A Double Isotopic Labelling Study of the Infrared Spectra of the Linkage Isomers [Pd(bipy)(SCN)2], [Pd(bipy)(NCS)2] and Related Complexes

Abstract

The IR spectra of the linkage isomers [Pd(bipy)(SCN)₂] and [Pd(bipy)(NCS)₂] have been determined in the C≡N stretching region (2200–2000 cm^?1) and below 500 cm^?1. The band shifts resulting from deuteration of the 2,2′-bipyridine (bipy) ring and ¹⁵NCS-labelling are shown to provide a ready means for distinguishing between the internal ligand modes, the μPd-N(bipy) and μPd-SCN/μPd-NCS vibrations. The assignment technique has been further extended to the complexes [Pt(bipy)(SCN)₂] and [Pd(phen)(SCN)₂] (phen = 1,10-phenanthroline). Finally, a comparison between the IR spectra of [Pd(bipy)(NCO)₂], [Pd(bipy)(NCS)₂] and [Pd(bipy)(SCN)₂] reveals that the frequencies μM-NCO, μM-NCS and μM-SCN decrease in the sequence NCO > NCS > SCN.     

NMR Studies of Drugs. Applications of Achiral and Chiral Lanthanide Shift Reagents to the Analgesic,Famprofazone: “Anomalous Shifts”

The 200 MHz ¹H NMR spectra of the analgesic, famprofazone, 1, have been studied in CDCl₃ solution at ambient temperatures with the achiral lanthanide shift reagent (LSR) tris (6, 6, 7, 7, 8, 8, 8-heptaf luoro-2, 2-dimethyl-3, 5-octanedionato) europium (III), Eu(FOD)₃, 2, for spectral simplification, and with the chiral LSR, tris [3-(heptafluoropropylhydroxymethylene) - (+) camphorato] europium (III), Eu (HFC)₃, 3. Lanthanide induced shift (LIS) magnitudes suggested predominant LSR binding at the carbonyl oxygen. Substantial enantiomeric shift differences were observed for several nuclei of 1 with added 3 which could permit direct determinations of enantiomeric excess.     

NMR Studies of Drugs. Applications of Achiral and Chiral Lanthanide Shift Reagents to a 5-Substituted-4-thiazolidinone

The 60 MHz ¹H NMR spectra of racemic 5-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-4-thiazolidinone, 1, have been studied in CDCl₃ solution at 28° with the achiral lanthanide shift reagent (LSR), tris (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium (III), 2, and the chiral LSRs, tris[3-(heptafluoropropylhydroxymethylene)- (+)-camphoratojeuropium(III), 3, and tris[3-(trifluoromethylhydroxymethylene-(+) -camphorato]europium (III), 4, Significant enantiomeric shift differences were observed in the presence of added 3, for the aryl protons of 1 that should permit direct determination of enantiomeric excess. Relative magnitudes of lanthanide-induced shift for the different nuclei of 1 with the three LSRs are compared and discussed in terms of preferred LSR binding sites. A favored conformation of 1 with respect to rotation about the C(5)-CH₂ bond is suggested.     

NMR Studies of Agricultural Products. Applications of Achiral and Chiral Lanthanide Shift Reagents to the Fungicide,Triadimefon.

Abstract

The 60 MHz ¹H NMR spectra of the systemic agricultural fungicide, triadimefon, 1, have been studied in CDCl₃ at 28±1° (as the racemic free base) with the added achiral lanthanide shift reagent (LSR), tris(6, 6, 7, 7, 8, 8, 8-heptafluoro-2, 2-dimethyl-3, 5-octanedionato) europium(III), Eu(FOD)₃, 2, for spectral simplification, and with the chiral LSR, tris [3-(heptafluoropropylhydroxymethylene)-(+) -camphorato)europium(III), Eu(HFC)₃, 3, to induce enantiomeric shift differences (ΔΔδ) for several nuclei. Significant ΔΔδ values were seen for the two protons of the heterocyclic ring, the OCH methine, and aryl H-2′, 6′ of the chlorophenoxy ring. For each of these nuclei exhibiting ΔΔδ with added 3, the ΔΔδ magnitudes reached maximum values with 3: 1 molar ratios ca. 0. 18–0. 29, and decreased with higher levels of 3. To confirm analytical utility of 3 for % e. e. determinations of 1, a nonracemic (“spiked”) sample of racemic 1, with added R-(?) triadimefon, was examined with 3. At low 3: 1 ratios, both triazole H-3 and H-5, as well as the OCH and aryl H-2′, 6′ protons of (?)-1 showed a downfield sense of magnetic nonequivalence with (+) -3. With 3: 1 ratios ca. 0. 8, triazole proton H-3 reversed its sense of magnetic noneguivalence. The H-3 and H-5 signals were useful for % e. e determinations at this higher 3: 1 ratio.     

NMR Studies of Drugs. Sulindac Methyl Ester. Applications of Achiral and Chiral Lanthanide Shift Reagents

The potent nonsteroidal anti-inflammatory agent, sulindac, (Z) -5-fluoro-2-methyl-1-{[4-(methylsulfinyl) - phenyl]methylene} -1H-indene-3-acetic acid, has been examined by ¹H NMR as its methyl ester in CDCl₃ solution with the added achiral lanthanide shift reagent (LSR) tris (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium (III), Eu (FOD)₃, 2, for spectral simplification, and with the chiral LSRs, tris[3-(heptafluoropropylhydroxymethylene) - (+) - camphorato] europium (III), 3, and tris[3-(trifluoromethyl-hydroxymethylene) - (+) -camphorato] europium (III), 4, to induce enantiomeric shift differences (ΔΔδ) for several nuclei. Studies employed 60 and 300 MHz spectrometers. At the higher frequency, analytically useful ΔΔδ values were observed with added 3 for the aryl protons ortho to the methylsulfinyl group that should permit direct determinations of enantiomeric excess (% ee). By conversion of sulindac samples to the methyl ester, use of 3 would then formally constitute an ee determination of sulindac.     

NMR Studies of Drugs: Antipyrine and Analogs. I. Use of Achiral and Chiral Lanthanide Shift Reagents to Examine Hindered Rotation.

The 200 MHz ¹H NMR spectra of the analgesic, antipyrine, 1, have been studied in CDC1₃ solution at ambient temperatures with the achiral lanthanide shift reagent (LSR) tris (6, 6, 7, 7, 8, 8, 8-heptafluoro-2, 2-dimethyl-3, 5-octanedionato) europium (III), Eu(FOD)₃, 2, and with the chiral LSR, tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorato]europium(III), Eu(HFC)₃, 3., Lanthanide-induced shift (LIS) magnitudes and broadening of selected signals are consistent with predominant LSR binding at the carbonyl oxygen with either 2 or 3. Of the different possible conformational regimes for the N-phenyl group of 1, our results appear to rule out a slow exchange limit (SEL) system with the N-phenyl coplanar with the heterocyclic ring. Perpendicular rings in an SEL regime can not be ruled out. A rapidly-rotating N-phenyl (fast exchange limit, FEL system) would also be consistent with observed results. Accurate chemical shifts for the aryl protons (overlapped in the 200 MHz spectrum of unshifted 1) are determined from spectra with added LSR by extrapolation to zero molar ratios of [LSR]:[1]. Relative slopes in the plots of chemical shift versus [LSR]:[1] molar ratios are calculated for each proton signal of 1.     

Design and verification of LSR module in laser display

The LSR module of optical engine in laser display has been designed and discussed in this paper. It has also been tested and verified with the scattering sheet of 5°, 10° and 20°. The experiment demonstrates that the method of rotating the scattering sheet with 10° can effectively suppress laser speckle in our system. It can make the speckle contrast of large power projection system drop to 4.2% < 5%, which reaches the acceptable range of the human eyes.     

Use of a Lanthanide Shift Reagent for Simplified NMR Analysis of Borneol—Isoborneol Mixtures. Apparent Catalysis of OH Proton Exchange by LSR

The use of ¹H NMR at low field (60 MHz spectrometer frequency) for direct analysis of mixtures of borneol, 1, and isoborneol, 2, is considerably simplified by addition of the lanthanide shift reagent (LSR), tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III), 3. The effect of added 3 is twofold. Firstly, the analytical marker signals of the methine proton CHOH in 1 and 2, which are partly overlapped at 60 MHz in CDCl₃ (28°), are separated and rendered baseline-resolved due to preferential LSR binding to the less hindered endo OH of 1. Secondly, the absorption signals of the CHOH methines actually sharpen in the presence of 3, and display clearly defined multiplet structure, attributed to full exchange decoupling of the vicinal OH as a result of enhanced OH exchange rates when LSR is present.     

拟除虫菊酯类农药的NMR研究Ⅰ.α-对取代苯基异戊酸及其类似化合物的手性和前手性NMR研究

α-对取代苯基异戊酸是合成拟除虫菊酯的重要中间化合物,其结构中有手性和前手性两个甲基。为了解构效与活性的关系,本文对其结构特点进行了仔细的考察。用手性位移试剂Eu(hfbc)₃和位移试剂Eu(fod)₃^-分离了对映体的¹H和¹³C的信号,并作出了一定的解释,为鉴定化合物的光学纯度找出了一种简便的方法。对异丙基上的两个非对映异位甲基作了详细的观察,确定了优势构象,并对其作了标识,实验与由简单模型的计算结果一致。本文认为在对这两个非对映异位甲基信号位移差别大小的影响中,取代基的体积效应起了相当重要的作用。     

NMR Studies of Agricultural Compounds. Applications of Achiral and Chiral Lanthanide Shift Reagents to the Herbicide,Diclofop Methyl

The 60 MHz H NMR spectra for the herbicide, diclofop methyl, 1, have been studied in CDCl₃ solution at 28±1° with the added achiral lanthanide shift reagent (LSR) tris (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato) europium(III), Eu (FOD)₃, 2, and with the chiral LSRs, tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorato]europium(III)₃, Eu(HFC)₃, 3, and tris[3-(trifluoromethylhydroxymethylene)-(+)-camphorato]europium(III), Eu(FACAM)₃, 4. Both 2 and 3 produced substantial lanthanide-induced shifts (LIS) consistent with predominant LSR binding at the ester carbonyl. Much smaller LIS magnitudes were observed with 4. Modest enantiomeric shift differences (ΔΔδ) were elicited with 3 for the OCH₃ and the CCH₃ resonances of 1. The former signal appears to offer greatest potential for the direct determination of enantiomeric excess of samples of 1, with 3:1 molar ratios ca. 0.3–0.4 resulting in valley heights as low as 33% of the average peak heights of the OCH₃ signals of the two enantiomers.