Introduction to CFT with application to metalloporphyrins
... cytochrome P450, soluble methane monooxygenase (sMMO), peroxidases, and nitrogenase all contain iron.1,2 Both iron(II) and iron(III)-containing molecules occur in biological systems, but Nature also makes use of iron in unusual oxidation states such as +4 in key enzymatic intermediates such as the c ...
... cytochrome P450, soluble methane monooxygenase (sMMO), peroxidases, and nitrogenase all contain iron.1,2 Both iron(II) and iron(III)-containing molecules occur in biological systems, but Nature also makes use of iron in unusual oxidation states such as +4 in key enzymatic intermediates such as the c ...
Chapter 23: The Transition Elements
... The d orbital energy level diagram contains six electrons. This indicates that the metal M must have the electron configuration [Ar]3d 6 and therefore a charge of 2+ (M2+). The two complexes that have M in the 2+ oxidation state are MF64- and M(CN)64-. The d orbital energy level diagram is high spin ...
... The d orbital energy level diagram contains six electrons. This indicates that the metal M must have the electron configuration [Ar]3d 6 and therefore a charge of 2+ (M2+). The two complexes that have M in the 2+ oxidation state are MF64- and M(CN)64-. The d orbital energy level diagram is high spin ...
Electronic Structure
... _____11. The ionization energies for element X are listed in the table above. On the basis of the data, element X is most likely to be (A)Na (B)Mg (C)Al (D) Si (E) P _____12. In the periodic table, as the atomic number increases from 11 to 17, what happens to the atomic radius? (A) It remains consta ...
... _____11. The ionization energies for element X are listed in the table above. On the basis of the data, element X is most likely to be (A)Na (B)Mg (C)Al (D) Si (E) P _____12. In the periodic table, as the atomic number increases from 11 to 17, what happens to the atomic radius? (A) It remains consta ...
Effects of Axial Ligand Basicity on the Isotropic NMR
... mole in reasonable agreement with our values.17 A similar study on the same ligands coordinated to lowspin ferric tetraphenylporphyrin complexes also revealed that the shift variations with the axial ligand basicity were dominated by changes in the magnetic anisotropy. 5 However, the pseudocontact s ...
... mole in reasonable agreement with our values.17 A similar study on the same ligands coordinated to lowspin ferric tetraphenylporphyrin complexes also revealed that the shift variations with the axial ligand basicity were dominated by changes in the magnetic anisotropy. 5 However, the pseudocontact s ...
Ligand Conformation Enforces Trigonal
... is EPR silent at room temperature and 77 K, thus suggesting a strongly antiferromagnetically coupled dinuclear compound. Description of the Crystal Structure. Table 1 lists the crystallographic data for complex 1, which crystallizes as green single crystals that belong to the triclinic system, space ...
... is EPR silent at room temperature and 77 K, thus suggesting a strongly antiferromagnetically coupled dinuclear compound. Description of the Crystal Structure. Table 1 lists the crystallographic data for complex 1, which crystallizes as green single crystals that belong to the triclinic system, space ...
hexagonal ferrites - Ryerson University
... weight and density of these ions, which are higher than those of strontium ions. The replacement of Sr2+ by RE3+ ions in the hexagonal structure leads to a variation in the bonding and consequently inter atomic distance and density. ...
... weight and density of these ions, which are higher than those of strontium ions. The replacement of Sr2+ by RE3+ ions in the hexagonal structure leads to a variation in the bonding and consequently inter atomic distance and density. ...
synthesis and characterization of tetracarbonyl[6
... heterocyclic compounds. Although some organometallic compounds have been known for a long time, it is only in the last four or five decades that organometallic chemistry has come into its own and has experienced tremendous growth, both at fundamental level where our insight into the nature of chemic ...
... heterocyclic compounds. Although some organometallic compounds have been known for a long time, it is only in the last four or five decades that organometallic chemistry has come into its own and has experienced tremendous growth, both at fundamental level where our insight into the nature of chemic ...
View PDF - Oriental Journal of Chemistry
... complexes are also shown in Table (1). Molar conductivities of all synthesized complexes are measured for (1×10-3M) solution in DMSO at room temperature, Table (1). These measured values are compared with known molar conductivities27-28 which indicates that they are nonelectrolyte and consistent wit ...
... complexes are also shown in Table (1). Molar conductivities of all synthesized complexes are measured for (1×10-3M) solution in DMSO at room temperature, Table (1). These measured values are compared with known molar conductivities27-28 which indicates that they are nonelectrolyte and consistent wit ...
University of Groningen High energy spectroscopy on vanadium
... in which a strong on-site Coulomb repulsion is present, is more problematic however. In antiferromagnetic insulators such as NiO and CoO, LDA calculations [11] fail to describe the large band gap. A calculation for antiferromagnetic NiO in the LSDA approximation [22] yielded a small band gap ( 0:3 ...
... in which a strong on-site Coulomb repulsion is present, is more problematic however. In antiferromagnetic insulators such as NiO and CoO, LDA calculations [11] fail to describe the large band gap. A calculation for antiferromagnetic NiO in the LSDA approximation [22] yielded a small band gap ( 0:3 ...
FULL PAPER Cobalt(II), Nickel(II), Copper(II), and Zinc
... and elemental analyses are consistent with the formation of compounds with a 1:1 metal/ligand stoichiometry: M(ClO4)2L·2H2O [M ⫽ Co (1), Ni (2), Zn (5); Cu(ClO4)2L·4H2O (3), and CuCl2L·4H2O (4)], while a compound with a 2:1 (M/L) stoichiometric ratio was isolated with zinc chloride: Zn2Cl4L (6). IR ...
... and elemental analyses are consistent with the formation of compounds with a 1:1 metal/ligand stoichiometry: M(ClO4)2L·2H2O [M ⫽ Co (1), Ni (2), Zn (5); Cu(ClO4)2L·4H2O (3), and CuCl2L·4H2O (4)], while a compound with a 2:1 (M/L) stoichiometric ratio was isolated with zinc chloride: Zn2Cl4L (6). IR ...
IC–ICP -MS Analysis of Gadolinium-Based MRI Contrast
... The concentrations of the competing Fe 3+ and Gd 3+ ions on the polyaminopolycarboxylate ligands and thus the extent of transmetallation can be determined using the Nucleosil cation separation column. The entire ion chromatographic separation was carried out by fractionation. To this end, Fe 3+ was ...
... The concentrations of the competing Fe 3+ and Gd 3+ ions on the polyaminopolycarboxylate ligands and thus the extent of transmetallation can be determined using the Nucleosil cation separation column. The entire ion chromatographic separation was carried out by fractionation. To this end, Fe 3+ was ...
Spin crossover
Spin Crossover (SCO), sometimes referred to as spin transition or spin equilibrium behavior, is a phenomenon that occurs in some metal complexes wherein the spin state of the complex changes due to external stimuli such as a variation of temperature, pressure, light irradiation or an influence of a magnetic field.With regard to a ligand field and ligand field theory, the change in spin state is a transition from a low spin (LS) ground state electron configuration to a high spin (HS) ground state electron configuration of the metal’s d atomic orbitals (AOs), or vice versa. The magnitude of the ligand field splitting along with the pairing energy of the complex determines whether it will have a LS or HS electron configuration. A LS state occurs because the ligand field splitting (Δ) is greater than the pairing energy of the complex (which is an unfavorable process).Figure 1 is a simplified illustration of the metal’s d orbital splitting in the presence of an octahedral ligand field. A large splitting between the t2g and eg AOs requires a substantial amount of energy for the electrons to overcome the energy gap (Δ) to comply with Hund’s Rule. Therefore, electrons will fill the lower energy t2g orbitals completely before populating the higher energy eg orbitals. Conversely, a HS state occurs with weaker ligand fields and smaller orbital splitting. In this case the energy required to populate the higher levels is substantially less than the pairing energy and the electrons fill the orbitals according to Hund’s Rule by populating the higher energy orbitals before pairing with electrons in the lower lying orbitals. An example of a metal ion that can exist in either a LS or HS state is Fe3+ in an octahedral ligand field. Depending on the ligands that are coordinated to this complex the Fe3+ can attain a LS or a HS state, as in Figure 1.Spin crossover refers to the transitions between high to low, or low to high, spin states. This phenomenon is commonly observed with some first row transition metal complexes with a d4 through d7 electron configuration in an octahedral ligand geometry. Spin transition curves are a common representation of SCO phenomenon with the most commonly observed types depicted in Figure 2 in which γHS (the high-spin molar fraction) is plotted vs. T. The figure shows a gradual spin transition (left), an abrupt transition with hysteresis (middle) and a two-step transition (right). For a transition to be considered gradual, it typically takes place over a large temperature range, even up to several hundred K, whereas for a transition to be considered abrupt, it should take place within 10 K or less.These curves indicate that a spin transition has occurred in a metal complex as temperature changed. The gradual transition curve is an indication that not all metal centers within the complex are undergoing the transition at the same temperature. The abrupt spin change with hysteresis indicates a strong cooperativity, or “communication”, between neighboring metal complexes. In the latter case, the material is bistable and can exist in the two different spin states with a different range of external stimuli (temperature in this case) for the two phenomena, namely LS → HS and HS → LS. The two-step transition is relatively rare but is observed, for example, with dinuclear SCO complexes for which the spin transition in one metal center renders the transition in the second metal center less favorable.There are several types of spin crossover that can occur in a complex; some of them are light induced excited state spin trapping (LIESST), ligand-driven light induced spin change (LD-LISC), and charge transfer induced spin transition (CTIST).