Search results for "Spectroscopy"
showing 10 items of 10293 documents
Synthesis and magnetic properties of an iron 1,2-bisthienyl perfluorocyclopentene photochromic coordination compound
2011
Abstract The coordination compound Fe(BM-4-PTP) 2 (NCS) 2 ⋅2MeOH ( 1 ) including the photoisomerizable ligand BM-4-PTP (1,2-bis(2′-methyl-5′-(pyrid-4″-yl)thien-3′-yl)perfluorocyclopentene) was obtained as an orange powder. The powder turns blue upon photocyclization of the 1,2-bisthienyl photochromic ligand induced by UV light irradiation at room temperature. Photocycloreversion is obtained by visible light irradiation of the material in the solid state. The orange and blue powders were investigated over the temperature range (5–293 K) and pressure range (1 bar–12 kbar) by magnetic susceptibility measurements and variable temperature 57 Fe Mossbauer spectroscopy. The photo-induced colour ch…
Neutron scattering characterization of homopolymers and graft-copolymer micelles in supercritical carbon dioxide
1996
Abstract Superficial fluids (SCF) are becoming an attractive alternative to the liquid solvents traditionally used as polymerization media [1]. As the synthesis proceeds, a wide range of colloidal aggregates form, but there has hitherto been no way to measure such structures directly. We have applied small-angle neutron scattering (SANS) to characterize such systems, and although SCF polymerizations are carried out at high pressures, the penetrating power of the neutron beam means that typical cell windows are virtually transparent. Systems studied include polymers soluble in CO 2 such as poly(1,1-dihydroperfluorooctyl acrylate) (PFOA), poly(hexafluoropropylene oxide) (PHFPO) and poly(dimet…
Multifunctional magnetic materials obtained by insertion of a spin-crossover Fe(III) complex into bimetallic oxalate-based ferromagnets.
2010
The syntheses, structures and magnetic properties of the compounds of formula [Fe(III)(sal(2)-trien)][Mn(II)Cr(III)(ox)(3)].CH(2)Cl(2) (1; H(2)sal(2)-trien=N,N'-disalicylidenetriethylenetetramine, ox=oxalate), [Fe(III)(sal(2)-trien)][Mn(II)Cr(III)(ox)(3)].CH(3)OH (2), [In(III)(sal(2)-trien)][Mn(II)Cr(III)(ox)(3)].0.25H(2)O.0.25CH(3)OH.0.25CH(3)CN (3), and [In(III)(sal(2)-trien)][Mn(II)Cr(III)(ox)(3)].CH(3)NO(2).0.5H(2)O (4) are reported. The structure of 1 presents a 2D honeycomb anionic layer formed by Mn(II) and Cr(III) ions linked through oxalate ligands and a cationic layer of [Fe(sal(2)-trien)](+) complexes intercalated between the 2D oxalate network. The structures of 2, 3, and 4 pres…
Study by FT-IR spectroscopy of ageing of adhesives used in restoration of archaeological glass objects
1999
Abstract A study by FT-IR spectroscopy which aims to compare the stability of five polymers, Araldit XW396/XW 397, Vitralit 7256, Loctite 350, Desmodur N 75/Viacryl SM 564/65 and Krafft silicone commonly used in the restoration of archaeological glass objects when subjected to thermal ageing, UV light ageing and cyclic ageing in SO 2 pollutant chamber has been carried out. Two series of test specimens were prepared in order to reproduce the two methods of application of polymers commonly used in restoration treatments as adhesive and consolidant or coating of glass fragments. Modifications in the chain or side chain structure of polymers, alterations of carbonyl groups in Araldit and isocya…
Rapid cooling experiments and use of an anionic nuclear probe to sense the spin transition of the 1D coordination polymers [Fe(NH2trz)3]SnF6n x H2O (…
2008
[Fe(NH(2)trz)(3)]SnF(6)n H(2)O (NH(2)trz=4-amino-1,2,4-triazole; n=1 (1), n=0.5 (2)) are new 1D spin-crossover coordination polymers. Compound 2 exhibits an incomplete spin transition centred at around 210 K with a thermal hysteresis loop approximately 16 K wide. The spin transition of 2 was detected by the Mossbauer resonance of the (119)Sn atom in the SnF(6) (2-) anion primarily on the basis of the evolution of its local distortion. Rapid-cooling (57)Fe Mossbauer and superconducting quantum interference device experiments allow dramatic widening of the hysteresis width of 2 from 16 K up to 82 K and also shift the spin-transition curve into the room temperature region. This unusual behavio…
Synthesis and Characterization of theO-Alkylation Products of Resorcinarene
2013
O-Substitution reactions of tetramethoxyresorcinarene with alkyl halides produced a variety of partially O-alkylated resorcinarene derivatives with terminal alkyne functionality. The degree of alkylation was affected by the reactivity of the alkylating halide used. NMR spectroscopy proved to be an ideal tool for analyzing the complex reaction mixtures and the isolated products based on the symmetry and degree of alkylation of the resorcinarene derivatives. Single-crystal X-ray diffraction studies furthermore showed diversity in the self-assembly of the various O-alkylation products that was greatly affected by the degree of alkylation, as well as the nature of the alkyne moiety.
Synthesis and characterisation of tetrazole compounds: 3 series of new ligands representing versatile building blocks for iron(II) spin-crossover com…
2005
Abstract New tetrazole compounds were synthesized and characterised by NMR and FTIR spectroscopy as well as by single crystal X-ray diffraction. We present in this paper mono- and ditetrazoles, which represent a versatile class of building blocks for the formation of mononuclear iron(II) complexes with monotetrazoles as terminal ligands as well as iron(II) coordination polymers with ditetrazoles as bridging ligands. Especially, the series of α,ω-bis[tetrazol-1-yl]-alkanes open the field of fascinating supramolecular structures with spin transition properties.
Multispectral autoflourescence detection of skin neoplasia using steady-state techniques
2019
In the current study were used excitation-emission matrices (EEMs) and synchronous fluorescence spectroscopy (SFS) steady-state techniques in a broad spectral regions (excitation at 220-500 nm and emission at 280-850 nm) to achieve the whole set of endogenous fluorophores, existed in normal and neoplastic cutaneous tissues. Several types of benign, dysplastic and malignant types of skin lesions were investigated ex vivo using both EEM and SFS modalities, namely the basal cell papilloma and carcinoma, pigmented nevi, dysplastic nevi, squamous cell carcinoma and malignant melanoma. Histological analysis was used as a “gold standard” for evaluation of clinical diagnosis of the lesions investig…
Properties and structure of raised bog peat humic acids
2013
Abstract Humic substances form most of the organic components of soil, peat and natural waters, and their structure and properties differ very much depending on their source. The aims of this study are to characterize humic acids (HAs) from raised bog peat, to evaluate the homogeneity of peat HAs within peat profiles, and to study peat humification impact on properties of HAs. A major impact on the structure of peat HAs have lignin-free raised bog biota (dominantly represented by bryophytes of different origin). On diagenesis scale, peat HAs have an intermediate position between the living organic matter and coal organic matter, and their structure is formed in a process in which more labil…
Molecular motion, thermal expansion, and phase transitions in paraffins: A model for polymers
2007
Owing to their simple chemical structure paraffins are generally regarded as representing a system which is especially suitable for a model study of the thermal behavior of oligomeric and polymeric solids. Extensive investigations on the properties of n-tritriacontane (C33H68) provide an example. For this system an identification of several types of motional mechanisms become possible. Their presence leads to peculiarities in the thermal expansion and to the occurrence of solid-solid phase transitions. Paraffins and polyethylene exhibit a marked anisotropy in the lateral thermal expansion. An analysis of the molecular background can be based on a modified Gruneisen theory which connects exp…