<i>The Theory of the Transition-Metal Ions</i>

Griffith, J. S.; Roberts, Louis D.

doi:10.1063/1.3057810

Cited by 776 publications

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“…the heme iron would then be bound to the 4 nitrogen atoms of heme c and one nitrogen atom of imidazole of the axial histidine-18 [ 16]. This explanation of the paramagnetism in reduced CM-Cyt c is further supported by theoretical considerations [6] and by observations in "inorganic complexes" [7] which show that systems with the electronic configuration nd 6 tend to take on the low spin state even in relatively weak ligand fields. Also the closely related properties of the heme iron in CM-Cyt c and deoxymyoglobin, in particular the ability to bind 02, CO, CN-and other small molecules at neutral pH, would then be understandable.…”

Section: Results and Discussionmentioning

confidence: 95%

Evidence for pentacoordinated iron (II) in carboxymethylated cytochromec

Keller¹,

Aviram

Schejter

et al. 1972

FEBS Letters

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Section: Results and Discussionmentioning

confidence: 95%

Evidence for pentacoordinated iron (II) in carboxymethylated cytochromec

Keller¹,

Aviram

Schejter

et al. 1972

FEBS Letters

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“…They determine the optical properties of the complex in the UV−visible spectral region. CT excitations involve the nominal water orbitals and correspond to transitions from 3 A 2g (e g ,t 2g ) 10 (t 2g * ,e g *) 8 to states of the (e g ,t 2g ) 9 (t 2g * ,e g *) 9 configuration.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…6 While the structure of 3d transition metal (TM) ions and their complexes in aqueous solution can be addressed experimentally with numerous scattering and spectroscopic methods, 7 bonding can be assessed with a limited set of spectroscopic tools among which, historically, UV−vis spectroscopy has played a dominant role. Complementing such experimental results and due to the strongly polarized character of the coordinate bond, ligand-field theory 8,9 can be successfully applied to hexaaqua complexes. In particular, the dependence of the ligand-field (LF) state energies on ligand-field strength and 3d−3d Coulomb interactions for all 3d n complexes were first calculated by Tanabe and Sugano in their seminal work from 1954.…”

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confidence: 99%

From Ligand Fields to Molecular Orbitals: Probing the Local Valence Electronic Structure of Ni²⁺ in Aqueous Solution with Resonant Inelastic X-ray Scattering

et al. 2013

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Bonding of the Ni 2+ (aq) complex is investigated with an unprecedented combination of resonant inelastic X-ray scattering (RIXS) measurements and ab initio calculations at the Ni L absorption edge. The spectra directly reflect the relative energies of the ligand-field and charge-transfer valence-excited states. They give element-specific access with atomic resolution to the ground-state electronic structure of the complex and allow quantification of ligand-field strength and 3d−3d electron correlation interactions in the Ni 2+ (aq) complex. The experimentally determined ligand-field strength is 10Dq = 1.1 eV. This and the Racah parameters characterizing 3d−3d Coulomb interactions B = 0.13 eV and C = 0.42 eV as readily derived from the measured energies match very well with the results from UV−vis spectroscopy. Our results demonstrate how L-edge RIXS can be used to complement existing spectroscopic tools for the investigation of bonding in 3d transition-metal coordination compounds in solution. The ab initio RASPT2 calculation is successfully used to simulate the L-edge RIXS spectra. ■ INTRODUCTION3d transition metals in aqueous solution are interesting from a fundamental point of view as their hexaaqua complexes [M(H 2 O) 6 ] n+ represent the archetype of Werner complexes with coordinative bonding in octahedral symmetry. 1 Considering hydrogen bonding between the various coordination spheres of water molecules, they could even be regarded as chelate complexes, 2 and new insight into their electronic structure could help understanding the interplay of bonding, structure, and dynamics in these complexes. This in turn forms the basis for understanding their thermodynamic properties and reactivity, having implications for modeling and understanding phenomena ranging from water exchange reactions 3,4 to photochemical processes 5 and atmospheric liquid chemistry of 3d transition-metal ions in solution. 6 While the structure of 3d transition metal (TM) ions and their complexes in aqueous solution can be addressed experimentally with numerous scattering and spectroscopic methods, 7 bonding can be assessed with a limited set of spectroscopic tools among which, historically, UV−vis spectroscopy has played a dominant role. Complementing such experimental results and due to the strongly polarized character of the coordinate bond, ligand-field theory 8,9 can be successfully applied to hexaaqua complexes. In particular, the dependence of the ligand-field (LF) state energies on ligand-field strength and 3d−3d Coulomb interactions for all 3d n complexes were first calculated by Tanabe and Sugano in their seminal work from 1954. 10,11 The low-energy electronic excited state spectrum of a typical TM coordination complex can thus be described by, with increasing photon energy, the LF excitations, followed by the charge-transfer (CT) and ligand-centered excitations. At present, the excitations to LF states of octahedral TM complexes are very well understood at the semiempirical level of ligand-field theory. Today, ab ini...

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“…When the fact that this splitting corresponds to 6B + 2C 32 is considered, it becomes clear that this system is highly covalent. 33, 34 Upon protonation of the nitrido complexes the (n f π*) transition shifts to lower energy (518 nm); moreover, its intensity decreases considerably. The low-energy shift can be explained by a weaker π-antibonding interaction between the metal d xz /d yz orbitals and the p orbitals of the imido ligand, as compared to the nitrido system.…”

Section: Discussionmentioning

confidence: 99%

Electronic Structure, Spectroscopic Properties, and Reactivity of Molybdenum and Tungsten Nitrido and Imido Complexes with Diphosphine Coligands: Influence of the trans Ligand

et al. 2006

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A series of molybdenum and tungsten nitrido, [M(N)(X)(diphos) 2 ], and imido complexes, [M(NH)(X)(diphos) 2 )]Y, (M ) Mo, W) with diphosphine coligands (diphos ) dppe/depe), various trans ligands (X ) N 3 -, Cl -, NCCH 3 ) and different counterions (Y -) Cl -, BPh 4 -) is investigated. These compounds are studied by infrared and Raman spectroscopies; they are also studied with isotope-substitution and optical-absorption, as well as emission, spectroscopies. In the nitrido complexes with trans-azido and -chloro coligands, the metal−N stretch is found at about 980 cm -1 ; upon protonation, it is lowered to about 920 cm -1 . The 1 A 1 f 1 E (n f π*) electronic transition is observed for [Mo(N)(N 3 )(depe) 2 ] at 398 nm and shows a progression in the metal−N stretch of 810 cm -1 . The corresponding 3 E f 1 A (π* f n) emission band is observed at 542 nm, exhibiting a progression in the metal−N stretch of 980 cm -1 . In the imido system [Mo(NH)(N 3 )(depe) 2 ]BPh 4 , the n f π* transition is shifted to lower energy (518 nm) and markedly decreases in intensity. In the trans-nitrile complex [Mo(N)(NCCH 3 )(dppe) 2 ]BPh 4 , the metal− N(nitrido) stretching frequency increases to 1016 cm -1 . The n f π* transition now is found at 450 nm, shifting to 525 nm upon protonation. Most importantly, the reduction of this nitrido trans-nitrile complex is drastically facilitated compared to its counterparts with anionic trans-ligands (E p red ) −1.5 V vs Fc + /Fc). On the other hand, the basicity of the nitrido group is decreased (pK a {[Mo(NH)(NCCH 3 )(dppe) 2 ](BPh 4 ) 2 } ) 5). The implications of these findings with respect to the Chatt cycle are discussed.

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The Theory of the Transition-Metal Ions

Cited by 776 publications

References 0 publications

Evidence for pentacoordinated iron (II) in carboxymethylated cytochromec

Evidence for pentacoordinated iron (II) in carboxymethylated cytochromec

From Ligand Fields to Molecular Orbitals: Probing the Local Valence Electronic Structure of Ni²⁺ in Aqueous Solution with Resonant Inelastic X-ray Scattering

Electronic Structure, Spectroscopic Properties, and Reactivity of Molybdenum and Tungsten Nitrido and Imido Complexes with Diphosphine Coligands: Influence of the trans Ligand

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The Theory of the Transition-Metal Ions

Cited by 776 publications

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Evidence for pentacoordinated iron (II) in carboxymethylated cytochromec

Evidence for pentacoordinated iron (II) in carboxymethylated cytochromec

From Ligand Fields to Molecular Orbitals: Probing the Local Valence Electronic Structure of Ni2+ in Aqueous Solution with Resonant Inelastic X-ray Scattering

Electronic Structure, Spectroscopic Properties, and Reactivity of Molybdenum and Tungsten Nitrido and Imido Complexes with Diphosphine Coligands: Influence of the trans Ligand

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From Ligand Fields to Molecular Orbitals: Probing the Local Valence Electronic Structure of Ni²⁺ in Aqueous Solution with Resonant Inelastic X-ray Scattering