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Concerted companion dyes (CC dyes) like XW61 have been demonstrated to be an effective platform for developing efficient DSSCs. However, the moderated phenothiazine-based electron donor in XW61 results in unsatisfactory Jsc. To address this problem, a stronger fluorenyl indoline-based electron donor has been used to construct porphyrin dye XW68 and organic dyes Y1-Y2. The stronger electron-donating character of the fluorenyl indoline unit leads to an enhanced Jsc value (20.48 mA·cm-2) for the individual dye XW68. On this basis, CC dyes XW69-XW70-C8 have been designed and synthesized by combining the frameworks of Y1 and Y2 with XW68. The complementary absorption characters of the porphyrin and the organic dye moieties lead to panchromatic absorption with a strong light-harvesting capability from 350 to 700 nm and the onset wavelength extended to ca. 840 nm in the IPCE curves. As a result, excellent Jsc values have been achieved (>22 mA·cm-2). In addition to the advantages of high Jsc, bulky octyl groups have been introduced into the donor of XW70-C8 to reduce dye aggregation and suppress charge recombination. Finally, a highest PCE of 11.1% with a satisfactory Jsc (22.25 mA·cm-2) and an enhanced Voc (750 mV) has been achieved upon coadsorption of XW70-C8 with CDCA. In addition, the CC dye XW70-C8-based solar cells exhibit excellent long-term photostability. These results provide an effective method for rationally improving the photovoltaic behavior, especially the Jsc of CC dyes, by introducing strong electron donor moieties with suitable substituents.

Tetracenequinone fused porphyrin Ni4TQ has been synthesized and the long tetracenequinone units at the vertices of porphyrin exhibit an intense π,π-interaction, which can be regulated by solvents to furnish different shapes of crystals or various uniform flower-shaped biomorphs.

To fabricate efficient dye-sensitized solar cells (DSSCs), 4-tert-butylpyridine (TBP) is commonly used as an additive in the electrolytes for improving the photovoltages (VOC). However, TBP cannot play a positive role in improving the photocurrent (JSC) because of the lack of absorption in the visible-wavelength range. We herein report a light-absorbing pyridine derivative N1 as an additive for the axial coordination with porphyrin dyes. N1 was synthesized by introducing a (bis(4-methoxyphenyl)amino)anthryl moiety into the para-position of pyridine via an acetylene bridge, and porphyrin dye XW64 containing meso-3,5-disubstituted phenyl groups was synthesized considering that the meta-substituted phenyl groups may induce weaker steric hindrance with the axial pyridyl ligand, as compared with wrapped and strapped porphyrin dyes. Thus, N1 was used as an electrolyte additive together with TBP. When optimized concentrations of 6 mM N1 and 0.5 M TBP were used for fabricating DSSCs based on XW64, enhanced photovoltaic performance was achieved, with JSC, VOC, and efficiency of 15.65 mA·cm-2, 0.701 V, and 7.35%, respectively, superior to those of the corresponding DSSCs without using the additives (JSC = 14.86 mA·cm-2, VOC = 0.599 V, and efficiency = 5.94%). The enhancement of JSC can be ascribed to the improved light-harvesting ability induced by the axially coordinated N1. Furthermore, the two additives also can be used to fabricate efficient solar cells based on the wrapped porphyrin dye XW42, achieving high efficiency of 10.3%, indicative of their general applicability in fabricating high-performance DSSCs. These results indicate that the simultaneous employment of the traditional TBP additive and a pyridyl ligand with light-harvesting ability in the electrolyte for the axial coordination to a porphyrin dye is a promising approach for developing efficient DSSCs.

An N-confused hexapyrrolic phlorinoid 1 and its isomer N-fused hexapyrrolic phlorinoid 2 were synthesized through [4 + 2] condensation. Both 1 and 2 can be readily transformed into N-confused hexapyrrolic phlorinone 3 under aerobic conditions. Coordination of 1 with Cu(acac)2 afforded two different mono-Cu(II) complexes 4 and 5 with CNNN and ONNN coordination environments, respectively. The NIR absorption bands can be effectively modulated up to 1265 nm through the oxidation, fusion, and metalation reactions.

To achieve high power conversion efficiency (PCE), three porphyrin sensitizers have been synthesized and explored to simultaneously enhance the photocurrent (Jsc) and photovoltage (Voc). On basis of the XW4, a benzothiadiazole (BTD) unit has been introduced to afford XW57 with the aim to extend the absorption wavelength and enhance the light harvesting ability. As a result, a Jsc of 13.72 mA/cm2 has been obtained for XW57, higher than that of XW4. On this basis, XW58 has been prepared by modifying the carbazole-based donor with two bulky dihexyloxyphenyl groups, and the superior anti-aggregation character raises the Voc from 781 mV (XW4) to 844 mV. When both the BTD unit and the bulky groups are introduced to the acceptor and donor units, respectively, the resulting sensitizer XW59 exhibits a highest PCE value of 7.34% with synergistically enhanced Jsc of 13.19 mA/cm2 and Voc of 793 mV. These results provide further insight into developing high performance dye-sensitized solar cells

Porphyrin dyes have been widely used for the fabrication of efficient dye-sensitized solar cells (DSSCs). However, dye aggregation and charge recombination still exert negative effects on photovoltaic performance, resulting in unsatisfactory power conversion efficiencies (PCEs). Herein, we report a new class of porphyrin sensitizers, XW52 and XW53 employing four benzyloxy groups to wrap the porphyrin cores. As a result, an efficiency of 7.6% was obtained for XW52, with [Formula: see text] and [Formula: see text] of 668 mV and 16.63 mA cm[Formula: see text], respectively. Compared with XW52, an additional 2,6-dialkoxyphenyl group has been introduced to the N-atom of the phenothiazine donor to furnish XW53 with the aim to further improve the anti-aggregation character and the solubility, and thus the [Formula: see text] was improved to 674 mV, and a higher efficiency of 7.9% was achieved for XW53. Upon cosensitization with PT-C6, the[Formula: see text] and [Formula: see text] were synergistically enhanced to 727 mV and 18.67 mA cm[Formula: see text], respectively. As a result, a high efficiency of 9.6% was successfully achieved for the cosensitization system of XW53 + PT-C6. These results provide an effective novel strategy for designing efficient porphyrin dyes by introducing multiple benzyloxy groups to the meso-phenyl groups.

Three new porphyrin dyes XW45 − XW47 have been synthesized employing a dialkoxy-wrapped phenothiazine donor, a tetraalkoxy-wrapped porphyrin π-framework, a benzothiadiazole (BTD)-based auxiliary acceptor, and an anchoring benzoic acid group. On the basis of our previously reported dye XW36 , XW45 was synthesized by introducing a BTD unit to broaden the absorption spectrum, further introducing a hexyl-substituent into the BTD unit afforded XW46 , and an additional fluorine atom was introduced to the carboxyphenyl acceptor to afford XW47 . As expected, the BTD unit obviously broadens and red-shifts the absorption threshold of XW45 − XW47 to ca . 750 nm. Dye-sensitized solar cells (DSSCs) were fabricated based on a cobalt electrolyte using chenodeoxycholic acid (CDCA) as the coadsorbent. Under full sun illumination, XW45 exhibits an efficiency of 9.73%, which is slightly lower than that of 10.19% obtained for the reference dye SM315 . By contrast, XW46 and XW47 show higher efficiencies than SM315 owing to the improved anti-aggregation ability associated with the hexyl group on the BTD unit and better ICT effect induced by the fluorine atom on the carboxyphenyl unit. Thus, XW47 exhibits the highest efficiency of 10.41% among the porphyrin dyes. Furthermore, PT-C6 was used as the cosensitizer to improve the light harvesting ability and efficiencies of the cells due to its broad absorption within 350–560 nm. Thus, high efficiencies of 10.32%, 11.38% and 10.90% were achieved for the cosensitized solar cells based on XW45 – XW47 , respectively, owing to the obviously enhanced photocurrent density ( J SC). In addition, under 30% full sun illumination, XW46 + PT-C6 exhibits a high efficiency of 13.08%. These results give an effective method for building high performance DSSCs through the cosensitization of porphyrin dyes containing a wrapped donor, a wrapped porphyrin framework and a properly substituted auxiliary benzothiadiazole unit.

Four novel porphyrin dyes XW48–XW51 with a doubly strapped porphyrin framework and judicious optimization of the substituents of the phenothiazine donor have been synthesized and utilized as DSSC dyes. On the basis of XW40, bulky 2,6-bis(hexyloxy)phenyl groups were incorporated into the phenothiazine donor by replacing the hexyl, 4-hexyloxyphenyl and both of them, to afford XW48, XW49 and XW50, respectively. On the basis of XW50, XW51 was synthesized by using 2,4-bis(hexyloxy)phenyl in place of the 2,6-bis(hexyloxy)phenyl units. As a result, the Voc values were enhanced stepwisely from 730 mV (XW40) to ca. 750 mV (XW48/XW49) and then to 761 mV (XW50). Compared with XW50, XW51 contains a bulky donor with more evenly distributed alkoxyl chains, which tend to form a more compact self-assembled monolayer to impede the penetration of I3−. Hence, an extraordinarily high Voc of 781 mV was achieved for XW51. As a result, the efficiency was dramatically improved to 11.1%, which is the highest efficiency for DSSCs based on an individual sensitizer using the iodine electrolyte, to the best of our knowledge. Furthermore, high efficiencies of 10.1% and 9.7% were also obtained for XW50 and XW51, respectively, based on the cobalt electrolyte.

Porphyrin sensitizers play essential roles in the development of efficient dye-sensitized solar cells (DSSCs). To further improve power conversion efficiency (PCE), it is vital to reduce undesirable dye aggregation that causes serious charge recombination and lowered open-circuit voltages (Voc). To this end, we herein report a new class of porphyrin-based dyes XW40 and XW41, with the porphyrin cores strapped with two circle chains. Compared with the reference sensitizer XW10 which contains a porphyrin core wrapped in four dodecoxyl chains, the double strapping in XW40 not only effectively suppresses the dye aggregation but also improves the dye loading amount. As a result, the Voc and photocurrent (Jsc) were improved by 19 mV and 0.8 mA cm−2, respectively, compared with the corresponding values of XW10, and the efficiency was improved from 8.6% obtained for XW10 to 9.3% for XW40. To further extend the spectral response, an electron-withdrawing benzothiadiazole (BTD) unit was introduced as an auxiliary acceptor in XW41. Impressively, the onset wavelength of its IPCE spectrum was dramatically red-shifted to 830 nm. However, the extended π-conjugation framework results in aggravated dye aggregation, and thus a lowered efficiency of 8.2% was obtained for XW41. Through a combined approach of coadsorption and cosensitization, the efficiencies were dramatically enhanced to 10.6% and 10.2% for XW40 and XW41, respectively, as a result of simultaneously enhanced Voc and Jsc. The results of this work provide a novel strategy for developing efficient DSSCs by employing strapped porphyrin dyes.

Dye-sensitized solar cells (DSSCs) have attracted intensive attention in developing photovoltaic devices for employing solar energy. For developing panchromatic and efficient porphyrin sensitizers, it has been demonstrated to be an effective approach to introduce an electron-withdrawing benzothiadiazole unit as an extra electron acceptor. In contrast, the structurally similar benzotriazole moiety remains relatively unknown in this respect. In this work, we have synthesized a novel porphyrin dye containing an extra electron acceptor of benzotriazole. Photophysical and electrochemical investigations revealed red-shifted absorption and a narrower band gap induced by the benzotriazole unit. Thus, a reasonable efficiency of 8.39% has been achieved with a Jsc of 17.00 mA cm−2 and a Voc of 712 mV. On this basis, to investigate the effect of the dihedral angle between the benzotriazole and the adjacent phenylene ring, one or two methyl groups were attached to the ortho-positions of the phenylene ring. As a result, the enlarged torsion angles induce poor electronic coupling between the LUMO of the dyes and TiO2, resulting in lower efficiencies of 6.61% and 3.62%, respectively. With the purpose to further improve the efficiencies, coadsorption and cosensitization approaches were employed. And the efficiencies have been successfully elevated to 9.32%, 8.49% and 7.34%, respectively. These results demonstrate the effectiveness of incorporating an auxiliary benzotriazole acceptor into porphyrin dyes on achieving extended light-harvesting wavelength ranges and illustrate the importance of avoiding severe torsion within the acceptor part of the porphyrin dyes. In contrast to the commonly used cosensitizers with absorption peaks lying in the absorption valley between the Soret band and the Q bands of porphyrin dyes (500–600 nm), the utilization of an organic dye with broad absorption in this work has been demonstrated to be effective for improving the efficiencies despite the fact that its absorption peak at 450 nm largely overlaps with the Soret band of the porphyrin dyes. These results provide an alternative approach for developing cosensitizers for porphyrin dyes.

Biothiols such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) play vital roles in various physiological and pathological processes. In this work, a BODIPY-based fluorescent probe XCN was synthesized from multi-step reactions. We first synthesized a BODIPY derivative with a cyano and a bromine moiety attached to the 8-diphenylaminophenyl substituent of BODIPY, followed by the reaction with p-aminothiophenol under basic condition. Interestingly, compound XCN was successfully obtained with the p-aminophenylthio moiety introduced into one of the α-positions of the pyrrolic units. This reaction may compose an efficient approach for synthesizing novel BODIPY derivatives with substituents attached to the pyrrolic unit without previously brominating it. XCN can be used as a fluorescence turn-on probe to selectively detect Cys and Hcy using the cyano group as the recognition site, with the p-aminophenylthio moiety left unreacted. XCN was found to be nearly nonfluorescent, and it exhibits only slight fluorescence enhancement when treated with GSH. However, upon interaction with Cys or Hcy, the fluorescence was enhanced by 1081 and 1126 folds, respectively. In addition, XCN exhibits good selectivity and sensitivity towards Cys and Hcy over GSH and other amino acids in a wide pH range from 2 to 10 in aqueous buffers. Furthermore, XCN was successfully used for imaging biothiols in living A549 lung cancer cells.

Biothiols, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play essential roles in many physiological and pathological processes. In this work, three porphyrin derivatives, XQ1 , XQ2 and XQ3 , were synthesized by combining the porphyrin framework with nitroethylene, bis(methoxycarbonyl)ethylene and dicyanoethylene moieties, respectively. XQ1 was almost nonfluorescent, which could be utilized as a good starting point for developing fluorescence turn-on probes. Thus, XQ1 exhibits fast fluorescence enhancement and high selectivity towards the biothiols based on the Michael addition mechanism. It also exhibits high sensitivity towards the biothiols with the detection limits of 0.65–1.1 μM. In addition, XQ1 was successfully applied to cell imaging in living A549 cells for visualizing the biothiols. The results compose a good example of designing porphyrin derivatives for detecting biothiols, with the advantages of dramatic fluorescence enhancement in the NIR wavelength range, which exhibits good cell membrane permeability and practicability in detecting both exogenous and endogenous biothiols.

Two fluorescence “turn-on” Zn2+ probes were developed by introducing an anthracenyl fluorophore through the linkage of a diphenylamino moiety at the 5-position of a dipyrrin moiety. Thus, two compounds with weak fluorescence were designed, synthesized, and employed as CHEF (chelation enhanced fluorescence) type fluorescence “turn-on” Zn2+ probes, which exhibit dramatic fluorescence enhancement upon addition of Zn2+, showing high sensitivities and impressive detection limits of 13 and 12 nM, respectively, better than their analogues containing simple aryl substituents at the 5 positions of a di- or tripyrrin moiety. In addition, both of the probes exhibit good selectivity, short response time of less than 10 s and wide applicable pH ranges. Furthermore, the weak fluorescence nature of the probes was rationalized based on viscosity dependence measurements and theoretical calculations. These results provide further insight into the development of selective and sensitive zinc probes.

The selective and sensitive detection of zinc ions has been an important research topic because of the vital role played by zinc ions in numerous physiological activities, and fluorescent probes have emerged as effective and powerful tools for zinc detection because of their simplicity andcereal-time monitoring nature. In this work, with the purpose to improve the binding affinities and sensitivities of dipyrrin based fluorescent Zn 2+ probes, strongly coordinating pyridyl moieties were introduced into dipyrrins. Aroylation of 5-pentafluorophenyl and 5-unsubstituted dipyrromethanes with picolinoyl chloride afforded two corresponding dipicolinoyl dipyrromethanes, which were further oxidized with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to afford the expected 5-pentafluorophenyl-substituted dipicolinoyl dipyrrin and a unique unexpected dipicolinoyl dipyrrolyl ketone, respectively. Both of these compounds exhibited noticeable fluorescence “turn-on” responses specifically to Zn 2+ over other metal cations, with fluorescence enhancements of 87 fold and 119 fold, respectively. However, because of the different substituents at the 5 positions and the different conjugation frameworks, distinct Zn 2+ sensing behavior was observed. For the 5-pentafluorophenyl-substituted dipicolinoyl dipyrrin, the sensing of Zn 2+ induced a color change from light orange to pink accompanied with enhanced red fluorescence. Whereas, the sensing of Zn 2+ by the dipicolinoyl dipyrrolyl ketone induced the color change from nearly colorless to bright yellow and enhanced green fluorescence. Based on high binding affinities and the dramatic spectral responses, both of the probes exhibit high sensitivities towards Zn 2+ with detection limits of 9.8 nM and 6.3 nM, respectively. In addition, fast responses within 10 s and wide applicable pH ranges are indicative of their potential applications as promising zinc probes. Finally, the 5-pentafluorophenyl dipicolinoyl dipyrrin was successfully applied to cell imaging in Hela cells, demonstrating its practical applicability. It is noteworthy that the single crystal structure of a Zn 2+ complex of the dipicolinoyl dipyrrolyl ketone was successfully analyzed by X-ray diffraction, which revealed an interesting tetranuclear Zn 2+ coordination structure. These results provide further insights into the design of highly sensitive Zn 2+ probes by introducing pyridyl moieties into dipyrrin platforms.

With the purpose to develop efficient dye-sensitized solar cells (DSSCs), a series of push-pull porphyrin dyes have been designed and optimized by introducing additional electron-donating diphenylamino and electron-withdrawing benzothiadiazole moieties. Electrochemical, photophysical and photovoltaic investigations indicate that the introduction of additional donors and acceptors can effectively extend the absorption spectra, resulting in better sunlight harvesting. However, the HOMO levels of the dyes are elevated by the additional donors, resulting in decreased driving forces for dye regeneration and decreased cell efficiencies. Upon coadsorption with 5 mM chenodeoxycholic acid (CDCA), the cell efficiencies can be elevated from 1.37% - 5.01% to 1.70% - 6.97%. Furthermore, based on the subtle absorption characteristics of the porphyrin dyes, we delicately designed a cocktail co-sensitization strategy using the solutions containing two of the porphyrin dyes as well as CDCA. Finally, a high photovoltaic efficiency of 8.6% was successfully achieved at an optimized molar ratio of 10:1 for the two porphyrin dyes.

Four alkoxy-wrapped push-pull porphyrin dyes containing the phenothiazine derived donor and the ethynylbenzoic acid acceptor have been designed, synthesized and used as sensitizers for fabricating ...

By the acid-catalyzed [2 + 2] condensation, an unprecedented neo-N-confused phlorin (neo-NCphlorin 1) was successfully synthesized. By treating 1 with N-chlorosuccinimide, the corresponding chloro-substituted neo-NCphlorin (1-Cl) was obtained. The oxidization of 1 with FeCl3 afforded the neo-N-confused phlorinone (neo-NCphlorinone 2), which bears a relatively coplanar conformation, different from the highly distorted ones observed for 1 and 1-Cl. Notably, 2 shows striking long-wavelength absorption beyond 1300 nm upon addition of TBAF.

From the simple one-pot Vilsmeier formylation of 9-diphenylaminoanthracence, mono-, di- and tri-formyl products were successfully synthesized and the yields for the individual products can be optimized by varying the equivalents of the Vilsmeier reagent and changing the reaction temperature. The four obtained aldehydes exhibit distinct optical properties, with the emission maxima varying in a large wavelength range of 455–593 nm, despite their similar structures. The intramolecular charge transfer effect can be effectively modulated by varying the numbers and positions of the formyl groups, resulting in the observed distinct optical properties. Based on the aldehydes, the corresponding boron-dipyrromethenes were also synthesized. Similarly, the intramolecular charge transfer effect and the optical properties can be effectively modulated by the numbers and positions of the boron-dipyrromethene moieties. To further modulate the intramolecular charge transfer effect and red shift the emission, the dimethoxy-substituted 9-diphenylaminoanthracence was also used for synthesizing the corresponding aldehyde and boron-dipyrromethene. Thus, full color emissions within the wavelength range of 455–704 nm were successfully achieved based on modulating the intramolecular charge transfer.

A combination of aggregation-induced emission and intramolecular charge transfer was achieved by using a triphenylamine analogue and a dicyanovinyl moiety as the electron donating and accepting uni ...

Efficient and selective ArS substitution of BODPY by various thiophenols was developed, in which the BODIPYs catalyze the formation of the ArS radicals under light and trap them in situ to form C-S bonds. Interestingly, the fluorescence properties of the ArS-substituted BODIPYs are effectively modulated by the numbers and electronic effects of the ArS units, with quantum yields varying in a range of 0.001-0.87.

Photocurrent (Jsc) and photovoltage (Voc) are two important parameters for dye-sensitized solar cells (DSSCs) to achieve high power conversion efficiencies (PCEs). Herein, we synthesize four novel ...

To fabricate efficient dye-sensitized solar cells (DSSCs), three porphyrin dyes XW65−XW67 have been designed and synthesized using a bulky triphenylamine donor. Based on our previously reported dyes with a carbazole donor, a bulky triphenylamine unit was employed as the donor to synthesize XW65 with the aim to enhance the electron donating ability and suppress dye aggregation. As a result, XW65 shows enhanced photocurrent density (Jsc) and open circuit voltage (Voc), affording a high efficiency of 9.02%. On this basis, XW66 was synthesized with a methyl group introduced into the carboxyphenyl acceptor to further suppress dye aggregation and improve the Voc, achieving an enhanced efficiency of 9.23% with improved Voc of 849 mV and Jsc of 14.87 mA cm−2, which can be ascribed to the further suppressed dye aggregation and enhanced adsorption amount on the TiO2 film induced by the additional methyl group. To further improve the Jsc, a benzothiadiazole (BTD) unit has been introduced as the auxiliary acceptor to afford XW67, which exhibits a strikingly red-shifted monochromatic photon-to-electron conversion efficiency (IPCE) onset wavelength of 830 nm, obtaining the highest Jsc value of 15.83 mA cm−2 among the three dyes. Consequently, despite the sacrifice of Voc caused by the severe dye aggregation associated the extended conjugation framework, XW67 exhibits the highest efficiency of 9.43%. On this basis, cosensitization with WS-5 afforded elevated efficiencies of 10.07%, 10.38% and 10.13% for XW65−XW67, respectively, owing to the simultaneously enhanced Jsc and Voc. These results indicate that it is effective to develop efficient DSSCs based on cosensitization of optimized porphyrin dyes containing a bulky triphenylamine donor, a methyl group on the carboxyphenyl acceptor, and an auxiliary electron acceptor.

Summary The improvement of open-circuit voltage (VOC) is a crucial goal to develop efficient dye-sensitized solar cells (DSSCs). Here, conjugating pillar[5]arene dyes (PPI and PPII) are designed, synthesized, and applied in DSSCs. The presence of pillar[5]arene moiety in the dyes inhibits the dye aggregation and charge recombination in the DSSCs, leading to the enhancement of VOC. PPI with a single D-π-A backbone and a pillar[5]arene moiety achieves a VOC of 715 mV, which is much higher than the reference dye (VOC of 674 mV) with the same D-π-A backbone but no pillar[5]arene moiety. PPII with 2 D-π-A backbones also achieves a VOC of 746 mV and a much higher short-circuit photocurrent (JSC) than the reference dyes. In addition, the host-guest interaction can adjust the VOC and JSC by coupling dye with the imidazolium in electrolyte, as confirmed by the electrolyte engineering.

In dye-sensitized solar cells (DSSCs), the HOMO–LUMO energy gap of organic sensitizers should be large enough to enable efficient electron injection and dye regeneration. However, the LUMOs of most practical organic dyes are always too high, making energy “waste”. In order to deepen the LUMOs, we focus on the targeted modulation of the molecular energy levels by embedding an electron donor or acceptor into the skeleton of a typical D–π–A model. The electron-rich group of 3,4-ethylenedioxythiophene (EDOT) lifts up the HOMO level with little influence on the LUMO, while the electron-deficient group of benzothiadiazole (BTD) or benzooxadiazole (BOD) mainly lowers the customized LUMO level. As a consequence, the auxiliary group change from EDOT (dye WS-53) to BOD (dye WS-55) brings forth a huge photoelectric conversion efficiency (PCE) increase by 38 fold from 0.24 to 9.46% based on an I−/I3− redox couple, and even reaching a high PCE of 10.14% with WS-55 under 0.3 sunlight irradiation.

Three porphyrin sensitizers XW54–XW56 containing a carbazole donor have been designed and synthesized by introducing a benzothiadiazole (BTD) unit as the auxiliary electron acceptor to extend the absorption spectra and/or bulky dihexyloxyphenyl groups into the carbazole unit to suppress dye aggregation and improve the photovoltage (Voc). The BTD unit incorporated in XW54 obviously broadens and red-shifts the absorption threshold to ca. 700 nm, as compared with that of 650 nm observed for XW1. Thus, XW54 exhibits a much broader monochromatic photon-to-electron conversion efficiency (IPCE) spectrum with an extremely red-shifted onset wavelength of 780 nm, resulting in a photocurrent density (Jsc) of 11.60 mA cm−2, higher than that of XW1. Unfortunately, the Voc value was decreased owing to the more severe dye aggregation caused by the large conjugation framework induced by the presence of the BTD unit. As a result, XW54 shows an efficiency of 6.26%, slightly higher than that of 6.11% obtained for XW1. On the other hand, with the bulky dihexyloxyphenyl donor groups introduced to XW55, a highest Voc of 860 mV was achieved, which can be ascribed to the efficient prevention of charge recombination and suppression of dye aggregation. Thus, XW55-based cells exhibit an improved efficiency of 6.60%. On the basis of XW54 and XW55, two bulky dihexyloxyphenyl groups and a BTD unit were simultaneously introduced to XW56, affording a highest efficiency of 7.03%, with the Jsc and Voc values of 12.5 mA cm−2 and 785 mV, respectively. These results compose a novel approach for developing efficient dye-sensitized solar cells (DSSCs) by simultaneously introducing bulky dihexyloxyphenyl groups and a benzothiadiazole unit, which may synergistically broaden the absorption spectra and suppress the dye aggregation, resulting in improved photocurrent and photovoltage.

Porphyrin dyes have received great attention due to their excellent photovoltaic performance in dye-sensitized solar cells (DSSCs). In this work, dyes XC1 – XC3 were synthesized by introducing various numbers of bis(4-methoxyphenyl)amino and p -hexyloxyphenyl groups to porphyrin meso -positions. The XC1 molecule contains two p -hexyloxyphenyl groups, and its DSSCs showed the power conversion efficiency of 4.81%. For XC2 and XC3 , the replacement of p -hexyloxyphenyl with diphenylamino groups can effectively enhance the light harvesting around 500 nm. However, the highest occupied molecular orbitals (HOMOs) were elevated too much, which suppressed the dye regeneration processes, leading to low cell efficiencies of 2.51% and 1.27% for XC2 , and XC3 , respectively. To further improve the cell performance, an anthracene derivative C1 was used as the cosensitizer for XC1 , which increased both the J sc and V oc values, with an improved efficiency of 5.75%.

Novel tin(IV) halo complexes of an N-confused tetraphenylporphyrin with different axial ligands have been synthesized and characterized by various spectroscopic methods including X-ray crystallographic analysis. The molecular structures of the dichloro and dibromo derivatives possess perfect octahedral geometries, which are nearly comparable to the corresponding regular porphyrin complexes. In contrast, the iodide/triiodide complex obtained by a same reaction manner, demonstrated that the tin(IV) cation is slightly displaced towards axially coordinated iodide anion, giving rise to the different electronic structure due to the tautomeric form of N-confused porphyrin ligand. These structural differences reflected to the distinct photophysical and electrochemical properties. The Sn(IV) complexes are near IR luminescent, however the unsymmetrical axial coordination of iodide and triiodide anions in the tin(IV) N-confused porphyrin complex allows, in particular, the longer emission lifetimes and a smaller singlet-triplet energy gap, which were investigated by steady-state and time-resolved spectroscopies as well as theoretical calculations.

Compared with the development of novel organic sensitizers, cosensitization is a much more convenient way to acquire panchromatic dye-sensitized solar cells (DSSCs). Taking the strong absorption in the long wavelength region but the lack of response in the ranges of 350–410 nm and 500–600 nm of porphyrin dyes into account, the D–A–π–A benzotriazole organic dye (WS-5), showing strong absorption bands in these two ranges, is targeted for cosensitization with porphyrin dye XW4. The cosensitization effects on light-harvesting capability, photovoltaic performance, charge recombination as well as long-term stability have been investigated in detail, especially for the interactions between WS-5 and XW4 and their effects on photovoltaic performance. Noticeably, a strong panchromatic light response and a promising photovoltaic efficiency of 10.41% have been achieved with only 6 μm TiO2 films, which is obviously higher than the corresponding efficiencies obtained using a single sensitizer. The cosensitization is essentially dominated by WS-5 while only a small amount of XW4 is contributed to enhance the IPCE response in the long wavelength region. These results demonstrate the effective approach for utilizing porphyrin dyes to simultaneously fill up the absorption valleys of D–A–π–A featured sensitizers and promote the DSSC efficiency, presenting the effective strategy of cosensitization to combine the advantages of both porphyrin and organic dyes, especially for pursuing highly efficient panchromatic dye-sensitized solar cells.

Donor-π-acceptor-type porphyrin dyes have been widely used for the fabrication of efficient dye-sensitized solar cells (DSSCs) owing to their strong absorption in the visible region and the ease of modifying their chemical structures and photovoltaic behavior. On the basis of our previously reported efficient porphyrin dye XW11, which contains a phenothiazine-based electron donor, a π-extending ethynylene unit, and an auxiliary benzothiadiazole acceptor, we herein report the syntheses of novel porphyrin dyes XW26-XW28 by introducing one or two alkyl/alkoxy chains into the auxiliary acceptor. The introduced chains can effectively suppress dye aggregation. As a result, XW26-XW28 show excellent photovoltages of 700, 701, and 711 mV, respectively, obviously higher than 645 mV obtained for XW11. Nevertheless, the optimized structures of XW26 and XW27 exhibit severe distortion, showing large dihedral angles of 57.2° and 44.0°, respectively, between the benzothiadiazole and benzoic acid units, resulting from the steric hindrance between the benzoic acid unit and the neighboring alkyl/alkoxy chain on the benzothiadiazole unit, and thus blue-shifted absorption, decreased photocurrents. and low efficiencies of 5.19% and 6.42% were observed for XW26 and XW27, respectively. Interestingly, XW26 exhibits a more blue-shifted absorption spectrum relative to XW27, indicating that the steric hindrance of the alkyl/alkoxy chains has a more pronounced effect than the electronic effect. Different from XW26 and XW27, XW28 contains only one alkyl chain neighboring the ethynylene unit, which does not induce obvious steric hindrance with the benzoic acid unit, and thus distortion of the molecule is not seriously aggravated compared with XW11. Hence, its absorption spectrum and photocurrent are similar to those of XW11. As a result, a higher efficiency of 9.12% was achieved for XW28 because of its suppressed dye aggregation and higher photovoltage. It is worth noting that a high efficiency of 10.14% was successfully achieved for XW28 upon coadsorption with CDCA, which is also higher than the corresponding efficiency obtained for XW11. These results provide a novel approach for developing efficient porphyrin dyes by introducing chains into the suitable position of the auxiliary benzothiadiazolyl moiety to suppress dye aggregation, without seriously aggravating distortion of the dye molecules.

Porphyrin dyes containing the carbazole electron donor have been designed and optimized by wrapping the porphyrin framework, introducing an additional ethynylene bridge to extend the wavelength range of light absorption, and further suppression of the dye aggregation by introducing additional alkoxy chains. Application of a cosensitization approach results in improved current density (Jsc) and open-circuit voltage (Voc) values, thus achieving the highest cell efficiency of 10.45 %. This work provides an effective combined strategy of molecular design and cosensitization for developing efficient dye-sensitized solar cells (DSSCs). In addition, carbazole has been demonstrated to be a promising donor for porphyrin sensitizers.

Fluorescence "turn-on" probes PC3 and C3 with weak background emissions were developed for hydrazine sensing. The aldehyde and dicyanovinyl groups were used as the recognition units for PD and C3, respectively. Because of low reactivity of the aldehyde group, the fluorescence of PC3 was enhanced by only ca. 93 folds upon addition of a large amount of 1646 eq. hydrazine. In contrast, 0 exhibited fluorescence enhancement by ca. 239 folds upon addition of only 1.3 eq. hydrazine, and thus it showed high sensitivity towards hydrazine, with the detection limit of 7 ppb. In aqueous systems, it also works well with improved selectivity for hydrazine over CN-. The weak fluorescence of PC3 and 0 can be ascribed to twisted intramolecular charge transfer (TICT) processes by the combination of the bulky diphenylamino and 9-anthryl units, which were well demonstrated by theoretical calculations, viscosity dependent fluorescence, and fluorescence decay behaviour. Addition of hydrazine induced the disappearance of the TICT deactivation pathway, resulting in the observed fluorescence enhancement. It can be concluded that the combination of the bulky diphenylamino and 9-anthryl units is an effective approach for developing fluorescence turn-on hydrazine probes based on the TICT mechanism.

Endowing both solvent independency and excellent thermal bistability, the benzobis(thiadiazole)-bridged diarylethene system provides an efficient approach to realize extremely high photocyclization quantum yields (Φo-c , up to 90.6 %) by both separating completely pure anti-parallel conformer and suppressing intramolecular charge transfer (ICT).

Using one ray of light to encode another ray of light is highly desirable because information in optical format can be directly transferred from one beam to another without converting back to the electronic format. One key medium to accomplish such an amazing task is photoswitchable molecules. Using bis(dithiazole)ethene that can be photoswitched between its ring-open and ring-closed states quantitatively with excellent fatigue resistance and high thermal stability, it is shown that quantitative photoreversibility allowed the photoswitching light to control other light travelling through the photoswitchable medium, a phenomenon of transferring information encoded in one light ray to others, thus imparting photo-optical modulation on the orthogonal light beam.

Four novel D–π–A porphyrin dyes (YQ1–YQ4) with 2-diphenylaminothiophene attached at the meso-position as the electron donor have been synthesized and used as the sensitizers for dye sensitized solar cells (DSSCs). 4-Ethynylbenzoic acid and 2-cyanoacrylic acid were incorporated as the anchoring moieties in YQ1, and YQ2–YQ4, respectively. Due to the extended conjugation size, the absorption spectra of YQ2–YQ4 showed Soret band maxima in the range of 447–468 nm, which is red shifted as compared to that of 446 nm for YQ1. Furthermore, in comparison with most reported porphyrin dyes with similar structures, YQ1–YQ4 demonstrate obviously red-shifted absorption maxima and broadened Soret bands, indicating that these porphyrin dyes may be developed as promising DSSC sensitizers. The electrochemical studies and DFT calculations indicated that all the four dyes were capable of serving as DSSC sensitizers. Thus, DSSCs were fabricated based on these dyes. The cells based on YQ4 showed the power conversion efficiency of 5.00%, which is higher than those of 4.23% and 4.38% for YQ2 and YQ3, respectively. This observation may be attributed to the suppression of the dye aggregation by the hexyl group attached to the thienyl ring of YQ4. On the other hand, YQ2–YQ4 demonstrated lower efficiencies compared with YQ1, which may be ascribed to the floppy structures of the cyanoacrylic acid-based porphyrins that provide free space for charge recombination. As a result, the DSSCs based on YQ1 exhibited the highest efficiency of 6.01%. This work demonstrates that the introduction of 2-diphenylaminothiophene into a porphyrin framework can obviously red-shift and broaden the absorption bands of the porphyrin dyes, resulting in high solar cell efficiencies. Hence, the introduction of 2-diphenylaminothiophene as the electron donor may be promising for the design of efficient porphyrin-based DSSC sensitizers.

XS1-XS3 have been synthesized by introducing an auxiliary acceptor into D-π-A dyes for simultaneous filling up of both absorption valleys of porphyrin dyes at around 550 and 380 nm. Thus, panchromatic DSSCs with the highest efficiency of 10.75% were achieved by cosensitization. This work provides a strategy for designing cosensitizers for porphyrin dyes.

Three photochromic compounds--2-butyl-5,6-bis[5-(4-methoxyphenyl)-2-methylthiophen-3-yl]-1 H-benzo[de]isoquinoline-1,3(2 H)-dione (BTE-NA), 4,5-bis[5-(4-methoxyphenyl)-2-methylthiophen-3-yl]benzo[c][1,2,5]thiadiazole (BTA), and BTTA, which contain naphthalimide, benzothiadiazole, and benzobisthiadiazole as six-membered ethene bridges with different aromaticities--were systematically studied in solution, sol-gel, and single-crystal states. They exhibit typical photochromic performance with considerably high cyclization quantum yields. BTE-NA, BTA, and BTTA form a typical donor-π-acceptor (D-π-A) system with significant intramolecular charge transfer (ICT) between HOMO and LUMO upon excitation, thus realizing the fluorescence modulation by both photochromism and solvatochromism. The three ethene bridges with different degrees of aromaticity can provide a systematic comparison of the thermal stability evolution for their corresponding closed forms (c-BTE-NA, c-BTA, and c-BTTA). c-BTE-NA shows first-order decay in various solvents from cyclohexane to acetonitrile. c-BTA only shows first-order decay in polar solvents such as chloroform, whereas it is stable in nonpolar solvents like toluene. In contrast, the less aromatic property of BTTA gives rise to its unprecedented thermal stability in various solvents even at elevated temperatures in toluene (328 K). Moreover, the small energy barrier between the parallel and antiparallel conformers allows the full conversion from BTTA to c-BTTA. In well-ordered crystal states, all three compounds adopt a parallel conformation. Interestingly, BTTA forms a twin crystal of asymmetric nature with interactions between the electron-rich oxygen atom of the methoxy group and the carbon atom of the electron-deficient benzobisthiadiazole moiety. This work contributes to the understanding of aromaticity-controlled thermal stability of photochromic systems based on a six-membered ring as an ethene bridge, and a broadening of the novel building blocks for photochromic bisthienylethene systems.

Four novel naphthalimide-based dyes (D-1, D-2, D-3 and D-4) were synthesized and utilized as sensitizers in dye-sensitized solar cells (DSCs), in which the triphenylamine (TPA) or indoline groups, naphthalimide unit and carboxylic group were functionalized as electron donor, acceptor and anchoring group, respectively. The naphthalimide unit was employed as the π-conjugation ring and electron acceptor for effectively realizing intramolecular charge separation in the oxidized states. In the series of dyes, the LUMO orbital is delocalized mainly on naphthalimide moieties, especially on the carbonyl group. Consequently, the LUMO electrons are isolated from the carboxyl anchoring group (-CH2CO2H) due to the presence of the methylene group, which could suppress the electron injection efficiency from the excited dyes to the TiO2 conduction band, thus leading to the inferior efficiencies of 1.10, 1.18, 2.27 and 2.70%, respectively, even though they exhibit broad spectral response and high extinction coefficients.

Near-IR (NIR) emission can offer distinct advantages for both in vitro and in vivo biological applications. Two NIR fluorescent turn-on sensors N,N'-di-n-butyl-2-(N-{2-[bis(pyridin-2-ylmethyl)amino]ethyl})-6-(N-piperidinyl)naphthalene-1,4,5,8-tetracarboxylic acid bisimide and N,N'-di- n-butyl-2-[N,N,N'-tri(pyridin-2-ylmethyl)amino]ethyl-6-(N-piperidinyl)naphthalene-1,4,5,8-tetracarboxylic acid bisimide (PND and PNT) for Zn(2+) based on naphthalenediimide fluorophore are reported. Our strategy was to choose core-substituted naphthalenediimide (NDI) as a novel NIR fluorophore and N,N-di(pyridin-2-ylmethyl)ethane-1,2-diamine (DPEA) or N,N,N'-tri(pyridin-2-ylmethyl)ethane-1,2-diamine (TPEA) as the receptor, respectively, so as to improve the selectivity to Zn(2+). In the case of PND, the negligible shift in absorption and emission spectra is strongly suggestive that the secondary nitrogen atom (directly connected to the NDI moiety, N(1)) is little disturbed with Zn(2+). The fluorescence enhancement of PND with Zn(2+) titration is dominated with a typical photoinduced electron-transfer (PET) process. In contrast, the N(1) atom for PNT can participate in the coordination of Zn(2+) ion, diminishing the electron delocalization of the NDI moiety and resulting in intramolecular charge-transfer (ICT) disturbance. For PNT, the distinct blueshift in both absorbance and fluorescence is indicative of a combination of PET and ICT processes, which unexpectedly decreases the sensitivity to Zn(2+). Due to the differential binding mode caused by the ligand effect, PND shows excellent selectivity to Zn(2+) over other metal ions, with a larger fluorescent enhancement centered at 650 nm. Also both PND and PNT were successfully used to image intracellular Zn(2+) ions in the living KB cells.

A supramolecular fluorescent sensor of F− based on intermolecular energy transfer is described. The maximum absorption wavelength of a pyrrolic compound 1 is 472 nm, which is coincident with the emission wavelength of a dipyridylamine-anthracene compound 2. In the CH2Cl2 solution of 1 and 2, the fluorescence of 2 was quenched because of the presence of intermolecular energy transfer from 2 to 1. When F− was added to this solution, the absorption maximum wavelength of 1 shifted from 472 to 594 nm due to a deprotonation process. Simultaneously, the fluorescence of 2 was recovered because of the interruption of the intermolecular energy transfer. Based on these observations, the combination of 1 and 2 can be regarded as a novel supramolecular fluorescence enhancing F− probe.

A supramolecular oligochromophoric system possessing exclusive binding sites for both a guest electron acceptor and an anionic cofactor species is developed, and anion-binding-induced stabilization of the charge-separated (CS) state is demonstrated. Toward this, intramolecular and intermolecular photochemical processes of a supramolecular complex of a bis-porphyrinyl-substituted oxoporphyrinogen with a bis(4-pyridyl)-substituted fullerene were investigated by using femtosecond and nanosecond laser flash photolysis measurements. Transient absorption spectra of the supramolecular complex obtained by femtosecond laser flash photolysis indicate that efficient electron transfer occurs from the porphyrin moiety to the fullerene moiety, followed by faster back electron transfer to the ground state. Binding of several different anionic species at the pyrrole amine groups of an oxoporphyrinogen unit within the supramolecular complex was found to improve the rate of the photoinduced electron transfer due to the favorable structural change. The anion binding also improves persistence of the photoinduced CS state between the anion-bound oxoporphyrinogen and fullerene moieties, which is produced by intermolecular electron transfer from the triplet excited state of free porphyrin molecules to free fullerene molecules, as indicated by the nanosecond laser flash photolysis measurements. In the case of fluoride anion binding, anion-complexation-induced stabilization of charge separation gave a 90-fold elongation of the CS state lifetime from 163 ns to 14 micros. Complexation with other anions (acetate or dihydrogen phosphate) also resulted in stabilization of the CS state, whereas weakly bound perchlorate anions gave no improvement. Complexation of anions to the oxoporphyrinogen center lowers its oxidation potential by nearly 600 mV, creating an intermediate energy state for charge migration from the ZnP(*+) to the oxoporphyrinogen:anion complex. An increase in reorganizational energy of electron transfer combined with the decrease in charge recombination driving force caused by anion binding results in an increase in the lifetime of the CS state.

Porphyrins are promising DSSC sensitizers due to their structural similarity to chlorophylls as well as their tunable strong absorption. Herein, a novel D-π-A porphyrin dye XW14 containing a strongly electron-donating triphenylamine moiety as the electron donor was designed and synthesized. To avoid undesirably decreased Voc caused by dye aggregation effect, two methoxy or hexyloxy chains were introduced to the para positions of the triphenylamine moiety to afford XW15 and XW16, respectively. To further extend the absorption to a longer wavelength, a benzothiadiazole unit was introduced as an auxiliary acceptor to furnish XW17. Compared with XW14, the introduction of additional methoxy or hexyloxy groups in XW15 and XW16 red-shift the onset wavelengths from 760 to 780 and 790 nm, respectively. More impressively, XW17 has a more extended π-conjugation framework, and thus, it exhibits a much broader IPCE spectrum with an extremely red-shifted onset wavelength of 830 nm, resulting in the highest Jsc (18.79 mA cm(-2)). On the other hand, the hexyloxy chains are favorable for suppressing the dye aggregation effect, and thus XW16 shows the highest Voc of 734 mV. As a result, XW16 and XW17 demonstrate photovoltaic efficiencies of 9.1 and 9.5%, respectively, higher than those of XW14 (8.6%) and XW15 (8.7%), and obviously higher than that of 7.94% for our previously reported dye, XW4. On the basis of optimized porphyrin dye XW17, we used a nonporphyrin dye with a high Voc and strong absorption around 500 nm (WS-5) as the cosensitizer to improve the Voc from 700 to 748 mV, with synergistical Jsc enhancement from 18.79 to 20.30 mA cm(-2). Thus, the efficiency was dramatically enhanced to 10.9%, which is among the highest efficiencies obtained for the DSSCs based on traditional iodine electrolyte. In addition, the DSSCs based on XW17 + WS-5 exhibit good photostability, which is beneficial for practical applications.

Cyanoacrylic and carboxyl groups have been developed as the most extensively used electron acceptor and anchoring group for the design of sensitizers for dye-sensitized solar cells. In terms of the photoelectric conversion efficiency, each of them has been demonstrated to be superior to the other one in certain cases. Herein, to further understand the effect of these two groups on cell efficiencies, a series of porphyrin sensitizers were designed and synthesized, with the acceptors systematically varied, and the effect of the neighboring ethynylene unit was also investigated. Compared with the sensitizer XW5 which contains a carboxyphenyl anchoring moiety directly linked to the meso-position of the porphyrin framework, the separate introduction of a strongly electron-withdrawing cyanoacrylic acid as the anchoring group or the insertion of an ethynylene unit can achieve broadened light absorption and IPCE response, resulting in higher Jsc and higher efficiency. Thus, compared with the efficiency of 4.77% for XW5, dyes XW1 and XW6 exhibit higher efficiencies of 7.09% and 5.92%, respectively. Simultaneous introduction of the cyanoacrylic acid and the ethynylene units into XW7 can further broaden light absorption and thus further improve the Jsc. However, XW7 exhibits the lowest Voc value, which is not only related to the floppy structure of the cyanoacrylic group but also related to the aggravated dye aggregation effect due to the extended framework. As a result, XW7 exhibits a relatively low efficiency of 5.75%. These results indicate that the combination of the ethynylene and cyanoacrylic groups is an unsuccessful approach. To address this problem, a cyano substituent was introduced to XW8 at the ortho position of the carboxyl group in the carboxyphenyl acceptor. Thus, XW8 exhibits the highest efficiency of 7.59% among these dyes. Further cosensitization of XW8 with XS3 dramatically improved the efficiency to 9.31%.

Photoswitching of bis(dithiazole)ethene can be regulated by Hg(II) ions and EDTA in a “lock-and-unlock” manner. The molecular photoswitch provides an enzyme-like binding pocket that selectively binds specifically to mercury ions, thus modulating the degree of photoswitching in its presence.

2,2'-Dipyridylamine and anthracene units were linked to afford highly emissive compounds whose Cu(2+) ensembles were developed as effective fluorescence turn-on CN(-) probes.

Cyanide sensing has attracted increasing interest due to its toxicity and wide use in industrial activities. Herein, we developed three colorimetric cyanide sensors by the modification of the α-position of a dipyrrin chromophore with various carbonyl groups, namely, C(6)F(5)CO, C(6)H(5)CO and CHO for 1, 2 and 3, respectively. In dichloromethane, these sensors respond to both CN(-) and F(-) with distinct colour changes. UV-Vis, (1)H NMR and HRMS measurements imply a two-process interaction between the sensors and CN(-). Initially, CN(-) forms a hydrogen bond with the NH moiety, and then it attacks the carbonyl group of the sensors via a nucleophilic addition reaction. In contrast, in aqueous systems, only cyanide induced vivid solution colour changes from light yellow to pink via nucleophilic addition reactions. The CN(-) detection limits reach a micromolar level of 3.6 × 10(-6) M, 4.2 × 10(-6) M and 7.1 × 10(-6) M for 1, 2 and 3, respectively. In view of the easy synthesis and the highly selective recognition of CN(-) with vivid colour changes, 1-3 may be developed as a novel and promising prototype of selective and sensitive colorimetric cyanide sensors.

A photochemically active dithiazolethene BN was designed and synthesized, exhibiting a specific gated photochromism. That is, the photochromic reactivity of BN is prevented to a great extent by BF(3), showing a "Lock" gate.

A conveniently synthesized photochromic compound, BTB-1, containing an unprecedented six-membered 2,1,3-benzothiadiazole unit as the center ethene bridge, possesses good photochromic performance, with a high cyclization quantum yield and moderate fatigue resistance in solution or an organogel system. The fluorescence of BTB-1 can be modulated by solvato- and photochromism. However, the analogue BTB-2, in which the dimethylthiophene substituents are relocated to the 5,6-positions of benzothiadiazole, does not show any detectable photochromism. To the best of our knowledge, this is the first example of six-membered bridge bisthienylethenes (BTEs) in which the photochromism can be controlled by the substitution position. The photochromism difference is elucidated by the analysis of resonance structure, the Woodward-Hoffmann rule, and theoretical calculations on the ground-state potential-energy surface. In a well-ordered single-crystal state, BTB-1 adopts a relatively rare parallel conformation, and forms an interesting two-dimensional structure due to the presence of multiple directional intermolecular interactions, including C-H···N and C-H···S hydrogen-bonding interactions, and π-π stacking interactions. This work contributes to several aspects for developing novel photochromic BTE systems with fluorescence modulation and performances controlled by substitution position in different states (solution, organogel, and single crystal).