Mono- and biscarbonyl complexes of iron(II) tetraphenylporphyrin

Wayland, Bradford B.; Mehne, Larry F.; Swartz, James E.

doi:10.1021/ja00476a020

Cited by 67 publications

(41 citation statements)

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“…Accordingly, stretch modes of the CO ligand are likely to be the origin of the bands observed at high wavenumbers. The broad TER band centred at 2045 cm −1 can be interpreted as due to ν CO with help of literature results: Values reported for ν CO in porphyrin–CO axial complexes vary between 2075 cm −1 for CoTPP in Ar/Kr matrices at low temperature,26 2042 cm −1 for FeTPP in Nujol at room temperature,27 and 2005 cm −1 for RuTPP in dried benzene 28. For the di‐carbonyl complexes [Me(CO) 2 ], the CO stretch bands were found at 70 to 90 cm −1 lower frequencies in the latter two studies, as expected on the basis of competition of trans ligands for the metal orbitals 28.…”

Section: Resultsmentioning

confidence: 64%

In Situ Discrimination between Axially Complexed and Ligand‐Free Co Porphyrin on Au(111) with Tip‐Enhanced Raman Spectroscopy

Domke

Pettinger

2009

ChemPhysChem

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Simultaneous chemical and topographic information about cobalt tetraphenyl-porphyrin (CoTPP) adlayers formed on a Au(111) single crystal is obtained with tip-enhanced Raman (TER) spectroscopy. We distinguish in situ between sample areas covered with an ordered adlayer of CoTPP and areas covered with a spontaneously formed disordered phase. The Raman vibrational fingerprints collected from the nanometer-sized near-field region just below a scanning tunnelling microscope (STM) tip are correlated with the adsorbate structures seen in the STM images. We assign the TER spectral features of the disordered phase to CoTPP complexes with CO and/or NO axial ligands, whereas the TER spectrum obtained from the ordered phase does not show any indication of additional axial complexation of CoTPP.

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Section: Resultsmentioning

confidence: 64%

In Situ Discrimination between Axially Complexed and Ligand‐Free Co Porphyrin on Au(111) with Tip‐Enhanced Raman Spectroscopy

Domke

Pettinger

2009

ChemPhysChem

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“…Previously, Wayland et al15 observed in the solid state the ν(CO) of Fe(CO) 2 TPP and FeCOTPP at 2042 and 1973 cm -1 , respectively. They also found the equilibrium constant for the formation of the monoadduct and the biscarbonyl adduct to be 6.6 10 4 and 140, respectively.…”

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confidence: 93%

Infrared Spectra of RuTPP, RuCOTPP, and Ru(CO)₂TPP Isolated in Solid Argon

et al. 2005

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Infrared spectra of unstable species such as CO-free ruthenium tetraphenylporphyrin RuTPP and RuCOTPP (species with vacant coordination sites) isolated in solid argon at 8 K have been recorded. Selective deposition conditions allow the isolation of either RuTPP and RuCOTPP or RuCOTPP and Ru(CO)2TPP. This depends on the preparation conditions of the sample. A specific Ru-CO bending mode has been characterized at 590.1 cm(-1) for Ru(CO)2TPP. The behavior of each vibrational mode of RuTPP, RuCOTPP, and Ru(CO)2TPP has been analyzed. Modes such as gamma8 at 721.3 cm(-1) (out-of-plane stretching mode gamma(Cbeta-H)sym) and nu41 at 1342.8 cm(-1) (nuCalpha-N coupled with deltaCalpha-Cm) reflect the charge transfer in the porphyrin. Indeed, the addition of one or two CO ligands to RuTPP reduces the charge transfer between the metal center and the porphyrin, which appears as an increase in the frequency of the nu41 mode and in a decrease in that of the gamma8 mode.

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“…Unlike ir-acceptor ligands such as CO, nitrogenous ligands act primarily as a donors. Indeed, the recent observation that the monoadduct Fe(TPP)(CO) is low-spin, whereas the Fe(TPP)(B) complexes are thought to be high spin, has been attributed to the enhanced 7r-accepting characteristics of CO as compared to base B (32). If ir back-bonding does not contribute to the Fe-B bond strength, then the above discussion indicates that the porphyrin (7rf*ir*) excitation should not cause the photolabilization of B.…”

Section: Methodsmentioning

confidence: 99%

On the photosensitivity of liganded hemoproteins and their metal-substituted analogues.

Hoffman¹,

Gibson²

1978

Proc. Natl. Acad. Sci. U.S.A.

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We have examined the photosensitivity of low-spin liganded hemoglobin, myoglobin, and peroxidase, and their metal-substituted analogues, using three different metals (Fe, Mn, Co) in several oxidation states and employing a variety of diatomic or pseudo-diatomic ligands (L). We have discovered a number of photosensitive systems, and present an overall stereo-electronic classification scheme for these photodissociation reactions: Linear, formally d6, metal-ligand fragments [e.g., HbCO (4,5), and isocyanide-hemes show a high quantum yield for photodissociation (-I) (Q. H. Gibson, unpublished data) in contrast to a lowered value for isocyanidehemoproteins (3). This has compounded the difficulty in isolating those factors that control the quantum yield for ligand photorelease by a metalloporphyrin.In our studies of metal-substituted hemoglobins (MHb) we noted that MnHbNO and HbCO are isoelectronic, and we proceeded to confirm the resulting expectation that NO would be readily photodissociated from the manganese protein, despite the minimal photolability of HbNO (8,9). Encouraged by this observation, we speculated that the variation in photodissociation quantum yields might be general, and might represent a stereo-electronic discrimination in which MHb(L) systems with a linear, formally d6, metal-ligand fragment [e.g., Fe(II) + CO; Mn(II) + NO] would be highly photodissociable, but systems with a bent fragment and higher electron occupancy [e.g., Fe(II) + 02; Fe(ii) + NO] would be relatively photoinert. This speculation has prompted us to undertake a broader study of the axial-ligand photodissociation from lowspin metalloporphyrins. We have primarily employed liganded Hb and Mb, and their metal-substituted analogues as a chemically flexible experimental system in which nitrogen atoms of the porphyrin and proximal imidazole occupy five coordination sites of a first transition series metal ion, and the sixth site is occupied by a reversibly bound diatomic or pseudodiatomic ligand, L.We here discuss flash photolysis photodissociation measurements for a large number of such systems, many previously unexamined. The results so far confirm the occurrence of a dichotomy in the values of (0L, which we show to reflect the geometry and electronic structure of the metal-ligand linkage and which appears to correlate with features of the optical spectra. MATERIALS AND METHODSHemoglobin and its liganded derivatives were prepared by published procedures, as were metal-substituted hemoglobins and their derivatives (8,9). Ligand photodissociation was observed spectrophotometrically after flash photolysis. The samples were exposed to light from a Multiblitz III electronic flash with 100-J energy input, and flash duration, (l/e) -400 Asec. The optical absorption spectra of low-spin liganded MPor and MHb and MMb are typically dominated by porphyrincentered transitions, the Soret band in the vicinity of 400 nm (E of order 105), and the a-f bands in the vicinity of 550 nm (E of order 104) (see refs. 10 and 11). The photoflash w...

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Mono- and biscarbonyl complexes of iron(II) tetraphenylporphyrin

Cited by 67 publications

References 1 publication

In Situ Discrimination between Axially Complexed and Ligand‐Free Co Porphyrin on Au(111) with Tip‐Enhanced Raman Spectroscopy

In Situ Discrimination between Axially Complexed and Ligand‐Free Co Porphyrin on Au(111) with Tip‐Enhanced Raman Spectroscopy

Infrared Spectra of RuTPP, RuCOTPP, and Ru(CO)₂TPP Isolated in Solid Argon

On the photosensitivity of liganded hemoproteins and their metal-substituted analogues.

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Mono- and biscarbonyl complexes of iron(II) tetraphenylporphyrin

Cited by 67 publications

References 1 publication

In Situ Discrimination between Axially Complexed and Ligand‐Free Co Porphyrin on Au(111) with Tip‐Enhanced Raman Spectroscopy

In Situ Discrimination between Axially Complexed and Ligand‐Free Co Porphyrin on Au(111) with Tip‐Enhanced Raman Spectroscopy

Infrared Spectra of RuTPP, RuCOTPP, and Ru(CO)2TPP Isolated in Solid Argon

On the photosensitivity of liganded hemoproteins and their metal-substituted analogues.

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Infrared Spectra of RuTPP, RuCOTPP, and Ru(CO)₂TPP Isolated in Solid Argon