Deepak Asthana

Assemblies of perylene diimide derivatives with melamine into luminescent hydrogels

We report unique and spontaneous formation of hydrogels of perylene derivatives with melamine. The luminescent gel network is formed by H-type aggregation of the perylene core, supramolecularly cross-linked by melamine units. As a result of controlled aggregation in the extended nanofibers, strong exciton fluorescence emission is observed.

Single electron transfer-driven multi-dimensional signal read-out function of TCNQ as an "off-the-shelf" detector for cyanide.

Herein we report the first applications of TCNQ as a rapid and highly sensitive off-the-shelf cyanide detector. As a proof-of-concept, we have applied a kinetically selective single-electron transfer (SET) from cyanide to deep-lying LUMO orbitals of TCNQ to generate a persistently stable radical anion (TCNQ(•-)), under ambient condition. In contrast to the known cyanide sensors that operate with limited signal outputs, TCNQ(•-) offers a unique multiple signaling platform. The signal readability is facilitated through multichannel absorption in the UV-vis-NIR region and scattering-based spectroscopic methods like Raman spectroscopy and hyper Rayleigh scattering techniques. Particularly notable is the application of the intense 840 nm NIR absorption band to detect cyanide. This can be useful for avoiding background interference in the UV-vis region predominant in biological samples. We also demonstrate the fabrication of a practical electronic device with TCNQ as a detector. The device generates multiorder enhancement in current with cyanide because of the formation of the conductive TCNQ(•-).

Frontispiece: Appending Diverse π‐Extended Acceptors with Tetrathiafulvalene/Dithiafulvalene Donors: Multistate Redox Properties, Radical Ion Generation, and Mid‐IR‐Absorbing Mixed‐Valence States

Three classes of donor-acceptor (D-A) π-extended chromophores (1-12) were synthesized through a phosphite-mediated cross-coupling reaction, in which the anhydride- or imide-based π-As and number of tetrathiafulvalene (TTF)/dithiafulvalene (DTF) Ds were systematically changed. Large π rings, such as benzoperylene and coronene, were integrated into the TTF/DTF unit, for the first time, to overcome their high insolubility. The anhydride and imide groups in the π acceptors can significantly alter the frontier orbitals and influence the optoelectronic properties. The D moieties allow the formation of radical cations (D.+ ) and the π-extended A moieties aid the formation of radical anions (A.- ) by oxidation/reduction under ambient conditions. The molecules revealed UV/Vis/near-IR absorption, fluorescence extending into the near-IR region, and amphoteric electrochemical properties. Chromophores 10 and 12 show solvatochromism in a wide range of solvents. The π-As with anhydride functionality allow easier electron uptake, relative to the imide groups, whereas the increasing number of D TTF/DTF units make them easy to oxidize. Interestingly, the trans-TTF-fused molecules (1, 6, and 11) exhibited a mixed-valence state in the mid-IR region (ν˜ =5130-4000 cm-1 ). Moderate electron coupling between the redox centers is inferred to the compounds being of Robin-Day class II. The multistate redox activity along with panchromism and near-/mid-IR optical absorption of these systems can be attractive towards advanced switchable materials.

Chapter 4:Functional Molecular and Supramolecular Materials for Electron Transfer Reactions and their Applications

This chapter describes some of the most extensively investigated π-conjugated scaffolds, which have the inherent ability to accept one or more electrons. Thus, the progress of the knowledge of well-known electron acceptors in recent times is deliberated. The focus of the chapter has been to highlight the new developments in the direction of design and synthesis of ambient stable open-shell, multi-anionic and multi-radical based systems and their new age applications. It is realized that weak intramolecular and intermolecular noncovalent interactions play pivotal role towards the delocalization of the unpaired electron and stability of the system. The significance of molecular and crystal engineering principles is discussed, which allow efficient transport of electrons in highly electron deficient systems to confer high charge mobility. The recent advances in molecular design approaches towards non-fullerene based electron acceptors for organic solar cells are illustrated. The photophysical properties of the excited doublet states of these radical anions have been discussed, which have shown that it is possible to control the movement of electrons within a multisite donor–acceptor array on a femtosecond time scale. In addition, the application of the photoexcited radical ions towards C–C bond formation reactions and aryl halide reduction is elucidated. Furthermore, the applications of the radical ions as probes to sense toxic analytes utilizing their attractive multi-channel absorption properties are explained. Finally, we examine the recent progress made en route to utilizing these π-conjugated electroactive materials for organic Li ion batteries.

Self-assembly characteristics of a multipolar donor-acceptor–based bis-pyrene integrated molecular tweezer

AbstractA modular design of a molecular tweezer is presented that integrates a multipolar D- π-A [D: Donor, A: Acceptor] scaffold, 1-aminopyrene-based fluorophore units and L-alanine-based linkers. The synthesis of the molecule is based on two-fold aromatic nucleophilic reactions (ArSN) and coupling reactions of the acid and amino functionalities. This molecule crystallizes in a non-centrosymmteric (P21) space group. We present its rich self-assembly characteristics that involves an array of π-stacking interactions. In addition, the molecular tweezer within its cleft forms H-bonding with two dimethylformamide molecules. Such multipolar D- π-A systems containing chiral and fluorophore units are potential candidates for a number of electronic and photonic applications. Graphical AbstractSelf-assembly of a multipolar scaffold having chiral units and flurophores was observed and characterized.

Self-assembly patterns of steroid-based all-organic ferroelectrics: valuable insights from the single-crystals derived from an organogel and solution

We report herein the first example of a single-crystal grown from a steroid-based organogel matrix. We have delineated the self-assembly process and compared the various non-covalent interactions with that of the single-crystals grown from solution, e.g.1·Ch showed 22 and 14-membered N–H–O H-bonded rings, while 1·Pr exhibited 24 and 14-membered rings. In addition, 1·Ch showed stronger cholesteryl–cholesteryl interactions than 1·Pr and 1·Ch exhibited 55% higher polarization.