Indirect detection of 31P,X connectivities with proton sensitivity: application of two‐dimensional 31P‐relayed 1H,X correlation spectroscopy

Experiments for ¹H‐detected heteronuclear ¹H,X correlation spectroscopy with ³¹P‐relayed coherence transfer are described which allow the indirect detection of δX and ⁿJ(X,P) even in the absence of a direct J(X,H) coupling. The use of these techniques for the assignments of ¹³C, ¹⁵N, and ¹⁸³W NMR data of organophosphorus compounds is demonstrated. Copyright © 2003 John Wiley & Sons, Ltd.     

Application of two‐dimensional near‐infrared (2D‐NIR) correlation spectroscopy to the discrimination of three species of Dendrobium

The objective of this paper was to apply two‐dimensional (2D) near‐infrared (NIR) correlation spectroscopy to the discrimination of three species of Dendrobium. Generalized 2D‐NIR correlation spectroscopy was able to enhance spectral resolution, simplify the spectrum with overlapped bands and provide information about temperature‐induced spectral intensity variations that was hard to obtain from one‐dimensional NIR spectroscopy. The FT‐NIR spectra were measured over a temperature range of 30–140°C. The 2D synchronous and asynchronous spectra showed remarkable differences within the range of 5600–4750 cm⁻¹ between different species of Dendrobium. Copyright © 2009 John Wiley & Sons, Ltd.     

Two‐dimensional Fourier transform infrared correlation spectroscopy and evolving factor analysis in the study of cationic curing of DGEBA and γ‐valerolactone mixtures

Generalized two‐dimensional (2D) correlation spectroscopy and evolving factor analysis (EFA) have been applied to the study of cationic curing reaction of mixtures of diglycidyl ether of bisphenol A (DGEBA) and γ‐valerolactone (γ‐VL). The reaction has been monitored by Fourier transform infrared spectroscopy. The reaction periods in which a chemical change takes place are identified using EFA and then the sequence of changes are established by means of the interpretation of the synchronous and asynchronous spectra obtained with 2D correlation spectroscopy. By combining this information, in the curing process, four reactions have been detected: (1) DGEBA and γ‐VL reaction to obtain a spiroorthoester intermediate, (2) homopolymerization of DGEBA, (3) copolymerization of DGEBA with the spiroorthoester intermediate, and (4) homopolymerization of the spiroorthoester. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3886–3899, 2008     

LSn(OCH2CH2)2NR (L = lone pair,W(CO)5; R = Me,t‐Bu). The Molecular Structures of 5‐Aza‐2,8‐dioxa‐1‐stannabicyclo[3.3.0]1.5octanes and Their Tungstenpentacarbonyl Complexes

Single crystal X‐ray diffraction analyses of LSn(OCH₂CH₂)₂NR [ 1 , R = Me, L = lone pair; 2 , R = Me, L = W(CO)₅; 3 , R = t‐Bu, L = W(CO)₅] reveal these compounds to be dimeric and cis‐configurated. The dimerization is realized by intramolecular O→Sn interactions to give four‐membered Sn₂O₂‐rings. In addition, there are intramolecular N→Sn interactions ranging in between 2.356(5) ( 2 ) and 2.549(4) Å ( 3 ).     

Characterization of signals in the solution 1H NMR spectrum of poly(isobutylene‐co‐p‐methylstyrene) and their utility

Poly(isobutylene‐co‐p‐methylstyrene) is an important precursor to Exxpro™ elastomers. A previous report detailed the characterization of both the proton and the carbon NMR spectra of the copolymer. 1 However, several resonances in the proton NMR spectrum of the copolymer were not assigned. Specifically, the proton methine resonance of the BSB triad sequence is now identified and used to calculate BSB triad contribution to the copolymer microstructure. This report describes the assignment of this resonance and other resonances associated with microstructural sequence distribution around p‐methylstyrene. The proton NMR signals of interest resonate at 2.8 ppm and 2.5 ppm in a typical spectrum for poly(isobutylene‐co‐p‐methylstyrene). The nature of these resonances were determined by preparation and characterization of specifically deuterated poly(isobutylene‐co‐p‐methylstyrene)s employing both one and two dimensional NMR techniques. The 2.8 ppm signal is assigned as the methine proton of a p‐methylstyrene incorporated between two isobutylene units (the BSB triad). The signal at 2.5 ppm is assigned to the meso‐BSS triad. Determination of these resonances allows for rapid evaluation of isolated p‐methylstyrene units (BSB triads) present in the copolymer using only ¹H NMR. The utility of this technique is demonstrated by comparing BSB triad values determined by ¹H and ¹³C NMR analysis. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1680–1686, 2000     

Synthesis and structure elucidation of three series of nitro‐2‐styrylchromones using 1D and 2D NMR spectroscopy

2‐Styrylchromones, although scarce in nature, constitute a group of oxygen heterocyclic compounds which have shown significant biological activities. New nitro‐2‐styrylchromones have been synthesised by the Baker–Venkataraman method, and the structure elucidation was accomplished using extensive 1D (1H, 13C) and 2D NMR spectroscopic studies (COSY, HSQC and HMBC experiments). Copyright © 2009 John Wiley & Sons, Ltd.     

The structural and dynamic properties of 1‐bromodecane in urea inclusion compounds investigated by solid‐state 1H, 13C and 2H NMR spectroscopy

For asymmetric guest molecules in urea, the end‐groups of two adjacent guest molecules may arrange in three different ways: head–head, head–tail and tail–tail. Solid‐state ¹H and ¹³C NMR spectroscopy is used to study the structural properties of 1‐bromodecane in urea. It is found that the end groups of the guest molecules are randomly arranged. The dynamic characteristics of 1‐bromodecane in urea inclusion compounds are probed by variable‐temperature solid‐state ²H NMR spectroscopy (line shapes, spin–spin relaxation: T₂, spin‐lattice relaxation: T_1Z and T_1Q) between 120 K and room temperature. The comparison between the simulation and experimental data shows that the dynamic properties of the guest molecules can be described in a quantitative way using a non‐degenerate three‐site jump process in the low‐temperature phase and a degenerate three‐site jump in the high‐temperature phase, in combination with the small‐angle wobbling motion. The kinetic parameters can be derived from the simulation. Copyright © 2011 John Wiley & Sons, Ltd.     

Spatial structure of heptapeptide Aβ16–22 (beta‐amyloid Aβ1–40 active fragment) in solution and in complex with a biological membrane model

The spatial structure of an active fragment of beta‐amyloid Aβ_1–40 heptapeptide Aβ_16–22 (Lys‐Leu‐Val‐Phe‐Phe‐Ala‐Glu) in aqueous buffer solution and in complex with sodium dodecyl sulfate micelles as a model membrane system was investigated by ¹H NMR spectroscopy and two‐dimensional NMR (TOCSY, HSQC‐HECADE (Heteronuclear Couplings from ASSCI‐domain experiments with E.COSY‐type crosspeaks), NOESY) spectroscopy. Complex formation was confirmed by the chemical shift changes of the heptapeptide's ¹H NMR spectra, as well as by the signs and values of the NOE effects in different environments. We compared the spatial structure of the heptapeptide in borate buffer solution and in complex with a model of the cell surface membrane. Copyright © 2012 John Wiley & Sons, Ltd.     

Tautomeric behaviour and isotopic multiplets in the 13C NMR spectra of partially deuterated 5‐arylazo‐pyrimidine (1H,3H,5H)‐2,4,6‐triones and 5‐arylazo‐2‐thioxo‐pyrimidine (1H,3H,5H)‐4,6‐diones—evidence for elucidation of tautomeric forms

NMR spectra of the synthesized azo dyes, 5‐arylazo‐pyrimidine (1H,3H,5H)‐2,4,6‐triones (5a–g), 1,3‐dimethyl‐5‐arylazo‐pyrimidine (1H,3H,5H)‐2,4,6‐triones (6a–g), and 5‐arylazo‐2‐thioxo‐pyrimidine (1H,3H,5H)‐4,6‐diones (7a–g) were studied in (CD₃)₂SO (three drops of CD₃OD were added into solutions of the dyes in two different concentrations). All dyes showed intramolecular hydrogen bonding. Dyes 5a–7a showed bifurcated intramolecular hydrogen bonds. Tautomeric behaviours of some of N‐methylated azo dyes (6a‐g) were studied in two different concentrations. The solvent–substrate proton exchange of dyes 5a–d, 6a and 7a–e was examined in presence of three drops of CD₃OD. The dyes which were soluble in (CD₃)₂SO containing CD₃OD showed isotopic splitting (β‐isotope effect) in the ¹³C NMR spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Conformational analysis of some 1R,4S‐2‐arylidene‐p‐menthan‐3‐ones by 1H NMR spectroscopy and molecular simulation

Based on ¹H NMR spectral analysis combined with molecular simulation, conformational states of the cyclohexanone ring were studied for some 1R,4S‐2‐(4‐X‐benzylidene)‐p‐menthan‐3‐ones (X = COOCH₃ or C₆H₅) in CDCl₃ and C₆D₆. The co‐existence of chair conformers with an axial orientation of both alkyl substituents and twist‐boat forms was established for the compounds studied at room temperature (22–23° C). The substituent X does not influence appreciably the ratio of these conformers, but the fraction of twist‐boat forms increases noticeably in benzene solutions as compared with CDCl₃ solutions. Rotameric states of the isopropyl fragment were also characterised for the compounds studied. Distinctions in conformational states for the 1R,4S‐2‐arylidene‐p‐menthan‐3‐ones and (?)‐menthone were revealed and are discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

1H, 13C and 15N NMR investigation of a new,condensed hexahydro‐1,3,5‐triazine

Treatment of 2‐acetyl‐2‐methylcyclopentanone with hydrazine hydrate yielded a new condensed hexahydro‐1,3,5‐triazine (3b), which is the first example of the ketimine‐type trimers. A complete ¹H, ¹³C and ¹⁵N NMR assignment of the compound was achieved. Copyright © 2003 John Wiley & Sons, Ltd.     

Characterization of the malate-aluminum(III) complex using 1H and 27Al NMR spectroscopy

Structural elucidation of a malate-aluminum(III) complex has been carried out using 1H and 27Al NMR spectroscopy. The 1H chemical shift perturbation clearly indicated the interaction between malate and Al(III) ion. The measurements of 27Al NMR and 1H-13C HSQC spectra demonstrated that the major form of a complex comprised two equivalent malate ions and two unequivalent Al(III) ions. With this constraint, an equilibrium geometry of the complex was proposed by a semi-empirical molecular orbital calculation.     

Characterization of the complex formation of 1,6‐anhydro‐β‐maltotriose with potassium using 1H and 39K NMR spectroscopy

The ¹H and ³⁹K longitudinal relaxation times (T₁) and ¹H diffusion coefficients were measured to investigate the complex formation of 1,6‐anhydro‐β‐maltotriose and potassium ions. Although the ¹H‐T₁ values of H3′, H5′, H1″ and H4″ decreased in the presence of potassium ions, ¹H chemical shifts and ¹H diffusion coefficients did not show significant changes. The long‐range coupling constants of ³J_C?H around the glycosyl bonds did not show significant changes either. In the measurements of ³⁹K spectra, the ³⁹K signal obviously broadened and the ³⁹K‐T₁ values decreased in the presence of 1,6‐anhydro‐β‐maltotriose, indicating the complex formation of 1,6‐anhydro‐β‐maltotriose and potassium ions. These results indicate that the conformation and molecular volume were unaffected in the complex formation. Copyright © 2009 John Wiley & Sons, Ltd.     

One‐dimensional TOCSY 1H NMR experiments on adducts of amino acid esters with cobalt(III) tetramethylchiroporphyrin. Prospects for the analysis of amino acid mixtures

Cobalt(III) tetramethylchiroporphyrin, CoCl(TMCP), is a useful chiral shift reagent for structure attribution, absolute configuration assignment and enantiomeric excess determination of amino acid methyl esters by ¹H NMR spectroscopy. However, it has two axial sites available for amine coordination, a structural feature which generates n(n + 1)/2 diastereomeric species and n² distinct spin systems from a mixture of n amino ester enantiomers, making the analysis of complex amino acid samples exceedingly difficult by classical 1‐D or 2‐D NMR methods when n > 3. The 1‐D TOCSY experiment is shown to be a powerful tool for the selective excitation and detection of every single component of a mixture of four amino acid methyl esters bound to CoCl(TMCP): those of(S)‐Leu, (S)‐Asp, (R)‐Asp and (S)‐Glu, for example. The potential utility of this methodology for the determination of amino acid enantiomers in carbonaceous meteorites or other extraterrestrial samples is suggested. Copyright © 2002 John Wiley & Sons, Ltd.     

Study of phenothiazine and N‐methyl phenothiazine by infrared,raman, 1H‐, and 13C‐NMR spectroscopies

A complete vibrational analysis of the Fourier transform (FT) infrared (IR) and FT‐Raman spectra of both molecules was carried out using quantum chemical calculations. The structure of phenothiazine (PTZ) and N‐methylphenothiazine (N‐MePTZ) were studied by semiempirical, and ab initio methods. Different basis sets and two new procedures for scaling the frequencies of the ring modes were used. Vibrational data of the methyl group in N‐MePTZ were interpreted in terms of the different molecular conformations in the solid state. The ¹H‐ and ¹³C–nuclear magnetic resonance (NMR) data were interpreted in terms of the electron densities on the atoms and the stacking solute–solute association in dimethyl sulfoxide solution. Chemical shifts were related to the Merz‐Kollman atomic charges. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Assignment of the E,Z configurational isomers of platinum complexes of N,N‐dialkyl‐N′‐acyl(aroyl)thioureas by means of triple resonance 1H/13C/195Pt PFG correlation NMR spectroscopy

Unsymmetrical, dialkyl‐substituted N,N‐dialkyl‐N^′‐acyl(aroyl)thioureas show E,Z configurational isomerism at room temperature in solution, which is also expressed in the existence of cis‐[Pt(ZZ‐L‐S,O)₂], cis‐[Pt(EZ‐L‐S,O)₂] and cis‐[Pt(EE‐L‐S,O)₂] complexes derived from these ligands. These configurational isomers were assigned by means of a double magnetization transfer ¹H/¹³C/¹⁹⁵Pt correlation NMR experiment, despite the fact that the long‐range ⁵J(¹⁹⁵Pt, ¹H) and ⁴J(¹⁹⁵Pt, ¹³C) scalar couplings are not directly observable in their ¹H and ¹³C spectra at high field. Depending on the ligand structure, the relative amounts of cis‐[Pt(ZZ‐L‐S,O)₂], cis‐[Pt(EZ‐L‐S,O)₂] and cis‐[Pt(EE‐L‐S,O)₂] complexes are in the ranges 40–42% ZZ, 46–47% ZE and 12–13% EE. The cis‐bis[N‐methyl‐N‐(tert‐butyl)‐N^′‐(2,2‐dimethylpropanoyl)thioureato]platinum(II) complex is found to occur exclusively as the ZZ isomer. Copyright © 2003 John Wiley & Sons, Ltd.     

Heterocyclic analogs of xanthiones: 5,6‐fused 3‐methyl‐1‐phenylpyrano[2,3‐c]pyrazol‐4(1H) thiones—synthesis and NMR (1H, 13C, 15N) data

Various [5,6]pyrano[2,3‐c]pyrazol‐4(1H)‐thiones were synthesized in high yields by treatment of the corresponding [5,6]pyrano[2,3‐c]pyrazol‐4(1H)‐ones with Lawesson's reagent. Detailed NMR spectroscopic studies were undertaken of the title compounds. Complete and unambiguous assignment of chemical shifts (¹H, ¹³C, ¹⁵N) and coupling constants (¹H,¹H; ¹³C,¹H) was achieved by the combined application of various one‐ and two‐dimensional (1D and 2D) NMR spectroscopic techniques. Unequivocal mapping of most ¹³C,¹H spin coupling constants is accomplished by 2D (δ, J) long‐range INEPT spectra with selective excitation. Copyright © 2010 John Wiley & Sons, Ltd.     

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.     

Synthesis,spectroscopic characterization (IR, 1H, 13C and 119Sn NMR,electrospray mass spectrometry) and toxicity of new organotin(IV) complexes with N,N′,O‐ and N,N′,S‐scorpionate ligands

New organotin(IV) derivatives containing the anionic ligands bis(3,5‐dimethylpyrazol‐1‐yl)dithioacetate [LCS₂]⁻ and bis(3,5‐dimethylpyrazol‐1‐yl)acetate [LCO₂]⁻ have been synthesized from reaction between (CH₃)₂SnCl₂ and lithium salts of the ligands. Mononuclear complexes of the type {[LCX₂](CH₃)₂SnCl} (X = S or O) have been obtained and fully characterized by elemental analyses and FT‐IR in the solid state and by NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy, conductivity measurements and electrospray ionization mass spectrometry in solution. The acute toxicity of new organotin(IV) derivatives on rat was studied, comparing their effect with those of dimethyltin chloride (CH₃)₂SnCl₂. The comparison of LD₅₀ of organotin(IV) complexes and (CH₃)₂SnCl₂ administered intraperitoneally, as a single dose, evaluated in vivo on rats, showed that toxicity decreases as follows: (CH₃)₂SnCl₂ > LCO₂ > LCS₂. The effect of these organotin(IV) complexes on DNA was evaluated in vitro and in vivo on rats treated with different doses of these compounds (1/20 LD₅₀ and 1/100 LD₅₀). The lymphocyte DNA status was assessed by the comet assay, a rapid and sensitive single‐cell electrophoresis technique, used to detect primary DNA damage in individual cells. After 36 h from the start of treatment the two new organotin(IV) derivatives induced a significant rise in comet assay parameters, indicating an increasing presence of damaged DNA. Copyright © 2005 John Wiley & Sons, Ltd.     

1H, 13C and 15N NMR assignments for N‐ and O‐acylethanolamines,important family of naturally occurring bioactive lipid mediators

The complete ¹H, ¹³C and ¹⁵N NMR signal assignments of some N‐ and O‐acylethanolamines, important family of naturally occurring bioactive lipid mediators, were achieved using one‐dimensional and two‐dimensional experiments (gs‐HMQC and gs‐HMBC). Copyright © 2012 John Wiley & Sons, Ltd.