scholarly journals Steering the Conformation and Chiroptical Properties of Poly(dithienopyrrole)s Substituted with Chiral OPV Side Chains.

2010 ◽  
Vol 43 (5) ◽  
pp. 2157-2168 ◽  
Author(s):  
Wouter Vanormelingen ◽  
Lesley Pandey ◽  
Mark Van der Auweraer ◽  
Thierry Verbiest ◽  
Guy Koeckelberghs
Keyword(s):  
Side Chains ◽  
Chiroptical Properties

scholarly journals Effect of chiral 2-ethylhexyl side chains on chiroptical properties of the narrow bandgap conjugated polymers PCPDTBT and PCDTPT

2016 ◽  
Vol 7 (8) ◽  
pp. 5313-5321 ◽  
Author(s):  
Stephanie L. Fronk ◽  
Ming Wang ◽  
Michael Ford ◽  
Jessica Coughlin ◽  
Cheng-Kang Mai ◽  
...  
Keyword(s):  
Conjugated Polymers ◽  
Side Chains ◽  
Chiroptical Properties ◽  
Narrow Bandgap

PCPDTBT* and PCDTPT* containing chiral 2-ethylhexyl side chains were synthesized and their resulting chiroptical properties were studied. PCPDTBT* exhibits a stronger chiroptical response compared to PCDTPT*.

Synthesis and chiroptical properties of heterodetic cyclic hexapeptides related to oxytocin ring moiety

1980 ◽  
Vol 45 (4) ◽  
pp. 1109-1131 ◽  
Author(s):  
Ivo Frič ◽  
Lyudmila I. Leonteva ◽  
Petr Maloň ◽  
Karel Jošt ◽  
Karel Bláha
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Peptide Synthesis ◽  
Spatial Arrangement ◽  
Cd Spectroscopy ◽  
Side Chains ◽  
Peptide Backbone ◽  
Chiroptical Properties ◽  
Disulfide Group ◽  
Cyclic Hexapeptides

Cyclic disulfides of cysteinyl-tetraglycyl-cysteine (Ia), cysteinyl-tyrosyl-triglycyl-cysteine (Ib) and cysteinyl-tyrosyl-isoleucyl-diglycyl-cysteine (Ic) were synthesized by classical methods of peptide synthesis. The actions of solvent and of side chains in the positions 2 and 3 on the conformational arrangement of the peptide backbone and the disulfide group were investigated by means of CD spectroscopy. Some mechanisms which co-operate in stabilizing the oxytocin conformation were identified. Hence, it may be deduced, that the amino acid sequence in the positions 1-3 determines the spatial arrangement characteristic for oxytocin, at least in a protonating medium.

Synthesis and chiroptical properties of novel helical polyacetylenes containing fluorene pendant groups in the side chains

2016 ◽  
Vol 109 ◽  
pp. 131-136 ◽  
Author(s):  
Yuping Liu ◽  
Shujing Li ◽  
Qingzhong Zhang ◽  
Jing Zhang ◽  
Chunping Du ◽  
...  
Keyword(s):  
Side Chains ◽  
Chiroptical Properties

Chiroptical Properties of a Benzotriazole–Thiophene Copolymer Bearing Chiral Ethylhexyl Side Chains

2016 ◽  
Vol 49 (24) ◽  
pp. 9301-9308 ◽  
Author(s):  
Stephanie L. Fronk ◽  
Yueqin Shi ◽  
Martin Siefrid ◽  
Cheng-Kang Mai ◽  
Caitlin McDowell ◽  
...  
Keyword(s):  
Side Chains ◽  
Chiroptical Properties

Influence of Flexible Side-Chains on the Breathing Phase Transition of Pillared Layer MOFs: A Force Field Investigation

2020 ◽  
Author(s):  
Julian Keupp ◽  
Johannes P. Dürholt ◽  
Rochus Schmid
Keyword(s):  
First Principles ◽  
Good Accuracy ◽  
Field Investigation ◽  
Square Lattice ◽  
Side Chain ◽  
Second Step ◽  
Side Chains ◽  
Dynamics Simulations ◽  
Complex Phenomena ◽  
Closed Pore

The prototypical pillared layer MOFs, formed by a square lattice of paddle-<br>wheel units and connected by dinitrogen pillars, can undergo a breathing phase<br>transition by a “wine-rack” type motion of the square lattice. We studied this not<br>yet fully understood behavior using an accurate first principles parameterized force<br>field (MOF-FF) for larger nanocrystallites on the example of Zn 2 (bdc) 2 (dabco) [bdc:<br>benzenedicarboxylate, dabco: (1,4-diazabicyclo[2.2.2]octane)] and found clear indi-<br>cations for an interface between a closed and an open pore phase traveling through<br>the system during the phase transformation [Adv. Theory Simul. 2019, 2, 11]. In<br>conventional simulations in small supercells this mechanism is prevented by periodic<br>boundary conditions (PBC), enforcing a synchronous transformation of the entire<br>crystal. Here, we extend this investigation to pillared layer MOFs with flexible<br>side-chains, attached to the linker. Such functionalized (fu-)MOFs are experimen-<br>tally known to have different properties with the side-chains acting as fixed guest<br>molecules. First, in order to extend the parameterization for such flexible groups,<br>1a new parametrization strategy for MOF-FF had to be developed, using a multi-<br>structure force based fit method. The resulting parametrization for a library of<br>fu-MOFs is then validated with respect to a set of reference systems and shows very<br>good accuracy. In the second step, a series of fu-MOFs with increasing side-chain<br>length is studied with respect to the influence of the side-chains on the breathing<br>behavior. For small supercells in PBC a systematic trend of the closed pore volume<br>with the chain length is observed. However, for a nanocrystallite model a distinct<br>interface between a closed and an open pore phase is visible only for the short chain<br>length, whereas for longer chains the interface broadens and a nearly concerted trans-<br>formation is observed. Only by molecular dynamics simulations using accurate force<br>fields such complex phenomena can be studied on a molecular level.

Pathway Complexity in the Stacking of Imine-linked Macrocycles Related to Two-Dimensional Covalent Organic Frameworks

2019 ◽  
Author(s):  
Shiwei Wang ◽  
Anton Chavez ◽  
Simil Thomas ◽  
Hong Li ◽  
Nathan C. Flanders ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Structural Similarity ◽  
Discrete Models ◽  
Side Chains ◽  
Two Dimensional ◽  
Assembly Process ◽  
Covalent Organic Frameworks ◽  
Electron Systems ◽  
Monomer Structure ◽  
Kinetic Traps

This work reports on the assembly of imine-linked macrocycles that serve as models of two-dimensional covalent organic frameworks (2D COFs). Interlayer interactions play an important role in the formation of 2D COFs, yet the effect of monomer structure on COF formation, crystallinity, and susceptibility to exfoliation are not well understood. For example, monomers with both electron-rich and electron-poor π-electron systems have been proposed to strengthen interlayer inter-actions and improve crystallinity. Here we probe these effects by studying the stacking behavior of imine-linked macrocycles that represent discrete models of 2D COFs. <div><br></div><div>Specifically, macrocycles based on terephthaldehyde (PDA) or 2,5-dimethoxyterephthaldehyde (DMPDA) stack upon cooling molecularly dissolved solutions. Both macrocycles assemble cooperatively with similar ΔHe values of -97 kJ/mol and -101 kJ/mol, respectively, although the DMPDA macrocycle assembly process showed a more straightforward temperature dependence. Circular dichroism spectroscopy performed on macrocycles bearing chiral side chains revealed a helix reversion process for the PDA macrocycles that was not observed for the DMPDA macrocycles. <br></div><div><br></div><div>Given the structural similarity of these monomers, these findings demonstrate that the stacking processes associated with nanotubes derived from these macrocycles, as well as for the corresponding COFs, are complex and susceptible to kinetic traps, casting doubt on the relevance of thermodynamic arguments for improving materials quality. <br></div>

Predicting the Strength of Stacking Interactions Between Heterocycles and Aromatic Amino Acid Side Chains

2019 ◽  
Author(s):  
Andrea N. Bootsma ◽  
Analise C. Doney ◽  
Steven Wheeler
Keyword(s):  
Amino Acid ◽  
Binding Sites ◽  
Aromatic Amino Acid ◽  
Aromatic Amino Acids ◽  
Biologically Active ◽  
Side Chains ◽  
Stacking Interactions ◽  
Inhibitor Binding ◽  
Protein Binding Sites ◽  
Amino Acid Side Chains

<p>Despite the ubiquity of stacking interactions between heterocycles and aromatic amino acids in biological systems, our ability to predict their strength, even qualitatively, is limited. Based on rigorous <i>ab initio</i> data, we have devised a simple predictive model of the strength of stacking interactions between heterocycles commonly found in biologically active molecules and the amino acid side chains Phe, Tyr, and Trp. This model provides rapid predictions of the stacking ability of a given heterocycle based on readily-computed heterocycle descriptors. We show that the values of these descriptors, and therefore the strength of stacking interactions with aromatic amino acid side chains, follow simple predictable trends and can be modulated by changing the number and distribution of heteroatoms within the heterocycle. This provides a simple conceptual model for understanding stacking interactions in protein binding sites and optimizing inhibitor binding in drug design.</p>

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