Isoreticular Design of Two Novel Metal Organic Frameworks and Their Single-Crystal-to-Single-Crystal Solvent Exchange Properties

Abstract

The rational design and synthesis of two novel MOFs based on the Schiff base ligand 5-({[4′-carboxy-(1,1′-biphenyl)-4-yl]methylene}amino)isophthalic acid (CBIPH3) formulated as [Cd3(CBIP)2(DMF)(H2O)2]n·8nDMF·4nH2O, (1)·8nDMF·4nH2O, and [Nd(CΒΙP)(DMF)(H2O)]n·1.5nDMF·3nH2O, (2)·1.5nDMF·3nH2O, are reported. The ligand CΒΙPH3 is an extended version of 5-[(4-carboxybenzylidene)amino]isophthalic acid (CIPH3) used previously by our group and was designed to isolate isoreticular analogues of compounds [Cd3(CIP)2(DMF)3] (UCY-3) and [Nd2(CIP)2(DMF)2.8(H2O)1.2] (UCY-2) which are known to possess interesting single-crystal-to-single-crystal (SCSC) transformation properties. Indeed, this goal was achieved, giving rise to the formation of 1·8nDMF·4nH2O and 2·1.5nDMF·3nH2O exhibiting 3-D microporous structures. Compound 2 was proven to display significant flexibility and capability to exchange, via SCSC transformation reactions, both the coordinated solvent molecules with N-methylpyrrolidone (NMP) and the lattice solvent molecules with aromatic hydrocarbons (benzene, toluene, o- and m-xylene). As a result, five SCSC modified products were additionally characterized crystallographically. The topological features of the reported compounds and the effect of the SCSC solvent exchange reactions on the structural characteristics of the pristine material are discussed in detail.