Search

The crystal structure of hexa-μ-hydroxo-do­deca­methylocta-μ3-oxo-do­deca­gallium(III) bis­[tetra­kis­(penta­fluoro­phenyl)­borate(III)] chloro­benzene disolvate dihydrate, [Ga12(CH3)12(μ3-O)8(μ-OH)6](C24F20B)2·2C6H5Cl·2H2O, is reported. The gallium-oxo-hydroxide dication is located on an inversion center and adopts a cage structure composed of 12 fused Ga3O3 rings and is associated with the hydrate mol­ecules and the [B(C6F5)4]− anions through hydrogen bonds and one O-H⃛π-ring interaction. Disordered chloro­benzene solvent mol­ecules are also present in the crystal structure. [ABSTRACT FROM AUTHOR]

An abstract of the article "Pestaloporonins A-C (I)-(III): Caryophyllene-Derived Sesquiterpenoids from a Fungicolous Isolate of Pestalotiopsis sp.," by I. H. Hwang and colleagues is presented.

The title triene, C18H10F6, was prepared via the Pd0 coupling reaction of ( E)-(1,2-di­fluoro-1,2-ethenediyl)­bis­(tri­butyl­stan­nane) with ( Z)-β-iodo-α,β-di­fluoro­styrene in N, N′-dimethylformamide/tetrahydrofuran. The crystal structure shows the product to be the 1 E,3 E,5 E isomer. Due to steric interactions between F atoms, the double bonds are not coplanar. The planes defined by the two terminal double bonds are almost perpendicular. [ABSTRACT FROM AUTHOR]

()-Tartaric acid, C4H6O6, crystallized from ethanol in space group P. The structure is characterized by five hydrogen bonds, including the formation of a centrosymmetric carbox­ylic acid dimer which forms infinite chains along the body diagonal. These chains form sheets via hydrogen bonding between α-hydroxyl groups. The sheets are connected through a bifurcated hydrogen bond. Structural comparisons are made with homochiral (2 R,3 R)-(+)-tartaric acid. [ABSTRACT FROM AUTHOR]

The title compound, [Hf(C7H7)3(C10H15)], adopts a monomeric three-legged piano-stool structure. One benzyl ligand is disordered between two sites (44:56%) related by a ∼30° rotation about an axis defined by the Hf atom and the ipso-C atom of the benzyl ligand. [ABSTRACT FROM AUTHOR]

Four meroterpenoids [talarolutins A–D] and one known compound [purpurquinone A] were characterized from an endophytic fungal isolate of Talaromyces minioluteus (G413), which was obtained from the leaves of the medicinal plant milk thistle [ Silybum marianum (L.) Gaertn. (Asteraceae)]. The structures of talarolutins A–D were determined by the analysis of various NMR and MS techniques. The relative and absolute configuration of talarolutin A was determined by X-ray diffraction analysis. A combination of NOESY data and comparisons of ECD spectra were employed to assign the relative and absolute configuration of the other analogs. Talarolutins B–D were tested for cytotoxicity against human prostate carcinoma (PC-3) cell line, antimicrobial activity, and induction of quinone reductase; no notable bioactivity was observed in any assay. [ABSTRACT FROM AUTHOR]

The high fluorophilicity of borane-containing ligands offers promise for accessing new metallodrug candidates capable of bifunctional [18F]-positron emission tomography (PET) imaging, but this requires water soluble and hydrolytically stable ligands that can be fluorinated under mild conditions. Toward this goal, here we report the synthesis and characterization of water-soluble Pt(II) complexes containing a triaminoborane-bridged diphosphoramidite ligand called MeOTBDPhos that can be fluorinated using simple fluoride salts. NMR and XRD studies show that (MeOTBDPhos)PtCl2 (1) dissolves in water with cooperative H–OH addition across the bridgehead N–B bond to form 1-H2O. The B–OH bond in 1-H2O undergoes rapid displacement with fluoride (<10 min) when treated with CsF in MeCN to form 1-HF. 1-HF can also be prepared in <10 min by addition of KF to 1 in the presence Kryptofix® 222 and (HNEt3)Cl in MeCN. In addition to using fluoride salts, we show how mononuclear 1 can be fluorinated with HBF4·Et2O to form dinuclear [(MeOTBDPhos-HF)Pt(μ-Cl)]2(BF4)2 (4-HF). Comparative studies show that the B–F bond in 1-HF undergoes hydrolysis as soon as it is dissolved in water or saline, but the B–F bond persists for hours when the pH of the solution is lowered to pH ≤ 2. In contrast to 1-HF, the B–F bond in dinuclear 4-HF persists for days when dissolved in water, which may be attributed to slow, sacrificial release of fluoride from the BF4− anion. The results show how cooperative N–B reactivity on the ligand can be leveraged to rapidly fluorinate water-soluble MeOTBDPhos complexes under mild conditions and afford suggestions for how to enhance hydrolytic B–F stability, as required for use in biomedical applications. [ABSTRACT FROM AUTHOR]

Abstract: Two tetraarylethylene derivatives symmetrically functionalized at the 4, 4′, 4″, and positions with either 4-pyridyl or 3-pyridyl groups were converted to their corresponding tetrapyridinium perchlorate salts upon exposure to Fe(ClO4)3·xH2O. These tetra-perchlorates were isolated as single crystals and their structures were determined by X-ray diffractometry. In both cases extensive hydrogen bonding networks were observed involving pyridinium N–H groups, perchlorate anions, and included water molecules. Additionally, both structures feature hydrophobic crystalline regions formed from stacking of tetraarylethylene cations in helical fashion. Polar pyridinium N–H groups are directed outward from these stacks into hydrophilic crystalline regions containing perchlorate anions and water molecules of hydration. Information obtained regarding the solid state structures of these functionalized tetraarylethylene derivatives should prove useful in design of more elaborate supramolecular architectures. [Copyright &y& Elsevier]

Solid-state reduction of WCl with Hg followed by incomplete sublimation of mercury chlorides generated the tritungsten decachloride—mercury chloride adducts WCl(HgCl)(HgCl). Thermal equilibration of the solid-state products followed by sublimation of HgCl afforded single crystals that include the mercurous chloride adduct WCl(HgCl). Single-crystal diffractometry revealed a one-dimensional polymer of tritungsten decachloride triangular clusters with novel terminal and inter-cluster-bridging ClHgHgCl ligands. The W cluster core has similar metrics to that of the benzyltriethylammonium salt of W(μ-Cl)(μ-Cl)Cl. WCl(HgCl) is the first reported adduct of the binary tungsten chloride WCl. The ClHgHgCl ligands are more labile that the terminal chlorine atoms of W(μ-Cl)(μ-Cl)Cl. These results demonstrate diverse roles and potential utility of main group element halide by-product ligands in solid-state reductions of transition metal halides. [ABSTRACT FROM AUTHOR]

Abstract: The cis-fused hexahydroxanthene system can be obtained through a cascade cyclization initiated by Lewis acid-mediated epoxide opening and terminated by reaction with a MOM-protected phenol. Only a single diastereomer of the product was obtained with stereochemistry verified by diffraction analysis. This demonstrates the viability of this approach to natural products containing the cis-fused hexahydroxanthene skeleton, and supports preparation of more complex targets through a similar strategy. [Copyright &y& Elsevier]

Abstract: The organoditantalum complexes (η-C5Me5)2Ta2(μ-X)4 (X=Cl, Br) react with 1–5 equiv. of allene under mild conditions to afford the fluxional allene adducts (C5Me5)2Ta2(μ-η1,η3-C3H4)(μ-X)X3 as shown by spectroscopic and spectrometric data. Low-temperature-limit proton NMR data at −95 °C for (C5Me5)2Ta2(μ-η1,η3-C3H4)(μ-Cl)Cl3 show a large chemical shift range for the inequivalent allene hydrogens, with a high-field value for one hydrogen at δ −0.36, and inequivalent Cp* groups. The low-temperature-limit 13C NMR resonances for the allene ligand are found at δ 204.4 (central C), δ 70.3 (CH2, 1 J CH =154 Hz), and the substantially upfield value of δ 42.9. The latter resonance has remarkably different coupling constants (1 J CH =173, 154 Hz). The allene coordinates in a novel alkylidene-diyl fashion in the solid-state, as shown by X-ray diffractometry on (C5Me5)2Ta2(μ-η1,η3-C3H4)(μ-Cl)Cl3 at 200 K. One tantalum is doubly-bonded to the central allenic carbon (Ta1nce, 2.011(7) Å) and interacts with an allene hydrogen in a probable β-agostic manner (Ta1–H21A distance of 2.25(10) Å). The second tantalum is coordinated to the allene in a hybrid of η3-allylic and sigma bonding, with Ta2–C distances to the allene methylenes of 2.206(8) and 2.276(9) Å and a Ta2–C22 bond distance to the central allenic carbon of 2.253(7) Å. The allene hydrogens are oriented above and below the C–C–C plane, consistent with appreciable σ-bonding between the Ta(2) and the allene methylenes. The bent allene ligand has a C–C–C angle of 106.0(6)° and can be viewed as reduced by four electrons, with concomitant oxidation of the two d2 tantalum centers of the organoditantalum(III) reactant. The long Ta⋯Ta nonbonded distance of 3.3052(8) Å is consistent with two d0 tantalum centers in an organoditantalum(V) product. [Copyright &y& Elsevier]

The terminal (diphenylalkenyl)alkylidene complexes (C5Me4R)Ta(CHCHCPh2)X2 (R=Me, Et; X=Cl, Br) are formed in moderate yields from the ring-opening reaction of 3,3-diphenylcyclopropene with the organoditantalum(III) halides (η-C5Me4R)2Ta2(μ-X)4. Potassium amalgam reduction of these alkenylalkylidene complexes afforded the alkylidene-tethered tantallanorbornadienes (C5Me4R)Ta[CHCHCPh(σ2-C6H5)], which possess a bent, boat conformation σ2-arene ligand with a fold angle of 19.24(46)° (R=Me) in the solid state. 13C and 1H NMR spectroscopies are consistent with a rapid flip-flop motion that averages the resonances of the σ2-phenyl group to fewer resonances than expected from the solid-state structure. [Copyright &y& Elsevier]

A saturated dicarboxylic acid is employed to achieve a photoreactive hydrogen-bonded assembly based on a thiophene that reacts to generate a head-to-tail photoproduct. A co-crystal that exhibits both a homo- and heterosynthon in the same co-crystal based on adipic acid and the thiophene is also presented. [ABSTRACT FROM AUTHOR]

Soft porous nanocrystals with a pronounced shape-memory effect exhibit two- to three-fold increase in elastic modulus compared to the microcrystalline counterpart as determined by atomic force microscopy nanoindentation. The increase in rigidity is consistent with the known shape-memory effect displayed by the framework solid at the nanoscale. Crystal downsizing can offer new avenues for tailoring the mechanical properties of metal–organic frameworks. [ABSTRACT FROM AUTHOR]

A structural study of two-dimensional inverted metal–organic frameworks demonstrates that the interior cavities of the framework structures can be systematically modified by changing the organic anion of a Cu(II)-paddlewheel unit. Changing the anion allows modifications to the shapes and sizes of the cavities in a series of isoreticular frameworks. The construction of the frameworks is based on the application of a tetrafunctional organic cyclobutane ligand synthesized in the organic solid state. [ABSTRACT FROM AUTHOR]

The acoustic frequency distributions, mechanical moduli, and crystal structures for theophylline (THY) and three cocrystals are combined to illustrate how supramolecular organization and interaction topology contribute to the compaction performance of molecular solids. A novel solid form of THY, a cocrystal with 4-fluoro-3-nitrobenzoic acid (FNBA), is reported. This material adopts a 2d-layered structure and has superior tabletability relative to THY. The improved plasticity for THY-FNBA was further corroborated by Heckel analysis with THY-FNBA displaying a reduced yield pressure (Py) relative to theophylline. The performance of THY-FNBA was further compared to a structurally similar theophylline cocrystal with acetaminophen (THY-APAP). Despite structural similarity, their relative compaction performance was distinct. Powder Brillouin light scattering (p-BLS) was used as an experimental measure of the interaction topologies of these materials, and through this approach, the interlayer interaction strength is shown to be weaker relative to THY-APAP. Moreover, a THY and p-aminobenzoic acid (PABA) cocrystal was studied to contrast the performance of two columnar crystal structures, THY-PABA and THY. THY-PABA displayed a stacking structure that frustrated slip and the compaction performance was consequently diminished. The elasticity moduli were further determined for all materials, and both THY-APAP and THY-FNBA displayed low Young's and shear moduli and is consistent with our compaction studies. [ABSTRACT FROM AUTHOR]

Co-crystallization of a symmetrical azo bipyridine with isosteric resorcinols affords isostructural co-crystals that exhibit linear thermal expansion along each axis. The thermal expansions involve interplay between intra-layer halogen and hydrogen bonds. [ABSTRACT FROM AUTHOR]

A correlation between Young's modulus, as determined by using nanoindentation atomic force microscopy (AFM), and atomic polarizability is observed for members of a series of cocrystals based on systematic changes to one cocrystal component. Time domain spectroscopy over terahertz frequencies (THz-TDS) is used for the first time to directly measure the polarizability of macro- and nanosized organic solids. Cocrystals of both macro- and nanodimensions with highly polarizable atoms result in softer solids and correspondingly higher polarizabilities. [ABSTRACT FROM AUTHOR]

Ag(I) is used to form a π-stacked metalorganic solid that exhibits remarkably high electrical conductivity. The solid undergoes a single-crystal-tosingle- crystal [2+2] photodimerization to generate a ID coordination polymer with over 40% higher conductivity. The Ag(l) complex represents the first example of an increase in conductivity resulting from a [2+2] photodimerization. Density of states calculations show a higher contribution from Ag(l) ions to the valence band in the photodimerized solid, supporting the increase in conductivity. [ABSTRACT FROM AUTHOR]

Abstract: We have prepared and characterized two ruthenium(II) complexes supported by phosphine-functionalized N-heterocyclic (NHC) ligands. One of the complexes (2a) underwent ortho-metalation of the N-phenyl moiety giving rise to a tridentate PCNHCC− coordinating ligand whereas 2b bears an N-mesityl group in order to prevent C–H activation of the aryl ring thereby enforcing a PCNHC bidentate binding mode. Both 2a and 2b were shown to catalyze transfer hydrogenation of ketones at 82°C in 2-propanol in the presence of KO t Bu albeit with vastly different catalytic activities. Catalytic transfer hydrogenation by 2b was shown to proceed at room temperature and in air using unpurified 2-propanol as solvent and hydrogen donor. Time studies revealed unique kinetic profiles for the two precatalysts; this may shed light on the difference in their catalytic activities. [Copyright &y& Elsevier]

Abstract: Two tetrapyridyl-substituted tetraphenylethylenes have been prepared via Suzuki coupling between tetrabromo tetraphenylethylene and 3- or 4-pyridine boronic acid. Both compounds exhibit aggregation-induced emission as determined by solid state fluorescence spectroscopy and solution phase fluorescence measurements performed in aqueous/organic solvent mixtures. Solution phase fluorescence was also found to be switchable as a function of pH. 3-Pyridyl-substituted tetraphenylethylene has been structurally characterized by X-ray crystallography. [Copyright &y& Elsevier]

Correction for 'Mechanical rigidity of a shape-memory metal–organic framework increases by crystal downsizing' by Al A. Tiba et al., Chem. Commun., 2021, 57, 89–92, DOI: 10.1039/D0CC05684G. [ABSTRACT FROM AUTHOR]

Zinc centers in pseudo-tetrahedral geometry are widely found in biology, often with three histidine ligands from protein. The trispyrazolylborate "scorpionate" ligand is used as a model for this tris(histidine) motif, and spectroscopically active CoII is often used as a substitute for spectroscopically silent ZnII. In this work, four pseudo-tetrahedral scorpionate complexes with the formula (Tp t -Bu,Tn)CoL, where Tp t -Bu,Tn = hydrotris(3- tert -butyl, 5–2′-thienyl-pyrazol-1-yl)borate anion and L = Cl−, N 3 −, NCO−, or NCS−, were studied using variable-temperature, variable-field magnetic circular dichroism (VTVH MCD) spectroscopy. The major goal was to determine the axial and rhombic zero field splitting (ZFS) parameters (D and E , respectively) of these S = 3/2 systems and compare these ZFS parameters to those determined previously by high-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy on the same (L = Cl− and NCS−) or closely related complexes. Additionally, HFEPR studies were undertaken here on the complexes with L = N 3 −, NCO−. Crystal structures for these two complexes are also first reported here. The values of D determined by VTVH MCD were + 12.8 and + 3.6 cm−1 for the L = Cl− and NCS- complexes, respectively. These values are in close agreement with those for the same complexes as previously determined by HFEPR. The values of D determined by VTVH MCD were + 3.0 and + 6.6 cm−1 for the L = N 3 − and NCO- complexes, respectively. These values were not as close to those determined by HFEPR in the present study, which are 4.2 cm−1 ≤ | D | ≤ 5.6 cm−1 in Tp t -Bu,TnCoN 3 , and 8.3 cm−1 ≤ | D | ≤ 11.0 cm−1 in Tp t -Bu,TnCoNCO. The bands in MCD spectra of these complexes were assigned in C 3 v symmetry and a complete ligand-field analysis of the MCD data was made using the Angular Overlap Model (AOM), which is compared to previous results. Magnetic circular dichroism was used to determine the zero field splitting parameter, D , in complexes of formula (Tp t -Bu,Tn)CoL, (Tp t -Bu,Tn = hydrotris(3- tert -butyl, 5–2′-thienyl-pyrazol-1-yl)borate anion; L = Cl−, N 3 −, NCO−, or NCS−). The values of D are in agreement with those determined by high-frequency and -field electron paramagnetic resonance. Unlabelled Image • Magnetic circular dichroism (MCD) can determine zero-field splitting (ZFS) in CoII. • High-frequency and -field EPR (HFEPR) values of ZFS in CoII are more precise. • MCD values of ZFS in CoII are still comparable to those determined by HFEPR. • MCD is more sensitive than HFEPR and can be applied to dilute biological CoII. [ABSTRACT FROM AUTHOR]

Focuses on the preparation and characterization of a propynylidene organodimetallic complex arising from double C-H activation of an allene ligand. Single-crystal diffractometry revealing a micro-propynylidene coplanar with two Ta atoms; as of February 2003. medical device manufacturer; Reactivity of a new organometallic functional group.

A method to rapidly diversify the molecules formed in organic crystals is introduced, with aryl nitriles playing a novel dual role as both hydrogen-bond acceptors and modifiable organic groups. The discovery of coexisting supramolecular synthons in the same crystal is also described. The general concept is demonstrated by using a bis(aryl nitrile) alkene that undergoes a hydrogen-bond-directed intermolecular [2+2] photodimerization to form a tetra(aryl nitrile)cyclobutane. The product is readily converted by click reactivity to a tetra(aryl tetrazole) and by hydrolysis to a tetra(aryl carboxylic acid). The integration of aryl nitriles into solid-state reactions opens broad avenues to post-modify products formed in crystalline solids for rapid diversification., (© 2022 Wiley-VCH GmbH.)

Cocrystallizations of diboronic acids [1,3-benzenediboronic acid (1,3-bdba), 1,4-benzenediboronic acid (1,4-bdba) and 4,4'-biphenyldiboronic acid (4,4'-bphdba)] and bipyridines [1,2-bis(4-pyridyl)ethylene (bpe) and 1,2-bis(4-pyridyl)ethane (bpeta)] generated the hydrogen-bonded 1 : 2 cocrystals [(1,4-bdba)(bpe) 2 ] (1), [(1,4-bdba)(bpeta) 2 ] (2), [(1,3-bdba)(bpe) 2 (H 2 O) 2 ] (3) and [(1,3-bdba)(bpeta) 2 (H 2 O)] (4), wherein 1,3-bdba involved hydrated assemblies. The linear extended 4,4'-bphdba exhibited the formation of 1 : 1 cocrystals [(4,4'-bphdba)(bpe)] (5) and [(4,4'-bphdba-me)(bpeta)] (6). For 6, a hemiester was generated by an in-situ linker transformation. Single-crystal X-ray diffraction revealed all structures to be sustained by B(O)-H⋅⋅⋅N, B(O)-H⋅⋅⋅O, O w -H⋅⋅⋅O, O w -H⋅⋅⋅N, C-H⋅⋅⋅O, C-H⋅⋅⋅N, π⋅⋅⋅π, and C-H⋅⋅⋅π interactions. The cocrystals comprise 1D, 2D, and 3D hydrogen-bonded frameworks with components that display reactivities upon cocrystal formation and within the solids. In 1 and 3, the C=C bonds of the bpe molecules undergo a [2+2] photodimerization. UV radiation of each compound resulted in quantitative conversion of bpe into cyclobutane tpcb. The reactivity involving 1 occurred via 1D-to-2D single-crystal-to-single-crystal (SCSC) transformation. Our work supports the feasibility of the diboronic acids as formidable structural and reactivity building blocks for cocrystal construction., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The genus Sphaerostilbella comprises fungi that colonize basidiomata of wood-inhabiting fungi, including important forest pathogens. Studies of fermentation cultures of an isolate (TFC201724) collected on the foothills of Himalayas, and closely related to S. broomeana isolates from Europe, led to the identification of a new cyclic octapeptide along with two closely related analogues ( 1 - 3 ) and four dioxopiperazines ( 4 - 7 ). The structure of the lead compound, broomeanamide A ( 1 ), was assigned mainly by analysis of 2D NMR and HRESIMS data. The structure consisted of one unit each of N -MeVal, Ala, N -MePhe, Pro, Val, and Ile and two N -MeLeu units. The amino acid sequence was determined on the basis of 2D NMR and HRESIMSMS data. NMR and HRMS data revealed that the other two new peptides have the same amino acid composition except that the Ile unit was replaced with Val in one instance ( 2 ) and the N -MeVal unit was replaced with Val in the other ( 3 ). The absolute configuration of 1 was assigned by analysis of the acid hydrolysate by application of Marfey's method using both C 18 and C 3 bonded-phase columns. Broomeanamide A ( 1 ) showed antifungal activity against Cryptococcus neoformans and Candida albicans , with MIC values of 8.0 and 64 μg/mL, respectively.