π−π Stacking and magnetic coupling mechanism on a mononuclear Cu(II) complex

Abstract

A mononuclear copper(II) complex was synthesized and in the crystal there are three types of π−π stacking interactions among adjacent complexes. The fitting for the data of the variable-temperature magnetic susceptibilities reveals that there is a weak anti-ferromagnetic coupling among adjacent Cu(II) ions with Weiss constant θ = −2.99 K = −2.08 cm⁻¹. Theoretical calculations reveal that two types of π−π stacking resulted in anti-ferromagnetic couplings with 2J = −12.40 cm⁻¹ and 2J = −9.74 cm⁻¹, respectively, and the third type of π−π stacking led to a weak ferromagnetic interaction with 2J = 4.28 cm⁻¹. The theoretical calculations also indicate that the ferromagnetic coupling sign from the π−π stacking accords with McConnell I spin-polarization mechanism, whereas the anti-ferromagnetic coupling signs cannot be explained with McConnell I spin-polarization mechanism.

Keywords:

• Crystal structure
• Magnetic coupling
• π−π Stacking
• Copper complex
• Theoretical calculation
• Broken-symmetry theory

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grant No. 20971080) and the Natural Science Foundation of Shandong Province (Grant Nos ZR2009BM026 and ZR2009BL002).