Bis-(1-(2-aminoethyl)piperidino), (2-(2-aminoethyl)pyridino) and (1-(2-aminoethyl)pyrrolidino)-substituted dicyanoquinodimethanes: consequences of flexible ethylene spacers with heterocyclic moieties and amine functionalities

Abstract

Heterocyclic building blocks possessing ethylene spacer and amine functionality such as 1-(2-aminoethyl)piperidine (1,2-AEPi), 2-(2-aminoethyl)pyridine (2,2-AEPy) and 1-(2-aminoethyl)pyrrolidine (1,2-AEPr) were reacted with tetracyanoquinodimethane (TCNQ) to give disubstituted compounds namely bis-(1-(2-aminoethyl)piperidino)dicyanoquinodimethane (1), bis-(2-(2-aminoethyl)pyridino)dicyanoquinodimethane (2) and bis-(1-(2-aminoethyl)pyrrolidino)dicyanoquinodimethane (3). Utilization of 1,2-AEPi, 2,2-AEPy and 1,2-AEPr as disubstituents on TCNQ has resulted in interesting crystal structures. Inter- and intramolecular hydrogen-bond mediated and expanded supramolecular structures were observed in the lattices of the crystals. Strong fluorescence was observed in solids and solutions. (2) showed a strong second harmonic generation (SHG) whereas (1) and (3) were found to be SHG inactive. All compounds possess good thermal stabilities.

Distinct Tetracyanoquinodimethane Derivatives: Enhanced Fluorescence in Solutions and Unprecedented Cation Recognition in the Solid State

“…Originally, TCNQ derivatives were exploited as potential candidates for second-order nonlinear optical (NLO) materials ,, due to their large hyperpolarizabilities (β). − Recently, a substantial study on the optical property of TCNQ derivatives has been conducted. Specifically, mono/di-substituted TCNQ (DADQ) fluorophores developed by the reaction of TCNQ with various heterocyclic, − aliphatic, , and countable (∼5) aromatic amines, − precisely with primary and secondary amines, resulted in a divergent phenomenon like aggregation-enhanced solid-state emission, ,, colloids, nanoparticles, − phase change attributes, − and second-harmonic generation (SHG). − Reasonable fluorescence in TCNQ derivatives as solutions was due to noncovalent interactions, strong hydrogen bonding, and self-assembly . However, enhanced fluorescence in solids was observed due to aggregation, , strong intermolecular attractions, ,− restricted geometric relaxation in excited states, ,,,, and decrease in intermolecular interactions like π–π/CH−π, − in comparison to solutions.…”

“…Specifically, mono/di-substituted TCNQ (DADQ) fluorophores developed by the reaction of TCNQ with various heterocyclic, − aliphatic, , and countable (∼5) aromatic amines, − precisely with primary and secondary amines, resulted in a divergent phenomenon like aggregation-enhanced solid-state emission, ,, colloids, nanoparticles, − phase change attributes, − and second-harmonic generation (SHG). − Reasonable fluorescence in TCNQ derivatives as solutions was due to noncovalent interactions, strong hydrogen bonding, and self-assembly . However, enhanced fluorescence in solids was observed due to aggregation, , strong intermolecular attractions, ,− restricted geometric relaxation in excited states, ,,,, and decrease in intermolecular interactions like π–π/CH−π, − in comparison to solutions. Currently, the inadequacy of TCNQ derivatives with considerable fluorescence in solution and in solid state is a severe limitation; furthermore, cation recognition by mono/di-substituted TCNQ derivatives has not been discovered yet.…”

Design and Development of Distinct Tetracyanoquinodimethane Derivatives Exhibiting Dual Effect of Fluorescence and Anticancer Activity

“…In [1] the central ring (C1À C6) was benzenoid with an average carbon-carbon bond distance of ∼ 1.398 Å, owing to zwitterionic nature. [37][38] The diaminomethylene unit in [1] was found to be completely twisted with reference to the benzenoid ring plane accompanied by torsion angles τ N4À C8À C3À C2 = 0.26°, τ C8À N4À C17À C16 = 50.60°. Angle between the benzeniod ring planes in [1] was 54.37°.…”

“…Molecular packing diagrams for [ 1 ], [ 2 ] with dipoles arranged in antiparallel fashion is shown in Figure 2. In [ 1 ] the central ring (C1−C6) was benzenoid with an average carbon‐carbon bond distance of ∼1.398 Å, owing to zwitterionic nature [37–38] . The diaminomethylene unit in [ 1 ] was found to be completely twisted with reference to the benzenoid ring plane accompanied by torsion angles τ N4−C8−C3−C2 =0.26°, τ C8−N4−C17−C16 =50.60°.…”

“…Dendritic (branched) feature was perceived in [ 7 ]. Different morphology observed in the films, obtained from various solvents is probably due to different molecular assemblies, based on solvent polarity and diffusion ability, indicating disparate evaporation rates accomplished by various molecular structures and incompatible growth kinetics [37,48] …”