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Updated: Aug 20, 2026

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures
Published on: October 9, 2012
Paramagnetism at ambient temperature, diamagnetism at low temperature in a Ru2(6+) core: structural evidence for
F Albert Cotton1, Carlos A Murillo, Joseph H Reibenspies
1Laboratory for Molecular Structure and Bonding, Texas A&M University, College Station, Texas 77842-3012, USA. cotton@tamu.edu
Abstract:
Variable temperature magnetic studies of the Ru(2)(6+) guanidinate compounds Ru(2)(hpp)(4)Cl(2) (1) and Ru(2)(hpp)(4)(CF(3)SO(3))(2) (2) show that they are paramagnetic with two unpaired electrons at room temperature and that they appear essentially diamagnetic at 2 K. In neither compound do the Ru-Ru distances vary by more than 0.008(1) A from 27 to 296 K. This argues strongly that the ground state electronic configuration remains constant over this temperature range and that the decrease in magnetism as the temperature is lowered must be attributable to zero-field splitting of the (3)A(2g) ground state arising from the electronic configuration sigma(2)pi(4)delta(2)pi(2). The Ru-Ru distance in 1 is about 0.04-0.05 A longer than that in 2 which indicates that the Ru(2)(hpp)(4)(2+) core is quite sensitive to the nature of the axial ligands. The electronic spectra show three absorption bands for each compound.
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