Coordination-Bond-Driven Dissolution-Recrystallization Structural Transformation with the Expansion of Cuprous Halide Aggregate.

Metal-organic frameworks (MOFs) with cuprous-halide-aggregates have shown superiority as organic LED (OLED) and semiconductor materials, while engineering MOF flexibility by involving the expansion of cuprous aggregates remains a great challenge. In this particular work, a dissolution-recrystallization structural transformation (DRST) with the dramatic growth of Cu-I aggregates, from 2D to 3D has been successfully realized. The unsaturated coordination nodes (2-positional nitrogen atoms) in have been demonstrated to be the driven force for DRST to via the formation of coordination bonds. The structural transformation process was irreversible and observed with optical microscopy and powder XRD. The expansion of Cu-I aggregates was also computational simulated accompanying with the rotation of the neutral tripodal TTTMB ligand (1,3,5-tris(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene) and the reduction of Cu to Cu. Moreover, the intermediate product was captured by adding the planar molecular anthrancene to shut down the reaction, where only partial 2-positional nitrogen atoms coordinated to the aggregates and the anthrancene was oxidized to anthraquinone. has further confirmed that DRST involved the breakage and recombination of coordination bonds and the electron transfer. and could be applied as semiconductor and OLED materials. This work has provided insights for crystal engineering, especially for the construction of the CuX aggregates, and illustrated that DRST could be controlled with a rational design (as the unsaturated coordination modes).