(E)-4,4'-Bis[bis(4-methoxyphenyl)amino]stilbene, 1, (E,E)-1,4-bis[4-[bis(4-methoxyphenyl)amino]styryl]benzene, 2, and two longer homologues, (E,E,E)-4,4'-bis[4-[bis(4-methoxyphenyl)amino]styryl]stilbene, 3, and (E,E,E,E)-1,4-bis(4-[4-[bis(4-methoxyphenyl)amino]styryl]styryl)benzene, 4, have been oxidized to their mono- and dications using tris(4-bromophenyl)aminium hexachloroantimonate. The intervalence charge-transfer (IVCT) band of 1(+) is narrow and asymmetric and exhibits only weak solvatochromism. Analysis of this band indicates that 1(+) is a class-III or class-II/III borderline mixed-valence species. In contrast, a broad, strongly solvatochromic IVCT band is observed for 2(+), indicating that this species is a class-II mixed-valence species. The assignment of 1(+ ) and 2(+) as symmetric class-III and unsymmetric class-II species, respectively, is also supported by AM1 calculations. Hush analysis of the IVCT bands of both 1(+) and 2(+) gives larger electronic couplings, V, than for their analogues in which the double bonds are replaced with triple bonds. The diabatic electron-transfer distance, R, in 1(+) can be estimated by comparison of the V estimated by Hush analysis and from the IVCT maximum; it is considerably less than the geometric N-N separation, a result supported by quantum-chemical estimates of R for 1(+)-4(+). In 3(+) and 4(+), the IVCT is largely obscured by an intense absorption similar to a band seen in the corresponding dications and to that observed in the monocation of a model compound, (E,E,E)-1-[bis(4-methoxyphenyl)amino]-4-[4-[4-(4-tert-butylstyryl)styryl]styryl]benzene, 5, containing only one nitrogen redox center; we attribute this band to a bridge-to-N(+) transition. The corresponding dications 1(2+)-4(2+) show a complementary trend in the coupling between redox centers: the shortest species is diamagnetic, while the dication with the longest bridge behaves as two essentially noninteracting radical centers.

Anthryl‐alkyl‐PA (π‐σ‐PA) self‐assembled monolayers (SAMs)/hafnium oxide (HfO2) hybrid dielectrics have been integrated into organic thin film transistors (OTFTs) to achieve operating voltages under −1.5 V. Using π‐σ‐PA SAMs on sol–gel processed HfO2, pentacene‐based OTFTs possess low subthreshold slopes (100 mV dec−1), high on–off current ratios (105–106), and hole mobilities as high as 0.22 cm2 V−1 s−1.

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The E-4,4'-bis[di(p-anisyl)amino]stilbene cation is a class-III mixed-valence species with electronic coupling comparable to that in its biphenyl-bridged analogue, whereas its tolane-bridged analogue belongs to class II.

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Two series of highly efficient and thermally stable nonlinear optical chromophores based on the (4diarylamino)phenyl electron donors have been synthesized and systematically investigated. A modular approach has been employed to synthesize these electron donors with tunable size, shape, and electrondonating abilities. Efficient conjugated bridges were extended from these donors and coupled with very strong CF 3 -TCF electron acceptors to afford chromophores with very high β values (up to 7077 × 10 -30 esu at 1.907 µm). These chromophores possess much higher thermal stability (with their onset decomposition temperatures all above 220 °C) than those substituted with (4-dialkylamino)phenyl donors. Most importantly, the high molecular hyperpolarizability of these chromophores can be effectively translated into very large electro-optic (E-O) coefficients (r 33 ) in poled polymers through suitable shape engineering. Exemplified by the chromophore B4, which has a fluorinated aromatic substituent anchored at its donor end, it showed a very large r 33 (169 pm/V) at 1.31 µm. This value is almost 1 order higher than the E-O activities usually reported for (4-diarylamino)phenyl-substituted NLO chromophores.

Pentacene-based organic thin-film transistors (OTFTs) have been fabricated using π-σ-phosphonic acid self-assembled monolayers (SAMs) on top of aluminum oxide as the gate dielectrics. With ultrathin dielectrics, high capacitances up to 760nF∕cm2 and low leakage current densities of 10−8A∕cm2 at 2V could be obtained, allowing operation of OTFTs within −3V. Vast improvements in the gate leakage current (∼2 orders), on/off current ratio (1 order), and subthreshold slope down to 85mV∕decade are achieved compared to control devices without SAMs. The OTFTs with pentacene vapor deposited at room temperature on SAM dielectrics-modified substrates exhibit mobilities of 0.14–0.30cm2∕Vs, on/off current ratios of 105, and threshold voltages of −(1.3–1.5)V.

Poled electro-optic (EO) polymers have enabled many advances in the exploration of high-speed and broadband information technologies.[1] Polymer based EO devices have been demonstrated to have large bandwidths (over 110 GHz), low driving voltages, and sustain their performance in a flexible form [2] or under extreme environmental conditions. [3,4] For optical circuits, EO polymers can be easily integrated with stripline-or ring-structured waveguides made of sol-gels, [5] low-loss fluorinated polymers, [6] silicon slots, [7] conducting oxides, [8] and photonic crystals. [9] Recently, EO polymers have also been utilized for the generation/detection of a gap-free pulsed THz system with a bandwidth up to ca. 12 THz.[10]Large numbers of discrete photonic components need to be inserted into integrated systems of telecommunication and silicon microphotonics, especially where an extreme amount of data is required to travel in a very small space.[11] Therein lies the great challenge for polymer-based EO technologies: to have thermally stable EO coefficients (r 33 ) of around 500 pm V -1 at wavelengths of 1.31 or 1.55 lm.[11b]Currently, the most commonly used materials for polymeric EO devices are based on poled polymers with r 33 values around 50-80 pm V -1 at wavelengths of 1.31 or 1.55 lm. In these materials, dipolar nonlinear optical (NLO) chromophores have been doped or incorporated at a level of ca. 20-25 wt % to reach their maximum r 33 values. [5][6][7][8][9][10] Beyond such a moderate loading of chromophores, strong intermolecular electrostatic interactions severely limit the poling-induced polar order and cause phase-separation problems between chromophores and polymers.To further improve EO activity, research efforts have focused on developing shape-engineered chromophores with high molecular optical nonlinearities (lb), [12] where lb is a product of first hyperpolarizability and the dipole moment of the NLO chromophore, and increasing order within the matrices by controlling the nanoscale architecture of macromolecules. [13] In our recent study we have demonstrated, using Diels-Alder (DA) "click chemistry" to post-functionalize NLO chromophores onto polymers, that high chromophore loading levels (up to 35 wt %) and large r 33 values (up to 110 pm V -1 ) could be achieved in in situ generated side-chain dendronized NLO polymers with non-reacted chromophores as guest dopants. [14] This opens a new avenue to explore optimal host-guest combinations and to develop an efficient way to control lattice hardening in these hybrid polymers. The ultimate goal is to simultaneously achieve very large EO activity, good thermal stability, high optical transparency, and excellent mechanical properties within the same material via molecular design and facile processing. In this paper, we report a novel method to disperse a highly efficient secondary chromophore into in situ crosslinked NLO polymer networks, leading to both enhanced EO activity (> 260 pm V -1 at 1.31 lm) and alignment stability at 85°C. In photorefractive (PR) po...