Modulation of Fluorescence Emissions of Copper(II) 2,2′-biquinoline-4,4′-dicarboxylates

Abstract

Interplay of weak interactions of di‐aqua‐bis‐ethylenediammine copper(II) 2,2′‐biquinoline‐4,4′‐dicarboxylate hydrate (1) were used to modulate solid state fluorescence emissions. Complex 1 forms porous self‐assembly in solid state by hydrogen bonds between cations, anions and lattice water molecules. Fluorescence spectroscopy, thermogravimetry, powder XRD, IR‐spectroscopy and surface analysis were used to establish the breakdown and regeneration of porous hydrogen bonded sub‐assemblies by dehydration and rehydration. Complex 1 is non‐fluorescent in solid state but anhydrous form of the complex 1 is highly fluorescent. In the solid state self‐assembly of the complex 1, π‐stacking among biquinoline rings contributes to quenching. Dehydration of solid sample of complex 1 generates a fluorescent state, and subsequent absorption of moisture by the anhydrous complex quenches fluorescence. In solution, competition between chelation by ethylenediamine and coordination by 2,2′‐biquinoline‐4,4′‐dicarboxylic acid with copper(II) ions is reflected in the ON and OFF states generated by judicious manipulation of chelation effects. Complex 1 is one among a series of bis‐chelated ethylendiamine copper(II) aromatic carboxylate complexes which have layered structures. It is also a precursor of nano‐dimensional copper oxide; 25–50 nm size copper oxide particles are formed by thermal decomposition of complex 1 at 500 °C.

Changes in Emission Properties by π‐Stacking and Conformation Adjustment of an Imidazole‐Tethered Naphthalimide Derivative

“…Among the weak interactions, the π‐interactions between two aromatic rings may occur in different ways. The contributions from each interacting counterpart in solid and solution influence the fluorescence emission properties of a compound, accordingly the emission features of a solid sample may differ from the features observed from solution of the same fluorescent compound . We set to study in this study a naphthalimide molecule N‐(3‐imidazol‐1‐yl‐propyl)‐1,8‐naphthalimide (abbreviated as imidanap ), which has a naphthalimide ring attached through a propylene tether connecting an imidazole unit.…”

Changing π-Interactions and Conformational Adjustments of N-(Isonicotinylhydrazide)-1,8-naphthalimide by Hydration and Complexation Affect Photophysical Properties

“…With the relative differences in fluorescence emission quenching one can differentiate the nitro-phenols through such a study (Figure d). The aggregation induced emission of certain naphthalimide derivatives has been explored; , on the other hand the hydration of metal–organic frameworks and self-assemblies of inorganic complexes or organic compounds are commonly used for detection of water in solvent by fluorescence modulation, − but our present findings clearly depict that in the case of an ICT driven fluorophore such as HL the native fluorescence state matters that can be fine-tuned to switch on and off by changing the parameters contributing to the orientation of the group contributing to stabilize such a state controlling interactions among the chromophore or modifying electron delocalization. On the other hand, the fluorescence sensing of nitro compounds by fluorescence ON and OFF process shown by receptors such as quantum dots and inorganic, organic receptors are widely studied; − the present example also adds one to such possibility with a difference that the aggregation induced state can be first generated through water and further exploited to quench emission from such a state by adding aromatic nitro-phenolic compounds.…”

“…Naphthalimide derivatives are used to encapsulate guests causing change in fluorescence, − but in the present case we clearly depict an example to show the differences in fluorescence caused by hydration. Although there are examples in which the reversible dehydration and rehydration affecting fluorescence are well demonstrated in metal–organic frameworks or noncovalent assemblies, − the present system is clear to depict the packing changes. In the present case no porous desolvate was formed making the emission changes irreversible after dehydration.…”

Stepwise Solution-Interfacial Nanoarchitectonics for Assembled Film with Full-Color and White-Light Circularly Polarized Luminescence

“…Coordination-Regulated Film Chiroptical Properties. Biquinoline is a typical bidentate ligand and is able to coordinate with various types of metal ions, 57,58 which might be used to manipulate the assembly and chiroptical properties of BQGE. As expected, the emission color of BQGE agg moved from blue to yellow after coordination with Zn 2+ cations by formation of BQGE/Zn 2+ aggregate, (BQGE/Zn 2+ ) agg , while other metal ions led to unchanged blue emission or quenched emission (Figure 3a).…”