Photophysical Approach of Biological Active Benzofuran Derivatized Pyrrole with Green Synthesized Silver NPs Using C. Roseus Leaves: Computational and Spectroscopic Study

The electronic absorption and fluorescence emission spectra of N-(2,5-dimethyl-pyrrol-1-yl)-2-(5-methoxybenzofuran-3-yl)acetamide (DPMA) molecule were recorded in various solvents at room temperature with the aim of estimation of ground state (\({\mu }_{g}\)) and excited states (\({\mu }_{e}\)) dipole moments using Lippert’s, Bakshiev’s and Kawski-Chamma-Viallete’s equations. The results were signified that, the excited state dipole moment is greater than the ground state dipole moment, which indicates the excited state dipole moment is more polar than the ground state dipole moment. Ecofriendly green synthesis of silver nanoparticles (Ag NPs) were synthesized using catharanthus roseus (C.R) leaf extract was done. These synthesized Ag NPs were used as fluorescence quenchers. Fluorescence lifetime measurement is carried out using time correlated single photon counting technique of DPMA molecule with various concentrations of Ag NPs. A linear Stern-Volmer (S-V) plot was obtained in steady state and transient state method. Furthermore we have estimated computational calculations such as ground state optimized geometry, molecular electrostatic potential (MEP), highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), experimental and theoretical energy band gap, solvent polarity and normalized solvent polarity values. Morphology and sizes of green synthesized silver NPs were characterized by transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDX) and also characterized by UV-Visible absorption.

Solvent effect on the absorption and emission spectra of carbon dots: evaluation of ground and excited state dipole moment

Background Carbon dots (C-dots) are photoluminescent nanoparticles with less than 10 nm in size. Today, many studies are performed to exploit the photoluminescence (PL) property of carbon dots, and our focus in this study is to estimate the dipole moment of carbon dots. For reaching our aims, C-dots were synthesized and dissolved in the different solvents. Results Carbon dots with intense photoluminescence properties have been synthesized by a one-step hydrothermal method from a carbon bio-source. In this research, we report on the effect of aprotic solvents on absorption and fluorescence spectra and dipole moments of C-dots dispersed in a range of many aprotic solvents with various polarity and dielectric constant at room temperature. The change in the value of dipole moment was estimated by using the Stokes shifts. The difference between the dipole moment of the excited state and the ground state was shown using an extended form of Lippert equations by Kawski and co-workers. Conclusions The values found for μg = 1.077 D, and μe = 3.157 D, as well as the change in the dipole moments. The results showed that the dipole moment of the excited state is more than the ground state, indicating a high density and redistribution of electrons in the excited state. Finally, the quantum yield of C-dots in the eclectic aprotic solvents was communicated and discussed.

Polarity- and molecular orbital-engineered host materials for stable and efficient blue thermally activated delayed fluorescence

To utilize thermally activated delayed fluorescence (TADF) technology for future displays, it is necessary to develop host materials that can harness the full potential of blue TADF emitters. We suggest an elaborative approach for designing host molecules for blue TADF devices with simultaneously improved efficiency and stability. We significantly enhanced the delayed fluorescence quantum yield by engineering the molecular geometry, polarity, and excited-state dipole moment of host molecules based on 3′,5-di(9H-carbazol-9-yl)-[1,1′-biphenyl]-3-carbonitrile. The engineerd hosts stabilized the charge-transfer excited states of TADF emitters, suppressed exciton quenching, and improved the charge balance in the emitting layer. Moreover, because the hosts are phosphine-oxide bond-free molecules, they are photochemically and electrochemically stable compared to bis[2-(diphenylphosphino)phenyl] ether oxide, the most popular high-polarity host. The devices employing the hosts exhibited a two-fold increase in external quantum efficiency and a 37-fold increase in operation lifetime compared to control devices with the same TADF emitter.

Computational and Spectral Means for Characterizing the Intermolecular Interactions in Solutions and for Estimating Excited State Dipole Moment of Solute

The results obtained both in quantum chemical computation and in solvatochromic study of pyridinium di-carbethoxy methylid (PCCM) are correlated in order to estimate the electric dipole moment in the excited state of this molecule. This estimation is made by a variational method in the hypothesis that the molecular polarizability does not change in time of the absorption process. Ternary solutions of PCCM in protic binary solvents are used here, both establishing the contribution of each type of interaction to the spectral shift and to characterize the composition of the first solvation shell of PCCM. Results are compared with those obtained before for other binary solvents. The difference between the interaction energies in molecular pairs of PCCM-active solvent and PCCM-less active solvent was also estimated based on the cell statistical model of the ternary solutions.

New QSAR and Solvatochromic Estimation of Molecular Parameters of Chlortetracycline

The present paper is focused on determination of the main parameters of Chlortetracycline. Chlortetracycline belongs to one of the most used family of antibiotics worldwide, Tetracyclines. Because of the large spectrum of infections which can be treated with this category of antibiotics there are attempts to find new derivatives from this class. The compounds derived from the same basic structure exhibit same chemical properties, that is why knowing in detail the main physico-chemical properties of Chlortetracycline could be a real help in synthesize new efficient derivatives. In order to evaluate the reactivity and biological activity HyperChem was used to establish the optimized structure, the electro-optical, the energetic and QSAR parameters. The solvatochromic methods allowed determining the intermolecular interactions types and their contribution to the spectral shifts of measured electronic absorption bands. Based on computational and solvatochromic results, the excited state dipole moment of Chlortetracycline was established by variation method.

Solvatochromic Study of Supramolecular Amphiphile Based on Calix[4]arene Connected to a Fluorescent Benzofurazan Moiety at Lower Rim: Evaluation of Ground and Excited State Dipole Moments-=SUP=-*-=/SUP=-

Photophysical properties of a supramolecular amphiphile of calix[4]arene having benzofurazan moiety at the lower rim, L has been studied. Electronic absorption and fluorescence spectra of L have been recorded in wide range of solvents of different polarities and data were used to study solvatochromic properties. The ground state and the excited state dipole moment of L were estimated from the Bakhshiev's and Bilot-Kawaski's equations. High value of dipole moment is observed for excited state as compared to ground state value and this is attributed to more polar excited state of molecule. Also, fluorescence emission peak undergoes a bathochromic shift with increase in the polarity of the solvent, confirming π-> π* transition. Scanning electron microscopy reveals that the aggregation of L is increased on going from the polar to non polar solvents. Keywords: solvatochromism, benzofurazan, dipole moment, quantum yield, absorption, fluoresence.

Ground and Excited State Dipole Moment of 2,5-Dihydroxybenzoic Acid from Solvatochromic Shifts

In present work we explore the role of solvents on the 2, 5-dihydroxybenzoic acid by using fluorescence techniques. It was found that DHBA shows spectral behaviour depending on polarity of solvents. DHBA shows generally three components at 405-415nm, 430-450nm, and 450-470nm. The effects of zwitterion as well as the interplay ionic species are involved to explain the observed results