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In the comproportionation reaction of Cu^IIX₂ and Cu⁰ with isopropylacetylene (iPr−C≡C−H), the ethynediide species C₂²⁻ is generated via concomitant C−H/C−C bond cleavage of the iPr−C≡C−H precursor under moderate temperature to direct the formation of Cu^I mixed ethynediide/isopropylethynide nanoclusters (potentially explosive). The active ethynediide dianion C₂²⁻ exhibits chameleon-like templating behavior to form C₂@Cu_m (m=6 (3, 4), 7 (2, 4), 8 (1)) central structural units for successive formation of {C₂²⁻⊂Cu₂₄} (1, 2), {6 C₂²⁻⊂Cu₄₈} (3), and {18 C₂²⁻⊂Cu₉₂} (4) complexes. Bearing the highest C₂²⁻ content, complex 4 features an unprecedented nanoscale Cu₂C₂ kernel. Furthermore, 1–3 exhibit structure-controlled photoluminescence in the solid state.

Template release: Temperature variation triggers the release of ethynediide C₂²⁻ from isopropylacetylene through concomitant C−H/C−C bond cleavage, leading to formation of Cu^I mixed ethynediide/alkynide nanoclusters. Synthesis of {C₂²⁻⊂Cu₂₄}, {6 C₂²⁻⊂Cu₄₈}, and {18 C₂²⁻⊂Cu₉₂} establishes a class of tunable nanostructures where the increasing number of ethynediide bestows nuclearity expansion and structural diversity.