Mössbauer Effect in CsI3 and Tri-iodide Complexes of Benzamide and Amylose

Ehrlich, Benjamin S.; Kaplan, M.

doi:10.1063/1.1672041

Cited by 20 publications

(2 citation statements)

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“…The Patterson function for the Cd2+ complex indicated equidistant peaks spaced at 3.1 Á along the 42 axis. In analogy with the previously described Li+ complex and from symmetry requirements of space group P422i2 it was obvious that the -CD molecules are arranged coaxially with the crystallographic c axis, that they have twofold (42) symmetry, and further that the asymmetric unit must contain two crystallographically independent half-a-CD molecules. Because heavy atoms were in special positions and therefore did not contribute in the phasing of general reflections, this crystal structure was solved by trial and error methods using one half-a-CD mole- 0.12 0.17…”

Section: Resultsmentioning

confidence: 83%

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Topography of cyclodextrin inclusion complexes. 12. Structural chemistry of linear .alpha.-cyclodextrin-polyiodide complexes. X-ray crystal structures of (.alpha.-cyclodextrin)2.LiI3.I2.8H2O and (.alpha.-cyclodextrin)2.Cd0.5).I5.27H2O. Models for the blue amylose-iodine complex

Noltemeyer¹,

Saenger²

1980

J. Am. Chem. Soc.

150

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a-Cyclodextrin ( -CD, C36H60O30) is an enzymatic degradation product of amylose (starch). It consists of six (1-*-4) linked glucoses and represents in its annular structure and overall dimensions one turn of the V6 amylose helix. a-CD and starch are able to form inclusion complexes with a variety of guests. With metal iodides in aqueous solution, essentially black, channel-type complexes crystallize in which -CD molecules stack like coins in a roll and in the tubular cavity polyiodide chains are embedded. Depending on the counterion, four different crystal types have been observed: the (pseudo)hexagonal (a-CDL-Kb-b-nFbO (form I), the triclinic (a-CD)2-Lil3'l2-8FI20 (form II), the hexagonal (a-CD)2-BaI2-l2-12H20 (form III), and the tetragonal (a-CD)2-Cdo.5'l5'27H20 (form IV). While for forms I and III only packing of the molecules can be given, the structures of forms II and IV have been studied in detail. In these, countercations are located in interstices between -CD stacks and coordinated with -CD hydroxyls in the case of Li+ (form II) but Cd2+ (form IV) is surrounded by water. This finding suggests that the observed polymorphism is due to different coordination schemes of cations. In complexes II and IV, -CD molecules adopt a "relaxed" form with all 0(5)-C(5)-C(6)-0(6) torsion angles (-)-gauche. They are linked head-to-head via H bonds to form dimers and each dimer accommodates five I atoms. Four of these are in fully occupied positions near planes defined by 0(4) and C( 6) atoms (diameter of cavity ~5.2 Á). The fifth I is where the 0(2), 0(3) rims of adjacent -CD meet and, since the cavity there bulges to ~7 Á, this I is twofold disordered (in ratio 39/61 in II and 50/50 in IV).The polyiodide chain in II is interpreted as (h-b-),, while it is (Is-),, in IV. Distances between I2, I3-, or I5-units are 3.14-4.01 Á, which are in all cases smaller than the van der Waals distance 4.3 Á. The black or blue color effects are due mainly to I-I charge transfer and possibly to I-H but not to I-O interactions. Electrical conductivity is -6 cm-1 along and 10-10 cm-1 perpendicular to the polyiodide chains in these crystals. It is proposed that in the "blue starch-iodine complex" the polyiodide chain is as found in complex II or IV.* Part I 2 of the series "Topography of Cyclodextrin Inclusion Complexes". For part 1 1. see B. Klar. B. Hingerty, and \V. Saenger, Acta Crystallogr., in press.0002-7863/80/1 502-271 OSO 1.00/0 to an aqueous solution of -CD, a cage-type complex of composition -00• 2•4 20 crystallizes as reddish needles.18 Flowever, if iodide anions are present, nearly black crystals showing metallic luster are formed. They belong to the channel-type inclusion compounds and their habitus, colors, and space groups depend strongly on the counterion, Table I. These complexes are of particular interest in relation to the polymeric amylose-iodine complex, because the "infinite columns" of the stacked -CD molecules mimic the amylose helix. The correspondence of matrix dimensions is obvious from the crystal data entere...

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Section: Resultsmentioning

confidence: 83%

“…cooperativity postulated earlier. 40 Móssbauer spectra of amylose-iodine have been discussed on the basis of I3- 41,42 and in recent studies including resonance Raman data43™45 a polyiodide structure consisting of Isand I3-, I2 units has been favored46 (Mizuno and Tanaka (Nagoya), private communication).…”

Section: Introductionmentioning

confidence: 99%

Topography of cyclodextrin inclusion complexes. 12. Structural chemistry of linear .alpha.-cyclodextrin-polyiodide complexes. X-ray crystal structures of (.alpha.-cyclodextrin)2.LiI3.I2.8H2O and (.alpha.-cyclodextrin)2.Cd0.5).I5.27H2O. Models for the blue amylose-iodine complex

Noltemeyer¹,

Saenger²

1980

J. Am. Chem. Soc.

150

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Mössbauer Spectroscopy

Parish¹

2009

Patai's Chemistry of Functional Groups

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Introduction Mössbauer Spectroscopy Interpretation of the Parameters Systems with Carbon–Iodine bonds Charge‐Transfer Complexes The Group IV Tetrahalides Conclusion Acknowledgements

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Normal modes and structure of iodine in the starch–iodine complex

Kim

1982

Biopolymers

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Normal modes of a linear array of iodine atoms with various repeat units, (I 3−), (I 3−I 3−), (I 3−I 2−), and (I 5−), have been calculated. The four resonance Raman bands (158, 107, 57, and 27 cm−1) observed with the starch–iodine complex can be assigned to the symmetric modes of either the (I 3−I 3−)n or (I 5−)n linear chain. However, the nature of the valence force fields of these two structures is very different: the former consists of a weakly coupled linear chain of (I 3−) structure, while the latter, (I 5−)n, is a tightly bound chain approaching equidistant iodine spacings. The nearly equivalent I‐I stretching force constants obtained in the present normal mode analysis of the (I 5−)n structure is supported by the results of previous x‐ray and I‐129 Mössbauer effect measurements. A numerical method of calculating the frequency dispersions of one‐ and two‐dimensional molecular arrays is given.

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Mössbauer Effect in CsI3 and Tri-iodide Complexes of Benzamide and Amylose

Cited by 20 publications

References 18 publications

Topography of cyclodextrin inclusion complexes. 12. Structural chemistry of linear .alpha.-cyclodextrin-polyiodide complexes. X-ray crystal structures of (.alpha.-cyclodextrin)2.LiI3.I2.8H2O and (.alpha.-cyclodextrin)2.Cd0.5).I5.27H2O. Models for the blue amylose-iodine complex

Topography of cyclodextrin inclusion complexes. 12. Structural chemistry of linear .alpha.-cyclodextrin-polyiodide complexes. X-ray crystal structures of (.alpha.-cyclodextrin)2.LiI3.I2.8H2O and (.alpha.-cyclodextrin)2.Cd0.5).I5.27H2O. Models for the blue amylose-iodine complex

Mössbauer Spectroscopy

Normal modes and structure of iodine in the starch–iodine complex

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