Substituent Influence on Structural and Luminescent Diversities of Cu3(pyrazolate)3-CunIn Coordination Supramolecular Isomers

Three photoluminescent isomeric complexes [Cu-3(L4)(3)](2)[CuI](2) (labeled as complexes 1, 2, and 3) were prepared from the same bifunctional organic ligand HL4 (3-(4pyridyl)-5-methyl-1H-pyrazole) and CuI by careful manipulation of the reaction conditions. Planar trinuclear Cu-3(L4)(3) and CuI/Cu2I2 units are integrated via N-Cu coordination bonds into Cu(3)Pz(3)-CunIn systems (Pz = pyrazolate). Complex 1 is a discrete supramolecular aggregate via cooperative pi-acid center dot center dot center dot base (Cu-3 center dot center dot center dot I) and Cu center dot center dot center dot Cu interactions. Complexes 2 and 3 are 2-fold interpenetrated three-dimensional frameworks. The small size of the CunIn (n = 1 or 2) units and structural diversities in such Cu(3)Pz(3)-CunIn systems were realized by preinstalling a methyl group on pyrazole at the 5-position of the ligand. The three complexes exhibit subtly different yellow emissions under UV irradiation in their solid states, originating from their respective triplet excited states of the supramolecular coordination luminophores. These results demonstrate that the structural and luminescent diversities of the Cu(3)Pz(3)-CunIn-based complexes can be regulated by substituents.