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 es...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.展开更多
It is experimentally well established that the phenolic systems such as phenol and diphenols undergo strong hydrogen bonding interaction with water molecule. But, the possible mode hydrogen bonding in phenol-water sys...It is experimentally well established that the phenolic systems such as phenol and diphenols undergo strong hydrogen bonding interaction with water molecule. But, the possible mode hydrogen bonding in phenol-water systems may be of different types. Although, the experimental methods are not always well enough to give the proper hydrogen bonding conformations in the phenol-water complexes. The hydrogen bonding ability in phenol-water systems can directly be influenced by changing the interacting sites in the given molecular systems, which could be investigated by theoretical studies. Generally, in phenol-water system, the hydrogen bonding is taking place through −OH group of phenol with water molecule, and this kind of interactions between phenol-water and diphenol-water complexes have been extensively investigated in electronic ground state by Quantum Mechanical MP4 calculations. It is also very important to study the stability of different phenol-water complexes and to find out the proper phenol-water complexes with minimized interaction energy. This study will also be helpful for understanding the effect of hydrogen bonding interaction in a better way on other aromatic systems.展开更多
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...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.展开更多
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 de...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.展开更多
The use of appropriate level of theories for studying weak interactions such as stacking of aromatic molecules has been an important aspect, since the high level methods have limitations for application to large molec...The use of appropriate level of theories for studying weak interactions such as stacking of aromatic molecules has been an important aspect, since the high level methods have limitations for application to large molecules. The differences in the stacking energies of various structures are found significant for identifying the most favored stacked benzene rings and the pyridine rings. The most favored structure of benzene rings obtained from various methods are similar, and also comparable with that of reported accurate CCSD(T) method. The effect of basis set in the stacking energies of MP2 calculations is small. Thus the moderately accurate methods may be feasible for studying the stacking interactions as demonstrated for benzene and pyridine molecules.展开更多
文摘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.
文摘It is experimentally well established that the phenolic systems such as phenol and diphenols undergo strong hydrogen bonding interaction with water molecule. But, the possible mode hydrogen bonding in phenol-water systems may be of different types. Although, the experimental methods are not always well enough to give the proper hydrogen bonding conformations in the phenol-water complexes. The hydrogen bonding ability in phenol-water systems can directly be influenced by changing the interacting sites in the given molecular systems, which could be investigated by theoretical studies. Generally, in phenol-water system, the hydrogen bonding is taking place through −OH group of phenol with water molecule, and this kind of interactions between phenol-water and diphenol-water complexes have been extensively investigated in electronic ground state by Quantum Mechanical MP4 calculations. It is also very important to study the stability of different phenol-water complexes and to find out the proper phenol-water complexes with minimized interaction energy. This study will also be helpful for understanding the effect of hydrogen bonding interaction in a better way on other aromatic systems.
文摘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.
文摘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.
文摘The use of appropriate level of theories for studying weak interactions such as stacking of aromatic molecules has been an important aspect, since the high level methods have limitations for application to large molecules. The differences in the stacking energies of various structures are found significant for identifying the most favored stacked benzene rings and the pyridine rings. The most favored structure of benzene rings obtained from various methods are similar, and also comparable with that of reported accurate CCSD(T) method. The effect of basis set in the stacking energies of MP2 calculations is small. Thus the moderately accurate methods may be feasible for studying the stacking interactions as demonstrated for benzene and pyridine molecules.