脯氨酸类N-酰胺衍生物的核磁共振研究

脯氨酸类衍生物结构独特,鲜有报道利用核磁共振（nuclear magnetic resonance,NMR）技术对氨基酸的手性进行鉴别.利用多种NMR技术:1H NMR、1H-1H同核位移相关谱（1H-1H COSY）、1H-1H质子全相关谱（1H-1H TOCSY）、1H-1H核Overhauser效应谱（1H-1H NOESY）、13C NMR、无畸变的极化转移增强法（DEPT135°）、1H-13C检出1H的异核单量子相干（1H-13C HSQC）和1H-13C检出1H的异核多键相关（1H-13C HMBC）,对脯氨酸类N-酰胺衍生物两种构象异构体的1H和13C NMR进行了全归属,确定了室温下在二甲基亚砜（DMSO）中L型和D型的顺反异构体以相同的比例同时存在.     

Theoretical study of electronic structure of rhodium mononitride and interpretation of experimental spectra

Potential energy curves of 22 electronic states of RhN have been calculated by the complete active space second‐order perturbation theory method. The X¹Σ₀⁺ is assigned as the ground state, and the first excited state a³Π₀+ is 978 cm^?1 higher. The ¹Δ(I) and B¹Σ⁺ states are located at 9521 and 13,046 cm^?1 above the ground state, respectively. The B¹Σ⁺ state should be the excited state located 12,300 cm^?1 above the ground state in the experimental study. Moreover, two excited states, C¹Π and b³Σ⁺, are found 14,963 and 15,082 cm^?1 above the X¹Σ⁺ state, respectively. The transition C¹Π₁–X¹Σ₀⁺ may contribute to the experimentally observed bands headed at 15,071 cm^?1. There are two excited states, D¹Δ and E¹Σ⁺, situate at 20,715 and 23,145 cm^?1 above the X¹Σ⁺ state. The visible bands near 20,000 cm^?1 could be generated by the electronic transitions D¹Δ₂–a³Π₁ and E¹Σ⁺₀–X¹Σ⁺₀ because of the spin–orbit coupling effect. © 2013 Wiley Periodicals, Inc.     

O‐loss photodissociation of the OCS+ ion in the low‐lying electronic states studied using multiconfiguration second‐order perturbation theory

The CASPT2 potential energy curves (PECs) for O‐loss dissociation from the X²Π, A²Π, B²Σ⁺, C²Σ⁺, 1⁴Σ^?, 1²Σ^?, and 1⁴Π states of the OCS⁺ ion were calculated. The PEC calculations indicate that X²Π, 1⁴Σ^?, 1²Σ^?, and 1⁴Π correlate with CS⁺(X²Σ⁺) + O(³P_g); A²Π and B²Σ⁺ correlate with CS⁺(A²Π) + O(³P_g); and C²Σ⁺ probably correlates with CS⁺(X²Σ⁺) + O(¹D_g). The CASSCF minimum energy crossing point (MECP) calculations were performed for the C²Σ⁺/1⁴Σ^?, C²Σ⁺/1⁴Π, A²Π/1⁴Σ^?, A²Π/1²Σ^?, A²Π/1⁴Π, and B²Σ⁺/1²Σ^? state pairs and the spin‐obit couplings were calculated at the located MECPs. A conical intersection point between the B²Σ⁺ and C²Σ⁺ potential energy surfaces was found at the CASSCF level. Based on our calculations, seven O‐loss predissociation processes of the C²Σ⁺ state are suggested and an appearance potential value of 7.13 eV for the CS⁺ + O product group is predicted. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Ground state for two‐electron and electron‐muon three‐body atomic systems

In this article, the angular correlated configuration interaction method previously introduced by some of the authors is extended to three‐body atomic systems with general masses. A recently proposed angularly correlated basis set is used to construct ground state wave functions which: (i) satisfy exactly Kato cusp conditions at the two‐body coalescence points; (ii) have only linear coefficients; and (iii) show a fast convergency rate for the energy. The efficiency of the construction is illustrated by the study of the negatively charged hydrogen‐like systems (^∞H^?, T^?, D^?, ¹H^?, and Mu^?), neutral helium‐like systems (e^?e^{? ∞}He⁺²,e^?e^{? 4}He⁺², e^?e^{? 3}He⁺², e^?μ^{? ∞}He⁺², e^?μ ^?4He⁺², and e^?μ^{? 3}He⁺²), and positively charged lithium‐like systems (e^?e^{? ∞}Li⁺³, e^?e^{? 7}Li⁺³, e^?e^{? 6}Li⁺³, e^?μ^{? ∞}Li⁺³, e^?μ^{? 7}Li⁺³, and e^?μ^{? 6}Li⁺³). The ground state energies and other mean values are compared with those given in the literature, when available. Wave functions with a moderate number of (20 maximum) linear coefficients are given explicitly; they are sufficiently simple and accurate to be used in practical calculations of atomic collision in which multidimensional integrations are involved. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Synthesis of exo-3-amino-10-hydroxy-hexacyclo[10.2.1.0.0.0.0]pentadecane-5,7-diene-endo-3-carboxyclic acid and endo-3-amino-10-hydroxy-hexacyclo[10.2.1.0.0.0.0]pentadecane-5,7-diene-exo-3-carboxylic acid

Treatment of hexacyclo[7.4.2.0^1,9.0^3,7.0^4,14.0^6,15]pentadecane-10,12-diene-2,8-dione with aqueous sodium cyanide produced 2,8-dihydroxy-hexacyclo[7.4.2.0^1,9.0^3,7.0^4,14.0^6,15]pentadecane-10,12-diene-2,8-lactam and with sodium cyanide, ammonium chloride and ammonium hydroxide, 2-amino-8-hydroxy-hexacyclo [7.4.2.0^1,9.0^3,7.0^4,14.0^6,15]pentadecane-10,12-diene-2,8-lactam was obtained. 10-Hydroxy-hexacyclo [10.2.1.0^2,11.0^4,10.0^4,14.0^9,13]pentadecane-5,7-diene-3-one was converted into the corresponding aminonitrile and hexacyclo[10.2.1.0^2,11.0^4,10.0^4,14.0^9,13]pentadecane-5,7-diene-10-hydroxy-3-spiro-5′-hydantoin. Treatment of the latter with barium hydroxide produced exo-3-amino-10-hydroxy-hexacyclo [10.2.1.0^2,11.0^4,10.0^4,14.0^9,13]pentadecane-5,7-diene-endo-3-carboxylic acid. The isomeric endo-3-amino-10-hydroxy-hexacyclo[10.2.1.0^2,11.0^4,10.0^4,14.0^9,13]pentadecane-5,7-diene-exo-3-carboxylic acid was obtained from 3-cyano-3-ureido-hexacyclo[10.2.1.0^2,11.0^4,10.0^4,14.0^9,13]pentadecane-5,7-diene-10-ol.     

Synthesis and evaluation of two novel rhodamine-based fluorescence probes for specific recognition of Fec+ ion

Two low cytotoxic fluorescence probes Rb1 and Rb2 detecting Fe³⁺ were synthesized and evaluated. Rb1 and Rb2 exhibited an excellent selectivity to Fe³⁺, which was not disturbed by Ag⁺, Li⁺, K⁺, Na⁺, NH₄⁺, Fe²⁺, Pb²⁺, Ba²⁺, Cd²⁺, Ni²⁺, Co²⁺, Mn²⁺, Zn²⁺, Mg²⁺, Hg²⁺, Ca²⁺, Cu²⁺, Ce³⁺, AcO^?, Br^?, Cl^?, HPO₄^2?, HSO₃^?, I^?, NO₃^?, S₂O₃^2?, SO₃^2? and SO₄^2? ions. The detection limits were 1.87 × 10^?7 M for Rb1 and 5.60 × 10^?7 M for Rb2, respectively. 1:1 stoichiometry and 1:2 stoichiometry were the most likely recognition mode of Rb1 or Rb2 towards Fe³⁺, and the corresponding OFF–ON fluorescence mechanisms of Rb1 and Rb2 were proposed.     

Physico-chemical studies on the chelation behaviour of biologically active 2-hydroxy-1-naphthaldehyde semicarbazone (HNAS) with some lanthanons

Summary The chelation behaviour of the complexes of La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Y³⁺, Tb³⁺, Dy³⁺, Ho³⁺ with biologically active 2-Hydroxy-1-naphthaldehyde semicarbazone (HNAS) has been studied potentiometrically in 75% (v/v) dioxane-water medium at various ionic strengths. The method of Bjerrum and Calvin, as modified by Irving and Rossotti has been used to find out the values of n andpL. The formation constants of metal chelates and the values ofS _min have been calculated. The order of formation constants of chelates was found to be: La³⁺3+3+3+3+3+3+3+3+3+3+.

---

Physikochemische Untersuchungen zur Komplexierung von biologisch aktivem 2-Hydroxy-1-naphthaldehyd-Semicarbazon (HNAS) mit Lanthanoiden

Zusammenfassung Das Chelierungsverhalten von La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Y³⁺, Tb³⁺, Dy³⁺ und Ho³⁺ mit 2-Hydroxy-1-naphthaldehydsemicarbazon (HNAS) wurde potentiometrisch in 75% (v/v) Dioxan-Wasser bei verschiedenen Ionenstärken untersucht. Die Werte für n undpL wurden nach der Methode von Bjerrum und Calvin in der Modifikation von Irving und Rossotti bestimmt. Die Komplexbildungskonstanten der Metallchelate und die WerteS _min wurden ermittelt. Die Reihung der Komplexbildungskonstanten war La³⁺3+3+3+3+3+3+3+3+33+.

     

A Nitron-Polyvinylbenzyl Chloride Polymer to Selectively Remove Oxidizing Anions from Non-Oxidizing Anions. Removal of NO3 − and NO2 − from Polluted Waters

Abstract

A nitron-polyvinylbenzyl chloride polymer was found to have a strong preference for oxidizing anions such as NO₃ ^?, NO₂ ^?, ReO₄ ^?, MnO₄ ^?, C1O₄ ^?, C1O₃ ^?, and Cr₂O₇ ⁼ but not for the non-oxidizing anions SO₄ ⁼, HSO₄ ^?, H₂PO₄ ⁼, HPO₄ ⁼, PO₄ ⁼, OH^?, CO₃ ⁼, HCO₃ ^?, F^?, C1^?, and Br^?.     

Photodissociation Spectra of OCS+ via B2∑+←X2∏ Transitions

In the wavelength range of 231-275 nm, we have studied the mass-resolved dissociation spectra of OCS⁺ via B²∑⁺←X²∏_3/2(000) and B²∑⁺←X²∏_1/2(000, 001) transitions by preparing OCS⁺ ions in the well-defined spin-orbit states. The spectroscopic constants ofυ1(CS stretch)=828.9 (810.4) cm^-1, υ2(bend)=491.3 cm^-1 and υ3(CO stretch)=1887.2 cm^-1 for OCS⁺(B²∑⁺) are deduced. The observed dependence of the υ2(bend) mode excitation of B²∑⁺ on the spin-orbit splitting of X²∏(Ω=1/2, 3/2) in the B²∑⁺←X²∏ transition can be attributed to the K coupling between the (000)²∏_1/2 and (010)²∑⁺_1/2 vibronic levels of X²∏ state, which makes the B²∑⁺(010)←X²∏_1/2(000) transition possible.     

Zum Einfluß der PR3‐Liganden auf Bildung und Eigenschaften der Phosphinophosphiniden‐Komplexe [{η2‐tBu2P–P}Pt(PR3)2] und [{η2‐tBu2P1–P2}Pt(P3R3)(P4R′3)]

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes XXI The Influence of the PR₃ Ligands on Formation and Properties of the Phosphinophosphinidene Complexes [{η²‐^tBu₂P–P}Pt(PR₃)₂] and [{η²‐^tBu₂P¹–P²}Pt(P³R₃)(P⁴R′₃)] (R₃P)₂PtCl₂ and C₂H₄ yield the compounds [{η²‐C₂H₄}Pt(PR₃)₂] (PR₃ = PMe₃, PEt₃, PPhEt₂, PPh₂Et, PPh₂Me, PPh₂ⁱPr, PPh₂^tBu and P(p‐Tol)₃); which react with ^tBu₂P–P=PMe^tBu₂ to give the phosphinophosphinidene complexes [{η²‐^tBu₂P–P}Pt(PMe₃)₂], [{η²‐^tBu₂P–P}Pt(PEt₃)₂], [{η²‐^tBu₂P–P}Pt(PPhEt₂)₂], [{η²‐^tBu₂P–P}Pt(PPh₂Et)₂], [{η²‐^tBu₂P–P}Pt(PPh₂Me)₂], [{η²‐^tBu₂P–P}Pt(PPh₂ⁱPr], [{η²‐^tBu₂P–P}Pt(PPh₂^tBu)₂] and [{η²‐^tBu₂P–P}Pt(P(p‐Tol)₃)₂]. [{η²‐^tBu₂P–P}Pt(PPh₃)₂] reacts with PMe₃ and PEt₃ as well as with ^tBu₂PMe, PⁱPr₃ and P(c‐Hex)₃ by substituting one PPh₃ ligand to give [{η²‐^tBu₂P¹–P²}Pt(P³Me₃)(P⁴Ph₃)], [{η²‐^tBu₂P¹–P²}Pt(P³Ph₃)(P⁴Me₃)], [{η²‐^tBu₂P¹–P²}Pt(P³Et₃)(P⁴Ph₃)], [{η²‐^tBu₂P¹–P²}Pt(P³Me^tBu₂)(P⁴Ph₃)], [{η²‐^tBu₂P¹–P²}Pt(P³ⁱPr₃)(P⁴Ph₃)] and [{η²‐^tBu₂P¹–P²}Pt(P³(c‐Hex)₃)(P⁴Ph₃)]. With ^tBu₂PMe, [{η²‐^tBu₂P–P}Pt(P(p‐Tol)₃)₂] forms [{η²‐^tBu₂P¹–P²}Pt(P³Me^tBu₂)(P⁴(p‐Tol)₃)]. The NMR data of the compounds are given and discussed with respect to the influence of the PR₃ ligands.     

Dianionic Titanyl and Vanadyl (Cation+)2[MIVO(Pc4−)]2− Phthalocyanine Salts Containing Pc4− Macrocycles

In this study, the titanyl and vanadyl phthalocyanine (Pc) salts (Bu₄N⁺)₂[M^IVO(Pc^4?)]^2? (M=Ti, V) and (Bu₃MeP⁺)₂[M^IVO(Pc^4?)]^2? (M=Ti, V) with [M^IVO(Pc^4?)]^2? dianions were synthesized and characterized. Reduction of M^IVO(Pc^2?) carried out with an excess of sodium fluorenone ketyl in the presence of Bu₄N⁺ or Bu₃MeP⁺ is exclusive to the phthalocyanine centers, forming Pc^4? species. During reduction, the metal +4 charge did not change, implying that Pc is an non‐innocent ligand. The Pc negative charge increase caused the C?N(pyr) bonds to elongate and the C?N(imine) bonds to alternate, thus increasing the distortion of Pc. Jahn–Teller effects are significant in the [eg(π*)]² dianion ground state and can additionally distort the Pc macrocycles. Blueshifts of the Soret and Q‐bands were observed in the UV/Vis/NIR when M^IVO(Pc^2?) was reduced to [M^IVO(Pc ^{. 3?})] ^{. ?} and [M^IVO(Pc^4?)]^2?. From magnetic measurements, [Ti^IVO(Pc^4?)]^2? was found to be diamagnetic and (Bu₄N⁺)₂[V^IVO(Pc^4?)]^2? and (Bu₃MeP⁺)₂[V^IVO(Pc^4?)]^2? were found to have magnetic moments of 1.72–1.78 μ_B corresponding to an S=1/2 spin state owing to V^IV electron spin. As a result, two latter salts show EPR signals with V^IV hyperfine coupling.     

Analytical methods to determine Po and Pb in marine samples

This paper describes the methods of sampling, preconcentration, chemical separation and final count of ²¹⁰Po and ²¹⁰Pb present in different marine matrices to determine their background levels in a marine ecosystem. Complex, time consuming and selective radioanalytical methods have been used to prepare final clear sources for alpha spectrometry and beta count; in fact, gamma spectrometry, a method direct and non destructive, cannot be taken into account because the ²¹⁰Pb activity is very low which does not allow to carry out sufficiently accurate measurements and ²¹⁰Po is not a gamma emitter but it emits only alpha particle at 5.40 MeV. The results of ²¹⁰Po and ²¹⁰Pb activity concentrations obtained in different marine samples collected in the first two campaigns are still very few to discuss about the ²¹⁰Po and ²¹⁰Pb behavior in marine environment.     

1H, 13C and 15N NMR chemical shifts of substituted pyrazolo[1,5‐a]pyrimidines

¹H, ¹³C and ¹⁵N NMR chemical shifts of 10 substituted pyrazolo[1,5‐a]pyrimidines were assigned based on DQF ¹H, ¹H COSY, PFG ¹H, ¹³C HMQC and PFG ¹H,X (X = ¹³C and ¹⁵N) HMBC experiments and on literature data. Copyright © 2002 John Wiley & Sons, Ltd.     

Multielement (H,C, N,O, S) stable isotope characteristics of lamb meat from different Italian regions

The study focuses on the ²H/H, ¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O and ³⁴S/³²S values of defatted dry matter (DFDM) and on the ²H/H, ¹³C/¹²C and ¹⁸O/¹⁶O values of the fat fraction of meat samples from various lamb types reared in seven Italian regions, following different feeding regimes (forage, concentrate, milk). The ¹³C/¹²C (r = 0.922), ²H/H (r = 0.577) and ¹⁸O/¹⁶O (r = 0.449) values of fat and DFDM are significantly correlated, the fat values being significantly lower for C and H and higher for O than for DFDM values and the differences between the two fractions not being constant for different lamb types. The feeding regime significantly affected the ¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O and ²H/H of fat. The DFDM ²H/H, and ¹⁸O/¹⁶O values, excluding an outlier, are significantly correlated with the corresponding values in meteoric waters, thus allowing us to trace the variability of geoclimatic factors. ¹⁵N/¹⁴N is influenced by pedoclimatic conditions, whereas ³⁴S/³²S is influenced by the sea spray effect and the surface geology of the provenance area. By applying stepwise linear discriminant analysis only the ²H/H of fat was found not to be significant and 97.7% of the samples were correctly assigned to the lamb type and more than 90% cross‐validated. With the feeding regime, 97.7% of the samples were both correctly assigned and cross‐validated using a predictive model including ¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O, ³⁴S/³²S of DFDM and ¹⁸O/¹⁶O of fat. Copyright © 2009 John Wiley & Sons, Ltd.     

210Pb and 210Po concentrations in the Venice lagoon ecosystem (Italy) and the potential radiological impact to the local public and environment

In order to evaluate the possible radiological impact to the local public and environment from a phosphogypsum stockpile, ²¹⁰Po and ²¹⁰Pb concentrations in river water, lagoon water, suspended matter, superficial sediment, algae and bivalves samples collected in Venice lagoon area have been investigated. The results show that the mean ²¹⁰Po and ²¹⁰Pb concentrations in river water are 1.42±0.36 mBq^.l^-1 and 1.46±0.39 mBq^.l^-1 with a mean ²¹⁰Po/²¹⁰Pb ratio of 0.98±0.17 and about 60% of them are associated with the particulate; ²¹⁰Po and ²¹⁰Pb contribution from the phosphogypsum stockpile to the river water is negligible. Higher ²¹⁰Po (2.61-5.67 mBq^.l^-1) and ²¹⁰Pb (1.31-3.62 mBq^.l^-1) concentrations in the lagoon waters have been observed if compared with the literature values. About 60% of ²¹⁰Po and ²¹⁰Pb are found in the soluble form with a mean ²¹⁰Po/²¹⁰Pb ratio of 1.79±1.47. ²¹⁰Po and ²¹⁰Pb concentrations in 28 out 37 sediment samples ranged from 26 to 45 Bq^.kg^-1 (dry weight), only 9 sediments with ²¹⁰Po and ²¹⁰Pb concentrations greater than 45 Bq^.kg^-1 are found and most of them are located 1-4 km near the phosphogypsum stockpile. The elevated ²¹⁰Po and ²¹⁰Pb concentrations in the sediments may be due to the contamination from the phosphogypsum stockpile. The mean ²¹⁰Po/²¹⁰Pb ratio (0.986±0.049) in the sediments shows that ²¹⁰Po and ²¹⁰Pb exist in nearly secular equilibrium. ²¹⁰Po and ²¹⁰Pb concentrations in algae vary with different species. The mean ²¹⁰Po and ²¹⁰Pb concentrations in Gracilaria compress and Ulva laetevirens which show a similar behavior, are 3.18±1.23 Bq^.kg^-1 and 2.42±1.26 Bq^.kg^-1 (fresh weight), respectively, with a mean ²¹⁰Po/²¹⁰Pb ratio of 1.45±0.34. The mean concentration factors with respect to the filtered water are 1096±424 for ²¹⁰Po and 1299±680 for ²¹⁰Pb. The mean ²¹⁰Po and ²¹⁰Pb concentrations in the soft part of Mytilus edulis are 23.2±9.7 Bq^.kg^-1 and 0.537±0.203 Bq^.kg^-1 (fresh weight), respectively, with a mean ²¹⁰Po/²¹⁰Pb ratio of 43.6±10.0. The mean concentration factors with respect to the filtered water are 8006±3351 for ²¹⁰Po and 290±109 for ²¹⁰Pb, showing a very high accumulation effect for ²¹⁰Po. The accumulation behaviors of Cerastoderma glaucum and Tapes philippinarum for ²¹⁰Po are similar to Mytilus edulis, but that for ²¹⁰Pb seems less effective, corresponding to a relatively higher ²¹⁰Po/²¹⁰Pb ratio. The estimated committed effective doses from ²¹⁰Po for the individual local public through ingestion of bivalves are in the range of 0.050-0.231 mSv^.y^-1.     

A Turn‐On Fluorescence Chemosensor for Cyanide in Aqueous Media Based on a Nucleophilic Addition Reaction

We synthesized a new cyanide (CN ⁻) chemosensor CX based on a nucleophilic addition reaction prompted by cyanide ion, which could be used for highly selective and sensitive fluorescence turn‐on detection of cyanide in aqueous media. The CX showed selective fluorescence recognition for CN ⁻, the miscellaneous competitive anions (F⁻, Cl⁻, Br⁻, I⁻, AcO ⁻, H₂PO₄⁻, HSO₄⁻, ClO₄⁻, S^{2 −}, PO₄³⁻, CO₃²⁻ and SCN ⁻) did not lead to any significant interference. The detection limit of the sensor towards CN ⁻ is 1.15 × 10⁻⁷ mol•L⁻¹. The sensor has been successfully applied to estimate the cyanide ion in seeds of cherries. Test strips based on CX were fabricated, which could be used as a convenient and efficient CN ⁻ test kit to detect CN ⁻ in aqueous solution for “in‐the‐field” measurement.     

The Electron Transfer Series [MoIII(bpy)3]n (n=3+, 2+, 1+, 0, 1−), and the Dinuclear Species [{MoIIICl(Mebpy)2}2(μ2‐O)]Cl2 and [{MoIV(tpy.)2}2(μ2‐MoO4)](PF6)2⋅4 MeCN

The electronic structures of the five members of the electron transfer series [Mo(bpy)₃]ⁿ (n=3+, 2+, 1+, 0, 1?) are determined through a combination of techniques: electro‐ and magnetochemistry, UV/Vis and EPR spectroscopies, and X‐ray crystallography. The mono‐ and dication are prepared and isolated as PF₆ salts for the first time. It is shown that all species contain a central Mo^III ion (4d³). The successive one‐electron reductions/oxidations within the series are all ligand‐based, involving neutral (bpy⁰), the π‐radical anion (bpy^.)^1?, and the diamagnetic dianion (bpy^2?)^2?: [Mo^III(bpy⁰)₃]³⁺ (S=3/2), [Mo^III(bpy^.)(bpy⁰)₂]²⁺ (S=1), [Mo^III(bpy^.)₂(bpy⁰)]¹⁺ (S=1/2), [Mo^III(bpy^.)₃] (S=0), and [Mo^III(bpy^.)₂(bpy^2?)]^1? (S=1/2). The previously described diamagnetic dication “[Mo^II(bpy⁰)₃](BF₄)₂” is proposed to be a diamagnetic dinuclear species [{Mo(bpy)₃}₂(μ₂‐O)](BF₄)₄. Two new polynuclear complexes are prepared and structurally characterized: [{Mo^IIICl(^Mebpy⁰)₂}₂(μ₂‐O)]Cl₂ and [{Mo^IV(tpy^.)₂}₂(μ₂‐Mo^VIO₄)](PF₆)₂?4 MeCN.     

N2 Activation in NiI–NN–NiI Units: The Influence of Alkali Metal Cations and CO Reactivity

After single electron reduction of the dinitrogen complex [L^tBuNi(μ‐η¹:η¹‐N₂)NiL^tBu] ( I ) with KC₈, reaction of the resulting compound K[L^tBuNi(μ‐η¹:η¹‐N₂)NiL^tBu] ( II ) with sodium sand yields KNa[L^tBuNi(μ‐η¹:η¹‐N₂)NiL^tBu] ( 1 ), which contains two different alkali metal ions. Treatment of I with two equivalents of sodium sand leads to the symmetric complex Na₂[L^tBuNi(μ‐η¹:η¹‐N₂)NiL^tBu] ( 2 ). Complexes 1 and 2 were investigated by single crystal X‐ray diffraction analysis as well as by Raman spectroscopy, and the results were compared with the data of K₂[L^tBuNi(μ‐η¹:η¹‐N₂)NiL^tBu] ( III ), which contains two K⁺ ions. Thus, it became obvious that the nature of the alkali metal ion M in compounds M₂[L^tBuNi(μ‐η¹:η¹‐N₂)NiL^tBu] has hardly any influence on the degree of NN bond activation. Furthermore, it was shown that treatment of the dinickel(I) complex III with CO leads to the dinickel(0) compound K₂[L^tBuNi(CO)]₂ ( 4 ) and N₂. Reaction of the unreduced dinickel(I) complex I with CO leads to a more simple replacement of the N₂ ligand and formation of [L^tBuNi(CO)] ( 3 ).     

Production of charge-induced X-rays during PIXE studies using light and heavy ion-beams

A recently discovered phenomenon of excessively high X-ray production is discussed. The high yield is attributed to the build-up of potential on non-conducting targets irradiated with accelerated ion beams, and the subsequent discharge. Ion-beams of¹H⁺,¹H₂ ⁺,²H⁺,²H₂ ⁺,³He⁺,³He²⁺,⁴He⁺,¹⁴N⁺,¹⁴N²⁺,¹⁶O⁺ and²⁰Ne⁺ were used. A new mechanism of X-ray excitation is proposed. The increased X-ray fluxes produced by this process are suitable for analytical applications of high specificity. The mechanism of excitation associated with the process, factors affecting the high X-ray yields, applications and a general overview of the studies undertaken with the various ion beams are given.