Asymmetric Ring Opening in Tetrazine‐based Ligand Affording a Tetranuclear Opto‐Magnetic Ytterbium Complex

We report the formation of a tetranuclear lanthanide cluster, [Yb 4 (bpzch) 2 (fod) 10 ] ( 1 ), which occurs from a serendipitous ring opening of the functionalized tetrazine bridging ligand, bpztz (3,6‐dipyrazin‐2‐yl‐1,2,4,5‐tetrazine) upon reacting with Yb(fod) 3 (fod ‐ = 6,6,7,7,8,8,8‐heptafluoro‐2,2‐dimethyl‐3,5‐octandionate). Compound 1 was structurally elucidated via single‐crystal X‐ray crystallography and subsequently magnetically and spectroscopically characterized to analyse its magnetisation dynamics and its luminescence behaviour. Computational studies validate the observed M J energy levels attained by spectroscopy and provides a clearer picture of the slow relaxation of the magnetisation dynamics and relaxation pathways. These studies demonstrate that 1 acts as a single‐molecule magnet (SMM) under an applied magnetic field in which the relaxation occurs via a combination of Raman, direct, and quantum tunnelling processes, a behaviour further rationalized analysing the luminescent properties. This marks the first lanthanide‐containing molecule that forms by means of an asymmetric tetrazine decomposition.