Copper(I) Alkynyl Clusters with Crystallization-Induced Emission Enhancement

Four copper(I) alkynyl complexes incorporating phosphate ligands, namely, [Cu-16((BuC)-Bu-t C)(12)(PhOPO3)(2)](n) (1; PhOPO3 = phenyl phosphate), [Cu-16((BuC)-Bu-t C)(12)(1-NaphOPO(3))(2)] n (2; 1-NaphOPO(3) = 1-naphthyl phosphate), [VO4@Cu-25((BuC)-Bu-t C)(19)(1-NaphOPO(3))]( PF6)(0.5)(F)(0.5) (3), and [ PO4@Cu-25( tBuC C)19(1-NaphOPO(3))](PF6)(0.5)( F)(0.5) (4), were solvothermally synthesized and well-characterized by IR spectroscopy, powder X-ray diffraction, and single-crystal X-ray diffraction. Single-crystal X-ray analysis revealed that the Cu16 cluster-based coordination chain polymers 1 and 2 are formed by assembly during crystallization, while 3 and 4 contain high-nuclearity copper(I) composite clusters enclosing orthovanadate and phosphate template ions, respectively, that are supported by ROPO32- ligands. Complexes 1-4 exhibit crystallization-induced emission enhancement. Their crystalline state shows strong luminescence, in striking contrast to the weak emission of the amorphous state and solution phase. A detailed investigation of the crystal structure suggests that well-arranged C-H center dot center dot center dot p and p center dot center dot center dot p interactions between the ligands are the major factors for this enhanced emission. Clusters 3 and 4 also exhibit photocurrent responses upon visible-light illumination.

Automated summary

Four copper(I) alkynyl complexes with phosphate ligands were synthesized and characterized, showing strong luminescence in the crystalline state compared to the amorphous and solution phases. The enhanced emission was attributed to well-arranged C-H···p and p···p interactions between the ligands. Additionally, some complexes exhibited photocurrent responses upon visible-light illumination.