Multinuclear NMR Spectroscopy Research Articles

3D honeycomb construction of N-fluorodinitromethyl substituted polynitroazoles based on hydrogen-bonded staggered conformation: Toward high-density melt-cast explosive instead of TNT

N-fluorodinitromethyl-functionalized polynitro-triazole/pyrazole were synthesized and characterized by IR spectrum, elemental analysis, multinuclear NMR spectroscopy as well as differential scanning calorimetry. The crystal packing characteristic of honeycomb construction for 5a and inter/intramolecular interactions were thoroughly explored. Compound 5a melts at 74°C and decomposes at 167°C, while compound 5b melts at 47°C and decomposes at 209°C. Further structural analysis was not performed for 5b as its melt point indicates that it is not appropriate for melt-cast explosive. Both new compounds show zero oxygen balance, high density (1.88 g cm−3), negative heats of formation (-101.3 kJ mol−1 for 5a, -123.3 kJ mol−1 for 5b), acceptable sensitivities (IS > 10 J, FS > 168 N) and high detonation performances (vD > 8591 m s−1, P > 32.7 GPa). The resluts of physicochemical properties and detonation performance suggest that 5a could be used as an applicable melt-cast explosive and a replacer for TNT.

Tuning the Properties of 5-Azido and 5-Nitramino-tetrazoles by Diverse Functionalization - General Concepts for Future Energetic Materials.

5‐Azido and 5‐nitraminotetrazole backbones are established heterocyclic motifs in the research field of energetic materials synthesis. Despite the high energy content of the compounds, the problem with many derivatives is that their sensitivities are far too high. Functionalization of one of the ring nitrogen atoms is the aim of this study to adjust the sensitivity by inserting nitratoethyl, azidoethyl and methyl groups. In this context, derivatives of 2‐(2‐azidoethyl)‐5‐nitraminotetrazoles (2, 2 a–2 d), as well as 1‐nitrato and 1‐azidoethyl substituted 5‐azidotetrazole (7 and 10) and the methylation products of 5‐azidotetrazole (5‐azido‐1‐methyl‐tetrazole, 11 and 5‐azido‐2‐methyl‐tetrazole, 12) were prepared. The obtained nitrogen‐rich compounds were extensively characterized through multinuclear NMR spectroscopy and IR spectroscopy. The structural confinement was checked by X‐ray diffraction experiments. The pure samples (verified by elemental analysis) were investigated regarding their behavior toward friction, impact (BAM methods) and electrostatic discharge as well as heating (DTA and DSC). For all metal‐free compounds the detonation properties were computed with the EXPLO5 code using their density and heat of formation, calculated based on CBS‐4 M level of theory.

Revisiting the Three Vanadium Sandwich-Type Polyoxometalates: Structures, Solution Behavior, and Redox Properties.

It is well known that the trivacant anions α-B-[XW9O33]9- react with vanadyl ions to give the sandwich-type polyoxometalates [(VIVO)3(XW9O33)2]12- with X = AsIII or SbIII. Nevertheless, the oxidized derivatives have been obtained selectively by electrochemical oxidation from the fully reduced derivatives [(VIVO)3(XW9O33)2]12- allowing full characterization both in solution using UV-vis and multinuclear (17O, 51V, and 183W) NMR spectroscopies and in the solid state by single-crystal X-ray diffraction. Structural analysis of the oxidized [(VVO)3(XW9O33)2]9- polyanions is consistent with the idealized D3h symmetry, while solution studies reveal a fair hydrolytic stability in a wide pH range from 0 to 6. Besides, the D3h polyanions either as reduced or oxidized forms [(VO)3(AsW9O33)2]9/12- have been identified as the thermodynamic product that results from the conversion of the C2v polyanion [(H2O)(VO)3(AsW9O33)2]9/12- through moderate heating. Conversely, the SbIII-containing derivative gives exclusively the D3h polyanion, probably either due to the extended lone pair of the trigonal SbIII heterogroup that prevents the formation of the C2v arrangement or the lability of the oxo-metalate bonds that favor chemical exchange. The electrochemical studies of sandwich-type polyoxometalates revealed that each {V═O} group gives rise to a one-electron transfer process. At last, the redox properties appear strongly altered in the 0.3-5 pH range, consistent with proton-coupled electron transfers.

Ambiguous structure determination from powder data: four different structural models of 4,11-di-fluoro-quinacridone with similar X-ray powder patterns, fit to the PDF, SSNMR and DFT-D.

Four different structural models, which all fit the same X-ray powder pattern, were obtained in the structure determination of 4,11-di-fluoro-quinacridone (C20H10N2O2F2) from unindexed X-ray powder data by a global fit. The models differ in their lattice parameters, space groups, Z, Z', molecular packing and hydrogen bond patterns. The molecules form a criss-cross pattern in models A and B, a layer structure built from chains in model C and a criss-cross arrangement of dimers in model D. Nevertheless, all models give a good Rietveld fit to the experimental powder pattern with acceptable R-values. All molecular geometries are reliable, except for model D, which is slightly distorted. All structures are crystallochemically plausible, concerning density, hydrogen bonds, intermolecular distances etc. All models passed the checkCIF test without major problems; only in model A a missed symmetry was detected. All structures could have probably been published, although 3 of the 4 structures were wrong. The investigation, which of the four structures is actually the correct one, was challenging. Six methods were used: (1) Rietveld refinements, (2) fit of the crystal structures to the pair distribution function (PDF) including the refinement of lattice parameters and atomic coordinates, (3) evaluation of the colour, (4) lattice-energy minimizations with force fields, (5) lattice-energy minimizations by two dispersion-corrected density functional theory methods, and (6) multinuclear CPMAS solid-state NMR spectroscopy (1H, 13C, 19F) including the comparison of calculated and experimental chemical shifts. All in all, model B (perhaps with some disorder) can probably be considered to be the correct one. This work shows that a structure determination from limited-quality powder data may result in totally different structural models, which all may be correct or wrong, even if they are chemically sensible and give a good Rietveld refinement. Additionally, the work is an excellent example that the refinement of an organic crystal structure can be successfully performed by a fit to the PDF, and the combination of computed and experimental solid-state NMR chemical shifts can provide further information for the selection of the most reliable structure among several possibilities.

Studies on the interaction between oxido/dioxidovanadium(V) compounds and reactive oxygen species: Synthesis, characterization, and photophysical investigation

Singlet oxygen (1O2) and hypochlorite (OClˉ) are two principal non-radical reactive oxygen species (ROS) which, are produced in a number of biochemical processes. In cellular systems, these analytes play various important roles. In this article, we report two mononuclear oxido- and dioxidovanadium(V) compounds 1 and 2 of an intramolecularly hydrogen bonded luminescent zwitterion ligand (HL). Single crystal X-ray diffraction analysis and multinuclear (1H and 51V) NMR spectroscopy provided the identities of 1 and 2 in the solid and solution states, respectively. Both 1 and 2 are water soluble and fluorescent. Fluorescence of the ligand HL is responsible for the fluorescent nature of 1 and 2. Protonation of the hanging amine moiety of the ligand remained unchanged in the vanadium complexes 1 and 2. However, the intramolecular H-bonding is not present in 1 and 2. Hydrophilicity and luminescent nature of the vanadium complexes provided us the opportunity to study the interaction of 1 and 2 with different ROS. Excited state photophysical investigations revealed highly selective instant response of the probes 1 and 2 for singlet oxygen and hypochlorite. Specific response of the dioxidovanadium(V) complex 1 towards singlet oxygen/hypochlorite remained unchanged in presence of other challenging ROS. Spectrofluorimetric titration provided limit of detection around 180 nM for 1O2. 1H NMR and theoretical calculations provided further information on the interactions between vanadium compound and analyte.

Synthesis, Photophysical, Electrochemical, and Non-linear Optical Properties of Triaryl Pyrazole-based B-N Coordinated Boron Compounds.

We report here a set of triaryl pyrazole based B-N coordinated boron compounds (11-17) synthesized by electrophilic aromatic borylation strategy. All the pyrazole boron compounds were thoroughly characterized using multinuclear NMR spectroscopy, LC-MS, and single crystal X-ray diffraction analysis (for 12-17). The photoluminescence measurements of 11-17 revealed that the emission peak maxima were tuned based on the substitution on N-phenyl. The photophysical and electrochemical properties were further supported by theoretical calculations. Z-scan based investigations at 515 nm pump wavelength showed that B-N coordination led to enhancement of nonlinear absorption (two-photon absorption (TPA)) in these compounds if an electron deficient moiety is attached. It has also been observed that an appropriate choice of moiety allows to optimally maneuver the molecular polarizability of the π-system and consequently, assists in controlling the third-order nonlinear optical response.

Switching on Cytotoxicity of Water-Soluble Diiron Organometallics by UV Irradiation.

The diiron compounds [Fe2Cp2(CO)2(μ-CO)(μ-CSEt)]CF3SO3, [1]CF3SO3, K[Fe2Cp2(CO)3(CNCH2CO2)], K[2], [Fe2Cp2(CO)2(μ-CO)(μ-CNMe2)]NO3, [3]NO3, [Fe2Cp2(CO)2(PTA){μ-CNMe(Xyl)}]CF3SO3, [4]CF3SO3, and [Fe2Cp2(CO)(μ-CO){μ-η:1η3-C(4-C6H4CO2H)CHCNMe2}]CF3SO3, [5]CF3SO3, containing a bridging carbyne, isocyanoacetate, or vinyliminium ligand, were investigated for their photoinduced cytotoxicity. Specifically, the novel water-soluble compounds K[2], [3]NO3, and [4]CF3SO3 were synthesized and characterized by elemental analysis and IR and multinuclear NMR spectroscopy. Stereochemical aspects concerning [4]CF3SO3 were elucidated by 1H NOESY NMR and single-crystal X-ray diffraction. Cell proliferation studies on human skin cancer (A431) and nontumoral embryonic kidney (HEK293) cells, with and without a 10-min exposure to low-power UV light (350 nm), highlighted the performance of the aminocarbyne [3]NO3, nicknamed NIRAC (Nitrate-Iron-Aminocarbyne), which is substantially nontoxic in the dark but shows a marked photoinduced cytotoxicity. Spectroscopic (IR, UV-vis, NMR) measurements and the myoglobin assay indicated that the release of one carbon monoxide ligand represents the first step of the photoactivation process of NIRAC, followed by an extensive disassembly of the organometallic scaffold.

Synthesis and properties of a new nine-membered triphospha-macrocyclic complex via a manganese(I) tricarbonyl template

Reaction of the primary diphosphine H2P(CH2)2PH2 with [MnBr(CO)5], followed by removal of the bromide by treatment with AgOTf (OTf = CF3SO3) and addition of PAr3 (Ar = o-C6H4F), gives the acyclic precursor complex, fac-[Mn(CO)3{H2P(CH2)2PH2}(PAr3)][OTf], thus positioning the primary phosphine functions adjacent to the o-fluorophenyl substituents. The identity of this species was confirmed by multinuclear NMR (1H, 19F{1H}, 31P{1H} and 55Mn) and IR spectroscopic analysis, as well as from a single crystal X-ray analysis. Subsequent treatment of this complex with KOtBu (potassium tertiary butoxide) causes a double P-C coupling reaction, with defluorination of two aryl groups, and leads to formation of a nine-membered triphosphine macrocyclic complex. Methylation (KOtBu/MeI) of the two remaining secondary phosphine function yields the complex [Mn(CO)3(1)][OTf], which has been characterised similarly by multinuclear NMR and IR spectroscopy, and by electrospray mass spectrometry. A single crystal X-ray structure determination confirms the distorted octahedral coordination at Mn(I), with the triphosphine macrocycle occupying three mutually facial coordination sites. As expected, this complex is extremely thermodynamically stable and kinetically inert, being unaffected by prolonged refluxing with either Me3NO or thiophenolate in MeCN.

Supramolecular architectures in novel diphenyl(aryl)tin(IV) chlorides

The diphenyl(aryl)tin(IV) chloride [2-{(CH2O)2CH)}C6H4]SnPh2Cl (1) was prepared reacting [2-{(CH2O)2CH)}C6H4]Li with Ph2SnCl2. Hydrolysis of 1 with p-toluenesulfonic acid as a proton source gave [2-(OCH)C6H4]SnPh2Cl (2), which in turn was reacted with 2-(aminomethyl)pyridine, benzidine, 1-aminopyrene, in the absence of a solvent or catalyst, to afford the mono- or bimetallic species [2-(2′-PyCH2NCH)C6H4]SnPh2Cl (3), ClSnPh2[2-C6H4(4-CHN-1,1′-C6H4C6H4-4′-NCH)-2′-C6H4]Ph2SnCl (4) and [2-(C16H12NCH)C6H4]SnPh2Cl (5) (Py = pyridyl, C16H12 = pyrene). The compounds were characterized by multinuclear NMR spectroscopy and mass spectrometry in solution and IR spectroscopy in solid state. The molecular structures for compounds 1–5 were established by single-crystal X-ray diffraction. For all compounds the metal center is pentacoordinated with a distorted trigonal bipyramidal geometry and a (C,E)C2SnX core (E = O, Nimine) as a result of intramolecular E→Sn interactions. The presence of CH···Cl and CH···π (Phcentroid, Pycentroid, Pyrenecentroid) intermolecular interaction led to the formation of supramolecular associations in solid state for all compounds, thus, ribbon-like polymer occurs in crystal of 1, 2D layers arise in the case of 2 and 4, and complex 3D architectures are found in 3 and 5.

P-Ru-Complexes with a Chelate-Bridge-Switch: A Comparison of 2-Picolyl and 2-Pyridyloxy Moieties as Bridging Ligands.

Starting from [Ru(pyO)2(nbd)] 1 and a N,P,N-tridentate ligand (2a: PhP(pic)2, 2b: PhP(pyO)2) (nbd = 2,5-norbornadiene, pic = 2-picolyl = 2-pyridylmethyl, pyO = 2-pyridyloxy = pyridine-2-olate), the compounds [PhP(μ-pic)2(μ-pyO)Ru(κ2-pyO)] (3a) and [PhP(μ-pyO)3Ru(κ2-pyO)] (3b), respectively, were prepared. Reaction of compounds 3 with CO and CNtBu afforded the opening of the Ru(κ2-pyO) chelate motif with the formation of compounds [PhP(μ-pic)2(μ-pyO)Ru(κ-O-pyO)(CO)] (4a), [PhP(μ-pic)2(μ-pyO)2Ru(CNtBu)] (5a), [PhP(μ-pyO)4Ru(CO)] (4b) and [PhP(μ-pyO)4Ru(CNtBu)] (5b). In dichloromethane solution, 4a underwent a reaction with the solvent, i.e., substitution of the dangling pyO ligand by chloride with the formation of [PhP(μ-pic)2(μ-pyO)Ru(Cl)(CO)] (6a). The new complexes 3a, 4a, 5a, 5b and 6a were characterized by single-crystal X-ray diffraction analyses and multi-nuclear (1H, 13C, 31P) NMR spectroscopy. The different coordination behaviors of related pairs of molecules (i.e., pairs of 3, 4 and 5), which depend on the nature of the P–Ru-bridging ligand moieties (μ-pic vs. μ-pyO), were also studied via computational analyses using QTAIM (quantum theory of atoms in molecules) and NBO (natural bond orbital) approaches, as well as the NCI (non-covalent interactions descriptor) for weak intramolecular interactions.

CO2 Adsorption on the N- and P-Modified Mesoporous Silicas.

SBA-15 and MCM-48 mesoporous silicas were modified with functionalized (3-aminopropyl)triethoxysilane (APTES) by using the post-synthesis method, thus introducing N- and P-containing groups to the pore surface. The structure of the newly synthesized modifiers (aldimine and aminophosphonate derivatives of (3-aminopropyl)triethoxysilane and their grafting onto the porous matrix were proved by applying multinuclear NMR and FTIR spectroscopies. The content of the grafted functional groups was determined via thermogravimetric analysis. The physicochemical properties of the adsorbent samples were studied by nitrogen physisorption and UV–Vis spectroscopy. The adsorption capacity of CO2 was measured in a dynamic CO2 adsorption regime. The modified silicas displayed an enhanced adsorption capacity compared to the initial material. The 13C NMR spectra with high-power proton decoupling proved the presence of physically captured CO2. A value of 4.60 mmol/g was achieved for the MCM-48 material grafted with the Schiff base residues. The total CO2 desorption was achieved at 40 °C. A slight decrease of about 5% in CO2 adsorption capacities was registered for the modified silicas in three adsorption/desorption cycles, indicating their performance stability.

Synthesis, structure and hydrolysis studies of pseudostannatranes: Kinetic studies of a hexanuclear tin(IV) hydroxo-cluster formed via reverse Kocheshkov reaction and partial hydrolysis of pseudostannatrane

The structural and synthetic aspects of novel mononuclear pseudostannatranes and a hexanuclear tin(IV) hydroxo-cluster have been reported. The reaction of the bis-phenolate aminoethanol tripodal ligand N(CH2CH2OH){CH2(2,4-di-t-Bu-C6H2OH)}2 (H3L) with BuSnCl3, PhSnCl3 and SnCl4 yielded the mononuclear pseudostannatranes [N(CH2CH2O){CH2(2,4-di-t-Bu-C6H2O)}2Sn(n-Bu)H2O] (1), [N(CH2CH2O) {CH2(2,4-di-t-Bu-C6H2O)}2Sn(Ph)EtOH] (2) and [N(CH2CH2OH){CH2(2,4-di-t-Bu-C6H2O)}2Sn(Cl)2] (3), respectively. The reaction of the ligand with PhSnCl3 using triethylamine as a base produced the reverse Kocheshkov product [N(CH2CH2OH){CH2(2,4-di-t-Bu-C6H2O)}2Sn(Cl)2].1/3NEt3 (3.1/3NEt3), which on partial hydrolysis yielded the hexanuclear tin(IV) hydroxo-cluster [N(CH2CH2O){CH2(2,4-di-t-BuC6H2O)}2SnCl]2{(OH)3SnPh(OH)2SnPh(OH)3}[SnN(CH2 CH2O){CH2(2,4-di-t-Bu-C6H2O)}2]2 (4). The synthesized compounds were characterized by elemental analysis, infrared spectroscopy, multi-nuclear NMR spectroscopy, electrospray ionization mass spectrometry and single-crystal X-ray diffraction. In addition, vital facts regarding the kinetics of the partial hydrolysis of the reverse Kocheshkov product to form the hydroxo cluster were explained by 119Sn NMR spectroscopy.

Diphenyl‐ and Dimesityl‐Phosphanyl‐Substituted 3,3,4,4,5,5‐Hexafluorocyclopentenyl‐Gold(I) Dimers – Syntheses and Solid‐State Structures

Abstract1,2‐Dichloro‐3,3,4,4,5,5‐hexafluorocyclopentene (F6cypCl2) was functionalized with diphenyl‐ and dimesitylphosphanyl groups by a salt‐elimination reaction of the respective chlorophosphane (PPh2Cl, PMes2Cl) with in situ generated lithiated F6cyp(Li)Cl. F6cyp(PR2)Cl (R=Ph, Mes) was functionalised again to obtain the corresponding trimethylstannyl substituted compounds F6cyp(PR2)(SnMe3) (R=Ph, Mes). These tin‐precursors were used in tin‐gold exchange reactions to synthesize the dinuclear gold(I) dimers [F6cyp(PR2)Au]2 (R=Ph, Mes). For the mesityl substituted compound, the phosphanegold chloride adduct F6cyp(PMes2AuCl)(SnMe3), the intermediate of the tin‐gold exchange reaction, could also be isolated. All compounds were characterized by multinuclear NMR spectroscopy and X‐ray diffraction experiments.

Self-assembly synthesis of diorganotin complexes based on arylformylhydrazone possessing ONO donor set: anticancer activity and mechanism.

Fourteen new organotin(IV) complexes were successfully synthesized and characterized by elemental analyses, Fourier transform infrared spectroscopy (FT-IR), multinuclear (1H, 13C, and 119Sn) NMR spectroscopy, high-resolution mass spectrometry (HRMS), and X-ray single-crystal techniques. Crystallographic data showed that the complexes 1b, 2b, 3b, and 5b were macrocyclic compounds, 4b exhibited a one-dimensional spiral chain structure with distorted trigonal bipyramidal geometry, other complexes were centrosymmetric dimers, and there was an Sn2O2 four-membered ring in the middle of the molecule. In-vitro anticancer activity against the three human tumor cell lines NCI-H460, MCF-7, and HepG2 was studied, and the dibutyltin complex 5a is a more potent antitumor agent than other complexes and cisplatin. Cell apoptosis study of 5a with the highest activity on HepG2 cancer cell lines was done by flow cytometry; it was shown that the antitumor activity of 5a was related to apoptosis, and it inhibited proliferation by blocking cells in the G2/M phase. The single-cell gel electrophoresis assay results show that 5a induces DNA damage. 5a interacts with ct-DNA by intercalating the mode of interaction. UV-visible absorption spectrometry, fluorescence competitive, viscosity measurements, and gel electrophoresis results also support the intercalative mode of interaction for 5a with DNA.

Silver(I) and gold(I) complexes of multidentate ligands based on functionalized pyridine

The new ligands 2,6-bis[{2′-(N,N-dialkylaminomethyl)phenylselanyl}methyl]pyridine with the general formula 2,6-[{2′-(R2NCH2)C6H4}SeCH2]2C5H3N [R = Me (L1), Et (L2)], based on pyridine functionalized with organoselenium groups, were obtained by reacting 2-(R2NCH2)C6H4SeNa with 2,6–bis(bromomethyl)pyridine in 2:1 molar ratio. The coordination behaviour of the potentially multidentate ligands was investigated towards gold(I) and silver(I) in reactions with AgOTf (OTf = CF3SO3), AgPF6 and (C6F5)Au(tht) (tht = tetrahydrothiophene), when the metal complexes [AgL]X [X = OTf, L = L1 (1), L2 (2); X = PF6, L = L1 (3), L2 (4)], [(C6F5Au)2L1] (5) and [(C6F5)AuL2] (6), were isolated. Multinuclear NMR spectroscopy (1H, 13C, 19F, 31P, 77Se, as appropriate) and mass spectrometry were employed to investigate the two ligands and the metal complexes in solution. The single crystal X-ray diffraction studies revealed a N,Se,N,Se,N-monometallic pentaconnective (κ2Se1,Se2-κ3N1,N2,N3) coordination behaviour of L1 in 1, a Se,N- bimetallic biconnective (bridging) [μ(Au-Au)(1κ1N1-2κ1Se2) coordination behaviour of L1 in 5 and a Se,N,Se-monometallic triconnective (pincer like, κ2Se1,Se2-κN1) pattern of L2 in 6, while in the free ligands the nitrogen atoms of the two pendant arms are intramolecularly coordinated to selenium. In solid state, both 5 and 6 display metallophilic Au‧‧‧Au interactions.

Aggregation of Copper(I) and Silver(I) Chloride Phosphane Complexes Determined by Aryl‐Stacking and Weak Hydrogen Bonds in the Ligand Periphery

AbstractStarting from pentafluorobenzene and 1,2,3,4‐tetrafluorobenzene, the phosphane ligands (o‐C6F4R)Me2P (R=H, F), as well as their copper(I) and silver(I) chloride complexes [(o‐C6F4R)Me2P]2MCl (M=Cu, Ag; R=H, F) were synthesized. All complexes were characterized by multinuclear NMR spectroscopy and CHN analyses. Their solid‐state structures were determined by X‐ray diffraction experiments and compared with each other with regard to their aggregation motifs. The aggregation in solution was investigated by variable‐temperature diffusion‐ordered NMR spectroscopy (VT‐DOSY) experiments.

Multinuclear solid-state NMR: Unveiling the local structure of defective MOF MIL-120

Metal-organic frameworks (MOFs) are emerging materials with many current and potential applications due to their unique properties. One critical feature is that the physical and chemical properties of MOFs are tunable. One of the methods for tuning MOF properties is to introduce defects by design for desired applications. Characterization of MOF defects is important, but very challenging due to the local nature and short-range ordering. In this work, we have introduced the ordered vacancies (the defects) in the form of the coordinatively unsaturated sites (CUSs) into the framework of MOF MIL-120(Al). The creation of ordered vacancies is achieved by replacing one quarter of the BTEC (1,2,4,5-benzenetetracarboxylate) with BDC (benzene-1,4-dicarboxylate) linkers. Both parent and defective MOFs were characterized by multinuclear solid-state NMR spectroscopy. 1H MAS NMR is used to characterize the hydrogen bonding in these MOFs, whereas 13C CP MAS NMR confirms unambiguously that the BDC is incorporated into the framework. One-dimensional 27Al MAS NMR provides direct evidence of the coordinatively unsaturated Al sites (the defects). Furthermore, 27Al 3QMAS experiments at 21.1 ​T allow direct identification of one penta-coordinated and three chemically inequivalent octahedral Al sites in the defective MIL-120(Al). Two of the above-mentioned octahedral Al sites are in the domain which appears defect-free. The third octahedral Al site is near the defective site. This work clearly demonstrates the power of solid-state NMR spectroscopy for characterization of defective MOFs.

A New Class of Task-Specific Imidazolium Salts and Ionic Liquids and Their Corresponding Transition-Metal Complexes for Immobilization on Electrochemically Active Surfaces.

Adding to the versatile class of ionic liquids, we report the detailed structure and property analysis of a new class of asymmetrically substituted imidazolium salts, offering interesting thermal characteristics, such as liquid crystalline behavior, polymorphism or glass transitions. A scalable general synthetic procedure for N‐polyaryl‐N’‐alkyl‐functionalized imidazolium salts with para‐substituted linker (L) moieties at the aryl chain, namely [LPh m ImHR]+ (L=Br, CN, SMe, CO2Et, OH; m=2, 3; R=C12, PEG n ; n=2, 3, 4), was developed. These imidazolium salts were studied by single‐crystal X‐ray diffraction (SC‐XRD), NMR spectroscopy and thermochemical methods (DSC, TGA). Furthermore, these imidazolium salts were used as N‐heterocyclic carbene (NHC) ligand precursors for mononuclear, first‐row transition metal complexes (MnII, FeII, CoII, NiII, ZnII, CuI, AgI, AuI) and for the dinuclear Ti‐supported Fe‐NHC complex [(OPy)2Ti(OPh2ImC12)2(FeI2)] (OPy=pyridin‐2‐ylmethanolate). The complexes were studied concerning their structural and magnetic behavior via multi‐nuclear NMR spectroscopy, SC‐XRD analyses, variable temperature and field‐dependent (VT‐VF) SQUID magnetization methods, X‐band EPR spectroscopy and, where appropriate, zero‐field 57Fe Mössbauer spectroscopy.

Sigma/pi Bonding Preferences of Solvated Alkali-Metal Cations to Ditopic Arylmethyl Anions.

Arylmethyl anions allow alkali‐metals to bind in a σ‐fashion to the lateral carbanionic centre or a π‐fashion to the aryl ring or in between these extremities, with the trend towards π bonding increasing on descending group 1. Here we review known alkali metal structures of diphenylmethane, fluorene, 2‐benzylpyridine and 4‐benzylpyridine. Next, we synthesise Li, Na, K monomers of these diarylmethyls using polydentate donors PMDETA or Me6TREN to remove competing oligomerizing interactions, studying the effect that two aromatic rings has on negative charge (de)localisation via NMR, X‐ray crystallographic and DFT studies. Diphenylmethyl and fluorenyl anions maintain C(H)−M interactions regardless of alkali‐metal, although the adjacent arene carbons engage in interactions with larger alkali‐metals. Introducing a nitrogen atom into the ring (at the 2‐ or 4‐position) encourages relocalisation of negative charge away from the deprotonated carbon and onto nitrogen. Phenyl(2‐pyridyl)methyl moves from an enamide formation at one extremity (lithium) to an aza‐allyl formation at the other extremity (potassium), while C‐ or N‐coordination modes become energetically viable for Na and K phenyl(4‐pyridyl)methyl complexes.

New Pt(II) diiodido complexes containing bidentate 1,3,4-thiadiazole-based ligands: Synthesis, characterization, cytotoxicity

Two diiodidoplatinum(II) complexes [PtI2(L1)] (1) and [PtI2(L2)] (2) with isomeric bidentate 1,3,4-thiadiazole-based N-donor ligands (L1, L2) were prepared and characterized by multinuclear NMR spectroscopy, elemental analysis, infrared spectroscopy and mass spectrometry. Complexes 1 and 2 were hydrolytically stable in 50% DMF-d7/50% D2O and 50% DMF-d7/50% PBS in D2O (pH 7.4). Cytotoxicity of 1 and 2 was evaluated on five human cancer cell lines, i.e. lung carcinoma (A549), hepatocellular carcinoma (HepG2), melanoma (A375), prostate carcinoma (DU-145) and breast carcinoma (MCF-7). Only the HepG2 (IC50 = 22.0 and 17.8 μM for 1 and 2, respectively) and A549 (IC50 = 18.5 μM for 1) cells were sensitive to the studied complexes, but their in vitro cytotoxicity was slightly lower than determined for the reference drug cisplatin (IC50 = 12.0 and 12.3 μM at the HepG2 and A549 cells, respectively). Both complexes 1 and 2 effectively quenched the fluorescence of the EtBr-DNA system (EtBr = ethidium bromide) but did not interact covalently with guanosine monophosphate used as a model DNA molecule.