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  • Synthesis of Square Planar ...
    Osei, Manasseh Kusi; Mirzaei, Saber; Bogetti, Xiaowei; Castro, Edison; Rahman, Mohammad Azizur; Saxena, Sunil; Hernández Sánchez, Raúl

    Angewandte Chemie, October 10, 2022, Letnik: 134, Številka: 41
    Journal Article

    Template‐assisted synthesis of well‐defined polynuclear clusters remains a challenge for M4 square planar topologies. Herein, we present a tetraamine scaffold RL(NH2)4, where L is a rigidified resorcin4arene, to direct the formation of C4‐symmetric RL(NH)4Cu4 clusters with Cu−Cu distances around 2.7 Å, suggesting metal‐metal direct interactions are operative since the sum of copper's van der Waals radii is 2.8 Å. DFT calculations display HOMO to HOMO‐3 residing all within a 0.1 eV gap. These four orbitals display significant electron density contribution from the Cu centers suggesting a delocalized electronic structure. The one‐electron oxidized Cu4+ species was probed by variable temperature X‐band continuous wave‐electron paramagnetic resonance (CW‐EPR), which displays a multiline spectrum at room temperature. This work presents a novel synthetic strategy for M4 clusters and a new platform to investigate activation of small molecules. Polynuclear reaction sites catalyze some of the most challenging transformations in chemistry. Programmatic assembly of atomically‐precise cluster compounds is challenging. Here we describe the synthesis of supramolecular ligands designed to nucleate well‐defined square planar tetranuclear copper clusters, establishing metal‐metal interactions capable of delocalizing oxidation stress across the cluster.