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Novel A2-D-A1-D-A2 type NIR absorbing symmetrical squaraines based on 2, 3, 3, 8-tetramethyl-3H-pyrrolo [3, 2-h] quinoline: Synthesis, photophysical, electrochemical, thermal properties and photostability study
摘要： Two novel acceptor–donor-acceptor-donor-acceptor type pi-conjugated symmetrical squaraine dyes, denoted by PQSQ 1 and PQSQ 2 based on 2, 3, 3, 8-tetramethyl -3H-pyrrolo [3,2-h] quinoline were successfully synthesized for the first time to arrive absorption and emission at NIR region. These dyes comprise indolenines as electron donor units, squaryl ring as a central electron acceptor and pyridines as terminal electron acceptor units. The relationship between molecular structures and photophysical properties of these dyes was studied in comparison with their parent compounds (ISQ and N-Et ISQ). These novel squaraine dyes displayed an intense absorption within the range 671 to 692 nm in polar to non- polar solvents respectively with good molar extinction coefficients (? 105 Lmol-1cm-1). Compared to their parent squaraines, both dyes showed red-shifted absorption (33 - 44 nm) as well as emission (38 - 59 nm) due to the electron-accepting ability of the ancillary pyridine acceptors and extended pi-conjugation. These dyes exhibited negative solvatochromism and Reichardt's ET (30) scale was applied to propose a quantitative relationship of the relative stability of ground and excited-state of these squaraines with solvent polarity. The electrochemical and computational properties of these symmetrical squaraines were investigated with the help of cyclic voltammetry and density functional theory (DFT). Moreover, PQSQ 1-2 exhibited high thermal and photo-stability. These A2-D-A1-D-A2 type dyes showed improved photostabilities compared to their parent D-A-D type dyes.
关键词： 2, 3, 3, 8-tetramethyl -3H-pyrrolo [3, 2-h] quinoline,NIR absorbing dyes,acceptor-donor-acceptor-donor-acceptor,squaraines,DFT computations,red shift
更新于2025-09-23 15:21:21
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Dicyanovinylene and Thiazolo[5,4-d]thiazole-Core Containing D-A-D Type Hole Transporting Materials for Spiro-OMeTAD Free Perovskite Solar Cell Applications with Superior Atmospheric Stability
摘要： In perovskite solar cell (PSC) devices, hole transporting materials (HTMs) are vital components affecting the charge separation and play an important role in achieving high efficiencies. These may also protect active light-absorbing layers from degradation. The current best-in-class HTM Spiro-OMeTAD is prohibitively expensive for large scale application and hence design of novel cost-effective HTMs yielding comparable device performance is essential. In this manuscript, we report synthesis of donor-acceptor-donor (D-A-D) type hole transporting materials (TTz-1 and TPDCN) featuring the dicyanovinylene and thiazolo[5,4-d]thiazole cores and evaluate their performance via integrating them in perovskite solar cells (PSCs). The results suggest that both the HTMs are easy to synthesize and demonstrate favourable structural characteristics for device integration. Detailed analysis reveals that the molecules showed appropriate energy level alignment with methylammonium lead iodide (CH3NH3PbI3) perovskite, possess good thermal stability and high hole mobility. Planar PSC devices fabricated using TTz-1 as HTM yielded a power conversion efficiency (PCE) of 11.37%, whilst devices using TPDCN shows a PCE of 10.11%, comparable to PCE of 11.62% obtained in control samples based on Spiro-OMeTAD. In additional, stability analysis of the devices shows that devices fabricated using TTz-1 and TPDCN exhibit superior atmospheric stability as compared to those based on Spiro-OMeTAD. These results suggest that the reported HTM architectures are promising leads for designing new HTMs for perovskite solar cells owing to their simple and scalable synthesis and tunability.
关键词： Thiazolo[5,4-d]thiazole,Hole transporting materials,Dicyanovinylene,Perovskite solar cell,Donor-Acceptor-Donor
更新于2025-09-16 10:30:52
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Effects of Pyrazine Derivatives and Substituted Positions on the Photoelectric Properties and Electromemory Performance of D–A–D Series Compounds
摘要： Pyrazine derivatives quinoxaline and pyridopyrazine were selected as the acceptors, and benzocarbazole was used as the donor to synthesize four different D–A–D compounds. The results showed that 2,3-bis(decyloxy)pyridine[3,4-b]pyrazine (DPP) exhibited stronger electron-withdrawing ability than that of 2,3-bis(decyloxy)quinoxaline (DPx), because DPP possesses one more nitrogen (N) atom, resulting in a red-shift of the intramolecular charge transfer (ICT) absorption bands and ?uorescent emission spectra for compounds with DPP as the acceptor compared with those that use DPx as the acceptor. The band-gap energy (Eg) of the four D–A–D compounds were 2.82 eV, 2.70 eV, 2.48 eV, and 2.62 eV, respectively, for BPC-2DPx, BPC-3DPx, BPC-2DPP, and BPC-3DPP. The solvatochromic effect was insigni?cant when the four compounds were in the ground state, which became signi?cant in an excited state. With increasing solvent polarity, a 30–43 nm red shift was observed in the emissive spectra of the compounds. The thermal decomposition temperatures of the four compounds between 436 and 453 ?C had very high thermal stability. Resistor-type memory devices based on BPC-2DPx and BPC-2DPP were fabricated in a simple sandwich con?guration, Al/BPC-2DPx/ITO or Al/BPC-2DPP/ITO. The two devices showed a binary non-volatile ?ash memory, with lower threshold voltages and better repeatability.
关键词： quinoxaline,photoelectric properties,donor-acceptor-donor,pyrazine,electromemory,benzocarbazole
更新于2025-09-10 09:29:36
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Highly Stable and Multifunctional Aza-BODIPY-Based Phototherapeutic Agent for Anticancer Treatment
摘要： Phototherapy, as an important class of noninvasive tumor treatment methods, has attracted extensive research interest. Although a large amount of the near-infrared (NIR) phototherapeutic agents have been reported, the low efficiency, complicated structures, tedious synthetic procedures, and poor photostability limit their practical applications. To solve these problems, herein, a donor?acceptor?donor (D?A?D) type organic phototherapeutic agent (B-3) based on NIR aza-boron-dipyrromethene (aza-BODIPY) dye has been constructed, which shows the enhanced photothermal conversion efficiency and high singlet oxygen generation ability by simultaneously utilizing intramolecular photoinduced electron transfer (IPET) mechanism and heavy atom effects. After facile encapsulation of B-3 by amphiphilic DSPE?mPEG5000 and F108, the formed nanoparticles (B-3 NPs) exhibit the excellent photothermal stabilities and reactive oxygen and nitrogen species (RONS) resistance compared with indocyanine green (ICG) proved for theranostic application. Noteworthily, the B-3 NPs can remain outstanding photothermal conversion efficiency (η = 43.0%) as well as continuous singlet oxygen generation ability upon irradiation under a single-wavelength light. Importantly, B-3 NPs can effectively eliminate the tumors with no recurrence via synergistic photothermal/photodynamic therapy under mild condition. The exploration elaborates the photothermal conversion mechanism of small organic compounds and provides a guidance to develop excellent multifunctional NIR phototherapeutic agents for the promising clinical applications.
关键词： heavy atom effects,intramolecular photoinduced electron transfer,donor?acceptor?donor type,NIR phototherapeutic agents,aza-BODIPY
更新于2025-09-10 09:29:36
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Photo-Physical Properties of Thermally Activated Delayed Fluorescent Materials upon Distortion of Central Axis of Donor Moiety
摘要： In this study, we showed the distortion of central axis of donor moiety can switch critically the rate of reverse intersystem crossing (kRISC) process, which is the trigger point to modulate the lifetime of delayed fluorescence. To achieve kRISC what we desired (105 to 106 s-1) in a series of donor-acceptor-donor (D-A-D) type thermally activated delayed fluorescence (TADF) materials, the donor groups (phenoxazine and phenothiazine) was selectively introduced. Maintaining the near orthogonality between donor and acceptor (benzonitrile) moiety, the occurrence of the distortion of central axis of donor moiety could make the effect of locally excited triplet state (3LE). In other words, the interaction between 3LE and the charge transfer counterparts (i.e., 1CT and 3CT) contributes an opposite propensity of kRISC for each target TADF materials when those are dissolved in solution and condensed in solid-state. Herein, we have theoretically and experimentally shown the photo-physical behavior of common D-A-D type TADF upon the different system.
关键词： Reverse Intersystem Crossing,Thermally Activated Delayed Fluorescence,Benzonitrile,Phenoxazine,Donor-Acceptor-Donor,Phenothiazine
更新于2025-09-09 09:28:46
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Importance of Chromophore Rigidity on the Efficiency of Blue Thermally Activated Delayed Fluorescence Emitters
摘要： Four new symmetrical donor?acceptor?donor (D?A?D)-type molecules are reported with diphenylamine (DPA) or 10,11-dihydro-5H-dibenz[b,f ]azepine (Az) as electron donors and 9,9-dimethylthioxanthene-S,S-dioxide (TXO2) as the electron acceptor. The donors are attached at different positions on the acceptor core: either para or meta to the sulfone unit. This series provides new insights into the effects of chromophore rigidity/flexibility on the efficiency of thermally activated delayed fluorescence (TADF). The molecules have been characterized by X-ray crystallography, by in-depth photophysical studies, and by theoretical calculations. The clear differences observed in the photophysical properties when using DPA or Az as a donor are shown to originate from different geometries of the donor unit which, in turn, influence the geometry of the nitrogen lone pair and the donating strength of the corresponding fragment. Thus, a para-substituted Az derivative demonstrated blue TADF in polar media, while the compounds with more flexible DPA units did not show delayed fluorescence. To obtain deep-blue emitters, weaker donating units are needed. A more flexible donor unit leads to increased local excited state (donor) LE emission and reduced TADF. However, a certain amount of flexibility has to be present to ensure deep-blue TADF.
关键词： chromophore rigidity,blue emitters,donor-acceptor-donor,photophysical properties,thermally activated delayed fluorescence
更新于2025-09-04 15:30:14