Chain-length dependent growth dynamics of n-alkanes on silica investigated by energy-dispersive x-ray reflectivity in situ and in real-time

We compare the growth dynamics of the three n-alkanes C(36)H(74), C(40)H(82), and C(44)H(90) on SiO(2) using real-time and in situ energy-dispersive x-ray reflectivity. All molecules investigated align in an upright-standing orientation on the substrate and exhibit a transition from layer-by-layer growth to island growth after about 4 monolayers under the conditions employed. Simultaneous fits of the reflected intensity at five distinct points in reciprocal space show that films formed by longer n-alkanes roughen faster during growth. This behavior can be explained by a chain-length dependent height of the Ehrlich-Schwoebel barrier. Further x-ray diffraction measurements after growth indicate that films consisting of longer n-alkanes also incorporate more lying-down molecules in the top region. While the results reveal behavior typical for chain-like molecules, the findings can also be useful for the optimization of organic field effect transistors where smooth interlayers of n-alkanes without coexistence of two or more molecular orientations are required.     

High performance single-crystal field-effect transistors based on twisted polyaromatic semiconductor pyreno[4,5-a]coronene

A novel p-channel semiconductor pyreno[4,5-a]coronene has been synthesized and characterized. The highly fused π-conjugated framework has a twisted geometry with an excellent on-top cofacial π-π stacking in the crystal structure and with a centroid-to-centroid distance of 3.808 ?. Single-crystal field effect transistors based on the molecule exhibit a high mobility of ~0.89 cm(2) V(-1) s(-1) and an on/off ratio of ~6 × 10(4).     

醌式杂环化合物的设计、合成及应用性能研究进展

醌式杂环(噻吩、吡咯、呋喃等)分子具有结构刚性、最高占据分子轨道(HOMO)/最低未占据分子轨道(LUMO)能级低、能级带隙窄和摩尔消光系数高等特点.醌式分子因其结构平面性特点,分子间作用力较强,因而分子间电荷传输能力强.目前,醌式杂环分子已成为有机半导体材料领域特别是有机场效应晶体管领域的研究热点.根据醌式杂环分子的结构特点,以端基为分类依据,综述了近年来醌式杂环化合物在分子设计、合成及应用性能等方面的研究进展,并展望了醌式杂环分子的发展前景.     

Heptagon‐Embedded Pentacene: Synthesis,Structures, and Thin‐Film Transistors of Dibenzo[d,d′]benzo[1,2‐a:4,5‐a′]dicycloheptenes

This study presents a new class of conjugated polycyclic molecules that contain seven‐membered rings, detailing their synthesis, crystal structures and semiconductor properties. These molecules have a nearly flat C₆‐C₇‐C₆‐C₇‐C₆ polycyclic framework with a p‐quinodimethane core. With field‐effect mobilities of up to 0.76 cm² V^?1 s^?1 as measured from solution‐processed thin‐film transistors, these molecules are alternatives to the well‐studied pentacene analogues for applications in organic electronic devices.     

Heptagon‐Embedded Pentacene: Synthesis,Structures, and Thin‐Film Transistors of Dibenzo[d,d′]benzo[1,2‐a:4,5‐a′]dicycloheptenes

This study presents a new class of conjugated polycyclic molecules that contain seven‐membered rings, detailing their synthesis, crystal structures and semiconductor properties. These molecules have a nearly flat C₆‐C₇‐C₆‐C₇‐C₆ polycyclic framework with a p‐quinodimethane core. With field‐effect mobilities of up to 0.76 cm² V⁻¹ s⁻¹ as measured from solution‐processed thin‐film transistors, these molecules are alternatives to the well‐studied pentacene analogues for applications in organic electronic devices.     

Hexyl‐Substituted Oligoselenophenes with Central Tetrafluorophenylene Units: Synthesis,Characterisation and Application in Organic Field Effect Transistors

A series of selenophene oligomers incorporating conjugated fluorinated phenylene units have been synthesised as potential semiconductor materials for organic field‐effect transistors (OFETs). X‐ray crystallography shows that the molecules are held in close proximity by several short intermolecular contacts, making them ideal candidates for OFET applications.

     

Simple fabrication of a smart microarray of polystyrene microbeads for immunoassay

We describe a simple method to fabricate an array of polystyrene microbeads (PS μbeads) conjugated with an elastin-like polypeptide (ELP) on a glass surface using a removable polymer template (RPT). A thin layer of adhesive was spun-cast on glass and cured by UV radiation. Micropatterns of an RPT were then transferred onto the surface by microcontact printing. The adhesion of PS μbeads on the surface depended on the adhesion performance of the adhesive layer, which could be adjusted by irradiation time. An array of PS μbeads conjugated with ELP was used for a smart immunoassay of prostate-specific antigen (PSA), a cancer marker. By controlling the phase transition of ELP molecules, PSA molecules were selectively adhered or released from the bead surface. The selective and reversible binding of PSA molecules on the bead surface was characterized with fluorescence microscopy.     

LEED, STM, and TDS studies of ordered thin films of the rhombus-shaped polycondensed aromatic hydrocarbon C54H22, on MoS2, GeS, and graphite

Low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), and thermal desorption spectroscopy (TDS) are used to study vacuum vapor-deposited molecular thin films of the rhombus-shaped polycondensed aromatic hydrocarbon "rhombus-C54", C54H22, on MoS2 and graphite (0001) and on GeS (010) substrates. It is found that this compound forms well-ordered incommensurate superstructures of the closest packed flat-lying molecules in well-defined azimuthal orientations to the substrate. These films are thermally remarkably stable. By TDS, a monolayer binding energy on graphite of 2.3 eV was derived, whereas the molecules in the second layer were found to be less strongly bound (1.9 eV). This difference allows the preparation of monolayers by desorbing multilayers at the appropriate temperature. Apparently, this molecule is a promising candidate for further studies aiming at applications in organic electronics such as organic field effect transistors or light emitting displays.     

Organic Ambipolar Conjugated Molecules for Electronics: Synthesis and Structure–Property Relationships

The field of organic electronics has been developed vastly in the past two decades, and the performance and lifetime of these devices are critically dependent on the materials development, device design, deposition processes, and modeling, among which the active materials of organic semiconductor play a crucial role. The unique properties of organic semiconductor are largely based on the versatility to synthesize multifunctional organic conjugated materials by judicious molecular design. To effectively adjust the optoelectronic properties, especially energy levels, of organic semiconductor, the scientists have presented a synthesis methodology of organic ambipolar conjugated molecules, in which typical p‐dope type and n‐dope type segments are incorporated into one molecule. The present review summarizes the progress on organic ambipolar conjugated molecules for electronics in the past few years. Some issues to be addressed are also highlighted and discussed.

     

PICOSECOND FLUORESCENCE AND ELECTRON TRANSFER IN PRIMARY PHOTOSYNTHETIC PROCESSES

Abstract. Under conditions that drive the reaction centers (RC's) into the "closed" state, the lifetime ( T ) of the fluorescence emitted by antenna molecules increases from 80 to 200 ps in PS I, from 300 to 600 ps in PS II, and from 200 to 500 ps in bacterial chromatophores. In Rhodopseudomonas sphaeroides strain 1760-1, the decay curve for fluorescence from the RC's has a component with T ₂= 15 ps due to the bacteriochlorophyll of the RC, and a second component with T ₂= 250 ps due to bacteriopheophytin.
Data on electron transfer at low temperatures and under different redox conditions are analyzed. along with the ps fluorescence kinetics. The hypothesis is discussed that electron transfer in RC's is coupled to conformation changes in the interacting molecules.     

Static and dynamic behavior of 2:1 inclusion complexes of cyclodextrins and charged porphyrins in aqueous organic media

Two heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TMe-beta-CD) molecules strongly include the peripheral substituents at the 5- and 15-positions of the charged meso-tetrasubstituted porphyrins, PorSub(4) [TPPS(4) (Sub = p-C(6)H(4)-SO(3)(-)), TPPOC3PS (p-C(6)H(4)-O-(CH(2))(3)-p-C(6)H(4)-SO(3)(-)), TCPP (Sub = p-C(6)H(4)-CO(2)(-)), and TPPOC3Py (p-C(6)H(4)-O-(CH(2))(3)-Py(+)Br(-)), where Py(+) = N-alkylpyridinium] in aqueous ethylene glycol. The binding constants (K(1) and K(2)) and the rate constants (k(1) and k(2)) for formation of the 1:1 and 2:1 complexes of TMe-beta-CD and PorSub(4) were determined. Both the binding constants and the rate constants for anionic TPPS(4), TCPP, and TPPOC3PS were much larger than those for cationic TPPOC3Py. The smaller k(1) and k(2) values for TPPOC3Py indicate a higher barrier for penetration of a cationic guest into the TMe-beta-CD cavity. The methyl groups at the rims and the cavity wall of the host are positively polarized due to the inductive effect of the ethereal oxygens. The positively polarized rims and interior of the host cavity should prevent the penetration of the cationic substituent of TPPOC3Py into the TMe-beta-CD cavity. The 2:1 TMe-beta-CD-PorSub(4) complexes are extraordinary stable in aqueous solutions, even in the case of cationic TPPOC3Py. Formation of both 1:1 and 2:1 complexes is promoted by negative and large enthalpy changes, suggesting a strong van der Waals interaction as the main binding force.     

The first example of a seven-coordinate vanadium(III) thiolate complex containing the hydrazine molecule, an intermediate of nitrogen fixation

The first example of a seven-coordinate vanadium(III) thiolate complex, [V(PS3' ')(N(2)H(4))(3)] (1), where PS3' ' = [P(C(6)H(3)-3-Me(3)Si-2-S)(3)](3)(-), has been synthesized and characterized. Compound 1 contains a tetradentate ligand (PS3' ') and three hydrazine molecules, forming a capped octahedral geometry. A five-coordinate vanadium(III) complex, [V(PS3)(1-Me-Im)] (2), where PS3 = [P(C(6)H(4)-2-S)(3)](3)(-) and 1-Me-Im = 1-methyl-imidazole, was also obtained. Compound 2 adopts a trigonal bipyramidal geometry, in which the vanadium is ligated by the title ligand, PS3, and one 1-Me-Im molecule.     

Direct Metallization of Gold Nanoparticles on a Polystyrene Bead Surface using Cationic Gold Ligands

Gold nanoparticles are formed to cover the surface of sulfonated‐polystyrene (PS) beads by the in‐situ ion‐exchange and chemical reduction of a stable cationic gold ligand, which makes it different from the physical adsorption or multiple electroless metallization methods. PS beads are synthesized by dispersion polymerization with a diameter of 2.7 µm, and their surface is modified by introducing sulfonic acid groups (SO) to give an ion exchange capacity of up to 2.25 mequiv. · g⁻¹, which provides 1.289 × 10¹⁰ SO per bead. Subsequently, the anionic surface of the PS beads is incorporated with a cationic gold ligand, dichlorophenanthrolinegold(III) chloride ([AuCl₂(phen)]Cl), through an electrostatic interaction in the liquid phase to give gold nanoparticles (ca. 1–4 nm in diameter) formed on the PS surface. Assuming that approximately three SO groups interact with one [AuCl₂(phen)]⁺ ion in the ion‐exchange process, the gold coverage on a PS bead is estimated as 12.0 wt.‐%, which compares well with the 16.8 wt.‐% of gold loading measured by inductively coupled plasma–mass spectrometry. Because of the adjustable IEC values of the polymer surface and the in‐situ metallization of Au in the presence of S atoms, both of which are of a soft nature, the developed methodology could provide a simple and controllable route to synthesize a robust metal coating on the polymer bead surface.

     

Charge transport anisotropy in n-type disk-shaped triphenylene-tris(aroyleneimidazole)s

Two novel n-type disk-shaped molecules containing a triphenylene core and three fused naphthaleneimide imidazole or peryleneimide imidazole "arms" are synthesized and characterized. The n-type charge carrier mobilities of these molecules are evaluated by both field effect transistors and space-charge limited-current measurements, which exhibit drastically different mobility anisotropy. A strong correlation between film morphology and the charge transport behavior is established by X-ray scattering and atomic force microscopic analyses.     

Synthesis of Dibenzothiophenes by Pd‐Catalyzed Dual CH Activation from Diaryl Sulfides

Palladium‐catalyzed dual C?H functionalization of diaryl sulfides to form dibenzothiophenes (DBTs) by oxidative dehydrogenative cyclization is reported. This protocol afforded various DBTs in moderate to good yields with tolerance of a wide variety of substrates. Benzo[1,2‐b:4,5‐b′]bis[b]benzothiophene was successfully synthesized by this method, which was used as an organic semiconductor for field‐effect transistors.     

Synthesis and Characterization of Hexathiophenes with Methylthienyl Side Chains

Summary: Two novel conjugated isomeric hexathiophenes 6T1 and 6T2 bearing 5-methyl-2-thienyl substituents have been synthesized by Suzuki coupling and oxidative dimerization method. These isomers were characterized by ¹H NMR, ¹³C NMR, elemental and mass analysis. The two hexamers show good solubility in common solvents and show almost identical UV-vis absorption spectra in solution with a maximum cantered at 387 nm. These materials bearing thienyl substituents in the sidechain are anticipated to provide better charge transport in devices and hold promise for use in organic field effect transistors.     

Conformation Diversity of a Fused‐Ring Pyrazine Derivative on Au(111) and Highly Ordered Pyrolytic Graphite

Heterocyclic aromatic compounds have attracted considerable attention because of their high carrier mobility that can be exploited in organic field‐effect transistors. This contribution presents a comparative study of the packing structure of 3,6‐didodecyl‐12‐(3,6‐didodecylphenanthro[9,10‐b]phenazin‐13‐yl)phenanthro[9,10‐b]phenazine (DP), an N‐heterocyclic aromatic compound, on Au(111) and highly ordered pyrolytic graphite (HOPG). High‐resolution scanning tunneling microscopy (STM) combined with atomistic simulations provide a picture of the interface of this organic semiconductor on an electrode that can have an impact on the field‐effect transistor (FET) performance. DP molecules adsorb with different conformational isomers (R/S: trans isomers; C: cis isomer) on HOPG and Au(111) substrates. All three isomers are found in the long‐range disordered lamella domains on Au(111). In contrast, only the R/S trans isomers self‐assemble into stable chiral domains on the HOPG surface. The substrate‐dependent adsorption configuration selectivity is supported by theoretical calculations. The van der Waals interaction between the molecules and the substrate dominates the adsorption binding energy of the DP molecules on the solid surface. The results provide molecular evidence of the interface structures of organic semiconductors on electrode surfaces.     

The induced magnetic field in cyclic molecules

The response of a molecule to an applied external magnetic field can be evaluated by a graphical representation of the induced magnetic field. We have applied this technique to four representative, cyclic organic molecules, that is, to aromatic (C(6)H(6), D(6h)), anti-aromatic (C(4)H(4), D(2h)) and non-aromatic (C(4)H(8), D(4h), and C(6)H(12), D(3d)) molecules. The results show that molecules that contain a pi system possess a long-range magnetic response, while the induced magnetic field is short-range for molecules without pi systems. The induced magnetic field of aromatic molecules shields the external field. In contrast, the anti-aromatic molecules increase the applied field inside the ring. Aromatic, anti-aromatic, and non-aromatic molecules can be characterized by the appearance of the magnetic response. We also show that the magnetic response is directly connected to nucleus-independent chemical shifts (NICS).     

Preparation and properties of the full series of cuboidal clusters [Mo(x)W4-xSe4(H2O)12]n+ (n = 4-6) and their derivatives

Hydrothermal reactions between incomplete cuboidal cluster aqua complexes [M3Q4(H2O)9]4+ and M(CO)6 (M = Mo, W; Q = S, Se) offer easy access to the corresponding cuboidal clusters M4Q4. The complete series of homometal and mixed Mo/W clusters [Mo(x)W4-xQ4(H2O)12]n+ (x = 0-4, n = 4-6) has been prepared. Upon oxidation of the mixed-metal clusters, it is the W atom which is lost, allowing selective preparation of new trinuclear clusters [Mo2WSe4(H2O)9]4+ and [MoW2Se4(H2O)9]4+. The aqua complexes were converted by ligand exchange reactions into dithiophosphato and thiocyanato complexes, and crystal structures of [W4S4((EtO)2PS2)6], [MoW3S4((EtO)2PS2)6], [Mo4Se4((EtO)2PS2)6], [W4Se4((i-PrO)2PS2)6], and (NH4)6[W4Se4(NCS)12]-4H20 were determined. Cyclic voltammetry was performed on [Mo(x)W4-xCO4(H2O)12]n+, showing reversible redox waves 6+/5+ and 5+/4+. The lower oxidation states are more difficult to access as the number of W atoms increases. The [Mo2WSe4(H2O)9]4+ and [MoW2Se4(H2O)9]4+ species were derivatized into [Mo2WSe4(acac)3(py)3]+ and [MoW2Se4(acac)3(py)3]+, which were also studied by CV. When appropriate, the products were also characterized by FAB-MS and NMR (31P, 1H) data.     

Photoresponsive n-channel organic field-effect transistors based on a tri-component active layer

Photoresponsive OFETs were fabricated based on a tri-component active layer (NDI2OD-DTYM2, spiropyran and polystyrene). The results demonstrated that these OFETs displayed photoresponsive feature to alternate UV and vis light due to the photoisomerization of spiropyran between the closed-ring state and ionic open-ring state.