The stacking of phenanthroline(phen) ligand within base pair sequences is one of the important factors for the stabilization of metalphen complex within DNA. The stacking ability of this ligand has been assessed to deduce the base pair selectivity as well as to identify the favored region of intercalation. Different level of theories have been used to predict the favorable regions for stacking interaction of phen ligand with base pair, but the results of MP2/6-31+G(d,p) is found to be reasonably good for monitoring such interactions

Aromatic systems like phenol, diphenol, cyano benzene, chloro benzene, aniline etc shows effective π-π stacking interactions, long range van der Waals forces; ion-π interactions etc. and these forces of interactions play an crucial role in the stability of stacked π-dimeric system. On the other hand, substituents and conformational change in the stacked dimmers of aromatic system may also change the stability of different stacked dimers. In this current study, stacked phenolic dimmers (both phenol and diphenol) have been taken for investigation of the stacking π-π interaction. But, the stacking interactions are also greatly affected by the conformational change with internal rotation (i.e. dihedral angle, φ) between the stacked dimers. It is generally accepted that larger basis sets are required for the highly accurate calculation of interaction energies for any stacked aromatic models. But, it has recently been reported that M062X/6-311++G(d,p) basis set is effectively better than that of B3LYP/6-311++G(d,p) for determining the interaction energies for any kind of long range interaction in aromatic systems. Therefore, all the calculations were carried out by using M062X/6-311++G(d,p) basis set. However, in most of the cases the calculated π-π stacking interaction energies show almost same result for both DFT and ab initio methods.

This work reports the low-cost exfoliation of graphene oxide (GO) from pencil lead using modified Hummer's method. The gold nanoparticles ( AuNPs ) supported on GO is prepared via an in situ bio reduction of HAuCl 4 by polyphenolic biomolecules present in young leaves of tea (Camellia sinensis) extracted in the presence of GO. The UV-Visible absorption spectrum of GO dispersion in water exhibits two bands at 228 nm and a shoulder at ~ 300 nm corresponding to π–π* transitions of aromatic C – C bonds and n–π* transitions of C = O bonds. In photoluminescence (PL) study, GO dispersion in water shows an emission band at 555 nm, when excited at 325 nm. When AuNPs are supported on GO nanosheets the bands at 228 nm and ~ 300 nm of GO disappears and two new UV-Visible bands at 229 nm for π–π* (for C = C ) and 550 nm for transverse surface plasmon resonance (TSPR) of AuNPs appears. When AuNPs are supported on GO nanosheets, PL emission band at 555 nm disappears and two new PL emission bands appear at 431 nm and 658 nm. The physical and morphological characterizations are performed by Fourier-transform infrared (FT-IR), X-ray diffraction (XRD), High-resolution-transmission electron microscopy (HR-TEM) and BET surface area measurement. Morphological studies revealed that the GO nanosheets are well dispersed in water and AuNPs are supported on the GO nanosheets.

No abstract

Non covalent interactions are quite common in all kinds of π-systems, such as π-π interactions, long range/short range van der waal force of interactions, ion-π interactions etc. Ab initio calculations are well established and account well for the experimental long range interaction energies for small clusters of aromatic molecules and most of the calculations were carried out using the MPn methods. If a reasonably large basis set is used to calculate the stacking interaction energies for a cluster (dimer, trimer etc.) of aromatic molecules then the electron-electron correlation energy may be properly calculated.Moreover, ab initio calculations for aromatic π-systems show that the calculated stacking interaction energies highly depend on the basis set used and the electron correlation energy. In this investigation, the electron correlation of the stacked hydrated phenol systems has been accounted at MP2 level of calculations. We have calculated the π-π stacking interaction energies of the hydrated phenolic systems with different conformations.