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Identification of a Weak Interaction between the Spin-Only 4f-Electronic System of Trivalent Gd Ion and a
Anas Santria1,2, Naoto Ishikawa1
1Department of Chemistry, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan.
Abstract:
An electronic interaction between the spin-only 4f-electronic system and the photoexcited π cyclic system has been identified in the anionic bis(phthalocyaninato)gadolinium(III) complex [Pc2Gd]- by using variable-temperature variable-magnetic-field magnetic circular dichroism (VTVH MCD). Two positive MCD A-term patterns, corresponding to the QH and QL absorption bands, were observed to increase in intensity as the temperature decreased, indicating a ferromagnetic-type interaction between spin angular momentum S of the 4f system and orbital angular momentum L of the photoexcited π system. A theoretical model incorporating the S-L interaction constant C was fitted to the VTVH MCD spectra, confirming the presence of a weak interaction, whose intensity was determined as C = 0.27 cm-1 for QL and C = 0.02 cm-1 for QH. Ab initio calculations using the RASSCF and RASSI methods revealed that the inclusion of the excited state calculations with the spin multiplicity (2S + 1) of 6 was crucial for assigning Δ and C values. This underscores the essential role of the 6P term in accurately modeling the S-L interaction in [Pc2Gd]-.
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