Chengyun Wang

Conjugated poly(aryleneethynylenesiloles) and their application in detecting explosives

Hyperbranched and linear conjugated polysiloles incorporating arylene ethynylene subunits (6 and 7) were synthesized by the Sonogashira reaction. The two polymers possess unusual phenomena of PL, with gradual addition of water in their THF solution, the intensity of PL firstly increased and then decreased, this may be due to the aggregate-enhanced emission (AEE) effect and aggregation-caused quenching (ACQ) effect. The polymers function as sensitive fluorescent chemosensors for the detection of explosives, such as picric acid (PA) and TNT. The quenching constants of 6 for PA and TNT were 4.7 × 10−2 ppm−1 and 4.6 × 10−3 ppm−1, respectively. The quenching constants of 7 for PA and TNT were 8.6 × 10−2 ppm−1 and 6.5 × 10−3 ppm−1 respectively. The polymer 7 has more detective efficiency for PA and TNT than that of polymer 6, this may be due to the less steric hindrance.

Synthesis and properties of a tetrathiafulvalene–perylene tetracarboxylic diimide–tetrathiafulvalene dyad

A donor–acceptor–donor dyad 4 involving 2-sulfur-3-methylthio-6,7-bis(hexylthio)tetrathiafulvalene (TTF) as a donor attached directly to N,N′-dibutylperylene-3,4,9,10-tetracarboxylic diimide (PDI) as an acceptor was synthesized by condensation of N,N′-dibutyl-1,6-dibromo-3,4,9,10-perylenetetracarboxylic diimide and 2-(2-cyanoethylthio-3-methylthio-6,7-bis(hexylthio)tetrathiafulvalene. The cyclic voltammetric (CV) data implied significant intramolecular interaction and the absorption spectrum indicated that there was an intramolecular charge transfer (ICT) interaction between TTF and PDI moieties in dyad 4. Comparing with PDI 13, the fluorescence emission intensity of dyad 4 was quenched almost quantitatively, which might result from the photo-induced electron transfer (PET) interaction between the PDI and TTF moieties in dyad 4. The fluorescence intensity of dyad 4 could be reversibly modulated by sequential oxidation and reduction of the TTF unit using chemical methods. Thus dyad 4 can be regarded as a new reversible fluorescence-redox dependent molecular switch.

Synthesis and properties of polysilanes with tetrathiafulvalene as pendant group

Two polysilanes with tetrathiafulvalene (TTF) as pendant groups were synthesized by reaction of 2-cyanoethyl substituted TTF 1 with (chloromethylphenyl)dimethyl(phenyl)polysilane, or reaction of 4-vinylphenyl-TTF 2 with poly[methylsilane-co-methyl(phenyl)silane]. The structures and properties of TTF-polysilanes and their intermediates were characterized by 1H NMR, mass, GPC, UV/Vis, IR and cyclic voltammetry (CV). The results of UV/Vis and CV of these polysilanes indicated interaction between the TTF moieties and σ-electron delocalized Si–Si chain in the ground states. These polysilanes doped by I2 exhibited high conductivities (10−2 S cm−1).

A new fluorescence molecular switch incorporating TTF and tetraphenylporphyrin units

A donor-σ-acceptor compound incorporating tetrathiafulvalene and tetraphenylporphyrin units was synthesized. The structures of the target compound and its intermediates have been characterized by 1H NMR, ESI MS, UV-vis, IR and mp. The results of UV-vis and cyclic voltammetry of the compound indicated negligible intramolecular charge transfer interaction in its ground state. The fluorescence and fluorescence lifetime of the compound were reduced, compared to tetraphenylporphyrin, which evidently indicated that photoinduced electron transfer occurred from the tetrathiafulvalene (TTF) unit to the tetraphenylporphyrin unit in the excited state. The fluorescence intensity of the compound could be reversibly modulated by sequential oxidation and reduction of the TTF unit using electrochemical and chemical methods. Therefore, a new fluorescence molecular switch based on TTF and porphyrin units was established.

A new colorimetric and fluorescent probe with a large stokes shift for rapid and specific detection of biothiols and its application in living cells

In this work, a new reversible colorimetric and fluorescent probe for sequential recognition of copper ions and biothiols is synthesized easily. Based on the chelation-enhanced fluorescence quenching (CHEQ) effect, this probe shows high sensitivity and selectivity towards Cu2+, which can be detected by the naked eye. And this experimental phenomenon can also be realised upon addition of biothiols, restoring their initial fluorescence intensity. This probe also features a very high response speed (less than 5 seconds) and a large stokes shift (178 nm) toward Cu2+ and biothiols. Moreover, the detection limit for Cu2+ and biothiols is as low as 7.34 nM and 10.3 nM, respectively. Additionally, this ON-OFF-ON-type fluorescence recognition cycle can be repeated more than 5 times by addition of Cu2+ and biothiols in turn. Particularly, this 1-Cu2+ ensemble is further successfully applied for GSH detection in living cells.

Conjugated ethynylene-fluorene polymers with electro-donating TTF as pendant groups: Synthesis, electrochemical and spectroscopic properties

A series of conjugated ethynylene-fluorene polymers with electro-donating TTF as pendant groups (P2–P4) were synthesized by using Sonogashira coupling reaction, and two functionalization methods, i.e. prepolymerization and postpolymerization, were developed. The composition and purity of the corresponding products were analyzed by 1H NMR. The results proved the functionalization of P2 (pre) and P2 (post) were 40% and 100%, respectively. The results also indicated that the postpolymerization method would be a better approach to prepare TTF-pendant conjugated ethynylene-fluorene polymers. The postpolymerization methodology could be extended to synthesize other conjugated fluorene-based polymers bearing TTF units (P3 and P4). The polymers mentioned above exhibited good solubility in normal organic solvents and higher conductivity (neutral conductivity ∼2–4 × 10−6 S cm−1; doped conductivity ∼1–3 × 10−3 S cm−1). Moreover, the fluorescence intensity of P2 (post) could be modulated by the oxidation of TTF units, which makes it an attractive candidate for the fluorescence switch.

Urethane tetrathiafulvalene derivatives: synthesis, self-assembly and electrochemical properities.

Summary This paper reports the self-assembly of two new tetrathiafulvalene (TTF) derivatives that contain one or two urethane groups. The formation of nanoribbons was evidenced by scanning electron microscopy (SEM) and X-ray diffraction (XRD), which showed that the self-assembly ability of T 1 was better than that of T 2. The results revealed that more urethane groups in a molecule did not necessarily instigate self-assembly. UV–vis and FTIR spectra were measured to explore noncovalent interactions. The driving forces for self-assembly of TTF derivatives were mainly hydrogen bond interactions and π–π stacking interactions. The electronic conductivity of the T 1 and T 2 films was tested by a four-probe method.

Synthesis and electrochromic performances of polymeric tetrathiafulvalene–bithiophene

Sulfur-based heterocycles were one of appealing building blocks in functional materials, due to their outstanding optical/electronical performance. Assembled DTTF-BTh which combined from two different sulfur heterocycles was synthesized by condensation of 2-cyanoethylthio-3-methylthio-6, 7-bis (hexylthio) tetrathiafulvalene (TTF-1), and 4, 4′-bis (2′-bromoethoxy)- 3, 3′-bithiophene (DBE-BTh). The full structural and physical characterizations of novel DTTF-BTh were studied by 1H NMR, Mass, UV–Vis absorption, and electrochemical measurements. The two heterocycle moieties were connected successfully but inclined to perform individually. This could be explained as electron separation by alkyl chains. Electropolymerization was also conducted. The result indicated that DTTF-BTh could directly form polymeric films on prepared ITO glass via electrochemical deposition. Moreover, the deposited polymer film possessed an electrochromic performance.

Synthesis of ethynyl end-capped oligo-aryl ethers

A series of aryl ether oligomers end-capped with ethynyl groups have been synthesised via a three-step process, i.e. iodination of oligo-aryl ethers, nucleophilic substitution of the iodide group with 2-methyl-3-butyn-2-ol catalysed by Pd/Cu and subsequent deacetonation in KOH/toluene. Effects of reaction temperature and the Pd/Cu catalyst on iodination and the substitution reaction are discussed.