Cis-dicarbonyl binding at cobalt and iron porphyrins with saddle-shape conformation

Seufert, Knud; Bocquet, Marie‐Laure; Auwärter, Willi; Weber‐Bargioni, Alexander; Reichert, Joachim; Lorente, Nicolás; Barth, Johannes V.

doi:10.1038/nchem.956

Cited by 100 publications

(127 citation statements)

References 38 publications

(36 reference statements)

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“…Similarly to MnPc, the CO-coordinated molecules exhibit fourfold symmetry, with a central protrusion appearing 0.8 Å higher than in the case of MnPc, indicating that a single CO molecule bonds directly to the transition metal ion. We find only singly coordinated CO-MnPc, contrary to previous studies reporting doubly coordinated porphyrin molecules [13,14].…”

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confidence: 55%

Reversible Change of the Spin State in a Manganese Phthalocyanine by Coordination of CO Molecule

et al. 2012

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We show that the magnetic state of individual manganese phthalocyanine (MnPc) molecules on a Bi(110) surface is modified when the Mn2þ center coordinates to CO molecules adsorbed on top. Using scanning tunneling spectroscopy we identified this change in magnetic properties from the broadening of a Kondo-related zero-bias anomaly when the CO-MnPc complex is formed. The original magnetic state can be recovered by selective desorption of individual CO molecules. First principles calculations show that the CO molecule reduces the spin of the adsorbed MnPc from S ¼ 1 to S ¼ 1=2 and strongly modifies the respective screening channels, driving a transition from an underscreened Kondo state to a state of mixed valence. DOI: 10.1103/PhysRevLett.109.147202 PACS numbers: 75.20.Hr, 68.37.Ef, 82.37.Gk, 68.43.Bc Control over the magnetic moment of a molecule and its interaction with a substrate is a key issue in the emerging field of molecular spintronics [1]. In metal-phthalocyanines and metal-porphyrins the metal center is usually coordinatively unsaturated and presents a local reactive site, which opens a unique possibility of controlling the magnetic moment in situ by external chemical stimuli [2][3][4][5][6][7][8]. The axial coordination of small molecules like CO, NO or O 2 to those complexes substantially alters their electronic properties, which has led to a successful implementation of phthalocyanines and porphyrins in gas sensors [9,10]. Studies specifically addressing the magnetic state are, however, scarce. Only recently it has been shown that the attachment of a NO molecule to a cobalt-tetraphenylporphyrin (CoTPP) quenches its spin due to the oxidation process [6]. The general picture is however more complicated, as the chemical bond to the reactant molecule causes the redistribution of charge in the d orbitals of the metal center and modifies the ligand field of the metal ion. This has critical consequences for the magnetic ground state of the complex [7,8]. On metal surfaces, the formation of a new ligand bond may additionally alter the hybridization of molecular and substrate states, thus affecting the electronic and magnetic coupling of the metal ion to the substrate [3][4][5]. Understanding the response of these effects to the change in chemical coordination is crucial to gain full control over the functionality of the magnetic system.Here, we show that the magnetic moment of a manganese phthalocyanine (MnPc) molecule [see Fig. 1(a)] on a Bi(110) surface is reduced when coordinated to a CO molecule. Using a combination of a low temperature scanning tunneling microscopy (STM) and density functional theory (DFT) we find, first, that the spin of the MnPc molecule is reduced from S ¼ 3=2 to S ¼ 1 upon adsorption and, second, that CO further reduces the spin of the MnPc from S ¼ 1 to S ¼ 1=2. The change in the magnetic ground state upon CO attachment is detected by the broadening of a characteristic zero-bias anomaly (ZBA). We interpret this broadening as a transition from a Kondo regime, for the bare MnPc on...

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confidence: 55%

Reversible Change of the Spin State in a Manganese Phthalocyanine by Coordination of CO Molecule

et al. 2012

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“…The response to elevated exogenous or endogenous CO may in part be a consequence of the interaction of CO with metalloporphyrins with iron or cobalt centers, which include vitamin B 12 (24). This could offer an explanation for increased expression of DVU0997 (metE), coding for a vitamin B 12 -independent methionine synthase ( Table 1; Fig.…”

Section: Vulgarismentioning

confidence: 99%

Deletion of the Desulfovibrio vulgaris Carbon Monoxide Sensor Invokes Global Changes in Transcription

et al. 2012

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The carbon monoxide-sensing transcriptional factor CooA has been studied only in hydrogenogenic organisms that can grow using CO as the sole source of energy. Homologs for the canonical CO oxidation system, including CooA, CO dehydrogenase (CODH), and a CO-dependent Coo hydrogenase, are present in the sulfate-reducing bacterium Desulfovibrio vulgaris, although it grows only poorly on CO. We show that D. vulgaris Hildenborough has an active CO dehydrogenase capable of consuming exogenous CO and that the expression of the CO dehydrogenase, but not that of a gene annotated as encoding a Coo hydrogenase, is dependent on both CO and CooA. Carbon monoxide did not act as a general metabolic inhibitor, since growth of a strain deleted for cooA was inhibited by CO on lactate-sulfate but not pyruvate-sulfate. While the deletion strain did not accumulate CO in excess, as would have been expected if CooA were important in the cycling of CO as a metabolic intermediate, global transcriptional analyses suggested that CooA and CODH are used during normal metabolism. Desulfovibrio organisms are sulfate-reducing bacteria that use organic acids, alcohols, or molecular hydrogen as electron donors to reduce sulfate (22). When these bacteria grow on organic acids or alcohols, energy generation is hypothesized to be derived in part through hydrogen cycling (20). Hydrogen cycling posits that reducing equivalents formed during oxidation of the electron donor in the cytoplasm are shuttled to form hydrogen, which is then oxidized in the periplasm to generate electrons for sulfate reduction and to generate a proton motive force. This mechanism for energy recovery offers an explanation for the hydrogen burst observed during the early growth phase in batch culture (15,19,20,28). Desulfovibrio vulgaris Hildenborough appears well equipped to carry out this hydrogen cycling, possessing an array of six predicted hydrogenases-four localized periplasmically (Hyd, Hyn1, Hyn2, and Hys) and two membrane-bound enzymes facing the cytoplasm (Coo and Ech) (12). There is also some evidence suggesting that, in addition to hydrogen, carbon monoxide functions as either a growth substrate or an intermediate in energy metabolism (16,29).With the exception of some Desulfotomaculum species that can grow in Ͼ50% CO, CO is toxic at concentrations of Ͻ20% to most sulfate-reducing bacteria (21). CO toxicity is likely to be a result of inhibition of hydrogenases or other metalloenzymes (21). CO has been demonstrated to be both produced and consumed by Desulfovibrio spp. CO production has been documented during growth of both D. vulgaris Hildenborough (29) and D. vulgaris Madison (16) on lactate-sulfate or pyruvate-sulfate, with greater accumulation in a D. vulgaris Hildenborough hyd mutant lacking the periplasmic Fe hydrogenase (29). Consumption was demonstrated in D. vulgaris strain Madison. This organism grew on a headspace of 4% CO as the sole energy source and tolerated a headspace of 4.5% CO while growing on organic acids, consistent with the presence of an acti...

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“…1a) combined with near-edge x-ray absorption spectroscopy data (Fig. S1, Supplementary Information) demonstrate that upon adsorption on the Ag(111) surface, the 2H-TPP adapts to a saddle-shaped macrocycle geometry with pairs of opposite pyrrole rings tilted upwards (α-pyr) or downwards (κ-pyr) 18,28 , respectively (Fig. 1b).…”

mentioning

confidence: 99%

A surface-anchored molecular four-level conductance switch based on single proton transfer

et al. 2011

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The development of a variety of nanoscale applications 1, 2 requires the fabrication and control of atomic [3][4][5] or molecular switches 6, 7 that can be reversibly operated by light 8 , a short range force 9, 10 , electric current 11,12 or some other external stimulus [13][14][15] . In order for such molecules to be used as electronic components, they should be directly Fig. 1d and f) at ambient temperatures, the process being called tautomerization 24,

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Cis-dicarbonyl binding at cobalt and iron porphyrins with saddle-shape conformation

Cited by 100 publications

References 38 publications

Reversible Change of the Spin State in a Manganese Phthalocyanine by Coordination of CO Molecule

Reversible Change of the Spin State in a Manganese Phthalocyanine by Coordination of CO Molecule

Deletion of the Desulfovibrio vulgaris Carbon Monoxide Sensor Invokes Global Changes in Transcription

A surface-anchored molecular four-level conductance switch based on single proton transfer

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