Solid-state 13C CPMAS Research Articles

Solid state 13C CP-MAS NNR and other spectral studies of tradition mental complexes

Solid state 13C CP-MAS NNR and other spectral studies of tradition mental complexes

Nature and distribution of alkyl carbon in forest soil profiles: implications for the origin and humification of aliphatic biomacromolecules

Resistant residues isolated from whole soils were subjected to analysis by solid-state CPMAS 13C NMR and Curie-point pyrolysis-gas chromatography-mass spectrometry to delineate the nature of the resistant aliphatic components. These components constitute a major fraction of soil organic matter and associated humic substances and appear to be concentrated during soil formation initially by a process of selective preservation. Changes in the nature of these biomacromolecules with increasing depth and decomposition in the soil profile indicate that they are being altered significantly. The NMR data show that the aliphatic structures in forest soil organic matter can be assigned to mobile and rigid carbon moieties. The mobile and rigid carbon types are possibly associated with different types of macromolecules. One type are the polyesters cutin and suberin from leaves, barks and roots, the other is a resistant non-saponifiable aliphatic biomacromolecule derived from leaves and barks or microorganisms. At depth in the soil profile the mobile components are degraded but the rigid aliphatic biomacromolecules appear to be selectively preserved. However, the pyrolysis data indicate that these non-saponifiable aliphatic macromolecules bear no resemblance to the resistant aliphatic biomacromolecules in fresh leaf cuticles or microbial cell walls. This lack of resemblance is probably due to the fact the selective preservation of resistant, non-saponifiable plant or microbial macromolecules is not the dominant process leading to the accumulation of alkyl carbon moieties in forest soil organic matter. Alternatively, it seems possible that the structural differences observed between the alkyl carbon moieties in forest litter and humified soil horizons result from an increase in cross-linking during humification.

Demonstration of spatial heterogeneity in the organic matter of de-ashed humin samples by solid-state 13C CPMAS NMR

A variant of solid-state 13C CPMAS NMR demonstrated the presence of carbon in spatially distinct domains within three de-ashed samples of humin from a forest soil profile under Douglas-fir near Victoria, British Columbia. Differences in 1H T1 values indicated incomplete spin diffusion in the solid state and separation of organic matter in domains with dimensions of tens of nanometres or more. These relaxation differences were used to separate subspectra of carbons associated with the slower- and faster-relaxing protons. The former were dominated by methylene chains, while the latter contained more aromatic and O-alkyl carbon. Most of the organic matter appears to remain associated with iron even after extensive de-ashing with HCl/HF, but the aromatic and carbohydrate structures appear to be more closely associated with iron than methylene groups in long chains. This NMR technique offers a novel approach to probing the structure of insoluble soil organic matter. Key words: Humin, CPMAS NMR, relaxation, iron, forest soil, Brunisol

Solid-state 13C NMR CP MAS high-resolution spectroscopy of chromogens: structural aspect of problem

Chromogens of different classes, viz., arylazo derivatives of resorcinol, naphthols, naphthylamines, chromotropic acid and its cyclic modification, and also someformazans, are investigated using high-resolution solid-state NMR 13C CP MAS. The technique revealed spectral data pertinent to the similarity and difference of the compounds in the solid state and in solution.

Motion in solid organotin(IV) coordination polymers: a two-dimensional exchange magic angle spinning 13C NMR study

Solid-state 13C CP MAS NMR studies of compounds [(Me3Sn)4M(CN)6]∞ with M = Fe, Ru and Os, using variable temperature, show that the trigonal bipyramidal arrangements at Sn are undergoing internal rotation about the N-Sn-N axes with lifetimes of the order of 0.5 s at moderately lowered temperature.

The hydroxonium perchlorate complex of cis-syn-cis-dicyclohexano 18-crown-6 ether: conformational analysis in the solid state and in solution at low temperature as studied via 13C NMR methods

From 100.6-MHz 13C NMR coalescence temperature measurements, the title complex is shown to undergo a single degenerate ring inversion process with a free energy barrier of [Formula: see text]. This is ca. 5 kJ/mol higher than the barrier in the free crown. The solid state 13C CPMAS spectrum is indicative of a totally unsymmetrical conformation and the shift trends in the solid are analyzed in terms of local torsional angle variations. Comparisons of experimental vs. calculated (GIAO) 13C chemical shift ranges for the CH2O carbons in the solid are made and satisfactory agreement with respect to the overall range and magnitude of the 13C shielding differences is obtained. Key words: crown ethers, stereochemistry, NMR.

Synthesis, structure, and solid state 13C NMR spectroscopy of a highly substituted tricarbonyl(cyclobutabenzene)chromium(0) derivative

The synthesis, spectroscopic characterization, and the X-ray crystal structure determination of tricarbonyl-η 6-[1,2-bis(ethylendioxy)cyclobutabenzene]chromium(0) are described. The free enthalpy of activation of the Cr(CO) 3 rotation has been determined by variable temperature solid state 13C CP-MAS NMR spectroscopy to be ca. 60kJ/mol.

Investigations of the transitions of some tetraalkylammonium halides by DSC, NMR, and X-ray diffraction

The transitions of several symmetric tetraalkylammonium halides were studied by differential scanning calorimetry (DSC), solid-state nuclear magnetic resonance (NMR) and X-ray diffraction. The reversibility of the transitions of Bu 4NI is investigated by cycling of the samples in the DSC. A plastic-crystalline phase is found and characterized. A glass transition is observed for Bu 4NCl at 230 K. Solid-state CP-MAS 13C NMR is performed on Hex 4NI in order to reveal the large-amplitude molecular motion. The DSC transitions are confirmed by changes in the chemical shifts, but additional, more continuous changes are seen. Condis-crystalline phases are probable for the latter two salts. Room-temperature X-ray diffraction on various iodides shows that the appropriate d-spacings increase linearly with size of the alkyl groups.

Structure and location of the organic base in zeolite EU-1 by 13C CP- MAS n.m.r.

Differential thermal analysis and high-resolution solid state 13C CP-MAS n.m.r. studies of EU-1 zeolite containing dibenzyldimethylammonium ion reveal that three to four molecules of the organic cation per unit cell are present, and chemically intact, in the zeolite. A configuration of the organic ions in which the phenyl rings are located inside the side pockets seems plausible. An apparent fit between the configuration of the guest organic molecule and the shape of the intracrystalline void in the zeolite suggests a templating role for the former.

Intercalation of 2-aminoethylferrocene into the layered host lattices MoO3, 2H-TaS2and α-Zr(HPO4)2·H2O

The amino-functionalised ferrocene derivative FcCH2CH2NH2[Fc = Fe(η-C5H4)(η-C5H4)] has been intercalated under mild conditions into both single-crystal and microcrystalline samples of the layered host lattices MoO3, 2H-TaS2, and α-Zr(HPO4)2·H2O. The X-ray powder patterns for the new intercalates have been indexed and yield interlayer lattice expansions of 13.09, 5.89 and 14.54 Å, respectively. The large interlayer expansions of 13.09 and 14.5 Å observed for the intercalates of both MoO3 and α-Zr(HPO4)2·2H2O suggest the formation of a bilayer of guest molecules within these host lattices. The 57Fe Mössbauer spectrum of MoO3(FcCH2CH2NH2)0.36 exhibits a quadrupole doublet with an isomer shift δFe= 0.442 mm s–1 and quadrupole splitting Δ= 2.344 mm s–1, indicating the presence of unoxidised ferrocene molecules within the oxide layers. Solid-state 13C CP-MAS NMR spectra of MoO3(FcCH2CH2NH2)0.36 are consistent with the existence of both neutral FcCH2CH2NH2 and FcCH2CH2NH3+ moieties within the host. In addition, the changes in the electronic structure of MoO3 that accompany the interacalation of FcCH2CH2NH2 have been investigated by solid-state photoelectron spectroscopy.

Changes in organic components for fallen logs in old-growth Douglas-fir forests monitored by 13C nuclear magnetic resonance spectroscopy

13C cross-polarization magic-angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy was used to characterize heartwood from decaying fallen boles of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco), western hemlock (Tsugaheterophylla (Raf.) Sarg.), and western red cedar (Thujaplicata Donn). The sample decay classes I to V had been previously assigned based on field observations. Solid-state 13C CPMAS NMR spectra were analyzed to determine the proportion of C of the following chemical types: carbohydrate, lignin, aliphatic, and the sum of carboxyl plus carbonyl. For both Douglas-fir and western hemlock, the proportion of carbohydrate C increased slightly in the early stages of decay. This was followed by a substantial increase in lignin C, while carbohydrate C declined to about 10% of total C. By contrast, the spectra for western red cedar generally showed little change with increasing decay class. One exceptional sample of western red cedar class IV was highly decomposed, indicating complete loss of carbohydrate C, and some loss of lignin side-chain C. For all three species, signals from alkyl and carbonyl C were weak, but tended to increase slightly with decomposition, most likely because of the selective preservation of waxes and resins (alkyl C), and oxidation. Accumulation of chitin was not observed, and there was little evidence for lignin decomposition or for formation of humic polymers. 13C CPMAS NMR offers a simple and information-rich alternative to wet chemical analyses to monitor changes in organic components during decomposition of woody litter.

Solid-state NMR Studies of Functional Group Recognition in Channel Inclusion Compound Formation

Abstract Solid-state 13C CP-MAS NMR spectra of urea inclusion compounds of methyl undecanoate (MUDA) show a significant bias in the relative alignment of guest molecules in the channels. In these spectra, asymmetric doublets are observed for C11 and methoxy carbons, while bands from internal carbons, including the carbonyl carbon, are unsplit. Band doubling is caused by differences in nearest neighbors, as shown by comparison with spectra of symmetric analogs, such as dimethyl sebacate/urea. During crystal formation of MUDA/urea from methanol, head to tail alignment is favored over head to head (plus tail to tail) alignment by a factor of 1.27±0.06, as shown by simulation of C11 resonances for spectra taken with a wide variety of cross polarization contact times. Adsorption of the ester group onto the growing face of the inclusion compound crystal probably gives rise to the observed bias.

A study of titanium and magnesium chloride complexes with dialkyl phthalates by solid state 13C CP MAS NMR spectroscopy

A series of dialkyl phthalate complexes with magnesium chloride and titanium(IV) chloride has been prepared and characterised by 13C CP MAS NMR spectroscopy. The isotropic chemical shift of the ester carbonyl group did not allow co-ordination to magnesium or titanium to be distinguished in general.

Mobility and hydrogen distribution in coal as revealed by polarization inversion in high-resolution solid state 13C [formula omitted] n.m.r.

A polarization inversion method was employed to study the nature of coal by high-resolution solid-state 13C CP MAS n.m.r. Comparison with synthetic polymers allowed evaluation of the relative molecular mobility of individual functional groups in coal samples. Some possible applications of the method in coal characterization for conversion processes are suggested.

Solid state 13C CP-MAS NMR spectra of iron (alkyne) carbonyl compounds

The solid state 13C NMR spectra of a series of iron (alkyne) carbonyl complexes, enriched in 13C at the carbonyl groups, have been obtained using 13C-{ 1H} cross-polarisation (CP) and slow magic angle spinning (MAS). In general, more resonances are observed from the solid state than from samples in solution; this may be due either to crystal packing effects lifting the degeneracy of certain signals or to a slowing of carbonyl fluxionality in the solid state. The intensities of the spinning side bands in the 13C spectra have been used to derive values for the components of the 13C shielding tensor. The component of the shielding tensor assigned to the CO bond axis (σ 33) is sensitive to the bonding of the CO group, i.e. whether it is a terminal or asymmetrically bridging group.

Carbon-13 NMR and chemical characterization of particle-size separates of peats differing in degree of decomposition

Solid-state 13C CPMAS NMR was used to examine particle-size fractions of six peats varying in degree of decomposition. With decreasing particle size, the chemical shift region attributed to O-substituted carbon decreased relative to that of aliphatic carbon, while changes in the aromatic, phenolic and carboxyl regions were small. These effects were similar to those previously seen with increasing decomposition with depth, and were more pronounced for the more decomposed peats. They were also consistent with chemical indications of increased decomposition in the smaller particle size fractions. It was also noted that carbohydrate content determined by chemical analysis was considerably lower than indicated by the relative intensity of the O-substituted region of the spectra (60–105 ppm). Principal component and factor analysis were applied to the NMR and pyrophosphate data. The principal components so derived reflected the empirical observations noted, but provide a more objective means of sample comparison.

ChemInform Abstract: A Variable‐Temperature Solid‐State 13C CPMAS NMR Analysis of meso‐Tetrapropylporphyrin and of Octaethylporphyrin.

ChemInformVolume 19, Issue 49 Physical Organic Chemistry ChemInform Abstract: A Variable-Temperature Solid-State 13C CPMAS NMR Analysis of meso-Tetrapropylporphyrin and of Octaethylporphyrin. L. FRYDMAN, L. FRYDMAN Fac. Farm. Bioquim., Univ. Buenos Aires, Buenos Aires 1113, Argent.Search for more papers by this authorA. C. OLIVIERI, A. C. OLIVIERI Fac. Farm. Bioquim., Univ. Buenos Aires, Buenos Aires 1113, Argent.Search for more papers by this authorL. E. DIAZ, L. E. DIAZ Fac. Farm. Bioquim., Univ. Buenos Aires, Buenos Aires 1113, Argent.Search for more papers by this authorA. VALASINAS, A. VALASINAS Fac. Farm. Bioquim., Univ. Buenos Aires, Buenos Aires 1113, Argent.Search for more papers by this authorB. FRYDMAN, B. FRYDMAN Fac. Farm. Bioquim., Univ. Buenos Aires, Buenos Aires 1113, Argent.Search for more papers by this author L. FRYDMAN, L. FRYDMAN Fac. Farm. Bioquim., Univ. Buenos Aires, Buenos Aires 1113, Argent.Search for more papers by this authorA. C. OLIVIERI, A. C. OLIVIERI Fac. Farm. Bioquim., Univ. Buenos Aires, Buenos Aires 1113, Argent.Search for more papers by this authorL. E. DIAZ, L. E. DIAZ Fac. Farm. Bioquim., Univ. Buenos Aires, Buenos Aires 1113, Argent.Search for more papers by this authorA. VALASINAS, A. VALASINAS Fac. Farm. Bioquim., Univ. Buenos Aires, Buenos Aires 1113, Argent.Search for more papers by this authorB. FRYDMAN, B. FRYDMAN Fac. Farm. Bioquim., Univ. Buenos Aires, Buenos Aires 1113, Argent.Search for more papers by this author First published: December 6, 1988 https://doi.org/10.1002/chin.198849040AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume19, Issue49December 6, 1988 RelatedInformation

High resolution solid-state 13C CPMAS study of neutral and partially oxidized aluminium polyfluorophthalocyanines

This paper reports a high resolution solid-state 13C CPMAS study of the low dimensional phthalocyanine (Pc = C 32H 16N 8) conductors (PcAlF)-(MoF 6) 0.38, (PcAlF)(IF 5) 0.43 and (PcAlF)(XeF 2) 0.35 as well as the precursor (PcAlF) n . This study confirms that the stacking configuration of Pc rings along polymeric chains of neutral polymer is eclipsed. The four inequivalent carbon sites resulting from this structure are clearly separate and identified. From this study it is concluded that intrachain disorder is more extended in MoF 6- and IF 5-doped compounds than in the XeF 2-doped one.

COMPARISON OF 13C CPMAS NMR AND CHEMICAL TECHNIQUES FOR MEASURING THE DEGREE OF DECOMPOSITION IN VIRGIN AND CULTIVATED PEAT PROFILES

Solid-state 13C CPMAS NMR was used to examine organic soils from virgin, 5-yr and 15-yr cultivated sites. In agreement with previous studies using other techniques, the chemical effects of cultivation were essentially confined to the plough layer. Cultivated sites had less carbohydrate, and increased lipid and methoxyl carbon; these changes were similar to those found with depth, due to natural decomposition. Changes in aromatic and phenolic carbon with depth or years of cultivation were small. When the NMR data were compared with other indicators of decomposition, there were no correlations between the pyrophosphate index and NMR parameters. Rubbed fiber correlated positively with carbohydrate, and negatively with lipid. This study supports the use of rubbed fiber as a routine indicator of the degree of decomposition, and the use of 13C CPMAS NMR for elucidating chemical changes in organic soils. It also illustrates the need to separate more clearly chemical changes occurring during decomposition or cultivation, from purely physical changes due to drying, compaction, and particle size diminution. Key words: 13C NMR, degree of composition, peat profile, organic soils

Raman and Solid State NMR Study on an Inclusion Compound of Aspartame with Cyclodextrin

Abstract A crystal of inclusion compound of Aspartame (α-l-aspartyl-l-phenylalanine methyl ester, APM) with β-cyclodextrin (β-CD) was obtained from their aqueous solution. The Raman spectrum of this crystal indicates some differences from the spectral sum of APM and β-CD. An analysis of these spectral differences suggests that the phenyl moiety of APM is included in the cavity of β-CD in the inclusion compound. In addition, a Raman spectroscopic study of APM with 15N-substitution and N-deuteration indicates that the peptide backbone of APM undergoes some conformational change on APM going into the inclusion compound. Solid state 13C CP MAS- and gated-decoupling MAS–NMR spectra for the inclusion compound indicate that the phenyl ring rotates at a higher frequency than 270 MHz, that the Phe Cβ and phenyl ring Cl move at the frequency of about 270 MHz, and that the molecular motion of the other parts of APM occurs at lower frequency than 270 MHz.