Uncovering the mechanism of selective stabilization of high-energy diastereoisomers via inclusion.

Supramolecular systems may be used to stabilize otherwise unstable isomers to find alternative synthetic pathways. It has been reported that cucurbit[8]uril can stabilize trans-I and trans-II CuII cyclam, whereas trans-III is the only non-substituted trans CuII cyclam diastereoisomer found outside of the host molecule experimentally. Quantum chemistry methods can provide valuable insight into the intermolecular interactions involved in these inclusion complexes. All five possible trans diastereoisomers of CuII cyclam were studied within the host molecule to calculate the interaction energy and free energy of association for each complex. The relative free energies of the five free cyclams confirm that trans-I and trans-II are the most energetically accessible diastereoisomers from the initial trans-III starting point. Energy decomposition analysis was used to identify the attractive and repulsive interactions between cyclam and cucurbit[8]uril and showed that trans-II encounters repulsive forces almost three times greater than trans-I, which may explain the 7:3 ratio of trans-I to trans-II within cucurbit[8]uril that occurs experimentally. Optimized complex geometries with trans-III, IV, and V show that the cyclams protrude out of cucurbit[8]uril, whereas trans-I and trans-II become more encapsulated and elongate the host, suggesting that the position of the cyclam is extremely important when forming non-covalent interactions. Our results agree with the experimental findings and provide greater insight into why the most stable isolated cyclam diastereoisomer, trans-III, does not form a complex. Supplementary Information: The online version contains supplementary material available at 10.1007/s00214-023-03077-7.

Elucidating the Role of Optical Activity of Polymers in Protein-Polymer Interactions.

Proteins are biomolecules with potential applications in agriculture, food sciences, pharmaceutics, biotechnology, and drug delivery. Interactions of hydrophilic and biocompatible polymers with proteins may impart proteolytic stability, improving the therapeutic effects of biomolecules and also acting as excipients for the prolonged storage of proteins under harsh conditions. The interactions of hydrophilic and stealth polymers such as poly(ethylene glycol), poly(trehalose), and zwitterionic polymers with various proteins are well studied. This study evaluates the molecular interactions of hydrophilic and optically active poly(vitamin B5 analogous methacrylamide) (poly(B5AMA)) with model proteins by fluorescence spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and circular dichroism (CD) spectroscopy analysis. The optically active hydrophilic polymers prepared using chiral monomers of R-(+)- and S-(-)-B5AMA by the photo-iniferter reversible addition fragmentation chain transfer (RAFT) polymerization showed concentration-dependent weak interactions of the polymers with bovine serum albumin and lysozyme proteins. Poly(B5AMA) also exhibited a concentration-dependent protein stabilizing effect at elevated temperatures, and no effect of the stereoisomers of polymers on protein thermal stability was observed. NMR analysis, however, showed poly(B5AMA) stereoisomer-dependent changes in the secondary structure of proteins.

COVID-19 pandemic-related change in racial and ethnic disparities in exclusive breastmilk feeding during the delivery hospitalization: a differences-in-differences analysis.

OBJECTIVE: Exclusive breastmilk feeding during the delivery hospitalization, a Joint Commission indicator of perinatal care quality, is associated with longer-term breastfeeding success. Marked racial and ethnic disparities in breastfeeding exclusivity and duration existed prior to COVID-19. The pandemic, accompanied by uncertainty regarding intrapartum and postpartum safety practices, may have influenced disparities in infant feeding practices. Our objective was to examine whether the first wave of the COVID-19 pandemic in New York City was associated with a change in racial and ethnic disparities in exclusive breastmilk feeding during the delivery stay. METHODS: We conducted a cross-sectional study of electronic medical records from 14,964 births in two New York City hospitals. We conducted a difference-in-differences (DID) analysis to compare Black-white, Latina-white, and Asian-white disparities in exclusive breastmilk feeding in a pandemic cohort (April 1-July 31, 2020, n=3122 deliveries) to disparities in a pre-pandemic cohort (January 1, 2019-February 28, 2020, n=11,842). We defined exclusive breastmilk feeding as receipt of only breastmilk during delivery hospitalization, regardless of route of administration. We ascertained severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection status from reverse transcription-polymerase chain reaction tests from nasopharyngeal swab at admission. For each DID model (e.g. Black-white disparity), we used covariate-adjusted log binomial regression models to estimate racial and ethnic risk differences, pandemic versus pre-pandemic cohort risk differences, and an interaction term representing the DID estimator. RESULTS: Exclusive breastmilk feeding increased from pre-pandemic to pandemic among white (40.8% to 46.6%, p<0.001) and Asian (27.9% to 35.8%, p=0.004) women, but not Black (22.6% to 25.3%, p=0.275) or Latina (20.1% to 21.4%, p=0.515) women overall. There was an increase in the Latina-white exclusive breastmilk feeding disparity associated with the pandemic (DID estimator=6.3 fewer cases per 100 births (95% CI=-10.8, -1.9)). We found decreased breastmilk feeding specifically among SARS-CoV-2 positive Latina women (20.1% pre-pandemic vs. 9.1% pandemic p=0.013), and no change in Black-white or Asian-white disparities. CONCLUSIONS: We observed a pandemic-related increase in the Latina-white disparity in exclusive breastmilk feeding, urging hospital policies and programs to increase equity in breastmilk feeding and perinatal care quality during and beyond this health emergency.

The clinical utility of magnetic resonance imaging as an adjunct to ultrasound in the diagnosis of placenta accreta spectrum disorders.

OBJECTIVES: To determine if the use of magnetic resonance imaging (MRI) changes the diagnosis of placenta accreta spectrum (PAS) made on prenatal ultrasound (US) leading to an improvement in clinical outcomes. METHODS: This was a retrospective chart review of all patients with evidence of PAS on US from 2012 to 2018 in one tertiary care medical center with subsequent use of MRI of the uterus to confirm diagnosis. The type of PAS classified by imaging was compared between US and MRI, with a final diagnosis made using histology. Outcomes that were analyzed included the following: 1) MRI correctly changed diagnosis, 2) MRI incorrectly downgraded diagnosis, 3) MRI incorrectly upgraded diagnosis, and 4) MRI did not change diagnosis. A T-test and Chi-squared test were performed to compare the clinical outcomes of patients with an upgraded diagnosis by MRI to those whose diagnosis was downgraded or stayed the same. RESULTS: Forty-one patients received an MRI to validate the diagnosis of PAS after ultrasound and are included in the analysis. MRI changed the diagnosis in 36.6% (15/41) patients, correctly changing the diagnosis in 22% (9/41) and incorrectly upgrading the diagnosis in 14.6% (6/41). Patients whose diagnosis was upgraded by MRI (either correctly or incorrectly) were more likely to deliver earlier compared to those who were either downgraded or had no change in their diagnosis [33. 2 ± 3. 5 weeks vs 35. 2 ± 2. 9 weeks, p = 0.05]. Patients who were upgraded were more likely to have interventional radiology and/or urology involvement at the time of delivery [91.7% (11/12) vs 25. 9% (7/27), p = 0.001]. There were no complications from these procedures. CONCLUSION: The use of MRI incorrectly changed the diagnosis as much as it correctly changed the diagnosis of PAS after US. MRI should not be used routinely as a clinical adjunct to ultrasound in the diagnosis of placenta accreta spectrum.

Corrigendum to: Hepatitis C Seroprevalence Among Consecutive Labor and Delivery Admissions in Two New York City Hospitals.

[This corrects the article DOI: 10.1093/ofid/ofaa514.].

Racial/Ethnic Disparities in Very Preterm Birth and Preterm Birth Before and During the COVID-19 Pandemic.

Importance: The coronavirus disease 2019 (COVID-19) pandemic may exacerbate existing racial/ethnic inequities in preterm birth. Objective: To assess whether racial/ethnic disparities in very preterm birth (VPTB) and preterm birth (PTB) increased during the first wave of the COVID-19 pandemic in New York City. Design, Setting, and Participants: This cross-sectional study included 8026 Black, Latina, and White women who gave birth during the study period. A difference-in-differences (DID) analysis of Black vs White disparities in VPTB or PTB in a pandemic cohort was compared with a prepandemic cohort by using electronic medical records obtained from 2 hospitals in New York City. Exposures: Women who delivered from March 28 to July 31, 2020, were considered the pandemic cohort, and women who delivered from March 28 to July 31, 2019, were considered the prepandemic cohort. Reverse transcription-polymerase chain reaction tests for the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were performed using samples obtained via nasopharyngeal swab at the time of admission. Main Outcomes and Measures: Clinical estimates of gestational age were used to calculate VPTB (<32 weeks) and PTB (<37 weeks). Log binomial regression was performed to estimate Black vs White risk differences, pandemic cohort vs prepandemic cohort risk difference, and an interaction term representing the DID estimator. Covariate-adjusted models included age, insurance, prepregnancy body mass index, and parity. Results: Of 3834 women in the pandemic cohort, 492 (12.8%) self-identified as Black, 678 (17.7%) as Latina, 2012 (52.5%) as White, 408 (10.6%) as Asian, and 244 (6.4%) as other or unspecified race/ethnicity, with approximately half the women 25 to 34 years of age. The prepandemic cohort comprised 4192 women with similar sociodemographic characteristics. In the prepandemic cohort, VPTB risk was 4.4% (20 of 451) and PTB risk was 14.4% (65 of 451) among Black infants compared with 0.8% (17 of 2188) VPTB risk and 7.1% (156 of 2188) PTB risk among White infants. In the pandemic cohort, VPTB risk was 4.3% (21 of 491) and PTB risk was 13.2% (65 of 491) among Black infants compared with 0.5% (10 of 1994) VPTB risk and 7.0% (240 of 1994) PTB risk among White infants. The DID estimators indicated that no increase in Black vs White disparities were found (DID estimator for VPTB, 0.1 additional cases per 100 [95% CI, -2.5 to 2.8]; DID estimator for PTB, 1.1 fewer case per 100 [95% CI, -5.8 to 3.6]). The results were comparable in covariate-adjusted models when limiting the population to women who tested negative for SARS-CoV-2. No change was detected in Latina vs White PTB disparities during the pandemic. Conclusions and Relevance: In this cross-sectional study of women who gave birth in New York City during the COVID-19 pandemic, no evidence was found for increased racial/ethnic disparities in PTB, among women who tested positive or tested negative for SARS-CoV-2.

Hepatitis C Seroprevalence Among Consecutive Labor and Delivery Admissions in Two New York City Hospitals.

BACKGROUND: Rates of hepatitis C virus (HCV) among women of childbearing age have increased as a result of the opioid epidemic, especially in the nonurban white population. Recently updated US Preventative Services Task Force and Centers for Disease Control and Prevention guidance have recommended universal HCV screening during pregnancy, but obstetrics societies have not yet endorsed this recommendation. We evaluated the seroprevalence of HCV among pregnant women in an inner-city population, compared rates with other sexually transmitted infections (STIs) screened for during pregnancy, and evaluated factors associated with HCV positivity. METHODS: We performed a prospective seroprevalence study of consecutive labor and delivery admissions (both antepartum complications and delivery admissions) by testing serum samples for HCV antibody over 9 months at 2 major hospital settings in New York City. RESULTS: Fifty-six of 7373 (0.75%; 95% confidence interval [CI], 0.57-0.98) patients screened positive for HCV, with 28 of 4013 (0.70%; 95% CI, 0.46%-1.01%) and 28 of 3413 (0.82%; 95% CI, 0.55%-1.18%) at each hospital. Forty-one percent of HCV-positive patients had any reported HCV risk factors. Hepatitis C virus-positive patients were less likely to have private insurance and more likely to have a history of cannabis, cocaine, and injection drug use (P < .001). The HCV rates were higher among antepartum admissions compared with delivery admissions and higher than that of hepatitis B virus (0.65%; 95% CI, 0.48-0.86), human immunodeficiency virus (0.27%; 95% CI, 0.16-0.42), and syphilis (0.16%; 95% CI, 0.08-0.28). CONCLUSIONS: We found a higher than expected HCV seroprevalence among pregnant women and higher than most other STIs routinely screened for in pregnancy. Most patients had no risk factors. These findings support universal screening for hepatitis C during pregnancy.

Photophysical Properties of Donor-Acceptor Stenhouse Adducts and Their Inclusion Complexes with Cyclodextrins and Cucurbit[7]uril.

Donor-acceptor Stenhouse adducts (DASAs) are a novel class of solvatochromic photoswitches with increasing importance in photochemistry. Known for their reversibility between open triene and closed cyclized states, these push-pull molecules are applicable in a suite of light-controlled applications. Recent works have sought to understand the DASA photoswitching mechanism and reactive state, as DASAs are vulnerable to irreversible "dark switching" in polar protic solvents. Despite the utility of fluorescence spectroscopy for providing information regarding the electronic structure of organic compounds and gaining mechanistic insight, there have been few studies of DASA fluorescence. Herein, we characterize various photophysical properties of two common DASAs based on Meldrum's acid and dimethylbarbituric acid by fluorescence spectroscopy. This approach is applied in tandem with complexation by cyclodextrins and cucurbiturils to reveal the zwitterionic charge separation of these photoswitches in aqueous solution and the protective nature of supramolecular complexation against degradative dark switching. DASA-M, for example, was found to form a weak host-guest inclusion complex with (2-hydroxypropyl)-γ-cyclodextrin, with a binding constant K = 60 M-1, but a very strong inclusion complex with cucurbit[7]uril, with K = 27,000 M-1. This complexation within the host cavity was found to increase the half-life of both DASAs in aqueous solution, indicating the significant and potentially useful stabilization of these DASAs by host encapsulation.

Characteristics and Outcomes of 241 Births to Women With Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection at Five New York City Medical Centers.

OBJECTIVE: To describe the characteristics and birth outcomes of women with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection as community spread in New York City was detected in March 2020. METHODS: We performed a prospective cohort study of pregnant women with laboratory-confirmed SARS-CoV-2 infection who gave birth from March 13 to April 12, 2020, identified at five New York City medical centers. Demographic and clinical data from delivery hospitalization records were collected, and follow-up was completed on April 20, 2020. RESULTS: Among this cohort (241 women), using evolving criteria for testing, 61.4% of women were asymptomatic for coronavirus disease 2019 (COVID-19) at the time of admission. Throughout the delivery hospitalization, 26.5% of women met World Health Organization criteria for mild COVID-19, 26.1% for severe, and 5% for critical. Cesarean birth was the mode of delivery for 52.4% of women with severe and 91.7% with critical COVID-19. The singleton preterm birth rate was 14.6%. Admission to the intensive care unit was reported for 17 women (7.1%), and nine (3.7%) were intubated during their delivery hospitalization. There were no maternal deaths. Body mass index (BMI) 30 or higher was associated with COVID-19 severity (P=.001). Nearly all newborns tested negative for SARS-CoV-2 infection immediately after birth (97.5%). CONCLUSION: During the first month of the SARS-CoV-2 outbreak in New York City and with evolving testing criteria, most women with laboratory-confirmed infection admitted for delivery did not have symptoms of COVID-19. Almost one third of women who were asymptomatic on admission became symptomatic during their delivery hospitalization. Obesity was associated with COVID-19 severity. Disease severity was associated with higher rates of cesarean and preterm birth.

Testing of Patients and Support Persons for Coronavirus Disease 2019 (COVID-19) Infection Before Scheduled Deliveries.

OBJECTIVE: To evaluate the rate of coronavirus disease 2019 (COVID-19) infection with the use of universal testing in our obstetric population presenting for scheduled deliveries, as well as the concordance or discordance rate among their support persons during the initial 2-week period of testing. Additionally, we assessed the utility of a screening tool in predicting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing results in our cohort. METHODS: This was an observational study in which all women who were scheduled for a planned delivery within the Mount Sinai Health system from April 4 to April 15, 2020, were contacted and provided with an appointment for themselves as well as their support persons to undergo COVID-19 testing 1 day before their scheduled delivery. Both the patients and the support persons were administered a standardized screen specific for COVID-19 infection by telephone interview. Those support persons who screened positive were not permitted to attend the birth. All patients and screen-negative support persons underwent SARS-CoV-2 testing. RESULTS: During the study period, 155 patients and 146 support persons underwent SARS-CoV-2 testing. The prevalence of asymptomatic COVID-19 infection was 15.5% (CI 9.8-21.2%) and 9.6% (CI 4.8-14.4%) among patients and support persons, respectively. The rate of discordance among tested pairs was 7.5%. Among patients with COVID-19 infection, 58% of their support persons also had infection; in patients without infection, fewer than 3.0% of their support persons had infection. CONCLUSION: We found that more than 15% of asymptomatic maternity patients tested positive for SARS-CoV-2 infection despite having screened negative with the use of a telephone screening tool. Additionally, 58% of their asymptomatic, screen-negative support persons also tested positive for SARS-CoV-2 infection. Alternatively, testing of the support persons of women who had tested negative for COVID-19 infection had a low yield for positive results. This has important implications for obstetric and newborn care practices as well as for health care professionals.

Detection and Identification of Reaction Intermediates in the Photorearrangement of Pyridazine N-Oxide: Discrepancies between Experiment and Theory.

Photolysis of pyridazine N-oxide (PNO) results in the detection of a complex series of transient phenomena. On the ultrafast (fs) timescale, we could detect the decay of the first singlet excited state of PNO and the formation of a short-lived transient species, which, based on its time-resolved resonance Raman (TR3) spectrum, we assign to oxaziridine 1,2-diaza-7-oxa-bicyclo[4.1.0]hepta-2,4-diene. On a longer (hundreds of ns) timescale, this species rearranges to a ring-opened diazo compound, which we have also detected by time-resolved infrared and TR3 spectroscopy. In addition, we identify 1-oxa-3,4-diazepine as a long-lived species formed in the photochemistry of PNO. This species is formed via its oxirane isomer, which in turn is likely formed directly from the S1 state of PNO via a conical intersection. The barrier determined experimentally for the decay of 1,2-diaza-7-oxa-bicyclo[4.1.0]hepta-2,4-diene (Ea = (7.1 ± 0.5) kcal mol-1) is far larger than any barrier calculated by any method that includes dynamic electron correlation but very close to the barriers calculated at the RHF or CASSCF levels of theory. Many methods (B3LYP, MP2, and MP4) fail to give a minimum structure for 1,2-diaza-7-oxa-bicyclo[4.1.0]hepta-2,4-diene, while M06, M06-2X, MP3, CCSD, or CCSD(T) yield activation energies for its electrocyclic ring opening that are far too small. In addition, we note that several important geometric parameters, both of 1,2-diaza-7-oxa-bicyclo[4.1.0]hepta-2,4-diene and of the transition state of its ring opening reaction, clearly have reached no convergence, even at the fully optimized CCSD(T)/cc-pVTZ level of theory. We therefore suggest that the transient species described in this contribution might be excellent test molecules for further development of highly correlated and density functional theory methods.

Measuring porosities of chromatographic columns utilizing a mass-based total pore-blocking method: Superficially porous particles and pore-blocking critical pressure mechanism.

Experimentally determined total, interstitial and intraparticle porosity values are necessary to equate theory, simulation and experimental column performance. This paper reports a study of a mass-based technique for determining total, interstitial and intraparticle porosity measurements based on the total pore-blocking (TPB) method. Commercially available superficially porous particle (SPP) columns, in a variety of small-pore and wide-pore materials, with both hydrophobic and hydrophilic surfaces, are utilized as samples. The results are compared with previously determined literature values for a number of columns and contrasted with HPLC-based elution methods. This method uses only a high-precision balance and an HPLC pump. A simple theoretical analysis of the TPB method using the Young-Laplace equation shows the pressure bounds and flow rate constraints of the method which ensure pore blocking stability. The results suggest that particles with small-pore diameters can be analyzed over a range of solvent clearing pressures and flow rates. However, wide-pore materials, typically with pore diameters in excess of 400 Å, have very low critical pressures and are difficult to determine without losing the pore blocking component. Small mass differences between clearing solvents are shown to present a challenge for measuring the interstitial volume.

Synthesis of Oligo(1,8-pyrenylene)s: A Series of Functional Molecular Liquids.

A monomer-through-pentamer series of oligo(1,8-pyrenylene)s was synthesized using a two-step iterative synthetic strategy. The trimer, tetramer, and pentamer are mixtures of atropisomers that interconvert slowly at room temperature (as shown by variable-temperature NMR analysis). They are liquids well below room temperature, as indicated by POM, DSC and SWAXS analysis. These oligomers are highly fluorescent both in the liquid state and in dilute solution (λF,max = 444-457 nm, φF = 0.80) and an investigation of their photophysical properties demonstrated that delocalization plays a larger role in their excited states than it does in related pyrene-based oligomers.

Advances in Light-Emitting Dendrimers.

The design of dendrimers with various chromophores has attracted significant attention in light of the dual effect of the luminescence of the chromophores and the morphology of the synthesized dendrimers. Recent developments in this field stem from their wide potential applications, including organic light-emitting diodes, photonic switches and upconversion lasers, as well as sensors and electronic devices. The focus of this comprehensive review is on the design and properties of various classes of light-harvesting dendrimeric materials.

Syringoid Eccrine Carcinoma of the Foot: Report of a Rare Cutaneous Adnexal Neoplasm.

Syringoid eccrine carcinoma is a rare malignant adnexal tumor that typically presents in the head and neck region. Involvement of the extremities is uncommon, with only a few cases reported in the literature. Here, we report our experience with a rare case of syringoid eccrine carcinoma occurring on the plantar surface of the right foot in a 47-year-old African American woman. Histologically, incisional biopsy revealed a tumor consisting of tubulocystic structures lined by basaloid cells with an infiltrative growth pattern, extending from the reticular dermis to the deep biopsy margin. Some of the nests and cords of basaloid cells displayed syringoma-like, tadpole morphology. Immunohistochemical analysis showed diffuse immunoreactivity with monoclonal carcinoembryonic antigen, epithelial membrane antigen, cytokeratin 7, S100 protein, and CD117. These morphologic and immunophenotypic features were most consistent with syringoid eccrine carcinoma. Syringoid eccrine carcinoma has a broad differential diagnosis which must be carefully ruled out by morphology, immunohistochemistry, and thorough metastatic survey with imaging studies. Our case highlights the importance of recognizing this rare entity, which is locally destructive and has a propensity for recurrence. To the best of our knowledge, this is the first reported case of syringoid eccrine carcinoma presenting on the sole of the foot.

Superficially porous particles with 1000Å pores for large biomolecule high performance liquid chromatography and polymer size exclusion chromatography.

To facilitate mass transport and column efficiency, solutes must have free access to particle pores to facilitate interactions with the stationary phase. To ensure this feature, particles should be used for HPLC separations which have pores sufficiently large to accommodate the solute without restricted diffusion. This paper describes the design and properties of superficially porous (also called Fused-Core®, core shell or porous shell) particles with very large (1000Å) pores specifically developed for separating very large biomolecules and polymers. Separations of DNA fragments, monoclonal antibodies, large proteins and large polystyrene standards are used to illustrate the utility of these particles for efficient, high-resolution applications.

Factors Affecting the Formation of 2:1 Host:Guest Inclusion Complexes of 2-[(R-Phenyl)amine]-1,4-naphthalenediones (PAN) in ß- and γ-Cyclodextrins.

The molecular hosts cyclodextrins form inclusion complexes with a wide variety of guests, resulting in complexes with various host:guest stoichiometries. In the case of a series of 19 1,4-naphthoquinolines as guests with either ß- or γ-cyclodextrin studied using electrospray mass spectroscopy, in most cases only 1:1 complexes were observed, with 2:1 host:guest complexes observed in just 6 out of 38 host:guest combinations. It is shown that these higher-order complexes were observed only in the case of small (or no) electronically withdrawing substituents, and were much less likely in the case of the larger γ-cyclodextrin host. The size and electronic properties of the substituents involved shows that both steric and electronic factors must be taken into account in predicting which cyclodextrin host:guest stoichiometries will be stable enough to form (or once formed, be robust enough to be observed in the ESI-MS experiments). It is clear that the prediction of host-guest stoichiometry for a specific host-guest pair is complicated, and involves a subtle interplay of both electronic and steric factors. However, there are definite trends, which can be used to help predict host:guest stoichiometry for a given host-guest pair.

Photoinduced Synthesis of Dual-Emissive Tetraphenylethene-Based Dendrimers with Tunable Aggregates and Solution States Emissions.

Photoactive materials are actively researched, piloting breakthroughs that have enriched fundamental understanding of science, and have led to real applications. Tetraphenylethene, a photoactive molecule that is of interest from fundamental and applied perspectives, features photochemical properties that are not exploited in the design of photoactive, dual-emissive materials. Here, tetraphenylethene-based, dual-emissive dendrimers are constructed via a synthetic approach that involves a photochemical reaction that exploits the photochemistry of tetraphenylethene. These dendrimers are emissive in solution and in the aggregate state with tunable dual emissions at 368 and 469 nm. The photochemical reaction also tunes the size of the aggregates, increasing the size after UV irradiation. The reported synthetic strategy is a direct and facile approach to accessing dual-emissive macromolecules, especially tetraphenylethene-based systems for real applications.

Structure-Binding Effects: Comparative Binding of 2-Anilino-6-naphthalenesulfonate by a Series of Alkyl- and Hydroxyalkyl-Substituted ß-Cyclodextrins.

Cyclodextrins (CDs) are the most widely used organic hosts for the inclusion of guest molecules. CDs can be readily modified through substitutions of the hydroxyl groups, and these modified CDs can have different host binding properties compared to those of parent CDs. However, only relatively few systematic studies of the effects of chemical substitution on CD binding ability have been reported thus far. In this paper, we report the study of the binding properties of five different analytically pure modified ß-cyclodextrin (ß-CD) hosts (substituted with alkyl and/or hydroxyalkyl groups) with 2-anilino-6-naphthalenesulfonate (2,6-ANS) as guest. Binding constants for the formation of the inclusion complex between 2,6-ANS and each CD were determined using both fluorescence spectroscopy and capillary electrophoresis. Addition of modified CDs to an aqueous solution of 2,6-ANS resulted in significant enhancement of the fluorescence intensity of 2,6-ANS, as well as a significant spectral blue shift, indicative of inclusion. Inclusion of 2,6-ANS within the CD cavity was confirmed by NMR spectroscopy. Substitution at position 3 decreased the magnitude of the binding constants, while alkyl or hydroxylalkyl substitution of the primary hydroxyl at position 6 increased the magnitude of the binding constant in all cases, in relation with increasing length of the alkyl chain linker. In addition, binding constants decreased with solvent polarity when increasing amounts of methanol were added. Structure-binding correlations for CDs based on these binding constant results are presented and discussed.