Flexible and dynamic Cu I metal−organic framework [Cu(I)-MOF (1)] with well-defined nanoporous channel built with flexible terpyridine ligand offers a scaffold for the inclusion of different classes of guest molecules through a single-crystal-tosingle-crystal (SCSC) transformation in the vapor phase at ambient conditions with visual color change. Thus, Cu(I)-MOF (1) offers a potential platform for molecular recognition and undergoes guestresponsive structural dynamism that can be triggered by interfacial interactions. Despite having the stable conformation of the rotational isomers, it selectively encapsulates the less stable conformation (eclipsed and gauche) into its cavity from their vapor phases in the SCSC process. All of the guest-exchanged processes are reversible. It shows selectivity toward less polar guest in a class. The intermediate of all of the guest-exchanged processes appeared as a black material (H 2 O@Cu(I)-MOF) (1z) prior to the encapsulation of each guest that happens through the SCSC manner followed by encapsulation of the guests replacing H 2 O in situ at ambient conditions through SCSC transformation. This confirms that the process is a two-step process leading to a common intermediate. The MOF loses its luminescence behavior with H 2 O removing lattice solvents in situ and appears as a black material, and it regains its luminescence property with the guests replacing H 2 O. Thus, the MOF displays both luminescence "turn-off" and "turn-on" before and after incorporation of the guests, respectively, leading to a common turn-off mechanism. A fluorescence titration experiment shows selectivity toward aniline among benzene and its derivatives.

A newly synthesized bis-pyridyl ligand having a diphenyl ether backbone (LP6) displayed the ability to form crystalline coordination polymers (CP1-CP6) which were fully characterized by single crystal X-ray diffraction. Most of the resulting polymers were lattice-occluded crystalline solids-a structural characteristic reminiscent to gels. The reactants of the coordination polymers produced metallogels in DMSO/water confirming the validity of the design principles with which the coordination polymers were synthesized. Some of the metallogels displayed material properties like in situ synthesis of Ag nanoparticles and stimuli-responsive gel-sol transition including sensing hazardous gases like ammonia and hydrogen sulfide.

A new series of coordination polymers (CPs) were synthesized and crystallographically characterized by single-crystal X-ray diffraction with the aim of developing drug-delivery systems via metallogel formation. Structural rationale was employed to design such coordination-polymer-based metallogels. As many as nine CPs were obtained by reacting two bis(pyridyl)urea ligands, namely, 1,3-dipyridin-3-ylurea (3U) and 1,3-dipyridin-4-ylurea (4U), and the sodium salt of various nonsteroidal antiinflammatory drugs, namely, ibuprofen (IBU), naproxen (NAP), fenoprofen (FEN), diclofenac (DIC), meclofenamic acid (MEC), mefenamic acid (MEF), and Zn(NO 3 ) 2 . All of the CPs displayed 1D polymeric chains that were self-assembled through various hydrogen-bonding interactions involving the urea N−H and carboxylate O atoms and, in a few cases, lattice-occluded water molecules. The reacting components of the CPs produced five metallogels in dimethyl sulfoxide/water. The gels were characterized by rheology and transmission electron microscopy. Three selected metallogelators, namely, 3UMEFg, 3UNAPg, and 3UMECg, showed in vitro anticancer, cell imaging, and multidrug delivery for antibacterial applications, respectively. The shear-thinning properties of 3UMECg (rheoreversibility and injectability) make it a potential candidate for plausible topical application.

Metallogelators/metallogels derived from a series of multi-NSAID based Zn(II)-coordination complexes displaying anti-cancer and anti-bacterial properties were designed based on a structural rationale as plausible multi-drug self-delivery system.

The supramolecular synthon approach in the context of the crystal engineering rationale has been exploited to synthesize a new series of primary ammonium sulfonate salts derived from primary alkyl amines with varying alkyl chain lengths (A n = CH 3 −(CH 2 ) n −NH 2 ; n = 2−11, 13−15, 17) and naphthalene-2-sulfonic acid (N2S) as potential supramolecular gelators. The sulfonate salts A n N2S with n ≥ 9 showed the ability to immobilize a number of polar and nonpolar solvents including dimethyl sulfoxide/water, resulting in supramolecular gels which were characterized by dynamic rheology and transmission electron microscopy. Single-crystal X-ray diffraction studies carried out on eight such salts confirmed the presence of gel-inducing hydrogen bonded supramolecular synthons. Anti-bacterial studies (zone inhibition, turbidity, and tetrazolium assays) revealed that the salt A 14 N2S had the ability to kill the Gram-positive bacterium Staphylococcus aureus. Laser scanning confocal microscopy and flow cytometry data taken under various staining conditions suggested reactive oxygen species-mediated RNA depletion as the plausible cause of bacterial cell death in the presence of the gelator salt. Shear thinning of the aqueous gel of A 14 N2S along with its antibacterial activity indicated that it could be a potential candidate for topical application.