Solvent-mediated structural transformations of copper(II) coordination polymers induced by different short-chain alcohols

A three-dimensional copper(II) coordination polymer (CP), {Cu(L-F)(N-3)}(n) (1), was synthesized by reacting Cu(NO3)(2) with 5-fluoronicotinic acid (HL-F) and NaN3 in a water medium. Complex (1) shows a 3D network, in which the 1D [Cu-2(COO)N-3](n) chains are interconnected via L-F ligands. By immersing (1) into different short-chain alcohols (CH3OH, C2H5OH and HOC2H4OH), three different CPs were isolated, including {Cu-3(L-F)(4)(N-3)(2)(CH3OH)(2)}(n) (2), {Cu-3(L-F)(4)(N-3)(2)(C2H5OH)(2)}(n) (3) and {Cu-2.5(L-F)(3)(N-3)(2)(HOC2H4OH)(0.5)}(n) (4). CPs (2) and (3) display a similar structure, in which trinuclear subunit [Cu-3(COO)(2)(N-3)(2)(solvent)(2)] is generated. Furthermore, such entities are interconnected via L-F ligands to give rise to a 3D network. As for (4), there are trinuclear [Cu-3(COO)(2)(N-3)(2)] and binuclear [Cu-2(COO)N-3] units, which are interconnected by L-F ligands to generate a 3D network. Notably, in (2) and (3), the coordination modes of CH3OH and C2H5OH solvents are monodentate; whereas for (4), the HOC2H4OH solvent adopts a bridging mode to link two Cu atoms. Of further interest, these processes are solvent-mediated structural transformations, with obvious colour changes in the crystals. Structural changes and mechanisms of transformation are discussed in detail.