Solvation controlling reaction paths and gel-formation in imide derivatives

Sequential effects of two cations on the fluorescence emission of a coordination polymer with Zn4O core in node

Distinct changes in the fluorescence emissions of free ligand 5-(1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)isophthalic acid (H2NAPHISO) than a 2D-zinc-coordination polymer of it, caused by sequential interactions with different sets of binary cations were observed. The coordination polymer having unsymmetrical Zn4O core of tetranuclear zinc-node could be dispersed in dimethylformamide without its degradation. The coordination polymer had an emission peak at 435 nm (quantum yield = 0.082) which was selectively quenched by adding Fe2+ ions. Based on this quenching, the Fe2+ ions in aqueous solution could be detected with a detection limit 42.57 nM. The metal ions such as Li+, Na+, Cd2+, Hg2+, Al3+ did not interfere in the detection; but each of these ions together with Fe2+ ions showed characteristic shift of the emission spectra. The H2NAPHISO in dimethyl formamide was non-fluorescent, but showed emission at 452 nm upon addition of Cd2+ or Zn2+ ions. This new emission of H2NAPHISO caused by zinc or cadmium ions was not quenched by Fe2+ ions. Various cations had affected the emission of the H2NAPHISO with Zn2+ which was much different from the corresponding changes caused by the same ion on the emission of the coordination polymer. For example, the Mn2+ and Zn2+ ions together in a solution of the ligand showed a broad emission spectrum spreading over 380-450 nm, but ions Sn2+ and Zn2+ together had showed emission at a shorter wavelength (380 nm). These allowed to modulate the emission of the ligand by binary combination of metal ions.

Bipyridine based metallogels: an unprecedented difference in photochemical and chemical reduction in the in situ nanoparticle formation

Metal co-ordination induced supramolecular gelation of low molecular weight organic ligands is a rapidly expanding area of research due to the potential in creating hierarchically self-assembled multi-stimuli responsive materials. In this context, structurally simple O-methylpyridine derivatives of 4,4'-dihydroxy-2,2'-bipyridine ligands are reported. Upon complexation with Ag(i) ions in aqueous dimethyl sulfoxide (DMSO) solutions the ligands spontaneously form metallosupramolecular gels at concentrations as low as 0.6 w/v%. The metal ions induce the self-assembly of three dimensional (3D) fibrillar networks followed by the spontaneous in situ reduction of the Ag-centers to silver nanoparticles (AgNPs) when exposed to daylight. Significant size and morphological differences of the AgNP's was observed between the standard chemical and photochemical reduction of the metallogels. The gelation ability, the nanoparticle formation and rheological properties were found to be depend on the ligand structure, while the strength of the gels is affected by the water content of the gels.

Competing phenol–imidazole and phenol–phenol interactions in the flexible supramolecular environment of N,N′-bis(3-imidazol-1-ylpropyl)naphthalenediimide causing domain expansion

Spectroscopic and crystallographic studies on cocrystals of N,N′-bis(3-imidazol-1-yl-propyl)naphthalenediimide (L) with a series of phenolic compounds have revealed that competition to form phenol–imidazole and phenol–phenol synthons causes domain expansion.

Cyclic aromatic imides as a potential class of molecules for supramolecular interactions

Prospects of stacking interactions of imides beneficial to generation of new soft materials are projected by analysing examples of primary building blocks that provide a basis for understanding at the molecular level.

Benzimidazole derivatives: synthesis, physical properties, and n-type semiconducting properties

A series of new benzimidazole derivatives were synthesized by the solid-state condensation and direct sublimation (SSC-DS) method and their physical properties were investigated. The reaction yields and product stability were significantly affected by the identity of the diamine and anhydride substituents. On the other hand, the substituents of the benzimidazole ring allowed fine tuning of the emission maxima, fluorescence quantum yields, and redox potentials. The HOMO-LUMO levels were estimated by cyclic voltammetry in film on indium tin oxide (ITO) and compared with values obtained by other methods. The described benzimidazoles showed high crystallinity, which is attributed to a high planarity and interactions between carbon and heteroatoms. These compounds showed n-type semiconducting behavior in organic field-effect transistors (OFETs). Optimized devices for fluorinated NTCBI (naphthalene tetracarboxylic bisbenzimidazole) showed respectable electron mobilities of ∼10(-2)  cm(2)  V(-1)  s(-1) .