Exploiting Orthogonal C-C Cross-Coupling Reactions for Chemistry-on-the-Complex: Modular Assembly of 2,6-Di(quinolin-8-yl)pyridine Ruthenium(II) Photosensitizer Triads.

In this work, we present a concise modular assembly strategy using one universal heteroleptic 2,6-di(quinolin-8-yl)pyridine-based ruthenium(II) complex as a starting building block. Extending the concept from established ligand modifications and subsequent complexation (classical route), the later appearing chemistry-on-the-complex methodology was used for late-stage syntheses, i.e., assembling discrete building blocks to molecular architectures (here: dyad and triads). We focused on Suzuki-Miyaura and Sonogashira cross-couplings as two of the best-known C-C bond forming reactions. Both were performed on one building block complex bearing a bromine and TIPS-protected alkyne for functional group interconversion (bromine to TMS-protected alkyne, a benzyl azide, or a boronic acid pinacol ester moiety with ≥95% isolated yield and simple purification) as well as building block assemblies using both a triarylamine-based donor and a naphthalene diimide-based acceptor in up to 86% isolated yield. Additionally, the developed purification via automated flash chromatography is simple compared to tedious manual chromatography for ruthenium(II)-based substrates in the classical route. Based on the preliminary characterization by steady-state spectroscopy, the observed emission quenching in the triad (55%) serves as an entry to rationally optimize the modular units via chemistry-on-the-complex to elucidate energy and electron transfer.

Virus-Subtype-Specific Cellular and Humoral Immune Response to a COVID-19 mRNA Vaccine in Chronic Kidney Disease Patients and Renal Transplant Recipients.

Patients with chronic kidney disease (CKD) or immunosuppression are at increased risk of severe SARS-CoV-2 infection. The vaccination of CKD patients has resulted in lower antibody concentrations and possibly reduced protection. However, little information is available on how T-cell-mediated immune response is affected in those patients and how vaccine-induced immune responses can neutralise different SARS-CoV-2 variants. Herein, we studied virus-specific humoral and cellular immune responses after two doses of mRNA-1273 (Moderna) vaccine in 42 patients suffering from CKD, small vessel vasculitis (maintenance phase), or kidney transplant recipients (KT). Serum and PBMCs from baseline and at three months after vaccination were used to determine SARS-CoV-2 S1-specific antibodies, neutralisation titers against SARS-CoV-2 WT, B1.617.2 (delta), and BA.1 (omicron) variants as well as virus-specific T-cells via IFNγ ELISpot assays. We observed a significant increase in quantitative and neutralising antibody titers against SARS-CoV-2 and significantly increased T-cell responses to SARS-CoV-2 S1 antigen after vaccination only in the CKD patients. In patients with vasculitis, neither humoral nor cellular responses were detected. In KT recipients, antibodies and virus neutralisation against WT and delta, but not against omicron BA.1, was assured. Importantly, we found no specific SARS-CoV-2 T-cell response in vasculitis and KT subjects, although unspecific T-cell activation was evident in most patients even before vaccination. While pre-dialysis CKD patients appear to mount an effective immune response for in vitro neutralisation of SARS-CoV-2, KT and vasculitis patients under immunosuppressive therapy were insufficiently protected from SARS-CoV-2 two months after the second dose of an mRNA vaccine.

Vaccination and Omicron BA.1/BA.2 Convalescence Enhance Systemic but Not Mucosal Immunity against BA.4/5.

Rising breakthrough infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron BA.4/5 led to the performance of various studies investigating systemic immunity and neutralizing antibodies in sera, but mucosal immunity remains understudied. In this cohort study, the humoral immune responses, including immunoglobulin levels and the presence of virus-neutralizing antibodies, of 92 vaccinated and/or BA.1/BA.2 convalescent individuals were investigated. Cohorts received two doses of ChAdOx1, BNT162b2, or mRNA-1273 and subsequent booster vaccination with either BNT162b2 or mRNA-1273, following BA.1/BA.2 infection. In addition, vaccinated and nonconvalescent or unvaccinated and BA.1 convalescent individuals were studied. Serum and saliva samples were used to determine SARS-CoV-2 spike-specific IgG and IgA titers and neutralizing activity against replication-competent SARS-CoV-2 wild-type virus and the Omicron BA.4/5 variant. Vaccinated/convalescent cohorts demonstrated strongest neutralization against BA.4/5, with 50% neutralization titer (NT50) values reaching 174.2; however, neutralization was reduced up to 11-fold, compared to wild-type virus. Both BA.1 convalescent and vaccinated nonconvalescent cohorts displayed the weakest neutralization against BA.4/5, with NT50 values being reduced to 4.6, accompanied by lower numbers of positive neutralizers. Additionally, salivary neutralization against wild-type virus was strongest in vaccinated and BA.2 convalescent subjects, but this elevated neutralization efficiency was lost when challenged with BA.4/5. Our data support the contention that current coronavirus disease 2019 (COVID-19) vaccines efficiently induce humoral immunity. However, antiviral effectiveness in serum and saliva is greatly reduced against novel variants of concern. These results suggest an adjustment of current vaccine strategies to an adapted or alternative vaccine delivery, such as mucosal booster vaccinations, which might establish enhanced or even sterilizing immunity against novel SARS-CoV-2 variants. IMPORTANCE Rising incidences of breakthrough infections caused by SARS-CoV-2 Omicron BA.4/5 have been observed. Although various studies were conducted investigating neutralizing antibodies in sera, mucosal immunity was barely evaluated. Here, we investigated mucosal immunity, since the presence of neutralizing antibodies at mucosal entry sites plays a fundamental role in disease limitation. We found strong induction of serum IgG/IgA, salivary IgA, and neutralization against SARS-CoV-2 wild-type virus in vaccinated/convalescent subjects but detected 10-fold reduced (albeit positive) serum neutralization against BA.4/5. Interestingly, vaccinated and BA.2 convalescent patients demonstrated the greatest serum neutralization against BA.4/5, but this advantageous neutralizing effect was not observed in the saliva. Our data support the contention that current COVID-19 vaccines are very efficient against severe/critical disease progression. Moreover, these results suggest an adjustment of the current vaccine strategy to adapted and alternative vaccine delivery, such as mucosal booster vaccinations, to establish robust sterilizing immunity against novel SARS-CoV-2 variants.

Immunity of Heterologously and Homologously Boosted or Convalescent Individuals Against Omicron BA.1, BA.2, and BA.4/5 Variants.

BACKGROUND: The emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variants BA.1, BA.2, and BA.4/5 demonstrate higher transmission and infection rates than previous variants of concern. To evaluate effectiveness of heterologous and homologous booster vaccination, we directly compared cellular and humoral immune responses as well as neutralizing capacity against replication-competent SARS-CoV-2 wild type, Delta, and Omicron variants BA.1, BA.2, and BA.4/5. METHODS: Peripheral blood mononuclear cells and serum samples from 137 participants were investigated, in 3 major groups. Individuals in the first group were vaccinated twice with ChAdOx1 and boosted with a messenger RNA (mRNA) vaccine (BNT162b2 or mRNA-1273); the second group included triple mRNA--vaccinated participants, and the third group, twice-vaccinated and convalescent individuals. RESULTS: Vaccination and convalescence resulted in the highest SARS-CoV-2-specific antibody levels, stronger T-cell responses, and best neutralization against wild type, Delta Omicron BA.2, and BA.4/5, while a combination of ChAdOx1 and BNT162b2 vaccination elevated neutralizing capacity against Omicron BA.1. In addition, heterologous booster regimens, compared with homologous regimens, showed higher efficacy against Omicron BA.2 as well as BA.4/5. CONCLUSIONS: We showed that twice-vaccinated and convalescent individuals demonstrated the strongest immunity against Omicron BA.2 and BA.4/5 variant, followed by those receiving heterologous and homologous booster vaccine regimens.

Antiviral drugs block replication of highly immune-evasive Omicron subvariants ex vivo, but fail to reduce tissue inflammation.

The identification of the SARS-CoV-2 Omicron variants BA.4/BA.5, BF.7 and BQ.1.1 immediately raised concerns regarding the efficacy of currently used monoclonal antibody therapies. Here we examined the activity of monoclonal antibody therapies and antiviral drugs against clinical specimens for SARS-CoV-2 Omicron BA.4/BA.5, BF.7 and BQ.1.1 employing an immunofluorescence neutralization assay. Further we explored treatment of BA.4/BA.5 infections with efficient antiviral drugs and monoclonal antibodies in a 3D model of primary human bronchial epithelial cells. We found that the antiviral drugs Molnupiravir, Nirmatrelvir and Remdesivir efficiently inhibit BA.4/BA.5, BF.7 and BQ.1.1 replication. In contrast, only the monoclonal antibody Cilgavimab exerted an inhibitory effect, while Tixagevimab, Regdanvimab and Sotrovimab lost their efficacy against BA.4/BA.5. We found that only the prophylactic treatment with Cilgavimab impacted on tissue inflammation by reducing intracellular complement component 3 (C3) activation following BA.4/BA.5 infection in primary human airway epithelial grown in air-liquid-interphase, which was not the case when using antiviral drugs or Cilgavimab after establishment of infection. Of note, all tested monoclonal antibodies had no neutralizing activity during infection by BF.7 and BQ.1.1 variants. Our results suggest that despite a marked reduction of viral replication, potent antiviral drugs fail to reduce tissue levels of inflammatory compounds such as C3, which can still result in tissue destruction.

Serum Neutralization Against SARS-CoV-2 Variants Is Heterogenic and Depends on Vaccination Regimen.

Omicron variants are still the dominant SARS-CoV-2 viruses worldwide, therefore determination of the level of protection from infection and severe disease is essential. Here, we investigated humoral and cellular immunity of individuals immunized by ChAdOx1, BNT162b2, and mRNA-1273 and our results show that IgG and neutralization titers wane over time. However, strongest neutralization against Omicron BA.1 and T-cell responses were detected in ChAdOx1 vaccinees 6 months after the second dose, while no long-lasting neutralization was shown against BA.2 in any cohort. Crucially, our investigation revealed that immunity against variants of concern is heterogenic and dependent on the immunization status.

Acid-base responsive photoluminescence switching of CdSe/ZnS quantum dots coupled to plasmonic gold film using nanometer-thick poly[(2-diethylamino)ethyl methacrylate] layer.

The control of plasmon-nanoemitter interactions at the nanoscale enables the tailored modulation of optical properties, namely, the photoluminescence (PL) intensity of the nanoemitters. In this contribution, using a nanometer-thick poly[(2-diethylamino) ethyl methacrylate] (39 to 74 nm) as pH responsive spacer layer (pKa ∼ 6 to 6.5) between a plasmonic gold film and CdSe/ZnS Quantum Dots (QDs) nanoemitters, we could achieve reversible pH-responsive PL switching in QDs. In fact, the swelling (at pH 5) and shrinking (at pH 11) function of the pH-responsive spacer layer modulates the distance between the QDs and the gold surface, which dictates the plasmonic film-QDs nanoemitter interaction. Notably, we observed a high QDs' PL enhancement of up to a factor of 3.1 ± 0.4 through changing the pH value from 5 to 11. Furthermore, based on a systematic analysis of several samples with different spacer layer thicknesses and multiple pH cycles, our developed system revealed substantial stability, reversibility and PL enhancement reproducibility. Thus, the established acid-base responsive switchable systems may represent an appealing platform for applications such as sensors, biochemical assays, optoelectronics and logic gates and can be easily evolved to other multifunctional switchable systems using alternative stimuli-responsive polymers.

Immune Responses Against SARS-CoV-2 WT and Delta Variant in Elderly BNT162b2 Vaccinees.

Background: Residents of nursing homes are one of the most vulnerable groups during the severe acute syndrome coronavirus 2 (SARS-CoV-2) pandemic. The aim of this study was to characterize cellular and humoral immune responses in >70-year-old participants before vaccination, after first and second vaccination with BNT162b2, in contrast to second-dose-vaccinated participants younger than 60 years. Methods: Peripheral blood mononuclear cells of 45 elderly and 40 younger vaccinees were analyzed by IFNγ ELISpot, specific immunoglobulin G antibody titers against SARS-CoV-2 spike protein, and neutralization abilities against SARS-CoV-2 wild-type (WT) and Delta variant (B.1.617.2). Results: Our results clearly demonstrate a significantly increased T cell response, IgG titers, and neutralization activities against SARS-CoV-2 WT and Delta between first and second vaccination with BNT162b2 in elderly vaccinees, thereby highlighting the importance of the second booster. Interestingly, similar cellular and humoral immune responses against SARS-CoV-2 WT and Delta were found after the second vaccine dose in the young and elderly groups. Conclusions: Our data demonstrate a full picture of cellular and humoral immune responses of BNT162b2-vaccinees in two age cohorts. In all vaccines, SARS-CoV-2 WT-specific antibodies with similar neutralizing activity were detected in all vaccinees. After the second vaccination, neutralization titers against SARS-CoV-2 Delta were impaired in both age groups compared with SARS-CoV-2 WT, thereby emphasizing the need for an additional booster to overcome rising variants of SARS-CoV-2.

Comparative analyses of IgG/IgA neutralizing effects induced by three COVID-19 vaccines against variants of concern.

BACKGROUND: Few studies have directly compared virus-specific antibodies and their neutralizing capacity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) wild type (WT) and circulating variants of concern despite the reported high efficacy of messenger RNA (mRNA)- and vector-based vaccines. OBJECTIVE: We assessed SARS-CoV-2 spike protein region 1 (S1)-specific antibodies of BNT162b2, mRNA-1273, and ChAdOx1 vaccinated as well as convalescent coronavirus disease 2019 (COVID-19) patients. We also determined the neutralization ability against SARS-CoV-2 WT and B.1.1.7 (Alpha), B1.1.7 E484K (Alpha-E484K), B.1.351 (Beta), and B.1.617.2 (Delta) variants. METHODS: Serum samples of 107 fully vaccinated or convalescent individuals were analyzed for anti-SARS-CoV-2-S1 IgG and IgA as well as for total anti-SARS-CoV-2 receptor binding domain Ig. Furthermore, neutralization capacity as 50% and 90% neutralization titer values against SARS-CoV-2 WT virus and circulating variants were determined. RESULTS: We observed a robust IgG response in all participants; however, the highest titers were detected in mRNA-based vaccine recipients. In case of serum IgA responses, the difference between mRNA- and vector-based vaccines or convalescent patients was even more pronounced. Interestingly, all 3 vaccines could neutralize all tested variants of concern in addition to WT virus, but in some individuals, only low or no neutralization, especially against Alpha-E484K and the Delta variant, was detected. CONCLUSION: Our study of the efficacy of various COVID-19 vaccines found that mRNA-1273 had the highest neutralization abilities compared to BNT162b2 and ChAdOx1. COVID-19 convalescent patients demonstrated the most heterogeneous range of antibody titers and neutralization abilities, making it hard to assess protection. Furthermore, a significant positive relation between antibodies and the 50% neutralization titer values for immunized and convalescent individuals was determined.

Improvement of Atopic Dermatitis by Synbiotic Baths.

Atopic dermatitis (AD) is a widespread chronic inflammatory dermatologic disorder. This randomized, double-blind study aims to evaluate the effect of synbiotic baths with a defined mixture of six viable lactic acid bacteria (LAB) and prebiotics, without bacteria and prebiotics and placebo baths without prebiotics and bacteria to treat AD patients over a period of 14 days. Therefore, AD patients were randomly assigned into three groups using synbiotic (n = 7), prebiotics (n = 8) or placebo baths (n = 7). Severity of AD was evaluated over time by using severity scoring of atopic dermatitis (SCORAD) and by patient questionnaires. In addition, microbiome on eczematous skin surface was sampled by swaps from each patient before the bath treatment, and after 9, 11 and 14 days of bath treatment. Thereafter, nucleic acids were extracted and the bacterial 16S rRNA gene was amplified via PCR for subsequent amplicon sequencing. Results showed a significantly reduced SCORAD over time of AD patients after daily synbiotic or prebiotic baths. Moreover, AD patients after daily synbiotic baths had a significantly improved pruritus and skin dryness and their bacterial microbiome was enriched by LAB. Taken together, a synbiotic bath is a promising topical skin application to alleviate AD.

Facile and Reliable Emission-Based Nanomolar Anion Sensing by Luminescent Iridium Receptors Featuring Chelating Halogen-Bonding Sites.

An anion sensor is presented that combines a bidentate hydrogen- (HB) or halogen-bonding (XB) site with a luminescent monocationic Ir fragment for strong binding of common anions (Ka up to 6×104 m-1 ) with diagnostic emission changes. A new emission-based protocol for fast and reliable detection was derived on the basis of correction for systematic but unspecific background effects. Such a simple correction routine circumvents the hitherto practical limitations of systematic emission-based analysis of anion binding with validated open-source software (BindFit). The anticipated order of Ka values was obeyed according to size and basicity of the anions (Cl>Br=OAc) as well as the donor atom of the receptor (XB: 6×104 m-1 > HB: 5×103 m-1 ), and led to submicromolar limits of detection within minutes. The results were further validated by advanced NMR techniques, and corroborated by X-ray crystallographic data and DFT analysis, which reproduced the structural and electronic features in excellent agreement. The results suggest that corrected emission-based sensing may become a complementary, reliable, and fast tool to promote the use of XB in various application fields, due to the simple and fast optical determination at high dilution.

Towards Covalent Photosensitizer-Polyoxometalate Dyads-Bipyridyl-Functionalized Polyoxometalates and Their Transition Metal Complexes.

A triol-functionalized 2,2'-bipyridine (bpy) derivative has been synthesized and used for the tris-alkoxylation of polyoxometalate (POM) precursors. The resultant POM-bpy conjugates of the Wells-Dawson- and Anderson-type feature a C-C bond as a linkage between the POM and bpy fragments. This structural motif is expected to increase the hydrolytic stability of the compounds. This is of particular relevance with respect to the application of POM-bpy metal complexes, as photocatalysts, in the hydrogen-evolution reaction (HER) in an aqueous environment. Accordingly, Rh(III) and Ir(III) complexes of the POM-bpy ligands have been prepared and characterized. These catalyst-photosensitizer dyads have been analyzed with respect to their electrochemical and photophysical properties. Cyclic and square-wave voltammetry, as well as UV/vis absorption and emission spectroscopy, indicated a negligible electronic interaction of the POM and metal-complex subunits in the ground state. However, emission-quenching experiments suggested an efficient intramolecular electron-transfer process from the photo-excited metal centers to the POM units to account for the non-emissive nature of the dyads (thus, suggesting a strong interaction of the subunits in the excited state). In-depth photophysical investigations, as well as a functional characterization, i.e., the applicability in the HER reaction, are currently ongoing.

High-Yielding Syntheses of Multifunctionalized RuII Polypyridyl-Type Sensitizer: Experimental and Computational Insights into Coordination.

RuII complexes based on functionalized 2,6-di(quinolin-8-yl)pyridine (dqp) ligands feature excellent photophysical and geometrical properties, thus suggesting dqp ligands as ideal surrogates for 2,2'-bipyridine (bpy) or 2,2':6',2″-terpyridine (tpy). However, the synthesis of multifunctionalized [Ru(dqp)2]2+-based complexes is often low-yielding, which has hampered their practical value to date. In this study, a universal high-yielding route was explored and corroborated by a mechanistic investigation based on 1H NMR, MS, and density functional theory. With application of high-boiling but less-coordinating solvents (i.e., DMF) during the coordination of dqp by the precursor [Ru(dqp)(MeCN)3]2+, the required reaction temperature is lowered considerably (by 30 °C). In comparison to tpy, the reaction rate for dqp is further reduced which is assigned to the higher steric demand upon the coordination process. Namely, the onset of coordination of a tpy derivative at 60 °C and of dqp at 90 °C is significantly milder than in previous protocols. The versatility of the procedure is demonstrated by the high-yielding syntheses of multifunctionalized RuII complexes reaching up to 90%, whereby the presence of hydroxyl groups and losses during purification may lower the isolated yields substantially. In addition, the same strategy of high-boiling but less-coordinating solvents enabled a milder one-pot protocol to prepare [Ru(dqp)2]2+ from a [Ru(MeCN)6]2+ source, i.e., without the need for in situ reduction or halide abstraction as typical for RuIIICl3 hydrate. Hence, the developed protocol benefits from an improved thermal tolerance of sensitive functional groups, which may be applicable also to related polypyridyl-type ligands.

"Chemistry-on-the-complex": functional RuII polypyridyl-type sensitizers as divergent building blocks.

Ruthenium polypyridyl type complexes are potent photoactive compounds, and have found - among others - a broad range of important applications in the fields of biomedical diagnosis and phototherapy, energy conversion schemes such as dye-sensitized solar cells (DSSCs) and molecular assemblies for tailored photo-initiated processes. In this regard, the linkage of RuII polypyridyl-type complexes with specific functional moieties is highly desirable to enhance their inherent photophysical properties, e.g., with a targeting function to achieve cell selectivity, or with a dye or redox-active subunits for energy- and electron-transfer. However, the classical approach of performing ligand syntheses first and the formation of Ru complexes in the last steps imposes synthetic limitations with regard to tolerating functional groups or moieties as well as requiring lengthy convergent routes. Alternatively, the diversification of Ru complexes after coordination (termed "chemistry-on-the-complex") provides an elegant complementary approach. In addition to the Click chemistry concept, the rapidly developing synthesis and purification methodologies permit the preparation of Ru conjugates via amidation, alkylation and cross-coupling reactions. In this regard, recent developments in chromatography shifted the limits of purification, e.g., by using new commercialized surface-modified silica gels and automated instrumentation. This review provides detailed insights into applying the "chemistry-on-the-complex" concept, which is believed to stimulate the modular preparation of unpreceded molecular assemblies as well as functional materials based on Ru-based building blocks, including combinatorial approaches.

Determination of the clean-up efficiency of the solid-phase extraction of rosemary extracts: Application of full-factorial design in hyphenation with Gaussian peak fit function.

We present a novel method for the quantitative determination of the clean-up efficiency to provide a calculated parameter for peak purity through iterative fitting in conjunction with design of experiments. Rosemary extracts were used and analyzed before and after solid-phase extraction using a self-fabricated mixed-mode sorbent based on poly(N-vinylimidazole/ethylene glycol dimethacrylate). Optimization was performed by variation of washing steps using a full three-level factorial design and response surface methodology. Separation efficiency of rosmarinic acid from interfering compounds was calculated using an iterative fit of Gaussian-like signals and quantifications were performed by the separate integration of the two interfering peak areas. Results and recoveries were analyzed using Design-Expert® software and revealed significant differences between the washing steps. Optimized parameters were considered and used for all further experiments. Furthermore, the solid-phase extraction procedure was tested and compared with commercial available sorbents. In contrast to generic protocols of the manufacturers, the optimized procedure showed excellent recoveries and clean-up rates for the polymer with ion exchange properties. Finally, rosemary extracts from different manufacturing areas and application types were studied to verify the developed method for its applicability. The cleaned-up extracts were analyzed by liquid chromatography with tandem mass spectrometry for detailed compound evaluation to exclude any interference from coeluting molecules.

A multidonor-photosensitizer-multiacceptor triad for long-lived directional charge separation.

The modular assembly of a directional photoredox-active multidonor-photosensitizer-multiacceptor (Dn-P-Am) architecture is presented. The triad assembly features a central Ru(ii) sensitizer equipped with pendant polymer chains consisting of multiple triarylamine (pTARA) and naphthalene diimide (pNDI) units, respectively. Upon excitation, the efficient formation (>96%) of charge separation (CS) was observed featuring similar CS lifetimes (400 ns) as related molecular triads. In contrast, a significant additional longer-lived CS component (2400 ns, 30%) is observed indicating multiple contributing pathways.

Extending Long-lived Charge Separation Between Donor and Acceptor Blocks in Novel Copolymer Architectures Featuring a Sensitizer Core.

A bifunctional RuII photosensitizer unit was decorated with one n- and one p-type polymer chain to form precisely controlled hierarchical copolymer-type architectures for light-induced charge separation. The applied modular chemistry-on-the-complex strategy benefits from separately prepared building blocks and their orthogonal linkage in the two final assembly steps. Upon visible light absorption, electron transfer is initiated between the conjugated poly(3,6-carbazole) chain and the styrenic poly(naphthalene diimide) segments. Steady-state and time-resolved spectroscopy show complete charge separation within a few nanoseconds (>95 % efficiency) persisting several tens of microseconds. The recombination is significantly reduced in comparison to low-molecular model systems or to non-conjugated congeners, reflecting the higher charge mobility in conjugated polymers. In summary, the modularity of the presented approach is expected to serve as a versatile platform to tailor the interface between the charge transport domains in a systematic fashion.

Asymmetric Cyclometalated RuII Polypyridyl-Type Complexes with π-Extended Carbanionic Donor Sets.

A series of novel cyclometalated RuII complexes were investigated featuring the tridentate dqp ligand platform (dqp is 2,6-di(quinolin-8-yl)pyridine), in order to utilize the octahedral coordination mode around the Ru center to modulate the electrochemical and photophysical properties. The heteroleptic complexes feature C1 symmetry due to symmetry breaking by the peripheral five- or six-membered carbanionic chelate (phenyl, naphthyl, or anthracenyl units). The chelation mode is controlled by the steric effects and C-H activation selectivity of the ligand, which prompted the development of a general synthesis protocol. The optimized conditions to achieve high overall yields (55-75%) involve NaHCO3 as the base and an simplified purification protocol: i.e., facile chromatographic separation using commercially available amino-functionalized silica applying nonaqueous salt-free conditions to omit the necessity of counterion exchange. The structural, photophysical, and electrochemical properties were studied in depth, and the results were corroborated by density functional theory (DFT) calculations. Steady state and time-resolved spectroscopy revealed red-shifted absorption (up to 750 nm) and weak IR emission (800-1000 nm) combined with prolonged emission lifetimes (up to 20 ns) in comparison to classical tpy-based (tpy is 2,2':6',2″-terpyridine) complexes. An enhanced stability was observed by blocking the reactive positions of the carbanionic ligand framework, while the reactive positions may be exploited for further functionalization.

Synthetic approaches towards structurally-defined electrochemically and (photo)redox-active polymer architectures.

Electrochemically active polymers are widely used in (opto)electronic applications, e.g. organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), solar cells or other light harvesting devices. In this regard, the progress in controlled polymerization techniques opens new possibilities to construct covalently linked polymer architectures, e.g. block copolymers or graft copolymers, from defined building blocks. These architectures represent promising candidates for application in (opto)electronic devices as they allow control of the morphology through self-assembly processes and, furthermore, are capable of mimicking fundamental processes for directional charge transport or light harvesting. This review details synthetic approaches to prepare functional redox-active and conjugated homopolymers as well as the construction of covalently linked well-defined architectures thereof, e.g. block copolymers, graft copolymers or chain end functionalized assemblies.