Fourier-transform Raman and infrared spectroscopic analysis of 2-nitro-tetraphenylporphyrin and metallo-2-nitro-tetraphenylporphyrins

Evolution of Nanoflowers and Nanospheres of Zinc Bisporphyrinate Tweezers at the Air/Water Interface

Although the sophisticated Langmuir and Langmuir-Blodgett (LB) techniques facilitate the fabrication of uniform ultrathin monolayer and films, they are also revealed as powerful tools for the bottom-up construction of the nanostructures through the air/water interface. In this paper, unique nanoflowers or nanospheres were constructed based on the synthesized m-phthalic diamide-linked zinc bisporphyrinate tweezers using the Langmuir and LB techniques. It was found that the two tweezer-type zinc bisporphyrinates could form stable two-dimensional spreading films at the air/water interface, which could be subsequently transferred onto solid substrates using the vertical lifting method. Atomic force microscopy (AFM) revealed that at the initial spreading stage, the compound formed flat disklike domains and then hierarchically evolved into nanoflowers or nanospheres upon compressing the floating film. Such nanostructures have not been reported before and cannot be fabricated using the other self-assembly methods.

Highly fluorescent peptide nanoribbon impregnated with Sn-porphyrin as a potent DNA sensor

Highly fluorescent and thermo-stable peptide nanoribbons (PNRs) were fabricated by solvothermal self-assembly of a single peptide (D,D-diphenyl alanine peptides) with Sn-porphyrin (trans-dihydroxo[5,10,15,20-tetrakis(p-tolyl)porphyrinato] Sn(IV) (SnTTP(OH)2)). The structural characterization of the as-prepared nanoribbons was performed by transmitting electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM), FT-IR and Raman spectroscopy, indicating that the lipophilic Sn-porphyrins are impregnated into the porous surface formed in the process of nanoribbon formation through intermolecular hydrogen bonding of the peptide main chains. Consequently the Sn-porphyrin-impregnated peptide nanoribbons (Sn-porphyrin-PNRs) exhibited typical UV-visible absorption spectrum of the monomer porphyrin with a red shifted Q-band, and their fluorescence quantum yield was observed to be enhanced compared to that of free Sn-porphyrin. Interestingly the fluorescence intensity and lifetimes of Sn-porphyrin-PNRs were selectively affected upon interaction with nucleotide base sequences of DNA while those of free Sn-porphyrins were not affected by binding with any of the DNA studied, indicating that DNA-induced changes in the fluorescence properties of Sn-porphyrin-PNRs are due to interaction between DNA and the PNR scaffold. These results imply that Sn-porphyrin-PNR will be useful as a potent fluorescent protein analogue and as a biocompatible DNA sensor.

β-Nitro-substituted free-base, iron(III) and manganese(III) tetraarylporphyrins: synthesis, electrochemistry and effect of the NO2 substituent on spectra and redox potentials in non-aqueous media

Two free-base and four metal derivatives of substituted tetraarylporphyrins containing a nitro-substituent on the β-pyrrole position of the macrocycle were synthesized and characterized by UV-vis, FTIR, 1 H NMR and mass spectrometry as well as electrochemistry and spectroelectrochemistry in non-aqueous media. The porphyrins are represented as ( NO 2 TmPP ) M and ( NO 2 TdmPP ) M , where M = 2 H , Fe III Cl or Mn III Cl , m is a CH 3 group on the para-position of the four meso-phenyl rings of the tetraphenylporphyrin (TPP) and dm represents two OCH 3 substituents on the meta-positions of each phenyl ring of the TPP macrocycle. UV-visible spectra of the nitro-substituted porphyrins exhibit absorption bands which are red-shifted by 4–11 nm as compared to bands of the same substituted tetraarylporphyrins lacking a nitro substituent. Three or four reductions are observed for each iron and manganese nitroporphyrin, the first of which is metal-centered, leading to formation of an Fe ( II ) or Mn ( II ) complex. Further reduction at the metal center occurs for the iron porphyrins but this reaction proceeds via an Fe ( II ) π anion radical in the case of the two nitro-substituented derivatives. The β-nitro-substituted porphyrins are easier to reduce and harder to oxidize than the corresponding compounds lacking a nitro group. The effect of NO 2 substituent on reduction/oxidation potentials and the site of electron transfer was also discussed.

Resonance Raman spectra of highly reduced iron porphycenes

The redox behavior of iron porphycenes using the sodium mirror contact technique is reported. The resonance Raman spectra are obtained for each redox state, in order to explore the vibrational characteristics of these species in different redox states. The observed resonance Raman behavior of Fe II porphycene anion radical and its dianion is interpreted using the vibrational analysis of free-base porphycene anion radical and dianion. For the first time, a species generated in the fourth reduction step, is confirmed by UV-vis spectroscopy and is assigned to Fe I porphycene π dianion. The dependence of resonance enhancements of Raman bands for the Fe I porphycene π dianion on excitation laser reveals structural distortion along the NC a C a N or C b C a C a C b segments of the pyrrole-pyrrole direct connection in the excited electronic state.

Resonance Raman and absorption properties of Zn(II) and Ni(II) polynitroporphyrins and their chemical reduction products

Electron-deficient metallocomplexes of dodeca- and octanitroporphyrins produced by the introduction of 8 β-nitro substituents or 8 β-nitro and a meta-nitro substituent on each meso-aryl ring of Zn (II) and Ni (II) [meso-tetra-(2,6-dichlorophenyl)porphyrin] (Zn8, Ni8 and Zn12, Ni12, respectively) and their air-stable reduced species have been characterized by steady-state absorption and Soret-excited resonance Raman spectroscopies. One-electron reduced species of the metallocomplexes were produced by three different procedures (in deprotonated tetrahydrofuran in air ambient, in tetralhydrofuran with the addition of piperidine in air ambient, and in contact with a sodium mirror under vacuum) and demonstrated similar absorption and RR spectra. It is concluded on the basis of the RR spectra that the one-electron reduction products of the studied polynitrosubstituted metalloporphyrins are π–anion radicals in character.