Electronic structure of metalloporphyrin π-anions

Gurinovich, G. P.; Gurinovich, I. F.; Ivashin, N. V.; Sinyakov, G. N.; Шульга, А. М.; Терехов, С. Н.; Filatov, I. V.; Dzilinski, K.

doi:10.1016/0022-2860(88)87026-1

Cited by 28 publications

(12 citation statements)

References 33 publications

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“…Addition of a second electron was studied by adjusting the potential to -1.51 V. This resulted in a new product (Table 5), but, as already suggested by the voltammetry, neutral NiP* could not be recovered even when the potential was returned to 0 V. The free base H 2 P* also gave excellent quality OTTLE spectra, and the anionic product gave a spectrum analogous to that of the nickel(II) complex, with additional bands due to the lower symmetry of the free base. These monomer anions have spectra similar to those reported in the literature for authenticated porphyrin radical anions [61,[70][71][72]. The similarity of the [NiP*] 1À and [H 2 P*] 1À spectra confirms that the site of first reduction in NiOEP complexes bearing meso-alkynyl substituents (whether dimers or monomers) is the macrocyclic psystem and not the metal ion.…”

Section: Spectra Of the Electrogenerated Anions And Dianionssupporting

confidence: 78%

Porphyrin Dimers Linked by Conjugated Butadiyne Bridges: Preparations, Spectra, Voltammetry and Reductive Spectroelectrochemistry of {[M(OEP)](μ-C₄)[M(OEP)]}(M₂≡H₄, Co₂, Ni₂, Cu₂, Zn₂, Pd₂, Pt₂, Co/Ni, Ni

Arnold

Heath

James

1999

J. Porphyrins Phthalocyanines

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A series of derivatives M 2 P 2 ( M 2 ≡ H 4, Co 2, Ni 2, Cu 2, Zn 2, Pd 2, Pt 2, Co / Ni , Ni / Cu , Ni / Zn ) of the ligand meso,meso′-bis(octaethylporphyrinyl)butadiyne has been prepared and characterized by 1 H NMR, FT Raman and visible absorption spectroscopies as well as by cyclic and a.c. voltammetry in CH 2 Cl 2 solution at 20 and −40 °C. The electronic spectra exhibit multiple Soret bands and the voltammetry reveals successive one-electron reductions indicating the accessibility of ‘mixed valence’ π-radical anions and π-dianions. Using in situ thin layer spectroelectrochemistry, the UV to near-IR spectra of [ M 2 P 2]1− and [ M 2 P 2]2− ( M as above) were recorded at ≤ −40 °C. Apart from the Co complexes (reduced at the metal ion), the bis(porphyrin) anions have spectra which include sharp, intense near-IR bands (ε = 50 000–200 000 M−1cm−1) at c. 4500 and 11 500 cm−1([ M 2 P 2]1−) and 9500 cm−1([ M 2 P 2]2−). An empirically constructed semiquantitative frontier orbital model explains the observed electronic absorption bands. Inter-porphyrin conjugation, mediated by the butadiyne bridge, is responsible for the Soret band multiplicity. The near-IR bands of the anions are assigned to long-axis polarized π → π* transitions within the newly occupied upper manifold of the two-porphyrin eight-orbital framework. The small comproportionation constants found for the diporphyrin monoanions contradict the usual assumption that electronically coupled dimers should have a large voltammetric separation between the first and second redox steps.

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Section: Spectra Of the Electrogenerated Anions And Dianionssupporting

confidence: 78%

Porphyrin Dimers Linked by Conjugated Butadiyne Bridges: Preparations, Spectra, Voltammetry and Reductive Spectroelectrochemistry of {[M(OEP)](μ-C₄)[M(OEP)]}(M₂≡H₄, Co₂, Ni₂, Cu₂, Zn₂, Pd₂, Pt₂, Co/Ni, Ni

Arnold

Heath

James

1999

J. Porphyrins Phthalocyanines

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“…Reduced forms of iron porphyrins play an essential role as intermediate products in the reduction−oxidation bioprocesses which modulate the course of reactions running with participation of the electron transfer. The reduction process of iron porphyrins runs in a more complex way in comparison, for example, with the Mg-or Zn-porphyrins [4], because additional electrons, joined to an iron porphyrin molecule can occupy d-orbitals of the…”

Section: Introductionmentioning

confidence: 99%

Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex

2015

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“…[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Most RR studies of tetrapyrrolic radicals have focused on prophyrin model c~mplexes.~-~*' '-17 Relatively few RR studies have been reported for the radical ions of natural photosynthetic pigments.18-21 Most of these latter efforts have been directed at radical cations. Cotton and co-workers examined the cations of the green plant pigment chlorophyll a (Chl) and several structurally related complexes.ls Both Lutz and co-workers20 and Cotton et al19 reported RR spectra of the radical cation of the bacterial photosynthetic pigment bacteriochlorophyll a (BCh).…”

Section: Introductionmentioning

confidence: 99%

Resonance Raman Spectra of the Anion and Cation Radicals of Bacterial Photosynthetic Pigments

Diers¹,

Bocian²

1994

J. Phys. Chem.

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Resonance Raman (RR) spectra are reported for the radical ions of the bacterial photosynthetic pigments bacteriochlorophyll a (BCh) and its metal-free analog bacteriopheophytin a (BPh). The radical anions, BChand BPh-, were the primary focus of the RR study; however, the radical cation, BCh+, was also examined.The RR data for all the radical species were acquired by using a variety of excitation wavelengths in the UV-violet region. Data were also obtained for BCh+ and BCh-in solvents in which the Mg(I1) ion axially coordinates either one or two solvent molecules. The RR data for the radical ions suggest that oxidation/ reduction results in characteristic frequency shifts for the carbonyl and ring skeletal modes of the bacteriochlorin macrocycles. These frequency shifts provide benchmarks for the characterization of transient radicals in vivo via time-resolved vibrational spectroscopy. The oxidatiodreduction-induced frequency shifts observed for BPh and BCh are indicative of significant structural and/or electronic perturbations of the bacteriochlorin macrocycle. The C9=0 and the C2,=0 groups appear to be the key structural elements in these perturbations.The RR data further suggest that oxidationheduction alters the forms of the vibrational eigenvectors of the carbonyl and ring skeletal modes. This in turn suggests that the relationship between the vibrational frequency shifts and structural and/or electronic perturbations is governed by the interplay of a number of subtle factors. Comparison of the RR data for the radical species in solution with those obtained from reaction center proteins suggests that the pigment-protein interactions may be significantly affected by catiodanion formation. Collectively, the RR data suggest that oxidationheduction-induced changes in pigment-protein interactions could provide a means of mediating the redox properties of BCh and BPh in vivo.

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Electronic structure of metalloporphyrin π-anions

Cited by 28 publications

References 33 publications

Porphyrin Dimers Linked by Conjugated Butadiyne Bridges: Preparations, Spectra, Voltammetry and Reductive Spectroelectrochemistry of {[M(OEP)](μ-C₄)[M(OEP)]}(M₂≡H₄, Co₂, Ni₂, Cu₂, Zn₂, Pd₂, Pt₂, Co/Ni, Ni

Porphyrin Dimers Linked by Conjugated Butadiyne Bridges: Preparations, Spectra, Voltammetry and Reductive Spectroelectrochemistry of {[M(OEP)](μ-C₄)[M(OEP)]}(M₂≡H₄, Co₂, Ni₂, Cu₂, Zn₂, Pd₂, Pt₂, Co/Ni, Ni

Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex

Resonance Raman Spectra of the Anion and Cation Radicals of Bacterial Photosynthetic Pigments

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Electronic structure of metalloporphyrin π-anions

Cited by 28 publications

References 33 publications

Porphyrin Dimers Linked by Conjugated Butadiyne Bridges: Preparations, Spectra, Voltammetry and Reductive Spectroelectrochemistry of {[M(OEP)](μ-C4)[M(OEP)]}(M2≡H4, Co2, Ni2, Cu2, Zn2, Pd2, Pt2, Co/Ni, Ni

Porphyrin Dimers Linked by Conjugated Butadiyne Bridges: Preparations, Spectra, Voltammetry and Reductive Spectroelectrochemistry of {[M(OEP)](μ-C4)[M(OEP)]}(M2≡H4, Co2, Ni2, Cu2, Zn2, Pd2, Pt2, Co/Ni, Ni

Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex

Resonance Raman Spectra of the Anion and Cation Radicals of Bacterial Photosynthetic Pigments

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Porphyrin Dimers Linked by Conjugated Butadiyne Bridges: Preparations, Spectra, Voltammetry and Reductive Spectroelectrochemistry of {[M(OEP)](μ-C₄)[M(OEP)]}(M₂≡H₄, Co₂, Ni₂, Cu₂, Zn₂, Pd₂, Pt₂, Co/Ni, Ni

Porphyrin Dimers Linked by Conjugated Butadiyne Bridges: Preparations, Spectra, Voltammetry and Reductive Spectroelectrochemistry of {[M(OEP)](μ-C₄)[M(OEP)]}(M₂≡H₄, Co₂, Ni₂, Cu₂, Zn₂, Pd₂, Pt₂, Co/Ni, Ni