Measuring the predictability of life outcomes with a scientific mass collaboration.

How predictable are life trajectories? We investigated this question with a scientific mass collaboration using the common task method; 160 teams built predictive models for six life outcomes using data from the Fragile Families and Child Wellbeing Study, a high-quality birth cohort study. Despite using a rich dataset and applying machine-learning methods optimized for prediction, the best predictions were not very accurate and were only slightly better than those from a simple benchmark model. Within each outcome, prediction error was strongly associated with the family being predicted and weakly associated with the technique used to generate the prediction. Overall, these results suggest practical limits to the predictability of life outcomes in some settings and illustrate the value of mass collaborations in the social sciences

G-quadruplex organic frameworks

Two-dimensional covalent organic frameworks often π stack into crystalline solids that allow precise spatial positioning of molecular building blocks. Inspired by the hydrogen-bonded G-quadruplexes found frequently in guanine-rich DNA, here we show that this structural motif can be exploited to guide the self-assembly of naphthalene diimide and perylene diimide electron acceptors end-capped with two guanine electron donors into crystalline G-quadruplex-based organic frameworks, wherein the electron donors and acceptors form ordered, segregated π-stacked arrays. Time-resolved optical and electron paramagnetic resonance spectroscopies show that photogenerated holes and electrons in the frameworks have long lifetimes and display recombination kinetics typical of dissociated charge carriers. Moreover, the reduced acceptors form polarons in which the electron is shared over several molecules. The G-quadruplex frameworks also demonstrate potential as cathode materials in Li-ion batteries because of the favourable electron- and Li-ion-transporting capacity provided by the ordered rylene diimide arrays and G-quadruplex structures, respectively

DNA Glycosylases Involved in Base Excision Repair May Be Associated with Cancer Risk in BRCA1 and BRCA2 Mutation Carriers

Peer reviewe

Fast Triplet Formation via Singlet Exciton Fission in a Covalent Perylenediimide-β-apocarotene Dyad Aggregate

A covalent dyad was synthesized in which perylene-3,4,:9:10-bis­(dicarboximide) (PDI) is linked to β-apocarotene (Car) using a biphenyl spacer. The dyad is monomeric in toluene and forms a solution aggregate in methylcyclohexane (MCH). Using femtosecond transient absorption (fsTA) spectroscopy, the monomeric dyad and its aggregates were studied both in solution and in thin films. In toluene, photoexcitation at 530 nm preferentially excites PDI, and the dyad undergoes charge separation in τ = 1.7 ps and recombination in τ = 1.6 ns. In MCH and in thin solid films, 530 nm excitation of the PDI-Car aggregate also results in charge transfer that competes with energy transfer from ¹*PDI to Car and with an additional process, rapid Car triplet formation in <50 ps. Car triplet formation is only observed in the aggregated PDI-Car dyad and is attributed to singlet exciton fission (SF) within the aggregated PDI, followed by rapid triplet energy transfer from ³*PDI to the carotenoid. SF from β-apocarotene aggregation is ruled out by direct excitation of Car films at 414 nm, where no triplet formation is observed. Time-resolved electron paramagnetic resonance measurements on aggregated PDI-Car show the formation of ³*Car with a spin-polarization pattern that rules out radical-pair intersystem crossing as the mechanism of triplet formation as well

Synthesis, Modular Composition, and Electrochemical Properties of Lamellar Iron SulfidesSynthesis, Modular Composition, and Electrochemical Properties of Lamellar Iron Sulfides

Transition metal chalcogenides with layered structures have emerged as promising materials for energy storage, catalysis, and electronics, among other areas. We have identified a new layered phase of iron sulfide containing interlayer solvated cations. We present an optimized synthesis for the Li+-containing material from an Fe(III) xanthate complex. Structure and composition data indicate the material consists of poorly-ordered iron sulfide layers separated by solvated cations. The lamellar spacing in these materials can be tuned by changing the identity of the cation. Furthermore, the lamellar spacing can also be reversibly tuned by the degree of solvation of the material. The material is electrically conductive and can serve as a pseudocapacitor with comparable performance to commercial materials such as MnO2. Furthermore, these materials also show promise as lithium or sodium ion battery cathodes with good capacity and reversibility

Steric and Electronic Effects of Ligand Substitution on Redox-Active Fe4S4-Based Coordination Polymers

One of the notable advantages of molecular materials is the ability to precisely tune structure, properties, and function via molecular substitutions. While many studies have demonstrated this principle with classic carboxylate‐based coordination polymers, there are comparatively fewer examples where systematic changes to sulfur‐based coordination polymers have been investigated. Here we present such a study on 1D coordination chains of redox‐activeiron-sulfur clusters linked by methylated 1,4‐benzene‐dithiolates. A series of new iron-sulfur based coordination polymers were synthesized with either 2,5‐dimethyl‐1,4‐benzenedithiol (DMBDT) or 2,3,5,6‐tetramethyl‐1,4‐benzenedithiol. The structures of these compounds have been characterized based on synchrotron Xraypowder diffraction while their chemical and physical properties have been characterized by techniques including X‐ray photoelectron spectroscopy, cyclic voltammetry and UV–visible spectroscopy. Methylation results in the general trend of increasing electron‐richness in the series, but the tetramethyl version exhibits unexpected properties arising from steric constraints. All these results highlight how substitutions on organic linkers can modulate electronic factors to fine‐tune the electronic structures of metal‐organic materials.</div

Picosecond Control of Photogenerated Radical Pair Lifetimes Using a Stable Third Radical

Photoinduced electron transfer reactions in organic donor–acceptor systems leading to long-lived radical ion pairs (RPs) have attracted broad interest for their potential applications in fields as diverse as solar energy conversion and spintronics. We present the photophysics and spin dynamics of an electron donor − electron acceptor − stable radical system consisting of a <i>meta</i>-phenylenediamine (mPD) donor covalently linked to a 4-aminonaphthalene-1,8-dicarboximide (ANI) electron-accepting chromophore as well as an α,γ-bisdiphenylene-β-phenylallyl (BDPA) stable radical. Selective photoexcitation of ANI produces the BDPA–mPD^+•–ANI^–• triradical in which the mPD^+•–ANI^–• RP spins are strongly exchange coupled. The presence of BDPA is found to greatly increase the RP intersystem crossing rate from the initially photogenerated BDPA–¹(mPD^+•–ANI^–•) to BDPA–³(mPD^+•–ANI^–•), resulting in accelerated RP recombination via the triplet channel to produce BDPA–mPD–^3*ANI as compared to a reference molecule lacking the BDPA radical. The RP recombination rates observed are much faster than those previously reported for weakly coupled triradical systems. Time-resolved EPR spectroscopy shows that this process is also associated with strong spin polarization of the stable radical. Overall, these results show that RP intersystem crossing rates can be strongly influenced by stable radicals nearby strongly coupled RP systems, making it possible to use a third spin to control RP lifetimes down to a picosecond time scale

Photogenerated Quartet State Formation in a Compact Ring-Fused Perylene-Nitroxide

We report on a novel small organic molecule comprising a perylene chromophore fused to a six-membered ring containing a persistent nitroxide radical to give a perylene-nitroxide, or <b>PerNO</b>^•. This molecule is a robust, compact molecule in which the radical is closely bound to the chromophore but separated by saturated carbon atoms, thus limiting the electronic coupling between the chromophore and radical. We present both ultrafast transient absorption experiments and time-resolved EPR (TREPR) studies to probe the spin dynamics of photoexcited <b>PerNO</b>^<b>•</b> and utilize X-ray crystallography to probe the molecular structure and stacking motifs of <b>PerNO</b>^<b>•</b> in the solid state. The ability to control both the structure and electronic properties of molecules having multiple spins as well as the possibility of assembling ordered solid state materials from them is important for implementing effective molecule-based spintronics

Electron Hopping and Charge Separation within a Naphthalene-1,4:5,8-bis(dicarboximide) Chiral Covalent Organic Cage

We present the stereoselective synthesis of a chiral covalent organic cage consisting of three redox-active naphthalene-1,4:5,8-bis­(dicarboximide) (NDI) units by dynamic imine chemistry. Single crystal X-ray diffraction analysis shows that host–guest interactions and racemic cocrystallization allow for controlling the solid state structure. Electronic interactions between the NDI units probed by absorption and circular dichroism spectroscopies, electrochemistry and theoretical calculations are shown to be weak. Photoexcitation of NDI leads to intracage charge separation with a longer lifetime than observed in the corresponding monomeric NDI and dimeric NDI cyclophane imines. The EPR spectrum of the singly reduced cage shows that the electron is localized on a single NDI unit at ambient temperatures and transitions to rapid hopping among all three NDI units upon heating to 350 K. Dynamic covalent chemistry thus promises rapid access to covalent organic cages with well-defined architectures to study charge accumulation and electron transport phenomena

Spin-Selective Photoreduction of a Stable Radical within a Covalent Donor–Acceptor–Radical Triad

Controlling spin–spin interactions in multispin molecular assemblies is important for developing new approaches to quantum information processing. In this work, a covalent electron donor–acceptor–radical triad is used to probe spin-selective reduction of the stable radical to its diamagnetic anion. The molecule consists of a perylene electron donor chromophore (D) bound to a pyromellitimide acceptor (A), which is, in turn, linked to a stable α,γ-bisdiphenylene-β-phenylallyl radical (R^•) to produce D-A-R^•. Selective photoexcitation of D within D-A-R^• results in ultrafast electron transfer to form the D^+•-A^–•-R^• triradical, where D^+•-A^–• is a singlet spin-correlated radical pair (SCRP), in which both SCRP spins are uncorrelated relative to the R^• spin. Subsequent ultrafast electron transfer within the triradical forms D^+•-A-R^–, but its yield is controlled by spin statistics of the uncorrelated A^–•-R^• radical pair, where the initial charge separation yields a 3:1 statistical mixture of D^+•-³(A^–•-R^•) and D^+•-¹(A^–•-R^•), and subsequent reduction of R^• only occurs in D^+•-¹(A^–•-R^•). These findings inform the design of multispin systems to transfer spin coherence between molecules targeting quantum information processing using the agency of SCRPs