Two series of unconventional triazine-based dendrimers with C(2) symmetry and C(3) symmetry were prepared. The newly prepared C(3)-symmetrical dendrimers were characterized by (1)H and (13)C NMR spectroscopy, mass spectrometry, and elemental analysis. Differential scanning calorimetry, polarizing microscopy, and powder XRD showed that the C(3)-symmetrical dendrimers display columnar liquid-crystalline phases during thermal treatment, but the C(2)-symmetrical dendrimers were not observed to behave correspondingly. The molecular conformations of C(3)- and C(2)-symmetrical dendrimers were obtained by computer simulation with the MM2 model of the CaChe program in the gas phase. The simulation results reasonably explain the different mesogenicities of C(3)- and C(2)-symmetric dendrimers. This new strategy should be applicable to other types of unconventional dendrimers with rigid frameworks for displaying columnar liquid-crystalline behavior.

S y n t h e s i s o f T r i a z i n e -B a s e d D e n d r o n s a n d D e n d r i m e r sAbstract: A convenient, efficient and convergent approach to prepare triazine-based dendrons and dendrimers is developed. The steric hindrance resulting from the presence of dioctylamino moieties in the peripheral regions allows the synthesis of soluble dendrons without employing protection and deprotection steps. The triazinebased dendrimers are prepared via reaction of N,N¢-dimethylethane-1,2-diamine with the dendrons in a ratio of 1:2. Interactions of the dendrimers with tetrafluorobenzoquinone led to the appearance of new broad bands, red-shifted by approximately 180 nm, in the absorbance spectra.Dendrimers are highly branched molecules containing central cores, bridging units and peripheral functionalities, and have attracted significant attention in biochemical and optical research. 1 In particular, dendrimers display single molecular weights and thus show interesting and predictable properties. Dendrimers bearing peripheral functional groups such as amino, hydroxy or carboxylate may potentially function as catalytic materials or drugtransporting agents. 2,3 As a result of the void spaces in the dendritic framework, dendrimers may function as porous materials that incorporate guest molecules. 4 However, the synthesis of dendrimers is generally tedious as protection and deprotection strategies are sometimes needed, and extremely poor solubility may be encountered for rigid or conjugated systems. 1,5 In divergent synthetic approaches the protection and deprotection steps may be incomplete, leading to unexpected side reactions affording by-products which co-exist with the dendrimers. 5 This, certainly to a degree, results in difficulties during their purification and characterization.Although there are challenges during their synthesis and subsequent characterization, the development of efficient strategies to prepare novel dendrimers with new peripheral functionalities is attractive. 6 For example, Takagi employed divergent and convergent approaches to prepare dendrimers with an aromatic linkage based on the triazine unit, however, because of the aryl moiety and hydrogen bonding interactions, the dendrimers were much less soluble in organic solvents. 7 Simanek and co-workers applied divergent, convergent and orthogonal methods to prepare triazine-based dendrimers with various functionalities present on the peripheral arms, but protection and deprotection steps were often required in their approaches. 8a Subsequently, the same group synthesized triazinebased dendrimers containing paclitaxcel or N-H functionalities in order to study their transfection efficiency. 8b,c With the increased potential applications of triazine-based dendrimers, the use of various linkers to simplify their synthesis or analysis has been reported. 8d,e Using piperazine as a transannular effect linker, 9 we reported an efficient method to prepare a new series of triazine-based dendrimers via a convergent approach in which protection and deprotectio...

A dendrimer with 3-fold symmetry and piperazinoamido moieties was prepared in ~35% yield. This molecule was observed to exhibit columnar phases on thermal treatment and possess free void space in...

Importance: SARS-CoV-2 infection can result in ongoing, relapsing, or new symptoms or other health effects after the acute phase of infection; termed post-acute sequelae of SARS-CoV-2 infection (PASC), or long COVID. The characteristics, prevalence, trajectory and mechanisms of PASC are ill-defined. The objectives of the Researching COVID to Enhance Recovery (RECOVER) Multi-site Observational Study of PASC in Adults (RECOVER-Adult) are to: (1) characterize PASC prevalence; (2) characterize the symptoms, organ dysfunction, natural history, and distinct phenotypes of PASC; (3) identify demographic, social and clinical risk factors for PASC onset and recovery; and (4) define the biological mechanisms underlying PASC pathogenesis. Methods: RECOVER-Adult is a combined prospective/retrospective cohort currently planned to enroll 14,880 adults aged ≥18 years. Eligible participants either must meet WHO criteria for suspected, probable, or confirmed infection; or must have evidence of no prior infection. Recruitment occurs at 86 sites in 33 U.S. states, Washington, DC and Puerto Rico, via facility- and community-based outreach. Participants complete quarterly questionnaires about symptoms, social determinants, vaccination status, and interim SARS-CoV-2 infections. In addition, participants contribute biospecimens and undergo physical and laboratory examinations at approximately 0, 90 and 180 days from infection or negative test date, and yearly thereafter. Some participants undergo additional testing based on specific criteria or random sampling. Patient representatives provide input on all study processes. The primary study outcome is onset of PASC, measured by signs and symptoms. A paradigm for identifying PASC cases will be defined and updated using supervised and unsupervised learning approaches with cross-validation. Logistic regression and proportional hazards regression will be conducted to investigate associations between risk factors, onset, and resolution of PASC symptoms. Discussion: RECOVER-Adult is the first national, prospective, longitudinal cohort of PASC among US adults. Results of this study are intended to inform public health, spur clinical trials, and expand treatment options.

-tetraalkyaminoazoxybenzene derivatives were conveniently prepared by the coupling of N,N-dialkylnitrosoaniline in the presence of acetone and KOH. The reaction mechanism was proposed and investigated, and the structure of compound 3b was also confirmed by single crystal X-ray diffractometry.