Magnetism of ferriprotoporphyrin IX monomers and dimers

Abstract

a b s t r a c tThe SQUID and the 57 Fe Mössbauer spectroscopy studies of the magnetic properties of monomeric and dimeric forms of iron porphyrin were performed between 2 and 305 K. The effective magnetic relaxation rate of the Fe atoms in iron porphyrin monomers exhibits complex temperature dependence, resulting from the competing spin-spin and spin-lattice relaxation processes. The dimerization of iron porphyrin dramatically speeds up the magnetic relaxation. The Fe-Fe antiferromagnetic exchange coupling constant in Fe-O-Fe dimer is J E À 110 cm. The complementary application of SQUID and the Mössbauer spectroscopy is proposed as a new precise quantitative analytical methodology for monitoring of the aggregation process of iron porphyrin.

Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex

“…This assignment is acceptable because of the equal areas under the components of the doublets. Such a kind of the asymmetry is characteristic for the temperature dependent relaxation processes [18][19][20] and positive sign of the V zz component of electric fi eld gradient (EFG) tensors. The positive sign of the V zz indicates that Fe ion has more negative charge in the porphyrin plane than the perpendicular direction to it [17].…”

Diffuse PeV neutrinos from EeV cosmic ray sources: Semirelativistic hypernova remnants in star-forming galaxies

“…Compared to normal supernovae, the local event rate of SR-hypernovae is ∼ 1% while their explosion energy is dozens of times larger, so the integral energy production rate of supernovae may be a few times larger than that of SR-hypernovae. But the rate of SR-hypernovae relative to supernovae might be higher at high redshifts, as SRhypernovae may be engine-driven like long GRBs [58], which seem to occur preferentially in low-metallicity galaxies [61]. This would suggest a relatively smaller contribution of normal SNRs at higher z.…”

“…Given the infrared luminosity of our Galaxy is ∼ 10 10 L ⊙ and assuming a pp−collision efficiency of 10 −3 , we estimate the total Galactic neutrino luminosity at 100 TeV-1 PeV is 10 36 erg s −1 . Note that our Galaxy might be too metal rich to host semi-relativistic hypernovae (or long GRBs) for the last several billion years [61], so the real value could be smaller. Even if all these neutrinos are produced in the Galactic center and radiate isotropically, it would result in 1 event detection during 662 days operation within a 8 • circular region around the Galactic Center [62] and would not cause a strong anisotropy that violates the observations [2].…”

Spectroscopic study and electronic structure of prototypical iron porphyrins and their μ-oxo-dimer derivatives with different functional configurations

“…15 Also Mössbauer spectroscopy studies, performed on the complexes we investigated, claimed the occurrence of a solvation effect. 16 As an ideal local structural probe, the X-ray absorption spectroscopy was already used to investigate local structural congurations of porphyrins, [17][18][19] as well as to identify spin-structures combining Mössbauer data and other magnetic and spectroscopic measurements, etc. 19 Metalloporphyrins are networking molecules with strong internal N-H hydrogen bonds that may be used to substitute a metal ion inside a porphyrin ring, forming a metallo complex.…”