Geometrical isomers of [Ph2P(CH2)2AuX2]2. Crystal and molecular structures of trans,trans-[Ph2P(CH2)2AuBr2]2 and cis,trans-[Ph2P(CH2)2AuCl2]2

1985 ◽  
Vol 24 (23) ◽  
pp. 3758-3762 ◽  
Author(s):  
Douglas S. Dudis ◽  
John P. Fackler
Keyword(s):  
Molecular Structures ◽  
Geometrical Isomers ◽  
Crystal And Molecular Structures

Crystal and Molecular Structures of the Free Base and the Monohydrochloride Salt of the Antileukemic Agent Glyoxal bis(Amidinohydrazone) [`Glyoxal bis(Guanylhydrazone)’]

1993 ◽  
Vol 48 (12) ◽  
pp. 1821-1827 ◽  
Author(s):  
Ilpo Mutikainen ◽  
Hannu Elo ◽  
Pirkko Tilus
Keyword(s):  
Solid State ◽  
Molecular Structures ◽  
Monoclinic Space Group ◽  
Free Base ◽  
X Ray Diffraction ◽  
Geometrical Isomers ◽  
Space Group ◽  
Crystal And Molecular Structures ◽  
Hydrogen Bond Networks ◽  
The Mean

The first study on the crystal and molecular structures of basic forms of bis(amidinohydrazones) is reported. The structures of the free base and the monohydrochloride salt of the antileukemic agent glyoxal bis(amidinohydrazone) (GBG) were determined by single crystal X-ray diffraction and were refined to R-values of 0.038 and 0.040, respectively. These structures are of special interest because recent results indicate that, in contrast to previous assumptions, the free base may be the actual antileukemic form of bis(amidinohydrazones) and that the monocation form is the predominant species of antileukemic bis(amidinohydrazones) at physiological conditions. In the crystals of the free base as well as in those of the monohydrochloride salt, GBG was found to exist solely in the all-trans configuration of the chain and to consist of one of the three possible geometrical isomers only. In the solid state, GBG free base consists solely of the endiamine tautomer instead of the 'classical’ carboximidamide tautomer, as does also the non-protonated part of GBG monocation in the monohydrochloride salt. Proton NMR measurements indicated that the free base consists of the endiamine tautomer also in dimethyl sulfoxide solution. In the solid state, both of the compounds studied consist of stacks of planes. In the case of the free base, the stacks are crisscross to each other. The distance between the mean planes of the molecules or the monocations is approximately 3.5 Å. The crystals of the monohydrochloride salt contain one molecule of water per each GBG monocation. In both compounds studied, the molecules in the crystals are held together by very extensive hydrogen bond networks and by the interaction of delocalized π-electrons. The crystal of C4H10N8 is monoclinic, space group C2/c with a = 15.874(6), b = 6.972(4), c = 7.8l3(5)Å, β = 90.34(4)° and Z = 4. The crystal of C4H13N8OC1 is monoclinic, space group P21/n with α = 7.010(3), b = 22.307(9), c = 7.028(3)Å, β = 66.33(3)° and Ζ = 4.

Crystal and Molecular Structures of Two Isomers of Phenylglyoxal Bis(amidinohydrazone) [‘Phenylglyoxal Bis(guanylhydrazone)’] Sulphate

1996 ◽  
Vol 51 (8) ◽  
pp. 1161-1172 ◽  
Author(s):  
Mikko Koskinen ◽  
Ilpo Mutikainen ◽  
Hannu Elo
Keyword(s):  
Aqueous Ethanol ◽  
Resonance Effect ◽  
Volume Ratio ◽  
Phenyl Group ◽  
Biochemical Properties ◽  
Molecular Structures ◽  
Geometrical Isomers ◽  
Crystal And Molecular Structures ◽  
First Case ◽  
Internal Hydrogen Bond

The first crystallographic study on an aromatic analogue of the antileukemic agent methylglyoxal bis(amidinohydrazone) (MGBG) is reported. Thus, the crystal and molecular structures of two different geometrical isomers of phenylglyoxal bis(amidinohydrazone) (PhGBG) sulphate were determined by single-crystal X-ray diffraction. Crystals were prepared by recrystallizing PhGBG sulphate using either water or aqueous ethanol (volume ratio ethanol:water 1:4) as the solvent. Depending on the solvent, different types of crystals were obtained although the PhGBG sulphate employed was in the both cases from the same synthesis batch that had been prepared according to classical methods from the corresponding glyoxal. When a crystal obtained from water was studied, PhGBG was found to exist solely in the form of the anti-anti isomer. e. the same isomer that has been observed in the cases of all mono- and dialkylglyoxal bis(amidinohydrazones) so far studied. However, when PhGBG sulphate was recrystallized from 20 % aqueous ethanol, the crystals obtained consisted of a different geometrical isomer. In this anti-syn isomer the carbon-nitrogen double bond closest to the phenyl group had the syn configuration. In the anti-syn isomer, there is an internal hydrogen bond between the two amidinohydrazone moieties, which may markedly contribute to the stabilization of the isomer. The anti-syn isomer of PhGBG is analogous to the only isomer of trifluoromethylglyoxal bis(amidinohydrazone) so far observed. PhGBG sulphate constitutes the first case in which two different geometrical isomers of a bis(amidinohydrazone) have been observed. In the case of the much studied aliphatic mono- and dialkylglyoxal analogues, isomerization of the bis(amidinohydrazone) backbone has never been observed. The structural flexibility of the bis(amidinohydrazone) chain of PhGBG is obviously attributable to the electron-withdrawing resonance effect and perhaps also to the inductive and hyperconjugative effects of the phenyl group. The obviously facile isomerization of PhGBG may markedly influence the biochemical properties of the compound.

A Solvent-Dependent and Electrochemically Controlled Self-Assembling/Disassembling System

2003 ◽  
Vol 68 (9) ◽  
pp. 1647-1662 ◽  
Author(s):  
Valeria Amendola ◽  
Massimo Boiocchi ◽  
Yuri Diaz Fernandez ◽  
Carlo Mangano ◽  
Piersandro Pallavicini
Keyword(s):  
Equilibrium Mixture ◽  
Bidentate Ligand ◽  
Molecular Structures ◽  
The Self ◽  
Molar Ratio ◽  
Crystal And Molecular Structures ◽  
Self Assembling ◽  
Irreversible Oxidation ◽  
Irreversible Reduction ◽  
Metal Ligand

The bis-bidentate ligand R,S-1,2-diphenyl-N,N'-bis(2-quinolinemethylidene)ethane-1,2-diamine (ligand 4), containing two (iminomethyl)quinoline moieties separated by a cis-1,2-diphenylethylene spacer, forms stable complexes with both CuI and CuII. With CuII, the monomeric 1:1 complex [CuII(4)]2+ is obtained both in CH3CN and CH2Cl2. With CuI and overall 1:1 metal/ligand molar ratio, an equilibrium mixture is obtained in CH3CN, consisting of [CuI(4)2]+, [CuI2(4)2]2+ and [CuI2(4)(CH3CN)4]2+. The preponderant species is the two-metal one-ligand "open" complex [CuI2(4)(CH3CN)4]2+, in which each Cu+ cation is coordinated in a tetrahedral fashion by one (iminomethyl)quinoline unit and by two CH3CN molecules. Precipitation from the equilibrium mixture yields only crystals of [CuI2(4)(CH3CN)4](ClO4)2·2CH3CN, whose crystal and molecular structures have been determined. On the other hand, in the poorly coordinating CH2Cl2 solvent, only the dimeric helical [CuI2(4)2]2+ complex is obtained, when the overall metal/ligand 1:1 molar ratio is chosen. Addition of large quantities of acetonitrile to solutions of [CuI2(4)2]2+ in dichlorometane results in the formation of [CuI2(4)(CH3CN)4]2+, i.e. in the solvent-driven disassembling of the CuI helicate. While electrochemistry in CH3CN is poorly defined due to the presence of more than one CuI species, cyclic voltammetry experiments carried out in CH2Cl2 revealed a well defined behavior, with irreversible oxidation of [CuI2(4)2]2+ and irreversible reduction of [CuII(4)]2+ taking place at separate potentials (∆E ≈ 700 mV). Irreversibility and separation of the redox events are due to the self-assembling and disassembling processes following the reduction and oxidation, respectively.

Synthesis of Trispirocyclotriphosphazenes with Oxaphosphorine Rings and Their Crystal and Molecular Structures

2021 ◽  
Vol 60 (7) ◽  
pp. 5014-5020
Author(s):  
Yuji Tada ◽  
Atsushi Sunada ◽  
Riki Watanabe ◽  
Makoto Kanazawa ◽  
Keiichiro Utsumi
Keyword(s):  
Molecular Structures ◽  
Crystal And Molecular Structures
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