Benzothiadiazole Units Research Articles

Effects of fluorination of benzothiadiazole units on the properties of alternating cyclopentadithiophene/benzothiadiazole donor/acceptor polymers

AbstractA set of narrow bandgap conjugated polymers was prepared, using cyclopentadithiophene (CDT) donor units coupled with benzothiadiazole (BT) acceptor units substituted with either no fluorine atoms (A1), one fluorine atom (A2) or two fluorine atoms (A3), using the Stille cross coupling reaction. The addition of two electron‐withdrawing fluorine atoms to the BT units was observed to deepen the HOMO energy level of the resulting copolymer, while only slightly affecting the LUMO level, as evidenced by cyclic voltammetry examination. The alternating copolymers (CDT‐A1, CDT‐A2 and CDT‐A3) possess small optical bandgaps of 1.37, 1.43 and 1.51 eV (which should efficiently harvest a broad part of the solar spectrum), and a moderate HOMO level of −5.00, −5.05 and −5.12 eV, respectively. CDT‐A3 displayed the highest optical/electrochemical‐bandgap and the deepest HOMO level, a consequence of the addition of the fluorine atoms on the BT moieties. Inclusion of two fluorine atoms resulted in sharper X‐ray diffraction peaks in the CDT‐A3 copolymer with respect to its analogues CDT‐A1 and CDT‐A2 copolymer indicating a greater crystallinity. These findings clearly demonstrate that fluorination of BT units is an effective approach for adjusting the energy levels and optical properties of BT‐based materials for use in organic solar cells devices as well as for other applications.

Asymmetrified Benzothiadiazole‐Based Solid Additives Enable All‐Polymer Solar Cells with Efficiency Over 19 %

AbstractDisordered polymer chain entanglements within all‐polymer blends limit the formation of optimal donor‐acceptor phase separation. Therefore, developing effective methods to regulate morphology evolution is crucial for achieving optimal morphological features in all‐polymer organic solar cells (APSCs). In this study, two isomers, 4,5‐difluorobenzo‐c‐1,2,5‐thiadiazole (SF‐1) and 5,6‐difluorobenzo‐c‐1,2,5‐thiadiazole (SF‐2), were designed as solid additives based on the widely‐used electron‐deficient benzothiadiazole unit in nonfullerene acceptors. The incorporation of SF‐1 or SF‐2 into PM6 : PY‐DT blend induces stronger molecular packing via molecular interaction, leading to the formation of continuous interpenetrated networks with suitable phase‐separation and vertical distribution. Furthermore, after treatment with SF‐1 and SF‐2, the exciton diffusion lengths for PY‐DT films are extended to over 40 nm, favoring exciton diffusion and charge transport. The asymmetrical SF‐2, characterized by an enhanced dipole moment, increases the power conversion efficiency (PCE) of PM6 : PY‐DT‐based device to 18.83 % due to stronger electrostatic interactions. Moreover, a ternary device strategy boosts the PCE of SF‐2‐treated APSC to over 19 %. This work not only demonstrates one of the best performances of APSCs but also offers an effective approach to manipulate the morphology of all‐polymer blends using rational‐designed solid additives.

Asymmetrified Benzothiadiazole-Based Solid Additives Enable All-Polymer Solar Cells with Efficiency Over 19 .

Disordered polymer chain entanglements within all-polymer blends limit the formation of optimal donor-acceptor phase separation. Therefore, developing effective methods to regulate morphology evolution is crucial for achieving optimal morphological features in all-polymer organic solar cells (APSCs). In this study, two isomers, 4,5-difluorobenzo-c-1,2,5-thiadiazole (SF-1) and 5,6-difluorobenzo-c-1,2,5-thiadiazole (SF-2), were designed as solid additives based on the widely-used electron-deficient benzothiadiazole unit in nonfullerene acceptors. The incorporation of SF-1 or SF-2 into PM6 : PY-DT blend induces stronger molecular packing via molecular interaction, leading to the formation of continuous interpenetrated networks with suitable phase-separation and vertical distribution. Furthermore, after treatment with SF-1 and SF-2, the exciton diffusion lengths for PY-DT films are extended to over 40 nm, favoring exciton diffusion and charge transport. The asymmetrical SF-2, characterized by an enhanced dipole moment, increases the power conversion efficiency (PCE) of PM6 : PY-DT-based device to 18.83 % due to stronger electrostatic interactions. Moreover, a ternary device strategy boosts the PCE of SF-2-treated APSC to over 19 %. This work not only demonstrates one of the best performances of APSCs but also offers an effective approach to manipulate the morphology of all-polymer blends using rational-designed solid additives.

Benzodiazole-Based Covalent Organic Frameworks for Enhanced Photocatalytic Dehalogenation of Phenacyl Bromide Derivatives.

Covalent organic frameworks (COFs) have garnered significant interest within the scientific community due to their distinctive ability to act as organic semiconductors responsive to visible light. This unique attribute makes them up-and-coming candidates for facilitating photocatalytic organic reactions. Herein, two donor-acceptor COFs, TPE-BSD-COF and TPE-BD-COF, have been designed and synthesized by incorporating electron-rich tetraphenylethylene and electron-deficient benzoselenadiazole and benzothiadiazole units into the framework through a Schiff-base polycondensation reaction. Both COFs exhibit exceptional crystallinity and enduring porosity. TPE-BSD-COF and TPE-BD-COF exhibit broad light absorption capabilities, a narrow optical band gap, and low electrochemical impedance spectrum (EIS) levels, indicating that the two COFs are effective heterogeneous photocatalysts for the reductive dehalogenation of phenacyl bromide derivatives under blue LED irradiation. A high photocatalytic yield of 98% and 95% was achieved by TPE-BSD-COF and TPE-BD-COF catalysts, respectively, within only one hour.

Self-Replication Without Hydrogen-Bonds: An Exobiotic Design.

Life on Earth uses DNA as the central template for self-replication, genetic encoding, and information transfer. However, there are no physical laws precluding life's existence elsewhere in space, and alternative life forms may not need DNA. In the search for exobiology, knowing what to look for as a biosignature remains a challenge - especially if it is not from the obvious list of biologic building blocks. Clues from chemicals recently discovered on Mars and in the Taurus Molecular Cloud 1 (TMC-1), show that intriguing organic compounds exist beyond Earth, which could provide a starting point for unconventional exobiotic designs. Here we present a new potential self-replicating system with structural similarities to recently discovered compounds on Mars and TMC-1. Rather than using DNA's hydrogen-bonding motif for reliable base-paring, our design employs sulfur-nitrogen interactions to selectively template unique benzothiadiazole units in sequence. We synthesized and studied two versions of this system, one reversible and the other irreversible, and found experimental evidence of self-replication in d-chloroform solvent. These results are part of a larger pursuit in our lab for developing a basis for a potential exobiological system using starting blocks closely related to these cosmic compounds.

Tunable optoelectronic performances of aminated benzothiadiazole-based D-A-D conjugated electrochromic polymers

Introducing heteroatom groups into benzothiadiazole (BT) unit has proven to be a very effective way to improve the optoelectronic properties of conjugate polymer due to its comprehensive advantages of lowering the HOMO or LUMO energy level, and increasing the interaction force on the polymer backbone. However, at present, little attention was paid to introducing amino groups into the BT unit. Herein, in this work, three D-A-D type aminated monomers (Th–NH2-BT, Th–2NH2-BT, and EDOT-2NH2-BT) with aminated benzothiadiazole as the acceptor unit and thiophene or 3,4-ethylenedioxythiophene (EDOT) as the donor unit were successfully synthesized by Stille coupling reaction, and their corresponding aminated polymers (P(Th–NH2-BT), P(Th–2NH2-BT), and P(EDOT-2NH2-BT)) were facilely achieved by electrochemical polymerization method. The optoelectronic properties of the aminated monomers and their D-A polymers were carefully analyzed, and the electrochemical and electrochromic properties of the resultant aminated polymers were further studied. The finally results show that the absorption and fluorescence spectra of Th–2NH2-BT and EDOT-2NH2-BT are both blue-shifted compared to Th–NH2-BT, and the corresponding optical bandgap are gradually increased (2.41 eV–2.65 eV). EDOT-2NH2-BT has a relatively lower oxidation potential (0.73 V) and P(EDOT-2NH2-BT) also has a wide potential window and better redox stability, which was very beneficial for improving its resultant D-A aminated polymers’ optoelectronic properties. As a result, as-formed P(EDOT-2NH2-BT) shown obvious color change from green in the neutral state to gray in the oxidized state with favorable electrochromic performances, with a high optical contrast (ΔT = 17.17 % at 860 nm) and high coloration efficiency (CE = 223 C−1 cm2 at 860 nm), so it is one of the promising materials that can be used in electrochromic devices.

Mono-chlorinated benzothiadiazole: A new electron-deficient unit for constructing high performance D-A electrochromic polymers

Chlorinated benzothiadiazole (Cl-BT) unit, as a new type of electron-accepting building block with the advantages of easy large-scale synthesis in high yields, has been found to be very promising in designing high performance electroactive polymers with decent optoelectronic properties. Most recently, the Cl-BT unit-based D-A polymers have been applied in many organic electronic devices, but little attention was paid to their electrochromic applications. Herein, in this work, to further evaluate the electrochromic performances of the Cl-BT unit-based chlorinated D-A polymers, two new D-π-A-π-D type chlorinated monomers (Cl-Th and Cl-EDOT) which using mono-chlorinated benzothiadiazole unit as the acceptor unit and thiophene/3,4-ethylenedioxythiophene (EDOT) as the donor unit, was successfully synthesized by Stille coupling reaction and then yield their corresponding chlorinated polymer films (P(Cl-Th) and P(Cl-EDOT)) by electrochemical deposition method. Due to the stronger electron donor ability of EDOT unit, the monomer Cl-EDOT has red-shifted UV–Vis and emission spectra and more significant Stoke's shifts. The lower oxidation potential of Cl-EDOT was very beneficial for improving its resultant D-A chlorinated polymer's optoelectronic properties. As a result, as-formed lower band gap P(Cl-EDOT) (∼1.31 eV) showed reversible color change from the neutral dark green to the oxidized dark blue accompanied with outstanding electrochromic properties, including high optical contrast (24.3%), speedy response time (0.6 s), and high coloration efficiency (170.8 cm2/C), as well as favorable redox stability (70% activity retention after 1000 cycles). The favorable electrochromic performances and good optical stability of P(Cl-EDOT) make it a promising candidate in electrochromic devices. Overall, the chlorinated benzothiadiazole and its derivatives were promising building blocks in constructing high-performance D-A electrochromic polymers.

Single-Chain Conjugated Polymer Guests Confined inside Metal-Organic Frameworks (MOFs): Boosting the Detection and Degradation of a Sulfur Mustard Simulant.

Real-time detection and effective degradation of toxic gases have attracted considerable attention in environmental monitoring and human health. Here, we demonstrate a solvent-assisted dynamic assembly strategy to strongly enhance the detection and degradation performance for 2-chloroethyl ethyl sulfide (CEES, as a sulfur mustard simulant) via confinement of a conjugated polymer in metal-organic frameworks (MOFs). The conjugated polymer poly(9,9-di-n-octylfluorene-altbenzothiadiazole) (F8BT) is infiltrated into one-dimensional nanochannels of the Zr-based topological MOF NU-1000 in a single-chain manner, which is caused by the nanoconfinement effect and the steric hindrance between 9,9-dioctylfluorene units and benzothiadiazole units. The obtained F8BT⊂NU-1000 composites provide a high specific surface area and abundant active sites. Based on the cooperative effect of F8BT and NU-1000, rapid and sensitive detection of CEES has been achieved. Moreover, the F8BT⊂NU-1000 composites can selectively oxidize CEES into 2-chloroethyl ethyl sulfoxide (CEESO) under mild photooxidation conditions. Overall, this study opens a new avenue for the fabrication of conjugated polymer/MOF hybrid materials that show great potential for the sensitive detection and effective removal of hazardous chemicals.

Role of the Benzothiadiazole Unit in Organic Polymers on Photocatalytic Hydrogen Production.

Organic polymers based on the donor-acceptor structure are a promising class of efficient photocatalysts for solar fuel production. Among these polymers, poly(9,9-dioctylfluorene-alt-1,2,3-benzothiadiazole) (PFBT) consisting of fluorene donor and benzothiadiazole acceptor units has shown good photocatalytic activity when it is prepared into polymer dots (Pdots) in water. In this work, we investigate the effect of the chemical environment on the activity of photocatalysis from PFBT Pdots for hydrogen production. This is carried out by comparing the samples with various concentrations of palladium under different pH conditions and with different sacrificial electron donors (SDs). Moreover, a model compound 1,2,3-benzothiadiazole di-9,9-dioctylfluorene (BTDF) is synthesized to investigate the mechanism for protonation of benzothiadiazole and its kinetics in the presence of an organic acid-salicylic acid by cyclic voltammetry. We experimentally show that benzothiadiazole in BTDF can rapidly react with protons with a fitted value of 0.1-5 × 1010 M-1 s-1 which should play a crucial role in the photocatalytic reaction with a polymer photocatalyst containing benzothiadiazole such as PFBT Pdots for hydrogen production in acidic conditions. This work gives insights into why organic polymers with benzothiadiazole work efficiently for photocatalytic hydrogen production.

Access to long-lived room temperature phosphorescence through auration of 2,1,3-benzothiadiazole.

A series of 2,1,3-benzothiadiazole-Au(I)-L complexes have been synthesised, structurally characterised and investigated for their photophysical properties. These are the first organometallic Au(I) complexes containing a C-Au bond on the highly electron-deficient benzothiadiazole unit. The complexes exhibit solution-phase phosphorescence at room temperature, assigned to the intrinsic triplet state of the benzothiadiazole unit that is efficently populated through its attachment to gold. Comparison with routinely reported Au(I) complexes, which include intervening alkenyl linkers, suggests that previous assignments of their phosphorescence as 1π → π*(CCR) might be incomplete. Our observations affirm that, in addition to the heavy atom effect, breaking symmetry in the involved aryl motif may be of importance in controlling the luminescence properties.

Photophysical and redox properties of new donor-acceptor-donor (DAD) compounds containing benzothiadiazole (A) and dimethyldihydroacridine (D) units: a combined experimental and theoretical study.

Four donor-acceptor-donor compounds consisting of 9,9-dimethyl-9,10-dihydroacridine donors differently linked to a benzothiadiazole acceptor were designed using DFT calculations and synthesized, namely 4,7-bis(4-(9,9-dimethyl-9,10-dihydroacridine)phenyl)benzo[c][1,2,5]thiadiazole (1), 4,7-bis(2,5-dimethyl-4-(9,9-dimethyl-9,10-dihydroacridine)phenyl)benzo[c][1,2,5]thiadiazole (2), 4,7-bis(3,5-di(9,9-dimethyl-9,10-dihydroacridine)phenyl)benzo[c][1,2,5]thiadiazole (3), and 4-(3,5-di(9,9-dimethyl-9,10-dihydroacridine)phenyl)-7-(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (4). As predicted theoretically, all studied compounds were electrochemically active both in the reduction as well as in the oxidation modes. They underwent one electron quasi-reversible reduction. Oxidation of 1 and 2 involved a two electron process transforming them into dications and carrying out, in parallel, their dimerization. Oxidation of 3 and 4 resulted in their oligomerization (polymerization). The electrochemically determined ionisation potentials (IP) of 1-4 were similar, covering a narrow range of 5.28-5.33 eV and were consistent with DFT calculations. Larger differences were found for experimentally determined electron affinity (EA) values, being significantly lower for 2 (|EA| = 2.59 eV) as compared to 1, 3 and 4 whose |EA| values were higher by 0.15-0.25 eV, again consistent with DFT calculations. DFT calculations predict positive values of ΔE(S1-T1) for all compounds i.e. in the range of 0.18 eV to 0.43 eV for 1, 3 and 4 and a significantly lower value for 2 (0.06 eV), indicating a possible RISC process in this case. DFT calculations of ΔE(S1-T2) lead to negative and very small values for 2-4 implying a possible involvement of higher lying triplets in the generation of singlet excitons. The investigated derivatives exhibited fluorescence in the orange-red spectral range (550-770 nm) and were strongly dependent on the solvent polarity. The highest PLQY value of 37% was measured for 1 in toluene. The PLQY values significantly improved upon deoxygenation of the studied solutions. Solid state samples also exhibited higher PLQY values as compared to those determined for DCM solutions. These findings were rationalized by partial suppression of the vibrationally induced emission quenching in the solid state due to the intermolecular interaction confinement.

Di-chlorinated benzothiadiazole unit: a new strong electron-withdrawing ability acceptor toward fast-switching green low band gap D-A electrochromic polymers

Di-halogenated benzothiadiazole (BT) is one of the potential acceptor units in constructing low band gap d-A polymers, but it has not attracted widespread attention, especially for the di-chlorinated BT unit. Herein, in this work, two kinds of d-π-A-π-D electrochromic conjugated precursors with di-halogenated BT (5,6-dichlorobenzo[c][1,2,5]thiadiazole and 5‑chloro-6-fluorobenzo[c][1,2,5]thiadiazole) as the acceptor unit, 3-dodecyl thiophene as the π bridge, and 3,4-ethylenedioxythiophene (EDOT) as the donor unit, were designed and synthesized, and their corresponding d-A polymers were successfully obtained by electrochemical deposition method. The photophysical study proves that introducing more chlorine atoms among the precursors will lead to stronger steric hindrance, lower HOMO energy level, blue-shifted absorption spectra, lower quantum yield, but larger Stokes shift. Both of them show very low oxidation potential, which is beneficial for them to obtain high-quality d-A polymers. The introduction of di-chlorinated BT unit obviously improved the polymers’ electroactivity and redox stability, and the remained activity of P(ClCl) was above 74.79 after 1000 cycles. The optical band gap of P(ClCl) is further reduced to 1.28 eV, and the reversible transition from the neutral dark green to the oxidized dark blue can be realized in the redox process. As a result, various favorable electrochromic parameters for P(ClCl) were achieved, such as the optical contrast in the near-infrared region is 27.23 %, the response time is as low as 0.4 s, and the coloration efficiency is as high as 151.3 cm2 C−1, as well as the good optical stability and satisfied memory effect. Overall, the subtle change of halogen atoms in BT units is a very efficient method to modulate the photophysical properties of d-π-A-π-D precursors, also providing good guidelines in designing highly efficient d-A electrochromic polymers.

Dendritic sp Carbon-Conjugated Benzothiadiazole-Based Polymers with Synergistic Multi-Active Groups for High-Performance Lithium Organic Batteries.

Green organic materials composed of C, H, O, and N elements are receiving more and more attention worldwide. However, the high solubility, poor electrical conductivity, and long activation time limit the development of organic materials in practice. Herein, two stable covalent organic materials with alkynyl linkage between benzene rings and benzothiadiazole groups with different amounts of fluorine atoms modification (defined as BOP-0F and BOP-2F), are designed for lithium-ion batteries. Both BOP-0F and BOP-2F can achieve superior reversible capacities of ≈719.8 and 713.5 mAh g-1 over 100 cycles on account of the redox activity of alkynyl (two-electron involved) and benzothiadiazole units (five-electron involved) in these organic materials. While BOP-2F electrodes exhibit much more stable cycling performance than BOP-0F electrodes, especially without pronounced capacity ascending during initial cycling. It can be assigned to the synergy effect of alkynyl linkage and fluorine atom modification in BOP-2F. The lithium storage and activation mechanism of alkynyl, benzothiadiazole, and fluorine groups have also been deeply probed by a series of material characterizations and theoretical simulations. This work could be noteworthy in providing novel tactics for the molecular design and investigation of high-efficiency organic electrodes for energy storage.

Dendritic sp Carbon‐Conjugated Benzothiadiazole‐Based Polymers with Synergistic Multi‐Active Groups for High‐Performance Lithium Organic Batteries

AbstractGreen organic materials composed of C, H, O, and N elements are receiving more and more attention worldwide. However, the high solubility, poor electrical conductivity, and long activation time limit the development of organic materials in practice. Herein, two stable covalent organic materials with alkynyl linkage between benzene rings and benzothiadiazole groups with different amounts of fluorine atoms modification (defined as BOP‐0F and BOP‐2F), are designed for lithium‐ion batteries. Both BOP‐0F and BOP‐2F can achieve superior reversible capacities of ≈719.8 and 713.5 mAh g−1 over 100 cycles on account of the redox activity of alkynyl (two‐electron involved) and benzothiadiazole units (five‐electron involved) in these organic materials. While BOP‐2F electrodes exhibit much more stable cycling performance than BOP‐0F electrodes, especially without pronounced capacity ascending during initial cycling. It can be assigned to the synergy effect of alkynyl linkage and fluorine atom modification in BOP‐2F. The lithium storage and activation mechanism of alkynyl, benzothiadiazole, and fluorine groups have also been deeply probed by a series of material characterizations and theoretical simulations. This work could be noteworthy in providing novel tactics for the molecular design and investigation of high‐efficiency organic electrodes for energy storage.

Novel conjugated microporous polymers for efficient tetracycline adsorption: insights from theoretical investigations

This paper presents a detailed theoretical understanding of the noncovalent interactions between antibiotics tetracycline and conjugated microporous polymer (CMP), which is important to understand the recent experimental finding of efficient removal of antibiotics by CMP materials. We show that the co-work of π-π and H-π interactions determines the final equilibrium structures, when a tetracycline molecule spontaneously adsorbs to the surface or within the pores of the CMP network at physisorption distances. The binding energies for tetracycline/CMP systems are calculated to be −0.31 ∼ −1.15 eV, demonstrating the reliability of the adsorption. The electronic structures of CMP nanostructures remain basically undamaged upon the tetracycline adsorption. The replacement of benzothiadiazole unit with S and N heteroatoms to the phenyl moiety in the linker effectively enhanced the molecular polarity of CMP molecule and increases the interaction area between tetracycline and CMP network, consequently enhancing the average binding energies notably. Our calculations provide useful theoretical guidance for design of novel carbon-based porous adsorbents with good adsorption performance to remove residual tetracycline and other antibiotics in water.

Rationally Engineered Ultrastable Three-Dimensional (3D) Conjugated Microporous Polymers Containing Triptycene, Tetraphenylethene, and Benzothiadiazole Units as Exceptional High-Performance Organic Electrodes for Supercapacitors

Rationally Engineered Ultrastable Three-Dimensional (3D) Conjugated Microporous Polymers Containing Triptycene, Tetraphenylethene, and Benzothiadiazole Units as Exceptional High-Performance Organic Electrodes for Supercapacitors

Highly efficient organic solar cells with improved stability enabled by ternary copolymers with antioxidant side chains

The stability of organic solar cells (OSCs) remains a major concern for their ultimate industrialization due to the photo, oxygen, and water susceptibility of organic photoactive materials. Usually, antioxidant additives are blended as radical scavengers into the active layer. However, it will induce the intrinsic morphology instability and adversely affect the efficiency and long-term stability. Herein, the antioxidant dibutylhydroxytoluene (BHT) group has been covalently linked onto the side chain of benzothiadiazole (BT) unit, and a series of ternary copolymers D18-Cl-BTBHTx (x = 0, 0.05, 0.1, 0.2) with varied ratio of BHT-containing side chains have been synthesized. It was found that the introduction of BHT side chains would have a negligible effect on the photophysical properties and electronic levels, and the D18-Cl-BTBHT0.05: Y6-based OSC achieved the highest power conversion efficiency (PCE) of 17.6%, which is higher than those based active layer blended with BHT additives. More importantly, the unencapsulated device based on D18-Cl-BTBHTx (x = 0.05, 0.1, 0.2) retained approximately 50% of the initial PCE over 30 hours operation under ambient conditions, significantly outperforming the control device based on D18-Cl (90% degradation in PCE after 30 h). This work provides a new structural design strategy of copolymers for OSCs with simultaneously improved efficiency and stability.

Benzothiadiazole-based rotation and possible antipolar order in carboxylate-based metal-organic frameworks

By modifying organic ligands of metal-organic framework with dipolar units, they turn suitable for various applications, e.g., in the field of sensor systems or switching of gas permeation. Dipolar linkers in the organic ligand are capable to rotate in certain temperature and frequency ranges. The copper-bearing paddlewheel shaped metal-organic frameworks ZJNU-40 and JLU-Liu30 possess such a polarizable dipole moment due to their benzothiadiazole moiety in the organic ligands. Here, we investigate the molecular rotor behavior of benzothiadiazole units of the two carboxylate-based MOFs by dielectric spectroscopy and computational simulation. Our dielectric results provide clear evidence for significant reorientational relaxation dynamics of these rotors, revealing various characteristics of glasslike freezing upon cooling. The calculated rotational energy barriers are consistent with experimentally determined barriers for single-dipole dynamics. Moreover, for JLU-Liu30 we find hints at antipolar ordering below about 300 K.

Cross-conjugated polymers as fluorescent probes for intracellular potassium ion detection

The abnormal changes of intracellular potassium ion (K+) concentration are usually associated with various diseases, therefore, real-time monitoring of intracellular K+ dynamic balance is crucial for disease research. Herein, we present a design strategy based on conjugated polymers (CPs) as potassium ion fluorescence probes. Six novel CP-based K+ sensors (P1, P2, P3, PP1, PP2 and PP3) were synthesized. These probes have different conjugated length backbones composing of stilbenzene, fluorene, thiophene, and/or benzothiadiazole units and different numbers of K+ selective ligands of triazacryptand (TAC), so as to study their spectral characteristics and response to K+. Among them, PP3 exhibits exceptional responsiveness and selectivity to K+. With a longer conjugated backbone, it shows a longer emission at 628 nm compared to other probes. Especially, the fluorescence intensities of PP3 showed a linear relationship with the concentrations of K+ in the range of 0–250 mM. PP3 has been successfully applied to detect the dynamic equilibrium of potassium ion concentration in living cells. This study proposes and validates the feasibility of the CP-based K+ fluorescence probe design strategy and expands the range of K+ probes, providing a new tool for understanding disease pathogenesis.

Molecular engineering of auxiliary acceptor for the development of efficient organic D-A-π-A sensitizers

Molecular structure is vitally important for the selective optimization of energy level and improving the interfacial charge transfer performance of dye-sensitized solar cells (DSSCs). With appropriate auxiliary acceptor, the organic sensitizer owing D-A-π-A structure can act as a promising efficient sensitizer for DSSCs. Herein, considering the conjugated π-system and electron-withdrawing capability, dyes CS-71 and CS-72 were designed and synthesized with naphthothiadiazole and naphthobisthiadiazole units as the auxiliary acceptors, respectively, while the benzothiadiazole unit was applied as the auxiliary acceptor for the reference dye CS-70. The structure-activity relationship between the molecular structure characteristics, including steric hindrance, π-conjugation system, and electron-withdrawing capability of the auxiliary acceptors, and the properties of the dye are systematically investigated. Ascribed to the extended auxiliary acceptor moieties, CS-71 and CS-72 obtained obvious downward shift LUMO levels accompanying with the HOMO levels remaining unchanged, with respect to the reference dye CS-70. Owing to the shrinked energy gap, their absorption spectra were also significantly bathochromic shifted, resulting in the effectively broadened light-harvesting region. Combining the improved charge injection process, cell devices sensitized by CS-72 achieves an optimal PCE of 7.17%, presenting us a promising way to obtain highly efficient organic sensitizer in the future.