Preparation and Properties of Gadolinium Homoleptic Double-and Triple-Decker Complexes Containing Tetrabenzoporphyrin Ligand

2013 ◽  
Vol 750-752 ◽  
pp. 1816-1821
Author(s):  
Qi Feng Liu
Keyword(s):  
Room Temperature ◽  
Spin Exchange ◽  
Spectroscopic Studies ◽  
Magnetic Interactions ◽  
Antiferromagnetic Coupling ◽  
Ir Absorption ◽  
Magnetic Studies ◽  
Absorption Bands ◽  
Near Ir ◽  
Sandwich Type

Two novel gadolinium sandwich-type complexes containing tetrabenzoporphyrin (TBP) ligands-Gd (TBP)2and Gd (TBP)3were prepared from porphyrin 1 and Gd (acac)3. nH2O under Ar by boiling 1, 2, 4-Tcb for 15~17h and 45~48 h respectively. Their structures are characterized by Uv-Vis, HR-MS and IR. The spectroscopic studies show that their longest-wavelength visible and near-IR absorption bands are obviously red-shifted due to the extension of the π conjugated systems in the TBP ring. The magnetic studies indicate that the observed value of χMT for Gd (TBP)2is close to the combined value of Gd (III) and porphyrin radical anion at room temperature and that antiferromagnetic interaction possibly results from the intramolecular spin exchange between the porphyrin π-radical electron and that the gadolinium f unpaired electrons dominates its magnetic properties over the whole temperature range while there is no magnetic interactions between two Gd (III) ions in Gd (TBP)3in the range from room temperature down to 20K and very weak antiferromagnetic coupling exsits between two Gd (III) ions below 20K.

Preparation and Characterization of a Novel Gadolinium Triple-Decker Sandwich-Type Complex with Tetrabenzoporphyrin Ligand

2013 ◽  
Vol 690-693 ◽  
pp. 573-576
Author(s):  
Qi Feng Liu
Keyword(s):  
Room Temperature ◽  
Spectroscopic Properties ◽  
Magnetic Interactions ◽  
Antiferromagnetic Coupling ◽  
Magnetic Studies ◽  
Conjugated Systems ◽  
Type Complex ◽  
Vis Spectroscopy ◽  
Sandwich Type

A novel gadolinium triple-decker sandwich-type complex containing tetrabenzoporphyrin (TBP) ligands-Gd (TBP)3was prepared from porphyrin 1 and Gd (acac)3.nH2O in boiling 1, 2, 4-Tcb for 45~48 h under Ar. Its structure is characterized by Uv-Vis spectroscopy and HR-MS. The spectroscopic properties show that its longest-wavelength visible band (600-800 nm) is obviously red-shifted due to the extension of the π conjugated systems derived from the linear benzoannulation in the TBP ring. The magnetic studies also indicate that there is no magnetic interactions between two Gd (III) ions in the triple-deckers in the range from room temperature down to 20K and very weak antiferromagnetic coupling exists between two Gd (III) ions below 20K.

Synthesis, Properties of Gadolinium Double-Decker Sandwich-Type Complex Containing Tetrabenzoporphyrin Ligand

2012 ◽  
Vol 190-191 ◽  
pp. 571-574 ◽  
Author(s):  
Hai Yun Xu ◽  
Chun Hua Hu ◽  
Qi Feng Liu ◽  
Wen Xian Zhao ◽  
Ying Liu
Keyword(s):  
Spin Exchange ◽  
Spectroscopic Characterization ◽  
Spectroscopic Properties ◽  
Ir Absorption ◽  
Magnetic Studies ◽  
Group 4 ◽  
Type Complex ◽  
Double Decker ◽  
Synthesis Properties ◽  
Sandwich Type

A novel gadolinium double-decker sandwich-type complex with tetrabenzoporphyrin (TBP) ligands-Gd(TBP)2 was synthesized by the reaction of porphyrin 1 with Gd(acac)3. nH2O in boiling 1, 2, 4-Tcb for 15~17 h under Ar. Its structure is characterized byUv-Vis-NIR and HR-MS. The spectroscopic properties show that the longest-wavelength visible band (600-800 nm) and the strong near-IR absorption band centered near 1340 nm of Gd (TBP)2 complex are obviously red-shifted due to the extension of the π conjugated systems derived from the linear benzoannulation in the TBP ring. The magnetic studies also indicate that the observed value of χMT of Gd(TBP)2 complex is close to the combined value of Gd(III) and porphyrin radical anion at room temperature, and antiferromagnetic interaction that possibly results from the intramolecular spin exchange between the porphyrin π-radical electron, and the gadolinium f unpaired electrons dominates its magnetic properties over the whole temperature range. Since the first report of bis(porphyrinato) metal complexes M(Por)2 such as a cerium(IV) bisporphyrinate, Ce(TPP)2 and hydrogen praseodymium(III), PrH(TPP)2 in 1983[1], sandwich-type rare earth complexes with porphyrin ligands have received increasing attentions due to the unusual physical, spectroscopic, redox, electron transfer, and/or conductivity properties resulting from their strong π-π interactions[2-4]. Whereas the chemistry and properties of homoleptic sandwich complexes containing the same pophyrinato ligands of various lanthanide, actinides and group 4 transition metals have been extensively studied[5-6], actually all of them are confined to the sandwich-type complexes containing meso-substituted porphyrin ligands except for octaethylporphyrin (OEP) or octamethylporphyrin (OMP). Little is known about sandwich-like complexes with aromatic ring-fused porphyrin ligands that contain a more delocalized π system. In this paper, we will describe the preparation of a novel gadolinium homoleptic double-decker sandwich-type complex with tetrabenzoporphyrin (TBP) ligand (see Fig.1) as well as their spectroscopic characterization and magnetic studies.

scholarly journals Absorption and Emission Spectra for C60 Anions

1994 ◽  
Vol 14 (1-3) ◽  
pp. 155-160 ◽  
Author(s):  
Tatsuhisa Kato
Keyword(s):  
Absorption Spectrum ◽  
Absorption Band ◽  
Theoretical Analysis ◽  
Room Temperature ◽  
Emission Spectra ◽  
Mirror Image ◽  
Ir Absorption ◽  
Near Ir ◽  
Laser Experiments ◽  
Ir Bands

Absorption spectra are detected for C60− and C602− produced electrolytically in solution at room temperature. Theoretical analysis of the spectrum of C60− by CNDO/S calculations gives an interpretation of the characteristic near-IR bands, the weak visible bands, and the strong bands in the UV region. The emission spectrum of C60− is a mirror image of the near-IR absorption band, and the detection of the emission reconfirms our original assignment of the absorption spectrum. The nature of the spectrum of C602− is characterized by a similar orbital picture to that of C60−. Further laser experiments of significance are proposed.

scholarly journals Local vibrational modes of vacancy-oxygen-related complexes at room temperature

2020 ◽  
Vol 56 (4) ◽  
pp. 480-487
Author(s):  
E. A. Tolkacheva ◽  
V. P. Markevich ◽  
L. I. Murin
Keyword(s):  
Absorption Band ◽  
Room Temperature ◽  
Clear Correlation ◽  
Ir Absorption ◽  
Oxygen Impurity ◽  
Interstitial Oxygen ◽  
Vibrational Modes ◽  
Oxygen Defect ◽  
Absorption Bands ◽  
Local Vibrational Modes

The isotopic content of natural silicon (28Si (92.23 %), 29Si (4.68 %) и 30Si (3.09 %)) affects noticeably the shape of IR absorption bands related to the oxygen impurity atoms. In the present work an attempt is undertaken to determine the positions of local vibrational modes (LVMs), related to quasimolecules 28Si16OS29Si and 28Si16OS30Si (OS – substitutional oxygen atom), for the absorption spectra measured at room temperature. An estimation of the isotopic shifts of corresponding modes is done by fitting the shape of the experimentally measured absorption band related to the vacancy–oxygen center in irradiated Si crystals. The LVM isotope shifts are found to be equal 2,2 ± 0.25 cm–1 for 28Si-16OS29Si and 4,3 ± 0,9 см–1 for 28Si-16OS30Si in relation to the basic band due to 28Si-16OS28Si, and the full width at half maximum of the A-center absorption band (28Si-16OS28Si) is 5,3 ± 0.25 cm–1. By means of infrared absorption spectroscopy a clear correlation between the disappearance of the divacancy (V2) in the temperature range 200–275 ºС and appearance of two absorption bands with their maxima at 825.8 and 839.2 cm–1 in irradiated oxygen-rich Si crystals is found. The band positioned at 825.8 cm–1 is assigned to a divacancy-oxygen defect V2O formed via an interaction of mobile V2 with interstitial oxygen (Oi ) atoms. The 839.2 cm–1 band is much more pronounced in neutron irradiated samples as compared to samples irradiated with electrons. We argue that it is related to a trivacancy–oxygen defect (V3O) formed via an interaction of mobile V3 with Oi atoms.

scholarly journals Mössbauer Spectroscopy, Structural and Magnetic Studies of Zn2+Substituted Magnesium Ferrite Nanomaterials Prepared by Sol-Gel Method

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Yun He ◽  
Xingxing Yang ◽  
Jinpei Lin ◽  
Qing Lin ◽  
Jianghui Dong
Keyword(s):  
Saturation Magnetization ◽  
Room Temperature ◽  
Mössbauer Spectra ◽  
Zinc Concentration ◽  
Sol Gel ◽  
Magnetic Interactions ◽  
Magnesium Ferrite ◽  
Magnetic Studies ◽  
Mossbauer Spectra ◽  
Absorption Area

Zinc substituted magnesium ferrite nanomaterialsMg1-xZnxFe2O4(x= 0, 0.1, 0.3, 0.5, 0.7) powders have been prepared by a sol-gel autocombustion method. The lattice parameter increases with increase in Zn concentration, but average crystallite size tends to decrease by increasing the zinc content. SEM results indicate the distribution of grains and morphology of the samples. Some particles are agglomerated due to the presence of magnetic interactions among particles. Room temperature Mössbauer spectra ofMg1-xZnxFe2O4shows that the A Mössbauer absorption area decreases and the B Mössbauer absorption area increases with zinc concentration increasing. The change of the saturation magnetization can be explained with Néel’s theory. It was confirmed that the transition from ferrimagnetic to superparamagnetic behaviour depends on increase in zinc concentration by Mössbauer spectra at room temperature. Saturation magnetization increases and coercivity decreases with Zn content increasing.

scholarly journals A Minireview of the Natures of Radiation-Induced Point Defects in Pure and Doped Silica Glasses and Their Visible/Near-IR Absorption Bands, with Emphasis on Self-Trapped Holes and How They Can Be Controlled

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
David L. Griscom
Keyword(s):  
Dose Rate ◽  
Optical Fibers ◽  
Point Defects ◽  
Ir Absorption ◽  
Absorption Bands ◽  
Space Applications ◽  
Ambient Temperatures ◽  
Silica Glasses ◽  
Near Ir ◽  
Radiation Induced

The natures of most radiation-induced point defects in amorphous silicon dioxide (a-SiO2) are well known on the basis of 56 years of electron spin resonance (ESR) and optical studies of pure and doped silica glass in bulk, thin-film, and fiber-optic forms. Many of the radiation-induced defects intrinsic to pure and B-, Al-, Ge-, and P-doped silicas are at least briefly described here and references are provided to allow the reader to learn still more about these, as well as some of those defects not mentioned. The metastable self-trapped holes (STHs), intrinsic to both doped and undoped silicas, are argued here to be responsible for most transient red/near-IR optical absorption bands induced in low-OH silica-based optical fibers by ionizing radiations at ambient temperatures. However, accelerated testing of a-SiO2-based optical devices slated for space applications must take into account the highly supralinear dependence on ionizing-dose-rate of the initial STH creation rate, which if not recognized would lead to false negatives. Fortunately, however, it is possible to permanently reduce the numbers of environmentally or operationally created STHs by long-term preirradiation at relatively low dose rates. Finally, emphasis is placed on the importance and utility of rigorously derived fractal-kinetic formalisms that facilitate reliable extrapolation of radiation-induced optical attenuations in silica-based photonics recorded as functions of dose rate backward into time domains unreachable in practical laboratory times and forward into dose-rate regimes for which there are no present-day laboratory sources.

scholarly journals Calibrations coefficients for determination of concentrations of vacancy-oxygen-related complexes and oxygen dimer in silicon by means of infrared absorption spectroscopy

2021 ◽  
Vol 66 (2) ◽  
pp. 227-233
Author(s):  
I. F. Medvedeva ◽  
V. P. Markevich ◽  
K. A. Talkachova ◽  
A. A. Fadzeyeva ◽  
D. N. Zhdanovich ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Infrared Absorption ◽  
Room Temperature ◽  
Crystalline Silicon ◽  
Calibration Coefficient ◽  
Ir Absorption ◽  
Absorption Bands ◽  
Oxygen Precipitates ◽  
Calibration Coefficients

Vacancy-oxygen complexes VnOm (n, m ≥ 1) in crystalline silicon are nucleation centers for oxygen precipitates, which are widely used as internal getters in modern technologies of production of silicon-based electronic devices and integrated circuits. For the controllable formation of oxygen precipitates in Si crystals in the technology processes the methods of determination of concentrations of the VnOm complexes are required. The aim of the present work was to find values of the calibration coefficients for determination of concentrations of the VnOm defects in Si from intensities of infrared (IR) absorption bands associated with the local vibrational modes (LVM) of these complexes. A combined electrical (Hall effect) and optical (IR absorption) study of vacancy-oxygen defects in identical silicon crystals irradiated with 6 MeV electrons was carried out. Based on the analysis of the data obtained, the values of the calibration coefficient for the determination of concentration of the vacancy-oxygen (VO) complex in silicon by the infrared absorption method were established: for measurements at room temperature (RT) – NVO = 8.5 · 1016 · αVO-RT cm–3, in the case of low-temperature (LT, Т ≡ 10 K) measurements – NVO = 3.5 · 1016 · αVO-LT cm–3, where αVO-RT(LT) are absorption coefficients in maxima of the LVM bands due to the VO complex in the spectra measured at corresponding temperatures. Calibration coefficients for the determination of concentrations of other VnOm (VO2, VO3, VO4, V2O and V3O) complexes and the oxygen dimer (O2) from an analysis of infrared absorption spectra measured at room temperature have been also determined.

scholarly journals FTIR study of carbon monoxide adsorption on ion-exchanged X, Y and mordenite type zeolites

2003 ◽  
Vol 68 (4-5) ◽  
pp. 409-416 ◽  
Author(s):  
Vesna Rakic ◽  
Vera Dondur ◽  
Radmila Hercigonja
Keyword(s):  
Carbon Monoxide ◽  
Fourier Transform ◽  
Transition Metal ◽  
Room Temperature ◽  
Ir Absorption ◽  
Transition Metal Cation ◽  
Absorption Bands ◽  
Ftir Study ◽  
Adsorption Of Co ◽  
Charge Balancing

In this work Fourier transform infrared (FTIR) study has been applied to study the adsorption of carbon monoxide on transition metal (Mn2+, Co2 Ni2+) ion-exchanged zeolites type Y, X and mordenites. The adsorption of CO at room temperature produces overlapping IR absorption bands in the 2120?2200 cm-1 region. The frequency of the band around 2200 cm-1 is found to be dependent not only on the charge-balancing transition metal cation but also on the framework composition. The frequencies of the band near 1600 cm-1 was found to be dependent on the Si/Al ratio of the investigated zeolites.

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