Ryszard NAZARSKI
@associate professor
Faculty of Chemistry
University of Lodz
RESEARCH, TEACHING, or OTHER INTERESTS
Physical and Theoretical Chemistry, Organic Chemistry, Spectroscopy, Computer Science Applications
Scopus Publications
Scopus Publications
Ryszard B. Nazarski
Wiley
AbstractThis study aimed to obtain the title spectra and verify the temperature dependence of δDSS of the HOD signal from D2O of the NMR sample. However, the analysis of the collected δX data, extended by the results of other closely related measurements reported in the literature, provided important guidelines for performing routine 1H/13C NMR spectra in aqueous solvents externally referenced to neat liquid TMS contained in a coaxial capillary. Therefore, it is recommended that the previously proposed correction of δX data thus determined, which is mainly due to the difference in volume magnetic susceptibility χv between the sample and the external standard used, usually called the bulk magnetic susceptibility (BMS) correction, has been increased by +0.05 ppm (7%). The new value of this correction, +0.73 ppm, based on NMR experiments carried out at a standard temperature of 25°C, was confirmed in a classical approach using critically reviewed χm, χM, and ρ data for TMS, D2O, and H2O. The BMS correction for H2O solutions is +0.75 ppm. Important issues concerning magnetic susceptibility measurements for D2O and H2O, coaxial bulb‐ended inserts, and the geometry of two‐tube NMR cells (shape factor αav) are also critically discussed here, partly from a historical perspective.
Ryszard B. Nazarski
MDPI AG
The quite popular, simple but imperfect method of referencing NMR spectra to residual 1H and 13C signals of TMS-free deuterated organic solvents (referred to as Method A) is critically discussed for six commonly used NMR solvents with respect to their δH and δC values that exist in the literature. Taking into account the most reliable data, it was possible to recommend ‘best’ δX values for such secondary internal standards. The position of these reference points on the δ scale strongly depends on the concentration and type of analyte under study and the solvent medium used. For some solvents, chemically induced shifts (CISs) of residual 1H lines were considered, also taking into account the formation of 1:1 molecular complexes (for CDCl3). Typical potential errors that can occur as a result of improper application of Method A are considered in detail. An overview of all found δX values adopted by users of this method revealed a discrepancy of up to 1.9 ppm in δC reported for CDCl3, most likely caused by the CIS mentioned above. The drawbacks of Method A are discussed in relation to the classical use of an internal standard (Method B), two ‘instrumental’ schemes in which Method A is often implicitly applied, that is, the default Method C using 2H lock frequencies and Method D based on Ξ values, recommended by the IUPAC but only occasionally used for 1H/13C spectra, and external referencing (Method E). Analysis of current needs and opportunities for NMR spectrometers led to the conclusion that, for the most accurate application of Method A, it is necessary to (a) use dilute solutions in a single NMR solvent and (b) to report δX data applied for the reference 1H/13C signals to the nearest 0.001/0.01 ppm to ensure the precise characterization of new synthesized or isolated organic systems, especially those with complex or unexpected structures. However, the use of TMS in Method B is strongly recommended in all such cases.
Gerhard Hägele, Ryszard B. Nazarski, Alexa Schmitz, Shanghua Xing, and Christoph Janiak
Informa UK Limited
Abstract S-n-alkyl-tetrahydrothiophenium cations [R-THT]+ in some iodide or tetraphenylborate ion-pairs [R-THT][X] (R = methyl to n-decyl, X−= I−, [BPh4]−, [NTf2]−) are characterized in the solid state by puckered THT rings in twist forms. In contrast, solution 1H NMR spectra of compounds [R-THT][X] indicate a rapid conformational exchange leading to dynamic [ABCD]2 spin systems due to eight protons of the THT ring. These strongly coupled spectra obtained at high magnetic fields were analyzed by iterative methods and simulated successfully. In addition, molecular modeling and gauge-including atomic orbitals (GIAOs) based calculations of proton NMR chemical shifts for two such ion-pair compounds in solution were performed at the density functional theory (DFT) level . As a result, conformational equilibrium between two different pairs of isoenergetic twist forms of the THT ring in [Me-THT][I] (global and local energy minima) was found to exist. These theoretical results are discussed in view of experimental 1H NMR spectral data. Graphical Abstract
Magdalena Ciechańska, Andrzej Jóźwiak, Ryszard B. Nazarski, and Ewa A. Skorupska
American Chemical Society (ACS)
The reaction of 2-aryl-3-hydroxyisoindolin-1-ones with the s-BuLi●TMEDA system in THF at -78oC, affording a series of diastereomeric 3-aminoindan-1-ones via a novel rearrangement of the isoindolinone scaffold, is reported. It is proposed that α-elimination of LiOH from the transient N,O-dilithiated hemiaminal carbenoids leads to the formation of singlet carbenes followed by their trapping via an internal C-H insertion. An alternative explanation based on an intramolecular Mannich reaction seems to be less probable. A mechanistic-type study that combines spectroscopic data of the products and calculation results, with a special focus on the diverse lithiated intermediates that are most likely to engage in the title process (particularly those with internal Li-bonds), is presented. The MP2 approach, involving also the NPA and QTAIM data, provided insight into structures and properties of all these species. Two reaction routes A and B appeared to be possible for the postulated carbene mechanism. An unusual metamorphosis of the CCN atom triad, from a near sp 1-azaallene-type in more stable non-carbene Li enolates to a roughly sp2 type in their carbene keto tautomers, is recognized in one of these pathways (route B). Dominant forms of resonance structures for the aforementioned tautomeric systems that have seven-membered quasi rings stabilized by Li+ ions bridging the N- and carbonyl O-atoms, are indicated. Large computational difficulties arising from a huge impact of internal Li+ complexation on conformational preferences and electronic properties of carbonyl group-bearing lithium derivatives are also discussed. The new γ-keto carbene species under study belong to a subclass of acyclic amino-aryl-carbenes (AAACs).
Jasper Adamson, Ryszard B. Nazarski, Jüri Jarvet, Tõnis Pehk, and Riina Aav
Wiley
AbstractUnprecedented scatter plots of calculated versus measured NMR 2,3JCH coupling constants in six densely oxygen functionalized epoxides are found with some B3LYP protocols, an effect attributed to stereoelectronic effects. Hence, 26 other exchange‐correlation density functionals (xc DFs) are benchmarked in this work. Very good results are achieved with mPW1PW91 and PBE0 in conjunction with the pcJ‐1 basis set (BS) of moderate size. A thorough statistical analysis of 53 relationships between the predicted and observed 2,3JCH datasets is presented. The effects of some xc DFs, including their x and c parts, and BSs on the calculation results are discussed, also in the context of DFT modeling of electron‐density distributions. Moreover, related 1JCH datasets predicted with 11 different DF methods are considered and compared with the experimental data. Finally, some proposals for further improvement of existing DFs based on the available nJCH (n=1–3) values are briefly outlined, in line with recent results on the DFT electron densities.
Ryszard B. Nazarski, Katarzyna Justyna, Stanisław Leśniak, and Anna Chrostowska
American Chemical Society (ACS)
Herein, an advantage of the use of IDSCRF- over UFF-radii-based solute cavities in GIAO/DFT calculations is presented for the 13C and especially 15N NMR chemical shifts made for several bicyclic aromatic nitrogen heterocycles in CDCl3 solution treated within the classical IEF-PCM solvation scheme. Successful application of the IDSCRF-radii in the non 1:1 joint multinuclear 1H/13C and particularly 1H/13C/15N correlations of the measured δH,C(,N) values to those obtained theoretically is also documented for a series of test systems (-268 ≤ δN ≤ -72 ppm). The experimentally yet unknown δN's were found in this way for the title compounds via a trinuclear eq 1 determined for an optimally chosen value of the multiplication factor of initial raw δH data (mH = 10). Such a simultaneous analysis of the δH,C(,N) data is proposed as a novel method to study the solution structure of the other similar conformationally homogeneous (bio)organic compounds. The issue of small spurious imaginary vibrational frequencies computed for a few molecular systems using the Gaussian 09 default UFF-radii is briefly considered as well.
Ryszard B. Nazarski, Piotr Wałejko, and Stanisław Witkowski
Royal Society of Chemistry (RSC)
Overall geometries of both glucosyl derivatives of PMC were found on the basis of their NMR spectra in CDCl3and relatedδH,C/nJHHIEF-PCM(UFF,CHCl3)/DFT calculational results.
Ryszard B. Nazarski and Włodzimierz Makulski
Royal Society of Chemistry (RSC)
The gas-phase 1J0,CHs in ‘isolated’ molecules of EMe4 were determined and discussed in terms of their geometric/electronic properties obtained from DFT calculations.
Ryszard B. Nazarski
Springer Science and Business Media LLC
Katarzyna Justyna, Stanisław Leśniak, Ryszard B. Nazarski, Michał Rachwalski, Thien Y. Vu, Thi Kieu Xuan Huynh, Saïd Khayar, Alain Dargelos, Anna Chrostowska, and Curt Wentrup
Wiley
AbstractPyrrolopyridines and naphthyridines are formed by flash vacuum thermolysis (FVT) of 3‐ and 4‐pyridylmethylidene‐tert‐butylimines 8 and 15. Elimination of a methyl radical generates resonance stablized 2‐azaallyl radicals a1 and b1. The formation of pyrrolopyridines 9, 16 and 17 is rationalized in terms of cyclization of 1‐aziridinyl radicals a2 and b2. Formation of naphthyridine 10 from imine 8, and of 11 and 18 from imine 15, are in accord with cyclization of 1‐azaallyl radicals a6 and b9. Formation of naphthyridine 11 from 8, and of 10 and 19 from 15, indicate the operation of the spiro‐cyclization pathways forming intermediates a9 and b14. Formation of the 1,8‐naphthyridine 20 (3 %) indicates a rearrangement through aziridine b22 and biradical b23. DFT calculations at the CAM‐B3LYP/6‐311G(d,p) level support the proposed reaction mechanisms.
Ewa A. Skorupska, Ryszard B. Nazarski, Magdalena Ciechańska, Andrzej Jóźwiak, and Arkadiusz Kłys
Elsevier BV
Justyna T. Polit and Ryszard B. Nazarski
Elsevier BV
Agata Szulawska‐Mroczek, Marta Szumilak, Malgorzata Szczesio, Andrzej Olczak, Ryszard B. Nazarski, Wieslawa Lewgowd, Malgorzata Czyz, and Andrzej Stanczak
Wiley
AbstractThe synthesis of new bischromone derivatives (4a–c and 5a–c) as potential anticancer drugs is described. The difference in the reactivity between 4‐oxo‐4H‐chromene‐3‐carboxylic acid 2 (or its methyl ester 3) and 4‐oxo‐4H‐chromene‐3‐carbonyl chloride 1 with three different polyamines: 3,3′‐diamino‐N‐methyldipropylamine (a), 1,4‐bis(3‐aminopropyl)piperazine (b), 4,9‐dioxa‐1,12‐dodecanediamine (c) resulted in the formation of two different groups of products, compounds 4a–c and 5a–c, designed in agreement with the bisintercalators' structural requirements. The transformation of 4‐oxo‐4H‐chromene‐3‐carboxylic acid into 2H‐chromene‐2,4(3H)‐diones (5) was confirmed by the NMR and XRD experiments. Compounds 4a and 5a were evaluated in vitro in the highly aggressive melanoma cell line A375. An enhanced induction of apoptosis and cell cycle arrest clearly revealed that compound 5a was more potent than 4a. Compound 5a was also more active in diminishing the adhesive potential of melanoma cells. Current studies support the notion that small changes in the three‐dimensional structure of molecules might have a substantial impact on their biological activity.
Ryszard B. Nazarski, Beata Pasternak, and Stanisław Leśniak
Elsevier BV
Stanisław Leśniak, Anna Chrostowska, Dawid Kuc, Małgorzata Maciejczyk, Saïd Khayar, Ryszard B. Nazarski, and Łukasz Urbaniak
Elsevier BV
Anna Chrostowska, Alain Dargelos, Alain Graciaa, Saïd Khayar, Stanisław Leśniak, Ryszard B. Nazarski, Thi Xuan Mai Nguyen, Małgorzata Maciejczyk, and Michał Rachwalski
Elsevier BV
Ryszard B. Nazarski
Wiley
AbstractThe most probable time‐averaged conformations of three polyammonium cations Hn2n+ (n = 3–5) formed from the macrocyclic pentamine ligand (2, scorpiand) [derivative of 1,4,8,11‐tetraazacyclotetradecane (cyclam)] were analyzed in order to elucidate an origin of ‘wrong‐way’ amine‐protonation shifts found in some 13C NMR pH‐profiles determined for the acidic H2O/D2O solution. These NMR trends were reproduced quite well in δCs computed for multicomponent shapes of related cations, which were in turn elucidated by the best fitting experimental data to those predicted by the gauge‐independent atomic orbital (GIAO) B3LYP/6‐31G* method, including the IEF‐PCM approach. A consistent DFT methodology of the treatment of such equilibrated cationic mixtures is proposed. Moreover, a few novel ONIOM2‐GIAO B3LYP/6‐31G*:STO‐3G type supermolecular calculations were performed for a simulated presence of bulk water molecules surrounding H525+. Copyright © 2009 John Wiley & Sons, Ltd.
Stanisław Leśniak, Ryszard B. Nazarski, and Beata Pasternak
Elsevier BV
Ryszard B. Nazarski
Informa UK Limited
The P(IV)↔H spin–spin transfer across the N─H· · · O−−P+ intramolecular H-bond previously observed NMR spectroscopically for Z stereoisomers of hydrazones of O,O′ -diisopropyl 1-oxoalkanephosphonates, 2h J PH = 2.95 ± 0.35 Hz, was rationalized using Fermi-contact (FC) contributions to such J PH couplings. Moreover, the FC terms were found to be dominant terms of these 2h J PH couplings. The applied FPT-DFT(B3LYP) FC calculational approach was successfully tested on J PH couplings in model phosphorus esters. As a result, linear relation J PH obsd (CDCl3) vs. J FC PH calcd was established for different long-range J PH couplings occurring via an oxygen atom of the phosphoryl group.
Ryszard B. Nazarski
Wiley
AbstractThe study of an isomeric A/B mixture of the title oxime 1, by photolytic or thermal E,Z‐isomerization and NMR measurement including 1H{1H}‐NOE difference spectra, led to assignment of the E configuration to its predominating form A. The 1H/13C data were interpreted in terms of steric overcrowding of both forms, especially of the thermolabile photoproduct B. Four classical (empirical) NMR methods of elucidating the oxime geometry were critically tested on these results. Unexpected vapor‐phase photoconversion A→B in the window glass‐filtered solar UV and spectroscopic findings on their protonated states were discussed, as well. The kinetically controlled formation of the N‐protonated species (Z)‐5+ was proved experimentally. In addition, some 1H NMR assignments reported for structurally similar systems were rationalized (3 and 4) or revised (1 and 7–9) with the GIAO‐DFT(B3LYP) and/or GIAO‐HF calculational results. Copyright © 2007 John Wiley & Sons, Ltd.
Wojciech J. Kinart, Ryszard B. Nazarski, Cezary M. Kinart, Quang T. Thuong, and Rafał Oszczęda
Informa UK Limited
Abstract The 3β‐acetoxy‐6β‐(3,5‐dioxo‐4‐phenyl‐[1,2,4]triazolidin‐1‐yl)cholest‐4‐ene structure has been assigned to a single product of the reaction of cholesteryl acetate with 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione in Et2O solution, mediated by LiClO4.