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Carbon nanomaterials composed of curved aromatics, such as carbon nanotubes, are difficult to selectively synthesize and modify precisely. Smaller molecular fragments of curved nanomaterials, such as cycloparaphenylenes, benefit from the precision of bottom-up synthesis, however, efforts to expand the curved molecular framework into even larger structures often rely on restrictive early stage synthetic strategies or difficult to control polymerizations. In this work we report a high yielding, strain-promoted, late-stage modification of a series of [ n + 1]CPPs. We show that the conversion of these [ n + 1]CPPs into soluble, pinwheel-like multipore carbon nanostructures is achievable via a straightforward and efficient metal-mediated alkyne cyclotrimerization reaction. We provide insight into suitable metals for this transformation, the photophysics of these trimeric molecules, as well as their strain profiles and crystal packing. We also demonstrate the strain-enhanced nature of the reaction under the optimized conditions, showing that strained internal-alkyne [ n + 1]CPPs efficiently undergo complete conversion whereas unstrained diphenylacetylene remains completely unreacted. We anticipate that this work will have broader impacts on the study of reactivity in strained-alkyne-containing hydrocarbons, and that access to this new molecular architecture will inspire new research and applications in materials science and related fields.

Chalaniline A, an aminofulveno[1,2- b ]chromone derivative previously isolated from a vorinostat-treated ascomycete Chalara sp., was prepared in nine steps from orcinol (3,5-dihydroxytoluene). In a key transformation, the tricyclic ring system of the target was generated by a pyrrolidine-catalyzed double annulation between α-(methylsulfinyl)-2,6-dihydroxy-4-methylacetophenone and the ketaldoester, methyl 2,5-dioxopentanoate. The resulting tertiary alcohol (coniochaetone H) was further converted to chalaniline A by operations including dehydration (to yield a hydroxyfulvene), Vilsmeier reaction, and enamine exchange.

To further the ability to manipulate the properties of open-shell molecules, logical and incremental modifications to molecular structure are key steps that provide fine-tuning of established diradicaloid scaffolds. We report the synthesis of an electronically "pure" diradicaloid based on a 2,6-anthroquinoidal core where the once necessary ethynyl "wings" are removed. Through the simplification of the overall electronic structure, the singlet-triplet energy gap increases by 0.3-0.4 kcal mol -1 in the reported diradicaloids while avoiding significant disruption to their optoelectronic properties.

Thiol-disulfide interchange has been a large field of study for both biochemists and physical organic chemists alike due to its prevalence within biological systems and fundamentally interesting dynamic nature. More recently, efforts have been made to harness the power of this reversible reaction to make self-assembling systems of macrocyclic molecules. However, less effort has focused on the fundamental work of isolating these assemblies and studying the factors that control the assembly and sorting of these emerging cyclic systems. A more complete fundamental understanding of factors controlling such self-assembly could also improve understanding of the complex systems biology of thiol exchange while also aiding in the design of dynamic thiol assembly to enable applications ranging from drug delivery and biosensing to new materials synthesis. We have shown previously that pnictogen-assisted self-assembly enables formation of discrete disulfide macrocycles and cages without competition from polymer formation for a wide variety of alkyl thiols. In this study, we report the expansion of pnictogen-assisted self-assembly methods to form disulfide bearing macrocycles from aryl thiol containing ligands, allowing access to previously unreported molecules. These studies complement classical physical organic and chemical biology studies on the rates and products of aryl thiol oxidation to disulfides, and we show that this self-assembly method revises some prevailing wisdom from these key classical studies by providing new product distributions and new isolable products in cyclic disulfide formation., (© 2024 Wiley-VCH GmbH.)

Persulfides (RSS - ) are ubiquitous source of sulfides (S 2- ) in biology, and interactions between RSS - and bioinorganic metal centers play critical roles in biological hydrogen sulfide (H 2 S) biogenesis, signaling, and catabolism. Here, we report the use of contact-ion stabilized [Na(15-crown-5)][ t BuSS] ( 1 ) as a simple synthon to access rare metal alkyl persulfide complexes and to investigate the reactivity of RSS - with transition metal centers to provide insights into metal thiolate persulfidation, including the fundamental difference between alkyl persulfides and alkyl thiolates. Reaction of 1 with [Co II (TPA)(OTf)] + afforded the η 1 -alkyl persulfide complex [Co II (TPA)(SS t Bu)] + ( 2 ), which was characterized by X-ray crystallography, UV-vis spectroscopy, and Raman spectroscopy. RSS - coordination to the Lewis acidic Co 2+ center provided additional stability to the S-S bond, as evidenced by a significant increase in the Raman stretching frequency for 2 ( v S-S = 522 cm -1 , Δ v S-S = 66 cm -1 ). The effect of persulfidation on metal center redox potentials was further elucidated using cyclic voltammetry, in which the Co 2+ → Co 3+ oxidation potential of 2 ( E p,a = +89 mV vs SCE) is lowered by nearly 700 mV when compared to the corresponding thiolate complex [Co II (TPA)(S t Bu)] + ( 3 ) ( E p,a = +818 mV vs SCE), despite persulfidation being generally seen as an oxidative post-translational modification. The reactivity of 2 toward reducing agents including PPh 3 , BH 4 - , and biologically relevant thiol reductant DTT led to different S 2- output pathways, including formation of a dinuclear 2Co-2SH complex [Co II 2 (TPA) 2 (μ 2 -SH) 2 ] 2+ ( 4 ).

Herein, we report the synthesis of a modular family of novel bimetallic tetraamidodiamine (tada) ligands, Li 4 -R-tada (R = Me 3 Si, t BuMe 2 Si, and i Pr 3 Si). These silylamido ligands display two distinct binding pockets whose steric profiles can be easily tuned by choice of the substituents on silicon. We also show that salt metathesis is a convenient route to install these new ligands on the early transition metals titanium(IV) and vanadium(III).

High oxidation state metal cations in the form of oxides, oxoanions, or oxoperoxoanions have diverse roles in carbon dioxide removal (direct air capture and point source). Features include providing basic oxygens for chemisorption reactions, direct binding of carbonate, and catalyzing low-temperature CO 2 release to regenerate capture media. Moreover, metal oxides and aqueous metal-oxo species are stable in harsh, point-source conditions. Here, we demonstrate aqueous niobium polyoxometalate (POM) carbon capture ability, specifically [Nb 6 O 19 ] 8- , Nb 6 . Upon exposure of aqueous Nb 6 to CO 2 , Nb 6 fragments and binds chemisorbed carbonate, evidenced by crystallization of Nb-carbonate POMs including [Nb 22 O 53 (CO 3 ) 16 ] 28 - and [Nb 10 O 25 (CO 3 ) 6 ] 12- . While Rb/Cs + counter cations yield crystal structures to understand the chemisorption processes, K + counter cations enable higher capture efficiency (based on CO 3 /Nb ratio), determined by CHN analysis and thermogravimetry-mass spectrometry of the isolated solids. Sum frequency generation spectroscopy also showed higher carbon capture efficiency of the K-Nb 6 solutions at the air-water interface, while small-angle X-ray scattering (SAXS) provided insights into the role of the alkalis in influencing these processes. Tetramethylammonium counter cations, like K + , demonstrate high efficiency of carbonate chemisorption at the interface, but SAXS and Raman of the bulk showed a predominance of a Nb 24 -POM (H x Nb 24 O 72 , x ∼ 9) that does not bind carbonate. Control experiments show that carbonate detected at the interface is Nb-bound, and the Nb-carbonate species are stabilized by alkalis, demonstrating their supporting role in aqueous Nb-POM CO 2 chemisorption. Of fundamental importance, this study presents rare examples of directing POM speciation with a gas, instead of liquid phase acid or base.

ELQ-300 is a potent antimalarial drug with activity against blood, liver, and vector stages of the disease. A prodrug, ELQ-331 , exhibits reduced crystallinity and improved in vivo efficacy in preclinical testing, and currently, it is in the developmental pipeline for once-a-week dosing for oral prophylaxis against malaria. Because of the high cost of developing a new drug for human use and the high risk of drug failure, it is prudent to have a back-up plan in place. Here we describe ELQ-596 , a member of a new subseries of 3-biaryl-ELQs, with enhanced potency in vitro against multidrug-resistant Plasmodium falciparum parasites. ELQ-598 , a prodrug of ELQ-596 with diminished crystallinity, is more effective vs murine malaria than its progenitor ELQ-331 by 4- to 10-fold, suggesting that correspondingly lower doses could be used to protect and cure humans of malaria. With a longer bloodstream half-life in mice compared to its progenitor, ELQ-596 highlights a novel series of next-generation ELQs with the potential for once-monthly dosing for protection against malaria infection. Advances in the preparation of 3-biaryl-ELQs are presented along with preliminary results from experiments to explore key structure-activity relationships for drug potency, selectivity, pharmacokinetics, and safety.

Mechanically interlocked molecules (MIMs) represent an exciting yet underexplored area of research in the context of carbon nanoscience. Recently, work from our group and others has shown that small carbon nanotube fragments-[n]cycloparaphenylenes ([n]CPPs) and related nanohoop macrocycles-may be integrated into mechanically interlocked architectures by leveraging supramolecular interactions, covalent tethers, or metal-ion templates. Still, available synthetic methods are typically difficult and low yielding, and general methods that allow for the creation of a wide variety of these structures are limited. Here we report an efficient route to interlocked nanohoop structures via the active template Cu-catalyzed azide-alkyne cycloaddition (AT-CuAAC) reaction. With the appropriate choice of substituents, a macrocyclic precursor to 2,2'-bipyridyl embedded [9]CPP (bipy[9]CPP) participates in the AT-CuAAC reaction to provide [2]rotaxanes in near-quantitative yield, which can then be converted into the fully π-conjugated catenane structures. Through this approach, two nanohoop[2]catenanes are synthesized which consist of a bipy[9]CPP catenated with either Tz[10]CPP or Tz[12]CPP (where Tz denotes a 1,2,3-triazole moiety replacing one phenylene ring in the [n]CPP backbone)., (© 2024 Wiley-VCH GmbH.)

H 2 S is a physiologically important signaling molecule with complex roles in biology and exists primarily as HS - at physiological pH. Despite this anionic character, few investigations have focused on the molecular recognition and reversible binding of this important biological anion. Using a series of imidazole and imidazolium host molecules, we investigate the role of preorganization and charge on HS - binding. Using a macrocyclic bis -imidazolium receptor, we demonstrate the unexpected 2:1 host-guest binding of HS - , which was characterized both in solution and by X-ray crystallography. To the best of our knowledge, this is the first example of this binding stoichiometry for HS - binding. Moreover, the short C-H···S distances of 2.53, 2.54, 2.76, and 2.79 Å are well within the sum of the van der Waals radii of the interacting atoms, which is consistent with strong C-H···S interactions.

Cycloparaphenylenes (CPPs) are the smallest possible armchair carbon nanotubes, the properties of which strongly depend on their ring size. They can be further tuned by either peripheral functionalization or by replacing phenylene rings for other aromatic units. Here we show how four novel donor-acceptor chromophores were obtained by incorporating fluorenone or 2-(9H-fluoren-9-ylidene)malononitrile into the loops of two differently sized CPPs. Synthetically, we managed to perform late-stage functionalization of the fluorenone-based rings by high-yielding Knoevenagel condensations. The structures were confirmed by X-ray crystallographic analyses, which revealed that replacing a phenylene for a fused-ring-system acceptor introduces additional strain. The donor-acceptor characters of the CPPs were supported by absorption and fluorescence spectroscopic studies, electrochemical studies (displaying the CPPs as multi-redox systems undergoing reversible or quasi-reversible redox events), as well as by computations. The oligophenylene parts were found to comprise the electron donor units of the macrocycles and the fluorenone parts the acceptor units., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Several phosphaquinolinone derivatives have been synthesized and characterized to explore their usefulness in the realm of cell imaging. Solution-state photophysical properties in both aqueous and organic solutions were collected for these derivatives. Additionally, CCK-8 cell viability assays and fluorescent imaging in HeLa cells incubated with the new heterocyclic derivatives show evidence of favorable cell permeability, cell viability, and moderate intracellular localization when appended with the well-known morpholine targeting motif.

Hydrosulfide (HS - ) is the conjugate base of gasotransmitter hydrogen sulfide (H 2 S) and is a physiologically-relevant small molecule of great interest in the anion sensing community. However, selective sensing and molecular recognition of HS - in water remains difficult because, in addition to the diffuse charge and high solvation energy of anions, HS - is highly nucleophilic and readily oxidizes into other reactive sulfur species. Moreover, the direct placement of HS - in the Hofmeister series remains unclear. Supramolecular host-guest interactions provide a promising platform on which to recognize and bind hydrosulfide, and characterizing the placement of HS - in the Hofmeister series would facilitate the future design of selective receptors for this challenging anion. Few examples of supramolecular HS - binding have been reported, but the Sindelar group reported HS - binding in water using bambus[6]uril macrocycles in 2018. We used this HS - binding platform as a starting point to develop a chemically-sensitive field effect transistor (ChemFET) to facilitate assigning HS - to a specific place in the Hofmeister series. Specifically, we prepared dodeca- n -butyl bambus[6]uril and incorporated it into a ChemFET as the HS - receptor motif. The resultant device provided an amperometric response to HS - , and we used this device to measure the response of other anions, including SO 4 2- , F - , Cl - , Br - , NO 3 - , ClO 4 - , and I - . Using this response data, we were able to experimentally determine that HS - lies between Cl - and Br - in the Hofmeister series, which matches recent theoretical computational work that predicted a similar placement. Taken together, these results highlight the potential of using molecular recognition coupled with ChemFET architectures to develop new approaches for direct and reversible HS - detection and measurement in water and further advance our understanding of different recognition approaches for this challenging anion., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Fusion of aromatic subunits to stabilize an antiaromatic core allows the isolation and study of otherwise unstable paratropic systems. A complete study of a series of six naphthothiophene-fused s-indacene isomers is herein described. Additionally, the structural modifications resulted in increased π-π overlap in the solid state, which was further explored through changing the sterically blocking mesityl group to (triisopropylsilyl)ethynyl in three derivatives. The computed antiaromaticity of the six isomers is compared to the observed physical properties, such as NMR chemical shift, UV-vis, and CV data. We find that the calculations predict the most antiaromatic isomer and give a general estimation of the relative degree of paratropicity for the remaining isomers, when compared to the experimental results., (© 2023 Wiley-VCH GmbH.)

Reactive sulfur species (RSS) and reactive selenium species (RSeS) play integral roles in hydrogen sulfide (H 2 S) and hydrogen selenide (H 2 Se) biological signaling pathways, and dichalcogenide anions are proposed transient intermediates that facilitate a variety of biochemical transformations. Herein we report the selective synthesis, isolation, spectroscopic and structural characterization, and fundamental reactivity of persulfide (RSS - ), perselenide (RSeSe - ), thioselenide (RSSe - ), and selenosulfide (RSeS - ) anions. The isolated chalcogenides do not rely on steric protection for stability and have steric profiles analogous to cysteine (Cys). Simple reduction of S 8 or Se by potassium benzyl thiolate (KSBn) or selenolate (KSeBn) in the presence of 18-crown-6 afforded [K(18-crown-6)][BnSS] ( 1 ), [K(18-crown-6)][BnSeSe] ( 2 ), [K(18-crown-6][BnSSe] ( 3 ), and [K(18-crown-6][BnSeS] ( 4 ). The chemical structure of each dichalcogenide was confirmed by X-ray crystallography and solution-state 1 H, 13 C, and 77 Se NMR spectroscopy. To advance our understanding of the reactivity of these species, we demonstrated that reduction of 1 - 4 by PPh 3 readily generates E═PPh 3 (E: S, Se), and reduction of 1 , 3 , and 4 by DTT readily produces HE - /H 2 E. Furthermore, 1 - 4 react with CN - to produce ECN - , which is consistent with the detoxifying effects of dichalcogenide intermediates in the Rhodanese enzyme. Taken together, this work provides new insights into the inherent structural and reactivity characteristics of dichalcogenides relevant to biology and advances our understanding of the fundamental properties of these reactive anions.

Deriving diverse compound libraries from a single substrate in high yields remains to be a challenge in cycloparaphenylene chemistry. In here, a strategy for the late-stage functionalization of shape-persistent alkyne-containing cycloparaphenylene has been explored using readily available azides. The copper-free [3+2]azide-alkyne cycloaddition provided high yields (>90 %) in a single reaction step. Systematic variation of the azides from electron-rich to -deficient shines light on how peripheral substitution influences the characteristics of the resulting adducts. We find that among the most affected properties are the molecular shape, the oxidation potential, excited state features, and affinities towards different fullerenes. Joint experimental and theoretical results are presented including calculations with the state-of-the-art, artificial intelligence-enhanced quantum mechanical method 1 (AIQM1)., (© 2023 Wiley-VCH GmbH.)

The phosphaquinolinone scaffold has been previously studied as a modular core for a variety of fluorescent species where use of substituent effects has focused on increasing or decreasing electron density in the core rings. We now report the synthesis and analysis of several pyridine-containing phosphaquinolinone species exhibiting notable linear conjugation from the aryl-substituent to electron-withdrawing pyridyl nitrogen. Varying the nature of the aryl substituent from electron-withdrawing to electron-donating leads to the generation of an internal charge-transfer (ICT) band in the absorbance spectrum, which becomes the dominant absorbance in terms of intensity in the most electron-rich -NMe 2 example. This heterocycle exhibits improved photophysical properties compared to others in the set including high quantum yield and considerably red-shifted emission. The enhanced ICT can be observed in the X-ray data where a rare example of molecule co-planarity is observed. Computational data show increased localization of negative charge on the pyridyl nitrogen as the electron-donating character of the aryl-substituent increases., (© 2023 Wiley-VCH GmbH.)

Mechanically interlocked carbon nanostructures represent a relatively unexplored frontier in carbon nanoscience due to the difficulty in preparing these unusual topological materials. Here we illustrate an active-template method in which a [n]cycloparaphenylene precursor macrocycle is decorated with two convergent pyridine donors that coordinate to a metal ion. The metal ion catalyses alkyne-alkyne cross-coupling reactions within the central cavity of the macrocycle, and the resultant interlocked products can be converted into fully π-conjugated structures in subsequent synthetic steps. Specifically, we report the synthesis of a family of catenanes that comprise two or three mutually interpenetrating [n]cycloparaphenylene-derived macrocycles of various sizes. Additionally, a fully π-conjugated [3]rotaxane was synthesized by the same method. The development of synthetic methods to access mechanically interlocked carbon nanostructures of varying topology can help elucidate the implications of mechanical bonding for this emerging class of nanomaterials and allow structure-property relationships to be established., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

The [ Ph B( t BuIm) 3 ] 1- ligand has gained increased attention since it was first reported in 2006 due to its ability to stabilize highly reactive first row transition metal complexes. In this work, we investigate the coordination chemistry of this ligand with redox-inert zinc to understand how a zinc metal center behaves in such a strong coordinating environment. The Ph B( t BuIm) 3 ZnCl (1) complex can be formed via deprotonation of [ Ph B( t BuIm) 3 ][OTf] 2 followed by the addition of ZnCl 2 . Salt metathesis reaction with nucleophilic n -BuLi yields the highly carbon-rich zinc coordination complex Ph B( t BuIm) 3 ZnBu (2) with three carbene atom donors and one carbanion donor. In contrast, reaction of complex 1 with a less nucleophilic polysulfide reagent, [K.18-C-6] 2 [S 4 ], leads to the formation of a tetrahedral zinc tetrasulfido complex via protonation of one carbene donor to form Ph B( t BuIm) 2 ( t BuImH)Zn(κ 2 -S 4 ) (3).

Reactive sulfur species (RSS) play critical roles in diverse chemical environments. Molecules containing sulfane sulfur (S 0 ) have emerged as key species involved in cellular redox buffering as well as RSS generation, translocation, and action. Using cucurbit[7]uril (CB[7]) as a model hydrophobic host, we demonstrate here that S 8 can be encapsulated to form a 1:1 host guest complex, which was confirmed by solution state experiments, mass spectrometry, and X-ray crystallography. The solid state structure of CB[7]/S 8 shows that the encapsulated S 8 is available to nucleophiles through the carbonyl portals of the host. Treatment of CB[7]/S 8 with thiols results in efficient reduction of S 8 to H 2 S in water at physiological pH. We establish that encapsulated S 8 is attacked by a thiol within the CB[7] host and that the resultant soluble hydropolysulfide is ejected into solution, where it reacts further with thiols to generate soluble sulfane sulfur carriers and ultimately H 2 S. The formation of these intermediate is supported by observed kinetic saturation behavior, competitive inhibition experiments, and alkylative trapping experiments. We also demonstrate that CB[7]/S 8 can be used to increase sulfane sulfur levels in live cells using fluorescence microscopy. More broadly, this work suggests a general activation mechanism of S 8 by hydrophobic motifs, which may be applicable to proteins, membranes, or other bimolecular compartments that could transiently bind and solubilize S 8 to promote reaction with thiols to solubilize and shuttle S 8 back into the redox labile sulfane sulfur pool. Such a mechanism would provide an attractive manifold in which to understand the RSS translocation and trafficking.

S/N crosstalk species derived from the interconnected reactivity of H 2 S and NO facilitate the transport of reactive sulfur and nitrogen species in signaling, transport, and regulatory processes. We report here that simple Fe 2+ ions, such as those that are bioavailable in the labile iron pool (LIP), react with thionitrite (SNO - ) and perthionitrite (SSNO - ) to yield the dinitrosyl iron complex [Fe(NO) 2 (S 5 )] - . In the reaction of FeCl 2 with SNO - we were able to isolate the unstable intermediate hydrosulfido mononitrosyl iron complex [FeCl 2 (NO)(SH)] - , which was characterized by X-ray crystallography. We also show that [Fe(NO) 2 (S 5 )] - is a simple synthon for nitrosylated Fe-S clusters via its reduction with PPh 3 to yield Roussin's Red Salt ([Fe 2 S 2 (NO) 4 ] 2- ), which highlights the role of S/N crosstalk species in the assembly of fundamental Fe-S motifs., (© 2022 Wiley-VCH GmbH.)

Inclusion of a second nitrogen atom in the aromatic core of phosphorus-nitrogen (PN) heterocycles results in unexpected tautomerization to a nonaromatic form. This tautomerization, initially observed in the solid state through X-ray crystallography, is also explained by computational analysis. We prepared an electron deficient analogue (2 e) with a fluorine on the pyridine ring and showed that the weakly basic pyridine resisted tautomerization, providing key insights to why the transformation occurs. To study the difference in solution vs. solid-state heterocycles, alkylated analogues that lock in the quinoidal tautomer were synthesized and their different 1 H NMR and UV/Vis spectra studied. Ultimately, we determined that all heterocycles are the aromatic tautomer in solution and all but 2 e switch to the quinoidal tautomer in the solid state. Better understanding of this transformation and under what circumstances it occurs suggest future use in a switchable on/off hydrogen-bond-directed receptor that can be tuned for complementary hydrogen bonding., (© 2022 Wiley-VCH GmbH.)

Hydrogen selenide (H 2 Se) is a central metabolite in the biological processing of selenium for incorporation into selenoproteins, which play crucial antioxidant roles in biological systems. Despite being integral to proper physiological function, this reactive selenium species (RSeS) has received limited attention. We recently reported an early example of a H 2 Se donor (TDN1042) that exhibited slow, sustained release through hydrolysis. Here we expand that technology based on the P═Se motif to develop cyclic-PSe compounds with increased rates of hydrolysis and function through well-defined mechanisms as monitored by 31 P and 77 Se NMR spectroscopy. In addition, we report a colorimetric method based on the reaction of H 2 Se with NBD-Cl to generate NBD-SeH (λ max = 551 nm), which can be used to detect free H 2 Se. Furthermore, we use TOF-SIMS (time of flight secondary ion mass spectroscopy) to demonstrate that these H 2 Se donors are cell permeable and use this technique for spatial mapping of the intracellular Se content after H 2 Se delivery. Moreover, these H 2 Se donors reduce endogenous intracellular reactive oxygen species (ROS) levels. Taken together, this work expands the toolbox of H 2 Se donor technology and sets the stage for future work focused on the biological activity and beneficial applications of H 2 Se and related bioinorganic RSeS.

Selective coupling of NO by a nonclassical dinuclear dinitrosyliron complex (D-DNIC) to form N 2 O is reported. The coupling is facilitated by the pyridinediimine (PDI) ligand scaffold, which enables the necessary denticity changes to produce mixed-valent, electron-deficient tethered DNICs. One-electron oxidation of the [{Fe(NO) 2 }] 2 10/10 complex Fe 2 ( Pyrr PDI)(NO) 4 ) results in NO coupling to form N 4 ) results in NO coupling to form N 2 O via the mixed-valent {[Fe(NO) 2 ] 2 } 9/10 species, which possesses an electron-deficient four-coordinate {Fe(NO) 2 site, crucial in N-N bond formation. The hemilability of the PDI scaffold dictates the selectivity in N-N bond formation because stabilization of the five-coordinate {Fe(NO) 10 site, crucial in N-N bond formation. The hemilability of the PDI scaffold dictates the selectivity in N-N bond formation because stabilization of the five-coordinate {Fe(NO) 2 } 9 site in the mixed-valent [{Fe(NO) 2 }] 2 9/10 species, [Fe 2 ( Pyr2 PDI)(NO) 4 ][PF 6 ] ( 6 site, and hence no N-N coupling is observed.2 } 10 site, and hence no N-N coupling is observed.

We examine the effects of fusing two benzofurans to s-indacene (indacenodibenzofurans, IDBFs) and dicyclopenta[b,g]naphthalene (indenoindenodibenzofurans, IIDBFs) to control the strong antiaromaticity and diradical character of these core units. Synthesis via 3-functionalized benzofuran yields syn-IDBF and syn-IIDBF. syn-IDBF possesses a high degree of paratropicity, exceeding that of the parent hydrocarbon, which in turn results in strong diradical character for syn-IIDBF. In the case of the anti-isomers, synthesized via 2-substituted benzofurans, these effects are decreased; however, both derivatives undergo an unexpected ring-opening reaction during the final dearomatization step. All the results are compared to the benzothiophene-fused analogues and show that the increased electronegativity of oxygen in the syn-fused derivatives leads to enhancement of the antiaromatic core causing greater paratropicity. For syn-IIDBF increased diradical character results from rearomati-zation of the core naphthalene unit in order to relieve this paratropicity., (© 2021 Wiley-VCH GmbH.)

The oxidative addition of Pd to Si-H bonds is a crucial step in a variety of catalytic applications, and many aspects of this reaction are poorly understood. One important yet underexplored aspect is the electronic effect of silane substituents on reactivity. Herein we describe a systematic investigation of the formation of silyl palladium hydride complexes as a function of silane identity, focusing on electronic influence of the silanes. Using [(μ-dcpe)Pd] 2 (dcpe = dicyclohexyl(phosphino)ethane) and tertiary silanes, data show that equilibrium strongly favours products formed from electron-deficient silanes, and is fully dynamic with respect to both temperature and product distribution. A notable kinetic isotope effect (KIE) of 1.21 is observed with H/DSiPhMe 2 at 233 K, and the reaction is shown to be 0.5 th order in [(μ-dcpe)Pd] 2 and 1 st order in silane. Formed complexes exhibit temperature-dependent intramolecular H/Si ligand exchange on the NMR timescale, allowing determination of the energetic barrier to reversible oxidative addition. Taken together, these results give unique insight into the individual steps of oxidative addition and suggest the initial formation of a σ-complex intermediate to be rate-limiting. The insight gained from these mechanistic studies was applied to hydrosilylation of alkynes, which shows parallel trends in the effect of the silanes' substituents. Importantly, this work highlights the relevance of in-depth mechanistic studies of fundamental steps to catalysis., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Addressing the instability of antiaromatic compounds often involves protection with bulky groups and/or fusion of aromatic rings, thus decreasing paratropicity. We report four naphthothiophene-fused s -indacene isomers, one of which is more antiaromatic than parent s -indacene. This surprising result is examined computationally through nucleus-independent chemical shift XY calculations and experimentally via nuclear magnetic resonance spectroscopy, X-ray crystallography, ultraviolet-visible spectrophotometry, and cyclic voltammetry, with the latter two indicating that this molecule possesses the lowest highest occupied molecular orbital-lowest unoccupied molecular orbital energy gap observed for heterocycle-fused s -indacene.

Carbon-based materials-such as graphene nanoribbons, fullerenes, and carbon nanotubes-elicit significant excitement due to their wide-ranging properties and many possible applications. However, the lack of methods for precise synthesis, functionalization, and assembly of complex carbon materials has hindered efforts to define structure-property relationships and develop new carbon materials with unique properties. To overcome this challenge, we employed a combination of bottom-up organic synthesis and controlled polymer synthesis. We designed norbornene-functionalized cycloparaphenylenes (CPPs), a family of macrocycles that map onto armchair carbon nanotubes of varying diameters. Through ring-opening metathesis polymerization, we accessed homopolymers as well as block and statistical copolymers constructed from "carbon nanohoops" with a high degree of structural control. These soluble, sp 2 -carbon-dense polymers exhibit tunable fluorescence emission and supramolecular responses based on composition and sequence. This work represents an important advance toward bridging the gap between small molecules and functional carbon-based materials., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Chalaniline B [1-anilino-2,8-dihydroxy-3-(hydroxymethyl)xanthone], an antibiotic previously isolated from vorinostat-treated Chalara sp., was prepared in 7 steps from 2-hydroxyxanthone by a route incorporating regioselective oxidative transformations (bromination at C1/C3, ketone directed Pd(II)-catalyzed hydroxylation at C8), installation of the C1-anilino moiety by a regioselective Buchwald-Hartwig amination reaction from 1,3-dibromo-2,8-dimethoxyxanthone, and late-stage hydroxymethylation at C3 using a Stille cross-coupling. Biological evaluation of deshydroxymethylchalaniline B (1-anilino-2,8-dihydroxyxanthone) revealed MIC values of 8 μg mL -1 (25 μM) against both methicillin resistant S. aureus and B. subtilis .

From arid, high desert soil samples collected near Bend, Oregon, 19 unique bacteria were isolated. Each strain was identified by 16S rRNA gene sequencing, and their organic extracts were tested for antibacterial and antiproliferative activities. Noteworthy, six extracts (30 %) exhibited strong inhibition resulting in less than 50 % cell proliferation in more than one cancer cell model, tested at 10 μg/mL. Principal component analysis (PCA) of LC/MS data revealed drastic differences in the metabolic profiles found in the organic extracts of these soil bacteria. In total, fourteen potent antibacterial and/or cytotoxic metabolites were isolated via bioactivity-guided fractionation, including two new natural products: a pyrazinone containing tetrapeptide and 7-methoxy-2,3-dimethyl-4H-chromen-4-one, as well as twelve known compounds: furanonaphthoquinone I, bafilomycin C1 and D, FD-594, oligomycin A, chloramphenicol, MY12-62A, rac-sclerone, isosclerone, tunicamycin VII, tunicamycin VIII, and (6S,16S)-anthrabenzoxocinone 1.264-C., (© 2021 Wiley-VHCA AG, Zurich, Switzerland.)

Hydrogen sulfide (H 2 S) is an important biological signaling molecule and one of three established gasotransmitters. Upon oxidation, H 2 S can form reactive sulfur species (RSS) that play a central role in protein persulfidation. Here we report that a molybdenum tetrasulfide can react directly with hydrosulfide to form polysulfides and oxidize the Mo center. Specifically, [NBu 4 ][TpMoS(S 4 )] reacts with 2 equiv of [NBu 4 ][SH] to form [NBu 4 ][TpMoS 3 ]. Trapping experiments with BnBr confirm the formation of polysulfides, as evidenced by the direct trapping of Bn 2 S 2 . This work demonstrates new reaction pathways for H 2 S oxidation and RSS generation from metal-bound polysulfides that will increase our understanding of the potential roles that metals play in signaling processes.

The ability to alter optoelectronic and magnetic properties of molecules at a late stage in their preparation is in general a nontrivial feat. Here, we report the late-stage oxidation of benzothiophene-fused indacenes and dicyclopentanaphthalenes to their corresponding sulfone derivatives. We find that while such modifications increase the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gap to a small degree, other properties such as HOMO and LUMO energy levels, molecule paratropicity, and singlet-triplet energy gaps are influenced to a greater degree. The most surprising finding is a change of the bond alternation pattern within the s -indacene core of the sulfones. Computations corroborate the experimental findings and offer plausible explanations for these changes in molecular properties.

Toxoplasmosis is a potentially fatal infection for immunocompromised people and the developing fetus. Current medicines for toxoplasmosis have high rates of adverse effects that interfere with therapeutic and prophylactic regimens. Endochin-like quinolones (ELQs) are potent inhibitors of Toxoplasma gondii proliferation in vitro and in animal models of acute and latent infection. ELQ-316, in particular, was found to be effective orally against acute toxoplasmosis in mice and highly selective for T. gondii cytochrome b over human cytochrome b Despite its oral efficacy, the high crystallinity of ELQ-316 limits oral absorption, plasma concentrations, and therapeutic potential. A carbonate ester prodrug of ELQ-316, ELQ-334, was created to decrease crystallinity and increase oral bioavailability, which resulted in a 6-fold increase in both the maximum plasma concentration ( C max ) and the area under the curve (AUC) of ELQ-316. The increased bioavailability of ELQ-316, when administered as ELQ-334, resulted in efficacy against acute toxoplasmosis greater than that of an equivalent dose of ELQ-316 and had efficacy against latent toxoplasmosis similar to that of ELQ-316 administered intraperitoneally. Treatment with carbonate ester prodrugs is a successful strategy to overcome the limited oral bioavailability of ELQs for the treatment of toxoplasmosis., (Copyright © 2020 American Society for Microbiology.)

Molecules and materials that demonstrate large amplitude responses to minor changes in their local environment play an important role in the development of new forms of nanotechnology. Molecular daisy chains are a type of a mechanically interlocked molecule that are particularly sensitive to such changes in which, in the presence of certain stimuli, the molecular linkage enables muscle-like movement between a reduced-length contracted form and an increased-length expanded form. To date, all reported syntheses of molecular daisy chains are accomplished via passive-template methods, resulting in a majority of structures being switchable only through the addition of an exogenous stimuli such as metal ions or changes in pH. Here, we describe a new approach to these structural motifs that exploits a multi-component active-metal template synthesis to mechanically interlock two pi-rich nanohoop macrocycles into a molecular daisy chain that undergoes large conformational changes using thermal energy., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Porous molecular materials combine benefits such as convenient processability and the possibility for atom-precise structural fine-tuning which makes them remarkable candidates for specialty applications in the areas of gas separation, catalysis, and sensing. In order to realize the full potential of these materials and guide future molecular design, knowledge of the transition from molecular properties into materials behavior is essential. In this work, the class of compounds termed cycloparaphenylenes (CPPs)-shape-persistent macrocycles with built-in cavities and radially oriented π-systems-was selected as a conceptually simple class of intrinsically porous nanocarbons to serve as a platform for studying the transition from analyte sorption properties of small aggregates to those of bulk materials. In our detailed investigation, two series of CPPs were probed: previously reported hoop-shaped [ n ]CPPs and a novel family of all-phenylene figure-8 shaped (lemniscal) bismacrocycles, termed spiro[ n , n ]CPPs. A series of nanocarbons with different macrocycle sizes and heteroatom content have been prepared by atom-precise organic synthetic methods, and their structural, photophysical, and electronic attributes were disclosed. Detailed experimental studies (X-ray crystallography, gas sorption, and quartz-crystal microbalance measurements) and quantum chemical calculations provided ample evidence for the importance of the solid-state arrangement on the porosity and analyte uptake ability of intrinsically porous molecular nanocarbons. We demonstrate that this molecular design principle, i.e., incorporation of sterically demanding spiro junctions into the backbone of nanohoops, enables the manipulation of solid-state morphology without significantly changing the nature and size of the macrocyclic cavities. As a result, the novel spiro[ n , n ]CPPs showed a remarkable performance as high affinity material for vapor analyte sensing.

Alkyltin clusters are exploited in nanolithography for the fabrication of microelectronics. The alkyltin Keggin family is unique among Keggin clusters across the periodic table; its members appear to favor the lower-symmetry β and γ isomers rather than the highly symmetrical α and ε isomers. Therefore, the alkyltin Keggin family may provide important fundamental information about the formation and isomerization of Keggin clusters. We have synthesized and structurally characterized a new butyltin Keggin cluster with a tetrahedral Ca 2+ center, fully formulated [(BuSn) 12 (CaO 4 )(OCH 3 ) 12 (O) 4 (OH) 8 ] 2+ (β-CaSn 12 ). The synthesis is a simple one-step process. Extensive solution characterization including electrospray ionization mass spectrometry, small-angle X-ray scattering, and multinuclear ( 1 H, 13 C, and 119 Sn) nuclear magnetic resonance shows β-CaSn 12 is essentially phase-pure and stable. This differs from the previously reported Na-centered analogues that always form a mixture of β and γ isomers, with facile interconversion. Therefore, this study has clarified prior confusion over complex spectroscopic and crystallographic characterization of the Na-centered analogues. Density functional theory calculations showed the following stability order: γ-CaSn 12 < γ-NaSn 12 < β-CaSn 12 < β-NaSn 12 . The β analogue is always more stable than the γ analogue, consistent with experiment. Notable outcomes of this study include a rare tetrahedral Ca coordination, a Na-free alkyltin cluster (important for microelectronics manufacturing), and a better understanding of Keggin families built of different metal cations.

Uranyl peroxide capsules are a fascinating class of polyoxometalates (POMs), discovered only in the 21st century. Understanding the reactivity between peroxide, alkali cations, and uranyl in alkaline solutions is important in nuclear science disciplines including mineralogy, nuclear energy, and legacy nuclear wastes. Here, we have developed a general procedure to isolate different fragments of the uranyl-peroxide POM capsules, using organic solvents to partially remove K + salts from crude solids of the monomer building block UO 2 (O 2 ) 3 4- ( K-U 1 ), leading to stabilization of these reactive fragments. Higher polarity organic solvents remove more K + salts from the crude solid, owed to higher solubility, resulting in more extensive linking of uranyl peroxide building units. By this strategy we have isolated and structurally characterized a dimer K 6 [(UO 2 ) 2 (O 2 ) 4 (OH) 2 ]·7H 2 O ( K-U 2 ) and a hexamer face frequently observed in the capsules, K 12 [(UO 2 ) 6 (O 2 ) 9 (OH) 6 ]· x H 2 O ( K-U 6 ). Comparing experimental and computed Raman spectra shows that these intermediates crystallize by a solid-to-solid transformation, via polymerization of the monomer building block. By small-angle X-ray scattering (SAXS), we track the conversion of the fragments to POM capsules; the reaction rate increases from K-U 1 (days) < K-U 2 (hours) < K-U 6 (instantaneous). This study provides a general synthetic procedure to isolate metastable uranyl peroxide oligomers and control the oligomerization, which will be later applied to systems with the heavier alkalis that are even less stable.

Inclusion of quinoidal cores in conjugated hydrocarbons is a common strategy to modulate the properties of diradicaloids formed by aromaticity recovery within the quinoidal unit. Here we describe an alternative approach of tuning of diradical properties in indenoindenodibenzothiophenes upon anti → syn isomerism of the benzothiophene motif. This alters the relationship of the S atom with the radical center from linear to cross conjugation yet retains the same 2,6-naphtho conjugation pattern of the rearomatized core. We conduct a full comparison between the anti and syn derivatives based on structural, spectroscopic, theoretical, and magnetic measurements, showing that these systems are stable open-shell singlet diradicaloids that only access their triplet state at elevated temperatures.

Cyclophanes are a venerable class of macrocyclic and cage compounds that often contain unusual conformations, high strain, and unusual properties. However, synthesis of complex, functional derivatives remains difficult due to low functional group tolerance, high dilution, extreme reaction conditions, and sometimes low yields using traditional stepwise synthetic methods. "Design of experiments" (DOE) is a method employed for the optimization of reaction conditions, and we showcase this approach to generate a dramatic increase in the yield of specific targets from two different self-assembling systems. These examples demonstrate that DOE provides an additional tool in tuning self-assembling, dynamic covalent systems., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report the synthesis and characterization of P-phenyl modified phosphorus- and nitrogen-containing phosphaquinolinone heterocycles. The change from -OPh to -Ph results in a marked increase in the quantum yield of the scaffold as well as a moderate red-shifting of the emission. While calculations suggest that π to π* transitions are dominant, intramolecular charge transfer (ICT) also contributes in the excited state. Solution- and solid-state studies of the dimerization of this new congener to the P-phenoxy variant are also reported, showing retention of the dimerization behavior in this scaffold.

The scalable production of homogeneous, uniform carbon nanomaterials represents a key synthetic challenge for contemporary organic synthesis as nearly all current fabrication methods provide heterogeneous mixtures of various carbonized products. For carbon nanotubes (CNTs) in particular, the inability to access structures with specific diameters or chiralities severely limits their potential applications. Here, we present a general approach to access solid-state CNT mimic structures via the self-assembly of fluorinated nanohoops, which can be synthesized in a scalable, size-selective fashion. X-ray crystallography reveals that these CNT mimics exhibit uniform channel diameters that are precisely defined by the diameter of their nanohoop constituents, which self-assemble in a tubular fashion via a combination of arene-pefluoroarene and C-H-F interactions. The nanotube-like assembly of these systems results in capabilities such as linear guest alignment and accessible channels, both of which are observed in CNTs but not in the analogous all-hydrocarbon nanohoop systems. Calculations suggest that the organofluorine interactions observed in the crystal structure are indeed critical in the self-assembly and robustness of the CNT mimic systems. This work establishes the self-assembly of carbon nanohoops via weak interactions as an attractive means to generate solid-state materials that mimic carbon nanotubes, importantly with the unparalleled tunability enabled by organic synthesis.

An unusual trithioorthoformate-capped cyclophane cage was assembled via antimony-activated iodine oxidation of thiols as confirmed by 1 H-NMR spectroscopy and X-ray crystallography. The disulfide bridges can undergo desulfurization with hexamethylphosphorous triamide (HMPT) at ambient temperature to capture a trithioether cyclophane cage capped by the trithioorthoformate. In both cages a methine proton points directly into the small cavity. This unexpected structure is hypothesized to have formed as a result of haloform insertion during oxidation., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We expand on our approach combining dynamic covalent self-assembly and sulfur extrusion to synthesize new biphenyl-linked disulfide and thioether macrocycles, which are variants of the venerable phenyl-bridged paracyclophanes. We then advance this strategy further to use two different thiols in tandem to provide new, elusive unsymmetrical disulfides which can also be trapped as unsymmetrical thioether "nanohoops". This approach enables substantial amplification of two unsymmetrical trimers out of a library of at least 21 possible macrocycles of various sizes.

A straightforward method for the preparation of non-K region fused phosphorus- and nitrogen-containing (PN)-heterocyclic pyrenes has been accomplished. Their structural, photophysical, and electrochemical properties have been fully investigated. The described compounds exhibit intriguing redox properties and show strong photoluminescence with a wide range of tunable emission colors, with λ em ranging from blue at 459 nm to red at 622 nm in CH 2 Cl 2 solution.

Group V Nb-polyoxometalate (Nb-POM) chemistry generally lacks the elegant pH-controlled speciation exhibited by group VI (Mo, W) POM chemistry. Here three Nb-POM clusters were isolated and structurally characterized; [Nb 14 O 40 (O 2 ) 2 H 3 ] 14- , [((UO 2 )(H 2 O)) 3 Nb 46 (UO 2 ) 2 O 136 H 8 (H 2 O) 4 ] 24- , and [(Nb 7 O 22 H 2 ) 4 (UO 2 ) 7 (H 2 O) 6 ] 22- , that effectively capture the aqueous Nb-POM species from pH 7 to pH 10. These Nb-POMs illustrate a reaction pathway for control over speciation that is driven by counter-cations (Li + ) rather than pH. The two reported heterometallic POMs (with UO 2 2+ moieties) are stabilized by replacing labile H 2 O/HO-Nb=O with very stable O=U=O. The third isolated Nb-POM features cis-yl-oxos, prior observed only in group VI POM chemistry. Moreover, with these actinide-heterometal contributions to the burgeoning Nb-POM family, it now transects all major metal groups of the periodic table., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A family of naphtho[2,1- e]-fused 1,2-azaphosphorine 2-oxides that contain electron-withdrawing and -donating substituents on the 3-phenyl groups has been prepared and characterized. This new series of phosphorus- and nitrogen-containing heterocycles is brightly fluorescent with tunable emission wavelengths (λ em = 441-493 nm, Φ F = 0.19-0.93). Their strong self-dimerization behavior through N-H and P═O hydrogen bond donors/acceptors was investigated experimentally and theoretically. The pendant phenyl group can be used to modify the intrinsic optoelectronic properties as well as the self-association of the PN-heterocycles. The results presented herein are expected to enable the development of new photofunctional materials and provide important insights in diverse areas of supramolecular chemistry.

The serendipitous isolation of very small amounts of two naphthocyclobutadiene (NCB) derivatives has led to the computational re-examination of the electrocyclization of Z,Z-3,5-octadiene-1,7-diyne as well as the experimental and computational study of diethynylindeno[2,1-a]fluorene derivatives that contain the 3,5-octadiene-1,7-diyne motif as part of a larger π-framework. In both cases the calculated potential energy surface strongly implicates two successive electrocyclic reactions to afford the antiaromatic products. With the octadienediyne fragment locked in the reactive conformation, the postulated diethynylindeno[2,1-a]fluorene intermediates afford the NCBs in modest to good yields. X-ray crystallography of four NCBs as well as NICS-XY scan calculations show that the paratropic motif is located primarily in the benzocyclobutadiene fragment within the larger π-scaffold., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The unique optoelectronic properties and smooth, rigid pores of macrocycles with radially oriented π systems render them fascinating candidates for the design of novel mechanically interlocked molecules with new properties. Two high-yielding strategies are used to prepare nanohoop [2]rotaxanes, which owing to the π-rich macrocycle are highly emissive. Then, metal coordination, an intrinsic property afforded by the resulting mechanical bond, can lead to molecular shuttling as well as modulate the observed fluorescence in both organic and aqueous conditions. Inspired by these findings, a self-immolative [2]rotaxane was then designed that self-destructs in the presence of an analyte, eliciting a strong fluorescent turn-on response, serving as proof-of-concept for a new type of molecular sensing material. More broadly, this work highlights the conceptual advantages of combining compact π-rich macrocyclic frameworks with mechanical bonds formed via active-template syntheses., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A set of fully-conjugated indenofluorenes has been synthesized and confirmed by solid-state structure analysis. The indeno[2,1-c]fluorenes and their benzo-fused analogues all contain the antiaromatic as-indacene core. The molecules possess high electron affinities and show a broad absorption that reaches into the near-IR region of the electromagnetic spectrum. All of the featured compounds reversibly accept up to two electrons as revealed by cyclic voltammetry. Analysis of molecule tropicity using NICS-XY scan calculations shows that, while the as-indacene core is less paratropic than s-indacene, benz[a]-annulation further reduces the antiaromaticity of the core. Antiaromatic strength of the as-indacene core can also be tuned by the position of fusion of additional arenes on the outer rings., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Isolating Fe(III) clusters from water without stabilizing ligands is significantly challenged by the high acidity of Fe 3+ -bound water, leading to uncontrolled precipitation of iron oxyhydroxides. Here we demonstrate a freeze-drying solvent-exchange method that enabled the isolation of a metastable Fe(III) sulfate decameric cluster formulated [Fe 10 O 2 (SO 4 ) 12 (OCH 3 ) 2 ]·14CH 3 OH (Fe 10 ). Without stabilization by solvent-exchange, the aqueous species undergoes rapid conversion to the iron sulfate mineral schwertmannite. Monitoring the hydrolysis process from cluster intermediates to schertmannite by small-angle X-ray scattering, we observe the progression from Fe 10 to 37 Å soluble nanoparticles prior to the precipitation process. This condensation behavior of Fe 10 is further exploited to develop a simple laboratory synthesis of schwetmannite. In addition, we demonstrate the versatility of the freeze-drying solvent-exchange method by isolating Al(III), Zn(II), and Cd(II) substituted Fe(III) sulfate clusters. The freeze-drying solvent-exchange method provides a unique opportunity to isolate cluster intermediates and models to aid in our understanding of metal-ion hydrolysis processes in environmental, material science, and geological studies.