MCD Spectra for Metal-Centered Transitions in the Hg(3)(dppm)(3)(4+) Cluster Complex

Area of Science:

• Inorganic Chemistry
• Spectroscopy
• Physical Chemistry

Background:

• Mercury complexes offer unique electronic properties.
• Bis(diphenylphosphino)methane (dppm) is a common ligand in coordination chemistry.
• Magnetic Circular Dichroism (MCD) spectroscopy is sensitive to electronic transitions and molecular symmetry.

Purpose of the Study:

• To investigate the electronic transitions of Hg(3)(dppm)(3)(SO(4))(2) using MCD and absorption spectroscopy.
• To interpret the observed spectral features in terms of metal-centered electronic excitations.
• To elucidate the nature of the lowest energy transition involving spin-orbit coupling.

Main Methods:

• Solution and rigid glass MCD spectroscopy at varying temperatures (295 K and 80 K).
• UV-Vis absorption spectroscopy at 295 K and 80 K.
• Spectral analysis to identify transitions and assign terms (A and B terms).

Main Results:

• MCD spectra at 295 K showed two minima, resolving into distinct A and B terms at 80 K.
• Absorption spectra exhibited intense bands at 3.05 &mgr;m(-)(1) (295 K) shifting to 3.09 &mgr;m(-)(1) (80 K), with a lower intensity band at 3.40 &mgr;m(-)(1).
• The positive A term was assigned to a sigma --> pi transition to a spin-orbit E' state.

Conclusions:

• The observed MCD and absorption spectra are consistent with 6s --> sigma and 6s --> pi metal-centered transitions.
• The lowest energy band's A term is attributed to a sigma --> pi transition to the spin-orbit E' state of (3)A(2)" origin.
• Temperature-dependent MCD and absorption spectroscopy provide valuable insights into the electronic structure of mercury complexes.