2,5-Distyryl-dithieno[2,3-b:2′,3′-d]thiophene (DEP-bt-DTT), an isomer of 2,5-distyryl-dithieno [2,3-b:3′,2′-d]thiophene (DEP-bb-DTT) and 2,5-distyryl-dithieno[3,2-b:2′,3′-d]thiophene (DEP-tt-DTT), was synthesized. Organic field-effect transistors (OFETs) based on these three isomers were fabricated. The structure cell parameters and the formation of intermolecular interactions in their single crystals show regular change when the positions of sulphur atoms vary from top–bottom–top in DEP-tt-DTT to bottom–bottom–top in DEP-bt-DTT, then to bottom–bottom–bottom in DEP-bb-DTT. Combining the results of theoretical calculations and OFET performances, it reveals that: (1) the positions of sulphur atoms determine the contribution extent of sulphur atoms to the molecular conjugation and the formation of intermolecular interactions; (2) the existence of the intermolecular interactions, especially for S–π, benefits for the charge transport; (3) the field-effect mobility (μ) increases with increasing of the sulphur atom contribution to the molecular conjugation.

The novel propeller type compound, 2,4,6-tri(anthracen-9-yl)-1,3,5-triazine (TAT) with C3 symmetry was synthesized by using 9-anthryl lithium with 1,3,5-trichlorotriazine or 2-chloro-4,6-dimethoxy-1,3,5-triazine in the presence of palladium catalyst in 22–48% yield. Another two propeller-like compounds, 2-(anthracen-9-yl)-4,6-dimethoxy-1,3,5-triazine (3) and 2,4-di(anthracen-9-yl)-6-methoxy-1,3,5-triazine (4) were obtained at the same time. The propeller type structures of TAT, 3 and 4 were confirmed by crystal analysis and theoretical calculations. The intramolecular C–C bond rotations between the anthryl groups and the triazine units in molecules TAT, 3 and 4 were regarded as the key factor to understand their spectroscopic behaviors in fluid medium and rigid solution.

Thiophene-based organic semiconductors used as the active components have received much attention. Their photoelectric properties can be easily tuned with various substitutions at different positions on molecular structures. Here, we synthesized series cyclopentadithiophene (CDT) derivatives with sulfur atoms at ortho- (o-CDT), meta- (m-CDT), and para-positions (p-CDT) of the bridge carbon. These CDT derivatives were substituted by carbonyl/dicyanomethylene at the bridge position and/or by phenyl groups at the α position, respectively. Due to the different conjugation extent and the variation of donor–acceptor (D–A) interaction originating from the change of sulfur atom position, diverse absorption spectra were observed. Especially for dicyanomethylene substituted o-CDT with phenyl as substitution group (DPCN-o-CDT), its absorption spectrum covers the whole region of visible light. Combining with the electrochemical behaviors and theoretical calculations, it was found that the sulfur atoms mainly contribute to the molecular conjugation in these CDT derivatives, especially for o-CDT derivatives. For phenyl groups, they primarily act as electron donor in m-CDT derivatives, and chiefly contribute to molecular conjugation in p-CDT derivatives, and simultaneously work as electron donor and conjugation component in o-CDT derivatives, respectively.

A series of derivatives based on annelated β-oligothiophenes were synthesized and characterized as active layer in organic field-effect transistors (OFETs). Highest field-effect mobility of 0.52 V−1 s−1 for 2,5-dibiphenyl-dithieno[2,3-b:3′,2′-d]thiophene (DBP-DTT), 2.2 cm2 V−1 s−1 for 2,5-distyryl-dithieno[2,3-b:3′,2′-d]thiophene (DEP-DTT), and 0.16 cm2 V−1 s−1 for 1,4-di[2-dithieno[2,3-b:3′,2′-d] thiophen-2-yl-vinyl]benzene (DDTT-EP) were obtained, while 2,5-diphenyl-dithieno [2,3-b:3′,2′-d]thiophene (DP-DTT) presents no field-effect behaviors. Their thermal, optical and electrochemical properties, topographical and X-ray diffraction patterns of films, and the single crystal structures were also investigated. With the end-capping groups changing in these materials, the intermolecular interactions could transform from S–S in DP-DTT to S–C in DBP-DTT, to S–π in DEP-DTT, and to the coexisting of S–S and S–π in DDTT-EP. According to the device performances and the results of transfer integral calculations, it was revealed that S–π intermolecular interaction benefits not only improving the mobility but also reducing the threshold voltage (VT), while S–S intermolecular interaction is not favorable for promoting the mobility.Graphical abstractIntermolecular interaction in the single crystals of DTT derivatives.Highlights► The intermolecular interaction can transfer from S–S to S–C, to S–π, and to the coexisting of S–S and S–π. ► The molecules adopt a condensed arrangement as the S–C intermolecular interaction existing. ► S–π intermolecular interaction benefits not only improving the mobility but also reducing the threshold voltage.

A novel bull’s horn-shaped oligothienoacene with seven fused thiophene rings (1) based on dithieno[2,3-b:2′,3′-d]thiophene (2) was efficiently synthesized. X-ray diffraction data indicate that 1 possesses an extraordinary compressed sandwich-herringbone arrangement and shows strong intermolecular S···C and S···S interactions. In addition, the UV/vis properties, theoretical calculations, and cyclic voltammetry behaviors of 1 are also described.

Organic field-effect transistors based on two derivatives of annelated β-oligothiophenes are fabricated. High mobility of 2.2 cm2 V−1 s−1 is obtained for 2,5-distyryl-dithieno[2,3-b:3′,2′-d]thiophene (DEP-DTT) while 2,5-diphenyl-dithieno[2,3-b:3′,2′-d]thiophene (DP-DTT) presents no field-effect characteristics. The existence of S–π intermolecular interaction in DEP-DTT, which is introduced by CC double bonds, plays an important role in the molecular arrangement both in single crystal and thin film structures, and the charge transport of organic field-effect transistors.

Organic field-effect transistors based on two derivatives of annelated β-oligothiophenes are fabricated. High mobility of 2.2 cm2 V−1 s−1 is obtained for 2,5-distyryl-dithieno[2,3-b:3′,2′-d]thiophene (DEP-DTT) while 2,5-diphenyl-dithieno[2,3-b:3′,2′-d]thiophene (DP-DTT) presents no field-effect characteristics. The existence of S–π intermolecular interaction in DEP-DTT, which is introduced by CC double bonds, plays an important role in the molecular arrangement both in single crystal and thin film structures, and the charge transport of organic field-effect transistors.

2,5-Distyryl-dithieno[2,3-b:2′,3′-d]thiophene (DEP-bt-DTT), an isomer of 2,5-distyryl-dithieno [2,3-b:3′,2′-d]thiophene (DEP-bb-DTT) and 2,5-distyryl-dithieno[3,2-b:2′,3′-d]thiophene (DEP-tt-DTT), was synthesized. Organic field-effect transistors (OFETs) based on these three isomers were fabricated. The structure cell parameters and the formation of intermolecular interactions in their single crystals show regular change when the positions of sulphur atoms vary from top–bottom–top in DEP-tt-DTT to bottom–bottom–top in DEP-bt-DTT, then to bottom–bottom–bottom in DEP-bb-DTT. Combining the results of theoretical calculations and OFET performances, it reveals that: (1) the positions of sulphur atoms determine the contribution extent of sulphur atoms to the molecular conjugation and the formation of intermolecular interactions; (2) the existence of the intermolecular interactions, especially for S–π, benefits for the charge transport; (3) the field-effect mobility (μ) increases with increasing of the sulphur atom contribution to the molecular conjugation.