Carbon-13 NMR Spectroscopy of the Antileukemic Drug MGBG and Related Bis(Amidinohydrazones) [‘Bis(Guanylhydrazones)’]

The first survey of the carbon-13 NMR spectroscopy of the bis(amidinohydrazones) [‘bis(guanylhydrazones)’] of various glyoxals is reported. The compounds studied included the free base and the dihydrochloride of the investigational antileukemic drug methylglyoxal bis(amidinohydrazone) (MGBG) and the dihydrochloride of the parent compound glyoxal bis(amidinohydrazone), as well as the free bases of seven alkyl- and dialkylglyoxal analogs of these compounds. Spectra were assigned with the aid of off-resonance proton noise decoupled carbon-13 measurements. The results obtained strongly suggest that each of the compounds studied consisted of one of the three or four possible geometrical isomers only, or that (less probably) the isomerization of the compounds is rapid on the NMR time scale. Thus, the results are in line with previous proton NMR and X-ray crystallographic observations, and support the theory that the classical syntheses of the compounds tend to yield     

Mass Spectroscopy of the Antileukemic Drug MGBG and Related Bis(Amidinohydrazones) [‘Bis(Guanylhydrazones)’]

The first study on the mass spectroscopy of various bis(amidinohydrazones) is reported. The compounds studied included the investigational antileukemic drugs methylglyoxal bis(amidino-hydrazone) [‘methylglyoxal bis(guanylhydrazone)’, MGBG] and glyoxal bis(amidinohydrazone), as well as seven mono- and dialkylglyoxal analogs thereof. The results indicate that the free bases of these high-melting compounds are volatilized well enough to allow a facile detection of the molecular ions and to make mass spectroscopy of the underivatized compounds a suitable method for the verification of the identity of the substances. This result is of importance considering the development of novel analogs and derivatives. A compilation of electron-impact mass spectra is reported and possible fragmentation routes are outlined. The fragmentation of the various congeners appears to occur essentially similarly, the main paths involving breakage of the carbon-carbon single bond in the glyoxal moiety or breakage of either one of the nitrogen-nitrogen single bonds.     

2D-NMR Studies on Bis(Amidinohydrazones). I. A Proton-Carbon Heteronuclear Shift Correlation Study on the Enzyme Inhibitors Methylpropylglyoxal Bis(Amidinohydrazone) and Butylmethylglyoxal Bis(Amidinohydrazone)

The first 2D-NMR study on bis(amidinohydrazones) [‘(guanylhydrazones)’] is reported. Heteronuclear shift correlation (HETCOR) experiments were performed on the enzyme inhibitors methylpropylglyoxal bis(amidinohydrazone) (MPGBG) and butylmethylglyoxal bis(amidinohydrazone) (BMGBG). The results obtained made possible the unambiguous assignment of the previously unassigned resonances of the side-chain carbon atoms of MPGBG. The results indicate that the chemical shifts of the protons of the propyl side chain of MPGBG are positively correlated to the ¹³C chemical shifts of the corresponding carbon atoms. The chemical shifts of the carbon atoms of the propyl side chain decrease as a function of the position of the atom in the side chain, the terminal methyl group having the lowest shift value. These results are in full agreement with previous results on the analogous compound dipropylglyoxal bis(amidinohydra- zone), whose side-chain carbon resonances were assigned using totally different techniques. In the case of BMGBG, however, HETCOR contour plots clearly indicate that there is no correlation between the chemical shifts of the protons of the butyl side chain and the 13C chemical shifts of the corresponding carbons. Because the 200 MHz proton spectrum of BMGBG is not fist-order, only the 1 3 resonance～ of the methyl substituent and the resonances of carbons 1 and 4 (but not those of carbons 2 and 3) of the butyl side chain could be assigned on the basis of the HETCOR study. Yet, the results gave a rough estimate of the previously unknown chemical shifts of the protons bound to butyl carbon atoms 2 and 3.     

Unambiguous Assignment of the 13C NMR Resonances of the Side-Chain Carbon Atoms of Dipropylglyoxal Bis(Amidinohydrazone) by DEPT and Selective Heteronuclear Proton Decoupling Techniques

The previously unassigned carbon-13 NMR resonances of the side-chain carbon atoms of the enzyme inhibitor dipropylglyoxal bis(amidinohydrazone) (DPGBG) have been unambiguously assigned with the aid of DEPT measurements and experiments involving the selective decoupling of the protons of one of the methylene groups. The chemical shifts of the side-chain carbon atoms of DPGBG decrease in a nearly linear fashion as a function of the position of the atom in the side chain, the terminal methyl groups having the lowest shift value. The carbon-13 shifts are positively correlated with the chemical shifts of the corresponding hydrogen atoms.     

Substituent Effects in the Carbon NMR of Aliphatic bis(Amidinohydrazones) ['Bis(Guanylhydrazones)']. Construction of a set of Quantitative Empirical Rules. Unambiguous Assignment of Several Previously Unassigned Carbon Resonances

The effects of substituents on the ¹³C chemical shifts of the various carbons of aliphatic 1,2-bis(amidinohydrazones) have been systematically studied using previously published experimental data as the basis. Mathematical formulae have been constructed that describe the effects of various structural features of the molecules on the chemical shifts of the carbons and that also make possible an accurate prediction of the spectra of compounds belonging to this class. It is also shown that the effects of side chains on the chemical shifts of the two carbons of the glyoxal moiety are strictly additive. A mathematical model has been constructed that makes possible a very accurate prediction of the chemical shift of each one of the glyoxal carbons of symmetrical as well as unsymmetrical bis(amidinohydrazones). In the case of ethylmethylglyoxal bis(amidinohydrazone) free base dissolved in dimethyl sulfoxide, the theory predicts that the glyoxal carbons resonate at 157.45 ppm (the one connected to the ethyl group) and 151.21 ppm, while the experimental values are 157.30 and 151.29 ppm. This has, for the first time, made possible the unambiguous individual assignment of the resonances of the glyoxal carbons of unsymmetrical dialkylglyoxal bis(amidinohydrazones). The results also indicate that in all such compounds so far studied, that one of the glyoxal carbons that bears the longer alkyl side chain resonates more downfield than does the other one. This result is in total agreement with conclusions derived from relaxation time measurements.     

UV/VIS Spectrophotometric Studies on the Antileukemic Agent Glyoxal bis(Amidinohydrazone) [‘Glyoxal bis(Guanylhydrazone)’]

Glyoxal bis(amidinohydrazone) (GBG) and several analogs thereof are compounds of considerable pharmacological interest, and a variety of HPLC and MECC methods have been developed for their analysis. In these methods, detection is invariably based on the strong UV absorption of the compound. Yet, almost nothing has been known of their UV and VIS spectral properties. In the present paper the UV and VIS Spectroscopy of GBG has been studied in several solvent systems (water, 0. 03 M aqueous sodium acetate buffer, 0. 1 inM aqueous NaOH and dimethylsulfoxide). In the case of solutions in bare water, the shape of the UV spectrum depends drastically on concentration, probably because of changes in the species distribution of GBG as a function of concentration. The spectrum comprises one maximum at ca. 200 nm, and between ca. 250 nin and 400 nm an absorption region with distinctly higher absorbance. In the case of aqueous sodium acetate as well as NaOH solutions, one strong maximum can be detected (at ca. 285–288 nm and 332–337 nm, respectively). In both cases, the maximum occurs at constant wavelength, being independent of concentration. In dimethylsulfoxide, the spectrum of GBG contains an absorption band at distinctly higher wavelengths (λ_max 354 nm) than in any one of the aqueous solvents studied, indicating that solvent effects are considerable in the UV spectrum of GBG. In no case, distinct absorption could be detected at wavelengths higher than 400 nm. The results indicate that if aqueous media are used as elements in HPLC analyses of bis(amidinohydrazones) or as solvents in direct UV analysis, they must be buffered.     

He(I) photoelectron spectra of bis(β-diketonate)nickel(II) complexes and their mono- and di-thio analogues

The vapor-phase He(I) photoelectron spectra of a series of bis(β-diketonate) nickel(II) complexes and some mono- and di-thio analogues are reported. The spectra are discussed in terms of the metal-ligand bonding present, and the effect on this bond of replacing oxygen donor atoms by sulphur donor atoms.     

Studies on the Spin-Lattice Relaxation Times of the Carbons of the Investigational Antileukemic Drug and Enzyme Inhibitor Methylglyoxal Bis(Amidino-Hydrazone) ['Methylglyoxal BIS(Guanylhydrazone)'] and Its Dialkylglyoxal Analogs

The first study on the ¹³C relaxation times of bis(amidinohydrazones) is reported. The spin-lattice relaxation times (T₁) of the carbons of the free bases of methylglyoxal bis(amidinohydrazone) (MGBG) and of four dialkylglyoxal analogs thereof were determined with the aid of the inversion recovery method and using dimethyl sulfoxide as the solvent. In the series of compounds studied, one of the side chains was always a methyl group, while the other one was altered (hydrogen, methyl, ethyl, propyl, butyl). Remarkable differences were found to exist between the T₁ values of the various carbons within each molecule. The T₁ values were in the range 1.5 - 2 s for methyl carbons, 0.16 - 1.9 s for carbons of longer alkyl groups, 4.3 - 7.0 s for unprotonated carbons of the glyoxal moiety, 0.57 s for the protonated glyoxal carbon of MGBG, and 2.6 - 3.1 s for guanidino carbons. The bulk of the differences are explainable by assuming that the major relaxation mechanism for the protonated carbons is dipolar relaxation. In alkyl side chains, the T₁ values increased in a very regular fashion down the chain. This effect made possible the assignment of two previously unassigned carbon resonances of the butyl group of BMGBG. T₁ studies thus offer a facile and reliable method for the assignment of side-chain carbon resonances of bis(amidinohydrazones). Further, T₁ measurements were found to offer a very good method for the individual assignment of the glyoxal carbons of unsymmetrical congeners, whose assignment has so far constituted a problem. The method, based on the finding that the one of the carbons bonded to the shorter alkyl chain has a longer relaxation time than does the other one, made possible the unambiguous assignment of several previously unassigned carbon resonances. The results obtained also offer a reliable method for unambiguously distinguishing between the resonances of glyoxal carbons and guanidino carbons that have been difficult to distinguish from each other because the separation of their chemical shifts is often extremely small. Correlations observed between T₁ values and the degree of alkyl substitution in the molecule are discussed, as are also possible relaxation mechanisms. Somewhat unexpectedly, the results obtained suggest that dipolar relaxation through the hydrogens of neighboring carbon atoms may to a significant extent contribute to the relaxation of some unprotonated carbons in bis(amidinohydrazones).     

Structure and optical properties of lead iodide based two-dimensional perovskite compounds containing fluorophenethylamines

Phenethylammonium-based perovskites, which can be regarded as a semiconductor/insulator multiple quantum well consisting of lead halide semiconductor layers sandwiched between phenethylammonium insulator layers were prepared. To investigate the effects of the electronic state and the orientation of organic insulator layers on the optical properties of layered perovskites, fluorine substituted analogues were also prepared. The structure and optical properties were investigated by the XRD, UV–Vis absorption, and fluorescence measurements. The exciton absorption peak was shifted by the substitution of fluorine atoms in organic ammonium compounds. It became clear that the optical properties of two-dimensional perovskite compounds were controlled by the substitution of fluorine atoms.     

Cu(Ⅱ)及Zn(Ⅱ)与直链醚席夫碱配合物的合成与表征

合成了两种直链醚席夫碱双水杨醛缩二甘醇二胺(SALDA)和双水杨醛缩四甘醇二胺(SALTTA)及其新配合物[Zn(SALDA)](NO₃)₂·4H₂O和[Cu₃(SALTTA)(NO₃)₄](NO₃)₂·3H₂O.并以IR谱、UV谱,特别是¹H和¹³C NMR谱等方法进行了表征,并详细地讨论了合成方法,IR谱表明SALTTA中醚氧并未全部配位.     

C-13 NMR Spectra of N-Aminopyridinium Perchlorates

C-13 NMR spectra of fifteen N-aminopyridinium perchlorates show the effect of amination of the ring nitrogen atom to be similar to that observed in the pyridine N-oxide spectra, particularly for the 2(6) and 3(5) positions. Benzene and pyridine increments predict well the carbon chemical shifts for the title compounds unless both positions 2 and 6 are occupied. The chemical shifts of some carbon atoms in the compounds studied are linearly dependent on those in the respective benzene derivatives as well as on the Hammett σ constants.     

Synthesis of novel fluorinated bis(biphenyl)diacetylene derivatives as highly birefringent nematic liquid crystalline materials

Three novel fluorinated bis(biphenyl)diacetylene (1,4-bis(biphenyl-4-yl)buta-1,3-diyne) derivatives, with alkoxy tails at the terminal positions, were prepared for use as high-birefringent nematic materials. To lower the thermal transition temperatures and determine the origin of the nematic phase of these compounds, fluorine atoms were introduced at lateral positions. Thermal transition temperatures and mesomorphic properties were investigated by differential scanning calorimetry and polarized optical microscopy. In addition, birefringence was measured using a microscopic method based on the interference method. Both the nematogenic properties and optical performances depended not only on the number of fluorine substituents, but also on the position of the substituents. The compound having the highest fluorine content exhibited the lowest birefringence, and the compound bearing fluorine atoms only on the inner benzene rings of the biphenyl cores exhibited an enantiotropic nematic phase with a maximum birefringence value of 0.48 at 550 nm and 140 °C.     

IR- and UV-Spectral Study on the Mechanism of 2-Aminopyridine Complexation with Palladium (II)

Abstract

The IR-spectra of Pd (II) complexes with 2-aminopyridine, obtained both in sulphuric acid and alkaline solution are studied in the region 1700- 1400 cm^?1. The structural conclusions are based on comparison with the IR- and UV-spectra of the free ligand and aminopyridinium sulphate, as well as of trans-dichloro-di-2-aminopyridine-palladium and deuterated at the amino group analogues of the investigated compounds.     

Molecular Spectral Analysis and Ab Initio Calculations of bis(3-aminopyridinium) Tetrachlorocuprate (II), 3-Ammoniumpyridinium Tetrachlorocuprate (II), and bis(3-aminopyridinium) Hexachlorodicuprate (II)

The aromatic character, distortion, and stabilization as a result of single and double protonation of 3-aminopyridine like three different complex salts were studied by infrared-, ultraviolet spectral analysis, proton nuclear magnetic resonance, and quantum chemical ab initio calculations. Linear-dichroic infrared spectroscopy was applied for identification of the infrared bands. The correlation structure-spectroscopic properties of the model systems are determined: bis(3-aminopyridinium) tetrachlorocuprate (II) salt, where the ring nitrogen atom participates in protonation; 3-ammoniumpyridinium tetrachlorocuprate (II) salt, where both nitrogen atoms are protonated; and a complex with copper (II) bis(3-aminopyridinium) hexachlorodicuprate (II), where the metal ion is coordinated through amino group.     

苯并咪唑取代胺及其配合物光谱分析

本文阐述了用原子吸收光谱测定三（2－苯并咪唑亚甲基）胺和二（2－苯并咪唑亚甲基）胺与Cu2 的配合物中心原子,并对上述配体及配合物用紫外光谱法和红外光谱法进行了研究,从而解释了配合物分子结构。     

Photoemission study of Gd metal overlayers on a GaAs(110) surface

We have studied the chemical reactions of Gd metal on an in situ cleaved GaAs(110) surface by photoemission spectroscopy of Ga 3d and As 3d core-levels as well as the Gd 4f level on- and off-resonance valence band using synchrotron radiation. We find that the Fermi-level pinning is completed before 0.13 ML coverage, and the deposited Gd atoms start to react with the GaAs substrate at a very low coverage (critical coverage < 0.067 ML). As more Gd atoms are deposited, they form stable compounds with As atoms which are then trapped in the relatively narrow interfacial layer of thickness less than about 3.3 ML, while Ga atoms diffuse out towards the surface and eventually become metallic. The thickness of the GdGa intermixed layers is estimated to be about 6.7 ML, which is somewhat greater than that for a interface.     

Density functional simulations of Sb-rich GeSbTe phase change alloys

We generated models of the amorphous phase of Sb-rich GeSbTe phase change alloys by quenching from the melt within density functional molecular dynamics. We considered the two compositions Ge(1)Sb(1)Te(1) and Ge(2)Sb(4)Te(5). Comparison with previous results on the most studied Ge(2)Sb(2)Te(5) allowed us to draw some conclusions on the dependence of the structural properties of the amorphous phase on the alloy composition. Vibrational and electronic properties were also scrutinized. Phonons at high frequencies above 200?cm(-1) are localized in tetrahedra around Ge atoms in Sb-rich compounds as well as in Ge(2)Sb(2)Te(5). All compounds are semiconducting in the amorphous phase, with a band gap in the range 0.7-1.0?eV.     

FT-Raman拉曼光谱在金属有机化合物表征中的应用

金属有机化学是化学研究中近半世纪来十分活跃和迅猛发展的领域，它作为新型有机合成试剂，均相催化剂和发展新材料在实际应用中已广为采纳。振动光谱是表征金属配合物和金属有机化合物的重要手段，已有不少好的总结文章［１］和专著［２］。回顾前人的工作，较多的利用红...     

Defects in semiconductors—results from Mössbauer spectroscopy

Progress in the development of Mössbauer techniques with ion-implanted, radioactive precursors to a Mössbauer isotope is discussed. Results obtained for elemental group IV semiconductors and their alloys as well as for III–V and II–VI compound semiconductors are presented. Emphasis is put on Mössbauer emission spectroscopy with radioactive probe atoms where the recoil energy in the nuclear decay is sufficient to expel the daughter atoms from a (substitutional) lattice site. The interactions of such (interstitial) atoms have been studied for ¹¹⁹Sb →¹¹⁹Sn in III–V compounds and for ⁵⁷Fe in silicon in particular. Finally, preliminary results, contributing to the question of the origin and nature of the magnetism in the Fe-doped, dilute magnetic semiconductor ZnO, are given.