of structure and photostability.
Structure of a polysaccharide from the lipopolysaccharide of Vibrio vulnificus clinical isolate YJ016 containing 2-acetimidoylamino-2-deoxy-L-galactu…
2009
Abstract A polysaccharide isolated after mild acid degradation of the lipopolysaccharide of Vibrio vulnificus clinical isolate YJ016 was found to contain l -Fuc, d -GlcpNAc, 2,4-diacetamido-2,4,6-trideoxy- d -glucose (di-N-acetylbacillosamine, d -QuiNAc4NAc), and 2-acetimidoylamino-2-deoxy- l -galacturonic acid ( l -GalNAmA). The last sugar derivative was confirmed by correlations for nitrogen-linked protons in 2D TOCSY and ROESY spectra measured in a H2O–D2O mixture. The following structure of the polysaccharide was established by 1H and 13C NMR spectroscopy, including 2D ROESY and 1H,13C HMBC experiments: Download : Download full-size image where the degree of 6-O-acetylation of the later…