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Organic and organometallic π-conjugated molecules with inherent nonlinear optical (NLO) responses have attracted great interest due to their controllable properties via rational structure modifications. However, most of the state-of-the-art materials such as porphyrins, phthalocyanines, and diacetylenes exhibit NLO responses at visible-light regions. Recently, diketopyrrolopyrrole (DPP) based donor–acceptor (D–A) type π-conjugated copolymers have been found to exhibit NLO responses which can reach up to 1064 nm. However, the design rationality of the structure toward NLO properties is not well understood. Herein, four alternating DPP-based copolymers are constructed by using the electron donors of 2-phenylpyridine for P1, 2-thienylpyridine for P2 and their Pt(II)-incorporated moieties for P1Pt and P2Pt. All copolymers display intense intramolecular charge transfer (ICT) processes, and the ICT absorption can be extended to the near-infrared (NIR) region due to the strong D–A interaction of the π-conjugated backbone. The variation tendency of optical bandgaps estimated from the onset of ICT absorption is P1 (1.60 eV) > P1Pt (1.56 eV) > P2 (1.47 eV) > P2Pt (1.44 eV). Open- and closed-aperture Z-scan experiments disclosed that all copolymers exhibit broadband (532 and 1064 nm) NLO properties due to the synergistic effect of excited state absorption and the ICT process upon excitation of 8 ns as well as 25 ps laser pulses. Pt(II)-incorporation can promote or switch the NLO properties due to the efficient triplet-state absorption introduced by the heavy-atom effect. The improvement of the NLO properties is of the order P1 < P1Pt < P2 < P2Pt, which is consistent with the decreasing trend of the copolymer bandgaps. These results will provide guidelines for the rational design of materials toward broadband NLO responses and advanced applications.

Photodynamic therapy (PDT) has emerged as an attractive alternative in cancer therapy, but therapeutic effects suffer from low photosensitizing efficiency and poor retention of photosensitizes in cancer cells. This paper reports the photosensitizers which show absorption and emission in the long-wavelength region and high photosensitizing efficiency can be formed in situ in cells from 4,6-dibromothieno[3,4-b]thiophene derivative (TT-5-P) after white light irradiation. The self-oligomerization of TT-5-P is uptaken in cells upon light irradiation-induced cell apoptosis simultaneously and efficiently. In addition, the formation of oligomers (TT-5-Ps) enhances the retention time in cells remarkably, which is advantageous for boosting the photodynamic therapy efficiency. Moreover, the selectivity toward tumor cells of TT-5-P can be improved obviously via the formation of complex of TT-5-P with albumin. This in situ photoinduced self-oligomerization strategy can be utilized to design effective biomaterials for long-term imaging and improved therapy.

Conjugated molecules with low lying LUMO levels are demanding for the development of air stable n-type organic semiconductors. In this paper, we report a new A-D-A'-D-A conjugated molecule (DAPDCV) entailing diazapentalene (DAP) and dicyanovinylene groups as electron accepting units. Both theoretical and electrochemical studies manifest that the incorporation of DAP unit in the conjugated molecule can effectively lower the LUMO energy level. Accordingly, thin film of DAPDCV shows n-type semiconducting behavior with electron mobility up to 0.16 cm2 ⋅V-1 ⋅s-1 after thermal annealing under N2 atmosphere. Moreover, thin film of DAPDCV also shows stable n-type transporting property in air with mobility reaching 0.078 cm2 ⋅V-1 ⋅s-1 .

The selective and sensitive detection of α-ketoglutaric acid ( KA ) is of great importance not only for biological studies but also for early diagnosis of cancers. In comparison with other assays, fluorescence detection is advantageous. However, the fluorescence turn-on detection of KA remains rare. In this paper, we disclose a new fluorescence detection of KA with the ensemble of silole-A and n -octanohydrazide by utilizing the aggregation induced emission feature of silole compounds and the chemical reaction between KA and n -octanohydrazide. The ensemble displays reasonably good sensitivity and selectivity toward KA , and KA with concentration as low as 1.5 μM can be detected.

A tetraphenylethylene based aggregation induced emission (AIE) probe, TPENNO 2 , bearing a 2,4-dinitrobenzenesulfonyl pendant was designed and synthesized for light-up and discriminatory detection of Cys over Hcy and GSH in PBS. The 2,4-dinitrobenzenesulfonyl group quenched the fluorescence of TPENNO 2 . While after thiol group promoted nucleophilic aromatic substitution reaction, TPENNO 2 can be converted to fluorescent TPENH 2 . The discriminatory detection of Cys over Hcy and GSH comes from the different reaction kinetic profiles of TPENNO 2 with the thiol residues of Cys, Hcy and GSH. Moreover, TPENNO 2 can be used to image biothiols in living HeLa cells.

Singlet fission (SF), in which one singlet exciton (S₁) splits into two triplets (T₁) on adjacent molecules through a correlated triplet-pair ¹(TT) state, requires precise but difficult tuning of exciton energetics and intermolecular electronic couplings in the solid state. Here we demonstrate anti-aromatic 4nπ dibenzopentalenes (DPs) as a new class of single-chromophore based intramolecular SF materials, which exhibit optically allowed S2 state with E(S₂) > 2E(T₁) and optically forbidden S₁ state. Ultrafast population transfer from high-lying S₂ state to ¹(TT) state was observed in monomeric solution of styryl-substituted DP (SDP) on sub-picosecond timescale. More importantly, we provide compelling evidence of exciton diffusion (ED) of ¹(TT) state to yield two individual long-lived triplets in SDP thin film. The overall triplet yield via iSF and subsequent triplet-pair diffusion can be as high as 142±10% in thin-film.

The rational design of multifunctional materials with both emissive and semiconducting properties remains a challenge. A multifunctional cruciform donor–acceptor (D–A) molecule, 2,2′-(((4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)bis(thiophene-5,2-diyl))bis(methanylylidene))dimalononitrile (BDTTM), which contains a benzodithiophene as the central core, has been synthesized and, based on the output and transfer characteristics of the corresponding FETs, thin films of BDTTM exhibited ambipolar semiconducting behavior. Notably, FETs with thin films of BDTTM showed a photoresponse in both p- and n-channels, and drain-source-current enhancement under white-light irradiation could be detected, even at a low light intensity of 0.1 mW cm−2. Furthermore, BDTTM exhibited red-light emission both in solution and as a crystalline solid. A microplate of BDTTM with red-light emission displayed typical optical waveguiding behavior.

Apart from sensing and imaging, luminogens with aggregation-induced emission (AIE) are also interesting for photosensitizing. The photosensitizing behavior and bacteria-killing performance of a pyridinium-substituted tetraphenylethylene with an alkyne group (TPE-A-Py+ ) is reported herein. Interestingly, TPE-A-Py+ exhibits higher photosensitizing efficiency than TPE-Py+ (without alkyne group) when I- was used as a counteranion. This is well explained by the fact that the ΔEST between the excited singlet state (S1 ) and triplet state (T1 ) was lower for TPE-A-Py+ than for TPE-Py+ , according to theoretical calculations. Moreover, replacement of I- with other anions (PF6- , N(SO2 CF3 )2- and BPh4- ) led to a decrease of photosensitizing efficiency for TPE-A-Py+ . Notably, TPE-A-Py+ could be used as an efficient photosensitizer to photo-inactivate ampicillin-resistant (ampr ) E. coli at low concentration under white-light irradiation very quickly.

Rigid and planar conjugated molecules have substantial significance due to their potential applications in organic electronics. Herein we report two highly fused ladder type conjugated molecules, TTCTTC and TTTCTTTC, with up to 10 fused rings in which the fused-thiophene rings are fused to the chromeno[6,5,4-def]chromene unit. Both molecules show high HOMO levels and accordingly they can be oxidized into their radical cations with absorptions extending to 1300 nm in the presence of trifluoroacetic acid. Thin films of TTCTTC and TTTCTTTC exhibit p-type semiconductor properties with hole mobilities up to 0.39 cm2 V−1 s−1. Moreover, TTCTTC shows a high fluorescence quantum yield of up to 16.5% in the solid state.

Biphenyl, as the elementary unit of organic functional materials, has been widely used in electronic and optoelectronic devices. However, over decades little has been fundamentally understood regarding how the intramolecular conformation of biphenyl dynamically affects its transport properties at the single-molecule level. Here, we establish the stereoelectronic effect of biphenyl on its electrical conductance based on the platform of graphene-molecule single-molecule junctions, where a specifically designed hexaphenyl aromatic chain molecule is covalently sandwiched between nanogapped graphene point contacts to create stable single-molecule junctions. Both theoretical and temperature-dependent experimental results consistently demonstrate that phenyl twisting in the aromatic chain molecule produces different microstates with different degrees of conjugation, thus leading to stochastic switching between high- and low-conductance states. These investigations offer new molecular design insights into building functional single-molecule electrical devices.

In this work, a conjugated polymer PNV is developed, linking naphthalene diimide with a vinyl linkage. Owing to the C–H⋯O hydrogen bond between the carbonyl and the vinyl, PNV exhibits a high red emission with a quantum yield of 33.4% in the solid state while it shows n-type properties with an electron mobility up to 1.5 × 10−3 cm2 V−1 s−1 in organic field effect transistors, simultaneously.

Two-photon excited fluorescence microscopy and nanoparticle-assisted photodynamic therapy (PDT) are two important areas in biomedical research, and their combination can be more beneficial. A type of red emissive photosensitizer (PS) with aggregation-induced emission (AIE) features, which is called tetraphenylethylene (TPE-red), was synthesized and further encapsulated with poly(styrene-co-maleic anhydride) (PSMA) to form nanoparticles. Two-photon fluorescence, as well as two-photon excited reactive oxygen species (ROS) generation by TPE-red–PSMA nanoparticles, was characterized. A large two-photon absorption cross-section was observed at 1040 nm with a femtosecond (fs) laser. PDT via two-photon excitation was well realized on tumor cells, using TPE-red–PSMA nanoparticles as PSs under 1040 nm fs laser excitation. Based on our study, we believe that two-photon excited PDT with AIE-active PSs has great potential applications in deep tissue imaging-guided therapy.

We present four conjugated donor–acceptor (D–A) polymers PBPDT-Si, PBPDSe-Si, PBPDT, and PBPDSe entailing a new electron acceptor Pechmann dye framework, i.e., bipyrrolylidene-2,2′(1H,1′H)-dione (BPD), and thiophene and selenophene as the respective electron donors. PBPDT-Si and PBPDSe-Si contain siloxane-terminated side chains, while PBPDT and PBPDSe bear branching alkyl chains. The respective HOMO energies of PBPDT-Si and PBPDSe-Si are slightly higher than those of PBPDT and PBPDSe, whereas the respective LUMO energies of PBPDT-Si and PBPDSe-Si are slightly lower than those of PBPDT and PBPDSe. The results reveal that (i) thin films of all four polymers show ambipolar semiconducting performances under a nitrogen atmosphere, (ii) hole and electron mobilities are more balanced for PBPDT-Si and PBPDSe-Si, and (iii) the employment of siloxane-terminated side chains is beneficial for improving charge transporting compared to branching alkyl side chains. Thin film hole and electron mobilities of PBPDT-Si can ...

Solid state emissive materials with high quantum yields and tunable emissions are desirable for various applications. A new TPE derivative (1) with two carbazole moieties and two cyano groups is reported, which shows typical aggregation induced emission behavior. Four crystals 1a, 1b, 1c, and 1d are obtained after crystallization from N,N-dimethylformamid (DMF), trichloromethane (CHCl3 ), tetrahydrofuran (THF), and dichloromethane (CH2 Cl2 ), respectively. Crystal structural analyses reveal that (i) molecules of 1 co-crystallize with DMF, CHCl3 , THF, and CH2 Cl2 in 1a, 1b, 1c, and 1d, respectively, and (ii) conformations of 1 are different within 1a, 1b, 1c, and 1d, and compound 1 within crystal 1a adopts the most twisting conformation. Crystalline solids 1a, 1b, 1c, and 1d exhibit high emission quantum yields up to 0.65, but their emission colors are varied from blue to green. In comparison, the amorphous solid of 1 is yellow-emissive with emission maximum at 542 nm. Moreover, the blue- or green-emissive crystalline solids and the yellow-emissive amorphous solid can be inter-converted by the grinding of crystalline solids and exposure of the amorphous solid to vapors of appropriate solvents. It is also demonstrated that microrods of 1a, 1b, and 1d show typical optical waveguiding behavior.

An AIE based tetraphenylethylene derivative (MOTIPS-TPE) with a pyridinium pendant was synthesized for light-up sensing of F− in aqueous solution without additives. The fluoride ion promoted cleavage reaction gave MOTIPS-TPE high selectivity toward F− over other common anions. Moreover, MOTIPS-TPE can be used to monitor F− in living HeLa cells.

Three conjugated D–A terpolymers PBPD1, PBPD2, and PBPD3 with the Pechmann dye-derived electron acceptor and dithienyl-diketopyrrolopyrrole as co-acceptors are presented. Their HOMO/LUMO energies and absorptions can be tuned by varying the ratios of two acceptors. Importantly, HOMO energies of these terpolymers are lowered by increasing the content of the Pechmann dye-derived electron acceptor in the conjugated backbones. The thin blend films of PBPD1, PBPD2, and PBPD3 with PC71BM have been tested as active layers for polymer solar cells. The blend of PBPD1:PC71BM shows a high power conversion efficiency of up to 5.21%, which is higher than that with the blend of the dithienyl-diketopyrrolopyrrole-based polymer without the Pechmann dye-derived electron acceptor and PC71BM. In addition, the neat thin films of PBPD1, PBPD2, and PBPD3 exhibit ambipolar semiconducting properties with hole and electron mobilities up to 0.604 cm2 V−1 s−1 and 0.225 cm2 V−1 s−1.

Three new conjugated D–A terpolymers PADPP1, PADPP2 and PADPP3, which contain diketopyrrolopyrrole (DPP) as electron acceptors and thiophene/anthracene as electron donors, are described. In comparison with PDPP3T which contains just DPP and thiophene units, the DPP moieties are partially replaced with anthracene units in PADPP1, PADPP2 and PADPP3. The HOMO/LUMO levels of PADPP1, PADPP2 and PADPP3 are slightly enhanced in comparison with those of PDPP3T. Moreover, the incorporation of the anthracene units into the backbones leads to the formation of nanofibrils with an appropriate width within the blending thin films of PADPP2 with PC71BM. The short circuit currents (JSC) of the photovoltaic cells with blends of PADPP1, PADPP2 and PADPP3 with PC71BM are higher than those with the PDPP3T/PC71BM blend. As a result, PADPP1, PADPP2 and PADPP3 display better photovoltaic performances than PDPP3T after blending each polymer with PC71BM under the same conditions. The PCE of the photovoltaic cell of the PADPP2/PC71BM blending thin film at a weight ratio of 1 : 2 as the active layer can reach 6.24%.

Three new conjugated polymers DPPA1, DPPA2, and DPPA3 with dithienyldiketopyrrolopyrrole (DPP) and azulene moieties were synthesized and characterized. The five-membered rings of azulene are connected with DPP in DPPA1 and DPPA2, whereas the seven-membered ring of azulene is incorporated into the backbone of DPPA3. The LUMO energy of DPPA3, which was determined on the basis of the respective cyclic voltammograms and absorption spectra, is lower than those of DPPA1 and DPPA2. OFETs were successfully fabricated with thin films of DPPA1, DPPA2, and DPPA3. Thin films of DPPA1 and DPPA2 exhibit p-type semiconducting properties with hole mobilities up to 0.97 cm2 V–1 s–1, whereas typical ambipolar behavior is found for thin film of DPPA3 with hole and electron mobilities reaching 0.062 cm2 V–1 s–1 and 0.021 cm2 V–1 s–1, respectively. The results reveal that semiconducting properties of DPPA1, DPPA2, and DPPA3 can be tuned by varying the linkage positions of azulene with DPP moieties. Furthermore, DPPA1, DPPA2, ...

The efficiency of the intersystem crossing process can be improved by reducing the energy gap between the singlet and triplet excited states (ΔE ST), which offers the opportunity to improve the yield of the triplet excited state., The efficiency of the intersystem crossing process can be improved by reducing the energy gap between the singlet and triplet excited states (ΔE ST), which offers the opportunity to improve the yield of the triplet excited state. Herein, we demonstrate that modulation of the excited states is also an effective strategy to regulate the singlet oxygen generation of photosensitizers. Based on our previous studies that photosensitizers with aggregation-induced emission characteristics (AIE) showed enhanced fluorescence and efficient singlet oxygen production in the aggregated state, a series of AIE fluorogens such as TPDC, TPPDC and PPDC were synthesized, which showed ΔE ST values of 0.48, 0.35 and 0.27 eV, respectively. A detailed study revealed that PPDC exhibited the highest singlet oxygen efficiency (0.89) as nanoaggregates, while TPDC exhibited the lowest efficiency (0.28), inversely correlated with their ΔE ST values. Due to their similar optical properties, TPDC and PPDC were further encapsulated into nanoparticles (NPs). Subsequent surface modification with cell penetrating peptide (TAT) yielded TAT–TPDC NPs and TAT–PPDC NPs. As a result of the stronger singlet oxygen generation, TAT–PPDC NPs showed enhanced cancer cell ablation as compared to TAT–TPDC NPs. Fine-tuning of the singlet-triplet energy gap is thus proven to be an effective new strategy to generate efficient photosensitizers for photodynamic therapy.

A new sensitive fluorescence turn-on detection of gamma-radiation is reported by taking advantage of aggregation induced-emission (AIE) behaviour of the tetraphenylethylene unit and the cascade radiochemical and protonation reactions.

In this paper, we report Zincke’s salt-substituted tetraphenylethylenes 1a and 1b with Cl– and PF6– as counteranions, respectively. The crystal structure of 1b was determined. Both 1a and 1b are almost nonemissive even in the aggregated states. This is attributed to the photoinduced electron transfer from 2,2-bis(4-methoxyphenyl)-1-phenylvinyl-phenyl unit to 1-(2,4-dinitrophenyl) pyridinium unit within 1a and 1b. The results demonstrate that the emissions of 1a and 1b in aqueous solution can be switched on upon either reaction with GSH or light irradiation. On the basis of the reaction between 1a and GSH, 1a can be utilized for the fluorescence turn-on detection of GSH selectively, and GSH with concentration as low as 36.9 nM can be detected. The transformation of 1b into 2 under light irradiation results in the fluorescence imaging of Hela and U2OS cells and phototoxicity toward Hela and U2OS cells after the protonation of pyridine unit in 2 because of the acidic environment of tumor cells. Aggregates of...

In this Feature Article, we have summarized the recent advances in the fluorescence modulation of tetraphenylethylene and silole fluorophores by manipulating the respective aggregation/deaggregation with amphiphiles. These include (i) the assembly of neutral tetraphenylethylene analogues with the aid of an ionic amphiphile, (ii) the aggregation of ionic tetraphenylethylene and silole induced by amphiphiles, and (iii) bio/chemosensors based on the aggregation/deaggregation of AIE fluorophores tuned by ionic amphiphiles.

In this paper seven salts of pyridinium-substituted tetraphenylethylene with different anions are reported. They show typical aggregation-induced emission. Crystal structures of three of the salts with (CF(3)SO(2))(2) N(-), CF(3) SO(3)(-), and SbF(6)(-) as the respective counter anions, are determined. The emission behavior of their amorphous and crystalline solids is investigated. Both amorphous and crystalline solids, except for the one with I(-), are highly emissive. Certain amorphous solids are red-emissive with almost the same quantum yields and fluorescence life-times. However, some crystalline solids are found to show different emission colors varying from green to yellow. Thus, their emission colors can be tuned by the counter anions. Furthermore, certain crystalline solids are highly emissive compared to the respective amorphous solids. Such solid-state emission behavior of these pyridinium-substituted tetraphenylethylene salts is interpreted on the basis of their crystal structures. In addition, optical waveguiding behavior of fabricated microrods is presented.

In this paper we report two DPP-based conjugated molecules DPPBT and DPPTT in which the respective electron withdrawing moieties 2,1,3-benzothiadiazole and thiazolo[5,4-d]thiazole are flanked by two DPP moieties. For comparison, DPPBZ containing 1,4-diethynylbenzene and two DPP moieties were synthesized. HOMO/LUMO energies of DPPBT, DPPTT and DPPBZ were estimated on the basis of cyclic voltammetric data. Owing to the fact that LUMO energies of DPPBT and DPPTT were lowered to ca. −3.5 eV, thin films of both DPPBT and DPPTT exhibit ambipolar semiconducting properties under N2 atmosphere with hole and electron mobilities up to 0.25 cm2 V−1 s−1 and 0.09 cm2 V−1 s−1, respectively. In comparison, thin film of DPPBZ just shows p-type semiconducting property. Notably, ambipolar semiconductors with relatively high carrier mobility are rarely reported for DPP-containing small conjugated molecules. Alternatively, both DPPBT and DPPTT can function as electron donors for photovoltaic materials. Thin films of DPPTT:PC71BM and DPPBT:PC71BM at a weight ratio of 1 : 1 exhibit PCEs of 4.18% and 2.44%, respectively, with VOC higher than 0.95 V.

In this paper, we report the design, synthesis and semiconducting behavior of two conjugated D–A polymers P-BPDTT and P-BPDBT which entail BPD, a Pechmann dye framework, as electron accepting moieties, and thieno[3,2-b]thiophene and 2,2′-bithiophene as electron donating moieties. Their HOMO/LUMO energies and bandgaps were estimated based on the respective cyclic voltammgrams and absorption spectra of thin films. P-BPDTT possesses lower LUMO level and narrower bandgap than P-BPDBT. On the basis of the characterization of the field-effect transistors, a thin film of P-BPDTT exhibits ambipolar semiconducting properties with hole and electron mobilities reaching 1.24 cm2 V–1 s–1 and 0.82 cm2 V–1 s–1, respectively, after thermal annealing. In comparison, thin film of P-BPDBT only shows p-type semiconducting behavior with hole mobility up to 1.37 cm2 V–1 s–1. AFM and XRD studies were presented to understand the interchain arrangements on the substrates and the variation of carrier mobilities.

A new selective fluorescence turn-on detection of hydrogen peroxide was established by taking advantage of the aggregation induced-emission (AIE) behavior of tetraphenylethylene unit and the reaction of hydrogen peroxide toward the arylboronic ester group in compound 1 . Moreover, compound 1 was successfully utilized for the selective detection of d -glucose in aqueous solution.

Herein, we report the synthesis of new tetraphenylethylene derivatives 1-5 that feature electron-donating (methoxy) and -accepting (dicyanomethane) groups as AIE-active molecules with tunable emission colors. The crystal structures of compounds 3 and 4 are described and the intermolecular interactions within their crystals agree with the observation that they exhibit strong solid-state emission. Compounds 1-4 exhibit typical AIE behavior and their emission maxima are red-shifted in the order: 1

In this paper we report the synthesis and crystal structures of emissive organic molecule (1a) based on pyrido[3,4-g]isoquinoline framework as well as its isomers 1b and 1c. The emission quantum yields decrease after transformation of pyridine moieties in 1a into the cyclic-amides in 1b and 1c. The fluorescent spectral results reveal that 1a, 1b, and 1c exhibit no AIE behavior. This is tentatively attributed to intramolecular weak C⋯H interactions, which may impede the intramolecular rotations based on the crystal structures of 1a and 1c. Interestingly, 1a, 1b, and 1c are emissive in the solid state, and among them 1a possesses the highest emission quantum yield (0.22). Moreover, the fluorescence of 1a in solution and solid state can be reversibly tuned by reactions with trifluoroacetic acid and triethylamine. Microarea PL studies reveal that microrods of 1a and these after exposure to HCl gas show typical waveguide behavior.

The protonation of azulene cores offers significant conductance tuning in single-molecule junctions with quantum interference., The protonation of azulene derivatives with quantum interference effects is studied by the conductance measurements of single-molecule junctions. Three azulene derivatives with different connectivities are synthesized and reacted with trifluoroacetic acid to form the protonated states. It is found that the protonated azulene molecular junctions produce more than one order of magnitude higher conductance than the neutral states, while the molecules with destructive interference show more significant changes. These experimental observations are supported by our recently-developed parameter free theory of connectivity, which suggests that the largest conductance change occurs when destructive interference near the Fermi energy in the neutral state is alleviated by protonation.

In this paper, we report the synthesis and characterization of two new D-A-D molecules (E)-5,5′-bis(5-(benzo[b]thiophen-2-yl)thiophen-2-yl)-1,1′-bis(2-ethyl- hexyl)-[3,3′-bipyrrolylidene]-2,2′(1H,1′H)-dione (BTBPD) and (E)-5,5′-bis- (5-(benzo[b]furan-2-yl)thiophen-2-yl)-1,1′-bis(2-ethylhexyl)-[3,3′-bipyrrolylidene]-2,2′(1H,1′H)-dione (BFBPD). They entail bipyrrolylidene-2,2′(1H,1′H)-dione (BPD, known as Pechmann dye) as the electron-accepting core that is flanked by two benzo[b]thiophene moieties and two benzo[b]furan moieties, respectively. Crystal structures of BTBPD and BFBPD provide solid evidence for the intermolecular donor–acceptor (D-A) interactions, which are favorable for improving charge transport performance. Organic field-effect transistors (OFETs) were prepared based on thin films of BTBPD and BFBPD through solution-processed technique. OFETs of BTBPD exhibit relatively high hole mobility up to 1.4 cm2 V–1 s–1 with high on/off ratio up to 106. In comparison, the hole mobility of OFETs with B...

A simple synthetic approach to dithiazole-fused naphthalene diimides 1 and 2 from 2,6-dibromoNDI (2BrNDI) was described. Note that the synthesis did not involve any metallic catalysts. Based on their cyclic voltammograms, the LUMO energies of 1 and 2 were estimated to be −3.99 eV and −3.98 eV, respectively, being lower than that of unsubstituted NDI. Thin films of 1 and 2 show n-type semiconducting behaviors. OFETs of 1 exhibit electron mobility up to 0.15 cm2 V−1 s−1 with high on/off ratio (under ambient conditions) after annealing.

The synthesis of a new tetrathiafulvalene derivative with an electron-withdrawing benzothiadiazole moiety and its use in thin-film organic field-effect transistors (OFETs) are reported. Compared to reported OFETs with other TTF derivatives, a high hole mobility up to 0.73 cm2 V−1 s−1, low off-current and high on/off ratio up to 105 are demonstrated. In addition, the developed OFETs show fast responsiveness toward chemical vapors of DECP (diethyl chlorophosphate) or POCl3 which are simulants of phosphate-based nerve agents. In contrast to previously reported OFET-based sensors, off-current is used as the output signal, which increases quickly upon exposure to either DECP or POCl3 vapors. High sensitivity is demonstrated toward DECP and POCl3 vapors, with concentrations as low as 10 ppb being detected. These OFETs are also responsive to TNT vapor. The sensing mechanisms for the new type of OFET are discussed.

Green fluorescent protein (GFP)-like chromophores 1–5, in which the p-hydroxylphenyl group is substituted with large aromatic moieties, were synthesized and their crystal structures were determined. Compared with that of p-hydroxybenzylideneimidazolinone (GFP chromophore), the fluorescence spectra of 1–5 are red-shifted because of elongated of π-conjugation. However, the incorporation of large aromatic moieties cannot inhibit the intramolecular torsional motions and, thus, 1–5 are generally weakly fluorescent in solution. The results manifest that the solid-state emission of these GFP-like chromophores is significantly influenced by the intermolecular packing. The emission spectra of 1–5 are further red-shifted in the solid-state, and 5 in the crystalline state emits in at red wavelengths with an emission maximum at 624 nm. 1, 3, and 4 are weakly emissive in both crystalline and powder forms. Interestingly, one crystalline state of 2 (2 B) emits relatively strongly, whereas another crystalline state 2 A emits rather weakly.

A triptycene-based cylindrical macrotricyclic molecule 1, which contains one tetrathiafulvalene (TTF) unit and four glycol chains, is reported. Both absorption and ESR spectroscopic studies clearly indicate that intermolecular electron transfer occurs from TTF in 1 to tetrachloroquinone in the presence of certain metal ions (e.g. Sc3+, Pb2+, and Zn2+). Based on comparative studies with 3 and 5, the close intermolecular alignment between 1 and tetrachloroquinone is proposed to occur by the synergic coordination of metal ions with oxygen atoms of the glycol chains and tetrachloroquinone (as well as the sulfur atoms of TTF). The intermolecular electron transfer is facilitated by the positive shift of the reduction potentials of tetrachloroquinone through coordination with metal ions, and the close alignment of 1 and tetrachloroquinone, which is beneficial for stabilizing the electron-transfer state.

The synthesis and optical investigations of di(p-methoxylphenyl)dibenzofulvene (1) and its analogues 2, 3, 4, 5, 6, and 7 with different lengths of alkoxyl chains are presented. All of these molecules exhibit emission in the solid state. The following interesting properties are reported for compound 1: 1) the solid-state fluorescence of 1 is dependent on the polymorphism forms; the two crystalline forms 1a and 1b are strongly blue- and yellow-green-emissive, whereas the amorphous solid is weakly fluorescent with orange emission; 2) on the basis of crystal-structural analysis, the intermolecular interactions will restrict the internal rotations, leading to fluorescence enhancement for the two crystalline forms 1a and 1b; however, the difference in emission color between 1a and 1b is ascribed to the molecular conformational alteration; 3) the solid-state fluorescence of 1 can be tuned by heating and cooling as well as grinding. Importantly, microrods of 1a and 1b exhibit outstanding optical waveguide behaviors. Moreover, amplified spontaneous emission for 1b and multimode-lasing behavior for 1a are presented. Besides the studies of compound 1, the crystal structures and solid-state fluorescence behaviors of 2, 3, 4, 5, 6, and 7 are also described.

A new electroactive polymer 1 with alternating NDI (naphthalene diimide) moieties and fluorinated alkyl chains was prepared and characterized. Gels of polymer 1 were formed in several solvents. Interestingly, gels of polymer 1 exhibited responsiveness toward N2H4, F− and CN−. Absorption and ESR spectroscopic studies revealed that such responsiveness is owing to the reduction of NDI moieties into the respective NDI.−. In addition, thin films of polymer 1 were easily prepared with spin-coating technique and the electrical conductivity of thin films reached 52.4 S/m after exposure to N2H4 vapor.

A new ratiometric fluorescence detection of heparin is reported with the ensemble of 1 and 2. This method is based on the respective ACQ (aggregation-caused quenched emission) and AIE (aggregation-induced emission) features of anthracene and tetraphenylethene. DLS, CLSM and fluorescent spectral investigations suggest that the variation of the fluorescence intensity ratio I(497)/I(421) is due to the formation of aggregates of 1 and 2 with heparin. Moreover, this ratiometric fluorescence method can be used to distinguish heparin from its analogues (HA, Dex). In order to demonstrate the practical utilization of this ratiometric fluorescence method, the fluorescence spectra of the ensemble of 1 and 2 were measured in the presence of serum, and the results indicate that it is possible to eliminate the interferences from other biomolecules by either subtracting the background fluorescence intensities or lowering the pH values of the sample solutions.

A new sensitive and selective fluorescence turn-on sensor for Zn(2+) (1) was developed by taking advantage of the aggregation-induced emission of the tetraphenylethylene framework. In addition, the corresponding ester precursor of 1 was successfully used for intracellular Zn(2+) imaging.

Three linear and one cyclic tetrathiafulvalene-1,4,5,8-naphthalenediimide (TTF-NDI) compounds 1, 2, 3, and 4 were synthesized and studied in the presence of metal ions. Both absorption and electron spin resonance spectroscopic studies clearly indicate that electron transfer occurs from TTF to the NDI unit in the presence of metal ions (Pb(2+) and Sc(3+)) for linear compounds 1 and 2. The mechanism based on the metal ion coordination is proposed for the electron transfer within 1 and 2 after the addition of metal ions. Compound 3 exhibits intramolecular charge-transfer absorption because of the cyclophane framework. Interestingly, intramolecular electron transfer also takes place for 3 after the addition of either Sc(3+) or Pb(2+).

A highly selective naked-eye detection of ClO − is successfully established with probe 1 by taking advantage of the oxidation transformation of p -methoxyphenol into benzoquinone with ClO − and the ICT absorption within the electron donor–acceptor compound. The color of the solution of probe 1 was changed, obviously upon addition of ClO − and ClO − with concentration as low as 1.74 μM can be analyzed in aqueous solution with probe 1 . Moreover, the interferences of other anions can be neglected.

A 2,2′-bipyridyl-bridged tetrathiafulvalene (TTF)-quinone dyad (1) was synthesized and characterized. Both absorption and ESR spectroscopic studies clearly indicate that electron transfer occurs from TTF to the quinone unit for dyad 1 in the presence of metal ions. The results manifest that the coordination of dyad 1 with metal ions plays a key role in facilitating the intramolecular electron transfer.

A dendron-substituted tetraphenylethene low molecular weight gelator (LMWG)compound, LMWG1, is designed and investigated. Gelation-induced fluorescence enhancement is observed for the gel based on LMWG1 and its fluorescence can be reversibly tuned by varying the temperature of the ensemble. The photoinduced energy-transfer can occur between LMWG1 and PI2 (perylene diimide) in the gel phase, but it cannot occur in the corresponding solution. The emission color of the gel of LMWG1 and PI2 can be tuned from cyan, yellow, to red by varying the concentration of PI2. By taking advantage of the photochromic transformation of spiropyran, the emission color of the organogels based on LMWG1 and SP3 can be switched by alternating UV and visible-light irradiations. The emission color can also be tuned by varying the irradiation time. In this way, organogels based on LMWG1 with multiemission color can be achieved in the presence of SP3 after light irradiations.

Tetrathiafulvalene–flavin dyads 1 and 2 are reported. Both absorption and ESR spectral studies show that the intramolecular electron transfer occurs from TTF to flavin units in dyads 1 and 2 in the presence of Pb2+/Sc3+. But, the electron transfer is more efficient for dyad 1 in the presence of Pb2+/Sc3+. Electrochemical studies manifest that coordination of dyads 1 and 2 with Pb2+/Sc3+ play an important role in facilitating the electron transfer within dyads 1 and 2.

The immobilization of fluorescent photoinduced electron transfer (PET) switches/sensors into solid state, which usually cannot maintain their identical properties in solution, has remained a big challenge. Herein, a water-stable anthracene and maleimide appended zirconium-based-metal-organic framework (Zr-MOF; UiO-68-An/Ma) is reported. Unlike the regular intramolecular "fluorophore-spacer-receptor" format, the separated immobilization of fluorescent (anthracene) and acceptor (maleimide) groups into the framework of a multivariate MOF can also favor a pseudo-intramolecular fluorescent PET process, resulting in UiO-68-An/Ma with very weak fluorescence. Interestingly, after Diels-Alder reaction or thiol-ene reaction of maleimide groups, the pseudo-intramolecular fluorescent PET process in UiO-68-An/Ma fails and the solid-state fluorescence of the crystals is recovered. In addition, UiO-68-An/Ma shows an interesting application as solid-state fluorescent turn-on sensor for biothiols, with the naked eye response at a low concentration of 50 µmol L-1 within 5 min. This study represents a general strategy to enable the efficient tuning of fluorescent PET switches/sensors in solid state, and considering the fluorescence of the PET-based MOFs can be restored after addition of analyte/target species, this research will definitely inspire to construct stimuli-responsive fluorescent MOFs for interesting applications (e.g., logic gate) in future.

For the development of multistimuli responsive organogels, the new organic gelator LMWG 1, featuring electroactive TTF and photoresponsive azobenzene groups, was designed and studied. By manipulating the redox state of the TTF group in LMWG 1, the gel-sol transition for organogels with the LMWG 1 can be reversibly tuned by either chemical or electrochemical oxidation/reduction reactions. Alternatively, the photoisomerization of the azobenzene group in LMWG 1 can also trigger the gel-sol transition. Therefore, organogels with LMWG 1 respond not only to thermal stimuli but also to redox reactions and light irradiation.

The synthesis, self-assembly, and spectroscopic investigations of spiropyran (SP)-functionalized dendron 1 are reported. Under UV light irradiation, assembly of 1 into nano-/microparticles occurs due to the transformation of the closed form of SP into the open merocyanine (MC) form. The formation of these nano-/microparticles is confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) experiments in addition to the confocal laser scanning microscopy (CLSM) measurements. These nano-/microparticles exhibit relatively strong red emission. It is interesting to note that the direct cooling of the toluene/benzene solution of 1 to 0 °C leads to gel formation. Multivalent π–π interactions due to the dendron in 1 may be the driving-force for the gelation. The UV light irradiation cannot destroy the gel phase, and in fact, the gel–gel transition is successfully realized. The purple-blue gel exhibits relatively strong red fluorescence; moreover, the fluorescence can be reversibly switched by alternating UV and visible light irradiation. The results clearly indicate that the MC form after aggregation becomes more stable and fluorescent.

Two new organic gelators 1 and 2 based on the silole (silacyclopentadiene) framework were designed with the end to develop switchable fluorescent organogels, by making use of the aggregation-induced emission (AIE) feature of silole derivatives. As for other silole derivatives, compounds 1 and 2 exhibited AIE behavior as indicated by the significant fluorescence enhancement by introducing water to the THF solutions. Compounds 1 and 2 can gel hexane, methylcyclohexane and heptane. Large fluorescence enhancement was observed for compounds 1 and 2 after gelation. Moreover, their fluorescence intensities can be changed reversibly accompanying the gel–solution transition through alternating cooling and heating. Therefore, thermally-driven fluorescence switches can be achieved with organogels based on 1 and 2 .

Electron transfer can occur from the TTF units to the substituted quinone unit in a new TTF-quinone-TTF triad 1 containing the N,N-dialkylaniline-substituted quinone unit flanked by two TTF units, in the presence of metal ions (Pb(2+), Zn(2+), and Sc(3+)). Simultaneously, the corresponding charge transfer within the substituted quinone unit becomes weak in the presence of metal ions. Moreover, the metal ion-promoted electron transfer and the intramolecular charge transfer can be tuned by alternating UV and visible light irradiation in the presence of spiropyran.

A highly selective ratiometric fluorescence sensor for Ag+ was developed with a molecular motif containing one pyrene and two adenine moieties.