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Nuclear Quadrupole Resonance Spectroscopy: Tautomerism and Structure of Functional Azoles. CRYSTALS 2019. [DOI: 10.3390/cryst9070366] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Nuclear Quadrupole Resonance spectroscopy data of functionalized azoles (imidazoles, triazoles and corresponding benzazoles) are reviewed and critically discussed. The possibility of studying the tautomerism of azoles by the NQR method is considered.
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Mamadazizov S, Shelyapina MG, Kupriyanova GS, Mozzhukhin GV. New assignment of 14N NQR spectral lines for tetrazoles derivatives. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.03.030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Tahan A. Theoretical study addressing the effects of tautomerism and explicit/implicit water molecules on NQR and NMR parameters of tetrazole-5-thione. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2017; 55:606-618. [PMID: 27930819 DOI: 10.1002/mrc.4560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Revised: 11/24/2016] [Accepted: 11/30/2016] [Indexed: 06/06/2023]
Abstract
DFT/B3LYP calculations were employed to study the effects of tautomerism and explicit/implicit water molecules on Nuclear Quadrupole Resonance (NQR) and Nuclear Magnetic Resonance (NMR) tensors of nitrogen nuclei in tetrazole-5-thione structure. The obtained results revealed that nuclear quadrupole coupling constant (χ) and isotropic chemical shielding (σiso ) values of nitrogen nuclei in tetrazole ring of five possible tautomeric forms of tetrazole-5-thione, i.e. two thione forms called tautomers A and E and three thiol forms called tautomers B, C, and D, were functions of resonance energy(E2 ) values of nitrogen lone pairs. Furthermore, it was observed that by increasing participation of lone pairs of nitrogen atoms in the ring resonance interactions, the σiso values around them were increased, while their χ and qzz values were decreased. However, the results indicated that with exception of tautomer B, the order of qzz and χ values of nitrogen nuclei in tetrazole ring was exactly opposite of the order of resonance energy values for the same nitrogen nuclei in all tautomers and their mono-hydrated complexes. In addition, a significant decrease was noticed in χ and qzz values when a water molecule was put in different positions near the tetrazole ring in tautomers A-E. The mentioned result can be attributed to hydrogen bond formation between nitrogen nuclei and the oxygen of water. In mono-hydrated complexes, the σiso values around nitrogen atoms acting as hydrogen donors in hydrogen bond formation (N-H….OH2 ) were decreased, while its values were increased for nitrogen atoms acting as hydrogen acceptors in hydrogen bond formation(N….H-OH). Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Arezoo Tahan
- Semnan Branch, Islamic Azad University, Semnan, Iran
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Gregorovič A. 14N NQR lineshape in nanocrystals: An ab initio investigation of urea. J Chem Phys 2017; 146:194306. [PMID: 28527464 DOI: 10.1063/1.4983484] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
14N nuclear quadrupole resonance (NQR) lineshapes mostly contain information of low interest, although in nanocrystals they may display some unexpected behaviour. In this work, we present an ab initio computational study of the 14N NQR lineshapes in urea nanocrystals as a function of the nanocrystal size and geometry, focusing on the surface induced broadening of the lineshapes. The lineshapes were obtained through a calculation of the electric field gradient for each nitrogen site in the nanocrystal separately, taking into account the individual crystal field by embedding the molecule of interest in a suitable lattice of point multipoles representing other urea molecules in the nanocrystal. The small influence of distant molecules is found with a series expansion, using the in-crystal Sternheimer shieldings which we also calculated ab initio. We have considered nanocrystals with two geometries: a sphere and a cube, with characteristic sizes between 5 and 100 nm. Our calculations suggest that there is a dramatic difference between the linewidths for the two geometries. For spheres, we find a steep drop in linewidths at ∼10 nm; at 5 nm the linewidth is ∼11 kHz, whereas for sizes above 20 nm the linewidth is practically negligible (<100 Hz). For cubes, on the other hand, we find a steady 1/size decrease, from 12 kHz at 10 nm to 1.2 kHz at 100 nm. This analysis is important for 14N NQR spectroscopy of crystalline pharmaceuticals, where nanoparticles are increasingly more often embedded in some sort of matrix. Although this is only a theoretical analysis, we believe that this work can serve as a guidance for the forthcoming experimental analysis.
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Affiliation(s)
- Alan Gregorovič
- Institute "Jožef Stefan," Jamova 39, 1000 Ljubljana, Slovenia
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Gregorovič A. Quantitative Analysis of Hydration Using Nitrogen-14 Nuclear Quadrupole Resonance. Anal Chem 2015; 87:6912-8. [PMID: 26008906 DOI: 10.1021/acs.analchem.5b01492] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hydration is a quite common process in pharmaceutical solids. Sometimes it is desirable, as it stabilizes the crystal structure; in other cases it is unwanted, as it changes the physical and chemical properties of drugs. We here use (14)N NQR spectroscopy to quantitatively analyze hydration of a model compound, 5-aminotetrazole. (14)N NQR has some great advantages compared to other routinely used techniques to study hydration, like a very simple spectrum, single point calibration, and no need for special sample preparation, but the method's great disadvantage is a rather small sensitivity. Nevertheless, here we demonstrate that (14)N NQR, although being significantly less sensitive than XRD, NIR, and also (35)Cl NQR, is still capable of providing excellent quantitative accuracies. We can achieve errors <1% of the total amount, provided good temperature stabilization is implemented, which then allows long experimental times. We also present results obtained with a SLSE pulse sequence, which is a less robust approach but allows the use of much shorter measuring times (∼200×) and could be used for quantitative real time monitoring of hydration or dehydration.
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Affiliation(s)
- Alan Gregorovič
- Institute "Jožef Stefan", Jamova 39, 1000 Ljubljana, Slovenia
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Lavrič Z, Pirnat J, Lužnik J, Puc U, Trontelj Z, Srčič S. (14) N nuclear quadrupole resonance study of piroxicam: confirmation of new polymorphic form V. J Pharm Sci 2015; 104:1909-1918. [PMID: 25776345 DOI: 10.1002/jps.24421] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Revised: 12/09/2014] [Accepted: 02/13/2015] [Indexed: 11/11/2022]
Abstract
A new polymorphic crystal form of piroxicam was discovered while preparing crystalline samples of piroxicam for (14) N nuclear quadrupole resonance (NQR) analysis. The new crystal form, designated as V, was prepared by evaporative recrystallization from dichloromethane. Three known polymorphic forms (I, II, and III) were also prepared. Our aim was to apply (14) N NQR to characterize the new polymorphic form of piroxicam and compare the results with those of the other known polymorphic forms. Additional analytical methods used for characterization were X-ray powder diffraction (XRPD), thermal analysis, and vibrational spectroscopy. For the first time, a complete set of nine characteristic (14) N NQR frequencies was found for each prepared polymorph of piroxicam. The consistent set of measured frequencies and calculated characteristic quadrupole parameters found for the new polymorphic form V is a convincing evidence that we are dealing with a new form. The already known piroxicam polymorphic forms were characterized similarly. The XRPD results were in accordance with the conclusions of (14) N NQR analysis. The performed study clearly demonstrates a strong potential of (14) N NQR method to be applied as a highly discriminative spectroscopic analytical tool to characterize polymorphic forms.
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Affiliation(s)
- Zoran Lavrič
- Faculty of Pharmacy, University of Ljubljana, Ljubljana SI-1000, Slovenia.
| | - Janez Pirnat
- Institute of Mathematics, Physics and Mechanics, Ljubljana SI1000, Slovenia
| | - Janko Lužnik
- Institute of Mathematics, Physics and Mechanics, Ljubljana SI1000, Slovenia
| | - Uroš Puc
- J. Stefan International Postgraduate School, Ljubljana, and Faculty of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia
| | - Zvonko Trontelj
- Institute of Mathematics, Physics and Mechanics, Ljubljana SI1000, Slovenia
| | - Stane Srčič
- Faculty of Pharmacy, University of Ljubljana, Ljubljana SI-1000, Slovenia
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Beguš S, Jazbinšek V, Pirnat J, Trontelj Z. A miniaturized NQR spectrometer for a multi-channel NQR-based detection device. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2014; 247:22-30. [PMID: 25233110 DOI: 10.1016/j.jmr.2014.08.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 08/01/2014] [Accepted: 08/02/2014] [Indexed: 06/03/2023]
Abstract
A low frequency (0.5-5 MHz) battery operated sensitive pulsed NQR spectrometer with a transmitter power up to 5 W and a total mass of about 3 kg aimed at detecting (14)N NQR signals, predominantly of illicit materials, was designed and assembled. This spectrometer uses a standard software defined radio (SDR) platform for the data acquisition unit. Signal processing is done with the LabView Virtual instrument on a personal computer. We successfully tested the spectrometer by measuring (14)N NQR signals from aminotetrazole monohydrate (ATMH), potassium nitrate (PN), paracetamol (PCM) and trinitrotoluene (TNT). Such a spectrometer is a feasible component of a portable single or multichannel (14)N NQR based detection device.
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Affiliation(s)
- Samo Beguš
- University of Ljubljana, Faculty of Electrical Engineering, Ljubljana, Slovenia
| | - Vojko Jazbinšek
- Institute of Mathematics, Physics and Mechanics, University of Ljubljana, Ljubljana, Slovenia
| | - Janez Pirnat
- Institute of Mathematics, Physics and Mechanics, University of Ljubljana, Ljubljana, Slovenia
| | - Zvonko Trontelj
- Institute of Mathematics, Physics and Mechanics, University of Ljubljana, Ljubljana, Slovenia.
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Gregorovič A, Apih T. WURST-QCPMG sequence and "spin-lock" in ¹⁴N nuclear quadrupole resonance. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 233:96-102. [PMID: 23793057 DOI: 10.1016/j.jmr.2013.05.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 05/17/2013] [Accepted: 05/20/2013] [Indexed: 06/02/2023]
Abstract
¹⁴N nuclear quadrupole resonance (NQR) is a promising method for the analysis of pharmaceuticals or for the detection of nitrogen based illicit compounds, but so far, the technique is still not widely used, mostly due to the very low sensitivity. This problem is already acute in the preliminary NQR stage, when a compound is being examined for the first time and the NQR frequencies are being searched for, by scanning a wide frequency range step-by-step. In the present work, we experimentally show how to increase the efficiency of this initial stage by using a combination of a wideband excitation achieved with frequency swept pulses (WURST) and a "spin-lock" state obtained with a quadrupolar-CPMG (QCPMG) sequence. In the first part we show that WURST pulses provide a much larger excitation bandwidth compared to common rectangular pulses. This increased bandwidth allows to increase the frequency step and reduces the total number of steps in a scanning stage. In the second part we show that the "spin-lock" decay time T2eff obtained with the WURST-QCPMG combination is practically identical with the T2eff obtained with the most common "spin-lock" sequence, the SLSE, despite a very different nature and length of excitation pulses. This allows for a substantial S/N increase through echo averaging in every individual step and really allows to exploit all the advantages of the wider excitation in the NQR frequency scanning stage. Our experimental results were obtained on a sample of trinitrotoluene, but identical behavior is expected for all compounds where a "spin-lock" state can be created.
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Affiliation(s)
- Alan Gregorovič
- Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia.
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Hu J, Wang J, Zhou T, Xu Y. Microwave-Assisted Synthesis of Tetrazolyl Pyrazole Amides. JOURNAL OF CHEMICAL RESEARCH 2011. [DOI: 10.3184/174751911x13149561530439] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A rapid and efficient microwave-assisted synthesis N-(1H-tetrazol-5-yl) derivatives of 3-methyl-1-phenyl-1H-pyrazole-5-carboxamide is described. These tetrazole pyrazole amides have interesting bacteriocidal, pesticidal, herbicidal and antimicrobial activities. They were identified by IR and 1H NMR elemental analyses. The target compounds were obtained in a shorter reaction time compared to conventional heating methods.
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Affiliation(s)
- Jun Hu
- College of Environment, Nanjing University of Technology/ Jiangsu Key Laboratory of Industrial water-Conservation & Emission Reduction, Nanjing 210009, P. R. China
| | - Jikui Wang
- College of Sciences, Nanjing University of Technology, Nanjing 210009, P. R. China
| | - Taoyu Zhou
- College of Environment, Nanjing University of Technology/ Jiangsu Key Laboratory of Industrial water-Conservation & Emission Reduction, Nanjing 210009, P. R. China
| | - Yanhua Xu
- College of Environment, Nanjing University of Technology/ Jiangsu Key Laboratory of Industrial water-Conservation & Emission Reduction, Nanjing 210009, P. R. China
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Luznik J, Jazbinsek V, Pirnat J, Seliger J, Trontelj Z. Zeeman shift--a tool for assignment of 14N NQR lines of nonequivalent 14N atoms in powder samples. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2011; 212:149-153. [PMID: 21783395 DOI: 10.1016/j.jmr.2011.06.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Revised: 05/30/2011] [Accepted: 06/23/2011] [Indexed: 05/31/2023]
Abstract
The use of Zeeman perturbed 14N nuclear quadrupole resonance (NQR) to determine the ν+ and ν-14N lines in polycrystalline samples with several nonequivalent nitrogen atoms was investigated. The 14N NQR line shift due to a weak external Zeeman magnetic field was calculated, assuming isotropic distribution of EFG tensor directions. We calculated the broad line distribution of the ν+ and ν- line shifts and experimentally confirmed the calculated Zeeman field dependence of singularities (NQR peaks) in cyclotrimethylenetrinitramine (RDX) and aminotetrazole monohydrate (ATMH). The calculated and measured frequency shifts agreed well. The proposed measurement method enabled determination of which 14N NQR lines in ATMH belong to ν+ and which to ν- transitions.
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Affiliation(s)
- J Luznik
- Institute of Mathematics, Physics and Mechanics, Jadranska 19, 1000 Ljubljana, Slovenia
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Seliger J, Žagar V, Latosińska JN. 14N NQR, 1H NMR and DFT/QTAIM study of hydrogen bonding and polymorphism in selected solid 1,3,4-thiadiazole derivatives. Phys Chem Chem Phys 2010; 12:13007-19. [DOI: 10.1039/c0cp00195c] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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