Nitrogen-14 nuclear quadrupole resonance spectra of the coordinated amino group and of coordinated imidazole. Crystal and molecular structures of chloroglycylglycinato(imidazole)cadmium

Ashby, Carol I. H.; Paton, W. F.; Brown, Theodore I.

doi:10.1021/ja00529a020

Cited by 55 publications

(47 citation statements)

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“…These three frequencies allow one to determine K ϭ 0.87 MHz and ϭ 0.34. The value of the quadrupole coupling constant K is close to the typical values ϳ0.75-0.85 MHz previously reported for peptide nitrogens (43)(44)(45)(46)(47). Calculation of the double-quantum transition for this nitrogen, with A ϭ 0.7 MHz and the nuclear quadrupole interaction parameters found, gives a value 3.4 MHz, consistent with the frequency observed in three-pulse S-band spectrum at g z (Fig.…”

Section: Assignment Of the Frequencies In S-band Spectra-linessupporting

confidence: 88%

“…The amide nitrogen in free peptides, such as in metal complexes of diglycine, which H-bond to the inorganic sulfur atoms of iron-sulfur clusters (43)(44)(45)(46)(47)(48), has a narrow range of quadrupole coupling constants, K ϭ 0.75-0.85 MHz, determined by the electronic structure and the geometry of the planar peptide group. This coupling constant is only slightly perturbed by hydrogen bonding, which has been confirmed by calculations of the quadrupole coupling tensor (46,50,51).…”

Section: Assignment Of the Frequencies In S-band Spectra-linesmentioning

confidence: 99%

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Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy

Dikanov

Kolling

Endeward

et al. 2006

Journal of Biological Chemistry

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Proteins containing Rieske-type [2Fe-2S] clusters with two histidyl and two cysteinyl ligands play important roles in many biological electron transfer reactions such as aerobic respiration, photosynthesis, and biodegradation of various alkene and aromatic compounds. The distinct biological functions of this protein family are in part associated with the cluster redox potential and the pK of the oxidized form, which are roughly correlated with the number of hydrogen bonds from protein side chains and the peptide backbone to the cluster and its immediate ligands (1-6).In the cytochrome bc 1 /b 6f family, a Rieske iron-sulfur protein (ISP) 4 is a constituent of the high potential electron transfer chain that accepts the first electron in the bifurcated reaction at the ubihydroquinone (quinol, QH 2 ) oxidizing Q o site. In the catalytic mechanism at the Q o site, the redox reaction involves extraction of both an electron and a proton from the bound quinol and their transfer to the ISP through a short pathway that includes the ISP His-161 ring and the H-bond between N ⑀ and the -OH of the quinol substrate (7). It has been proposed that the electron transfer is gated by the low probability of finding the H-atom of the H-bond in the kinetically favorable position, determined by the pK difference between the quinol and the oxidized ISP (ISP ox ) (reviewed in Refs. 5 and 6). The pK on ISP ox is contributed by one of the cluster ligands, His-161 in bovine numbering, and is associated with H ϩ dissociation from the N ⑀ involved in the H-bond. The gating accounts for the fact that this first electron transfer is slower by more than 3 orders of magnitude than would be expected from the short distance (ϳ7 Å) involved (6, 7). The first electron transfer is the ratedetermining step in quinol oxidation under conditions of substrate saturation. Rate determination at this reaction is demonstrated by the fact that the overall rate depends on its driving force in a classical Marcus fashion, as shown through use of mutants of the ISP with modified redox potential (6 -13). Briefly, the driving force, ⌬G o , for the first electron transfer is determined by the redox potential difference between the donor (SQ/QH 2 ) and acceptor (ISP ox /ISPH) couples. Assuming that mutations in the ISP do not change E m (SQ/QH 2 ), a change in * This work was supported by National Institutes of Health Grants GM 35438 (to A. R. C.) and GM 62954 (to S. A. D.), Fogarty Grant PHS 1 RO3 TW 01495 (to A. R. C. and R. I. S.), and National Institutes of Health/National Center for Research Resources Grant S10-RR15878 for instrumentation. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 To whom correspondence may be addressed. E-mail: dikanov@uiuc.edu. 2 Present address: Dept. of Chemistry, Princeton University, Princeton, NJ 08540. 3 To whom correspondence may be addressed. E-mail:...

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Section: Assignment Of the Frequencies In S-band Spectra-linessupporting

confidence: 88%

Section: Assignment Of the Frequencies In S-band Spectra-linesmentioning

confidence: 99%

Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy

Dikanov

Kolling

Endeward

et al. 2006

Journal of Biological Chemistry

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“…Cd À O bond distances of 2.241(4)-2.598(4) are consistent with expected values. [20] Both Cd1 and Cd2 exist as dimers that serve as 6-connected, 6-c, molecular building blocks (MBBs),…”

mentioning

confidence: 99%

Post‐Synthetic Modification of Porphyrin‐Encapsulating Metal–Organic Materials by Cooperative Addition of Inorganic Salts to Enhance CO₂/CH₄ Selectivity

et al. 2012

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Porous metal-organic materials (MOMs) that incorporate porphyrins can combine the physicochemical properties of the porphyrin [1, 2] while retaining the permanent porosity [3] of the MOM, thereby facilitating gas storage, [4] separations, [5] and luminescence. [6] There are two established approaches to incorporate porphyrins into MOMs: the use of functionalized porphyrins as nodes or linkers, [7] porphMOMs; selective encapsulation of porphyrins into cages, porph@MOMs. [8] PorphMOMs are relatively well studied and their properties have been of interest in the context of gas sorption and catalysis.[9] Porph@MOMs have been limited by the dearth of MOMs with suitable cages and until very recently there were just three examples.[8] The use of porphyrins as structure directing agents (SDAs) to template porph@MOMs with hitherto unknown MOMs has afforded a series of porph@-MOMs in which porphyrin moieties are trapped in a "ship-ina-bottle" fashion. [4,10] That porph@MOMs are now readily available affords an opportunity to fine-tune their structure and properties through either pre-synthetic design or post-synthetic modification (PSM). [11,12] PSM typically involves condensation [11] or coordination chemistry [12] and in effect turns MOMs that are amenable to PSM into platforms for the study of structurefunction relationships. Computational and experimental studies [13] have indicated that PSM by over-exchange with metal ions alters the affinity of a MOM for guest molecules and thereby enables improved H 2 or CO 2 uptake. [14] PSM that introduces metal ions has been accomplished as follows: a) exchange of guest molecules or organic cations with metal ions (Scheme 1 a); [15] b) exchange of a hydroxy proton for a Li cation (Scheme 1 b); [16] c) chemical reduction of a MOM with a reductive metal, such as Li (Scheme 1 c).[17] For example, Hupp et al. reported that the incorporation of Li + ions into metal-organic frameworks (MOFs) by either chemical reduction or cation exchange enhances the isosteric heats of adsorption (Q st ) for both H 2 and CO 2 . [16,18] However, detailed characterization of the composition and structure of such PSM materials has been hampered by the highly disordered nature of the added cations and/or the non-stoichiometric loading of the metal cations. Herein, we describe a new approach to PSM that exploits a porph@MOM with cation and anion binding sites that enable stoichiometric addition of metal salts. Specifically, immersing single crystals of a new cadmium-based porph@MOM, porph@MOM-11, into MeOH solutions of metal chloride salts leads to coordination of metal ions to the walls of the MOM and binding of Cl À ions to the metalloporphyrin moieties (Scheme 1 d).Dark green prismatic crystals of porph@MOM-11 were harvested from the reaction of biphenyl-3,4',5-tricarboxylate

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“…As it has been shown in related studies (27) the NQCC parameters at the coordinated N atom are sensitive indicators of binding to the metal center, so that rather detailed inferences regarding the extent of electron transfer can be obtained from the NQR data of this nucleus.…”

Section: Resultsmentioning

confidence: 99%

Electronic structure characterization of Fe^III-protoporphyrin IX (Fe^III-PPIX) and β-hematin using calculated nuclear quadrupole resonance (NQR) and Mössbauer parameters

Rafiee¹,

Hadipour²

2008

Can. J. Chem.

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In this work, we performed the ab initio calculation of quadrupolar parameters of 17 O and 14 N atoms in Fe III -protoporphyrin IX (Fe III -PPIX) and β-hematin molecules. Furthermore, the quadrupole splitting of iron atoms in these molecules were calculated. The calculations were carried out to explore the differences between the electronic structures of Fe III -PPIX and β-hematin. The results show that the value of quadrupole splitting of iron atom, ∆( 57 Fe), in Fe III -PPIX is exactly three-fold of its value in β-hematin. The electric field gradient (EFG) at the site of quadrupolar nuclei were calculated to obtain quadupolar parameters (χ , η, and ∆), using B3LYP method and an all-electron representation for iron (62111111/3311111/3111), as well as the 6-31G* basis for all other atoms.Résumé : Dans ce travail, on a effectué des calculs ab initio de paramètres quadripolaires des atomes de 17 O et de 14 N dans les molécules de la Fe(III)-protoporphyrine IX et de la β-hématine. On a calculé de plus le dédoublement quadripolaire des atomes de fer dans ces molécules. On a effectué les calculs afin d'explorer les différences entre les structures électroniques de la Fe(III)-protoporphyrine IX et de la β-hématine. Les résultats montrent que la valeur du couplage quadripolaire de l'atome de fer, ∆( 57 Fe), dans la Fe(III)-protoporphyrine IX est exactement trois fois plus élevée que dans la β-hématine. En faisant appel à la méthode B3LYP et à la représentation de tous les électrons de Wachter pour le fer (62111111/3311111/4111) ainsi qu'à une base 6-31G* pour tous les autres atomes, on a aussi calculé le gradient du champ électrique (GCE) au niveau du noyau quadripolaire dans le but d'obtenir les paramètres quadripolai χ, η, reset ∆.

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Nitrogen-14 nuclear quadrupole resonance spectra of the coordinated amino group and of coordinated imidazole. Crystal and molecular structures of chloroglycylglycinato(imidazole)cadmium

Cited by 55 publications

References 4 publications

Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy

Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy

Post‐Synthetic Modification of Porphyrin‐Encapsulating Metal–Organic Materials by Cooperative Addition of Inorganic Salts to Enhance CO₂/CH₄ Selectivity

Electronic structure characterization of Fe^III-protoporphyrin IX (Fe^III-PPIX) and β-hematin using calculated nuclear quadrupole resonance (NQR) and Mössbauer parameters

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Nitrogen-14 nuclear quadrupole resonance spectra of the coordinated amino group and of coordinated imidazole. Crystal and molecular structures of chloroglycylglycinato(imidazole)cadmium

Cited by 55 publications

References 4 publications

Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy

Identification of Hydrogen Bonds to the Rieske Cluster through the Weakly Coupled Nitrogens Detected by Electron Spin Echo Envelope Modulation Spectroscopy

Post‐Synthetic Modification of Porphyrin‐Encapsulating Metal–Organic Materials by Cooperative Addition of Inorganic Salts to Enhance CO2/CH4 Selectivity

Electronic structure characterization of FeIII-protoporphyrin IX (FeIII-PPIX) and β-hematin using calculated nuclear quadrupole resonance (NQR) and Mössbauer parameters

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Post‐Synthetic Modification of Porphyrin‐Encapsulating Metal–Organic Materials by Cooperative Addition of Inorganic Salts to Enhance CO₂/CH₄ Selectivity

Electronic structure characterization of Fe^III-protoporphyrin IX (Fe^III-PPIX) and β-hematin using calculated nuclear quadrupole resonance (NQR) and Mössbauer parameters