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Many transition metal coordination complexes are known to undergo a structural change in response to a stimulus, like light, which can have a debilitating impact on properties of interest (e.g., quantum yield, stability, reactivity, etc.). This is particularly true for Cu(I) coordination complexes that suffer from short, excited-state lifetimes due to D2d to D2 distortion and solvent coordination. Here, we investigate the impact of strategic surface binding and the role of the surface binding motif on the excited state lifetime of Cu(I) complexes with carboxylate-functionalized N-phenylpyridin-2-ylmethanimine ligands. Relative to the solution, the excited state lifetime for the ZrO2-bound complexes increases 7-fold when either one ligand is bound or both ligands are bound through a flexible linker but 17-fold when both ligands are rigidly bound to the surface. With support from theoretical calculations, we attribute the dramatic increase in lifetime for the latter to the rigid binding strategy inhibiting the planarizing distortion and possible quenching via solvent coordination. These results lend further support to the idea that molecular immobilization via strategic surface binding is an effective strategy for inhibiting undesired molecular distortion. 

This paper presents a subregular analysis of syntactic agreement patterns modeled using command strings over Minimalist Grammar (MG) dependency trees (Graf and Shafiei 2019), incorporating a novel MG treatment of agreement. Phenomena of interest include relativized minimality and its exceptions, direction of feature transmission, and configurations involving chains of agreeing elements. Such patterns are shown to fall within the class of tier-based strictly 2-local (TSL-2) languages, which has previously been argued to subsume the majority of long-distance syntactic phenomena, as well as those in phonology and morphology (Graf 2022a). This characterization places a tight upper bound on the range of configurations that are predicted to occur while providing parameters for variation which closely match the observed typology. 

Building on recent work in subregular syntax, we argue that syntactic constraints are best understood as operating not over trees, but rather strings that track structural relations such as dominance and c-command. Even constraints that seem intrinsically tied to trees (e.g. constraints on tree tiers) can be reduced to such strings. We define serial constraints as an abstraction that decomposes string constraints into a context function (which associates nodes with strings) and a requirement function (which enforces constraints on these strings). We provide a general procedure for implementing serial constraints as deterministic tree automata. The construction reveals that the many types of constraints found in subregular syntax are variants of the same computational template. Our findings open up a string-based perspective on syntactic constraints and provide a new, very general approach to the automata-theoretic study of subregular complexity. 

We use the MG treebank of Torr (2017) to investigate the conjecture in Graf (2020) that category systems are ISL-2 inferrable. A category system is ISL-2 inferrable iff the category feature of every lexical item can be jointly inferred from phonological exponents of both the item itself and either its selecting head or the arguments it selects. If correct, this conjecture would greatly limit the overgeneration problem posed by subcategorization mechanisms. Our corpus study finds that the conjecture is largely borne out, with only a few exceptions attested in the corpus. However, we also observe that it holds even for features that aren't expected to be inferrable in this manner, and we demonstrate that inferrability can arise merely from language datasets displaying Zipfian distributions. We conclude that category systems in natural languages may well be ISL-2 inferrable, but that this could be due to extragrammatical factors. 

Molecules undergo a structural change to minimize the energy of excited states generated via external stimuli such as light. This is particularly problematic for Cu(I) coordination complexes which are an intriguing alternative to the rare and expensive transition metal containing complexes (e.g., Pt, Ir, Ru, etc.) but suffer from short excited state lifetimes due to D2d to D2 distortion and solvent coordination. Here we investigate strategic surface binding as an approach to hinder this distortion and increase the excited state lifetime of Cu(I) polypyridyl complexes. Using transient absorption spectroscopy, we observe a more than 20-fold increase in excited state lifetime, relative to solution, for a Cu(I) complex that can coordinate to the ZrO2 via both carboxylated ligands. In contrast, the Cu(I) complex that coordinates via only one ligand has a less pronounced enhancement upon surface binding and exhibits greater sensitivity to coordinating solvents. A combination of ATR-IR and polarized visible ATR measurements as well as theoretical calculations suggest that the increased lifetime is due to surface binding which decreases the degrees of freedom for molecular distortion (e.g., D2d to D2), with the doubly bound complex exhibiting the most pronounced enhancement. 

Generative artificial intelligence (AI) technology is expected to have a profound impact on chemical education. While there are certainly positive uses, some of which are being actively implemented even now, there is a reasonable concern about its use in cheating. Efforts are underway to detect generative AI usage on open-ended questions, lab reports, and essays, but its detection on multiple choice exams is largely unexplored. Here we propose the use of Rasch analysis to identify the unique behavioral pattern of ChatGPT on General Chemistry II, multiple choice exams. While raw statistics (e.g., average, ability, outfit) were insufficient to readily identify ChatGPT instances, a strategy of fixing the ability scale on high success questions and then refitting the outcomes dramatically enhanced its outlier behavior in terms of Z-standardized out-fit statistic and ability displacement. Setting the detection threshold to a true positive rate (TPR) of 1.0, a false positive rate (FPR) of <0.1 was obtained across a majority of the 20 exams investigated here. Furthermore, the receiver operating characteristic curve (i.e., FPR vs TPR) exhibited outstanding areas under the curve of >0.9 for nearly all exams. While limitations of this method are described and the analysis is by no means exhaustive, these outcomes suggest that the unique behavior patterns of generative AI chat bots can be identified using Rasch modeling and fit statistics. 

We present a six-step cascade that converts 1,3-distyrylbenzenes (bis-stilbenes) into nonsymmetric pyrenes in 40–60% yields. This sequence merges photochemical steps, E,Z-alkene isomerization, a 6π photochemical electrocyclization (Mallory photocyclization); the new bay region cyclization, with two radical iodine-mediated aromatization steps; and an optional aryl migration. This work illustrates how the inherent challenges of engineering excited state reactivity can be addressed by logical design. An unusual aspect of this cascade is that the same photochemical process (the Mallory reaction) is first promoted and then blocked in different stages within a photochemical cascade. The use of blocking groups is the key feature that makes simple bis-stilbenes suitable substrates for directed double cyclization. While the first stilbene subunit undergoes a classic Mallory photocyclization to form a phenanthrene intermediate, the next ring-forming step is diverted from the conventional Mallory path into a photocyclization of the remaining alkene at the phenanthrene’s bay region. Although earlier literature suggested that this reaction is unfavorable, we achieved this diversion via incorporation of blocking groups to prevent the Mallory photocyclization. The two photocyclizations are assisted by the relief of the excited state antiaromaticity. Reaction selectivity is controlled by substituent effects and the interplay between photochemical and radical reactivity. Furthermore, the introduction of donor substituents at the pendant styrene group can further extend this photochemical cascade through a radical 1,2-aryl migration. Rich photophysical and supramolecular properties of the newly substituted pyrenes illustrate the role of systematic variations in the structure of this classic chromophore for excited state engineering.