Optically Active, Amphiphilic Poly(meta-phenylene ethynylene)s: Synthesis, Hydrogen-Bonding Enforced Helix Stability, and Direct AFM Observation of Their Helical Structures

2012 ◽  
Vol 134 (20) ◽  
pp. 8718-8728 ◽  
Author(s):  
Motonori Banno ◽  
Tomoko Yamaguchi ◽  
Kanji Nagai ◽  
Christian Kaiser ◽  
Stefan Hecht ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Optically Active ◽  
Phenylene Ethynylene ◽  
Helical Structures ◽  
Helix Stability ◽  
Afm Observation

Optical activity and enantiomorphism

2004 ◽  
Author(s):  
Robert E. Newnham
Keyword(s):  
Optical Activity ◽  
Polarized Light ◽  
Polarization Vector ◽  
Optically Active ◽  
Crystal Thickness ◽  
Helical Structures ◽  
Active Materials ◽  
Circularly Polarized ◽  
Space Groups ◽  
Polarized Waves

When plane-polarized light enters a crystal it divides into right- and lefthanded circularly polarized waves. If the crystal possesses handedness, the two waves travel with different speeds, and are soon out of phase. On leaving the crystal, the circularly polarized waves recombine to form a plane polarized wave, but with the plane of polarization rotated through an angle αt. The crystal thickness t is in mm, and α is the optical activity coefficient expressed in degrees/mm. The polarization vector of the combined wave can be visualized as a helix, turning α ◦/mm path length in the optically-active medium. Because of the low symmetry of a helix, optical activity is not observed in many high symmetry crystals. Point groups possessing a center of symmetry are inactive. In relating α to crystal chemistry it is convenient to divide optically-active materials into two categories: Those which retain optical activity in liquid form, and those which do not. It has long been known that optically-active solutions crystallize to give optically-active solids. This follows from the fact that molecules lacking mirror or inversion symmetry can never crystallize in a pattern containing such symmetry elements. Thus one way of obtaining optically-active materials is to begin with optically-active molecules, as in Rochelle salt, tartaric acid and cane sugar. Few of these crystals are very stable, however, and the optical activity coefficients are usually small, typically 2◦/mm. The same is true of many inorganic solids, though they are seldom optically active in the liquid state. For NaClO3 and MgSO4·7H2O, α is about 3◦/mm. Quartz and selenium, however, have coefficients an order of magnitude larger, showing the importance of helical structures to optical activity. Both compounds crystallize as right- and left-handed forms in space groups P312 and P322, with helices spiraling around the trigonal screw axes. Quartz contains nearly regular SiO4 tetrahedra with Si–O distances of 1.61 Å. Levorotatory quartz belongs to space group P312 and contains right-handed helices; enantiomorphic dextrorotatory quartz crystallizes in P322. Trigonal selenium also contains helical chains.

Dynamic optical activity induction in the N-alkyl-N′-trityl ureas and thioureas

2019 ◽  
Vol 17 (33) ◽  
pp. 7782-7793 ◽  
Author(s):  
Natalia Prusinowska ◽  
Agnieszka Czapik ◽  
Martika Wojciechowska ◽  
Marcin Kwit
Keyword(s):  
Hydrogen Bonding ◽  
Optical Activity ◽  
Optically Active ◽  
Thiourea Derivatives ◽  
Hydrogen Bonding Network ◽  
Activity Induction

Stereodynamic trityl group, utilized as a reporter of chirality, hampers hydrogen bonding network in optically active urea and thiourea derivatives.

Variations on a Cage Theme: Some Complexes of Bicyclic Polyamines as Supramolecular Synthons

2009 ◽  
Vol 62 (10) ◽  
pp. 1246 ◽  
Author(s):  
Ian J. Clark ◽  
Alessandra Crispini ◽  
Paul S. Donnelly ◽  
Lutz M. Engelhardt ◽  
Jack M. Harrowfield ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Aromatic Ring ◽  
Oxidation State ◽  
Metal Ion ◽  
Intermolecular Forces ◽  
Optically Active ◽  
Alphabetical Order ◽  
Supramolecular Synthons ◽  
Π Stacking ◽  
Parallel Arrays

Dedication: One of Alan Sargeson’s great abilities was to seek out knowledge on topics of which he was not the master from those people with the expertise. This led occasionally to publications with a ‘cricket team’ of authors but with a rich brew of information, often international. Alan also insisted that all authors were equal since, without any one, the paper would not be what it was. Hence, he endeavoured to pursue the policy, difficult to maintain over a period where an obsession with absurdities such as the order of authors and point-scoring based on meaningless publication indices became so important in the maintenance of research, of listing authors simply in alphabetical order. In describing work begun while he was still with us, we have attempted to adhere to his principles. Analysis of a body of crystallographic information concerning metal(ii) and metal(iii) complexes of macrobicyclic hexamine ligands and some of their derivatives provides evidence for the action of a variety of intermolecular forces within the lattices. Hydrogen bonding is universal and its forms depend strongly upon the oxidation state and the particular nature of the metal ion bound to the macrobicycle. The introduction of both aliphatic and aromatic substituents leads to lattices in which these substituents associate, although, in the case of aromatic substituents, this is not necessarily a consequence of ‘π-stacking’, despite the fact that the aromatic ring planes form parallel arrays. At least in the case of CoIII, stable enantiomers of the complexes can be obtained, and in {Δ-(+)589-[Co{(NH3)(CH3)sar}]}2Cl2(C6(CO2)6)·26H2O (sar = 3,6,10,13,16,19-hexa-azabicyclo[6.6.6]icosane), the benzene hexacarboxylate anion adopts a chiral conformation in the presence of the optically active cation.

scholarly journals (2R,2′S)-2,2′-Bipiperidine-1,1′-diium dibromide

2013 ◽  
Vol 69 (11) ◽  
pp. o1711-o1711 ◽  
Author(s):  
Guang Yang ◽  
Bruce C. Noll ◽  
Elena V. Rybak-Akimova
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Title Compound ◽  
Optically Active ◽  
Organic Cations ◽  
Al Alloy ◽  
Inversion Center ◽  
Compound C ◽  
Organic Moiety ◽  
Counter Ions

The title compound, C10H22N22+·2Br−, was synthesizedviareduction of 2,2′-dipyridyl with Ni–Al alloy/KOH, followed by separation of diastereoisomers (mesoandrac) by recrystallization from ethanol. Although the two bridging C atoms are optically active, these two chiral centers adopt an (S,R) configuration; thus, the title compound contains an achiralmesoform of 2,2′-bipiperidine. Both of the piperidinium rings adopt chair conformations, and the two N atoms aretransto each other; an inversion center is located in the mid-point of the central C—C bond. The conformation of the organic moiety resembles that of 1,1′-bi(cyclohexane). The organic diammonium cations are linked to each other through hydrogen bonding with bromide counter-ions, each of which forms two hydrogen bonds (N—H...Br) with two adjacent organic cations, thus linking the latter together in sheets parallel to (100).

Controlling them-Poly(phenylene ethynylene) Helical Cavity Environment: Hydrogen Bond Stabilized Helical Structures

2011 ◽  
Vol 44 (1) ◽  
pp. 60-67 ◽  
Author(s):  
Ha H. Nguyen ◽  
James H. McAliley ◽  
David A. Bruce
Keyword(s):  
Hydrogen Bond ◽  
Phenylene Ethynylene ◽  
Helical Structures
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