Efficient Standalone Flexible Small Molecule Organic Solar Cell Devices: Structure-Performance Relation Among Tetracyanoquinodimethane Derivatives.

Currently, very few dicyano and tetracyanoquinodimethane (TCNQ) based molecules are utilized as active layers, sandwiched between the electron and hole transport layer in organic solar cell (OSC) devices. Nevertheless, simple mono- and disubstituted TCNQ derivatives as exclusively active layers are yet unexplored and provide scope for further investigation. In this study, TCNQ derivatives with varying amine substituents, namely, AEPYDQ (1), BMEDDQ (2), MATBTCNQ (3), and MITATCNQ (4), were explored as efficient standalone, flexible, all small molecule OSC devices. Particularly, 1 resulted in the highest device efficiency of 11.75% with an aromatic amine, while 2 possessing an aliphatic amine showed the lowest power conversion efficiency (PCE; 2.12%). Notably, the short circuit current density (JSC) of device 1 increased from 2 mA/cm2 in the dark to 9.12 mA/cm2 under light, indicating a significant boost in the current generation. Further, 1 manifested more crystallinity than others. Interestingly, 4 exhibited a higher PCE (5.90%) than 3 (PCE is 2.58%), though 3 is disubstituted with an aromatic amine, probably attributed to the electron-withdrawing effects of the -CF3 and -CN groups in 3 reducing the available π-electron density for stacking. Therefore, this study emphasizes crystallinity, significantly on the PCE, offering insights into the design of many such efficient OSCs.

Spirocyclic rhodamine B benzoisothiazole derivative: a multi-stimuli fluorescent switch manifesting ethanol-responsiveness, photo responsiveness, and acidochromism.

Multi-stimuli fluorescent switching materials have been extensively employed in chemistry, biochemistry, physics, and materials science. Although rhodamine-based spirolactams have been specifically considered for metal ion sensing by photoluminescence, only some of them manifest photochromic behavior, and further development of rhodamine B (RHB)-based photochromic materials is required. RHB and its cyclic amides are advantageous in various sensing applications owing to their colorimetric responses to external stimulation. Hence, the current work reports a novel multifunctional active molecular material (3',6'-bis(diethylamino))-2-(5-nitrobenzo[c]isothiazol-3-yl)spiro[isoindoline-1,9'-xanthen]-3-one (RHBIT) by linking rhodamine B with 3-amino,5-nitro[2,1]benzoisothiazole (ANB) in a facile synthetic pathway; that perceives both emission color change and switching between off-on states. RHBIT shows acidochromism, photochromism, and pH sensitivity accompanied by unique ethanol responsiveness, with potential applications in anti-counterfeiting and drug delivery. Notably, RHBIT is highly acid sensitive and reverts to the ring-closed form on treatment with triethylamine (base), visible with the naked eye amidst colorless-pink-colorless transformations. On short UV irradiation, RHBIT provides a two-fold rise in the lifetime for the ring-open form in CHCl3 and DCM compared to the spirolactam (closed form). DFT and TDDFT studies provide electronic characterization for the absorption spectra of the open and closed forms. Using the photoresponsive feature of RHBIT, an information protection application has been enacted via a rewritable platform.

7,7-bis(N, N-diethylethylenediamino)-8,8-dicyanoquinodimethane: Effect of Ethyl Moiety on the Photophysical Property besides Thermal Stability.

Tetracyanoquinodimethane (TCNQ) on reaction with primary/secondary amines sequels in mono/di-substituted TCNQ adducts known as diaminodicyanoquinodimethanes (DADQ's) possessing astounding optical or non-linear optical characteristics. Crucially, the subtle choice of amine contributes to the outcome of molecular material aspects. Herein, we present a comprehensive investigation of 7,7-bis(N,N-diethylethylenediamino)-8,8-dicyanoquinodimethane (BDEDDQ); manifesting the impact of ethyl group (existing on the di-substituted nitrogen of N,N-diethylethylenediamine (DEED)); on the crystal structure, optical property and thermal stability. Crystallography study revealed supramolecular self-assemblies among molecular dipoles emanating fluorescence enhancement in the solid state compared to solutions. Quantum yields were primarily ~0.2 to 0.4% in solutions and ~56% in the solid. Stokes shift was noticed to be more in solutions (~90 nm) than solid (~67 nm), suggesting excess vibrational relaxations in solutions. Differential scanning calorimetry revealed ~182 °C as the melting temperature. The heat capacity of solid was found to be 5.03 mJs-1. Thermogravimetric analysis conveyed single stage decomposition process initiated by the two amine side chains. Scanning electron microscopy of films prepared by drop casting solutions imparted divergent morphological features, due to different rates of evaporation accompanied by varied growth kinetics. Accordingly, in this paper we have demonstrated the utilization of simple N,N-diethylethylenediamine (DEED) to successfully generate a noteworthy blue emissive molecular material exhibiting semiconducting feature besides reasonable thermal stability.

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

Tetracyanoquinodimethane (TCNQ) is known to react with various amines to generate substituted TCNQ derivatives with remarkable optical and nonlinear optical characteristics. The choice of amine plays a crucial role in the outcome of molecular material attributes. Especially, mono/di-substituted TCNQ's possessing strong fluorescence in solutions than solids are deficient. Furthermore, cation recognition in the solid-state TCNQ derivatives is yet undetermined. In this article, we present solution-enhanced fluorescence and exclusive solid-state recognition of K+ ion achieved through the selection of 4-(4-aminophenyl)morpholin-3-one (APM) having considerable π-conjugation and carbonyl (C=O) functionality, particularly in the ring. TCNQ when reacted with APM, in a single-step reaction, resulted in two well-defined distinct compounds, namely, 7,7-bis(4-(4-aminophenyl)morpholin-3-ono)dicyanoquinodimethane (BAPMDQ [1], yellow) and 7,7,8-(4-(4-aminophenyl)morpholin-3-ono)tricyanoquinodimethane (APMTQ [2], red), with increased fluorescence intensity in solutions than their solids. Crystal structure investigation revealed extensive C-H-π interactions and strong H-bonding in [1], whereas moderate to weak interactions in [2]. Surprisingly, simple mechanical grinding during KBr pellet preparation with [1, 2] triggered unidentified cation recognition with a profound color change (in ∼1 min) detected by the naked eye, accompanied by a drastic enhancement of fluorescence, proposed due to the presence of carbonyl functionality, noncovalent intermolecular interactions, and molecular assemblies in [1, 2] solids. Cation recognition was also noted with various other salts as well (KCl, KI, KSCN, NH4Cl, NH4Br, etc.). Currently, the recognition mechanism of K+ ion in [1, 2] is demonstrated by the strong electrostatic interaction of K+ ion with CO and simultaneously cation-π interaction of K+ with the phenyl ring of APM, supported by experimental and computational studies. Computational analysis also revealed that a strong cation-π interaction occurred between the K+ ion and the phenyl ring (APM) in [2] than in [1] (ΔG binding calculated as ∼16.3 and ∼25.2 kcal mol-1 for [1] and [2], respectively) providing additional binding free energy. Thus, both electrostatic and cation-π interactions lead to the recognition. Scanning electron microscopy of drop-cast films showed microcrystalline "roses" in [1] and micro/nano "aggregates" in [2]. Optical band gap (∼3.565 eV) indicated [1, 2] as wide-band-gap materials. The current study demonstrates fascinating novel products obtained by single-pot reaction, resulting in contrasting optical properties in solutions and experiencing cation recognition capability exclusively in the solid state.

Quality by Design Approach to Develop Stability Indicating Method to Quantify Related Substances and Degradation Products of Sacubitril by High Performance Liquid Chromatography.

Sacubitril (SBT) is a neprilysin inhibitor, approved by food and drug administration (FDA) in 2015, under the FDA's priority review process. In this work, we report the validated stability indicating method of SBT by employing quality by design (QbD) principles related to analytical method development, capable in separation of 11 impurities. Chromatographic separation was performed on an ascentis phenyl hexyl column using 10 mM KH2PO4 as a mobile phase-A and the pH adjusted to 2.1. Methanol: acetonitrile (70:30 v/v) solvent mixture was employed as the mobile phase-B in a gradient mode of elution at a flow rate 0.8 mL/min at 30°C. The column effluents were monitored by a photo diode array detector set at a wavelength of maximum absorption 254 nm noted for all the impurities and furthermore for SBT. This method was remarked to be accurate in the range from 92 to 116%, precise with relative standard deviation 0.9% for SBT (0.8 mg/mL) and 1.0 to 2.1% for its related impurities (0.0005 mg/mL) also linear with correlation coefficient r ≥ 0.9989. The limits of quantification for all impurities were 0.05% with respect to sample concentration 0.8 mg/mL. The developed method revealed a good method operable design range for the experimental chromatographic conditions. Forced degradation of SBT carried under acidic, basic and oxidative stressed conditions manifested that the method is stability indicating.