Synthesis and Optoelectronic Properties of a Quinoxalino-Phenanthrophenazine (QPP) Extended Tribenzotriquinacene (TBTQ).

A six-step synthesis towards a tribenzotriquinacene (TBTQ) bearing three quinoxalinophenanthrophenazine (QPP) units is presented. The optoelectronic properties are investigated and the effect of the three-dimensional arrangement of the individual QPP planes is examined using optical spectroscopy, electrochemical analysis and quantum-chemical calculations.

Tailoring Ultrafast Singlet Fission by the Chemical Modification of Phenazinothiadiazoles.

Quantum chemistry and time-resolved spectroscopy are applied to rationalize how singlet fission (SF) is affected by systematic chemical modifications introduced into phenazinothiadiazoles (PTD). Substitution of the terminal aromatic ring of TIPS-tetracene by a thiadiazole group leads to a considerable change in the relative energies of its S1 and T1 states. Thus, in contrast to TIPS-tetracene, SF becomes exothermic for various PTD derivatives, which show S1-2T1 energy differences as high as 0.15 eV. This enables SF in PTD as corroborated by femtosecond transient absorption spectroscopy and TD-DFT calculations. The latter report T-T spectra consistent with thin film UV-vis femtosecond transient absorption of PTDs at long delays. TD-DFT calculations also show that the S1-T1 energy gap can be rationally tuned by introducing N atoms into the aromatic scaffold and by the halogenation of one side ring of the PTD. In addition, the specific S1-to-1(T1T1) electronic coupling depends on the crystal morphology and the electronic properties simultaneously. Thus, both of them govern the strength and the interplay between direct and superexchange couplings, which in the most favorable cases accelerate SF to rate constants beyond (100 fs)-1. Remarkably, direct coupling was found to contribute considerably to the total effective coupling and even to dominate it for some PTDs investigated here. A quantum yield of 200% is obtained on the early picosecond time scale for all compounds studied here, which is reduced to 100% due to triplet-triplet annihilation after a few nanoseconds.

N-Acenoacenes.

The syntheses of new, fourfold alkynylated tetraazaacenoacenes (tetraazaanthracenoanthracene, tetraazatetracenotetracene and tetraazapentacenopentacene) are reported. This novel heteroacenoacene motif exhibits surprisingly strong electronic coupling between its constituting diazaacene units.

Helical Ullazine-Quinoxaline-Based Polycyclic Aromatic Hydrocarbons.

Polycyclic aromatic azomethine ylides (PAMYs) are powerful building blocks in the bottom-up synthesis of internally nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs) through 1,3-cycloaddition reactions. In this work, the cycloaddition reaction of PAMYs to asymmetric ortho-quinones is presented, which, in contrast to the addition to symmetric para-quinones, facilitates subsequent condensation reactions and allows the synthesis of three helical N-PAHs with ullazine-quinoxaline (UQ-1-3) backbones. UQ-1 and UQ-2 possess two helical centers; however, single-crystal X-ray analysis together with the computational modeling of UQ-3 elucidate the formation of only the thermodynamically most stable geometry with four helical centers in a (P,P,M,M) configuration. For the series UQ-1-3, the number of redox steps is directly correlated with the number of ullazine or quinoxaline units incorporated into the targeted molecular backbones. A detailed investigation of the spectroscopic and magnetic properties of the radical cation and anion as well as the dication and dianion species by in situ EPR/UV/Vis-NIR spectroelectrochemistry is provided. The excellent optical and redox properties combined with helical geometries render them possibly applicable as chiral emitter or ambipolar charge transport material in organic electronics.

Azaarene Dimers.

Binaphthyl-3,3',4,4'-tetraone was prepared and coupled to different bis(TIPS-ethynyl)-substituted (TIPS=triisopropyl silane) aromatic diamines, resulting in the formation of dimeric benzo-fused azaacenes, centrally connected by a single bond. The two halves of the molecules are highly twisted with respect to each other and showed limited electronic interaction in the ground state because their absorption spectra remained very similar to those of the constituting monomers. The dimers displayed greatly reduced fluorescence when compared to the monomers, suggesting that there is a significant interaction of the two azarene units in the excited state. Preliminary investigations showed that the dimers are attractive for application as acceptors in organic photovoltaic because they significantly outperform their monomeric counterparts.

Mono- and Dianion of a Bis(benzobuta)tetraazapentacene Derivative.

A bis(benzobuta)tetraazapentacene derivative was reduced to its radical anion and its dianion, using potassium [18]crown-6 anthracenide in THF. Both reduced species were characterized by UV/Vis spectroscopy of the isolated species and by spectroelectrochemistry. Two distinct single-crystal structures of the dianion and an EPR spectrum of the radical anion were obtained. Contrary to other azaacenes, the lowest energy absorption in the UV/Vis spectrum of the dianion is redshifted in comparison to that of the neutral compound.

Phenylene Bridged Cyclic Azaacenes: Dimers and Trimers.

The synthesis and characterization of novel macrocyclic, phenylene-bridged azaacenes is reported. These species were obtained either by a conventional benzoin- diamine condensation, as shown for the case of the cyclotrimers, in which the azaacene units are separated by meta-connected phenylene bridges, or by a Buchwald-Hartwig-type Pd-catalyzed coupling, which employs 1,2,5,6-tetrabromodibenzocyclooctatetraene as the substrate and bis-TIPS-ethynylated diaminobenzene, -naphthalene or -anthracene as the coupling partner to give the double coupling products azaacene-annulated dibenzocyclooctatetraenes in moderate yields. The macrocycles show strong emission and light emitting diodes have been built with brightnesses exceeding 1600 cd m-2 . We evaluated the optical and electronic properties and the solid-state structures of the molecules and discuss their properties through comparison with their linear and tetrameric N-heteroacene counterparts.

Preparation, Properties, and Structures of the Radical Anions and Dianions of Azapentacenes.

A series of diazapentacenes (5,14-diethynyldibenzo[b,i]phenazine, 6,13-diethynylnaphtho[2,3-b]phenazine) and tetraazapentacenes (7,12-diethynylbenzo[g]quinoxalino[2,3-b]quinoxaline, 6,13-diethynylquinoxalino[2,3-b]phenazine) were reduced to their radical anions and dianions, employing either potassium anthracenide or lithium naphthalenide in THF. The anionic species formed were investigated by UV-vis-NIR, fluorescence and EPR spectroscopy, spectroelectrochemistry, and quantum chemical calculations. Single crystal X-ray structures of three of their radical anions and of three of their dianions were obtained. In contrast to the acenes, the anions of the azapentacenes are persistent and, in some cases, even moderately stable toward air, and were characterized.

Dibenzobarrelene-Based Azaacenes: Emitters in Organic Light-Emitting Diodes.

The synthesis of soluble dibenzobarrelene-substituted azaacenes either by condensation reactions in solution or, more effectively, in the solid state by using a ball mill is reported herein. We relate their optical properties in thin films to their packing in the solid state. The targets are characterized by cyclic voltammetry, X-ray crystallography and UV/Vis and fluorescence analysis. Three highly fluorescent, amorphous azaacenes were processed into organic light-emitting diodes, and their improved performance (luminance, efficiency and efficacy) was compared with that of structurally related iptycene-based azaacenes.

Synthesis and Characterization of Heterobenzenacyclo-octaphanes Derived from Cyclotetrabenzoin.

We describe the modular synthesis and characterization of several substituted N-hetero benzenacyclooctaphanes (BAOs), a new motif for heteroaromatic conjugated macrocycles. The targets were synthesized via condensation of substituted aromatic ortho-diamines with a cyclic octaketone building block in moderate to excellent yields (41-91 %). We evaluated the optical and electronic properties and the solid-state structures of the targets and discuss their properties through comparison with their linear diphenyl N-heteroacene counterparts.

Dicyano-Substituted Diazaacenes.

Herein, we report the synthesis, spectroscopic, and structural properties of novel 2,3-dicyano-substituted azaacenes containing three to six annelated rings as a framework. The targets were prepared by Pd-catalyzed coupling of diamino-bis(tri-isopropylsilylethynyl)benzene, -naphthalene, and -anthracene with either 4,5-dibromophthalonitrile or 6,7-dibromonaphthalene-2,3-dicarbonitrile into the respective N,N'-dihydrodiazaacenes. Oxidation with MnO2 or PbO2 furnishes the dicyano-substituted diazaacenes in reasonable to good yields. An exception is the diazahexacene, where the N,N'-dihydrodiazaacene is difficult to oxidize. Most of the targets could be crystallized and pack in isolated pairs, stacks, and brick-wall motifs. The n-type behavior of these molecules was illustrated in a proof-of-concept organic field-effect transistor, showing mobilities up to 7×10-3  cm2 V-1 s-1 .

Alkyne-Substituted N-Heterophenes.

The synthesis and characterization of novel S-shaped N-heterophenes is reported. The targets contain a central anthracene connected to two heterophenanthrene units. N-Heterophenes are synthesized by reacting Boldt's 1,2,6,7-anthracenetetraone with different dialkynylated ortho-diaminobenzenes. The condensation yields range from 63 to 75 %; all of the N-heterophenes are stable and isolable.

Synthesis of Alkynylated Benzo[a]naphtho[2,3-i]phenazine Derivatives.

Thermal condensation of 2,3-diamino-1,4-(bistriisopropylsilylethynyl)benzene, -naphthalene,-anthracene, and -benzothiadiazole substrates with 1,2-naphthalenedione forms bent benzophenazine-type heteroarenes in a one-step reaction in good to excellent yields. The targets are investigated by UV/Vis spectroscopy, cyclic voltammetry, and single-crystal X-ray crystallography. The packing of the targets in the solid state follows either a herringbone or a brick wall motif. In the case of 8,13-bis(triisopropylsilylethynyl)dibenzo[a,i]phenazine, polymorphs with either packing result.

Polyelectrolyte Complexes Formed from Conjugated Polymers: Array-Based Sensing of Organic Acids.

One fluorescent, positively charged poly(para-phenyleneethynylene) (PAE 1) forms electrostatic complexes with five negatively charged pyridine- or benzothiadiazole-containing poly(para-aryleneethynylene)s (PAE 2-PAE 6). The PAE 2-PAE 6 are less fluorescent in water and act as quenchers for PAE 1 in their electrostatic complexes C 1-C 5; the PAE-complexes (2 µm) were exposed to thirteen different carboxylic acids (50 mm) in buffered aqueous solution. The fluorescence responses of the small library of electrostatic PAE-complexes towards the acids was analyzed; discrimination of all of the thirteen acids was achieved. The investigated acids include acetic, butyric, tartaric, maleic, lactic, sorbic, oxalic, aspartic, and citric acids. A random, simple, ad-hoc library of electrostatic polymer complexes, C 1-C 5, therefore discerns the thirteen carboxylic acids in water.

Bent N-Heteroarenes.

The syntheses and optical, electronic, and structural properties of a series of bent N-heteroarenes are described. The targets were obtained by condensation reactions of substituted aromatic o-diamines with 1,2-naphthoquinone and 1,2-anthraquinone in yields between 34 and 94%; naphthoquione-based products are generally formed in higher yields.

Complications and Outcomes of Surgically Treated Pediatric Supracondylar Humerus Fractures.

This study describes the outcome of supracondylar humerus fractures in children using crossed K-wires after closed or open reduction with the medial, lateral or bilateral approach. Patients treated between January 2000 and December 2019 were classified according to the Von Laer classification, complications were classified according to the Sink classification and clinical outcomes were classified according to modified Flynn criteria. In total, 364 patients with a mean age of 5.23 ± 2.45 years were included. The majority were type IV fractures (156; 42.9%) and 94 (60.3%) needed an open reduction for which the medial approach (53; 56.4%) was predominantly used. Overall, of 50 complications (31 using closed reduction, 19 open reduction), 17/50 (34%) needed revision surgery. An excellent clinical outcome was achieved in 348/364 (95.6%) patients. The approach used for open reduction as such had no influence on the complication rate or clinical outcome. For severely displaced fractures, the data showed that an open approach for crossed K-wires tended to result in fewer complications and better clinical outcomes than a closed reduction. If an open reduction is indicated, the required approach (medial, lateral or bilateral) should be primarily selected according to the requirements of the fracture pattern and eventual cosmetic considerations.

Increased pupil and heart-rate responses to sexual stimuli in men after physical exertion.

Physical stress has been found to enhance arousability by visual sexual stimuli on a short-term basis, as reflected in higher phasic pupil dilation responses, probably mediated by sympathetic nervous system (SNS)-related processes. However, previous research has not addressed the specificity of this effect in terms of emotional valence, that is, whether it reflects an instance of general excitation transfer or a more specific mechanism. Thus, to further investigate changes in sexual processing after acute stress exposure, 40 male participants underwent either a predominantly sympathetic stressor (3 min sustained handgrip) or similar control procedure. After stress induction, pictures varying in valence as well as sexual versus non-sexual arousal were presented (for 5000 ms each). Using principal component analysis, pupillary responses during picture viewing were dissociated into fast and slow components (early vs. late response phases). In addition, startle eyeblink responses were elicited by bursts of white noise (50 ms, 105 dB) in half of the trials and recorded at the orbicularis oculi via electromyography. Skin conductance and heart rate were co-registered, as well. While affective startle modulation and skin conductance responses to emotional stimuli were unaffected by previous stress exposure, both evoked heart-rate deceleration (but not acceleration) and pupil responses were specifically enhanced with sexually arousing stimuli in stressed participants, and this effect was mediated by blood pressure reactivity as an index of preceding SNS activation. Taken together, our findings provide strong evidence for enhancement of sexual processing by acute stress exposure in men and suggest differential involvement of parasympathetic versus sympathetic mechanisms.

Correlation of Fall Height, Fracture Severity and Clinical Outcome in Pediatric Supracondylar Fractures-A Retrospective Analysis with an Observation Period of 20 Years.

The most common cause leading to supracondylar humerus fractures in children is falling onto an outstretched arm. A correlation between fall height and fracture severity may be assumed but has not yet been described. The aim of this study was to show that fracture severity increases with fall height. Furthermore, the correlation between fracture severity and outcome was examined. A total of 971 children with supracondylar humerus fractures between January 2000 and December 2019 were included in this study. The correlations between fall height and fracture severity and between fracture severity and outcome were assessed. Increasing fall height correlates with fracture severity (p < 0.001; r = 0.24). Furthermore, the incidence of complications increases with fracture severity and a correlation was present accordingly (p < 0.001; r = 0.28). A total of 30 (3.1%) patients showed limitations in range of motion and/or persistent neurologic deficits at the latest follow-up. Type I fractures rarely lead to subsequent limitations. The correlation between increasing fall height and fracture severity was significant. Furthermore, children with type III and IV supracondylar fractures are more likely to develop complications or restrictions in movement than children with type I and II fractures. Hence, the initial fall height may be an indirect indicator of a more or less favorable outcome.

Biomarkers in Cardiorenal Syndrome and Potential Insights Into Novel Therapeutics.

Heart and kidney failure often co-exist and confer high morbidity and mortality. The complex bi-directional nature of heart and kidney dysfunction is referred to as cardiorenal syndrome, and can be induced by acute or chronic dysfunction of either organ or secondary to systemic diseases. The five clinical subtypes of cardiorenal syndrome are categorized by the perceived primary precipitant of organ injury but lack precision. Traditional biomarkers such as serum creatinine are also limited in their ability to provide an early and accurate diagnosis of cardiorenal syndrome. Novel biomarkers have the potential to assist in the diagnosis of cardiorenal syndrome and guide treatment by evaluating the relative roles of implicated pathophysiological pathways such as hemodynamic dysfunction, neurohormonal activation, endothelial dysfunction, inflammation and oxidative stress, and fibrosis. In this review, we assess the utility of biomarkers that correlate with kidney and cardiac (dys)function, inflammation/oxidative stress, fibrosis, and cell cycle arrest, as well as emerging novel biomarkers (thrombospondin-1/CD47, glycocalyx and interleukin-1ß) that may provide prediction and prognostication of cardiorenal syndrome, and guide potential development of targeted therapeutics.

Time course of skeletal muscle regeneration after severe trauma.

BACKGROUND AND PURPOSE: Animal models of skeletal muscle injury should be thoroughly described and should mimic the clinical situation. We established a model of a critical size crush injury of the soleus muscle in rats. The aim was to describe the time course of skeletal muscle regeneration using mechanical, histological, and magnetic resonance (MR) tomographic methods. METHODS: Left soleus muscles of 36 Sprague-Dawley rats were crushed in situ in a standardized manner. We scanned the lower legs of 6 animals by 7-tesla MR one week, 4 weeks, and 8 weeks after trauma. Regeneration was evaluated at these times by in vivo measurement of muscle contraction forces after fast-twitch and tetanic stimulation (groups 1W, 4W, 8W; 6 per group). Histological and immunohistological analysis was performed and the amount of fibrosis within the injured muscles was determined histomorphologically. RESULTS: MR signals of the traumatized soleus muscles showed a clear time course concerning microstructure and T1 and T2 signal intensity. Newly developed neural endplates and myotendinous junctions could be seen in the injured zones of the soleus. Tetanic force increased continuously, starting at 23% (SD 4) of the control side (p < 0.001) 1 week after trauma and recovering to 55% (SD 23) after 8 weeks. Fibrotic tissue occupied 40% (SD 4) of the traumatized muscles after the first week, decreased to approximately 25% after 4 weeks, and remained at this value until 8 weeks. INTERPRETATION: At both the functional level and the morphological level, skeletal muscle regeneration follows a distinct time course. Our trauma model allows investigation of muscle regeneration after a standardized injury to muscle fibers.