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Herein we present a new viologen-based radical-containing metal-organic framework (RMOF) Gd-IHEP-7, which upon heating in air undergoes a single-crystal-to-single-crystal transformation to generate Gd-IHEP-8. Both RMOFs exhibit excellent air and water stability as a result of favorable radical-radical interactions, and their long-lifetime radicals result in wide spectral absorption in the range 200-2500 nm. Gd-IHEP-7 and Gd-IHEP-8 show excellent activity toward solar-driven nitrogen fixation, with ammonia production rates of 128 and 220 μmol h-1 g-1 , respectively. Experiments and theoretical calculations indicate that both RMOFs have similar nitrogen fixation pathways. The enhanced catalytic efficiency of Gd-IHEP-8 versus Gd-IHEP-7 is attributed to intermediates stabilized by enhanced hydrogen bonding.

ESI of 1:1 mixtures of Th(ClO₄)₄ and ligand TMOGA in acetonitrile resulted in the observation of the TMOGA supported tetracation, Th(L)₃⁴⁺, in the gas phase. Three TMOGA ligands are necessary to stabilize the tetrapositive thorium ion; no Th(L)₂⁴⁺ or Th(L)₄⁴⁺ was observed. Theoretical calculations reveal that the Th(L)₃⁴⁺ complex possesses C₃ symmetry with the thorium center coordinated by nine oxygen atoms from three ligands, which forms a twisted TPP geometry. Actinide compounds with such a geometry feature a nine-coordinate chiral actinide center. The Th-L binding energy and bond orders of Th(L)n⁴⁺ decrease as the coordination number increases, consistent with the trend of concurrently increasing Th-O distances. The Th-O bonding is mainly electrostatic in nature, but the covalent interactions are not negligible. CID of the Th(L)₃⁴⁺ complex mainly resulted in charge reduction to form Th(L)₂(L-86)³⁺oss of neutral TMOGA was not observed. The protic ligand methanol stabilized only tri- and dications of ligated thorium. The intensity of the Th(L)₃⁴⁺ peak was reduced as the percentage of water increased in the Th(ClO₄)₄/TMOGA solution.

Gas-phase addition of a basic ligand to dipositive uranyl coordination complexes comprising diacetone alcohol (DAA) results in water-elimination, which indicates aldol dehydration of DAA to produce mesityl oxide. A novel attribute of the observed gas-phase chemistry is that a ligand exothermically associates to a coordination complex to provide the excitation required to induce chemistry in other ligands, with the added “spectator ligand” remaining intact in the product. Dehydration of DAA was observed for addition of tetrahydrofuran, acetone, and 2-propanol to uranyl complexes [UO2(DAA)2]2+ and [UO2(DAA)(acetone)2]2+. In contrast, [UO2(DAA)2(acetone)]2+ did not exhibit ligand-addition chemistry, which is attributed to a high degree of coordinative saturation at the uranium metal center.

Reported here is a comparison of electron transfer dissociation (ETD) and collision-induced dissociation (CID) of solvent-coordinated dipositive uranyl and plutonyl ions generated by electrospray ionization. Fundamental differences between the ETD and CID processes are apparent, as are differences between the intrinsic chemistries of uranyl and plutonyl. Reduction of both charge and oxidation state, which is inherent in ETD activation of [An(VI) O(2) (CH(3) COCH(3) )(4) ](2+) , [An(VI) O(2) (CH(3) CN)(4) ](2) , [U(VI) O(2) (CH(3) COCH(3) )(5) ](2+) and [U(VI) O(2) (CH(3) CN)(5) ](2+) (An = U or Pu), is accompanied by ligand loss. Resulting low-coordinate uranyl(V) complexes add O(2) , whereas plutonyl(V) complexes do not. In contrast, CID of the same complexes generates predominantly doubly-charged products through loss of coordinating ligands. Singly-charged CID products of [U(VI) O(2) (CH(3) COCH(3) )(4,5) ](2+) , [U(VI) O(2) (CH(3) CN)(4,5) ](2+) and [Pu(VI) O(2) (CH(3) CN)(4) ](2+) retain the hexavalent metal oxidation state with the addition of hydroxide or acetone enolate anion ligands. However, CID of [Pu(VI) O(2) (CH(3) COCH(3) )(4) ](2+) generates monopositive plutonyl(V) complexes, reflecting relatively more facile reduction of Pu(VI) to Pu(V).

The fragmentation chemistry of UO2(N3)Cl2- (obtained by electrospray ionization of MeOH solutions containing UO2Cl2 and NaN3) in the gas phase is investigated using quadrupole ion trap mass spectrometry.

Naked and oxo-ligated actinide (An) monopositive ions were reacted with ethylene oxide, cyclo-C(2)H(4)O (EtO). Along with An = U, Np, Pu and Am, ions of two lanthanide (Ln) elements, Ln = Tb and Tm, were studied for comparison. Metal and metal oxide ions, M(+), MO(+) and MO(2)(+), were generated by laser ablation and immediately reacted with EtO. Unreacted and product ions were detected by time-of-flight mass spectrometry. It was apparent that the overall reaction cross-sections decreased in the order U(+) > or = Np(+) > Pu(+) > Am(+). A primary reaction channel for each studied metal was the formation of MO(+) from M(+), in accord with the expected exothermicity of oxygen abstraction from EtO. For U, Np and Pu, the dioxides were also major products, indicating OAn(+)--O dissociation energies of at least 350 kJ mol(-1), the energy required for O-atom abstraction from EtO. For Am, Tb and Tm, the dioxides were only very minor products, reflecting the stabilities of the trivalent states and resistance to oxidation to higher valence states; the structures/bonding in these MO(2)(+) are intriguing given that the formal pentavalent bonding state is effectively unattainable. It was demonstrated that EtO, unlike more thermochemically favorable but kinetically restricted O-donors, is effective at achieving facile oxidation of actinide metal ions to the monoxide, and to the dioxide if the second O-abstraction reaction is exothermic. Several intriguing minor products were also identified, most of which incorporate metal--oxygen bonding and are attributed to the oxophilicity of the f-block elements; the contrast to the behavior of first-row d-block transition elements is striking in this regard. Particularly noteworthy was the formation of MH(4)(+) (and MOH(4)(+)), evidently via abstraction of all four H atoms from a single C(2)H(4)O molecule; the structures/bonding in these novel 'hydride' species are indeterminate and warrant further attention.

The laser ablation with prompt reaction and detection method was employed to provide a survey of some gas-phase reactions of actinide (M = U, Np, Pu and Am) and lanthanide (M = Tb and Tm) ions, M(+) and MO(1,2)(+), with alcohols, thiols and ethers. Particular attention was given the changing behavior in progressing across the actinide series beyond uranium. With alcohols, ROH, major products included hydroxides and alkoxides, M(OH)(1,2)(+), M(OR)(1,2)(+), MO(OH)(+) and MO(OR)(+); these products are presumed to have resulted from RObH and RbOH bond cleavage by ablated M(+) and MO(+). The abundance distributions for these elementary products reflected the decrease in stabilities of high oxidation states between U and Am. Other alcohol reaction products included electrostatically bonded adducts, such as HObNp(+)ellipsisC(3)H(7)OH, sigma-bonded organometallics, such as HObPu(+)bC(2)H(5), and pi-bonded organometallics, such as Np(+)beta(3)-?C(3)H(5)?. In view of the inability of actinide and lanthanide ions to dehydrogenate alkanes, the exhibition of dehydrogenation of the alkyl chain of alcohols, as in HO-Pu(+)-C(3)H(5)O from propanol, suggests a non-insertion mechanism involving complexation of the reactant ion to the alcohol. Whereas O abstraction products from ROH were obfuscated by directly ablated MO(1,2)(+), S abstraction from thiols, RSH, was manifested by the appearance of MS(+), MS(2)(+) and MOS(+). In analogy with OH abstraction from alcohols to produce metal hydroxides, SH abstraction from thiols resulted in hydrosulfides, including Am(SH)(+) and Np(SH)(2)(+). In addition to several other reaction pathways with the thiol reagents, products presumed to be thiolates included Am(C(3)H(7)S)(+) and NpO(C(3)H(7)S) from propanethiol. A primary product of reaction with dimethyl ether were methoxides resulting from C--O bond cleavage, including Am(OCH(3))(+) and Np(OCH(3))(2)(+). With methyl vinyl ether, more complex pathways were exhibited, most of which corresponded to the elimination of stable organic molecules. An ancillary result was the discovery of several small oxide clusters, Am(2)O(n)(+), Np(2)O(n)(+) and AmNpO(n)(+). The compositions and abundance distributions of these clusters reflected the propensity of Np to exist in higher oxidation states than Am; the dominant binary clusters were Am(2)O(2)(+) and Np(2)O(3)(+).

Ibutilide fumarate is a class III antiarrhythmic agent in phase III clinical trials. Due to rapid hepatic metabolism, ibutilide has a low oral bioavailability (< 10%). To assess alternate routes of administration, we performed repeated studies of the electrophysiologic effects of sublingual ibutilide (0.03, 0.1, and 0.3 mg/kg; 0.07, 0.2, and 0.7 mmol/kg) in pentobarbital anesthetized dogs. Peak significant increases in QTc interval, ventricular effective refractory period (VERP), and right ventricular monophasic action potential duration (MAPD90) were achieved 30 min following 0.1 or 0.3 mg/kg (0.2 and 0.7 mmol/kg) ibutilide and were coincident with peak plasma ibutilide levels. The duration of significant effects ranged from 2 to 5 h. Peak effects were: QTc + 121 msec, MAPD90 + 71 msec, and VERP + 53 msec. The 0.3 mg/kg (0.7 mmol) dose significantly decreased heart rate 10 min post dosage through 5 h. The 0.03 mg/kg (0.07 mmol) dose increased MAPD90 at 1 to 2 h but was otherwise ineffective. The plasma half life of ibutilide was 2.8 h, with a 72% bioavailability relative to an equivalent intravenous dose. Based on the electrophysiologic results, we chose to test the 0.1 mg/kg (0.2 mmol) sublingual ibutilide dose for termination of sustained atrial flutter in anesthetized dogs with y-shaped right atrial incisions. The administration of 0.1 mg/kg (0.2 mmol) sublingual ibutilide during sustained atrial flutter resulted in termination of atrial flutter in all cases (n = 4) after a mean time interval of 11.4 ± 0.8 min. Termination of atrial flutter was associated with ibutilide plasma levels of 19.6 ± 6.3 ng/ml, and 30 and 18 msec increases in atrial and ventricular effective refractory periods. Atrial flutter could be reinduced in 2 dogs, on at 3 h and one at 4 h post ibutilide administration. The ability to reinduce atrial flutter was associated with a reduction in ibutilide plasma levels to 2.3 ± 0.7 ng/ml. We conclude that sublingual ibutilide is rapidly absorbed and produces significant electrophysiologic and antiarrhythmic effects, and is a potential alternative to intravenous and oral therapy. ©1995 Wiley-Liss, Inc.

The electrophysiologic and antiarrhythmic effects of artilide were evaluated in dogs 24 h after myocardial infarction. Artilide (0.1 to 3.0 mg/kg or 0.2 to 7.0 μuM/kg iv) prevented programmed stimulation induced ventricular arrhythmias in 9 out of 9 dogs that had demonstrated inducibe ventricular arrhythmias prior to treatment. This antiarrhythmic action was associated with significant increases in ventricular refractoriness and monophasic action potential duration. Lower doses of artilide tended to reduce the incidence of spontaneous ventricular arrhythmias but these effects were not significant. These results are consistent with the concept that spontaneous and pacing induced ventricular arrhythmias result from different mechanisms, and that class III anti-arrhythmic agents are more effective in suppressing induced ventricular tachycardia due to reentry than spontaneous arrhythmias which result from nonreentrant mechanisms. © 1993 wiley-Liss, Inc.

The compound, NpNi5, was prepared and its crystal properties studied by means of powder X-ray diffraction. The existence and properties of this compound were pursued as they are important in developing further the Np-Ni phase diagram. The crystal symmetry of this material was determined to be hexagonal and have the D2d CaCu5 structure type, which is also observed for ThNi5 and PuNi5. The lattice parameters of NpNi5 were calculated to be: ao=0.4859±0.0002 and co=0.3991±0.0003 nm. Based on these lattice parameters and the apparent radius of Np in the NpNi5 compound, it appears that Np can be considered as being tetravalent, which has certain bonding implications. The apparent valence states for Np and other actinides in these actinide-Ni5 compounds are discussed, as well as the variation in cell volumes noted for the known actinide- and lanthanide-Ni5 compounds.

The plutonium–oxygen system is fundamentally and technologically important. The primary goal of the present study was to prepare and carry out initial chemical studies on gas-phase plutonium oxide cluster ions, which would contribute to the general understanding of PuOx chemistry. In this effort, several plutonium oxide, oxide-hydroxide and hydroxide cluster ions, PuxOy(OH)z+, were synthesized by pulsed laser ablation of hydrated plutonium oxalate in vacuum. Cerium was studied for comparison, and a chemically less diversified oxide cluster system was observed. The large variety of PuxOy(OH)z+ compositions found is attributed to the accessibility of multiple oxidation states for Pu, and the results demonstrate the feasibility of preparing clusters with diverse stoichiometries and variable plutonium oxidation states. These clusters may be studied by various gas-phase techniques to illuminate the behavior of plutonium as a function of key variables, such as oxidation state, structure/coordination and bonding. In addition, some gas-phase reaction studies were carried out and at least one significant cluster reaction product with dimethylether was identified. This result demonstrates the desirability of studying plutonium cluster chemistry in ion traps where longer residence times, and more ion–molecule collisions will result in greater reaction efficiencies. The largest primary oxide cluster identified here comprised six Pu atoms, but two distinctive ‘magic number’ clusters were also produced, which incorporated 16 and 18 Pu atoms, respectively. These ‘magic number’ clusters suggest that special stabilities obtain for these species and that it may be possible to prepare plutonium oxide ‘nanocrystals’ in the gas phase for examination by techniques complementary to those applicable to bulk materials. The plutonium cluster compositions and abundances observed in this work are discussed in the context of the oxidation states, structures, and bonding exhibited by plutonium.

Recent years have witnessed an increased level of activity in the study of gas-phase chemistry of bare and oxo-ligated actinide ions. The intent of this report is to summarize some key accomplishments in gas-phase actinide ion chemistry. Early work on thorium and uranium is described along with an account of recent results for the more radioactive synthetic actinides. Reactions of bare and oxo-ligated actinide ions with hydrocarbons have been a central focus of study and reveal important insights into actinide chemistry. Also briefly summarized are a few representative reactions with other types of substrates. Some results for the homologous lanthanide elements are included for comparison. Other types of reactions are also considered with an emphasis on the unique behavior of the actinides. Future prospects in the field of gas-phase actinide ion chemistry are discussed.

Fundamental aspects of the chemical and physical properties of atomic and molecular actinide ions and neutrals are being examined by Fourier transform ion cyclotron resonance mass spectrometry (FTICR/MS). To date, gas-phase reactivity studies of bare and ligated An+ and An2+ ions, where An = Th, Pa, U, Np, Pu, Am, and Cm, with oxidants and with hydrocarbons have been performed. Among the information that has been deduced from these studies are thermodynamic properties of neutral and ionic actinide oxide molecules and the role of the 5f electrons in actinide chemistry. Parallel theoretical studies of selected actinide molecular ions have also been carried out to substantiate the interpretation of the experimental observations.

A variety of in vivo models have been used to detect and develop novel antiarrhythmic/antifibrillatory agents. However, most of these models primarily have identified the class I agents that block sodium ion currents during the upstroke of the cardiac action potential. Since we are interested in identifying agents with a class III electrophysiologic action, i.e. delayed repolarization of the cardiac action potential, we have focused our drug discovery process on a specific, somewhat uncommon in vivo canine model. These studies have demonstrated that class I agents such as encainide, disopyramide, or U58797, a novel benzamide, are clearly identified in the ouabain-toxic dog or the postinfarction (24–48 hr) conscious dog. In contrast, class III agents such as clofilium sotalol are identified in an acute canine model of coronary artery occlusion and reperfusion. This occlusion-reperfusion model allows us to further identify the antiarrhythmic and antifibrillatroy actions of novel class III agents.

Recent theoretical calculations have shown that Ir should behave as a chemical analogue to N, with the result that IrUO{sup +}, like known NUO{sup +}, is predicted to be a stable species isoelectronic with UO{sub 2}{sup 2+}, the uranyl dication. The target heterometallic analogue to uranyl has now been prepared by direct laser desorption/ionization of a U/Ir alloy, and by oxidation of UIr{sup +} with N{sub 2}O and C{sub 2}H{sub 4}O. Properties of UIr{sup +}, UPt{sup +}, and UAu{sup +} bimetallic ions have been studied. They demonstrate direct actinide-transition metal bonding, and support the concept of autogenic isolobality.

The relative vapor pressures of each component of the ternary mixed fluoride system (Pr1/3Pm1/3Sm1/3)F3 are determined simultaneously over the temp. range 1100-1280 °C by using Knudsen effusion-mass spectrometry.

243AmBi and 248CmBi have been prepared from the elements (vacuum, excess Bi; AmBi: 700 °C, 16 h; CmBi: 400-600 °C, several h).