The polarized optical spectra of the ions Ti3+, V3+, Cr3+, Mn3+, Co3+, and Ni3+ in corundum single crystals have been studied at temperatures from 4.2° to 1200°K. A theory of the band strength based on the point‐charge model and p‐d mixing has been developed and applied to the data with results in fair agreement with experiment. The effects of temperature show that the vibrational‐electronic contribution to band strength is quite small at low temperature but may be appreciable at high temperatures. The crystal‐field parameters have been calculated as convergent lattice sums. The observed trigonal‐field parameter has the opposite sign from that calculated by the point‐charge model if the impurity ion is assumed to occupy an Al3+ ion position in the lattice, but has the same sign as calculated for an ion 0.1 A displaced along the c3 axis toward the empty octahedral site. Details of the spectra have been interpreted as showing that the surroundings of an ion are distorted in some electronic states.

Optical spectra of transition-metal ions in corundum

A ligand field model for 3d1 ions with approximate D3h site symmetry has been developed which satisfactorily explains the fine structure parameters, the EPR spectra, and the magnetic susceptibility. The treatment includes the essential features of Jahn-Teller distortion and covalency effects which are found to have important bearing on the nature of the Jahn-Teller distortion. Finally by the spin Hamiltonian formalism of Pryce the g-values and magnetic susceptibility arecalculated. Attempts are made to fit the experimental data of optical absorption, gr-values, and magnetic susceptibility with a set of parameter values in the theoretical expressions at different temperatures. From this an estimate is made of covalency and Jahn-Teller parameters.

Jahn-Teller Effect in the Ligand Field Theory of Trigonal Bipyramidal V4+ Complexes

Lattice-ion interactions of Fe2+ ion in a tetrahedral environment

Metal acetylacetonates of the general formula [M(acac)3 ] (MIII =Cr, Mn, Fe, Co) are among the best investigated coordination compounds. Many of these first-row transition metal complexes are known to have unique electronic properties. Independently, photophysical research with different β-diketonate ligands pointed towards the possibility of a special effect of the 2,4,6-trimethylphenyl substituted acetylacetonate (mesacac) on the electron distribution between ligand and metal (MLCT). We therefore synthesized and fully characterized the previously unknown octahedral title complex. Its solid-state structure shows a Jahn-Teller elongation with two Mn-O bonds of 2.12/2.15 Å and four Mn-O bonds of 1.93 Å. Thermogravimetric data show a thermal stability up to 270 °C. High-resolution mass spectroscopy helped to identify the decomposition pathways. The electronic state and spin configuration of manganese were characterized with a focus on its magnetic properties by measurement of the magnetic susceptibility and triple-zeta density functional theory (DFT) calculations. The high-spin state of manganese was confirmed by the determination of an effective magnetic moment of 4.85 μB for the manganese center.

Electronic Structure and Magnetic Properties of a High-Spin MnIII Complex: [Mn(mesacac)3 ] (mesacac=1,3-Bis(2,4,6-trimethylphenyl)-propane-1,3-dionato).

Lattice‐ion interactions of Co2+ ion in an octahedral environment

A theoretical expression for the magnetic susceptibility and anisotropy of an Mn (111) ion having trigonal symmetry in octahedral trisacetylacetonato manganese have been derived on the basis of the more general molecular orbital method of Van Vleck, Stevens, and Bose et al., considering quantum mechanical tunnelling which links equivalent vibronic states of the Jahn-Teller ion. Attempts have been made to fit the experimental data of optical absorption and magnetic susceptibility with a unique set of parameters in the theoretical expressions at all temperatures. From this an estimate of the parameters which describe the Jahn-Teller potential is made.



Ein theoretischer Ausdruck fur die magnetische Suszeptibilitat und Anisotropie eines Mn (111)-Ions mit trigonaler Symmetrie in oktaedrischem Mangan-Triazetylazetonat wurde auf der Grundlage einer allgemeineren Molekulorbitalmethode von Van Vleck, Stevens und Bose et al. abgeleitet, wobei quantenmechanisches Tunneln, das aquivalente Schwingungszustande des Jahn-Teller-Ions koppelt, berucksichtigt wird. Es wird der Versuch gemacht, die experimentellen Ergebnisse der optischen Absorption und magnetischen Suszeptibilitat mit einem einzigen Parametersatz an die theoretischen Ausdrucke fur alle Temperaturen anzupassen. Daraus werden Parameter, die das Jahn-Teller-Potential beschrieben, berechnet.

Role of Jahn‐Teller Effect in the Ligand Field Theory of Octahedrally Coordinated Trisacetylacetonato Manganese

The theoretical expressions for the magnetic susceptibility and g-values of trigonally distorted octahedral V3+ ion have been developed on the basis of molecular orbital method of Stevens [19] and Bose et al. [20]. Results are discussed considering the less strong vibronic coupling (dynamic Jahn-Teller effect) in which an orbital triplet interacts with the vibrational E-modes of the ligands. Comparison is made with experimental results on magnetic susceptibility, g-values, and optical absorption with a unique set of values of parameters in the theoretical expressions at all temperatures. The Jahn-Teller coupling parameter appears to be appreciable in some of the complexes.



Die theoretischen Ausdrucke fur die magnetische Suszeptibilitat und die g-Werte trigonal gestorter oktaedrischer V3+ -Ionen werden auf der Basis der Molekulbahnen-Methode von Stevens [19] und Bose et al. [20] entwickelt. Die Ergebnisse werden unter Berucksichtigung der weniger starken vibronischen Kopplung (dynamischer Jahn-Teller-Effekt) diskutiert, wobei ein Bahntriplet mit den vibronischen E-Moden der Liganden in Wechselwirkung tritt. Die experimentellen Ergebnisse der magnetischen Suszeptibilitat, der g-Werte und der optischen Absorption werden mit einem eindeutigen Satz von Parameterwerten in den theoretischen Ausdrucken bei allen Temperaturen verglichen. Der Jahn-Teller-Kopplungsparameter scheint in einigen Komplexen von Bedeutung zu sein.

B. D. Bhattacharyya

Papers

Role of Jahn‐Teller Effect in the Ligand Field Theory of Octahedrally Coordinated Trisacetylacetonato Manganese

Lattice—Ion Interactions in the Ligand Field Theory of Trigonally Distorted Octahedral V3+ Complexes

Role of the Jahn-Teller Effect in the Ligand Field Theory of the Magnetic Behaviour of (NMe4)2FeCl4

Lattice‐ion interactions of Co2+ ion in an octahedral environment

Ligand Field Theory of Some Double Chlorides of V2+ Ions