Accuracy of determination of self-diffusion coefficients in studies of porphyrin-based complexes by 2D DOSY

© ISUCT Publishing. Influence of chemical exchange processes on the accuracy of determination of self-diffusion complexes of porphyrinnickel complexes was shown. A method of estimating the inaccuracy of the self-diffusion coefficients for an inverted porphyrin complex was proposed. The values obtained using two different approaches to recording DOSY spectra, STE and CPMG, were compared. Allowing for exchange was shown to be important for accurate diffusion measurements and correct interpretation of results obtained in studied of molecular-level processes

Hybrid multi-porphyrin supramolecular assemblies: Synthesis and structure elucidation by 2D DOSY NMR studies

© 2015 Elsevier B.V. All rights reserved. Design and synthesis of hybrid multi-metalloporphyrin assembles have been performed. The chemical structure of the synthesized complexes and their stability in solution were confirmed by the methods of 2D DOSY NMR spectroscopy, which have been specially adapted for these supramolecular architectures in solutions

N-Confused porphyrins: Complexation and¹H NMR studies

© 2017 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique. The complexation of 2-aza-21-carba-tetraphenylporphyrin and 2-aza-2-methyl-5,10,15,20-tetraphenyl-21-carbaporphyrin with nickel and zinc acetates in organic solvents has been investigated by UV-Vis spectroscopy and 1 H NMR. It has been shown that the enhanced reactivity of these tetrapyrrolic macrocycles is mainly determined by their ability to exist in different tautomeric forms

Zinc(II) bis(dipyrromethenate)s crystal solvates with dimethyl sulfoxide Composition, stability and spectral-luminescent properties

© 2017 Elsevier B.V.It was found that 3,3′-, 2,3′ and 2,2′-zinc(II) bis(dipyrromethenate)s ([Zn2L2]) form stable supramolecular complexes of the composition [Zn2L2(DMSO)n] (n = 1 or 2) with dimethyl sulfoxide (DMSO). The [Zn2L2(DMSO)n] are stable in the solid phase and solutions. Composition, stability, and spectral-luminescent properties of the [Zn2L2(DMSO)n] crystal solvates were studied by means of FTIR, PXRD, 1H NMR, DOSY, absorption and fluorescence analyses. Spectroscopic studies showed that the quantum yields (φ) of [Zn2L2(DMSO)n] are lower (to ∼1.6–3.6 times) than quantum yields (φо) of [Zn2L2] in cyclohexane. Quantum-chemical study allowed to suggest the most likely mechanism of the DMSO molecules coordination on the coordinating centers of [Zn2L2]. It is demonstrated, that the high-energy coordination interactions (Zn − O) in [Zn2L2(DMSO)n] are the main cause of the fluorescence quenching of [Zn2L2] in the presence of DMSO. Fluorescence quenching of [Zn2L2] in the DMSO presence is based on the photoinduced electron transfer (PeT) mechanism. The obtained results are interesting for the development of new [Zn2L2] fluorescent sensors of the DMSO molecules

Inversion of population distribution of felodipine conformations at increased concentration in dimethyl sulfoxide is a prerequisite to crystal nucleation

Knowledge of the preferred conformations of biologically active compounds is of the utmost importance for a better understanding of the structure-activity relationships underlying their biological activity, as well as their mechanism of action. Moreover, investigating the mechanism of nucleation from a saturated solution can facilitate the discovery and preparation of new polymorphic forms. To search regularities in the crystal nucleation of biologically active compounds (drugs) from a saturated solution, we studied the conformational preference of felodipine in dilute and saturated solution in dimethyl sulfoxide. The inversion of conformation distribution at increased concentration occurs: conformers that dominate in a dilute solution become the least abundant in the saturated one. Conformers that dominate in the saturated solution are of the same type as revealed in crystalline state by X-ray. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:392-394, 2014

Synthesis and spectroscopic characterization of Ru(II) and Sn(IV)-porphyrins supramolecular complexes

Copyright © 2014 Published by Elsevier B.V. All rights reserved. Synthesis and NMR studies of Ru(II) and Sn(IV) tetraphenylporphyrins supramolecular complexes were carried out. The diffusion coefficients of the complexes, porphyrinates, and solvents were determined by DOSY NMR spectroscopy. By the method of spectrophotometric titration a binding ability of Ru(II) tetraphenylporphyrin towards 4-(imidazol-1-yl)-phenol was investigated, stability constant of resulting complexes and concentration intervals of their existence were defined. Crow

Determination of preferred conformations of ibuprofen in chloroform by 2D NOE spectroscopy

© 2014 Elsevier B.V. All rights reserved. Solution of an anti-inflammatory drug ibuprofen ((RS)-2-(4-isobutylphenyl) propionic acid) in chloroform was studied by nuclear magnetic resonance spectroscopy. A set of 2D NOESY spectra was analyzed in order to obtain atom-atom distances. Since ibuprofen is known to exist as an ensemble of different conformations, these distances are averaged over the ensemble. To compare experimental and calculated distances, three models of averaging were concerned. Our data allowed to determine the dominant conformers of ibuprofen dissolved in chloroform. The population of conformers in the saturated solution leads to a certain crystal morphology formed within the nucleation process. Observed and calculated 13C chemical shifts (at the DFT/B3LYP/6-311+G(2d,p) level) were in good agreement

Detailed NOESY/T-ROESY analysis as an effective method for eliminating spin diffusion from 2D NOE spectra of small flexible molecules

© 2015 Elsevier B.V. An intriguing property of the multistep magnetization transfer, so-called spin diffusion, is that it can affect the results of NMR-based analysis of conformer distribution of small molecules in solution. Therefore, the contribution of spin diffusion should be subtracted in order to obtain accurate data on molecular conformations and their distributions. Several methods have been developed for this purpose, but many of them have a lack of versatility. These methods were critically analysed, and two approaches to eliminate spin diffusion were tested during the study of felodipine as the drug molecule of small size. QUIET-NOESY was found to be a powerful technique to solve this problem. The second method, combined analysis of two sets of spectra, NOESY and T-ROESY, was tested and proved to be the most correct way of obtaining exact internuclear distances in a flexible molecule in solution

Memory of myself and memory on myself. An attempt to make autobiographical memory tests.

This research reviewed several methods of various autobiographical memory tests, examining if a method is adequate and easy to carry out among many people, if it allows people to recall easily their memories of various times in life, and allows us to research the retention interval of autobiographical memory, and also if it allows us to compare the autobiographical memory of normal healthy people to that of amnesic patients. Of those methods, Croviz\u27s technique and autobiographical fluency test were borrowed, and two experiments were conducted. In Experiment 1, episodes elicited by 3 kind of words(affect words,object words, activity words) were compared,regarding their richness of description and the time when those episodes actually occurred. The results showed that female subjects recalled more in detail than male subjects did, and that the episodes elicited by affect words were less episodic in description and had occurred more recently than those elicited by the other 2 kind of words. In Experiment 2, by means of simplified autobiographical fluency task, middle aged people(50\u27s) and young people(20\u27s) were compared with regard to their autobiographical memory and autobiographical facts. The results showed that middle aged people recalled fewer proper nouns(names of people and names of places) than young people did from childhood up until one yea ago, and that middle aged people recalled more episodes than young people did in proportion to the total number of elicited episodes as for the time of adolescence and for the recent 1 year.本研究では、様々な自伝的記憶検査方法のうち、第1に、多くの人に簡単に施行できる検査方法であること、第2に、人生の様々な時期の自伝的記憶を再生させ、自伝的記憶が時間的にどのくらい保持されているかを知ることができる方法であること、第3に、年齢間の比較や健常者と健忘症の患者の比較が容易な方法であることを選択基準として、いくつかの方法を紹介した。また、これらの方法のうちCrovitz法を用いて、大学生の自伝的記憶のエピソード性の評価と再生時期の分析を行う実験を行った。その結果、女性の方が男性よりエピソード性が高く、また男女とも、情動を表す単語により喚起される自伝的記憶は、活動を表す単語や物を表す単語とは異なり、内容は詳細だが「いつ」、「どこで」などのエピソード性が低く、再生時期も他の単語に比べて最近（高校時代）であることが示された。また、自伝的流暢性課題を簡易化した方法を用いて、20代と50代の年齢間の比較を行う実験を行った。この結果、固有名詞（人の名前や場所の名前）は20代に比べて50代の人では子供時代から最近に至るまで再生が悪いこと、全体的に対するエピソードの比率は、青年期（中学卒業後5年）と最近において50代の人は20代の人より多いことが示された