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R Parthasarathi

Publications and source records attributed to R Parthasarathi.

22 records · Page 2Linked to original sources
PubMed2005

Hydrogen bonding in phenol, water, and phenol-water clusters.

Structure, stability, and hydrogen-bonding interaction in phenol, water, and phenol-water clusters have been investigated using ab initio and density functional theoretical (DFT) methods and using various topological features of electron density. Calculated interaction energies at MP2/6-31G level for clusters with similar hydrogen-bonding pattern reveal that intermolecular interaction in phenol clusters is slightly stronger than in water clusters. However, fusion of phenol and water clusters leads to stability that is akin to that of H(2)O clusters. The presence of hydrogen bond critical points (HBCP) and the values of rho(r(c)) and nabla(2)rho(r(c)) at the HBCPs provide an insight into the nature of closed shell interaction in hydrogen-bonded clusters. It is shown that the calculated values of total rho(r(c)) and nabla(2)rho(r(c)) of all the clusters vary linearly with the interaction energy.

Electrons↗
PubMed2004

Electrophilicity index as a possible descriptor of biological activity.

The purpose of this study is to probe the suitability of DFT based chemical reactivity parameter, electrophilicity index as a possible biological activity descriptor in the development of QSAR. Testosterone derivatives with activity described in terms of various biological activity parameters and the estrogen derivatives by relative binding affinity (RBA) values have been selected as model systems. The implications for the ability of electrophilicity to describe the biological activities are discussed. From the results it is possible to observe that electrophilicity index may be suitable to effectively describe the biological activity.

Animals↗
PubMed2004

Molecular dipoles at substrate/film interfaces influencing surface energy of Langmuir-Blodgett films.

Langmuir and Langmuir-Blodgett (LB) films of novel rigid Schiff base amphiphiles with different polar groups on aromatic rings have been studied at air/water interfaces and on solid substrates. The local surface potentials for the different substituents on the aromatic groups of the amphiphiles are correlated to the surface energy of LB films on solid substrates. Their contributions are probed on high-surface-energy (hsfe) quartz and hydrophobically modified low-surface-energy (lsfe) quartz. Using theoretical estimates, the long-range effects of the substituents of the polar groups on the alkyl chains have been studied from charge on the carbon and hydrogen atoms of the alkyl tails. The calculations indicate that a substituted carbon atom has a charge that is directly dependent on the nature of the atoms to which it is attached rather than on the charges of any other atoms of the substituents. This work shows that the polar substituents on the head group clearly influence the distal methylene groups of the tail. Thus, any treatment, either theoretical or experimental, of these films in contact with solid substrates should include the local relative permitivities of the polar moieties, which seem to play an important role in determining macroscopic properties such as surface energy.

Journal Article↗