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Acta crystallographica / Section D 78(3), 310 - 320 (2022). doi:10.1107/S2059798322000432, InlB, a bacterial agonist of the human receptor tyrosine kinase MET, consists of an N-terminal internalin domain, a central B repeat and three C-terminal GW domains. In all previous structures of full-length InlB or an InlB construct lacking the GW domains (InlB$_{392}$), there was no interpretable electron density for the B repeat. Here, three InlB$_{392}$ crystal structures in which the B repeat is resolved are described. These are the first structures to reveal the relative orientation of the internalin domain and the B repeat. A wild-type structure and two structures of the T332E variant together contain five crystallographically independent molecules. Surprisingly, the threonine-to-glutamate substitution in the B repeat substantially improved the crystallization propensity and crystal quality of the T332E variant. The internalin domain and B repeat are quite rigid internally, but are flexibly linked to each other. The new structures show that inter-domain flexibility is the most likely cause of the missing electron density for the B repeat in previous InlB structures. A potential binding groove between B-repeat strand β2 and an adjacent loop forms an important crystal contact in all five crystallographically independent chains. This region may represent a hydrophobic `sticky patch' that supports protein–protein interactions. This assumption agrees with the previous finding that all known inactivating point mutations in the B repeat lie within strand β2. The groove formed by strand β2 and the adjacent loop may thus represent a functionally important protein–protein interaction site in the B repeat., Published by Wiley, Bognor Regis

Advantages like environmentally friendly operation and relatively low maintenance costs of vacuum circuit breakers (VCB) in comparison to other interrupters have established the VCB in the medium voltage range. In order to enlarge the operational voltage level, a common approach is the usage of a double break. One possible solution for the symmetrisation of the voltage distribution over the series gaps is the use of external grading capacitors. In this paper a double breaking vacuum chamber with additional field grading and shielding electrodes, in a separate surrounding vacuum chamber to symmetrize the voltage distribution, is presented. In the first step, the shielding behaviour of the arrangement is analysed. Therefore, a grounded surrounding electrode is used to disturb the symmetric field distribution over the arrangement. In a second step the dielectric behaviour in dependence of the shield preparation before and during conditioning is investigated. Complete breakdowns of the arrangement are detected by using a common voltage divider. To detect partial breakdowns, the shields own capacitances are determined and used to generate a voltage divider. This approach also allows the estimation of the floating middle potential. All tests were performed with lightning impulse voltage stress (LIV). The paper presents a dielectric strength evaluation for vacuum double break arrangements and a test procedure to detect partial breakdowns inside.

This paper proposes a combined day-ahead forecasting and scheduling energy management system (EMS) with multiple complimentary objectives on household level. Our comparative case study, analyses, economical, ecological and grid independence aspects of our model include the utilization of renewable energy source (RES) with a controllable diesel generator and an energy storage system (ESS). The latter includes both stationary and electric vehicle batteries. The forecasting of RES and uncontrollable load of a single household is based on an LSTM approach, which is then used for day-ahead electricity scheduling. In order to be consistent with the forecasting horizon, day-ahead wholesale electricity market prices are used.

MET, the product of the c-MET proto-oncogene, and its ligand hepatocyte growth factor/scatter factor (HGF/SF) control survival, proliferation and migration during development and tissue regeneration. HGF/SF-MET signaling is equally crucial for growth and metastasis of a variety of human tumors but resistance to small-molecule inhibitors of MET kinase develops rapidly and therapeutic antibody targeting remains challenging. We made use of the designed ankyrin repeat protein (DARPin) technology to develop an alternative approach for inhibiting MET. We generated a collection of MET-binding DARPins covering epitopes in the extracellular MET domains and created comprehensive sets of bi-paratopic fusion proteins. This new class of molecules efficiently inhibited MET kinase activity and downstream signaling, caused receptor downregulation and strongly inhibited the proliferation of MET-dependent gastric carcinoma cells carrying MET locus amplifications. MET-specific bi-paratopic DARPins may represent a novel and potent strategy for therapeutic targeting of MET and other receptors, and this study has elucidated their mode of action. Copyright © 2019. Published by Elsevier Ltd.

The health and life span of Drosophila melanogaster are partly determined by intestinal barrier integrity, metabolic rate as well as stress response and the expression of longevity-associated genes, depending on genetic and dietary factors. Ursolic acid (UA) is a naturally occurring triterpenoid exhibiting potential antimicrobial, anti-inflammatory, and antiobesity activity and counteracting age-related deficits in muscle strength. In this study, UA was dietarily administered to w1118 D. melanogaster which significantly elongated the health and life span of males. Spargel (srl) is the Drosophila orthologue of mammalian peroxisome proliferator-activated receptor-gamma coactivator 1 α(PGC1α), an important regulator of energy homeostasis and mitochondrial function. Our results indicate that the health-promoting effect of UA, demonstrated by a significant increase in climbing activity, occurs via an upregulation of srl expression leading to a metabolic shift in the fly without reducing fecundity or gut integrity. Moreover, UA affected the flies' microbiota in a manner that contributed to life span extension. Srl expression and microbiota both seem to be affected by UA, as we determined by using srl-mutant and axenic flies. © 2018 BioFactors, 45(2):169-186, 2019.

The human MET receptor tyrosine kinase contributes to vertebrate development and cell proliferation. As a proto-oncogene, it is a target in cancer therapies. MET is also relevant for bacterial infection by Listeria monocytogenes and is activated by the bacterial protein internalin B. The processes of ligand binding, receptor activation, and the diffusion behavior of MET within the plasma membrane as well as its interconnections with various cell components are not fully understood. We investigated the receptor diffusion dynamics using single-particle tracking and imaging fluorescence correlation spectroscopy and elucidated mobility states of resting and internalin B-bound MET. We show that internalin B-bound MET exhibits lower diffusion coefficients and diffuses in a more confined area in the membrane. We report that the fraction of immobile receptors is larger for internalin B-bound receptors than for resting MET. Results of single-particle tracking in cells treated with various cytotoxins depleting cholesterol from the membrane and disrupting the actin cytoskeleton and microtubules suggest that cholesterol and actin influence MET diffusion dynamics, while microtubules do not have any effect.

We investigate the scale-free property of an agent-based macroeconomic model initially proposed by Wright (Physica A, 346:589–620, 2005), called the Social Architecture (SA) model. The SA model has been shown to be able to replicate a number of important features of a macroeconomy, such as patterns concerning economic growth, business cycles, industrial dynamics, and income distribution. We explore whether macroeconomic stylized features resulting from this model are robust when the number of agents populating the (model) economy varies. We simulate the model by systematically varying the agent population with 100, 500, 1,000, 2,000, 4,000, 8,000, and 10,000 agents. Our results indicate that the SA model does exhibit significant size effects for several important variables.

We report on bulk structures of a family of quaterthiophene (4T) derivatives with linear and branched end groups such as α,α′-dihexylquaterthiophene (Hex-4T-Hex), α,α′-didecyl-quaterthiophene (Dec-4T-Dec) and α,α′-bis(2-ethylhexyl)quaterthiophene (EH-4T-EH), tetramethyldisiloxane-based dimers D2-Und-4T-EH and D2-Und-4T-Hex, and carbosilane-siloxane-based tetramers D4-Und-4T-EH and D4-Und-4T-Hex. The dimers and tetramers contain undecylenic (Und) spacers between the disiloxane and 4T- units of the molecule. The impact of the molecular architecture on the bulk structure at different temperatures is addressed with X-ray diffraction and differential scanning calorimetry. For all of the studied quaterthiophene-containing organosilicon multipods the formation of 4T-crystal sublattice is observed. The alkyl periphery plays an important role in the molecular packing and thermal stability of the ordered phase. They can stabilize or destabilize the crystal phase, depending on their length and architecture. The quat...

We investigated two different (2,7-dialkyl-[1]benzothieno[3,2-b][1]benzothiophenes; C(n)-BTBT-C(n), where n = 12 or 13) semiconductors in low-voltage operating thin-film transistors. By choosing functional molecules in nanoscaled hybrid dielectric layers, we were able to tune the surface energy and improve device characteristics, such as leakage current and hysteresis. The dipolar nature of the self-assembled molecules led to a shift in the threshold voltage. All devices exhibited high charge carrier mobilities of 0.6-7.0 cm(2) V(-1) s(-1). The thin-film morphology of BTBT was studied by means of atomic force microscopy (AFM), presented a dependency upon the surface energy of the self-assembled monolayer (SAM) hybrid dielectrics but not upon the device performance. The use of C(13)-BTBT-C(13) on hybrid dielectrics of AlO(x) and a F(15)C(18)-phosphonic acid monolayer led to devices with a hole mobility of 1.9 cm(2) V(-1) s(-1) at 3 V, on/off ratio of 10(5), small device-device variation of mobility, and a threshold voltage of only -0.9 V, thus providing excellent characteristics for further integration.

The preparation and characterization of novel electron donor compounds with two (D1) and four (D2) quaterthiophene-containing arms attached to the flexible carbosilane–siloxane core are described. These materials were investigated in organic field effect transistors and photovoltaic cells. A power conversion efficiency of ∼0.9% obtained for D1:[70]PCBM blends is one of the highest values achieved up to now for solution-processible small molecular bulk heterojunction solar cells with large band-gap oligothiophene-based donor materials comprising no other chromophore units.

The one-photon and two-photon absorption properties of cross-shaped chromophores consisting of four donor-substituted styryl branches linked to an aromatic core (benzene or pyrazine) have been investigated and compared with those of linear analogues with only two branches (donor−π−donor distryrylarenes). The areas of the lowest energy two-photon absorption bands of the compounds with four branches were less than twice those of analogues with two branches. The spectral features observed in these chromophores suggest that electronic coupling between the branches is effective but does not lead to significant enhancement of the two-photon cross section when the branches extend in more than one dimension. In a chromophore with two donor-substituted and two acceptor-substituted branches the two-photon cross section is smaller than in the corresponding linear analogues. The main characteristics of both the one-photon and two-photon spectra of multibranched compounds of the type discussed here can be explained qu...

The dinuclear dipolar borabenzene complexes [(η5-C5H5)Fe{μ-(η5-C5H4)C2(η6-BC5H5)}ML]X [ML = Ru(η6-C6H6), X = Cl (4aCl), PF6 (4aPF6), B(C6H5)4 (4aBPh4); ML = Rh(η5-C5Me5), X = Cl (4bCl), PF6 (4bPF6); ML = Ir(η5-C5Me5), X = Cl (4cCl), PF6 (4cPF6)] were synthesized by a nucleophilic substitution reaction of the trimethylphosphane adduct of borabenzene (1) with lithium ferrocenylacetylide, subsequent lithium-thallium exchange and coordination of the appropriate ML unit obtained from [Ru(η6-C6H6)Cl(μ-Cl)]2, [M(η5-C5Me5)Cl(μ-Cl)]2 (M = Rh, Ir); the formed chloride salts, which are soluble in water, were transformed to the PF6 salts by adding [NH4][PF6] to the corresponding water solution. BPh4 salts can be produced, when a methanolic solution of Na[BPh4] were added to CH2Cl2-solutions of the appropriate PF6 salt. X-ray structure analyses of single crystals of 4aBPh4 and 4bPF6 were successful, illustrating the cation 4a+ in an ideal cis-conformation, whereas 4b+ displays a cis- and trans-conformation. Spectroscopic and cyclic voltammetry studies reveal a small but distinct donor-acceptor interaction between the ferrocenyl donor and the cationic borabenzene complex acceptor which increases in the order 4aPF6 < 4cPF6 < 4bPF6. The nonlinear optical properties of these donor-acceptor complexes were studied by means of hyper-Rayleigh scattering (HRS), resulting in the determination of small values for the first hyperpolarisability s, which increase in the same order as the donor-acceptor interaction. Kationische Borabenzol-Komplexe als Elektronenakzeptor-Gruppen fur molekulare Materialien mit nichtlinearoptischen Eigenschaften Der Weg zur Darstellung der zweikernigen, dipolaren Borabenzolkomplexe [(η5-C5H5)Fe{μ-(η5-C5H4)C2(η6-BC5H5)}ML]X [ML = Ru(η6-C6H6), X = Cl (4aCl), PF6 (4aPF6), B(C6H5)4 (4aBPh4); ML = Rh(η5-C5Me5), X = Cl (4bCl), PF6 (4bPF6); ML = Ir(η5-C5Me5), X = Cl (4cCl), PF6 (4cPF6)] fuhrte uber die nucleophile Substitutionsreaktion am Trimethylphosphanaddukt von Borabenzol (1) mit Lithiumferrocenylacetylid; das entstandene Lithiumsalz des ferrocenylethinylsubstituierten Boratabenzols (2) wurde zunachst einer Li/Tl-Austauschreaktion unterworfen und zur Koordination an ML-Einheiten anschliesend mit [Ru(η6-C6H6)Cl(μ-Cl)]2, [M(η5-C5Me5)Cl(μ-Cl)]2 (M = Rh, Ir) umgesetzt. Die entstandenen Cl-Salze sind wasserloslich und lassen sich durch Zugabe von [NH4][PF6] zu wassrigen Losungen der Chloride in die PF6-Salze uberfuhren. BPh4-Salze konnen hergestellt werden, indem methanolische Losungen von Na[BPh4] zu CH2Cl2-Losungen der entsprechenden PF6-Salze gegeben werden. Einkristallstrukturanalysen von 4aBPh4 und 4bPF6 waren erfolgreich. Sie ergeben fur das Kation 4a+ eine ideale cis-Konformation, wahrend fur 4b+ eine cis- und trans-Konformation gefunden wird. Spektroskopische und cyclovoltammetrische Studien zeigen eine geringe aber merkliche Donor-Akzeptor-Wechselwirkung zwischen dem Ferrocenyldonor und dem kationischen Borabenzolkomplex-Akzeptor, die in der Reihenfolge 4aPF6 < 4cPF6< 4bPF6 ansteigt. Die nichtlinear optischen Eigenschaften dieser Donor-Akzeptorkomplexe wurden mit Hilfe der hyper-Rayleigh-Streuungsmethode (HRS) untersucht. Danach konnten fur die erste Hyperpolarisierbarkeit s relativ kleine Werte bestimmt werden, die in der gleichen Reihenfolge wie die Donor-Akzeptor-Wechselwirkung ansteigen.

The donor-acceptor complexes with a vinylogue monohydro sesquifulvalene and sesquifulvalene backbone of the type [(η5-C5H5)Ru{µ-(η5-C5H4)C2H2(η6-C7H7)}ML](PF6)n [n = 0: ML = none (1), Cr(CO)3 (2); n = 1: ML = Ru(η5-C5H5) (3a), Ru(η5-C5Me5) (3b)] and [(η5-C5H5)Ru{µ-(η5-C5H4)C2H2(η7-C7H6)}ML](PF6)n [n = 1: ML = none (4), Cr(CO)3 (5); n = 2: ML = Ru(η5-C5H5) (6a), Ru(η5-C5Me5) (6b)], respectively, have been synthesised, and spectroscopically and structurally characterised. A charge-shift correlation was carried out by means of 1H NMR spectroscopic studies and an increased ground-state donor-acceptor interaction in the order 5 < 6b < 4 < 6a was found. The corresponding donor-acceptor interaction in 3a and 3b varies by an insignificant amount. Hyper-Rayleigh scattering (HRS) was applied to determine the first hyperpolarisability β of the mono- and dicationic complexes 3a−6b. The β values obtained for the cationic sesquifulvalene complexes 4−6b are among the largest ever measured for ruthenocenyl containing complexes due to a strong resonance enhancement: the sesquifulvalene complexes 4−6a, 6b show first hyperpolarisabilities which range between 360 and 700 × 10−30 esu, whereas β for the monohydrosesquifulvalene complexes are considerably lower (75 and 162 × 10−30 esu). For the latter complexes the first hyperpolarisability doubles on going from Ru(η5-C5Me5) (3b) to Ru(η5-C5H5) (3a) in the acceptor unit. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Three different {η5-(+)-neomenthylcyclopentadienyl}ruthenium complexes have been synthesized from (−)-menthol: [(η6-benzene){η5-(+)-neomenthylcyclopentadienyl}ruthenium(II)] hexafluorophosphate (1), [tris(acetonitrile){η5-(+)-neomenthylcyclopentadienyl}ruthenium(II)] hexafluorophosphate (2) and [(η6-cyclooctatetraene){η5-(+)-neomenthylcyclopentadienyl}ruthenium(II)] hexafluorophosphate (3). X-ray structural determination (space group P212121) and NMR spectroscopic studies of 3 show it exists as a single stereoisomer in both the solid and solution phase, with [α]20D = +92.5. The chiral modification of the Cp ligand induces anisochrony for all of the magnetically active nuclei of the unsubstituted COT ligand. (© Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2003)

The potent electron-donating group [(CpFeCO)2(µ-CO)(µ-C=CH−)] was combined with different tropylium-based acceptors yielding the push-pull complexes [(CpFeCO)2(µ-CO)(µ-C=CH−CH=A)][BF4] where =A represents [=CH−(η7-C7H6)Cr(CO)3]+ (5), [={C10H7}]+ (azulenylium) (7) [={C10H4Me2iPr}]+ (guaiazulenylium) (8). Crystal structures of the precursor complexes [(CpFeCO)2(µ-CO)(µ-C=CH−CH=CH−C7H7)] (3), [(CpFeCO)2(µ-CO){µ-C=CH−CH=CH−(η6-C7H7)Cr(CO)3}] (4) and the push-pull derivative 5 are presented. Whereas complexes 3 and 4 demonstrate localised carbon−carbon double and single bonds in the π-bridge between the diiron moiety and the seven-membered ring a small but distinct π-bond delocalisation can be observed in the π-linker of the cationic derivative 5. From the NMR spectroscopic results a correlation between the 13C NMR shift of the bridging carbon atom µ-C of the diiron unit and the coupling constant J(1H-1H) of the β- and γ-protons of the π-bridge was found. This correlation indicates an increased π-bond delocalisation throughout the conjugated bridge with respect to the electron-accepting capability in the order tricarbonyl(η7-cycloheptatrienylium)chromium < guaiazulenylium < azulenylium implying a predominantly charge-delocalised form in the case of the azulenylium complex 7. Considerably large first hyperpolarisabilities β were determined for 5 and 8 by means of hyper-Rayleigh scattering. Based on the two-level model β0 values were calculated and related to the bond-length alternation in the π-linker. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

In order to gain a deeper insight into structure-property relationships of the donor (D)−acceptor (A) interactions in cationic sesquifulvalene complexes the mono- and dicationic complexes [(η5-C5H5)Fe{µ-(η5-C5H4)(η7-C7H6)}M′L′]+ were synthesized as BF4 and PF6 salts: M′L′ = Cr(CO)3 (3PF6); M′L′ = none (4BF4); M′L′ = Ru(η5-C5H5)+ [5(PF6)2]; M′L′ = Ru(η5-C5Me5)+ [6(PF6)2]. The ferrocenyl substituent works as the electron donor and the tropylium moiety as the electron acceptor. For the electronic ground state the NMR spectroscopic results demonstrate an increasing charge delocalization in the order M′L′ = Cr(CO)3 < Ru(η5-C5Me5)+ < Ru(η5-C5H5) < none. The same order of the acceptor moieties is observed for the difference between the oxidation and reduction potentials, which are related to an electrochemically reversible and a complete irreversible one-electron transfer, respectively. A comparison of the structural data of 3−6 reveals a small but distinct contribution of the cross-conjugated mesomeric form to the bis(aromatic) mesomeric form in the ground state of the sesquifulvalene complexes, which increases, when the electron-withdrawing ability of the acceptor becomes stronger. The UV/Vis spectra are dominated by two intense absorption bands in the visible and near-UV region, which are assigned to a low-energy donor(metal)−acceptor charge-transfer (D−A CT) transition and to a high-energy donor(ligand)−acceptor charge-transfer (L−A CT) transition. For these archetype sesquifulvalene complexes the first hyperpolarizability β was determined by means of hyper-Rayleigh scattering (HRS). Whereas for 3 no second harmonic signal could be detected and 4 shows fluorescence due to two-photon absorptions, 5 and 6 possess appreciable β values.

In order to investigate the structure−property relationship of nonlinear optical materials, a series of organometallic chromophores were synthesised utilising the [Fe2(η-C5H5)2(CO)2(μ-CO)(μ-C−)]+ electron-accepting moiety and the ferrocenyl group, Fc, as the electron donor. The π-linker between these two termini was systematically modified and the mutual electronic communication between them was determined using IR, NMR, and electronic absorption spectroscopy. An X-ray structure determination of [Fe2(η-C5H5)2(CO)2(μ-CO)(μ-C−CH=CH−CH=C(Cl)−Fc)][BF4] confirmed the strong electronic interaction between the donor and the acceptor with reduced π-bridge bond-length alternation. The nonlinear optical properties of these complexes were examined using the hyper Rayleigh scattering technique. The experimental first hyperpolarisabilities are some of the highest obtained for ferrocenyl chromophores and, significantly, no enhancement was found due to two-photon absorption fluorescence. When polyene linkers −(CH=CH)n− are used, the values for β0 increase with a ca. n1.5 dependence with no sign of saturation up to n = 4. However, the highest values for β and βo were obtained for linkers which contained an aromatic ring as opposed to pure polyenes and in this respect a benzene ring was more effective than a thiophene or furan. Consequently, the higher β and β0 are not exhibited by those merocyanines with the highest values for λmax. It is concluded for these compounds that a low excitation energy Eeg and a large transition moment M for the electronic excitation are less important than a large change in the dipole moment Δµeg. Furthermore, a chloro substituent on the olefinic double bond proximate to the ferrocenyl group has a dramatic effect on the β and β0 values.

The synthesis is reported of a series of extended π-bridged organometallic merocyanines linking the dicyanovinyl electron accepting group with the electron donating [(CpFeCO) 2 (μ-CO)(μ-CCH)] fragment. The chromophores exhibited inverse solvatochromic shifts with increased medium polarity, which is because of interactions between dipolar or protic solvents and the dicyanovinyl unit. The nonlinear optical (NLO) properties of the chromophores have been investigated using long wavelength (1500 nm) hyper-Rayleigh scattering techniques to avoid both resonance and two-photon absorption enhancement of the first hyperpolarisabilities.

The novel series of monometallic monocations Fc-[n]-Az+ and Fc-[n]-Guaz+ (where Az+ and Guaz+ denote azulenylium and guaiazulenylium cations respectively and n = 0–3), and a bimetallic dicationic complex Fc-[0]-Guaz(RuCp)2+ have been prepared. Single crystal structures of Fc-[0]-Guaz+ and Fc-[0]-Guaz(RuCp)2+ have been determined. Analysis of the bond lengths and angles coupled with the electrochemistry data provides evidence for strong ground state charge transfer in the series which diminishes upon π-bridge extension. The electronic absorption spectra reveal that alkylation of the cationic terminus (1) diminishes the electron-accepting ability, (2) results in a larger dipole moment change upon excitation and (3) causes a smaller sequential lowering of the CT transitions with π-bridge extension. The NLO properties which were characterised by hyper-Rayleigh scattering techniques indicate the potential of the azulenylium based donor–acceptor chromophores, but also that the extended complexes exhibit two-photon absorption fluorescence.

Ionic [(CpFeCO)2(μ-CO)(μ-CCHCH−)]+ fragments were used as electron acceptors in combination with para-substituted stilbenyl donors to form push−pull chromophores. These μ-vinylcarbyne salts were pr...

In order to investigate nonlinear optical properties, in particular second harmonic generation (SHG) of organometallic complexes, numerous dipolar monocationic sesquifulvalene complexes of the general form [Mc–Z–C7H6]+ have been synthesised (Mc = metallocenyl), wherein the metallocenyl moiety Mc acts as an electron donor, and the tropylium cation C7H6+ as an electron acceptor. The mutual electronic influence of the donor and the acceptor groups is warranted by a linking spacer Z, which is a single bond [Mc = CpFeC5H4 (4a); Mc = CpRuC5H4 (4b)], an unsaturated bridge containing olefins [Z = (E-CHCH)n: n = 1, Mc = CpFeC5H4 (25a), Mc = CpRuC5H4 (25b); n = 2, Mc = CpFeC5H4 (26); n = 3, Mc = CpFeC5H4 (27)], or thiophene units [Z = 2,5-C4H2S, Mc = CpFeC5H4 (28); Z = 5,5′-(2,2′-C4H2S)2, Mc = CpFeC5H4 (29); Z = 2-(5-E-CHCH)C4H2S, Mc = CpFeC5H4 (30)]. For the salts of 4a·BF4, 4b·PF6 and 25a·PF6 X-ray structure determinations have been performed [4a·BF4: orthorhombic, Pnma, = 21.75(2), b = 9.900(2), c = 6.881(3) A, V = 1482.0(15) A3, Z = 4; 4b·PF6: monoclinic, P2(1)/c, a = 8.104(3), b = 18.206(14), c = 11.228(4) A, β = 107.59(3), V = 1579.1(15) A3, Z = 4; 25a·PF6: triclinic, P1bar, a = 10.067(6), b = 10.496(6), c = 11.418(6) A, α = 94.07(4), β = 110.96(4), γ = 102.88(5)°, V = 1083.1(11) A3, Z = 2]; the solid state structures indicate an almost coplanar arrangement of the organic π-system. Cyclic voltammetry studies reveal an irreversible one-electron reduction and an electrochemically reversible one-electron oxidation step for the ferrocenyl derivatives, whereas the ruthenocenyl derivatives demonstrate an irreversible two-electron oxidation. The redox potentials clearly indicate that the oxidation occurs at the metallocene unit, and the reduction is localised on the tropylium entity. In the electronic absorption spectra two intense bands are observed in the region 400 < λ < 900 nm which undergo strong negative solvatochromic shifts. The origin of the high-energy absorption band is assumed to be an interligand charge-transfer (LL–CT) transition, and the low-energy absorption band is assigned to a donor-acceptor charge-transfer (DA–CT) transition. Whereas the LL–CT is continuously shifted to lower energy with increasing spacer length, the energy of the DA–CT approaches a limiting value. A comparable phenomenon is also observed for the difference between the oxidation and reduction potentials obtained from electrochemical studies. Investigations concerning the nonlinear optical properties of the dipolar cationic sesquifulvalene complexes by means of hyper-Rayleigh scattering (HRS) indicate that the ferrocenyl derivatives fluoresce due to two-photon absorption whereas the ruthenocenyl congeners exhibit second harmonic generation with considerably larger first hyperpolarizability which is partly resonance-enhancement based.

Currently, the most important class of nonlinear optical (NLO) compounds providing second harmonic generation (SHG) comprises of electron donating and accepting groups which are electronically coupled. These kinds of dipolar compounds have potential in photonic applications. In this article the synthesis and the NLO activities of dipolar mono- and dinuclear sandwich-like complexes are reviewed. These structures are composed of sesquifulvalenes and metal–ligand fragments MLn and M′L′n which stabilize the aromatic units of the sesquifulvalene moiety. In these complexes the five-membered ring of the sesquifulvalene complexes is coordinated to MLn=Fe(C5H5), Fe(C5Me5), Ru(C5H5) and Co(C4Ar4) and acts as an electron donor; hence, its electron donating capability is varied by changing the MLn entity. The electron withdrawing capability of the seven-membered ring is changed by the coordination of Cr(CO)3 and RuCp+ or by keeping it uncoordinated. In addition, cationic borabenzene complexes are introduced as electron accepting groups. The electronic communication between the donor and acceptor is facilitated by a direct coupling or by introducing acetylenic and olefinic bridges between the donor and acceptor, e.g. E-1,2-ethendiyl, E,E-1,3-diendiyl, E,E,E,-1,5-triendiyl, 2,5-thiendiyl, 2,5′-dithiendiyl. Structural as well as UV–vis spectroscopic studies indicate a distinct mutual influence of the donor and the acceptor of the sesquifulvalene complexes. The NLO properties of these mono- and dinuclear sandwich-type complexes are studied by means of hyper-Rayleigh scattering experiments. They prove that most of the ferrocenyl derivatives demonstrate fluorescence in the region of the SHG due to two-photon absorption whereas all of the ruthenium congeners show SHG which is quantified by determination of the first hyperpolarizability. The measured β-values are large and their magnitude can be partly explained by resonance enhancement. Taking the two-level model into account the calculated values of the static hyperpolarizability are still very large indicating that mono- and bimetallic sesquifulvalene complexes are powerful NLO-chromophores.

Reaction of the ynamine MeC⋮CNEt2 with the pentatetraenylidene complexes [(CO)5MCCCCC(NMe2)2] (M = Cr (3a), W (3b)) at room temperature affords the new heptapentaenylidene complexes [(CO)5MCCCCC(NEt2)C(Me)C(NMe2)2] (M = Cr (5a), W (5b)) in good yield. The spectroscopic data and the X-ray structural analysis of 5a indicate that these amino-substituted metallacumulenes are best described as hybrids of a cumulene and several strongly polarized alkynyl structures. For 5a and the related metallacumulenes [(CO)5MCCC(NMe2)2] (M = Cr (1a), W (1b)), [(CO)5CrCCC(NEt2)C(H)C(NMe2)2] (2a), and 3a,b the molecular first hyperpolarizability β was determined by hyper-Rayleigh scattering experiments. The insertion of a cumulated C2 unit into a metallacumulene quadruples β, while the insertion of a conjugated C2 unit results in only slight enhancement of the second harmonic generation response. Substitution of tungsten for chromium has only a minor effect on β. All observed β values are reasonably high compared with those o...

The pentacarbonyl(vinylidene)chromium complexes [(CO) 5 Cr=C=C(R)R′] ( 1 ) [C(R)R′ = CPh 2 ( a ), C(CH 2 ) 5 ( b ), CMe 2 ( c ), C(Me)H ( d )] react with 1-diethylamino-1-propyne, MeC≡CNEt 2 , by regiospecific addition of the C≡C bond of the alkyne to the C=C bond of the vinylidene ligand to form the cyclobutenylidene complexes ( 2a–d ). The analogous reaction of [(CO) 5 Cr=C=C(Ph)H] with MeC≡CNEt 2 affords via cycloaddition and formal [1,3]-H shift the complex ( 3 ). The cycloadditions of Me 2 NC≡CNMe 2 and MeC≡COEt to 1b give ( 4 ) and ( 5 ) respectively. The addition of ( S )-2-methoxymethyl( N -1-propynyl)pyrrolidine ( 6 ) and ( R )-methyl(1-propynyl)(1-phenylethyl)amine ( 8 ) with 1a–c leads to E/Z mixtures of [R * = ( S )-2-methoxymethyl pyrrolidinyl ( 7a–c ), R * = ( R )-N(Me)[CH(Me)Ph] ( 9a–c )]. In the reactions of 1a–c with 6 predominantly the E isomer, in the reactions of 1a–c with 8 predominantly the Z isomer is formed. All 3-amino substituted complexes exhibit a considerable solvatochromic behavior. The first hyperpolarizability β of 2b was determined by hyper-Rayleigh scattering ( β = 22 × 10 −30 esu). The Kurtz powder method was used to investigate the effectiveness in second harmonic generation of 2d , 3 , 7a , 7b , and 9c . Their efficiencies range from 4 to 35 times that of urea. The structures of 2b and Z- 9b were established by X-ray structural analyses. Together with the results of spectroscopic investigations, they reveal a strongly delocalized π -system [(CO) 5 Cr=C=C=C=N].

Self-assembled monolayer field-effect transistors (SAMFETs) of BTBT functionalized phosphonic acids are fabricated. The molecular design enables device operation with charge carrier mobilities up to 10-2 cm 2 V-1 s-1 and for the first time SAMFETs which operate on rough, flexible PEN substrates even under mechanical substrate bending. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An asymmetric n-alkyl substitution pattern was realized in 2-tridecyl[1]benzothieno[3,2-b][1]benzothiophene (C(13)-BTBT) in order to improve the charge transport properties in organic thin-film transistors. We obtained large hole mobilities up to 17.2 cm(2)/(V·s) in low-voltage operating devices. The large mobility is related to densely packed layers of the BTBT π-systems at the channel interface dedicated to the substitution motif and confirmed by X-ray reflectivity measurements. The devices exhibit promising stability in continuous operation for several hours in ambient air.

We report a quantitative study that describes and correlates the threshold voltage of low-voltage organic field-effect transistors with the molecular structure of self-assembled monolayer dielectrics. We have observed that the component of the dipole moment of such self-assembled molecules perpendicular to the surface correlates linearly with the threshold voltage shift in devices. The model was validated using three different organic semiconductors (pentacene, α,α'-dihexylsexithiophene, and fullerene-C(60)) on six different self-assembled monolayers. The correlation found can help optimize future devices, by tuning the dipole moments of the molecules that constitute the self-assembled monolayer.

We report on p- and n-type organic self-assembled monolayer held effect transistors. On the base of quaterthiophene and fullerene units, multifunctional molecules were synthesized, which have the ability to self-assemble and provide multifunctional monolayers. The self-assembly approach, based on phosphonic acids, is very robust and allows the fabrication of functional devices even on larger areas. The p- and n-type transistor devices with only one molecular active layer were demonstrated for transistor channel lengths up to 10 mu m. The monolayer composition is proven by electrical experiments and by high-resolution transmission electron microscopy, electron energy loss spectroscopy, XPS, and AFM experiments. Because of the molecular design and the contribution of isolating alkyl chains to the hybrid dielectric, our devices operate at low supply voltages (-4 V to +4 V), which is a key requirement for practical use and simplifies the integration in standard applications. The monolayer devices operate in ambient air and show hole and electron mobilities of 10(-5) cm(2)/(V s) and 10(-4) cm(2)/(V s) respectively. In particular the n-type operation of self-assembled monolayer transistors has not been reported before. Hereby, structure-property relations of the SAMs have been studied. Furthermore an approach to protect the sensitive C-60 from immediate degradation within the molecular design is provided.

PEDOT based polyelectrolyte complexes are widely used as hole injection layers in OLEDs. They are available with high and low work functions. A new polystyrenesulfonic acid free water based complex has been developed that offers easy processing. Due to its high stability it gives rise to efficient and long living devices. Small molecule semiconductors can exhibit high charge carrier mobilities due to their high crystallinity. Oligomeric semiconductor materials with mobilities >3 cm 2 /Vs have been synthesized using the benzothienobenzothiophene (BTBT) core.

Unsymmetrical dimethylchlorosilyl-substituted α, α′- dialkylquater-, quinque-, and sexithiophenes were designed and successfully synthesized by a combination of Kumada and Suzuki cross-coupling reactions followed by hydrosilylation. Optimization possibilities of the hydrosilylation of low-soluble linear oligothiophenes by dimethylchlorosilane as well as the nonreactive byproducts formed are described. The molecular structures of the obtained dimethylchlorosilyl-functionalized oligothiophenes were proven by NMR and DCI MS techniques. These compounds were found to be stable and reactive enough, even in the presence of the nonreactive byproducts, to form semiconducting monolayers on dielectric hydroxylated SiO2 surfaces by self-assembly from solution. The semiconducting properties of these oligothiophene SAMs were as good as those of bulk oligothiophenes. This allowed the production of stable, even under ambient conditions, SAMFETs with a mobility of up to 0.04 cm2/(V s) and an on/off ratio up to 1 × 10 8. © 2010 American Chemical Society.

The development of suitable materials for organic electronics is still one of the key points to access new application areas with this promising technology. Semiconductors based on thiophene chemistry show very high charge carrier mobilities. The functionalization with linker groups provided materials that built monomolecular layers of the semiconductors on the hydrolyzed oxide surface of a silicon-wafer. This approach lead to self-assembled mono-layer field-effect transistors (SAM-FETs) with mobilities of up to 0.04 cm 2 /Vs, which is comparable to the values of the respective bulk thin film. Transparent inorganic conductors like ITO are highly conductive but the costly processing and the brittleness hamper their use in cost-sensitive and/or flexible devices. Highly conductive PEDOT-grades have been developed with conductivities of up to 1000 S/cm which are easily applicable by printing techniques and can be used as ITO replacement in devices such as touch panels or organic photovoltaics.

Organic electronics open new fields of applications requiring large-area coverage, structural flexibility, low-temperature and low-cost processing. A key for this technology is access to suitable materials. Progress in conducting and semiconducting materials for organic electronics will be reported. Highly conductive PEDOT-grades have been developed for high resolution printing. Linear oligomeric and star shaped oligothiophenes will be discussed. These materials show outstanding carge carrier mobility and environmental stability when deposited from vacuum deposition. After fine tuning the deposition parameter by ink jet printing we also obtained transistors with excellent properties. The concept of "flexible core" star shaped oligothiophenes will be discussion which might be a way to combine both, high charge carrier and wet processing.

Structure-property relationships based on experimental as well as theoretical results will be elucidated. For this purpose different dipolar organometallic compounds were synthesized and characterized. The alteration of the donor and acceptor termini in mono- and dinuclear sesquifulvalene complexes results in spectroscopic and even structural modifications. The structural and 1H NMR spectroscopic changes correlate with the experimentally obtained first hyperpolarizability. The potent electron-donating (D) group [(CpFeCO)2(μ-CO)(μ-C=CH-)] is combined with different electron-accepting units (A), yielding the push-pull complexes [(CpFeCO)2(μCO)(μ-C=CH-CH=A)]. The extent of electron delocalization within the π-bridge connecting the donor D and the acceptor A can be monitored by means of 1H NMR spectroscopy. A correlation between the 3J(Hβ-Hγ) coupling constants and the first hyperpolarizability is found, which very much resembles the dependence of the first hyperpolarizability on the bond length alternation. In order to elucidate the dependence of the NLO response on the conformation of triply branched NLOphores, a new series of dendritic D-μ-A structures has been synthesized. A combined approach of experiments and computational predictions was applied both on the dendrimers and on the corresponding single-strand chromophores. These results demonstrate that theoretical calculations are able to reproduce experimental results and show the tendency of the effects due to structural changes

The development of two-photon laser scanning fluorescence microscopy (TPLSM) has provided a new capability for 3D imaging in whole and living tissues, reduced photobleaching effects, and greater depth penetration. Since the rate of two-photon excitation is proportional to the square of the light intensity, degree of excitation falls off roughly as the fourth power of distance from the focal plane. The full potential of two-photon fluorescence microscopy has not been realized, in part, because fluorophores under use have been developed for single photon excitation and have not been optimized for two-photon absorption. Highly efficient two-photon fluorophores are needed to allow sensitive detection of small numbers of labeled sites and to reduce the optical power of the exciting laser beam that is needed to produce adequate signal levels. The sensitivity of a two-photon fluorescence label is determined by the product of the two-photon absorption cross section and the fluorescence quantum efficiency.

Ligand-coated metallic nanoparticles are powerful new materials for nano-electronic and photonics applications. They can be readily synthesized and their stability and solubility allows them to be cast in complex composite materials or self-assembled into quasi-ordered films. We demonstrate that, in the presence of reducing dyes with a large two-photon cross-section and metal salts, it is possible to induce the growth of metal nanoparticles in composite films under optical excitation or irradiation with electrons. We demonstrate further that continuous metal structures can be obtained via laser irradiation of the composites and that, with two-photon excitation, 3D structures can be fabricated. Silver, copper, and gold microstructures have been fabricated via two-photon excitation. The composition of our polymeric precursor is described in detail. In order to achieve highly-homogenous solid-state solutions of nanoparticles dissolved in polyvinylcarbazole (PVK), we have synthesized tailor-made nanoparticles on which we have introduced a mixture of carbazoyl-terminated octylthiol and simple octylthiols.. Preliminary experiments on e-beam lithography show that thin films of nanoparticles doped with suitable dyes and metal salts are efficient precursors form metal structures.

Strong enhancement of the two-photon absorption of organic molecules near silver nanoparticle fractal clusters has been observed and has been exploited to yield composite materials with very strong two-photon absorption and two-photon-excited fluorescence properties. Measurements on cluster films coated with chromophoric polymer or with thiol-bound chromophores give spatially-averaged enhancements of 1000 and 20 000, respectively. Two-photon fluorescence microscopy studies show that the enhancements are spatially inhomogeneous, with peak-enhancement factors of ≥ 10 000 (polymer/cluster) and ≥ 160 000 (thiol chromophore/cluster), and excitation frequency dependent. These results are in accord with theoretical predictions of local-field effects due to strong localization of collective plasmon modes in fractal metal clusters, and demonstrate an approach to ultrasensitive two-photon processes.

Two different types of dipolar cationic sesquifulvalene complexes were prepared and investigated by electrochemistry, UV-vis spectroscopy and hyper-Rayleigh scattering: i) monocationic, mononuclear species with different spacers Z, and ii) dinuclear derivatives with different electron acceptors, and the five- and seven- membered rings in close contact.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.