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

Abstract

A three-dimensional copper(II) coordination polymer (CP), {Cu(L-F)(N3)} 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 [Cu2(COO)N3] 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 {Cu3(L-F)4(N3)2(CH3OH)2} n (2), {Cu3(L-F)4(N3)2(C2H5OH)2} n (3) and {Cu2.5(L-F)3(N3)2(HOC2H4OH)0.5} n (4). CPs (2) and (3) display a similar structure, in which trinuclear subunit [Cu3(COO)2(N3)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 [Cu3(COO)2(N3)2] and binuclear [Cu2(COO)N3] 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.