Jibin Sun

Molecular and Crystal Structure Diversity, and Physical Properties of Tetrathiafulvalene Derivatives Substituted with Various Aryl Groups through Sulfur Bridges

A library of tetrathiafulvalene (TTF) derivatives (TTF-1-TTF-47) bearing aryl groups attached through sulfur bridges has been created. The peripheral aryl groups exert a significant influence on both the electronic and crystallographic properties of the resulting TTFs. These TTFs display broad absorption bands at 400-500 nm caused by intramolecular charge-transfer transitions between the aryl groups and central TTF core, and their first redox potentials increase with increasing electron-withdrawing ability of the aryl groups. In their crystal structures (22 examples), the central TTF cores adopt various conformations, including chair, half-chair, boat, and planar conformations. Moreover, the peripheral aryl groups exhibit multiple alignment modes with respect to the central TTF core, caused by their rotation about the two C-S bonds of the sulfur bridges. The packing motifs of these TTFs depend on both the nature of the aryl groups and their spatial alignment modes. Driven by intermolecular van der Waals forces and π-π interactions between the aryl groups and between the aryl groups and the TTF core, these TTFs adopt various packing structures. As a typical example, TTF-14, an achiral molecule, adopts a helical chain stack through intermolecular atomic close contacts. Moreover, the molecular geometries and packing motifs of these TTFs are sensitive to environmental variation, as exemplified by TTF-28, which adopts three distinct crystal modifications with diverse molecular geometries and stacking modes under different crystallization conditions. This work indicates that these TTFs are potential candidates as electronic materials, as well as functional building blocks for supramolecular assembly.

Honeycomb supramolecular frameworks of organic–inorganic hybrid cluster composed of cation radical and Keggin-type polyoxometalate

Keggin-type phosphomolybdic acid (H3PMo12O40) promoted the formation of a cation radical of tetra(thienylthio)-tetrathiafulvalene (TT-TTF), consequently resulting in a cation radical complex [(TT-TTF)+•]3[(PMo12O40)3−](CH2Cl2), which shows self-assembly in solution and forms microtubes. The molecular level structure of the microtube is evaluated by X-ray diffraction analysis, which reveals that the microtube is produced via various non-covalent interactions in the hierarchical assembly process: the electrostatic interactions between (TT-TTF)+• and (PMo12O40)3− afford an organic–inorganic hybrid triangular nanocluster [(TT-TTF)+•]3[(PMo12O40)3−] as the building block; the strong π–π interactions between (TT-TTF)+• result in the cluster-based two-dimensional honeycomb nanosheet; the van der Waals forces between the nanosheets lead to the propagation along the third direction to form a three-dimensional supramolecular framework possessing nano-sized channels.

Decorating tetrathiafulvalene (TTF) with fluorinated phenyls through sulfur bridges: facile synthesis, properties, and aggregation through fluorine interactions.

Tetrathiafulvalene derivatives (TTF1-TTF9) bearing fluorinated phenyl groups attached through the sulfur bridges have been synthesized by employing a copper-mediated C-S coupling reaction of C6 H5-x Fx I (x=1, 2, 5) and a zinc-thiolate complex, (TBA)2 [Zn(DMIT)2 ] (TBA=tetrabutyl ammonium, DMIT=1,3-dithiole-2-thione-4,5-dithiolate), as the key step. Particularly, the selective synthesis of C6 F5 -substituted (TTF8) and C6 F4 -fused (TTF9) TTFs from C6 F5 I is disclosed. The physicochemical properties and crystal structures of these TTFs are fully investigated by UV/Vis absorption spectra, cyclic voltammetry, molecular orbital calculation, and single-crystal X-ray diffraction. The exchange of hydrogen versus fluorine on the peripheral phenyl groups show a notable influence on both the electronic and crystallographic natures of the resulting TTFs: 1) lowering both the HOMO and the LUMO energy levels, 2) modulating the electrochemical properties by regioselective and/or the degree of fluorination, 3) enhancing the driving forces of stacking by multiple fluorine interactions (F⋅⋅⋅S, CF⋅⋅⋅π/πF , CF⋅⋅⋅FC, and CF⋅⋅⋅H). This work indicates that the decoration with fluorinated phenyls holds promise to produce functional TTFs with novel electronic and aggregation features.

Donor–acceptor type co-crystals of arylthio-substituted tetrathiafulvalenes and fullerenes

Summary A series of donor–acceptor type co-crystals of fullerene (as the acceptor) and arylthio-substituted tetrathiafulvalene derivatives (Ar-S-TTF, as the donor) were prepared and their structural features were thoroughly investigated. The formation of co-crystals relies on the flexibility of Ar-S-TTF and the size matches between Ar-S-TTF and fullerene. Regarding their compositions, the studied co-crystals can be divided into two types, where types I and II have donor:acceptor ratios of 1:1 and 1:2, respectively. Multiple intermolecular interactions are observed between the donor and acceptor, which act to stabilize the structures of the resulting co-crystals. In the type I co-crystals, the fullerene molecule is surrounded by four Ar-S-TTF molecules, that is, two Ar-S-TTF molecules form a sandwich structure with one fullerene molecule and the other two Ar-S-TTF molecules interact with the fullerene molecule along their lateral axes. In the type II co-crystals, one fullerene molecule has the donor–acceptor mode similar to that in type I, whereas the other fullerene molecule is substantially surrounded by the aryl groups on Ar-S-TTF molecules and the solvent molecules.

Copper ion salts of arylthiotetrathiafulvalenes: synthesis, structure diversity and magnetic properties

Summary The combination of CuBr2 and arylthio-substituted tetrathiafulvalene derivatives (1–7) results in a series of charge-transfer (CT) complexes. Crystallographic studies indicate that the anions in the complexes, which are derived from CuBr2, show diverse configurations including linear [Cu(I)Br2]–, tetrahedral [Cu(II)Br4]2–, planar [Cu(II)2Br6]2–, and coexistence of planar [Cu(II)Br4]2– and tetrahedral [Cu(II)Br3]– ions. On the other hand, the TTFs show either radical cation or dication states that depend on their redox potentials. The central TTF framework on most of TTFs is nearly planar despite the charge on them, whereas the two dithiole rings on molecule 4 in complex 4·CuBr4 are significantly twisted with a dihedral angle of 38.3°. The magnetic properties of the complexes were elucidated. The temperature-dependent magnetic susceptibility of complex 5·Cu2Br6 shows the singlet–triplet transition with coupling constant J = −248 K, and that of 3·(CuBr4)0.5·CuBr3·THF shows the abrupt change at 270 K caused by the modulation of intermolecular interactions. The thermo variation of magnetic susceptibility for the other complexes follows the Curie–Weiss law, indicating the weak antiferromagnetic interaction at low temperature.

Inclusion complexes of fullerenes with flexible tetrathiafulvalene derivatives bearing four aryls through sulfur bridges

TTF derivatives decorated with four aryls through the sulfur bridges are employed to form the donor–acceptor type inclusion complexes with fullerenes. The key factor for the formation of inclusion complexes is the introduction of structural flexibility in TTF molecules along with the molecular size matching with fullerenes. A crystallographic study indicates that the structures of the resulting complexes are stabilized by a multidimensional intermolecular interaction network consisting of TTF cores, peripheral aryls, and fullerenes, which in turn gives rise to the electronic communication between the donor and the acceptor as proved by the solid state absorption spectra. Moreover, the fullerene molecules form the two-dimensional sheet structure in the complexes.

Remarkable Nonlinear Optical Response of Pyrazine-fused Trichalcogenasumanenes and Their Application for Optical Power Limiting

The C3v-symmetric hetera buckybowl trichalcogenasumanenes have attracted recent interest due to their unique features in chemical and optoelectronic aspects. To gain a nonlinear optical (NLO) response, the electron-withdrawing unit pyrazine was introduced onto tricalcogenasumanenes to give the pyrazine-fused trithiasumanene (1) and triselenasumanene (2) as reported herein. Compounds 1 and 2 exhibit typical NLO properties which are verified using open-aperture Z-scan technology under a 532 nm nanosecond laser pulse. It is found that the NLO performance of these two molecules is much better than the state-of-the-art NLO material C60. The time-resolved transient absorption clearly verified that the NLO properties of 1 and 2 originate from the reverse saturable absorption (RSA) of the triplet excited-state. Owing to their remarkable NLO performance, 1 and 2 are further employed as optical power limiting (OPL) materials. Compounds 1 and 2 exhibit OPL behavior with a limiting threshold of 1.78 J cm−2 and 2.43 J cm−2, respectively; this performance is better than that of C60 (12.85 J cm−2). This work indicates that the sumanene derivatives are promising candidates for NLO and OPL materials.