Oraphan Saengsawang

An n-Channel Two-Dimensional Covalent Organic Framework

Co-condensation of metallophthalocyanine with an electron-deficient benzothiadiazole (BTDA) block leads to the formation of a two-dimensional covalent organic framework (2D-NiPc-BTDA COF) that assumes a belt shape and consists of AA stacking of 2D polymer sheets. Integration of BTDA blocks at the edges of a tetragonal metallophthalocyanine COF causes drastic changes in the carrier-transport mode and a switch from a hole-transporting skeleton to an electron-transporting framework. 2D-NiPc-BTDA COF exhibits broad and enhanced absorbance up to 1000 nm, shows panchromatic photoconductivity, is highly sensitive to near-infrared photons, and has excellent electron mobility as high as 0.6 cm(2) V(-1) s(-1).

An Ambipolar Conducting Covalent Organic Framework with Self-Sorted and Periodic Electron Donor-Acceptor Ordering

Covalent organic frameworks (COFs) are crystalline polygons with permanent porosity that have potential application in gas adsorption and storage. [ 1–14 ] π -Electronic versions have also been prepared, by integrating aromatic building blocks into the polygon skeletons. [ 15–25 ] The unusual two-dimensional (2D) conformation endows the frameworks with crystallized layer structures, which could set π -components in face-to-face stacked columns and provide aligned conduction pathways. [ 19–27 ] It is highly interesting and remains a challenge if the unique 2D COF architecture can be explored for the construction of highly aligned donor (D) and acceptor (A) systems. The crystallization of electron donors (D) and acceptors (A) into macroscopic heterojunctions with segregated D and A

How do carbon nanotubes serve as carriers for gemcitabine transport in a drug delivery system

Aiming at understanding the molecular properties of the encapsulation of the anticancer drug gemcitabine in the single-walled carbon nanotube (SWCNT), molecular dynamics (MD) simulations were applied to the two scenarios; that of gemcitabine filling inside the SWCNT, and that of the drug in the free state. Inside the SWCNT, the cytosine ring of gemcitabine was found to form a π-π stacking conformation with the SWCNT surface, and this movement is not along the centerline of the tube from one end to the other of the tube where the distance from the center of gravity of the molecule to the surface is 4.7 Å. A tilted angle of 19° was detected between the cytosine ring of gemcitabine and the inner surface of SWCNT. In comparison to its conformation in the free form, no significant difference was observed on the torsion angle between the five- (ribose) and the six- (cytosine) membered rings. However, gemcitabine inside the SWCNT was found to have a lower number of solvating water molecules but with a stronger net solvation than the drug in the free state. This is due to the collaborative interactions between gemcitabine and the surface of the SWCNT. In addition, the steered molecular dynamics simulation (SMD) approach was employed to investigate the binding free energy for gemcitabine moving from one end to another end throughout the SWCNT. In excellent agreement with that yielded from the classical MD, the SMD energy profile confirms that the drug molecule prefers to locate inside the SWCNT.

Molecular Structure and Electronic Properties of Porphyrin-Thiophene-Perylene Using Quantum Chemical Calculation

This study aimed to design a new series of compounds consisting of a porphyrin macrocycle linked to a perylene unit via a thiophenic bridge. The structural and electronic properties of the molecules, and the effects of mono- and di-substituents R on C3 and R′ on C4 of the thiophene ring were investigated using a quantum calculation approach. The results from the method validation revealed that using the density functional theory approach at B3LYP/6–31G(d) data set was the optimal one, considering the accuracy attained and maintaining the computer time required within tractable limits. The results from the B3LYP/6–31G(d) approach indicated that significant changes of the torsion angle between the molecular planes of the porphyrin and perylene rings, compared to that of the unsubstituted derivatives, were found in the di-substituted systems bearing R = R′ = −OCH3 and −NH2, and in a mono-substituted system having R = −H and R′=−NH2. The symmetric di-substitution does not provide a significantly lower HOMO-LUMO energy gap (). Noticeable decreases in were found only with the substitution patterns of: R, R′ = −OCH3, −H; −OH, −H; −N(CH3)2, −H; −H, −NH2. UV-visible spectra of all derivatives exhibited characteristic absorption maxima of the free bases of porphyrin and perylene.

Structure and electronic properties of deformed single-walled carbon nanotubes: quantum calculations

The electronic properties of single-walled carbon nanotubes (SWCNTs) can be modified by deforming their structure under high pressure. The aim of this study was to use quantum calculations to investigate one such property, the energy band gap, in relation to molecular structures of armchair and zigzag SWCNTs of various sizes and shapes deformed by applied forces. To model the increase in pressure, the degree of flatness (η) of the SWCNTs was adjusted as the primary parameter. The calculations gave accurate C-C bond lengths of the SWCNTs in their distorted states; these distortions significantly affected the electronic properties, especially the energy band gap of the SWCNTs. These results may contribute to a more refined design of new nano-electronic devices.

Energy barrier of water and methane molecules due to the silanol groups on the (010) surface of silicalite-1 as studied by quantum chemical calculations

Quantum mechanical calculations at different levels, HF/6-31G(d,p), B3LYP/6-31G(d,p), HF/6-31++G(d,p), and B3LYP/6-31++G(d,p), have been applied to investigate the interaction between guest molecules, water and methane, and the external surface of silicalite-1. The (010) surface which is perpendicular to the straight channel was selected and the silanol groups on the surface were generated by adding hydrogen atoms to the broken O-Si bonds. The complex geometries were fully optimized. The optimal B3LYP/6-31++G(d,p) binding energies on the external (010) surface of −13.84 kcal/mol and −0.26 kcal/mol were yielded for water and methane molecule, respectively. With the same method, the binding energy in the channel was −4.76 kcal/mol for water and −3.87 kcal/mol for methane binding. This leads to the estimated energy barrier to enter the straight channel via binding with the silanol group on the (010) surface of silicate-1 of 9.08 kcal/mol for water while this process is barrier free for methane molecules.