Jahn-Teller Distortion: Geometric and Electronic Effects

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Questions and Answers

Match the type of distortion with its effect on bond lengths in an octahedral complex:

Tetragonal Elongation = Bond lengths along the z-axis elongate relative to the x and y axes. Tetragonal Compression = Bond lengths along the z-axis compress relative to the x and y axes. Rhombic Distortion = Unequal bond lengths along all three axes (x, y, and z). No Distortion = All bond lengths are equal.

Match the electronic configuration of transition metal ions with the likelihood of exhibiting a strong Jahn-Teller effect in octahedral complexes:

$d^9$ (e.g., $Cu^{2+}$) = High likelihood; uneven occupancy of $e_g$ orbitals leads to strong distortion. High-spin $d^4$ (e.g., $Cr^{2+}$) = High likelihood; uneven occupancy of $e_g$ orbitals leads to strong distortion. $d^3$ (e.g., $V^{2+}$) = Low likelihood; even occupancy of $t_{2g}$ orbitals results in minimal distortion. $d^{10}$ (e.g., $Zn^{2+}$) = Low likelihood; fully filled d orbitals do not exhibit JT distortion.

Match the spectroscopic technique with the type of information it provides about Jahn-Teller distorted complexes:

UV-Vis Spectroscopy = Detects broadened or split peaks due to electronic transitions in the distorted complex. EPR Spectroscopy = Provides information about the symmetry and electronic structure of the distorted complex. Raman Spectroscopy = Identifies vibrational modes associated with the distortion. X-ray Diffraction = Determines the precise bond lengths and angles in the distorted geometry.

Match the effect of Jahn-Teller distortion with its impact on the stability of coordination complexes:

Energy Lowering = The distorted structure is generally more stable than the undistorted structure due to the lowering of electronic energy. Geometry Change = High symmetry structures are distorted to lower symmetry structures, altering bond lengths and angles. Orbital Splitting = Degenerate energy levels split, resulting in a net energy decrease. Property Modification = Significant changes in the chemical and physical properties of the complex. Signup and view all the answers

Match the application area with the influence of Jahn-Teller distortion on transition metal complexes:

Catalysis = Affects the reactivity and selectivity of metal-based catalysts by altering the electronic and geometric properties of the active site. Magnetism = Influences the magnetic properties of complexes by modifying the electronic structure and spin state of the metal ion. Materials Science = Can be exploited to design materials with specific properties, such as nonlinear optical materials and single-molecule magnets. Spectroscopy = Alters the UV-Vis and EPR spectra of the complexes. Signup and view all the answers

Match the Jahn-Teller effect with its primary cause:

Electronic Degeneracy = Uneven occupancy of degenerate orbitals. Geometric Distortion = Changes in bond lengths and angles to lower symmetry. Energy Stabilization = Lowering of electronic energy due to distortion. Spectroscopic Changes = Broadened or split peaks in UV-Vis spectra. Signup and view all the answers

Match the metal ion with its expected Jahn-Teller distortion strength in an octahedral complex:

$Cu^{2+}$ ($d^9$) = Strong distortion due to uneven $e_g$ occupancy. $Cr^{2+}$ (high-spin $d^4$) = Strong distortion due to uneven $e_g$ occupancy. $Mn^{2+}$ (high-spin $d^5$) = Weak distortion due to symmetrical $d$ orbital occupancy. $Fe^{3+}$ (high-spin $d^5$) = Weak distortion due to symmetrical $d$ orbital occupancy. Signup and view all the answers

Match the type of spectroscopic change with the consequence of Jahn-Teller distortion:

Broadened UV-Vis Peaks = Splitting of electronic energy levels due to lowered symmetry. Altered EPR Signals = Changes in the electronic structure and magnetic properties. Shifted Raman Frequencies = Changes in vibrational modes due to altered bond lengths. No Change in NMR Spectra = The nuclear magnetic resonance is not directly changed. Signup and view all the answers

Match the application of transition metal complexes with the role of Jahn-Teller distortion:

Catalysis = Modifies the electronic and geometric properties of the active site, influencing reactivity. Magnetism = Affects spin state and magnetic interactions via electronic configuration changes. Materials Science = Enables design of materials with specific optical and magnetic properties. Sensor Technology = Alters conductivity of a material by controlling the geometry. Signup and view all the answers

Match the factor that affects the magnitude of Jahn-Teller stabilization energy in a complex:

Extent of Distortion = Greater distortion leads to larger stabilization energy. Metal Ion Identity = Different metal ions exhibit varying degrees of Jahn-Teller effect. Ligand Field Strength = Stronger ligand fields can influence the extent of distortion. Temperature = Lower temperatures favor expression of distortion. Signup and view all the answers

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Flashcards

Jahn-Teller (JT) Distortion

A geometric distortion in non-linear molecular systems that lowers the molecule's overall energy, common in transition metal complexes.

Geometric Change Due to JT Effect

Distortion from high to lower symmetry, such as octahedral to tetragonal or rhombic.

Electronic Configuration Impact

Uneven electron occupancy in eg or t2g orbitals causing distortion.

Strong JT Effect Examples

Configurations like d9 (Cu2+), high-spin d4 (Cr2+), and d7 (Co2+) in octahedral fields strongly exhibit JT effects.