Insights from (125)Te and (57)Fe nuclear resonance vibrational spectroscopy: a [4Fe–4Te] cluster from two points of view

Iron–sulfur clusters are common building blocks for electron transport and active sites of metalloproteins. Their comprehensive investigation is crucial for understanding these enzymes, which play important roles in modern biomimetic catalysis and biotechnology applications. We address this issue by utilizing (Et(4)N)(3)[Fe(4)Te(4)(SPh)(4)], a tellurium modified version of a conventional reduced [4Fe–4S](+) cluster, and performed both (57)Fe- and (125)Te-NRVS to reveal its characteristic vibrational features. Our analysis exposed major differences in the resulting (57)Fe spectrum profile as compared to that of the respective [4Fe–4S] cluster, and between the (57)Fe and (125)Te profiles. DFT calculations are applied to rationalize structural, electronic, vibrational, and redox-dependent properties of the [4Fe–4Te](+) core. We herein highlight the potential of sulfur/tellurium exchange as a method to isolate the iron-only motion in enzymatic systems.