Counteranion-Triggered and Excitation-Dependent Chemopalette Effect in a Supramolecular Dual-Emissive System Based on Cu3Pz3

Three Cu 3 Pz 3 -based isostructural complexes (Cu 3 L 3 ) 2 (CuX) 2 (labeled as 1 -ClO 4, 1 -NO 3, and 1 -Br, where X = ClO 4 –, NO 3 –, and Br –, respectively) were prepared by solvothermal reactions of an angular bifunctional pyridyl–pyrazole ligand, 4-(pyridin-4′-ylthio)-3,5-dimethyl-1 H -pyrazole ( H L ), with Cu(ClO 4 ) 2, Cu(NO 3 ) 2, and CuBr, respectively. Pyrazolate (Pz) groups are highly specific to form planar trinuclear Cu 3 Pz 3 units. Two Cu 3 L 3 units are further connected by two CuX units through N Py –Cu–N Py (Py = 4-pyridyl) bonds to form an octanuclear chairlike molecule (Cu 3 L 3 ) 2 (CuX) 2, which then self-assembles through intertrimeric cuprophilicity to construct chainlike supraaggregates featuring two luminophores, [Cu 3 Pz 3 ] 2 and CuPy 2 X. With different counteranions (ClO 4 –, NO 3 –, and Br – ), the complexes give off various emissions from red to green upon UV irradiation. 1 -ClO 4 and 1 -NO 3 show only low-energy (LE) orange (λ em max = 585 nm) and red (λ em max = 640 nm) emissions, while 1 -Br exhibits excitation-dependent (260–360 nm) emissions from yellow to green due to variation in the relative intensities of two resolvable emissions, high energy (HE, λ em max = 520 nm) and LE (λ em max = 630 nm). The dual emissions are assigned to 3 CC (LE states) based on excimeric [Cu 3 Pz 3 ] 2 units and 3 XLCT/ 3 MLCT (HE states) based on CuPy 2 X units. This work realizes a chemopalette effect through regulations of the counteranion and excitation energy in a dual-emissive system. It provides valuable insights into the nature of dual-emissive materials and the further investigation of the photophysical mechanism in such a system.