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The anionic polyaddition of methyl‐substituted 1,1‐diphenylethylene derivatives, catalyzed by lithium diisopropylamide, was examined. Polymerization of the monomer was conducted at 50°C in THF with the addition of diisopropylamine. NMR and MALDI‐TOF‐MS analyses of the obtained polymer indicate that polymerization proceeded via a polyaddition reaction, in other words, repetition of the lithium amide‐induced metalation reaction of the monomer at the methyl group and the subsequent nucleophilic addition reaction of the corresponding benzyllithium with the vinyl group in the monomer. On the other hand, the unsubstituted diphenylethylene monomer could not be polymerized by the same reaction condition. Consequently, the resulting polymer was indeed obtained by an anionic polyaddition mechanism. In conclusion, a novel hydrocarbon polymer containing a phenyl group in the main chain of the repeating unit was successfully obtained from a methyl‐substituted 1,1‐diphenylethylene monomer. [ABSTRACT FROM AUTHOR]

A series of metalated porous organic polymers (POPs) derived from tetraphenylporphyrin (TPP) was synthesized, and the specific surface areas, selectivities for CO2 over N2, and conversion properties of the POPs were investigated. The metallo-tetraphenylporphyrin-based porous organic polymers were characterized using FT-IR, 13C-NMR, TGA, XRD, XPS, HR-FESEM, and EDX. Among the five catalysts studied, non-metalated TPP-based POP exhibited the highest BET surface area of 524.04 m2g−1, whereas the Ni(II)TPP-based POP had the greatest CO2/N2 selectivity at both 298 and 323 K. In terms of the catalytic efficiency for the conversion of styrene oxide to styrene carbonate using CO2, 2HPOP exhibited the highest yield of 91.67%, while the yield obtained with the metalated POPs was approximately 20%. This result suggests that the catalytic efficiency for CO2 conversion is determined by both the selectivity and surface area of the metalated POPs. Moreover, the improvement in the CO2/N2 selectivity resulting from metalation did not play a dominant role in counterbalancing and surpassing the decrease in porosity. [ABSTRACT FROM AUTHOR]

A highly crystalline and robust Zr-hydroxamate metal–organic framework (MOF) was prepared from a pyrazine-based ligand, featuring abundant N,N′ chelating sites. High-degree Pd(II) metalation of the MOF was achieved through straightforward postsynthetic modification, with detailed coordination chemistry elucidated spectroscopically. The Pd-functionalized MOF was then studied as a heterogeneous Suzuki–Miyaura catalyst, through combined experimental/computational methods. [ABSTRACT FROM AUTHOR]

Invasive fungal diseases affect more than two million people worldwide. The increasing incidence of invasive fungal infections is the result of many factors, including an increase in the resistance to current drugs. As such, there is an urgent need to obtain new drugs that are efficient, selective, and able to overcome existing resistance mechanisms. Candida yeasts are responsible for more than 70% of all nosocomial invasive fungal diseases. In this work, we describe the synthesis of nickel (II)(NHC) complexes based on xanthines, by direct metalation of xanthinium salts with nickelocene NiCp2to yield [NiCpI(NHC)] complexes. For methyl caffeine, a biscarbene complex [NiCp(NHC)2]+is also formed, resulting from carbene dissociation from the corresponding monocarbene. [NiCpI(NHC)] complexes are active as antifungals for Candida yeasts and show toxicity for human cells (HeLa) that is dependent on the substitution of N7 of the xanthine moiety. The biscarbene complex 5[NiCp(NHC)2]+is highly selective for Candida glabrata and shows very low toxicity for human cells, being a promising candidate for selective treatment of C. glabrata infections. [ABSTRACT FROM AUTHOR]

Functionalized ferrocene derivatives have a wide range of applications across various scientific fields. Although significant progress has been made in synthesizing 1,2‐disubstituted ferrocene derivatives, the preparation of 1,3‐disubstituted ferrocenes remains challenging. Recently, however, several powerful synthetic approaches to 1,3‐disubstituted ferrocenes have been reported. This review aims to present the evolution of these synthetic methods, from initial stoichiometric approaches to the more recent catalytic methodologies. [ABSTRACT FROM AUTHOR]

Organocalcium compounds are highly reactive reagents whereas the alkaline-earth metal itself is a weak reductant. This discrepancy hampered a straightforward development of an organocalcium chemistry. The in situ generation of the highly reactive organocalcium reagent and immediate metalation of a H-acidic compound (iGMM) or addition onto a polar π-system (iGAM) offers not only a loophole to organocalcium reagents but opens the entry to a rich organic chemistry of this non-toxic and globally abundant alkaline-earth metal, being competitive to the organolithium chemistry. [ABSTRACT FROM AUTHOR]

Two new C,O-bidentate chelating triazolylidene-phenolate ligands were synthesized that feature a diisopropylphenyl (dipp) and an adamantyl (Ad) substituent respectively on the triazole scaffold. Subsequent metalation afforded iron(II) complexes [Fe(C^O)2] that are active catalysts for the intramolecular C-H amination of organic azides. When compared to the parent complex containing a triazolylidene with a mesityl substituent (Mes) the increased steric bulk led to slightly lower activity (TOFmax = 23 h-1 vs. 30 h-1), however selectivity towards pyrrolidine formation increases from 92% up to >99%. Kinetic studies indicate that the mechanism is similar in all three complexes and includes a half-order dependence in [Fe(C^O)2], congruent with the involvement of a dimetallic catalyst resting state within this catalyst class. Structural analysis suggests that enhanced bulkiness disfavors N2 loss and nitrene formation, yet shields the nitrene from intermolecular processes and thus favors intramolecular nitrene insertion into the C-H bond. This model rationalizes the high selectivity and the lower reaction rate observed with dipp and with Ad substituents on the ligand. [ABSTRACT FROM AUTHOR]

Pyridine‐directed regioselective C−H hydroxymethylation to pyridones and isoquinolones using para‐formaldehyde has been developed under manganese catalysis, offering a wide variety of hydroxymethylated products in 40–85% yields. This operationally simple methodology proceeds in one step using an earth‐ abundant first‐row transition metal‐catalyst without the generation of unwanted salt wastes. A mechanistic study revealed that the C−H metalation step is reversible but not the rate‐determining step. The introduction of hydroxymethyl group in the biologically relevant scaffolds could be used as an intermediate for valuable synthetic transformations. [ABSTRACT FROM AUTHOR]

Although carbanions, which are usually regarded as reactive species and powerful metalation reagents, can be stabilized through choice of the substitution pattern, they have rarely been considered for the design of weakly coordinating anions (WCA). Here, we report on an evaluation of the potential of a series of differently substituted carbanions to serve as WCA by computational methods. This led us to the synthesis of the water‐ and air‐stable allyl anion 1 with triflyl and 3,5‐bis(trifluoromethyl)phenyl (ArF) moieties, which can be isolated in high yields even on a gram‐scale. Single crystal X‐ray crystallography and NMR studies confirmed the weak coordination ability of the anion by showing negligible or only weak interactions with different cations. This property enabled the application of 1 in the stabilization of reactive group 14 and 15 cations. In addition to the crystallization of a phosphenium cation, the first all‐carbon salt with a non‐aromatic carbanion is reported, which revealed to be a convenient reagent for hydride abstraction such as from silanes. Overall, this work demonstrates the so far untapped potential of carbanions as WCA, that are accessible with a variety of different cations for various applications. [ABSTRACT FROM AUTHOR]

The metalation of 1,3-diaryl-4-(arylsulfanyl)imidazolium and 1,3-diaryl-4-(arylsulfonyl)imidazolium chlorides with copper(I) oxide has been studied. The resulting Cu/NHC complexes have been studied as catalysts for the carboxylation of phenylacetylene, benzoxazole, and benzothiazole. The main patterns of this reaction behavior and the dependence of the catalysis efficiency on the NHC structure were revealed. [ABSTRACT FROM AUTHOR]

A chelating N-heterocyclic carbene palladium complex (3) containing N-(3-bromopropyl)-N'-thioether di-functionalized imidazol-2-ylidene was synthesized by the direct metalation of N-(3-bromopropyl)-N'-thioether di-functionalized imidazolium bromide (2) with Pd(OAc)2 in the presence of NaOAc and NaBr at room temperature using CH2Cl2 as solvent. The structure was characterized by NMR, HR-MS and X-ray crystallography. The results showed that complex 3 consists of two independent molecules with configuration of SC, RS in molecule a, and SC, SS in molecule b, respectively. The crystal is triclinic, P1 space group, with a = 8.4815(3), b = 8.6338(3), c = 19.2371(7) Å, V = 1245.66(8) Å3, and Z = 2 (at 293(2)K). A chelating N-heterocyclic carbene palladium complex (3) consists of two independent molecules with configurations of SC, RS and SC, SS respectively has been synthesized through the direct metalation of the precursor imidazolium bromide (2). [ABSTRACT FROM AUTHOR]

Exploration of expanded porphyrins with unprecedented reactivities has remained important. Here [22]pentaphyrins(2.0.1.1.0) were synthesized as a constitutional isomer of sapphyrin by acid‐catalyzed cyclization of 1,14‐dibromo‐5,10‐diaryltripyrrin with 1,2‐di(pyrro‐2‐ly)ethenes. These pentaphyrins display roughly planar structures and varying aromaticities depending upon the vinylene structures. The 19,20‐ditolyl pentaphyrin gave an N‐fused product and an unprecedented pyrrole‐rearranged product, depending upon the oxidation conditions. Remarkably, upon the metalation with CuCl, the N‐fused product and the pyrrole‐rearranged product afforded an inner β‐β coupled face‐to‐face CuII complex dimer and an outer β‐β coupled lateral CuII complex dimer, respectively, in fairly good yields. Further, [22]pentaphyrin(2.0.1.1.0) fused with a NiII porphyrin was effectively dimerized upon oxidation with MnO2 to give a 16–16' directly linked dl‐dimer. [ABSTRACT FROM AUTHOR]

While organoelement compounds of lithium, sodium and potassium have been much studied for decades and consequently have found forests of applications, those of the heavier alkali metals, rubidium and caesium would barely manage to fill a tree. However, recently the literature has seen some little growth spurts with these metals, hinting at a possible fertile future in areas such as homogeneous catalysis provided more work is put into their fundamental development. Here we report the synthesis and crystal structures of lithium, rubidium and caesium derivatives of the ureaphosphane Ph2PCH2CH2NHC(=O)NHPh, chosen because it offers O, N, P, and π‐coordination sites. Though one may expect such alkali metal compounds to be essentially similar, the caesium complex has novel features where Cs+ engages in a side‐on coordination to the C=O bond and in a weak bond to the P centre, both of which are absent in the Rb structure. Less surprisingly, the lithium derivative is tetrameric in contrast to the infinite networks of the rubidium and caesium structures. All alkali metal derivatives were made with deprotonating the ureaphosphane by a suitable base, including the sodium and potassium complexes though these two complexes could not be obtained in a crystalline form. [ABSTRACT FROM AUTHOR]

Profiting from the dual high basicity and nucleophilicity of organosodium complexes, here we report the stepwise lateral metalation of a wide range of alkyl arenes (MeAr), mediated by hydrocarbon‐soluble NaCH2SiMe3 ⋅ PMDETA (PMDETA=N,N,N',N",N"‐pentamethyldiethylenetriamine), followed by nucleophilic addition to diarylethenes of the newly generated NaCH2Ar ⋅ PMDETA complexes. This method grants access to a range of functionalised hydrocarbons in excellent yields and can be upgraded to catalytic regimes when using trans‐stilbene, a 10 mol% of the alkyl sodium base and toluene as a solvent. Extending this approach to aromatic ketones leads to the formation of stilbenes under mild reaction conditions, resulting from the deprotonative coupling of toluenes with ketones. Combining spectroscopic studies with the trapping and characterisation of key reaction intermediates, mechanistic insights have been gained, advancing the understanding of coordination effects in organosodium chemistry, and shedding light on their special reactivity profiles. [ABSTRACT FROM AUTHOR]

A sterically encumbered dinuclear amidinato magnesium hydride 3 with bridging hydrido ligands was synthesized from the metalation of the corresponding amidine 1 with dibutylmagnesium and subsequent treatment with phenylsilane. This complex reacts stoichiometrically with 1 atm of carbon dioxide at room temperature in tetrahydrofuran (THF) to the corresponding bis(thf) adduct of the dinuclear formate complex 4‐2 thf with bridging formate anions. This complex is stable in THF at 60 °C for more than 16 hours but decomposes into the amidine 1 upon removal of ligated thf ligands. Complex 3 efficiently catalyzes the reduction of carbon dioxide with 9‐BBN, yielding bis(boryl)acetal (R2BO)2CH2, and with silanes H4‐nSiPhn (n=1, 2, and 3). The bis(silyl)acetal is quantitatively accessible for Ph3SiH (n=3) whereas during the reduction of CO2 with hydrogen‐richer silanes (n=1, 2) siloxanes form and methane evolves. [ABSTRACT FROM AUTHOR]

Synthetic multimetallic porphyrinoids are potential candidates in catalysis, molecular magnetism and as modern optoelectronic materials. Introducing electronic heterogenity in these multi‐porphyrinoids shall bring in novel electronic and redox characteristics. In this direction, herein we report four discrete Corrole‐Porphyrin‐Corrole C[10] ⋅ P[5,15] ⋅ C[10] hybrids that have both corrole and porphyrin units covalently connected together. Metal ions in diverse oxidation states have been incorporated into respective cores to achieve homo and heterotrinuclear metal complexes. Selective metalation at the porphyrin and corrole cores was achieved by step‐wise insertion of Zn(II)/Cu(II), Zn(II)/Ga(III) and Cu(II)/Cu(II) ions to suit the dianionic and trianionic pockets, respectively. Single crystal X‐ray diffraction studies reveal the solid‐state structural evidence for both homo‐, and hetero‐trinuclear metal complexes. The Zn(II) and Ga(III) moieties have two distinct geometries in the molecular assembly. The geometry of Zn(II) at the porphyrin core is a perfect square planar, whereas the Ga(III) geometry at the corrole is square pyramidal with pyridine as an axial ligand. In case of homotrinuclear Cu(II) complex, the Cu(II) ions adopt square planar geometry irrespective of the core. Similar to all porphyrin trimers, C[10] ⋅ P[5,15] ⋅ C[10] trimers exhibit significant excitonic coupling between corrole and porphyrin units in the absorption spectra. The cyclic voltametric investigations also reveal electronic coupling between the individual chromophores despite the non‐coplanar arrangement amongst the individual macrocycles. [ABSTRACT FROM AUTHOR]

During the photochemical CO2 reduction reaction, CO2 adsorption on the catalyst's surface is a crucial step where the binding mode of the [metal‐CO2] adduct directs the product selectivity and efficiency. Herein, an ionic TiO2 nanostructure stabilized by polyoxometalates (POM), ([POM]x@TiO2), is prepared and the sodium counter ions present on the surface to balance the POMs' charge are replaced with copper(II) ions, (Cux[POM]@TiO2). The microscopic and spectroscopic studies affirm the copper exchange without altering the TiO2 core and weak coordination of copper (II) ions to the POMs' surface. Band structure analysis suggests the photo‐harvesting efficiency of the TiO2 core with the conduction band edge higher than the reduction potential of CuII/I and multi‐electron CO2 reduction potentials. Photochemical CO2 reduction with Cux[POM]@TiO2 results in 30 μmol gcat.−1 CO (79 %) and 8 μmol gcat−1 of CH4 (21 %). Quasi‐in‐situ Raman study provides evidence in support of CO2 adsorption on the Cux[POM]@TiO2 surface. 13C and D2O labeling studies affirm the {Cu‐[CO2]−} adduct formation. Despite the photo‐harvesting ability of Nax[POM]@TiO2 itself, the poor CO2 adsorption ability of sodium ions highlights the crucial role of copper ion CO2 photo‐reduction. Characterization of the {M‐[η2‐CO2]−} species via surface tuning validates the CO2 activation and photochemical reduction pathway proposed earlier. [ABSTRACT FROM AUTHOR]

There is a pressing need for methods that can connect enantioenriched organic compounds with readily accessible building blocks via asymmetric functionalization of unreactive chemical bonds in organic synthesis and medicinal chemistry. Herein, the asymmetric chemoselective cleavage of two unactivated C(Ar)−O bonds in the same molecule is disclosed for the first time through an unusual nickel‐catalyzed carbomagnesiation. This reaction facilitates the evolution of a novel atroposelective ring‐opening difunctionalization. Utilizing readily available dibenzo bicyclic substrates, diverse valuable axially chiral biaryls are furnished with high efficiencies. Synthetic elaborations showcase the application potential of this method. The features of this method include good atom‐economy, multiple roles of the nucleophile, and a simple catalytic system that enables the precise magnesiation of an α‐C(Ar)−O bond and arylation of a β‐C(Ar)−O bond. [ABSTRACT FROM AUTHOR]

C−H metalation is the most efficient method to prepare aryl–zinc and –aluminium complexes that are ubiquitous nucleophiles. Virtually all C−H metalation routes to form Al/Zn organometallics require stoichiometric, strong Brønsted bases with no base‐catalyzed reactions reported. Herein we present a catalytic in amine/ammonium salt (Et3N/[(Et3N)H]+) C−H metalation process to form aryl‐zinc and aryl‐aluminium complexes. Key to this approach is coupling an endergonic C−H metalation step with a sufficiently exergonic dehydrocoupling step between the ammonium salt by‐product of C−H metalation ([(Et3N)H]+) and a Zn−H or Al−Me containing complex. This step, forming H2/MeH, makes the overall cycle exergonic while generating more of the reactive metal electrophile. Mechanistic studies supported by DFT calculations revealed metal‐specific dehydrocoupling pathways, with the divergent reactivity due to the different metal valency (which impacts the accessibility of amine‐free cationic metal complexes) and steric environment. Notably, dehydrocoupling in the zinc system proceeds through a ligand‐mediated pathway involving protonation of the β‐diketiminate Cγ position. Given this process is applicable to two disparate metals (Zn and Al), other main group metals and ligand sets are expected to be amenable to this transition metal‐free, catalytic C−H metalation. [ABSTRACT FROM AUTHOR]

Typified by LiTMP and TMPMgCl.LiCl, (TMP=2,2,6,6‐tetramethylpiperidide), s‐block metal amides have found widespread applications in arene deprotonative metalation. On the contrary, transition metal amides lack sufficient basicity to activate these substrates. Breaking new ground in this field, here we present the synthesis and full characterisation of earth‐abundant transition metals M(TMP)2 (M=Fe, Co). Uncovering a new reactivity profile towards fluoroarenes, these amide complexes can promote direct M−H exchange processes regioselectively using one or two of their basic amide arms. Remarkably, even when using a perfluorinated substrate, selective C‐H metalation occurs leaving C−F bonds intact. Their kinetic basicity can be boosted by LiCl or NBu4Cl additives which enables formation of kinetically activated ate species. Combining spectroscopic and structural studies with DFT calculations, mechanistic insights have been gained on how these low polarity metalation processes take place. M(TMP)2 can also be used to access ferrocene and cobaltocene by direct deprotonation of cyclopentadiene and undergo efficient CO2 insertion of both amide groups under mild reaction conditions. [ABSTRACT FROM AUTHOR]

Metalation of metal–organic frameworks (MOFs) has been developed as a prominent strategy for materials functionalization for pore chemistry modulation and property optimization. By introducing exotic metal ions/complexes/nanoparticles onto/into the parent framework, many metallized MOFs have exhibited significantly improved performance in a wide range of applications. In this review, we focus on the research progress in the metalation of metal–organic frameworks during the last five years, spanning the design principles, synthetic strategies, and potential applications. Based on the crystal engineering principles, a minor change in the MOF composition through metalation would lead to leveraged variation of properties. This review starts from the general strategies established for the incorporation of metal species within MOFs, followed by the design principles to graft the desired functionality while maintaining the porosity of frameworks. Facile metalation has contributed a great number of bespoke materials with excellent performance, and we summarize their applications in gas adsorption and separation, heterogeneous catalysis, detection and sensing, and energy storage and conversion. The underlying mechanisms are also investigated by state-of-the-art techniques and analyzed for gaining insight into the structure– property relationships, which would in turn facilitate the further development of design principles. Finally, the current challenges and opportunities in MOF metalation have been discussed, and the promising future directions for customizing the next-generation advanced materials have been outlined as well. [ABSTRACT FROM AUTHOR]

Series of 5-substituted alkyl 2-[(2-ethoxy-2-oxoethyl)sulfanyl]methyl- and 2-[(2-ethoxy-2-oxoethyl)(methyl)amino]methylfuran-3-carboxylates have been synthesized and intramolecular ester condensation of these compounds has been investigated. It has been shown that sulfides, when heated with sodium foil in benzene, undergo cyclization to give sodium salts of 2-substituted ethyl 4-oxo-4,7-dihydro-5H-thiopyrano[3,4-b]furan-5-carboxylates. Upon long boiling under the same conditions, sarcosine esters form sodium salts of 2-substituted ethyl 6-methyl-4-oxo-4,5,6,7-tetrahydrofuro[2,3-с]pyridine-5-carboxylates. Salts of the derivatives of dihydrothiopyrane series exist in the carbanion form, while these of tetrahydrofuropyridine derivatives are enolates. The reactions of these salts with methyl iodide and acetyl chloride predominantly yield the products of С-alkylation and С-acylation in the former case, affording the enolates in the latter case. Influence of substituents in position 5 of the furan ring on the direction of metalation and the possibility of cyclization of (3-alkoxycarbonylfur-2-yl)methylsulfanylacetates and N-(3-alkoxycarbonylfur-2-yl)methylsarcosinates into the corresponding fused systems has been observed. [ABSTRACT FROM AUTHOR]

The synthesis and structural characterization of an electron poor Au(III) trication bearing 2 imidazole and 2 acetonitrile ligands is described. The new complex is capable of aryl C–H metalation with the formation of a monomesitylene complex and also demonstrated to be highly oxidizing in the rapid room temperature conversion of cyclohexene to benzene. [ABSTRACT FROM AUTHOR]

Studies have determined that nonredox enzymes that are cofactored with Fe(II) are the most oxidant-sensitive targets inside Escherichia coli. These enzymes use Fe(II) cofactors to bind and activate substrates. Because of their solvent exposure, the metal can be accessed and oxidized by reactive oxygen species, thereby inactivating the enzyme. Because these enzymes participate in key physiological processes, the consequences of stress can be severe. Accordingly, when E. coli senses elevated levels of H2O2, it induces both a miniferritin and a manganese importer, enabling the replacement of the iron atom in these enzymes with manganese. Manganese does not react with H2O2 and thereby preserves enzyme activity. In this study, we examined several diverse microbes to identify the metal that they customarily integrate into ribulose-5-phosphate 3-epimerase, a representative of this enzyme family. The anaerobe Bacteroides thetaiotaomicron, like E. coli, uses iron. In contrast, Bacillus subtilis and Lactococcus lactis use manganese, and Saccharomyces cerevisiae uses zinc. The latter organisms are therefore well suited to the oxidizing environments in which they dwell. Similar results were obtained with peptide deformylase, another essential enzyme of the mononuclear class. Strikingly, heterologous expression experiments show that it is the metal pool within the organism, rather than features of the protein itself, that determine which metal is incorporated. Further, regardless of the source organism, each enzyme exhibits highest turnover with iron and lowest turnover with zinc. We infer that the intrinsic catalytic properties of the metal cannot easily be retuned by evolution of the polypeptide. [ABSTRACT FROM AUTHOR]

The defluoroborylation of fluoroarenes by chromium-catalyzed cleavage of unactivated C–F bonds is described. The reaction uses HBpin as the boron source, low-cost and commercially available chromium salt as the precatalyst, and terpyridine as a crucial ligand, providing a protocol with atom-efficient benefits and a wide range of applicable substrates for the functionalization of aryl C–F bonds. Preliminary mechanistic studies indicate that an unprecedented Cr-catalyzed magnesiation of the unactivated C–F bond occurred. The generated arylmagnesium intermediates then participated in the subsequent borylation reaction. The application of the strategy in the preparation of valuable derivatives is demonstrated by the late-stage functionalization of boronate ester groups. [ABSTRACT FROM AUTHOR]

The reactivity of thioredoxin (Trx1) with the Au(I) drug auranofin (AF) and two therapeutic N-heterocyclic carbene (NHC)2-Au(I) complexes (bis [1-methyl-3-acridineimidazolin-2-ylidene]gold(I) tetrafluoroborate (Au3BC) and [1,3-diethyl-4,5-bis(4methoxyphenyl)imidazol-2-ylidene]gold(I) (Au4BC)) was investigated. Direct infusion (DI) electrospray ionization (ESI) mass spectrometry (MS) allowed information on the structure, stoichiometry, and kinetics of formation of Trx-Au adducts. The fragmentation of the formed adducts in the gas phase gave insights into the exact Au binding site within the protein, demonstrating the preference for Trx1 Cys32 or Cys35 of AF or the (NHC)2-Au(I) complex Au3BC, respectively. Reversed-phase HPLC suffered from the difficulty of elution of gold compounds, did not preserve the formed metal-protein adducts, and favored the loss of ligands (phosphine or NHC) from Au(I). These limitations were eliminated by capillary electrophoresis (CE) which enabled the separation of the gold compounds, Trx1, and the formed adducts. The ICP-MS/MS detection allowed the simultaneous quantitative monitoring of the gold and sulfur isotopes and the determination of the metallation extent of the protein. The hyphenation of the mentioned techniques was used for the analysis of Trx1-Au adducts for the first time. [ABSTRACT FROM AUTHOR]

Metallodrugs are an important group of medicinal agents used for the treatment of various diseases ranging from cancers to viral, bacterial, and parasitic diseases. Their distinctive features include the availability of a metal centre, redox activity, as well as the ability to multitarget. Diruthenium paddlewheel complexes are an intensely developing group of metal scaffolds, which can securely coordinate bidentate xenobiotics and transport them to target tissues, releasing them by means of substitution reactions with biomolecular nucleophiles. It is of the utmost importance to gain a complete comprehension of which chemical reactions happen with them in physiological milieu to design novel drugs based on these bimetallic scaffolds. This review presents the data obtained in experiments and calculations, which clarify the chemistry these complexes undergo once administered in the proteic environment. This study demonstrates how diruthenium paddlewheel complexes may indeed embody a new paradigm in the design of metal-based drugs of dual-action by presenting and discussing the protein metalation by these complexes. [ABSTRACT FROM AUTHOR]

A series of 5-alkoxy-1,3-benzenedicarbaldehydes and related dimers were prepared in three steps from dimethyl 5-hydroxyisophthalate. Acid catalyzed condensation of the dialdehydes with a tripyrrane dicarboxylic acid, followed by oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, afforded good yields of 3-alkoxybenziporphyrins, although dimeric tetraaldehydes failed to give isolatable porphyrinoid products. Proton NMR spectroscopy gave no indication of an aromatic ring current, but addition of trifluoroacetic acid resulted in the formation of dications that exhibited weakly diatropic characteristics. Spectroscopic titration with TFA demonstrated that stepwise protonation took place, generating monocationic and dicationic species. 3-Alkoxybenziporphyrins reacted with nickel(II) or palladium(II) acetate to give the related nickel(II) or palladium(II) complexes. These stable organometallic derivatives showed increased diatropic properties that were most pronounced for the palladium(II) complexes. These unique porphyrinoids provide further insights into the properties of benziporphyrins. [ABSTRACT FROM AUTHOR]

This paper presents methods for the introduction and exchange of substituents in a nucleobase and its nucleosides and nucleotides with emphasis on the C8-position in the purine skeleton. The nucleobase is open for electrophilic and nucleophilic chemistry. The nucleophilic chemistry consists mainly of displacement reactions when the C8-substituent is a good leaving group such as a halogen atom. The heteroatom in amines, sulfides, or oxides is a good nucleophile. Halides are good reaction partners. Metal-promoted cross-coupling reactions are important for carbylations. Direct oxidative metalation reactions using sterically hindered metal amides offer chemo- and regio-selectivity besides functional tolerance and simplicity. The carbon site is highly nucleophilic after metalation and adds electrophiles resulting in chemical bond formation. Conditions for metal-assisted reactions are described for nucleobases and their glycosides. [ABSTRACT FROM AUTHOR]

We report the synergistic combination of Pd(OAc)2 and Ag2O for the oxidative C−H arylation of (poly)fluoroarenes with aryl pinacol boronates (Ar‐Bpin) in DMF as the solvent. This procedure can be conducted easily in air, and without using additional ligands, to afford the fluorinated unsymmetrical biaryl products in up to 98 % yield. Experimental studies suggest that the formation of [PdL2(C6F5)2] in DMF as coordinating solvent does not take place under the reaction conditions as it is stable to reductive elimination and thus would deactivate the catalyst. Thus, the intermediate [Pd(DMF)2(ArF)(Ar)] must be formed selectively to give desired arylation products. DFT calculations predict a low barrier (5.87 kcal/mol) for the concerted metalation deprotonation (CMD) process between C6F5H and the Pd(II) species formed after transmetalation between the Pd(II)X2 complex and aryl‐Bpin which forms a Pd‐Arrich species. Thus a Pd(Arrich)(Arpoor) complex is generated selectively which undergoes reductive elimination to generate the unsymmetrical biaryl product. [ABSTRACT FROM AUTHOR]

The application of Mg[Ph4Pn] and Li·K[Ph4Pn] in transmetalation reactions to a range of Rh(I) precursors led to the formation of "half-baguette" anti-[Rh I(L) n ]2[μ:η5:η5Ph4Pn] (L = 1,5-cyclooctadiene, norbornadiene, ethylene; n = 1, 2) and syn-[Rh I(CO)2]2[μ:η5:η5Ph4Pn] complexes as well as the related iridium complex anti-[Ir I(COD)]2[μ:η5:η5Ph4Pn]. With CO exclusive syn metalation was obtained even when using mono-nuclear Rh(I) precursors, indicating an electronic preference for syn metalation. DFT analysis showed this to be the result of π overlap between the adjacent M(CO)2 units which overcompensates for dz2 repulsion of the metals, an effect which can be overridden by steric clash of the auxiliary ligands to yield anti-configuration as seen in the larger olefin complexes. syn-[Rh I(CO)2]2[μ:η5:η5Ph4Pn] is a rare example of a twinned organometallic where the two metals are held flexibly in close proximity, but the two d8 Rh(I) centres did not show signs of M–M bonding interactions or exhibit Lewis basic behaviour as in some related mono-nuclear Cp complexes due to the acceptor properties of the ligands. The ligand substitution chemistry of syn-[Rh I(CO)2]2[μ:η5:η5Ph4Pn] was investigated with a series of electronically and sterically diverse donor ligands (P(OPh)3, P(OMe)3, PPh3, PMe3, dppe) yielding new mono- and bis-substituted complexes, with E-syn-[Rh I(CO)(P{OR})3]2[μ:η5:η5Ph4Pn] (R = Me, Ph) characterised by XRD. [ABSTRACT FROM AUTHOR]

Quinoline carboxylic acid-linked and Pd nanoparticle (NP)-loaded COF nanospheres were constructed via a three-component one-pot Doebner reaction and post-synthetic metalation. The obtained Pd@DhaTAPB-COOH solid stabilizer can greatly promote the pH-switched recyclable Pickering interfacial dechlorination reaction, which sheds light on the bright future of smart Pickering emulsion catalysis. [ABSTRACT FROM AUTHOR]

The reactions of dimesitylphosphane oxide Mes2P(O)H with Lawessons reagent and dimesitylphoshane with selenium yield Mes2P(E)H with E = S (1a) and E = Se (1b), respectively, with moderate yields. Metalation of dimesitylphosphane sulfide 1a with n-butyllithium, sodium hydride or potassium hydride in THF allows the isolation of dinuclear dimesityl-thiophosphinites of the type [(thf)2A-S-PMes2]2 [A = Li (4), Na (5), K (2a)] with central four-membered A2S2 rings. The weaker base THP leads to the very similar aggregate [(thp)2K-S-PMes2]2 (3a) as has also been observed for the homologous potassium dimesityl-selenophosphinites of the type [(L)2K-Se-PMes2]2 [L = thf (2b), thp (3b)]. Addition of 18-crown-6 ether leads to deaggregation and expectedly to formation of mononuclear [(18C6)K-S-PMes2] (6). Moderate yields have been obtained due to dismutation reactions that yield the corresponding phosphinates AE2PMes2 and phosphanides APMes2, a degradation process which has been observed earlier also for Li-O-PMes2. This side reaction hampers the application of these thio- and selenophosphinites as catalysts in the addition of phosphane sulfides and selenides across alkynes. [ABSTRACT FROM AUTHOR]

The reactions of dimesitylphosphane oxide Mes2P(O)H with Lawessons reagent and dimesitylphoshane with selenium yield Mes2P(E)H with E = S (1a) and E = Se (1b), respectively, with moderate yields. Metalation of dimesitylphosphane sulfide 1a with n-butyllithium, sodium hydride or potassium hydride in THF allows the isolation of dinuclear dimesityl-thiophosphinites of the type [(thf)2A-S-PMes2]2 [A = Li (4), Na (5), K (2a)] with central four-membered A2S2 rings. The weaker base THP leads to the very similar aggregate [(thp)2K-S-PMes2]2 (3a) as has also been observed for the homologous potassium dimesityl-selenophosphinites of the type [(L)2K-Se-PMes2]2 [L = thf (2b), thp (3b)]. Addition of 18-crown-6 ether leads to deaggregation and expectedly to formation of mononuclear [(18C6)K-S-PMes2] (6). Moderate yields have been obtained due to dismutation reactions that yield the corresponding phosphinates AE2PMes2 and phosphanides APMes2, a degradation process which has been observed earlier also for Li-O-PMes2. This side reaction hampers the application of these thio- and selenophosphinites as catalysts in the addition of phosphane sulfides and selenides across alkynes. [ABSTRACT FROM AUTHOR]

Converting carbon dioxide (CO2) into valuable chemicals such as fossil resources via photocatalysis requires the development of advanced materials. Herein, we coupled zirconium-based metal–organic frameworks (MOFs) containing porphyrin and Cu-porphyrin with anatase TiO2. The effect of the porphyrin metalation proportion was also investigated. Notably, while the use of free-base porphyrin as the organic linker resulted in the development of PCN-224, the presence of Cu-porphyrin provided mixed-phase MOF structures containing both PCN-224 and PCN-222. MOF/TiO2 composites bearing partial (50%) metalated porphyrin were proven more active and selective towards the production of CH4, at ambient conditions, in the gas phase and using water vapors without the use of hole scavengers. The optimized composite bearing 15 wt.% of the partial metalated MOF was three times more active than pure TiO2 towards CH4 production. This study provides insights on the effect of precise materials engineering at a molecular level on the development of advanced MOF-based photocatalysts for CO2 reduction. [ABSTRACT FROM AUTHOR]

This article discusses the development of a catalytic method for the magnesiation of alkyl fluorides using magnesium powder. Alkylmagnesium reagents, such as Grignard reagents, are important tools in organic synthesis, but the preparation of alkylmagnesium reagents from alkyl fluorides has been challenging due to the high bond-dissociation energy of C-F bonds. The researchers used a bimetallic rhodium-aluminum complex as a catalyst to activate the C-F bond and successfully magnesiate alkyl fluorides, including secondary and tertiary ones. The method offers a new approach for the synthesis of alkylmagnesium reagents and expands the range of available starting materials. [Extracted from the article]

In main group chemistry, the BDI ligand ([HC(C(Me)N(R))2]), more commonly known as NacNac, has proved indispensable over the last two decades. Within this work, we are introducing the hybrid NacNac‐akin ligand 3,3‐dimethyl‐2‐[2‐methyl‐2‐(2,6‐diisopropyl‐aniline)ethenyl]‐3H‐indolenine (DNI). On the basis of this novel ligand, alkali metal complexes [DNI(M1)] [M1=Li (3(OEt2)), Na (4(THF)3), and K (5(THF)3)] have been synthesized by facile deprotonation of the ligand's backbone. The reaction of DNI with AlH3 ⋅ NMe2Et led to the aluminium dihydride compound [DNI‐AlH2] (6) in excellent yield (90 %). Further synthesis of [DNI‐AlI2] (7), which is seen as a potential precursor for the aluminium(I) complex, was realized in the presence of 1.0 equiv. iodine with 6. All products 2–7 were completely characterized by 2D‐NMR, mass spectrometry, elemental analysis and SC‐XRD. Density functional theory calculations were performed to provide better understanding of their bonding characteristics and electronic structures. [ABSTRACT FROM AUTHOR]

Advancing the use of alkali‐metal alkoxides as additives to activate organometallic reagents, here we report the synthesis and characterization of a novel potassium zincate [{(PMDETA)KZn(OtBu)Et2}2] obtained by co‐complexation of equimolar amounts of potassium tert‐butoxide, diethyl zinc and the tridentate donor PMDETA (N,N,N',N",N"‐pentamethyldiethylenetriamine). Demonstrating its ability to activate both of the Et groups towards alkyne C−H metalation, this zincate reacts at room temperature with 2 equivalents of phenylacetylene to furnish [(THF)2KZn(CCPh)2(OtBu)}2], whereas, for the homometallic [ZnEt2(TMEDA)] (TMEDA=N,N,N',N'‐tetramethylethylendiamine) only one Et group is reactive towards the same substrate under the same conditions. Investigations on the reactivity of these complexes to undergo N−H amine metalation using 2, 6‐diisopropylphenylamine (NH2Dipp) and 1,2,3,4‐tetrahydroquinoline (THQ(H)) as model substrates revealed that while homometallic [ZnEt2(TMEDA)] is completely inert towards these amines, heterobimetallic [{(PMDETA)KZn(OtBu)Et2}2] reacts through one of its Et groups to form [(THF)2KZn(OtBu)(Et)(NHDipp)] as well as [(THF)4K2Zn(THQ)4]. The latter is obtained as a side product of ligand redistribution of a putative [(THF)nKZn(OtBu)(Et)(THQ)] intermediate. An alternative method to access mixed amide/alkoxide potassium zincates is also described by assessing the co‐complexation of KOtBu with Zn(HMDS)2 in the presence of PMDETA which gave [(PMDETA)KZn(HMDS)2(OtBu)]. [ABSTRACT FROM AUTHOR]

Many efforts have been made in the last few decades to selectively transport antitumor agents to their potential target sites with the aim to improve efficacy and selectivity. Indeed, this aspect could greatly improve the beneficial effects of a specific anticancer agent especially in the case of orphan tumors like the triple negative breast cancer. A possible strategy relies on utilizing a protective leaving group like alizarin as the Pt(II) ligand to reduce the deactivation processes of the pharmacophore enacted by Pt resistant cancer cells. In this study a new series of neutral mixed-ligand Pt(II) complexes bearing alizarin and a variety of diamine ligands were synthesized and spectroscopically characterized by FT-IR, NMR and UV–Vis analyses. Three Pt(II) compounds, i.e., 2b, 6b and 7b, emerging as different both in terms of structural properties and cytotoxic effects (not effective, 10.49 ± 1.21 μM and 24.5 ± 1.5 μM, respectively), were chosen for a deeper investigation of the ability of alizarin to work as a selective carrier. The study comprises the in vitro cytotoxicity evaluation against triple negative breast cancer cell lines and ESI-MS interaction studies relative to the reaction of the selected Pt(II) complexes with model proteins and DNA fragments, mimicking potential biological targets. The results allow us to suggest the use of complex 6b as a prospective anticancer agent worthy of further investigations. [ABSTRACT FROM AUTHOR]

Cyclic azobenzene‐BODIPY hybrids were synthesized via cyclization by 1) acid‐catalysed condensation of azobenzene‐bridged dipyrroles with 3,5‐di‐tert‐butylbenzaldehyde, 2) oxidation with DDQ, and 3) metalation with BF3 ⋅ Et2O. The structures of many cyclic hybrids have been confirmed by single crystal X‐ray analysis. The absorption spectra of the hybrids reveal the effective cyclic conjugation. The ultrafast measurements reveal that the photoexcited decays of these cyclic hybrids depend upon the ring size and connectivity. [ABSTRACT FROM AUTHOR]

With their highly reactive respective C−Na and N−Na bonds, organosodium and sodium amide reagents could be viewed as obvious replacements or even superior reagents to the popular, widely utilised organolithiums. However, they have seen very limited applications in synthesis due mainly to poor solubility in common solvents and their limited stability. That notwithstanding in recent years there has been a surge of interest in bringing these sustainable metal reagents into the forefront of organometallics in synthesis. Showcasing the growth in utilisation of organosodium complexes within several areas of synthetic chemistry, this Minireview discusses promising new methods that have been recently reported with the goal of taming these powerful reagents. Special emphasis is placed on coordination and aggregation effects in these reagents which can impart profound changes in their solubility and reactivity. Differences in observed reactivity between more nucleophilic aryl and alkyl sodium reagents and the less nucleophilic but highly basic sodium amides are discussed along with current mechanistic understanding of their reactivities. Overall, this review aims to inspire growth in this exciting field of research to allow for the integration of organosodium complexes within common important synthetic transformations. [ABSTRACT FROM AUTHOR]

Similar to porphyrin, porphyrinogen is regarded as a stable platform with adaptable properties. Herein we demonstrate the synthesis of metal complexes by direct incorporation of transition metals having importance on the redox activity of the ligands. Metal ions were directly incorporated by using anhydrous metal salts like CoII and CrIII in porphyrinogen core. Tetra-anion is generated by the reaction of n-BuLi and then followed by metal complex formation. Its oxidation unlike the aromatization of the porphyrin skeleton gives rise to various forms of oxidized porphyrinogen. The above aspects are particularly important for establishing metal-assisted redox chemistry of porphyrinogen ligand. The β-position of the pyrrole ring in porphyrinogens was suitably substituted by halogens and other functionalities (β-substituted porphyrinogen) which were found to be effective receptors for a wide variety of guest molecules under certain conditions. The invention, which falls under the technical heading of "organic compound synthesis," details a novel porphyrin family chemical as well as its preparation and application, involving several steps in the preparation process. Cycloheptanone and pyrroles are initially combined in an acetone environment to create meso-cycloheptyl porphyrinogen, which is subsequently followed by metal porphyrinogens and β-substituted porphyrinogen. By using FT-IR, 1H-NMR, mass, and UV–Vis spectroscopy, the characterization was completed. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) capable of post-synthetic metalation (PSMet) have garnered significant interest as supports for catalytic metals. The Mn-based MOF, MnMOF-1 ([Mn3(L2Me)3] where L2Me = bis-(4-carboxyphenyl-3,5-dimethylpyrazolyl)methane), has been an exemplar for studying PSMet. Herein we investigate the synthesis of Mn-based MOFs from related flexible ditopic pyrazole carboxylate links, along with the formation of MOFs with similar tetratopic hinged linkers. We show for the first time that MnMOF-1 is likely a kinetic or metastable phase and a newly identified 2D layered material (MnMOF-2D) is the thermodynamically favoured product for this metal–linker combination. Formation of a MnMOF-1 structure with shorter linkers is thwarted by steric clashes that preclude the formation of the Mn3 cluster. This observation prompted the use of density functional theory (DFT) simulations that showed the target material to be very dense, highly strained and thereby energetically unfavourable, but potentially, a hypothetical MnMOF-1 structure with a longer phenylethynyl spacer would be energetically feasible. Finally, the predominance of 2D MOFs formed with shorter flexible links encouraged us to use tetratopic hinged linkers to form 3D frameworks, which was vindicated by the successful synthesis of two new porous 3D Mn-based MOFs, MnMOF-L4 and MnMOF-L5. These results highlight that reticular synthesis of MOFs formed with flexible, non-linear linkers is challenging. [ABSTRACT FROM AUTHOR]

Metal‐organic frameworks (MOFs) provide uniquely tunable, periodic platforms for site‐isolation of reactive low‐valent metal complexes of relevance in modern catalysis, adsorptive applications, and fundamental structural studies. Strategies for integrating such species in MOFs include post‐synthetic metalation, encapsulation and direct synthesis using low‐valent organometallic complexes as building blocks. These approaches have each proven effective in enhancing catalytic activity, modulating product distributions (i.e. by improving catalytic selectivity), and providing valuable mechanistic insights. In this minireview, we explore these different strategies, as applied to isolate low‐valent species within MOFs, with a particular focus on examples that leverage the unique crystallinity, permanent porosity and chemical mutability of MOFs to achieve deep structural insights that lead to new paradigms in the field of hybrid catalysis. [ABSTRACT FROM AUTHOR]

This document is a research article that focuses on the total synthesis of ajudazol A, a natural product. The authors, researchers from the University of Bonn, provide detailed information about the experimental procedures and characterization data. The document is technical in nature and provides information relevant to organic chemistry and natural product synthesis. [Extracted from the article]

Aryl azoles can be found in numerous active pharmaceutical ingredients (APIs). Milvexian is a Factor Xia inhibitor currently in phase III for the treatment of thrombotic events containing an ortho-substituted 1-aryl-1H-1,2,3-triazole moiety. During the process development of Milvexian, we assessed multiple approaches for the preparation of 4-chloro-1,2,3-triazole, intermediate 1. In this review article, we will detail how we initiated several academic collaborations to speed up the selection of the best synthesis for commercial manufacturing. Ultimately, those results not only helped us to achieve our goal but yielded general methodologies for the functionalization of azoles that extended even beyond our initial scope.

The bis(azolium) salt [L1‐H2]Br2 was found to serve as a suitable platform for accessing the heterobimetallic IrIII‐M (M=PdII/AuI) and PdII‐IrIII complexes. Initially, selective mono‐metalation of [L1‐H2]Br2 yielded an orthometalated IrIII‐ or non‐orthometalated PdII‐complex. Sequential metalation of the mono‐IrIII complex resulted in the formation of heterobimetallic IrIII‐PdII/AuI complexes. Similarly, a distinct heterobimetallic PdII‐IrIII complex was synthesized starting from the mono‐PdII complex. Further, the corresponding homobimetallic IrIII‐IrIII and PdII‐PdII complexes were directly obtained from [L1‐H2]Br2. Additionally, monometallic PdII and IrIII analogues were synthesized from [L2‐H]Br and [L3‐H]Br, respectively. The heterobimetallic IrIII‐PdII and PdII‐IrIII complexes were then evaluated as catalysts in various one‐pot tandem catalytic reactions in which they demonstrated superior activity than the mixtures of both their corresponding homobimetallic IrIII‐IrIII/PdII‐PdII and monometallic IrIII/PdII counterparts, under the constant concentrations of metal centers. Moreover, while comparing complexes IrIII‐PdII and PdII‐IrIII, the former exhibits higher activity in all the studied reactions. All these findings suggest the presence of some form of cooperativity between the two metal centers (Ir and Pd) connected by a single ligand framework in IrIII‐PdII and PdII‐IrIII complex, with IrIII‐PdII displaying better cooperativity that has been validated by electrochemical, NMR, and DFT studies. [ABSTRACT FROM AUTHOR]

Metalation of functionalized benzoquinoline-linked COFs via post-synthetic modification can be applied into electrocatalytic oxygen reduction and lithium-sulfur batteries. [Display omitted] It is worthwhile to explore and develop multifunctional composites with unique advantages for energy conversion and utilization. Post-synthetic modification (PSM) strategies can endow novel properties to already excellent covalent organic frameworks (COFs). In this study, we prepared a range of COF-based composites via a multi-step PSM strategy. COF-Ph-OH was acquired by demethylation between anhydrous BBr 3 and − OMe, and then, M@COF-Ph-OH was further obtained by forming the N − M − O structure. COF-Ph-OH exhibited a 2e−-dominated oxygen reduction reaction (ORR) pathway with high H 2 O 2 selectivity, while M@COF-Ph-OH exhibited a 4e−-dominated ORR pathway with low H 2 O 2 selectivity, which was due to the introduction of a metal salt with a d electron structure that facilitated the acquisition of electrons and changed the adsorption energy of the reaction intermediate (*OOH). It was proven that the d electron structure was effective at regulating the reaction pathway of the electrocatalytic ORR. Moreover, Co@COF-Ph-OH showed better 4e− ORR properties than Fe@COF-Ph-OH and Ni@COF-Ph-OH. In addition, compared with the other sulfur-impregnated COF-based composites examined in this study, S-Co@COF-Ph-OH had a larger initial capacity, a weaker impedance, and a stronger cycling durability in Li-S batteries, which was attributed to the unique porous structure ensuring high sulfur utilization, the loaded cobalt accelerating LiPS electrostatic adsorption and promoting LiPS catalytic conversion, and the benzoquinoline ring structure being ultra-stable. This work offers not only a rational and feasible strategy for the synthesis of multifunctional COF-based composites, but also promotes their application in electrochemistry. [ABSTRACT FROM AUTHOR]

Herein we disclose an efficient one‐pot route to a wide range of 3‐substituted fused pyridinyl‐lactones, so called aza‐phthalides. The developed strategy involves a Metal/Halogen Exchange (MHE) reaction as key step, followed by an electrophile trapping using various carbonyl derivatives and a subsequent lactonization. To promote the MHE reaction with high chemoselectivity, our investigations have particularly focused on the nature of mono‐ or bimetallic derivatives as metalation reagents including organolithiums, Grignard reagents and lithium organomagnesiate complexes, and highlighted the positive salt effect on reactional sequence. An extension to fused heteroaryl‐lactones (benzothienyl‐, benzofuranyl‐ and naphthofuranyl scaffolds) was explored. [ABSTRACT FROM AUTHOR]