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Continuous flow technology was exploited for the effective generation of nitrile imines via photolysis of substituted aryl tetrazoles. The resulting photo-click process rapidly affords advanced nitrogen-rich scaffolds upon the subsequent trapping of the reactive dipole with alkenes, alkynes, and benzylic amines. Crucially, this approach uncovers the differential reactivity for ether vs amine tethers, thus providing facile and scalable access to underexplored medicinally relevant heterocyclic entities.

In exploring structural and functional mimics of nitrile hydratases, we report the synthesis of the pseudo-trigonal bipyramidal CoIIcomplexes (K)[CoII(DMF)(LPh)] (1(DMF)), (NMe4)2[CoII(OAc)(LPh)] (1(OAc)), and (NMe4)2[CoII(OH)(LPh)] (1(OH)) (LPh= 2,2',2’’-nitrilo-tris-(N-phenylacetamide; DMF = N,N-dimethylformamide; –OAc = acetate)). The complexes were characterized using NMR, FT-IR, ESI-MS, electronic absorption spectroscopy, and X-ray crystallography, showing the LPhligand to bind in a tetradentate tripodal fashion alongside the respective ancillary donor. One of the complexes, 1(OH), is an unusual structural and functional mimic of the Co active site in Co nitrile hydratases. 1(OH)reacted with acetonitrile to yield the CoII-acetamide complex (NMe4)2[CoII(NHC(O)CH3)(LPh)], 2, which was also thoroughly characterized. In the presence of excess hydroxide, 1(OH)was found to catalyze quantitative conversion of the added hydroxide into acetamide. Despite the differences in Co oxidation state in nitrile hydratases and 1(OH)(CoIIIversus CoII, respectively), 1(OH)was nonetheless an effective nitrile hydration catalyst, selectively producing acetamide over multiple turnovers.

Acid–base multicomponent systems have become a popular choice as a strategy to fine-tune the physicochemical properties of active pharmaceutical ingredients. Current prediction tools based on the principles of anticrystal engineering cannot always accurately predict the nature of intermolecular interactions within a multicomponent system. Even small changes in the physicochemical parameters of parent components can result in unexpected outcomes, and many salt, cocrystal, and ionic liquid forms are still being discovered empirically. In this work, we aimed to establish structural consistency in a series of mixtures comprising lidocaine (LID) with decanedioic, undecanedioic, dodecanedioic, and tridecanedioic acids and to explore how length and flexibility of the acid carbon backbone affect the molecular recognition, crystallization, and thermal behavior of the expected binary systems. We found that neat grinding of LID with dicarboxylic acids results in the formation of eutectic phases. The observed eutectic melting points deviated from the ideal eutectic temperatures predicted by the Schroeder van Laar model because of hydrogen bonding between the reacting components within the mixtures. Furthermore, thermal and infrared analysis provided evidence for the possible formation of new phases stemming from partial ionization of the counterions. Besides, the structure of a previously undetermined form I of the tridecanedioic acid was solved by single crystal X-ray diffraction.

The bicyclo[1.1.1]pentane (BCP) unit is under scrutiny as a bioisostere in drug molecules. We employed methodologies for the synthesis of different BCP triazole building blocks from one precursor, 1-azido-3-iodobicyclo[1.1.1]pentane, by “click” reactions and integrated cycloaddition–Sonogashira coupling reactions. Thereby, we accessed 1,4-disubstituted triazoles, 5-iodo-1,4,5-trisubstituted triazoles, and 5-alkynylated 1,4,5-trisubstituted triazoles. This gives entry to the synthesis of multiply substituted BCP triazoles on either a modular or a one-pot basis. These methodologies were further utilized for appending porphyrin moieties onto the BCP core.

The ability to cover the face of a porphyrin macrocycle selectively is an attractive feature for concepts such as catalysis and anion binding that is reliant on porphyrin core interactions. Herein, we have synthesized a family of mono-urea functionalized porphyrin complexes with intent to investigate their potential to form core···π interactions selectively to one face of the porphyrin macrocycle. By altering the distance between the urea moiety and the porphyrin through direct linkage or introducing a linker group we can control the formation of the core interactions. This is clearly seen in the crystal structure of 1-phenyl-3-(2-([10,15,20-triphenylporphyrinato]zinc(II)-5-yl)phenyl)urea where a unique face capping effect is demonstrated. In the crystal of this complex, there is a hydrogen-bonding network between the urea group and the axial methanol ligand forming head-to-tail aggregates with the Zn–O axis all molecules pointing in one direction.

It is well established that oxaliplatin, one of the three Pt(II) anticancer drugs approved worldwide, and phenanthriplatin, an important preclinical monofunctional Pt(II) anticancer drug, possess a different mode of action from that of cisplatin and carboplatin, namely, the induction of nucleolar stress. The exact mechanisms that lead to Pt-induced nucleolar stress are, however, still poorly understood. As such, studies aimed at better understanding the biological targets of both oxaliplatin and phenanthriplatin are urgently needed to expand our understanding of Pt-induced nucleolar stress and guide the future design of Pt chemotherapeutics. One approach that has seen great success in the past is the use of Pt-click complexes to study the biological targets of Pt drugs. Herein, we report the synthesis and characterization of the first examples of click-capable phenanthriplatin complexes. Furthermore, through monitoring the relocalization of nucleolar proteins, RNA transcription levels, and DNA damage repair biomarker γH2AX, and by investigating their in vitrocytotoxicity, we show that these complexes successfully mimic the cellular responses observed for phenanthriplatin treatment in the same experiments. The click-capable phenanthriplatin derivatives described here expand the existing library of Pt-click complexes. Significantly they are suitable for studying nucleolar stress mechanisms and further elucidating the biological targets of Pt complexes.

Porphyrin-based metal–organic frameworks (MOFs) are attractive materials for photo- and thermally activated catalysis due to their unique structural features related to the porphyrin moiety, guest-accessible porosity, and high chemical tunability. In this study, we report the synthetic incorporation of nonplanar β-ethyl-functionalized porphyrin linkers into the framework structure of PCN-222, obtaining a solid-solution series of materials with different modified linker contents. Comprehensive analysis by a combination of characterization techniques, such as NMR, UV–vis and IR spectroscopy, powder X-ray diffraction, and N2sorption analysis, allows for the confirmation of linker incorporation. A detailed structural analysis of intrinsic material properties, such as the thermal response of the different materials, underlines the complexity of synthesizing and understanding such materials. This study presents a blueprint for synthesizing and analyzing porphyrin-based mixed-linker MOF systems and highlights the hurdles of characterizing such materials.

Oxygenases have been postulated to utilize d4FeIVand d8CuIIIoxidants in proton-coupled electron transfer (PCET) hydrocarbon oxidation. In order to explore the influence the metal ion and d-electron count can hold over the PCET reactivity, two metastable high-valent metal–oxygen adducts, [NiIII(OAc)(L)] (1b) and [CuIII(OAc)(L)] (2b), L = N,N′-(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamidate, were prepared from their low-valent precursors [NiII(OAc)(L)]−(1a) and [CuII(OAc)(L)]−(2a). The complexes 1a/b–2a/bwere characterized using nuclear magnetic resonance, Fourier transform infrared, electron paramagnetic resonance, X-ray diffraction, and absorption spectroscopies and mass spectrometry. Both complexes were capable of activating substrates through a concerted PCET mechanism (hydrogen atom transfer, HAT, or concerted proton and electron transfer, CPET). The reactivity of 1band 2btoward a series of para-substituted 2,6-di-tert-butylphenols (p-X-2,6-DTBP; X = OCH3, C(CH3)3, CH3, H, Br, CN, NO2) was studied, showing similar rates of reaction for both complexes. In the oxidation of xanthene, the d8CuIIIoxidant displayed a small increase in the rate constant compared to that of the d7NiIIIoxidant. The d8CuIIIoxidant was capable of oxidizing a large family of hydrocarbon substrates with bond dissociation enthalpy (BDEC–H) values up to 90 kcal/mol. It was previously observed that exchanging the ancillary anionic donor ligand in such complexes resulted in a 20-fold enhancement in the rate constant, an observation that is further enforced by comparison of 1band 2bto the literature precedents. In contrast, we observed only minor differences in the rate constants upon comparing 1bto 2b. It was thus concluded that in this case the metal ion has a minor impact, while the ancillary donor ligand yields more kinetic control over HAT/CPET oxidation.

GANT61-D is an important hedgehog pathway inhibitor and an interesting ligand candidate for metal coordination. The first examples of metal complexes of the potent hedgehog pathway inhibitor GANT61-D are described. The reaction of Ni(II), Pd(II), and Pt(II) precursors with the hedgehog pathway inhibitor GANT61-D gave [NiII(GANT61-D)(OH2)3(μ2-SO4)(μ3-SO4)] (1), [PdII(Cl)(GANT61-D)]Cl (2), [PtII(Cl)(GANT61-D)]Cl, and [PtII(CBDCA–2H)(GANT61-D)]. X-ray crystal structure analysis revealed that GANT61-D is a versatile N-donor ligand that can act as a bidentate ligand via the diaminopropane (DAP) N atoms or a tridentate ligand via the DAP N atoms and one dimethylaniline N atom. Protonation constants of the GANT61-D ligand in water and in a 60:40 (w/w) dimethyl sulfoxide–water solvent mixture were determined. Potentiometric and spectroscopic data on the NiII(GANT61-D) system indicate the formation of octahedral 1:1 species with medium stability in solution. 1and 2exhibited noteworthy in vitro cytotoxicity against medulloblastoma cancer cells.

Herein we report the synthesis of 5,10,15,20-tetraaryl-(X)-substituted-2,3,7,8,12,13,17,18-octaethylporphyrins (OETArXPs) and a structural investigation of their solid-state properties via small molecule X-ray diffraction. A series of halogen (fluorine to iodine), nitrogenous (azido, cyano), alkyl (TMS-acetylene and acetylene), and chained (benzyloxy) porphyrins were chosen as the initial target molecules. Following this, a selection of tetravalent metal complexes [Cu(II), Ni(II), and Pd(II)] based on these porphyrins were synthesized to allow for an investigation of the effects of metal complexes on the structural properties of these highly substituted porphyrins. The size of the halogen atom affects the potential of intermolecular interactions and the resulting crystal packing in these 4-halo-OETArXP complexes. The fluorine series have an equal preference for alkyl or aryl groups (ortho-hydrogen), the chlorine series favor interactions between the alkyl groups, and the bromine appears to favor the aryl (ortho- and meta-hydrogens). This results in an extensive cupping pattern in the unit cell. For the 2,6-halo-OETArXP it was established that the change in position alters the types of the intermolecular contacts toward face-to-edge or face-to-face interactions and alters the packing patterns observed. Within the 4-benzyloxy-OETArXP series the meso-substituent favors interacting with the core of the porphyrin macrocycle. The 4-cyano-OETArXP is a suitable hydrogen-bond acceptor and results in an interesting Z-shape network. Additionally, it was highlighted that solvent effects play a much larger role in crystal packing than intermolecular/intramolecular interaction or metal(II) center substitution. This is accompanied by a study using both the azide- and acetylene-OETArXPs as a base molecule to allow for a quick one-step reaction for the generation of a variety of functionalized compounds. Using a copper(I)-catalyzed azide–alkyne cycloaddition reaction, we were able to append hydrogen bonding functionalities to the OETArXPs framework in high yields. The crystal packing images included in this work shows the potential to create selective and functional receptor sites based on free base porphyrins. However, insofar as analytical measurements indicate, the design of such a free base porphyrin through crystal engineering has not yet been realized. The variety of porphyrin packing arrangements herein indicates the need for further studies.

Dehydroalanine (ΔAla) is a highly electrophilic residue that can react efficiently with sulfur nucleophiles to furnish cysteinyl analogues. Herein, we report an efficient synthesis of N-terminal cysteinyl thioesters, suitable for S,N-acyl transfer, based on β,γ-C,S thiol-Michael addition. Both ionic and radical-based methodologies were found to be efficient for this process.

Recent breakthroughs have brought into question the innocence (or not) of carboxamidate donor ligands in the reactivity of high-valent oxidants. To test the reactivity properties of high-valent carboxamidate complexes, [NiII(tBu-terpy)(L)] (1, tBu-terpy = 4,4′,4′′-tri-tert-butyl-2,2′;6′,2″-terpyridine; L = N,N′-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate) was prepared and converted to [NiIII(tBu-terpy)(L)]+(2) using ceric ammonium nitrate. 2was characterized using electronic absorption and electron paramagnetic resonance spectroscopies and electrospray ionization mass spectrometry. 2was found to be a capable oxidant of phenols and through kinetic analysis was found to oxidize these substrates via a nonconcerted or partially concerted proton coupled electron transfer (PCET) mechanism. The products of PCET oxidation of phenols by 2were phenoxyl radical and the protonated form of 1, 1H+. 1H+was crystallographically characterized providing convincing evidence of 1’s ability to act as a proton acceptor. We demonstrate that the complex remained intact through a full cycle of oxidation of 1to 2, PCET of 2to yield 1H+, and deprotonation of 1H+to yield 1followed by reoxidation of 1to yield 2. The N–H bond dissociation energy of the protonated amide in 1H+was determined to be 84 kcal/mol. Our findings illuminate the role carboxamidate ligands can play in PCET oxidation.

A theoretical study has been carried out at the M062X/6-311++G(d,p) computational level to search for a rationale on ligands’ affinity toward α2-adrenoceptors by estimating the nature and strength of intramolecular hydrogen bonds potentially formed (by means of the QTAIM and NBO approaches) as well as the degree of deviation from planarity that could be observed in some of the compounds. Four different families have been studied: thiophen-2-yl, 3-carboxylatethiophen-2-yl esters, 3-cyanothiophen-2-yl, and 2-thiazolyl guanidinium derivatives. In the case of the thiophen-2-yl guanidines not substituted in the 3 position, nonplanarity was always observed, whereas in the thiazole series, intramolecular hydrogen bonds were identified between the guanidinium and the thiazole ring forcing the systems to planarity. Regarding the carboxylic esters, two different rotamers were found: quasi-planar and quasi-perpendicular systems with very similar energy. Both of these isomers can form different nets of intramolecular hydrogen bonds and other types of noncovalent interactions. Different physicochemical properties such as basicity, solubility, or lipophilicity were calculated for these systems, but no correlation to the degree of planarity was found. However, when comparing the α2-ARs affinity with the planarity of the molecules, a trend appears in the thiophen-2-yl guanidinium series indicating that lack of planarity seems to be optimal for α2-ARs engagement.

In the presence of a trityl-substituted cinchona alkaloid-based catalyst, homophthalic, aryl succinic, and glutaconic anhydride derivatives reacted with aromatic and aliphatic aldehydes to produce cis-lactones in up to 90:10 dr and 99% ee. A DFT study has shown how the catalyst is uniquely able to bring about the opposite sense of diastereocontrol to that usually observed.

A novel 1,4-disubstituted 1,2,3-triazole-based ligand, 2-(4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl)propane-1,3-diamine (ptpd), which possesses pyridyl and diamino secondary and tertiary coordinating groups was synthesized in excellent yield. The reactivity of 2-(1-phenyl-1H-1,2,3-triazol-4-yl)pyridine (ptp), di-tert-butyl (2-azidopropane-1,3-diyl)dicarbamate (Boc2-ptpd), and ptpd·3HCl was investigated with Au(III) and Pt(II) precursors. Analysis including X-ray crystal structures of [Au(III)Cl3(ptp)] (1), [Au(III)Cl2(ptpd)][Au(I)Cl2][OH]{[NaAuCl4·2H2O]}n(3), and [Pt(II)Cl2(ptpdH2)][PtCl4] (4) revealed that ptpd (i) serves as a monodentate ligand for Au(III) coordinating to the metal center via the pyridine nitrogen only, (ii) preferentially coordinates Au(III) via the bidentate diamino group over the monodentate pyridine group, (iii) can coordinate Pt(II) in a bidentate fashion via the pyridyl nitrogen and the triazole N-3, and (iv) can bridge two Pt(II) centers through bidentate chelation at the diamino group and bidentate chelation via the pyridyl nitrogen and the triazole N-3. ptpd represents a versatile ligand template for the development of mixed metal complexes.

A series of uranyl thiocyanate and selenocyanate of the type [R4N]3[UO2(NCS)5] (R4= nBu4, Me3Bz, Et3Bz), [Ph4P][UO2(NCS)3(NO3)] and [R4N]3[UO2(NCSe)5] (R4= Me4, nPr4, Et3Bz) have been prepared and structurally characterized. The resulting noncovalent interactions have been examined and compared to other examples in the literature. The nature of these interactions is determined by the cation so that when the alkyl groups are small, chalcogenide···chalcogenide interactions are present, but this “switches off” when R = nPr and charge assisted U═O···H–C and S(e)···H–C hydrogen bonding remain the dominant interaction. Increasing the size of the chain to nBu results in only S···H–C interactions. The spectroscopic implications of these chalcogenide interactions have been explored in the vibrational and photophysical properties of the series [R4N]3[UO2(NCS)5] (R4= Me4, Et4, nPr4, nBu4, Me3Bz, Et3Bz), [R4N]3[UO2(NCSe)5] (R4= Me4, nPr4, Et3Bz) and [Et4N]4[UO2(NCSe)5][NCSe]. The data suggest that U═O···H–C interactions are weak and do not perturb the uranyl moiety. While the chalcogenide interactions do not influence the photophysical properties, a coupling of the U═O and δ(NCS) or δ(NCSe) vibrational modes is observed in the 77 K solid state emission spectra. A theoretical examination of representative examples of Se···Se, C–H···Se, and C–H···O═U by molecular electrostatic potentials and NBO and AIM methodologies gives a deeper understanding of these weak interactions. C–H···Se are individually weak but C–H···O═U interactions are even weaker, supporting the idea that the -yl oxo’s are weak Lewis bases. An Atoms in Molecules study suggests that the chalcogenide interaction is similar to lone pair···π or fluorine···fluorine interactions. An oxidation of the NCS ligands to form [(UO2)(SO4)2(H2O)4]·3H2O was also noted.

Background: Cancers of the lymphatic cells (lymphomas) account for approximately 12% of malignant diseases worldwide. The nitrostyrene scaffold is identified as a lead target structure for the development of particularly effective compounds targeting Burkitt's lymphoma (BL). Objectives: The aims of the curent study were to synthesise a panel of nitrostyrene compounds and to evaluate their activity in Burkitt's lymphoma (BL). Methods: A panel of structurally varied compounds were designed and synthesised using Henry Knoevenagel condensation reactions. Single crystal X-Ray analysis confirmed the E configuration for six examples of these novel structures. A number of nitrostyrene-related compounds were also investigated including 1,3-bis(aryl)-2-nitropropenes together with heterocyclic scaffolds containing the nitrovinyl pharmacophore such as 3-nitro-2-phenyl-2H-chromenes. The antiproliferative activities of the compounds were evaluated using the BL cell lines EBV- MUTU-1 and EBV+ DG- 75 (chemoresistant) to establish preliminary structure-activity relationships. Results: Lead compounds with optimized nitrostyrene scaffolds and 3-nitro-2-phenyl-2Hchromene structures were successfully established with typical IC50 values of 0.45 μM and 0.47 μM in MUTU-1 cells and 1.41 μM and 1.92 μM, respectively, in DG-75 cells. The mechanism of cell death was identified as apoptotic and the lead compound was found to elicit comparable apoptotic effects to Taxol in Burkitt's lymphoma cell lines MUTU-1 and DG-75. Conclusion: This class of pharmaceutically active compounds with potential for the treatment of Burkitt's lymphoma suggest a potential role for nitrostyrene based agents in chemotherapy.

A series of complexes [Et4N][Ln(NCS)4(H2O)4] (Ln = Pr, Tb, Dy, Ho, Yb) have been structurally characterized, all showing the same structure, namely a distorted square antiprismatic coordination geometry, and the Ln–O and Ln–N bond lengths following the expected lanthanide contraction. When the counterion is Cs+, a different structural motif is observed and the eight-coordinate complex Cs5[Nd(NCS)8] isolated. The thorium compounds [Me4N]4[Th(NCS)7(NO3)] and [Me4N]4[Th(NCS)6(NO3)2] have been characterized, and high coordination numbers are also observed. Finally, attempts to synthesize a U(III) thiocyanate compound has been unsuccessful; from the reaction mixture, a heterocycle formed by condensation of five MeCN solvent molecules, possibly promoted by U(III), was isolated and structurally characterized. To rationalize the inability to isolate U(III) thiocyanate compounds, thin-layer cyclic voltammetry and IR spectroelectrochemistry have been utilized to explore the cathodic behavior of [Et4N]4[U(NCS)8] and [Et4N][U(NCS)5(bipy)2] along with a related uranyl compound [Et4N]3[UO2(NCS)5]. In all examples, the reduction triggers a rapid dissociation of [NCS]−ions and decomposition. Interestingly, the oxidation chemistry of [Et4N]3[UO2(NCS)5] in the presence of bipy gives the U(IV) compound [Et4N]4[U(NCS)8], an unusual example of a ligand-based oxidationtriggering a metal-based reduction. The experimental results have been augmented by a computational investigation, concluding that the U(III)–NCS bond is more ionic than the U(IV)–NCS bond.

Di‐ and multiazole‐substituted fluorocyclic products (2–13) were readily synthesized in good to high yields. These were synthesized by nucleophilic substitution reactions of perfluorocycloalkenes with azoles (i.e., imidazole, triazole) involving simple reaction procedures. Interestingly, these azoles were later found to be reactive not only with the vinylic, but also with the allylic fluorine atoms. This resulted in the substitution of up to six azoles on the fluorinated rings. Stoichiometry plays a key role in determining the degree of substitution. For comparison, the analogous reactions of N‐substituted 1‐(trimethylsilyl)‐imidazole and 1‐(trimethylsilyl)‐1,2,4‐triazole were also investigated. All of the new compounds were fully characterized by elemental, spectral (19F, 1H, 13C NMR), and thermal differential scanning calorimetry (DSC) analyses.

High density energetic salts containing nitrogen rich cations and carbonyl‐ or oxalylbis(diamino‐tetrazole) anions, which were obtained from cyanogen azide and hydrazine, were readily synthesized. In every case, a new family of energetic salts 3–14were characterized by vibrational spectroscopy, multinuclear (1H, 13C, 15N) NMR, elemental analyses, density, differential scanning calorimetry and impact sensitivity. Compound 12was structured by single crystal X‐ray diffraction. The densities of 3‐14, determined by gas pycnometer, range between 1.500 and 1.676 g cm−3. The heats of formation and detonation properties for these stable salts were calculated by using Gaussian 03 and Cheetah 5.0, respectively.

Base‐catalyzed activation of the CF bondin the trifluoromethylazo‐substituted cyclic and acyclic alkanes provides a route to disubstituted azidotetrazoles. For example, the reaction of 1,2‐bis(trifluoromethylazo)ethane with four equivalents of NaN3gave the alkyl‐bridged bis(5‐azido‐1H‐tetrazol‐1‐yl)‐1,2‐dimine, N,N′‐bis(5‐azido‐1H‐tetrazol‐1‐yl)‐1,2‐diiminoethane, in 75 % yield (see scheme).

No flame, no gain: A hypergolic mixture is composed of stable species that readily react/ignite on molecular contact. Both the anion and the cation in an ionic liquid play prominent roles in determining hypergolic properties as well as ignition delay times. With the 2,2‐dialkyltriazanium cation, salts with nitrate, chloride, nitrocyanamide, and dicyanamide anions are hypergolic.

Gefährliche Nähe: Eine hypergole Mischung aus stabilen Verbindungen reagiert rasch oder entzündet sich bei molekularem Kontakt. Anion wie Kation einer ionischen Flüssigkeit haben einen großen Einfluss auf die hypergolen Eigenschaften und die Zündverzögerung. Im Fall des Kations 2,2‐Dialkyltriazanium sind die Nitrat‐, Chlorid‐, Nitrocyanamid‐ und Dicyanamidsalze hypergol.

Insensitive energetic salts: A series of furazan‐functionalized tetrazolate‐based energetic salts (see figure) were synthesized and characterized. All of the salts exhibit excellent thermal stabilities and high positive heats of formation.

High density energetic salts containing nitrogen‐rich cations and the nitranilic anion were readily synthesized in high yield by metathesis reactions of sodium nitranilate 2and an appropriate halide. All of the new compounds were fully characterized by elemental, spectral (IR, 1H, 13C NMR), and thermal (DSC) analyses. The structure of hydrazinium nitranilate (4) was also determined by single‐crystal X‐ray analysis. The high symmetry and oxygen content of the anion give these salts extensive hydrogen bonding capability which further results in the high densities, low water solubilities, and high thermal stabilities (Td> 200 °C) of these compounds. Theoretical performance calculations were carried out by using Gaussian 03 and Cheetah 5.0. The calculated detonation pressures (P) for these new salts fall between 17.5 GPa (10) and 31.7 GPa (4), and the detonation velocities (νD) range between 7022 m s−1(13) and 8638 m s−1(4).

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A family of new fluorinecontaining ionic liquids 3–14 was synthesized in high yield by the reaction of Nalkylpyrrolidine, Nmethylpiperidine and fluorinated 1,3diketones: 1,1,1,5,5,5hexafluoroacetylacetone, 1,1,1trifluoro2,4pentanedione and 4,4,4trifluoro1phenyl1,3butanedione. Their properties, such as the phasetransition temperature, density, and viscosity, were determined. Most of them show relatively low melting points and low viscosities. The influence of fluorinated 1,3diketonate anions and the structural variation in cyclic amine cations on the above physicochemical properties was examined. Xray singlecrystal diffraction analysis of compound 7confirms the proton transfer from 4,4,4trifluoro1phenyl1,3butanedione to Nbutylpyrrolidine. © WileyVCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008

Syntheses of salts with 4,6‐bis(nitroimino)‐1,3,5‐triazinan‐2‐one (DNAM), 3,5‐dinitro‐1,2,4‐cyclopentanetrione (DDCP), 3‐nitroiminotriazolate, and 5‐nitroiminotetrazolate as anions yielded moderately dense nitro‐containing energetic salts that are thermally stable to >200 °C (measured by thermogravimetric analysis). Di(aminoguanidine) 5‐nitroiminotetrazolate (8) crystallizes in the monoclinic space group P2(1)/cwith an essentially planar 5‐nitroiminotetrazolate dianion. Based on experimental and calculated densities, and theoretical calculations carried out by using the Gaussian 03 suite of programs, all of the salts have calculated detonation pressures and velocities that exceed those of 2,4,6‐trinitrotoluene (TNT) and a few have values that approach those of triaminotrinitrobenzene (TATB).

1-Nitroamino-1,2,3-triazole (5) was synthesized and its zwitterionic structure was established using single-crystal X-ray diffraction. The calculated detonation properties for 4-nitroamino-1,2,4-triazole (2) (P= 33.4 GPa, vD= 8793 m/s) and 1-nitroamino-1,2,3-triazole (5) (P= 33.0 GPa, vD= 8743 m/s) are comparable with RDX. A new family of energetic salts 7–21based on either the 1-nitroamino-1,2,3-triazolate or the 4-nitroamino-1,2,4-triazolate anion were prepared and characterized by vibrational spectroscopy (IR), multinuclear NMR spectra, elemental analyses, density, TGA and DSC. The heats of formation (ΔfH°298) and detonation properties for these stable salts were calculated using Gaussian 03 and Cheetah 4.0, respectively. Comparison of the properties of the 1,2,3- and 1,2,4-triazolate salts indicates that while the 1,2,4-derivatives are more stable thermally, the 1,2,3-analogs invariably have higher heats of formation. In contrast to its salts, 1-nitroamino-1,2,3-triazole (5) is extremely shock-sensitive with an impact sensitivty of <1 J. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

The formation of tetraaminopiperazinium salts using water as solvent provides a green, straightforward approach to highly energetic salts that exhibit good thermal stabilities and moderate densities. TheN,N,N′,N′‐tetraaminopiperazinium cation was selected for this study because of its high nitrogen–nitrogen bond content and its high positive heat of formation. Theoretical and empirical calculations on energetic salts based on this nitrogen‐rich cation reveal them to have high positive molar enthalpies of formation, as high as 1034.0 kJ mol−1, supporting the application of these new salts as potential energetic materials.

Energetic salts based on polycyano anions and cations with a high nitrogen content tend to have extensive hydrogen bonding and exhibit heats of formation up to ΔHf=1579.1 kJ mol−1. Based on theoretical calculations, some of the new salts may be considered to be low‐energy monopropellants. One of the salts can be used as a precursor to a carbon nitride.

Lateral metalation and oxidation of 3‐(9′‐anthryl)‐isoxazoles (1), using Davis' oxaziridine (6), produced the desired hydroxylation (2), along with sulfonamide adduct (3), and in the case of the use of butyl lithium as base, butyl addition products (4) and (5). Structures of isoxazole sulfonamides (3a) and (5a), were obtained as the SR/RS‐diastereomer, however, studies indicate that this is a consequence of the crystallization process. Metalation studies with isoxazole (8) demonstrate that hydroxylation (9), can be carried out cleanly, minimizing formation of (10), using camphorsulfonyloxaziridine (7) as an electrophile.

A basic ionic liquid was selected to serve as both the solvent and base for Heck, “copper-free” Sonogashira reactions, and for homocoupling reactions of terminal alkynes. The ionic liquids with tertiary aliphatic amines are effective solvents for these reactions. Under reflux conditions, eight equivalent basic ionic liquids and Pd(OAc)2 in THF or acetone produced palladium colloids with diameters of (2.6 ± 0.3) or (3.7 ± 0.5) nm, respectively. Preliminary results for Knoevenagel condensations are also reported.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

A detailed study of the thermal decomposition of the zwitterionic, ring‐borylated ansa‐chromocene hydrido carbonyl complex [Cr(CO)H{Me4C2(C5H4)[C5H3B(C6F5)3]}] (2) is described. This complex is formed in the reaction between [Cr(CO){Me4C2(C5H4)2}] (1) and B(C6F5)3in toluene at −78 °C. Above −25 °C, 2decomposes to a 50:50 mixture of the low‐spin, 17 e CrIIIcomplexes [Cr(CO){Me4C2(C5H4)[C5H3B(C6F5)3]}] (3 b) and [Cr(CO){Me4C2(C5H4)2}][HB(C6F5)3] (4). Carbon monoxide elimination from 3 bgenerates high‐spin, 15 e [Cr{Me4C2(C5H4)[C5H3B(C6F5)3]}] (3 a), which coordinates two other electron‐donating ligands, such as xylyl isocyanide, PMe3, and PPh2Me to form the low‐spin, 17 e electron complexes 3 c, 3 d, and 3 e, respectively. High‐spin, 15 e [Cr{Me4C2(C5H4)2}][HB(C6F5)3] (5) is generated by heating 3 bin toluene at 100 °C and periodically removing the evolved CO. Efforts to isolate more than a few X‐ray quality crystals of 5were thwarted by its tendency to form an insoluble precipitate (6) with the same molecular formula. Heating the solution of 5at 120 °C results in its partial conversion (ca. 28 %) to 3 a, thereby allowing the formation of 3 ain yields as high as 74 % from the reaction between 1and B(C6F5)3. The X‐ray crystal structures of 3 b–eand 5are described. Cyclic voltammetry measurements on 3 a–ereveal a dramatic reduction in the redox potentials of the complexes relative to their non‐borylated analogues. DFT calculations show that this is due primarily to electrostatic stabilization of the oxidized species by the negatively charged borylate group. EPR and 19F NMR spectroscopy allow 3 ato be distinguished from its Lewis base adducts 3 b–eand reveal the relative affinities of different Lewis bases for the chromium.

2,4,5‐Trinitroimidazolate (TNI) salts with “high‐nitrogen” cations tend to be highly hydrogen bonded and have heats of formation ranging up to 616 kJ mol−1. Density, oxygen balance, and thermostability are enhanced by the presence of TNI. Based on theoretical calculations, all of the new salts are potential propellants.

New energetic nitroformate salts that contain high-nitrogen cations were synthesized by taking advantage of the relatively high acidity of nitroform. All of the new salts have been characterized by elemental, spectral, and thermal analyses. Single-crystal X-ray analysis of 2 shows that it is a co-crystal of a neutral 4-amino-1,2,4-triazole molecule with the 4-amino-1,2,4-triazolium nitroformate ion pair. The presence of the neutral molecule appears to lend stability to the salt. The structure of 3,6-diguanidino-1,2,4,5-tetrazinium nitroformate (10) was also confirmed by single-crystal X-ray analysis. Theoretical performance calculations indicate that these materials have properties which compare favorably with hydrazinium nitroformate, TNT and Tetryl suggesting potential applications as eco-friendly oxidizers. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Neat reactions of 1-(pyrazolylmethyl)imidazole with an excess of alkyl or polyfluoroalkyl halides at 100 °C followed by subsequent metathetical reactions with LiN(SO2CF3)2 or KPF6 at 25 °C gave rise to a series of monoquaternary salts 3a–3k. These salts can be also prepared through treatment of 1-alkylimidazole with 1-(chloromethyl)pyrazole hydrochloride in the presence of base, followed by anion exchange with LiN(SO2CF3)2 or KPF6. Their phase-transition temperature, thermal stability, density and solubility in common solvents have been investigated. Most of the bis(trifluoromethanesulfon)amide salts are room-temperature ionic liquids. The effect of anions and of alkyl substituents bonded to the imidazolium cation on the physicochemical properties was examined. Using 3-butyl-1-(pyrazolylmethyl)imidazolium chloride (2d), the precursor of 3-butyl-1-(pyrazolylmethyl)imidazolium bis(trifluoromethanesulfon)amide (3d), as a reactant, a hemilabile (N-heterocyclic carbene)palladium(II) complex 4 was synthesized through a (carbene)silver(I) transfer reagent. It was characterized by single-crystal X-ray diffraction analysis. The catalytic activity and recyclability of 4 in 3d were preliminarily evaluated by consecutive Heck reactions using different substrates. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

A study of the halogen⋅⋅⋅halogen contacts in organic compounds using ab initio calculations and the results of previously reported crystallographic studies show that these interactions are controlled by electrostatics. These contacts can be represented by the geometric parameters of the CX1⋅⋅⋅X2C moieties (where θ1=CX1⋅⋅⋅X2and θ2=X1⋅⋅⋅X2C; ri=X1⋅⋅⋅X2distance). The distributions of the contacts within the sum of van der Waals radii (rvdW) versus θi(θ1=θ2) show a maximum at θ≈150° for X=Cl, Br, and I. This maximum is not seen in the distribution of F⋅⋅⋅F contacts. These results are in good agreement with our ab initio calculations. The theoretical results show that the position of the maximum depends on three factors: 1) The type of halogen atom, 2) the hybridization of the ipsocarbon atom, and 3) the nature of the other atoms that are bonded to the ipsocarbon atom apart from the halogen atom. Calculations show that the strength of these contacts decreases in the following order: I⋅⋅⋅I>Br⋅⋅⋅Br>Cl⋅⋅⋅Cl. Their relative strengths decrease as a function of the hybridization of the ipsocarbon atom in the following order: sp2>sp>sp3. Attaching an electronegative atom to the carbon atom strengthens the halogen⋅⋅⋅halogen contacts. An electrostatic model is proposed based on two assumptions: 1) The presence of a positive electrostatic end cap on the halogen atom (except for fluorine) and 2) the electronic charge is anisotropically distributed around the halogen atom.

Bicyclic azoles, 2‐methyl‐5‐(imidazol‐1‐yl)‐2H‐tetrazole (1), 2‐methyl‐5‐(1,2,4‐triazol‐1‐yl)‐2H‐tetrazole (4), 1‐methyl‐5‐(imidazol‐1‐yl)‐1H‐tetrazole (7), 1‐methyl‐5‐(1,2,4‐triazol‐1‐yl)‐1H‐tetrazole (10), 1‐methyl‐4‐nitro‐2‐(imidazol‐1‐yl)‐1H‐imidazole (13), and 1‐methyl‐4‐nitro‐2‐(1,2,4‐triazol‐1‐yl)‐1H‐imidazole (16) were prepared. Their thermally stable azolium salts, 3, 6, 9, 12, 15, and 18–21, with densities ranging between 1.519–1.674 g cm−3, were synthesized by quaternization with nitric or perchloric acid or with iodomethane followed by metathesis reactions with silver nitrate and silver perchlorate. The structures of 12 band 21 bwere confirmed by single‐crystal X‐ray analysis. The standard enthalpies of formation for some of the new salts were calculated by using the computationally feasible DFT(B3LYP) and MP2 methods in conjunction with an empirical approach based on densities of salts. The calculated values range from Δ${H{{{\circ}\hfill \atop {\rm f}\hfill}}}$=209.9 (21 a) to 412.3 (12 b) kJ mol−1in which the experimental densities are >1.515 g cm−3.

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Hexamethylenetetrammonium salts, composed of energetic anions 3,5-dinitropyrazolate, 4,5-dinitroimidazolate, 3,5-dinitro-1,2,4-triazolate, 5-nitrotetrazolate, perchlorate, nitrate and azide, were synthesized and characterized. The structure of N-methyl-hexamethylenetetrammonium 3,5-dinitro-1,2,4-triazolate (6) was confirmed by X-ray analysis. The standard enthalpies of formation for the new salts were calculated by using the computationally feasible DFT(B3LYP) and MP2 methods in conjunction with an empirical approach based on the densities of the salts. The calculated values range from ΔHf° = –30.6 (7) to +468.8 kJ·mol–1 (10) where the experimental densities > 1.35 g cm–3. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Supramolecular coordination networks showing redox activity were obtained by reacting ferrocene-based bidentate ligands, 1,1‘-bis(1H-1,2,4-triazol-1-yl)methylferrocene (1) and 1,1‘-bis1H-(2-methyl)imidazol-1-ylmethylferrocene (2), with AgNO3, CdCl2, and ZnCl2using a layering technique. The resulting extended networks display a variety of different conformations, which highlights the flexibility of the bridging ligand:  1·AgNO3(3), 1-D helical array; 12·CdCl2(4), 1-D cross-linked network; 1·ZnCl2(5), 1-D zigzag array; and 2·ZnCl2(6), 1-D zigzag array.

The energetic mono and bridged imidazolium, triazolium and tetrazolium picrates 7–10, 14, and 16, the dipicrates 23, 25, and 26 and the dinitrates 24, and 27 were synthesized by the quaternization of azolium derivatives (1, 2, 13, 15, 19 and 20) with picric acid and nitric acid or by metathesis of the corresponding quaternary salts (3, 6, 21 and 22) with silver picrate or silver nitrate. The structures of 14 and 16 were determined by single-crystal X-ray diffraction analysis confirming quaterization on the triazolium and tetrazolium rings. Their physical and thermodynamic properties were determined. In some cases, the salts are thermally stable to ca. 300 °C and they exhibit densities averaging ca. 1.6 g/cm3. Nearly all have positive heats of formation with the highest calculated value, ΔfHom = 611.6 kJ/mol, found for 3-azido-1,4-dimethyl-1,2,4-triazolium picrate (10). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Energetic salts comprised of substituted 1,2,4-triazolium and tetrazolium cations and 3,5-dinitro-1,2,4-triazolate anion were synthesized and characterized. The structure of 4,5-dimethyl-1-aminotetrazolium 3,5-dinitro-1,2,4-triazolate 16 was confirmed by X-ray analysis. Based on experimentally obtained heats of combustion, these materials have calculated heats of formation ranging from ΔHf° 118 2 to 778 kJ mol−110 with densities >1.5 g cm−3. Salts, 2, 4, 7, 9and 10, fall into the ionic liquid class mp < 100 °C.

Methylenetriphenylphosphorane was coordinated to the boron of phenylborylidene-bridged bis(cyclopentadienyl)- and bis(2-Me,4-Ph-indenyl)zirconium dichloride to form zwitterionic ansa-zirconocene complexes. The cyclopentadienyl complex 2, when activated with MAO, exhibits remarkable polymerization activity that is more than an order of magnitude greater than that of a related amidoborylidene-bridged complex as well as the commercially important precatalyst [Cp′−SiMe2−N−tBu]TiCl2 (Cp′ = C5Me4). The zwitterionic bis(2-Me,4-Ph-indenyl)zirconium dichloride species is isolated as a mixture of rac and meso isomers 4−6. The propylene polymerization efficiency of the isomer mixture activated by MAO is greater than that of a related silylene bridged system at 70 and 85 °C; however, the activity of the zwitterionic system decreased with further increase in temperature. The high level of isotactic triads (63.6%) and pentads (52.4%) in the polypropylene formed by 4−6 indicates that the rac isomer is the most active precatalyst of the mixture. The molecular structures of 2 and the rac bis-indenylzirconium isomer 4 and one of the meso isomers 5 are described. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)