Note that there are imposing the peaks of N1s and Yb4p, whose parameters are derived from the decomposition peak at Yb4p1/2 in Yb oxide. In N1s spectra of asymmetric Yb pyridyl-phenyl complexes two peaks of nitrogen structure were observed at 399.6 and 398.5 eV related with pyridyl group and central Yb-N group features. In symmetric Yb metalloporphyrin charge distribution is more uniform for N1s spectra, thus wide peak of N1s states shows small difference between pyrrole- and aza-nitrogen in metalloporphyrins, in consequence of that formed a single N1s state. The central atom of Yb, replacing the two hydrogen atoms has bound to the all equivalent the nitrogen atoms. These N1s levels with binding energies of 399.8 and 397.8 eV were assigned to sp3 and sp2 nitrogen respectively (pyrrol- and aza-states associated with the protonated and not protonated nitrogen). There are two peaks at the spectrum of the core levels of the N1s level in the pristine TPP. Wide peak in the range 282 and 290 eV were seen in the wide C1s spectra that are related to the unequivalent C atoms in the molecules (aromatic at 284.5eV, 286.5 eV и 288.5 eV for metoxycarbonil and acetilacetone group respectively). Different peaks were seen in the C1s spectra related to the chemically unequivalent C atoms in the molecules.
The X-ray photoemission data show these different atomic constituents in accordance with its states in the molecules which can be related to the peaks of N1s, C1s, O1s, Yb4d appearing in the electronic spectra. All elements of pristine TPP and metalloporphyrins were found in XPS spectra (photon energy 1486.69 eV (Al Kα) after moderate annealing in UHV. The base pressure during measurements was in the range 5∙10-10–2∙10-9 torr. The surfaces of ex situ prepared samples were additionally cleaned in situ by resistive heating up to ~ 400 K in ultra high vacuum (UHV) and/or cleaned by ion gun. Samples for X-ray photoemission spectroscopy were prepared by chemical deposition (drop coating solution of the compounds) self-assembling techniques ex situ from the CHCl3 or CCl4 solution onto Ag and/or the sample was pressed in an indium substrate ex situ. Spectra were calibrated using Ag3d5/2 and In3d5/2 lines. To obtain this information high resolution of N1s, C1s, valence band spectra were measured at Kratos AXIS Ultra DLD spectrometer (the photon energy 1486.69 eV, Al Kα mono) (total resolution Ag 3d5/2 was about 0.48 eV). In present work electronic structure and chemical bonding in tetrakis-porphyrins and precursors were studied experimentally by X-ray (XPS) photoemission spectroscopy.
The occupied and empty states of porphyrins which are involved in chemical bonding are essentially responsible for promising properties and should be studied by optic photoelectron spectroscopy. For understanding and tailoring their properties knowledge of electronic structure and bonding in these compounds are required.
#ASYMMETRIC XPS PEAK FREE#
Unlike the free bases of porphyrins ytterbium complexes under the light irradiation do not create toxic concentration of singlet oxygen 1О2 retaining a high affinity to malignant tumors at the same time. Such substances can be used at present for the cancer photodynamic therapy. Additional interest in ytterbium porphyrins complexes is determined by a possibility of their use as effective markers in luminescent diagnostics of malignant tumors since porphyrins are capable to accumulate in various types of cancer cells and tumors microvessels. As shown for a wide class of porphyrins one can vary electronic state by ligands and metal doping. Niobium gets its name from the mortal Niobe of Greek mythology who turned to stone after she wept for the loss of her children and husband.Organic molecular films of RE porphyrins have attracted attention over the past years in view of potential applications as templates for nanomaterials synthesis, biology, and medicine. This element is a Type II superconductor, which means that it remains a superconductor even in high magnetic fields. Niobium is a compound in some stainless steels and is an alloy of other nonferrous metals, such as those used in pipeline construction. Niobium is chemically very close to tantalum. This color makes niobium attractive for use in body piercing jewelry. Normally shiny gray, niobium develops a bluish tinge when exposed to air at room temperature.
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