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In this study, the computational studies of the PO3H2, CONHOH, and SO2H (A1–A3) molecules were investigated for optoelectronic applications on the basis of tetrahydroquinoline (C1-1) dye. Besides, a detailed calculation of the molecular structures, energy levels, driving force of injection, regeneration, non-linear optical (NLO) property, chemical hardness, excitation binding energy, light-harvesting efficiency (LHE), absorption spectra, and photovoltaic (PV) parameters were all discussed in details using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. The optoelectronic properties of C1-1-based A1–A3 molecules are originated to be tuned by changing the position of the acceptor. To get a maximum absorption spectrum of C1-1, Becke's three-parameter and Lee–Yang–Parr (B3LYP), Coulomb-attenuating method-B3LYP (CAM-B3LYP), and Head-Gordon model (ωB97XD) were used for the TD-DFT method. Results reveal that the TD-ɷB97XD and 6-31G(d) combined functionals were provided reliable effects to the C1-1. Therefore, absorption spectra of the A1–A3 dyes were followed by the TD-ɷB97XD/6-31G(d) techniques. The designed A1 (PO3H2) dye displayed a smaller energy gap and red-shifted broadened spectra than the other dyes and C1-1 can be utilized to get a better PV properties. In addition, NLO properties of the A1–A3 chromophores were calculated by the polarizability and first-order hyperpolarizability. Consequently, A1 dye has a superior value of the NLO activity. This study will deliver a valuable reference to the upcoming molecular proposal of tetrahydroquinoline dyes for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Based on (E)-2-cyano-3-(5-(2-(4-(dimethylamino)phenyl)ethynyl)thiophene-2-yl)acrylic acid (CSD-01) dye, newly designed isolated organic (CSDS1-CBDS7) molecules were investigated for dye-sensitised solar cells (DSSCs) application using the density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The electronic and optimised geometry of the CSDS1–CSDS7 derivatives were contained in the electron-donor (D), π-linker (π) and electron–acceptor (A) groups to form a D–π–A structure. Different hybrid functionals were used to get a maximum value of optical absorption UV-Vis peak in CSD-01 dye. Accordingly, a ωB97XD was sensibly found by calculating the UV-Vis in CSD-01. Further, UV-Vis spectra were used to design newly efficient sensitisers by the TD-DFT-ωB97XD-6-31G(d) theory. The CSDS1–CSDS7 dyes were implemented on the driving force of the electron injection ( Δ G inject ), dye regeneration ( Δ G reg ), dipole moment ( μ normal ), light-harvesting efficiency, theoretical open-circuit photovoltage ( e V OC ), excited-state lifetime (τ), the density of state, the exciton binding energy ( E b ) and molecular electrostatic potential. The highest occupied molecular orbitals below the redox electrolyte and lowest unoccupied molecular orbitals above the conduction band edge of the TiO2 surface were successfully identified. Finally, the newly CSDS5 and CSDS6 structured sensitisers were offered theoretical tools for highly efficient organic photosensitisers for further research. [ABSTRACT FROM AUTHOR]

A novel symmetrical indolo[3,2- b ]carbazole derivative ( ICZ-CN ) containing dicyanovinyl groups has been designed and synthesized. The typical D-π-A type conjugated compound exhibited an obvious intramolecular charge transfer (ICT) property, which was evidenced by UV-vis absorption, fluorescent emission spectroscopy and density functional theory (DFT) calculations. Meanwhile, ICZ-CN exhibited a strong aggregation-enhanced emission (AEE) characteristic. Interestingly, compound ICZ-CN showed a reversible mechanofluorochromic (MFC) property between yellow and orange-red emission by grinding-fuming processes. The MFC mechanism was investigated through the single crystal structure, the scanning electron microscope (SEM) and the powder X-ray diffraction (XRD). The results showed that the mechanofluorochromic property is attributed to the loose molecular packing by weak intermolecular hydrogen bond interactions was destroyed and generated the phase transformation from crystalline to amorphous states under external stimulations. The results would be of great help in understanding and designing new MFC materials. [ABSTRACT FROM AUTHOR]

Facile probing organic solvents is attracting intense attention due to the growing environmental issues. Herein, for the first time, we report a novel D-π-A structured methanol responsive fluorescence molecule (TTO), synthesized by coupling triphenylamine (electron-donor) and p -toluenesulfonyl (electron-acceptor) via Cu (I) catalytic 1,3-dipolar cycloaddition (click chemistry) forming a triazole bridge. Density functional theory (DFT) calculations and X-ray single crystal structure reveal that TTO has a highly twisted conformation and unique D-π-A structure which render it exceptional optical properties. TTO exhibits strong fluorescence in methanol (QE > 0.67) but weak fluorescence in other organic solvents (QE < 0.1) including various alcohols and can be used as a highly selective fluorescence probe for methanol identification. Notably, TTO is able to excellently probe methanol from its homologue ethanol in water with a detection limit of below 0.7% (volume concentration), which demonstrates the promise potential of TTO for practical applications. [ABSTRACT FROM AUTHOR]

Donor-π bridge-acceptor (D-π-A) design principle has been widely employed to build functionalized materials with excellent optical properties, whereas its feasibility in electrocatalytic reactions is seldom investigated. We demonstrate the primary study of D-π-A rule in constructing electrocatalysts for oxygen reduction reaction (ORR) purpose by rationally designing three cobalt porphyrins EGZ1–3 with 9H-carbazole, triphenylamine and N,N-diphenyl-[1,1′-biphenyl]-4-amine as the donor substituents, respectively, cobalt porphyrin as the π bridge, and cyanoacrylic acid as the acceptor unit. The electronic properties of the molecules are calculated using the density functional theory and the composite catalysts EGZs/C are characterized by a series of spectroscopic approaches. The electrochemical measurements show that EGZ3/C attains a more positive reduction potential and a greater response current density than EGZ1/C and EGZ2/C, which is possibly due to the optimized electronic structure and the substituent effect. The electron transfer number as well as hydrogen peroxide generation yield values suggest slightly better selectivity of EGZ3/C and EGZ2/C than those of EGZ1/C (i.e., ~ 2.9, ~ 2.9 vs. ~ 2.7 and ~ 54%, ~ 53% vs. ~ 62%, respectively) towards full oxygen reduction. Our result reveals the feasibility of the D-π-A design rule and the importance of molecular electronic state and the substituent feature in constructing ORR electrocatalysts. [Display omitted] • Three donor-π-acceptor cobalt porphyrins are synthesized. • The electronic structure of porphyrins is calculated by density functional theory. • Porphyrin-carbon black composites are studied in oxygen reduction reaction. • The electrocatalyst EGZ3/C attains the best ORR performance. • Both electronic structure and substituents affect the electrocatalytic activity. [ABSTRACT FROM AUTHOR]

Two new D-π-A-structured dyes (SGT-160 and SGT-161) with the extension of π-conjugation in the acceptor unit have been designed and synthesized to modulate LUMO energy levels and to investigate the photophysical and electrochemical properties as well as cell performances. Based on a reference dye of SGT-130 as a platform of donor-π-bridge-BTD-phenyl-acceptor sensitizers, ethynylphenylene (T-Ph) and 2-ethynylthiophene (T-Th) moieties as an auxiliary π-spacer were introduced to replace the traditional phenylene (Ph) moiety for SGT-160 and SGT-161, respectively. It was found that the insertion of an additional ethynyl moiety into the BTD-Ph acceptor unit significantly enhanced the light-harvesting capability by extending the absorption bands and intensifying the molar absorptivity. Moreover, the π-extension in the acceptor part was beneficial for stabilizing the LUMO energy levels. The density functional theory (DFT) calculations and the partial density of states (PDOS) suggest that the variation of acceptor units affects the electronic transition between the major orbitals of the dyes. As a result, dye-sensitized solar cells (DSSCs) based on SGT-160 with a chenodeoxycholic acid (CDCA) co-adsorbent exhibited high power conversion efficiencies (PCEs) of 10.28%, while DSSCs based on SGT-161 and SGT-130 showed moderate PCEs of 8.05% and 10.06%, respectively. [Display omitted] • D-π-A structured organic dyes of SGT-130, SGT-160 and SGT-161 were designed and synthesized. • The effect of auxiliary ethynyl-based acceptor units on the photovoltaic properties was investigated. • The introduction of π-extended acceptors is a rational design strategy to improve light-harvesting capability. • SGT-160-based DSSCs showed a better PCE (10.28%) than other dyes. [ABSTRACT FROM AUTHOR]