13C, 14N, 15N and 17O NMR spectra of nitropyrroles and nitroimidazoles

Carbon, nitrogen and oxygen NMR spectra of some nitro derivatives of pyrrole and imidazole have been investigated. The ¹³C chemical shifts of para-carbons and the ¹⁷O chemical shifts of the nitro group correlate qualitatively with the electron densities on these carbon and oxygen atoms, which in turn depend upon the degree of conjugation of the nitro groups with the heterocyclic ring. Conjugation of several nitro groups with the benzene ring is in most cases not impaired by mutual interactions and the ¹³C shifts show good additivity. Such additivity is much worse in pyrrole and imidazole derivatives. Taken together with the diamagnetic nature of these deviations from additivity, this leads to a possible conclusion about the less pronounced conjugation of the nitro groups with the heterocyclic ring in heterocyclic dinitro derivatives.     

Platinum(IV) complexes with dipeptide. X-ray crystal structure, 195Pt NMR spectra, and their inhibitory glucose metabolism activity in Candida albicans

Three dipeptide complexes of the form K[Pt(IV)(dipep)Cl3] and two complexes of the form K[Pt(IV)(Hdipep)Cl4] were newly prepared and isolated. The platinum(IV) complexes containing the dipeptide were obtained directly by adding KI to H2[PtCl6] solution. The reaction using KI was rapidly completed and provided analytically pure yellow products in the form of K[Pt(dipeptide)Cl3] for H2digly, H2gly(alpha)-ala, H2alpha-alagly and H2di(alpha)-ala. The K[Pt(IV)(digly)Cl3] complex crystallizes in the monoclinic space group P2(1)/c with unit cell dimensions a = 10.540(3) A, b = 13.835(3) A, c = 8.123(3) A, beta = 97.01(2) degrees, Z = 4. The crystal data represented the first report of a Pt(IV) complex with a deprotonated peptide, and this complex has the rare iminol type diglycine(2-) coordinating to Pt(IV) with the bond lengths of the C2-N1 (amide) bond (1.285(13) A). The 195Pt NMR peaks of the K[Pt(IV)(dipep)Cl3] and the K[Pt(IV)(Hdipep)Cl4] complexes appeared at about 270 ppm and at about -130 ppm, respectively, and were predicted for a given set of ligand atoms. While the K[Pt(IV)(x-gly)Cl3] complexes, where x denotes the glycine or alpha-alanine moieties, were easily reduced to the corresponding platinum(II) complexes, the K[Pt(IV)(x-alpha-ala)Cl3] complexes were not reduced, but the Cl- ion was substituted for OH- ion in the reaction solution. The K[Pt(digly)Cl3] and K[Pt(gly-L-alpha-ala)Cl3] complexes inhibited the growth of Candida albicans, and the antifungal activities were 3- to 4-fold higher than those of cisplatin. The metabolism of glucose in C. albicans was strongly inhibited by K[Pt(digly)Cl3] and K[Pt(gly-L-alpha-ala)Cl3] but not by the antifungal agent fluconazole.     

Magnetic relaxation characteristics of Gd(III) in N,N-dimethylformamide according to 1H and 14N NMR data

The solvation of Gd³⁺ is studied in N,N-dimethylformamide by ¹H and ¹⁴N NMR in the temperature range of 298–373 K.     

13C, 14N, 15N and 17O NMR spectra of the charged species of nitropyrroles and nitroimidazoles

Changes in ¹³C and ¹⁴N chemical shifts of the nitro derivatives of nitrogen heterocycles upon ionization (anion or cation formation) are twofold—first a uniform paramagnetic or in the case of protonation, a uniform diamagnetic shift of all the ring resonances that parallels the changes in the respective ultraviolet spectra and must be caused by changes in the molecular excited states, and second—the influence of the conjugated nitro group. About one third of the total negative anion charge may be localized on the nitro group, which causes unusually large shifts of the ring ¹³C resonances in this case.     

A direct15N NMR study of erbium(III)-nitrate complexation in aqueous solvent mixtures

The extent of inner-shell ion-pair formation of Er³⁺ with nitrate ion in aqueous mixtures has been studied by nitrogen-15 (¹⁵N) NMR spectroscopy. At low temperature, exchange is slow enough to permit the direct observation of¹⁵N signals for nitrate ions in the Er³⁺ solvation shell and in bulk medium. In water-acetone mixtures,¹⁵N NMR signals for the mono-and bis complexes are observed at low nitrate to Er³⁺ mole ratios, but only the bis complex is evident at higher anion concentrations. No spectral evidence for the tris complex was seen at any nitrate concentration. In water-methanol-acetone mixtures, signals for the mono and bis complexes persist even at higher nitrate concentrations, indicating a reduced tendency to ion-pair with increasing dielectric constant. Preliminary¹⁵N NMR results are presented for the nitrate complexes of other paramagnetic lanthanide ions.     

Coordination around thorium(IV) in aqueous perchlorate,chloride and nitrate solutions

The coordination around the thorium(IV) ion in aqueous perchlorate, chloride and nitrate solutions has been determined from large angle X-ray scattering measurements. In perchlorate solutions, where inner-sphere complexes are not formed, the first coordination sphere contains 8.0±0.5 water molecules with Th-H₂O bond lengths of 2.48₅ Å. In chloride solutions inner-sphere complexes are formed, which lead to an increase in the coordination number. In nitrate solutions the nitrate ions are bonded as bidentate ligands to the thorium ion. The bond lengths are similar to those found in crystalline hydrates of thorium nitrate. The coordination numbers found for thorium(IV) in solution are compared with previously reported values for lower charged ions of similar size.On leave from Department of Inorganic Chemistry Royal Institute of Technology S-10044 Stockholm Sweden     

1H, 13C, 15N and 195Pt NMR studies of Au(III) and Pt(II) chloride organometallics with 2‐phenylpyridine

¹H, ¹³C, ¹⁵N and ¹⁹⁵Pt NMR studies of gold(III) and platinum(II) chloride organometallics with N(1),C(2′)‐chelated, deprotonated 2‐phenylpyridine (2ppy*) of the formulae [Au(2ppy*)Cl₂], trans(N,N)‐[Pt(2ppy*)(2ppy)Cl] and trans(S,N)‐[Pt(2ppy*)(DMSO‐d₆)Cl] (formed in situ upon dissolving [Pt(2ppy*)(µ‐Cl)]₂ in DMSO‐d₆) were performed. All signals were unambiguously assigned by HMBC/HSQC methods and the respective ¹H, ¹³C and ¹⁵N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: Δ^1H_coord = δ^1H_complex ? δ^1H_ligand, Δ^13C_coord = δ^13C_complex ? δ^13C_ligand, Δ^15N_coord = δ^15N_complex ? δ^15N_ligand), as well as ¹⁹⁵Pt chemical shifts and ¹H‐¹⁹⁵Pt coupling constants discussed in relation to the known molecular structures. Characteristic deshielding of nitrogen‐adjacent H(6) protons and metallated C(2′) atoms as well as significant shielding of coordinated N(1) nitrogens is discussed in respect to a large set of literature NMR data available for related cyclometallated compounds. Copyright © 2009 John Wiley & Sons, Ltd.     

195Pt NMR chemical shift trend analysis as a method to assign new Pt(IV)-halohydroxo complexes

A 195Pt NMR spectroscopy study of the speciation of [PtCl6]2-, [PtBr6]2-, and the mixed [PtCl6-mBrm]2- (m=0-6) anions in aqueous medium after hydroxide ion substitution of coordinated halide ions has been carried out under dynamic conditions. Of the 56 possible [PtCl6-m-nBrm(OH)n]2- (m, n=0-6) complex anions in solution under dynamic conditions, the relative chemical shifts delta(195Pt) of 52 observable species have been assigned, 33 of which had not been reported previously. The assignment of all these species including the possible stereoisomers is facilitated by systematic linear relationships between the delta(195Pt) increments resulting from substitutions of the halide ions by OH- ions. Under dynamic conditions, the relative concentration (as indicated by resonance intensities) of the [PtCl6-m-nBrm(OH)n]2- (m, n=0-6) species was found to be largely determined by the trans effects on ligand substitution reactions, leading to the transient appearance of previously unobserved complexes. Only the 2c2c2t and 2t2t2t isomers of the ternary [PtCl2Br2(OH)2]2- complex, the 3m12t [PtCl3Br(OH)2]2- and the 13m2t [PtClBr3(OH)2]2- anions could not be observed under our conditions, although their delta(195Pt) are confidently predictable from the linear trend analysis. This chemical shift trend analysis constitutes a powerful method for the virtually unambiguous assignment of 195Pt chemical shifts for such complex anions undergoing slow ligand exchange on the NMR time scale, as facilitated by the strikingly good correlations of delta(195Pt) for the species as a function of the number of hydroxide ions in the coordination sphere.     

The effect of temperature on the complexation of Cm(III) with nitrate in aqueous solutions

The complexation of curium(III) with nitrate was studied at different temperatures (10-85 °C) by luminescence spectroscopy. The stability constants of CmNO(3)(2+) were calculated from the luminescence emission spectra. The specific ion interaction approach (SIT) was used to obtain the stability constants of CmNO(3)(2+) at infinite dilution and variable temperatures. The complexation is weak and little effect of temperature on the complexation was observed over the temperature range 10-85 °C. Data on the luminescence lifetime indicate that each nitrate ligand replaces two water molecules from the inner coordination sphere of Cm(3+), forming a bidentate inner-sphere complex with Cm(3+) in aqueous solutions.     

A direct carbon-13 and nitrogen-15 NMR study of samarium(III) complexation with nitrate and isothiocyanate in aqueous solvent mixtures

The extent of inner-shell, contact ion-pairing between samarium(III)-nitrate and in a preliminary manner, samarium(III)-isothiocyanate, has been determined by a direct, low-temperature, multinuclear magnetic resonance technique. In water-acetone mixtures containing Freon-12 or Freon-22, the slow exchange condition is achieved at –110 to –120°C, permitting the observation of¹⁵N NMR resonance signals for bulk and coordinated nitrate. In these mixtures, signals are observed for Sm(NO₃)²⁺, Sm(NO₃) ₂ ⁺ , and two higher complexes, possibly the tetranitrato with either the penta-or hexanitrato.¹H NMR signals for bound water molecules in these mixtures were observed, but accurate hydration numbers can not yed be determined. In anhydrous or aqueous methanol mixtures,¹⁵N NMR signals for only three complexes are observed, with the dinitrato clearly dominating. Using¹⁵N and³⁵Cl NMR chemical shift and linewidth measurements, the superior complexing ability of nitrate compared to perchlorate and chloride, was demonstrated. Successful preliminary¹³C and¹⁵N NMR measurements of Sm³⁺-NCS^– interactions in water-acetone-Freon-22 mixtures also have been made. The¹³C NMR spectra reveal signals for five complexes, presumably Sm(NCS)²⁺ through Sm(NCS) ₅ ^2– . In the¹⁵N NMR spectra, signals for only three complexes are observed (the result of insufficient spectral resolution.) displaced about +240 ppm from bulk anion.     

Solvent extraction of thorium(IV) ion with N,N,N,N-tetrabutylsuccinylamide from nitric acid solutions

It was found that N,N,N,N-tetrabutylsuccinylamide (TBSA) in a diluent composed of 50% 1,2,3-trimethylbenzene (TMB) and 50% kerosene (OK) can extract thorium(IV) ion from a nitric acid solution. The results of the extraction study suggested the formation of a 141 thorium(IV) ion, nitrate ion and N,N,N,N-tetrabutylsuccinylamide complex as extracted species. The related thermodynamic functions were also calculated.     

Methanol and acetonitrile associates in aqueous and chloroform solutions according to 1H NMR spectroscopic data

Association of methanol and acetonitrile in a nonpolar (CDCl₃) and polar (H₂O and D₂O) solvents was studied by ¹H NMR spectroscopy and quantum chemistry. The results were compared with the data obtained by decomposition of the spectral curves in the range 800–1100 nm by the independent component analysis (ICA) technique. The content of homoassociates consisting of four and two or three molecules in the case of methanol and acetonitrile, respectively, gradually increased with the amount of the organic solvent in solution. The aqueous solutions under study consisted of few associates of compositions 1: 1, 1: 2, and 1: 4.5 for acetonitrile and 1: 1 and 1: 3 for methanol (water: organic solvent). The quantum-chemical calculation of the NMR spectra of the particles existing in solution confirmed our conclusions about the structure of the solutions.     

Synthesis of (15N2)[17O]Urea, (15N2)[O2, O4-17O2]Uridine,and (15N3)[O2-17O]Cytidine

A general synthetic approach for the synthesis of ¹⁵N- and ¹⁷O-doubly labelled pyrimidine nucleosides is described. The ¹⁵N isotopes in uridine and the ¹⁷O isotope in the urea-derived carbonyl group of uridine and cytidine originate from (¹⁵N₂)[¹⁷O]urea ( 5 ) which was synthesized from ¹⁵NH₄Cl, thiophosgene ( 1 ), and H₂[¹⁷O]. The third ¹⁵N isotope of cytidine in 4-position stems from the substitution of the 1,2,4-triazole moiety of (¹⁵N₂)[O²-¹⁷O]uridine derivative 8a/b with ¹⁵NH₄OH. Hydrolysis of the same key intermediate 8a/b with Na[¹⁷O]H/H₂[¹⁷O] introduced the second ¹⁷O isotope into the 4-position of uridine. The ¹⁵N- and ¹⁷O-NMR spectra of the target compounds 12 and 14 in phosphate-buffered H₂O serve as references for heteronuclear NMR spectra of labelled RNA fragments.     

1H, 13C, 195Pt and 15N NMR structural correlations in Pd(II) and Pt(II) chloride complexes with various alkyl and aryl derivatives of 2,2'-bipyridine and 1,10-phenanthroline

(1)H, (13)C, (195)Pt and (15)N NMR studies of platinide(II) (M = Pd, Pt) chloride complexes with such alkyl and aryl derivatives of 2,2'-bipyridine and 1,10-phenanthroline as LL = 6,6'-dimethyl-bpy, 5,5'-dimethyl-bpy, 4,4'-di-tert-butyl-bpy, 2,9-dimethyl-phen, 2,9-dimethyl-4,7-diphenyl-phen, 3,4,7,8-tetramethyl-phen, having the general [M(LL)Cl(2)] formula were performed and the respective chemical shifts (δ(1H), δ(13C), δ(195Pt), δ(15N)) reported. (1)H high-frequency coordination shifts (Δ(coord)(1H) = δ(complex)(1H)-δ(ligand)(1H)) mostly pronounced for nitrogen-adjacent protons and methyl groups in the nearest adjacency of nitrogen, as well as (15)N low-frequency coordination shifts (Δ(coord)(15H) = δ(complex)(15H)-δ(ligand)(15H)) were discussed in relation to the molecular structures.     

The complexation of (N,N-diethylcarbamoylmethyl)diphenylphosphine sulfide with silver nitrate

The crystalline complex [Ag(L ¹)NO₃]₂ (A) was isolated by the interaction of (N,N-diethylcaibamoylmethyl)diphenylphosphine sulfide Ph₂P(S)CH₂C(O)NEt₂ (L ¹) with AgNO₃ in different solvents at the ratios of metal:ligand = 11 and 12. According to the X-ray data, complexA is a center-symmetric dimer with bridge sulfur atoms. The cations of the metal are in a tetrahedral environment formed by two S atoms and the O atoms of CO and NO₃ groups. The interaction ofL ¹ with AgNO₃ was studied in solution by IR spectroscopy, and the structures of the complexes formed are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 708–713, April, 1994.The authors are grateful to B. V. Lokshin and his coworkers for help in measurement of the Raman spectra and for useful discussion.The present investigation was financially supported by the Russian Foundation for Basic Research (Project 93-03-4351).     

14N, 17O, 103Rh NMR Studies of Rh(III) State in Diluted Nitric Acid Solutions

The state of rhodium(III) in nitric acid solutions diluted with 3M HNO₃ or water was studied by ¹⁴N, ¹⁷O, and ¹⁰³Rh NMR methods. The ¹⁰³Rh NMR chemical shifts significantly depend on the ionic background of the solution. Concentrated nitric acid solutions (c _Rh = 0.5–1 mol/l) diluted 100 to 200 times retain the polynuclear Rh(III) forms with double (-NO₃, -OH) bridges. The predominant form in the diluted solutions is a dimer.     

195Pt NMR study of the speciation and preferential extraction of Pt(IV)-mixed halide complexes by diethylenetriamine-modified silica-based anion exchangers

A detailed 195Pt NMR study of the distribution of Pt(IV) complex species resulting from the aquation of H2PtCl6, H2PtBr6, and mixtures of H2PtCl6/H2PtBr6 in water/dilute HClO4 has been carried out to obtain an understanding of the speciation in these solutions as relevant to the recovery of Pt(IV) complexes from process solutions. A species distribution plot of the [PtCl6]2-, [PtCl5(H2O)]-, and [PtCl4(H2O)2] shows that in equilibrated, relatively concentrated H2PtCl6 solutions ([Pt]t > 0.12 M), the [PtCl4(H2O)2] species is below the 195Pt NMR detection limit; for [Pt]t concentrations < 0.1 M, the relative concentrations of the [PtCl5(H2O)]- and [PtCl4(H2O)2] species increase significantly, as a result of relatively rapid aquation of the [PtCl6]2- and [PtCl5(H2O)]- complexes under these conditions. From this (195)Pt NMR data the aquation constants of [PtCl6]2- and [PtBr6]2- of log K6 approximately 1.75 +/- 0.05 and log K6 approximately 2.71 +/- 0.15, respectively, have been determined at 30 degrees C. In mixtures of H2PtCl6/H2PtBr6 in water, a number of previously unidentified aquated complexes of the general formula [PtCl(5-n)Br(n)(H2O)]- (n = 0-5) could be identified, including the possible geometrical isomers of these complexes. These 195Pt NMR assignments were confirmed by remarkably systematic, linear relationships between the 195Pt chemical shift increments induced by substitution of Cl- ions by n Br- ions in [PtCl(6-n)Br(n)]2- and [PtCl(5-n)Br(n)(H2O)]- complexes. Preferential extraction of the [PtX6]2- (X = Cl, Br, or a mixture of the two halides) species over their corresponding aquated [PtX5(H2O)]- counterparts by silica-based diethylenetriamine anion exchangers could be demonstrated by means of 195Pt NMR spectroscopy.     

Thermodynamic parameters of complexation reactions between nickel(II) ion and L-serine in aqueous solutions

A thermochemical study of coordination equilibria in the nickel(II) ions-L-serine system was carried out. The heats of reaction between solutions of an amino acid and nickel(II) nitrate at 288.15, 298.15, and 308.15 K and ionic strength of 0.25, 0.50, and 0.75 (KNO₃) were measured. The heats of dilution of nickel nitrate solution in background electrolyte solutions were determined under identical conditions to make proper corrections. The results were processed with allowance for stepwise equilibria. The standard thermodynamic parameters of the complexation processes were calculated. The effect of temperature on heats of complexation reactions in the L-serine-nickel(II) ions was studied. The standard enthalpies of formation of NiSer⁺, NiSer₂, and NiSer ₃ ^? complexes in aqueous solutions were determined.