Guest dependent reversible single-crystal to single-crystal structural transformation in a flexible Gd(iii)-coordination polymer. Issue 4 (20th February 2015)

• Record Type: Journal Article
• Authors: Pal, Tapan K.; De, Dinesh; Neogi, Subhadip; Bharadwaj, Parimal K.
• Is Part Of: Inorganic chemistry frontiers. Volume 2:Issue 4(2015)
• Page Start: 395
• Page End: 402
• Publication Date: 2015-02-20
• Subjects: Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c4qi00193a
• Languages: English
• ISSNs: 2052-1553

Abstract

Abstract : We describe a 3D flexible Gd(iii )-coordination polymer, constructed from a linear carboxylate ligand, which shows reversible single-crystal to single-crystal "guest-responsive fitting" of the channels and carboxylate shift process, upon inclusion of aldehyde guests. Abstract : The ligand 2, 6, 2′, 6′-tetranitro-biphenyl-4, 4′-dicarboxylic acid (H 2 L ) reacts solvothermally with [Gd(NO3 )3 ]·6H2 O to produce a flexible and porous metal–organic framework, {[Gd2 (L )3 (DMF)4 ]·(4DMF)·(3H2 O)} n (1 ) (DMF = N, N ′-dimethylformamide). An X-ray crystallographic study reveals that compound1 contains a 3D framework structure with two different 1D channels (A and B) that are occupied by solvent DMF and water molecules. Crystals of1 when kept in a dichloromethane solution of 4-chlorobenzaldedhyde (4-ClPhCHO) afford the daughter product {[Gd2 (L )3 (DMF)4 ]·(4-ClPhCHO)·(4DMF)} n (1a ), via single-crystal to single-crystal (SC–SC) transformation, where lattice water molecules of channel B are replaced by guest aldehyde molecules. Likewise, exposure of 4-fluorobenzaldehyde (4-FPhCHO) and 4-methylbenzaldehyde (4-MePhCHO) vapors to fresh crystals of1 afforded two isostructural daughter frameworks, {[Gd(L )1.5 (DMF)(H2 O)3 ]·(4-FPhCHO)·(DMF)·(3H2 O)} n (1b ) and {[Gd(L )1.5 (DMF)(H2 O)3 ]·(4-MePhCHO)·(2DMF)·(H2 O)} n (1c ), respectively. Here, the guest aldehyde molecules occupy both the channels of the framework. Interestingly, the latter transformations exhibit a drastic rearrangement of the framework channels followed by several 'carboxylate-shift' processes, and concomitant movement of the water molecules from the cavity to the metal center. Importantly, all the host–guest complexes revert back to the as-synthesized crystal when kept in fresh DMF, rendering the mother framework a flexible and dynamic container for the aromatic aldehydes. All these transformations transpire through an SC–SC fashion under ambient conditions, pointing to the high flexibility of the framework and "guest-responsive fitting" of the channels. All the compounds are characterized by X-ray crystallography, thermogravimetry, elemental analysis, powder X-ray diffraction measurements and infrared spectroscopy.