scholarly journals Cholic acid dimers as invertible amphiphilic pockets: synthesis, molecular modeling, and inclusion studies

2017 ◽  
Vol 95 (7) ◽  
pp. 792-798 ◽  
Author(s):  
Meng Zhang ◽  
Nicolas Levaray ◽  
Josée R. Daniel ◽  
Karen C. Waldron ◽  
X.X. Zhu
Keyword(s):  
Free Energy ◽  
Molecular Modeling ◽  
Cholic Acid ◽  
Organic Solvents ◽  
Sodium Salt ◽  
Organic Media ◽  
Fluorescence Studies ◽  
Complexation Process ◽  
Formation Of Complexes ◽  
Coumarin 343

Two dimers of cholic acid were synthesized through simple covalent linkers. The dimers form invertible molecular pockets in media of different polarity; hydrophobic pockets are formed in water and hydrophilic pockets are formed in organic media. Fluorescence studies show that pockets formed by these dimers can serve as invertible hosts for the hydrophobic guest pyrene and the hydrophilic guest coumarin 343. The molecular pocket also enhances dissolution of the weakly soluble cresol red sodium salt in organic media. Molecular modeling was performed to better understand the host–guest complexation process of the invertible amphiphilic pockets. The calculated free energy changes indicate that the two dimers form the most stable complexes with coumarin 343 at a host to guest ratio of 2:2, whereas the host to guest ratio differs in the formation of complexes with pyrene for the two dimers. The dimer with the shorter, less flexible linker seems to form host–guest complexes that are more stable in both water and organic solvents.

Bundlet Model for Single-Wall Carbon Nanotubes, Nanocones and Nanohorns

2012 ◽  
Vol 2 (1) ◽  
pp. 48-98 ◽  
Author(s):  
Francisco Torrens ◽  
Gloria Castellano
Keyword(s):  
Carbon Nanotubes ◽  
Free Energy ◽  
Distribution Function ◽  
Carbon Nanotube ◽  
Interaction Energy ◽  
Organic Solvents ◽  
Cone Angle ◽  
Single Wall Carbon Nanotubes ◽  
Carbon Nanocones ◽  
Single Wall Carbon

This paper discusses the existence of single-wall carbon nanocones (SWNCs), especially nanohorns (SWNHs), in organic solvents in the form of clusters. A theory is developed based on a bundlet model describing their distribution function by size. Phenomena have a unified explanation in bundlet model in which free energy of an SWNC, involved in a cluster, is combined from two components: a volume one, proportional to number of molecules n in a cluster, and a surface one proportional to n1/2. Bundlet model enables describing distribution function of SWNC clusters by size. From purely geometrical differences, bundlet (SWNCs) and droplet (fullerene) models predict different behaviours. The SWNCs of various disclinations are investigated via energetic–structural analyses. Several SWNC’s terminations are studied, which are different among one another because of type of closing structure and arrangement. The packing efficiencies and interaction-energy parameters of SWNCs/SWNHs are intermediate between fullerene and single-wall carbon nanotube (SWNT) clusters; an in-between behaviour is expected. However, the properties of SWNCs, especially SWNHs, are calculated close to SWNTs. The structural asymmetry in the different SWNCs, entirely characterized by their cone angle, distinguishes the properties of some, such as P2.

scholarly journals Super Extended Calix[4]Pyrroles as Candidate for Binding Mercury

2018 ◽  
Vol 34 (6) ◽  
pp. 2789-2795
Author(s):  
Maan Al-Nuaim ◽  
H. N. K. AL-Salman ◽  
Hussein H. Hussein
Keyword(s):  
Thermodynamic Parameters ◽  
Organic Solvents ◽  
1H Nmr ◽  
Strong Interaction ◽  
Ester Group ◽  
Hydroxyl Group ◽  
Ester Derivative ◽  
Anion Complexation ◽  
Calorimetric Studies ◽  
Complexation Process

The binding of mercury Hg (II) by calix[4]pyrrole derivative; 2 has been much less discovered than anion complexation. The presence of hydroxyl group in the structure of meso-tetramethyl-tetrakis-[2(4-hydroxyphenyl)ethylcalix[4]pyrrole is important for further modifications in the next steps. The modification of the hydroxyl group by the substitution of ester group was carried out to produce the ester derivative for the modified calix[4]pyrrole 2. The ester group would be expected to deliver high electronic contributions in the complexation processes with the guests as well as to increase the solubility of the receptor in different organic solvents. 1H NMR and isothermal titration calorimetric studies revealed that the receptors exhibited strong interaction with mercury cation and the complexation process was driven enthalpically and entropically. Conductance measurements in acetonitrile were carried out to identify the composition of the formed complex. From Nano Isothermal Titration Calorimetric studies, the thermodynamic parameters for the complexation processes were calculated.

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