Nonadditive and additive ligand fields and spectrochemical series arising from ligand field parameterization schemes. Pyridine as a nonlinearly ligating .pi.-back-bonding ligand toward chromium(III)

1976 ◽  
Vol 15 (6) ◽  
pp. 1399-1407 ◽  
Author(s):  
Joergen. Glerup ◽  
Ole. Moensted ◽  
Claus E. Schaeffer
Keyword(s):  
Ligand Field ◽  
Parameterization Schemes ◽  
Back Bonding ◽  
Ligand Fields ◽  
Ligand Field Parameterization ◽  
Spectrochemical Series

Ligand field effects on the ground and excited states of reactive FeO2+ species

2018 ◽  
Vol 20 (45) ◽  
pp. 28786-28795 ◽  
Author(s):  
Justin K. Kirkland ◽  
Shahriar N. Khan ◽  
Bryan Casale ◽  
Evangelos Miliordos ◽  
Konstantinos D. Vogiatzis
Keyword(s):  
Iron Oxide ◽  
Quantum Chemical Calculations ◽  
Excited States ◽  
Quantum Chemical ◽  
Ligand Field ◽  
Reactive Iron ◽  
Field Effects ◽  
Ligand Fields

Multiconfigurational quantum chemical calculations on bare and representative ligated iron oxide dicationic species suggest that weak ligand fields promote more reactive channels, whereas strong ligand fields stabilize the less reactive iron-oxo structure.

Single crystal electronic spectra of a series of trans nickel(II) complexes with N,N′-diethyl- and N,N′-dimethylethylenediamine

1977 ◽  
Vol 55 (17) ◽  
pp. 3172-3189 ◽  
Author(s):  
A. B. P. Lever ◽  
G. London ◽  
P. J. McCarthy
Keyword(s):  
Steric Hindrance ◽  
Electronic Spectra ◽  
Spherical Harmonic ◽  
Bonding Strength ◽  
Ligand Field ◽  
Transition Energies ◽  
B Values ◽  
Axial Ligands ◽  
Symmetry Adapted Functions ◽  
Spectrochemical Series

We have measured the polarized crystal spectra at 10 K. of Ni(s-Et2en)2X2, where X = Cl, Br, NCS, and H2O (with Cl, Br, and I counterions) and *-Et2en is N, N'-diethylethylenediamine, and of Ni(s-Me2en)2X2, where X = NCS and NO3, and.s-Me2en is N,N′-dimethylethylenediamine. Transition energies were calculated for D4h symmetry using symmetry adapted functions and a normalized spherical harmonic Hamiltonian. When the differences between calculated and observed band positions are minimized, the ligand-field and angular overlap parameters listed in Table 2 are obtained. The criteria for the band assignments are discussed. The principal conclusions are: (1) The π interactions between Ni(II) and the axial ligands are small in contrast to tetragonal Cr(III) complexes. (2) Equatorial and axial parameters are relatively independent, in contrast to tetragonal Cu(II) complexes. (3) The more basic,s-Et2en exerts a stronger ligand field than,s-Me2en. (4) The σ-bonding strength of the axial ligands follows the spectrochemical series. (5) DQ for the axial ligands in the ethyl complexes is lower than anticipated, probably due to steric hindrance of the bulky ethyl groups. (6) B values are all near 850 cm−1, except for an anomalously low value for Ni(s-Et2en)2(NCS)2.

The d2 and d8 Noncubic Ligand Field Spectrum. I. The Complete Theory of Quadrate, Trigonal, and Cylindrical Ligand Fields

1972 ◽  
Vol 27 (12) ◽  
pp. 1820-1860 ◽  
Author(s):  
Jayarama Perumareddi
Keyword(s):  
Cylindrical Symmetry ◽  
Complete Theory ◽  
Ligand Field ◽  
Spin Orbit ◽  
Planar Limit ◽  
Unitary Transformations ◽  
Cubic Fields ◽  
Electronic Configurations ◽  
Tetrahedral Complexes ◽  
Ligand Fields

AbstractThe complete theory of Liehr and Ballhausen for d2 and d8 electronic configurations immersed in cubic fields has been extended to include noncubic ligand fields of quadrate, trigonal, and cylindrical symmetry. The complete set of symmetry adapted eigenvectors for the three symmetries have been derived in various coupling schemes in which the spin-orbit interaction, electron cor-relation, and ligand field in turn are varied from minor to dominant perturbations. The cor-responding energy matrices as a function of the parameters of the ligand field, electron correlation, and spin-orbit constant have been constructed in all the representations. Unitary transformations connecting different formalisms were obtained. The energy matrices have been solved for representative sets of parametric values and energy diagrams have been plotted in all the symmetries as well as in the square planar limit of the quadrate crystalline field. The secular determinants, the eigenfunctions, the energy diagrams, and the unitary transformations presented here are extremely useful in the study of the various aspects of spectroscopic, magnetic, and other properties of appropriate systems. The theory is applicable to quadrately distorted or substituted, trigonally distorted or substituted, octahedral and tetrahedral complexes and to compounds of cylindrical symmetry of d2 and d8 electronic configurations.

Cobalt(II), nickel(II) and copper(II) complexes of some o-hydroxycrotonophenones

1980 ◽  
Vol 33 (4) ◽  
pp. 729 ◽  
Author(s):  
M Palaniandavar ◽  
C Natarajan
Keyword(s):  
High Spin ◽  
Metal Ion ◽  
Magnetic Measurements ◽  
Thermal Studies ◽  
Ligand Field ◽  
Square Planar ◽  
Infrared Studies ◽  
Stabilization Energies ◽  
Back Bonding ◽  
High Ligand

Metal(II) complexes of the type ML2,nB [M = CuII, NiII, CoII; L = 2- hydroxy-5-X-crotonophenone where X = H, CH3, Cl; B = H2O, pyridine; n = 0, 1, 2] have been obtained and investigated. With the help of element analyses, magnetic measurements, ligand field and infrared spectra and thermal studies, the structure and the nature of bonding have been established. The anhydrous copper(II) chelates are monomeric and possess trans-square-planar configuration while the corresponding cobalt(II) and nickel(II) compounds are polymeric and possess high-spin trans-octahedral configuration. All the base adducts possess high-spin trans-octahedral structure with lesser tendency toward dissociation in solution. Infrared studies indicate that v(C=O) and v(M-O) are affected by metal ion and phenyl substitutions and adduct formation. The order of stabilities, namely Cu > Ni > Co, derived from v(M-O) parallels the crystal field stabilization energies. Substitution in the phenyl ring of the complexes produces shifts in v(M-O) which are related to the resonance capacities of the substituents. ��� The relatively high ligand field strength of o-hydroxycrotonophenone compared to salicylaldehyde is attributed to the conjugation of C=O with C=C which lowers the energy of the π3* orbital leading to extensive back-bonding with dπ orbitals of the metal.

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