Resonance Raman studies of metal tetrakis(4-N-methylpyridyl)porphine: band assignments, structure-sensitive bands, and species equilibria

Blom, Nils; Odo, Junichi; Nakamoto, Kazuo; Strommen, Dennis P.

doi:10.1021/j100404a015

Cited by 106 publications

(83 citation statements)

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“…Figure 3 shows the RR spectrum of Co II P in water measured with 422 nm excitation and the spectra of Co III P aqueous solution with B-and Q-band excitations. The observed wavenumbers and polarization properties of the RR bands and their assignments are summarized in Table 1; assignments for Co III P are based on results reported previously 44 and on data obtained for metal tetraphenylporphyrins (M-TPP). 42,48 -50 Assignments for Co II P are analogous to those of Co III P.…”

Section: Characterization Of Co II Tmpyp(4) Versus Co Iii Tmpyp(4) Inmentioning

confidence: 99%

“…This mode is due to porphyrin and pyridinium deformation vibrations. 44 A recent normal coordinate treatment has shown that a similar band for M-TPP derivatives primarily consists of M-N pyrrole and C˛-C m bond stretching and methine bridge bending motions. 49 Our present data show that the 8 mode wavenumber is very sensitive to Co(II) !…”

Section: Rr Characterization Of Co Porphyrins: Co(ii) Versus Co(iii) mentioning

confidence: 99%

“…35 -43 Surprisingly, RR data for water-soluble Co(II) porphyrins have not yet been reported in the literature; their aqueous solutions are very unstable owing to their sensitivity to molecular oxygen dissolved in water. For Co(III) derivatives of watersoluble porphyrins, RR spectra have been published, 10,44,45 but spectroscopic characterization of their ligated species has not been carried out.…”

Section: Introductionmentioning

confidence: 99%

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Resonance Raman characterization of cationic Co(II) and Co(III) tetrakis(N‐methyl‐4‐pyridinyl)porphyrins in aqueous and non‐aqueous media

Терехов

Kruglik

Malinovskii

et al. 2003

J Raman Spectroscopy

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Resonance Raman (RR) spectra of Co(II) and Co(III) complexes of the water-soluble cationic tetrakis(Nmethyl-4-pyridinyl)porphyrin [Co II TMpyP(4), Co III TMpyP (4)] were obtained in aqueous and non-aqueous media, using both B-and Q-band excitation wavelengths. RR spectra of Co II TMpyP(4) are observed for the first time, and they are compared with those of Co III TMpyP(4). Wavenumbers of the n 2 , n 4 , n 8 and n 6 oxidation state-sensitive bands depend on pH in aqueous solution and on the nature of the solvent ( methanol, ethanol, DMF, DMSO): they lie in distinct spectral ranges for Co(II) vs Co(III) porphyrins. In addition, wavenumber shifts induced by axial ligation cover regions twofold broader for Co III TMpyP(4) than for Co II TMpyP(4). This shows that the electronic influence of axial ligands on the p-system of the macrocycle is more effective when cobalt is in a higher oxidation state. This can be due to (i) smaller axial bond lengths of Co(III) porphyrin and, hence, more efficient cobalt-axial ligand interaction as compared with Co(II) complexes, and (ii) Co III TMpyP(4) being involved in bis-adducts whereas Co II TMpyP(4) ismainly bound with only one axial ligand. The response of the porphyrin ring to the binding of axial ligands having various electron-donating-withdrawing properties was monitored by the behaviour of these oxidation-state sensitive RR bands: their shifts observed in a series of solvents were compared with Gutmann donor and acceptor numbers (DN, AN) of the solvents. A linear positive correlation was observed between Gutmann AN and n 2 , n 4 , n 8 and n 6 band wavenumbers for Co III TMpyP(4), whereas a linear negative correlation was observed for the same bands of Co II TMpyP(4) when DN increases. This means that enhanced electron-accepting properties of axial ligand result in a scarcity of cobalt d p -orbitals, which in turn leads to a decrease in p back-donation from cobalt to the porphyrin macrocycle.

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Section: Characterization Of Co II Tmpyp(4) Versus Co Iii Tmpyp(4) Inmentioning

confidence: 99%

Section: Rr Characterization Of Co Porphyrins: Co(ii) Versus Co(iii) mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Resonance Raman characterization of cationic Co(II) and Co(III) tetrakis(N‐methyl‐4‐pyridinyl)porphyrins in aqueous and non‐aqueous media

Терехов

Kruglik

Malinovskii

et al. 2003

J Raman Spectroscopy

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“…Several new conclusions are drawn regarding the (1) analytically and structurally interesting site/sequence specificity of the binding, (2) electronic excited state properties of free and bound PdP(4), (3) perturbation effects of intercalation and external binding on the porphyrin frontier (,*) MOs, and (4) orientation of bound PdP(4) in each of the three B-DNA systems. Our findings are based on a detailed analysis of MCD, CD, and optical (UV-visible) spectra measured in the analytically sensitive porphyrin Soret (B 0 ) band region (⑀ max ϳ 10 5 cm Ϫ1 M Ϫ1 ), in addition to insight gained from previous experimental (e.g., viscosity, [1][2][3][4][5][6] unwinding of supercoiled DNA, 3,6,7 footprinting, 8,9 optical, 1,3,10,11 CD, 1,3,7,10,12 flow linear dichroism (FLD), 4,5,13,14 NMR, 2,4,5,15,16 resonance Raman (RR), [17][18][19][20][21] laser-induced dichroism (LID), 22 and photoluminescence 23 ) and computational 24,25 work on these and similarly bound porphyrin systems. Use is also made of matrix method CD (mm-CD) sector rules, 26,27 based on the nondegenerate electric dipole transition moment (edtm) coupling ( e D Ϫ e DNA ) model, for interpreting the signs of DNA-induced CD bands in drugs that are achiral in the unbound state with transition energies below those of the DNA bases.…”

Section: Introductionmentioning

confidence: 99%

5,10,15,20-Tetrakis(4-N-methylpyridyl)porphyrinatopalladium(II) as a differentiation probe for sensing binding modes with B-DNA duplexes: Electronic MCD and CD spectra

Barnes¹,

Stroud²,

Robinson³

et al. 1999

Biospectroscopy

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We report our detailed electronic MCD, CD, and optical spectroscopic measurements and analysis of the porphyrin Soret (B0) region of four‐coordinate 5,10,15,20‐tetrakis(4‐N‐methylpyridyl)porphyrinatopalladium(II), PdP(4), and its bound states with B‐DNA duplexes poly(A‐T)2, poly(G‐C)2, and calf thymus DNA (CT DNA). For system PdP(4)/poly(A‐T)2 it was possible to conclude that the porphyrin is bound edge‐on in the major groove, specifically at the 5′AT3′ site. For this orientation the porphyrin's electric dipole transition moments (edtm), μx (most perturbed direction) and μy (least perturbed direction), have tilt angles α ∼ 90° and ∼ 45°, respectively, relative to the helix axis. It was further concluded from the small shifts of B0 optical and MCD band intensities and wavelengths and from the net MCD (+) A‐term sign retention upon binding that the porphyrin's frontier pπ MOs (1a1u 3a2u 4eg) are only weakly perturbed by the heterocyclic bases of poly(A‐T)2, and therefore that the LUMO (4eg) splitting is less than the |1a1u−3a2u| energy separation, ΔHOMO, that is, ΔLUMO < ΔHOMO for the bound state in PdP(4)/poly(A‐T)2. For intercalation systems PdP(4)/poly(G‐C)2 and /CT DNA, with PdP(4) centered in the intercalation “pocket” and having two of its 4‐N‐methylpyridyls extending into each of the major and minor grooves, the edtms μx and μy were determined to be oriented perpendicular (γ ∼ 0°) and parallel (γ ∼ 90°) to the hydrogen bonds of the base pairs, respectively. Intercalation is characterized by a much stronger binding interaction, viz., the B0 optical band and net MCD extrema wavelength shifts are relatively large, and the net MCD (+) A‐term of PdP(4) is substantially quenched as it becomes the (−) pseudo‐A‐term of intercalated PdP(4)/poly(G‐C)2. This A‐term sign reversal informs that the porphyrin MOs are so strongly perturbed by the GC base pairs that ΔLUMO > ΔHOMO, which gives rise to a (−) pseudo‐A‐term. Also, the findings demonstrate (1) the potential of PdP(4) as a sensitive, discriminating analytical probe of DNA sequences and (2) the diagnostic capability of the composite of five spectra [net MCD, CD, and optical of free and bound PdP(4)] in differentiating the site and sequence selectivity and preferred binding mode of this porphyrin. © 1999 John Wiley & Sons, Inc. Biospectroscopy 5: 179–188, 1999

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“…where the 8 mode is active. This mode, determined by porphyrin and pyridyl cycle deformations 44 and by methene bridge deformations, 45,46 is known as an oxidation-state marker, 47 although it is also sensitive to other parameters. As our recent investigations showed, 33 its position depends on electronic properties of axial ligands.…”

Section: Resonance Raman Measurements Co Porphyrins In Ct Dna and At-mentioning

confidence: 99%

Resonance Raman and absorption characterization of cationic Co(II)-porphyrin in its complexes with nucleic acids: binding modes, nucleic base specificity and role of water in Co(II) oxidation processes

Терехов

Galievsky

Chirvony

et al. 2005

J. Raman Spectrosc.

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A comparative study of Co(II) and Co(III) complexes of the water-soluble cationic tetrakis(N-methyl-4-pyridiniumyl)porphyrin [Co II -and Co III TMpyP(4)] with calf thymus DNA (CT DNA) and synthetic double-stranded (ds) and single-stranded (ss) polynucleotides, namely, poly(dA-dT) 2 , poly(dG-dC) 2 , [poly(dA)·poly(dT)], poly(A), poly(dT), poly(G) and poly(C) was carried out by resonance Raman (RR) as well as stationary absorption spectroscopy. It is shown that free Co II TMpyP(4) in aqueous solution is easily oxidized to Co III TMpyP(4) by dissolved molecular oxygen, but Co(II) to Co(III) oxidation ability fundamentally changes when Co II TMpyP(4) is bound to nucleic acids (NA). In double helical DNA and AT-containing polynucleotides, where the porphyrin is assumed to be outside bound mainly in the minor groove near AT sites, Co(II) is stable for weeks and even months. It is suggested that Co(II) axial ligation by immobilized water (i.e. water molecule that is hydrogen bound to O or N atoms from DNA bases) resultsin such Co II TMpyP(4) stabilization. In contrast, Co II TMpyP(4) binding with ds and ss guanine-containing polynucleotides results in instantaneous Co(II) to Co(III) transformation. This can be explained by Co ion ligation by the guanine N7 atoms, which are known to be strong electron-donating ligands. It is assumed that partial intercalation occurs when Co II TMpyP(4) is bound with poly(dG-dC) 2 , in particular, at low ionic strength values, where cobalt ion is Co(III) in character.

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Resonance Raman studies of metal tetrakis(4-N-methylpyridyl)porphine: band assignments, structure-sensitive bands, and species equilibria

Cited by 106 publications

References 1 publication

Resonance Raman characterization of cationic Co(II) and Co(III) tetrakis(N‐methyl‐4‐pyridinyl)porphyrins in aqueous and non‐aqueous media

Resonance Raman characterization of cationic Co(II) and Co(III) tetrakis(N‐methyl‐4‐pyridinyl)porphyrins in aqueous and non‐aqueous media

5,10,15,20-Tetrakis(4-N-methylpyridyl)porphyrinatopalladium(II) as a differentiation probe for sensing binding modes with B-DNA duplexes: Electronic MCD and CD spectra

Resonance Raman and absorption characterization of cationic Co(II)-porphyrin in its complexes with nucleic acids: binding modes, nucleic base specificity and role of water in Co(II) oxidation processes

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