Factors Determining the Ligand Field Stabilization Energies of the Hexaaqua 2+ Complexes of the First Transition Series and the Irving-Williams Order

1995 ◽  
Vol 34 (22) ◽  
pp. 5666-5671 ◽  
Author(s):  
David A. Johnson ◽  
Peter G. Nelson
Keyword(s):  
Ligand Field ◽  
Transition Series ◽  
Stabilization Energies

Ligand field stabilization energies and stereochemistry of early second and third row transition elements

1968 ◽  
Vol 21 (1) ◽  
pp. 9 ◽  
Author(s):  
R Colton ◽  
JH Canterford
Keyword(s):  
Periodic Table ◽  
Ligand Field ◽  
Transition Elements ◽  
Transition Series ◽  
Stabilization Energies

The elements of the second and third row transition series towards the left of the Periodic Table show clearly defined trends in their observed stereochemistries. These trends are summarized and an explanation for the experimental facts is suggested.

Thermodynamic of metal complexation of the macrocyclic antibiotic rifampicin

2001 ◽  
Vol 79 (1) ◽  
pp. 42-49
Author(s):  
I Shehatta ◽  
I Kenawy ◽  
A H Askalany ◽  
Ayman A Hassan
Keyword(s):  
Binding Sites ◽  
Equilibrium Constants ◽  
Ionic Species ◽  
Ligand Field ◽  
Water Medium ◽  
Acid Base ◽  
Distribution Diagram ◽  
Macrocyclic Antibiotic ◽  
Transition Series ◽  
Different Temperatures

The acid-base and complexation equilibria of rifampicin with H+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, and Pb2+ were studied by means of potentiometry. The stoichiometric equilibrium constants were determined in 50% (v/v) methanol-water medium at different temperatures and constant ionic strength (0.05 M KCl). It was established that rifampicin has two proton-binding sites. The distribution diagram of the corresponding ionic species as a function of pH is given and indicated that rifampicin exists predominantly in the zwitterionic form at pH [Formula: see text] 5. The thermodynamic parameters of protonation and complexation were derived and discussed. The formation of the complexes is spontaneous, more favourable at lower temperatures, entropically unfavourable, and an enthalpy-driven process. The order of the changes in Gibbs energy and enthalpy accompanying the complexation was found to be Mn2+ < Co2+ < Ni2+ < Cu2+ > Pb2+ > Zn2+ > Cd2+ > Hg2+ in accordance with the well-known sequence of Irving and Williams. The transition series contraction energy (Er(Mn-Zn)), and the ligand field stabilization energy (δH) were calculated from the enthalpy changes.Key words: rifampicin, thermodynamics, potentiometry, and complexation.

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.

Über die Spin-Bahn-Wechselwirkung in der Ligandenfeldtheorie

1963 ◽  
Vol 18 (3) ◽  
pp. 276-280
Author(s):  
H.-H. Schmidtke
Keyword(s):  
Field Theory ◽  
Ligand Field ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Field Potentials ◽  
Coupling Energy ◽  
Ligand Field Theory ◽  
Transition Series ◽  
Low Symmetry ◽  
Made In

The spin-orbit coupling operators in ligand field theory for octahedral, tetragonal, trigonal and axial symmetry are derived from the corresponding crystal field potentials. An estimate of the coupling energy for the low symmetry part of this operator is made in the case of octahedrally symmetric complexes of the first transition series. The results are discussed and compared with other approaches to this problem.

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