Hydrogen-Bond-Assisted Helical Folding of Propeller-Shaped Molecules: Effects of Extended π-Conjugation on Chiral Selection, Conformational Stability, and Exciton Coupling

2011 ◽  
Vol 2012 (4) ◽  
pp. 708-720 ◽  
Author(s):  
Elizabeth A. Opsitnick ◽  
Xuan Jiang ◽  
Andrew N. Hollenbeck ◽  
Dongwhan Lee
Keyword(s):  
Hydrogen Bond ◽  
Conformational Stability ◽  
Chiral Selection ◽  
Exciton Coupling ◽  
Helical Folding

Influence of the geometry of a hydrogen bond on conformational stability: a theoretical and experimental study of ethyl carbamate

2009 ◽  
Vol 11 (11) ◽  
pp. 1719 ◽  
Author(s):  
M. Goubet ◽  
R. A. Motiyenko ◽  
F. Réal ◽  
L. Margulès ◽  
T. R. Huet ◽  
...  
Keyword(s):  
Experimental Study ◽  
Hydrogen Bond ◽  
Conformational Stability ◽  
Ethyl Carbamate

scholarly journals Temperature and H/D Isotopic Effects in the IR Spectra of the Hydrogen Bond in Solid-State 2-Furanacetic Acid and 2-Furanacrylic Acid

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Henryk T. Flakus ◽  
Anna Jarczyk-Jędryka
Keyword(s):  
Hydrogen Bond ◽  
Electronic Structure ◽  
Ir Spectra ◽  
Close Relation ◽  
Coupling Mechanism ◽  
Band Frequency ◽  
Molecular Systems ◽  
Exciton Coupling ◽  
Relative Contribution ◽  
Type Coupling

Polarized IR spectra of 2-furanacetic acid and of 2-furanacrylic acid crystals were measured at 293 K and 77 K in the vO−H and vO−H band frequency ranges. The corresponding spectra of the two individual systems strongly differ, one from the other, by the corresponding band shapes as well as by the temperature effect characterizing the bands. The crystal spectral properties remain in a close relation with the electronic structure of the two different molecular systems. We show that a vibronic coupling mechanism involving the hydrogen bond protons and the electrons on the π-electronic systems in the molecules determines the way in which the vibrational exciton coupling between the hydrogen bonds in the carboxylic acid dimers occurs. A strong coupling in 2-furanacrylic acid dimers prefers a “tail-to-head-” type Davydov coupling widespread by the π-electrons. A weak through-space coupling in 2-furanacetic acid dimers is responsible for a “side-to-side-” type coupling. The relative contribution of each exciton coupling mechanism in the dimer spectra generation is temperature and the molecular electronic structure dependent. This explains the observed difference in the temperature-induced evolution of the compared spectra.

Indole-based macrocycles and oligomers binding anions

2008 ◽  
Vol 80 (3) ◽  
pp. 599-608 ◽  
Author(s):  
Jae-min Suk ◽  
Min Kyung Chae ◽  
Nam-Kyun Kim ◽  
Uk-Il Kim ◽  
Kyu-Sung Jeong
Keyword(s):  
Hydrogen Bond ◽  
Binding Affinities ◽  
Binding Modes ◽  
Helical Structures ◽  
Binding Properties ◽  
Molecular Building Block ◽  
Internal Cavities ◽  
Sonogashira Reactions ◽  
Helical Folding ◽  
Hydrogen Bond Donors

Indole-based synthetic receptors which bind anions by multiple hydrogen bonds in organic solvents have been prepared. The biindole scaffold bearing two good hydrogen bond donors of indole NHs has been used as a molecular building block to construct the receptors. Incorporation of more hydrogen bond donors or acceptors increases the binding strength and selectivity toward a specific ion. Two macrocycles having different sizes of the internal cavities have been also synthesized, and their binding properties have been compared. Two macrocycles display distinct binding modes with polyatomic anions such as azide, as unequivocally proven by X-ray crystal structures. Finally, a series of oligoindoles containing four, six, and eight indoles have been prepared by Sonogashira reactions. The oligoindoles fold into helical structures upon binding with chloride. The binding affinities of the oligoindoles with chloride increase with increasing of the chain length, which provides an additional evidence for helical folding of the complexes.

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