CPMAS NMR Spectra Research Articles

Characterization of photo-intermediates in the photo-reaction pathways of a bacteriorhodopsin Y185F mutant using in situ photo-irradiation solid-state NMR spectroscopy.

Photo-reaction pathways of a bacteriorhodopsin Y185F mutant were examined using in situ photo-irradiation solid-state NMR spectroscopy. (13)C CP MAS NMR spectra were recorded at -40 °C in the dark (D1), under irradiation with 520 nm light (L1), subsequently in the dark (D2), and again under irradiation with 520 nm light (L2). In the process from D1 to L1, the 13-cis, 15-syn (CS; bR548) state changed to a CS*- (13-cis, 15-syn) intermediate, which was highly stable at -40 °C, and the all-trans (AT; bR568) state transformed to an N-intermediate. Under the D2 conditions, the N-intermediate transformed to an O-intermediate, which was highly stable at -40 °C in the dark. During subsequent irradiation with 520 nm light (L2), the O-intermediate transformed to the N-intermediate through the AT state, whereas the CS*-intermediate did not change. The CS*-intermediate was converted to the AT state (or O-intermediate) after the temperature was increased to -20 °C. Upon subsequent increase of the temperature to 20 °C, the AT state (or O-intermediate) was converted to the CS state until reaching equilibrium. In this experiment, the chemical shift values of [20-(13)C, 14-(13)C]retinal provided the 13C[double bond, length as m-dash]C and 15C[double bond, length as m-dash]N configurations, respectively. From these data, the configurations of the AT and CS states and the CS*-, N-, and O-intermediates were determined to be (13-trans, 15-anti), (13-cis, 15-syn), (13-cis, 15-syn), (13-cis, 15-anti), and (13-trans, 15-anti), respectively. (13)C NMR signals of the CS*- and O-intermediates were observed for the first time for the Y185F bR mutant by in situ photo-irradiation solid-state NMR spectroscopy and the configuration of the CS*-intermediate was revealed to be significantly twisted from that of the CS state although both were assigned as (13-cis, 15-syn) configurations.

Structural and spectroscopic studies of bis(2-amino-6-methylpyrimidinium-4-(1H)-one) aquapentachloridoindate(III) monohydrate

Physico-chemical properties of a new organic indate(III) (C5H8N3O)2[InCl5(H2O)].H2O are discussed on the basis of its X-ray crystal structure investigation. The asymmetric unit includes two independent 2-amino-6-methylpyrimidinium-4-(1H)-one cations, one aquapentachloridoindate dianion, and one crystallization water molecule. The InIII ion is in a slightly distorted octahedral coordination geometry. In the crystal structure, the dimeric species formed by two metal complexes and two water molecules are connected to the 2-amino-6-methylpyrimidin-4-1H)-one cations through N–H⋯Cl hydrogen bonds to build 2D sheets parallel to the (b, a + c) plane. The 13C and 15N CP-MAS NMR spectra are in agreement with the X-ray structure. The vibrational absorption bands were identified by infrared spectroscopy. DFT calculations allowed attributions of NMR signals and of the IR bands.

Synthesis and Physico-Chemical Studies of a New Noncentrosymmetric Bis[N-(2-hydroxyethyl)piperazine-1,4-diium] Tetrakis(hydrogen oxalate) Trihydrate: [C6H16N2O]2(HC2O4)4·3H2O

The new noncentrosymmetric oxalate with the general formula [C6H16N2O]2(HC2O4)4·3H2O, has been synthesized and single crystals were grown from aqueous solution by slow evaporation technique. Single crystal X-ray diffraction study on grown crystal reveals that they belong to triclinic system with space group P1. The unit cell dimensions are: a = 5.688(2) A, b = 8.315(2) A, c = 16.634(3) A, α = 96.63(2)°, β = 99.81(3)°, γ = 110.01(2)° with V = 715.4(3) A3 and Z = 1. The structure has been solved using a direct method and refined to a reliability R factor of 0.052. The structure is built up from anionic chains parallel to the a-axis. These chains are interconnected by the organic cations and water molecules via hydrogen bonds so as to build a three dimensional arrangement. FT-IR spectrum confirms the presence of the functional groups in the synthesized material. The 13C CP-MAS NMR spectrum is in agreement with the X-ray structure. UV–Vis spectrum indicates that the crystal is transparent in UV and visible region with a lower cutoff wavelength of 212 nm. The DSC curve indicates that the crystal is thermally stable up to 330 K. The molecular structure of bis(N-(2-hydroxyethyl)piperazine-1,4-diium) Tetrakis(hydrogen oxalate) Trihydrate is formed by N-(2-hydroxyethyl)piperazine-1,4-diium cations, oxalate anions and water molecules held together by means of N–H⋯O, C–H⋯O, O–H⋯OW and OW–H⋯OW(O) hydrogen bonds to form three-dimensional network.

Synthesis, crystal structure and vibrational spectroscopic analysis of tetrakis(5-amino-1-H-1,2,4-triazol-4-ium) decachlorodibismuthate(III):[C2H5N4]4Bi2Cl10

Physico-chemical properties of a new organic bismuthate(III), [C2H5N4]4Bi2Cl10 are discussed on the basis of X-ray crystal structure investigation. This compound crystallizes in the monoclinic space group C2/c, with a=16.3622(3), b=12.7941(2), c=14.8178(2)Å, β=98.5660(10)°, V=3067.35(8)Å3 and Z=4. The crystal structure consists of discrete binuclear [Bi2Cl10]4− anions and 3-amino-1-H-1,2,4-triazolium cations. The crystal packing is governed by strong NH⋯N and weak NH⋯Cl hydrogen bonds and Π–Π stacking interactions to form three-dimensional network. The 13C CP-MAS NMR spectrum is in agreement with the X-ray structure. The infrared study confirms the presence of the organic cation [C2H5N4]+. The vibrational absorption bands were identified by infrared spectroscopy and DFT calculations allowed their attribution.

Chemical and nutritional analysis of seeds from purple and white açaí (Euterpe oleracea Mart.)

Seeds from the purple and the white fruit produced by the Amazonian palm, Euterpe oleracea Mart., commonly called “açai”, were analyzed by solid state 1H-decoupled 13C CPMAS and MAS NMR, solution NMR and LC–MS/MS. The goal was to distinguish the seeds from each colored fruit and determine their spectra for the first time. The seeds of each variety contained primarily glycosidic carbons, due to their cellulose and hemicellulose content. They also contained carbons due to CO, CC, as well as aliphatic carbons. The insoluble fiber found in açaí pulp is distinguishable from the seed of the fruit by its unique solid state 1H-decoupled 13C CPMAS NMR spectra. The seed also contains fats (0.22–0.33%) not previously reported. The seed contains a mixture of saturated and unsaturated fats. There are also 3.38–4.70% total methanolic extractables, with no detectable cyanidin 3-O-glucoside or cyanidin 3-O-rutinoside, unlike the pulp which contains both cyanidins. When the NMR spectra of the white and purple açaí seeds are compared, it was possible to observe differences between these two açaí varieties, as well as differences between the composition of pulp of the fruit and its seed.

Synthesis, crystal structure and characterization of a new organic–inorganic hybrid material: [C6H16N2O]SbCl5

The present paper undertakes the study of [C6H16N2O]SbCl5 which is a new hybrid compound. It is synthesized and characterized by single-crystal X-ray diffraction, thermal analysis, IR and solid state NMR spectroscopies. The centrosymmetric compound crystallizes in the monoclinic space group P21/n, with the following unit cell parameters: a=9.8519(2), b=8.8345(2), c=17.3087(4)Å, β=102.3(1)° and Z=4. The atomic arrangement shows an alternation of organic and inorganic entities. The cohesion between these entities is performed via N–H⋯Cl and O–H⋯Cl hydrogen bonding to form a three-dimensional network. The 13C CP-MAS NMR spectrum is in agreement with the X-ray structure. Infrared and Raman spectra at room temperature are recorded in the 4000–400 and 500–100cm−1 frequency regions respectively. This study confirms the presence of the organic cation [C6H16N2]2+ and of the [SbCl5]2− anion. DFT calculations allow the attribution of the carbon peaks to the different atoms.

Oligomeric complexes of some heteroaromatic ligands and aromatic diamines with rhodium and molybdenum tetracarboxylates: 13 C and 15 N CPMAS NMR and density functional theory studies

Seven new oligomeric complexes of 4,4'-bipyridine; 3,3'-bipyridine; benzene-1,4-diamine; benzene-1,3-diamine; benzene-1,2-diamine; and benzidine with rhodium tetraacetate, as well as 4,4'-bipyridine with molybdenum tetraacetate, have been obtained and investigated by elemental analysis and solid-state nuclear magnetic resonance spectroscopy, (13)C and (15)N CPMAS NMR. The known complexes of pyrazine with rhodium tetrabenzoate, benzoquinone with rhodium tetrapivalate, 4,4'-bipyridine with molybdenum tetrakistrifluoroacetate and the 1 : 1 complex of 2,2'-bipyridine with rhodium tetraacetate exhibiting axial-equatorial ligation mode have been obtained as well for comparison purposes. Elemental analysis revealed 1 : 1 complex stoichiometry of all complexes. The (15)N CPMAS NMR spectra of all new complexes consist of one narrow signal, indicating regular uniform structures. Benzidine forms a heterogeneous material, probably containing linear oligomers and products of further reactions. The complexes were characterized by the parameter complexation shift Δδ (Δδ = δcomplex - δligand). This parameter ranged from around -40 to -90 ppm in the case of heteroaromatic ligands, from around -12 to -22 ppm for diamines and from -16 to -31 ppm for the complexes of molybdenum tetracarboxylates with 4,4'-bipyridine. The experimental results have been supported by a density functional theory computation of (15)N NMR chemical shifts and complexation shifts at the non-relativistic Becke, three-parameter, Perdew-Wang 91/[6-311++G(2d,p), Stuttgart] and GGA-PBE/QZ4P levels of theory and at the relativistic scalar and spin-orbit zeroth order regular approximation/GGA-PBE/QZ4P level of theory. Nucleus-independent chemical shifts have been calculated for the selected compounds.

Combined experimental and computational NMR study of crystalline and amorphous zeolitic imidazolate frameworks.

Zeolitic imidazolate frameworks (ZIFs) have attracted great interest in recent years due to their high chemical and thermal stability with promising applications in gas storage and separations. We investigate the structures of three different crystalline ZIFs - ZIF-4, ZIF-8, ZIF-zni - and their amorphous counterparts using high field (13)C and (15)N CP MAS NMR. The high field (20 T) allows for the observation of all crystallographically independent carbon and nitrogen atoms in the crystalline ZIFs. Combining our experimental results with density functional theory calculations enabled the assignment of all chemical shifts. The crystalline spectra reveal the potential of high field NMR to distinguish between two ZIF polymorphs, ZIF-4 and ZIF-zni, with identical [Zn(C3H3N2)2] chemical compositions. (13)C and (15)N CP MAS NMR data obtained for the amorphous ZIFs clearly showed signal broadening upon amorphization, confirming the retention of chemical composition and the structural similarity of amorphous ZIF-4 and ZIF-zni. In the case of amorphous ZIF-8, we present evidence for the partial de-coordination of the 2-methyl imidazole linker.

Synthesis, structure and characterization of two new Zn(II) and Cd(II) complexes with the bidentate ligand 2-[(2-aminoethyl)amino]ethanaminium (AEEA)

Two new Zn(II) and Cd(II) complexes with the bidentate ligand 2-[(2-aminoethyl)amino]ethanaminium (AEEA), [ZnCl2(C4H14N3)]ClO4 (1) and [CdCl2(C4H14N3)]ClO4 (2), have been prepared and were characterized by single crystal X-ray diffraction, elemental analysis, CP–MAS-NMR and IR spectroscopies. The basic coordination patterns of the AEEA coordinated metal cations is highly distorted tetrahedral in (1) and distorted octahedral in (2). The crystal structure of (1) is characterized by ZnCl2N2 tetrahedra interconnected via N–H⋯Cl hydrogen bonds to form layers parallel to the (b, a+c) plane. In (2), the CdN2Cl4 entities form polymeric chains of edge-sharing octahedra extending along the a-axis direction. The crystal structures are stabilized by sets of hydrogen bonds, some of which are bi or trifurcated. The 13C and 15N CP–MAS NMR spectra are discussed and the vibrational absorption bands were identified by infrared spectroscopy.

Synthesis and physico-chemical studies of a novel noncentrosymmetric heptacoordinated cadmium(II) compound containing a tripodal amine, CdCl2[N(C2H6N)3

A new noncentrosymmetric Cd(II) complex with thetripodal amine tris(2-aminoethyl)amine, CdCl2[N(C2H6N)3]2, has been prepared and characterized by single crystal X-ray diffraction, solid state NMR and IR spectroscopies. In the complex, the Cd(II) ion is surrounded by sevennitrogen atoms. The organic molecule acts as both a tri-and a tetradentate ligand. The cationic complexes are linked to each other forming layers parallel to the (a, b)plan. The Cl- counter ions occupy the cavities created inside these layers. The 13C CP-MAS NMR spectra are in agreement with the X-ray structure. DFT calculations allow the attribution of the carbon peaks to the differentatoms.The vibrational absorption bands were identified by infrared spectroscopy and DFT calculations allowed their attributions.

Synthesis, structure and characterization of a new noncentrosymmetric Zn(II) complex with the 2-amino-5-chloropyridine ligand (AClPy)

A new noncentrosymmetric Zn(II) complex with the monodentate ligand 2-amino-5-chloropyridine (AClPy), ZnCl2(C5H5ClN2)2, has been prepared at room temperature and characterized by single crystal X-ray diffraction, 13C CP-MAS-NMR and IR spectroscopies. The basic coordination pattern of the AClPy coordinated metal cations is slighly distorted tetrahedral. The crystal structure is characterized by ZnCl2N2 tetrahedra interconnected via N-H···Cl hydrogen bonds generated by the NH2 amino group to form chains extending along the (a-c) direction. The exocyclic N atom is an electron receiving center, which is consistent with features of imino resonance as evidenced by bond lengths and angles. The crystal structure is stabilized by sets of intra and intermolecular hydrogen bonds. The 13C CP-MAS NMR spectrum is discussed and the vibrational absorption bands are identified by infrared spectroscopy and theoretical calculations.

Distinctive Spectral and Microscopic Features for Characterizing the Three-Dimensional Local Aluminosilicate Structure of Perlites

Expanded perlite and raw perlites of various origins were examined using solid-state NMR and Fourier transform infrared (FTIR) spectroscopies, as well as scanning electron microscopy, in an attempt to correlate the characteristics of aluminosilicate framework with the material’s expansion properties. The 27Al magic angle spinning (MAS) NMR spectra indicated that aluminum atoms in perlite are mainly tetrahedrally coordinated in Q4 structures not participating in the expansion process; two different octahedral Al species were also identified in perlite. Owing to the tetrahedra−octahedra transformations, perlite may be classified among the metastable materials. The 29Si MAS NMR and 1H–29Si CPMAS NMR spectra showed that Q3 and Q4 units are mostly abundant, a fact that explains the low cation exchange capacity of perlites. Deconvoluted FTIR and 29Si MAS NMR spectra are consistent regarding the relative Qn intensities which, together with the network geometry, determine the expansibility of raw perlites. The calculated variations of the Si–O–Si angle are more significant than those of the Si–O bond length, remarkably affecting the structure of the aluminosilicate network. Thus, perlite samples of increasingly fragmentary framework exhibit the highest expansion ratios. SEM micrographs monitored the expansion process differentiating between the low- and high-expansibility perlites.

Synthesis and physico-chemical studies of a novel organo-metallic compound CdCl2(C6H4FNH2)2

A new Cd(II) complex with the monodentate ligand 3-fluoroaniline, CdCl2(C6H4FNH2)2, has been prepared and characterized by single crystal X-ray diffraction, solid state NMR, IR, Raman and UV–visible spectroscopies. In the complex, the Cd(II) ion is surrounded by four chlorine atoms and two nitrogen atoms, forming a chain of edge-charing octahedra spreading along the a-axis direction. These chains are interconnected via NH…Cl hydrogen bonds to form inorganic layers parallel to the (a, b) plane. The organic 3-fluorophenyl groups are inserted between these layers and are interconnected via CH…F hydrogen bonds to perform an infinite three-dimensional network. Intermolecular π–π stacking interactions between neighboring aromatic rings are also observed with a face-to-face distance of 3.6816 (4)Å. The 13C and 19F CP-MAS NMR spectra are in agreement with the X-ray structure. DFT calculations allow the attribution of the carbon peaks to the different atoms. The absorption bands of the Cd2Cl4N2 units were identified by Raman spectroscopy. The solid-state UV–vis spectrum of the complex has been assigned to ligand and charge transfer transitions.

Physico-Chemical Studies of Tris (adamantan-1-aminium) Hexachlorostannate (IV) Chloride Monohydrate

The structural characteristics of organic ammonium salts of the hexahalogenostannates (IV) with a general formula (R-NH 3)3SnX 6 have not yet been studied extensively. In the course of investigating these types of materials, the title compound, a double salt of adamantan-1aminium chloride and hexahalogenostannate (IV), with the formula (C 10 H18 N) 3[SnCl 6]Cl·H 2O, was crystallized. Its asymmetric unit contains three independent cations of protonated adamantan-1-amine, one chloride anion, one Hexachlorostannate (IV) ion and a hydrate water molecule. The atomic arrangement can be described as inorganic SnCl 6 2- units isolated from each other by the organic cations, the chloride anions and the cocrystallized water molecules. The compound exhibits bifurcated and simple hydrogenbonding interactions between the ammonium groups, the water molecules and the chlorine atoms, with little variation in the hydrogen-bonding interactions. The 119 Sn, 13 C and 15 N CPMAS NMR spectra are in agreement with the X-ray structure.

Synthesis and physico-chemical studies of a novel bis [3,5-diamino-4H-1,2,4-triazol-1-ium] dichloride monohydrate

The title new compound, (C2H6N5+)2, 2Cl−.H2O, contains two 3,5-diamino-4H-1,2,4-triazol-1-ium cations, two chloride anions and one water molecule. The crystal structure is stabilized by O - H···Cl, N - H···Cl, N - H···O and N - H···N hydrogen bonds, one of them being a three-center interaction. Strong π - π stacking interactions between neighboring triazolium rings are present, with a centroid - centroid distance of 3.338 (7) Å. The exocyclic N atoms are sp2 hybridized, as evidenced by bond lengths and angles, in agreement with an enamine-imine tautomerism. A dielectric spectroscopic study of the title compound was performed. The 13C CP-MAS NMR spectrum is in agreement with crystallographic data. The infrared spectrum has been recorded at ambient temperature and interpreted on the basis of literature data. The temperature dependence of the imaginary part of the permittivity constant was analyzed with the Cole - Cole formalism in the temperature range 325 - 375 K.

Solid-state NMR structure characterization of a 13CO-Labeled Ir(I) complex with a P,N-donor ligand including ultrafast MAS methods.

The structural characterization of a (13)CO-labeled Ir(I) complex bearing an P,N-donor ligand (1-[2-(diphenylphosphino)ethyl]pyrazole), [Ir(PyP)((13)CO)Cl] is demonstrated using a series of tailored solid-state NMR techniques based on ultrafast (60 kHz) Magic Angle Spinning (MAS), which facilitates correlations with narrow proton line-widths. Our 1D (1)H MAS and 2D (13)C and (31)P CP-MAS NMR spectra provided structural information similar to that obtained using NMR spectroscopy in solution. We employed high-resolution 2D solid-state correlation spectroscopy ((1)H-(13)C HETCOR, (1)H-(31)P correlation) to characterize the networks of dipolar couplings between protons and carbon/phosphorus. (1)H-(1)H SQ-SQ correlation spectra showed the dipolar contacts between all protons in a similar fashion to its solution counterpart, NOESY. The use of the (1)H single quantum/double quantum experiments made it possible to observe the dipolar-coupling contacts between immediately adjacent protons. Additionally, internuclear (13)CO-(31)P distance measurements were performed using REDOR. The combination of all of these techniques made it possible to obtain comprehensive structural information on the molecule [Ir(PyP)((13)CO)Cl] in the solid state, which is in excellent agreement with the single crystal X-ray structure of the complex, and demonstrates the enormous value of ultrafast MAS NMR techniques for a broad range of future applications.

Synthesis, structure and characterization of a new cadmium(II) iodide containing a tetradentate tripodal amine

A cadmium(II) iodide compound of the [Cd(L)I]I series, with L = tris(2-aminoethyl)amine, is synthesized and characterized. X-ray structural study shows that the title compound has a slightly distorted trigonal bipyramidal environment where the CdN4I chromophore is bounded by N atoms of L and one iodide. In the structural arrangement, the [Cd(L)I]+ cationic complexes are interconnected via N-H···I hydrogen bonds generated by the uncoordinated I iodide anions to form layers parallel to the (a, c) plane. The 13C CP-MAS NMR spectrum is discussed and the vibrational absorption bands were identified by infrared spectroscopy and DFT calculations.

Synthesis and physico-chemical studies of a novel coordination compound ZnCl2(C6H4FNH2)2

A new Zn(II) complex with the monodentate ligand 3-fluoroaniline, ZnCl2(C6H4FNH2)2, has been prepared and characterized by single crystal X-ray diffraction, Solid state NMR, IR and UV-visible spectroscopies. The Zn(II) ion, located on a special position, is tetracoordinated by two nitrogen atoms of two 3-fluoroaniline monodentate ligands and two chlorine ligands. In the atomic arrangement, the ZnCl2(NH2)2 entities are interconnected via N-H…Cl hydrogen bonds to form inorganic layers parallel to the (b, c) plane. The organic 3-fluorophenyl groups are located between these layers and connect each other via C-H…F hydrogen bonds to perform an infinite three-dimensional network. The F atom of the 3-fluoroaniline ligand is disordered over two positions. An F-F interaction between neighboring fluorine atoms contributes also to the structure cohesion. The 13C and 15N CP-MAS NMR spectra are in agreement with the X-ray structure. DFT calculations allow the attribution of the carbon peaks to the different independent atoms. Solid-state UV-Vis spectrum of the complex has been assigned to ligand and charge transfer transitions.

Physico-chemical studies of a novel cadmium(II) coordination compound[(C6H9N2)2CdCl4]0.305H2O

The crystal structure of the title organic-inorganic hybrid material, [(C 6 H 9 N 2 ) 2 CdCl 4 ]0.305H 2 O, contains two crystallographically independent but chemically equivalent cadmium complexes with essentially the same geometry (rms deviation of all atoms: 0.152 A). The metal centers have a 6-coordinated octahedral geometry and both Cd atoms exhibit exact crystallographic inversion symmetry. Crystal packing is stabilized by intermolecular N-H...Cl hydrogen bonds that connect individual zwitter-ionic complexes into a three dimensional lattice, which is further stabilized through p-p stacking interactions between aromatic rings of neighboring complexes, with centroid to centroid distances of 3.4406(14) and 3.7022(13) A and interplanar separations of 3.299(1) and 3.302(1) A. Interstitial space is partially filled with water molecules which are connected to the network through O-H...Cl and C-H...O hydrogen bonds. The 13 C and 15 N CP-MAS NMR spectra are in agreement with the X-ray structure. Four resonance peaks for the C3 carbon atom are observed due to the different environments of the aromatic rings caused by the presence of 0.305 water molecule per unit cell. DFT calculations allow the attribution of the carbon and nitrogen peaks to the different atoms.

Short-term effects of sustainable agricultural practices for spring maize (Zea mays L.) production on soil organic carbon characteristics

The effects of the integrated adoption of several recommended sustainable agricultural practices (SAP) on maize grain yield and the quantitative and qualitative characteristics of soil organic carbon (SOC) were studied in 2 years, spring maize monoculture field plot experiment. The recommended agricultural practices included conservation tillage, combined application of organic manure and chemical fertilizers, and crop residue return. Compared with the conventional agricultural practices (CAP), the maize grain yield increased in the SAP treatment, and the difference between the two treatments was statistically significant (P<0.05) in the second season of the experiment (2010). The content of soil total organic carbon (TOC) and organic C fractions (that is, water soluble organic C, easily oxidizable organic C, particulate organic C, humus C and black C) were higher in the SAP than in the CAP treatment, although the differences between the two treatments were not significant. The relative intensities of O-alkyl C and carbonyl C and the aliphatic C / aromatic C ratio were higher, while the relative intensities of alkyl C and aromatic C and the ratios of alkyl C / O-alkyl C and hydrophobic C / hydrophilic C were lower in solid-state 13C CPMAS NMR spectra of HF-treated soils in the SAP than in the CAP treatment. The recommended sustainable agricultural practices were beneficial for the increase of maize grain yield and the improvement of the quantity and quality of SOC during a short-term period. Key words: Soil organic carbon, organic carbon fraction, agricultural practice, spring maize, 13C CPMAS NMR.