Electronic‐Excited‐State Structures and Properties of Hydrated DNA Bases and Base Pairs

Abstract

Computational chemistry methods have been established as an attractive and reliable alternative to the costly and time-consuming experiments used to determine structures, properties and reactivities of molecular species. Although the modelling of the exact environmental conditions at the high theoretical level is still very expensive and may not be possible in several cases, computational methods are capable of providing reliable predictions in many ways, which can be useful to experimentalists and to the general scientific community [1,2]. Theoretical methods are especially attractive in areas such as the determination of excitedstate geometries of complex molecules, where experiments are not yet possible. Another example of the role of computational studies is the quantitative prediction of amino group pyramidalization of nucleic acid bases. The neutron diffraction study of adenine crystals has suggested a non-planar amino group [3]. Using the ab initio quantum chemical method, the amino groups of bases were suggested to be non-planar more than a decade ago [4,5]. However, only recently, an experimental method has verified such non-planarity in the gas phase of adenine and cytosine, using the measurement of the vibrational transition moment angles [6]. We strongly believe that theoretical and experimental methods are complementary to each other, and a judicious decision is needed for their efficient applications to determine the structures and properties of different systems.Hydrogen bonding is ubiquitous. It plays an important role in different aspects of all living organisms. Hydrogen bonds can be classified as weak, moderate and strong, depending upon their energies [7]. Hydrogen

CO2 and CH4 Sorption by [N4 4 4 4][NTf2] Ionic Liquid Using Quartz Crystal Microbalance Experiments under Different Pressures

“…It is reported that [N 4 4 4 4 ][NTf 2 ] has a melting point of 365−369 K, 45,46 determining its crystallized nature at room temperature, possibly due to the predominant Coulombic force between cation and anion. 47 [NTf 2 ] − anion was selected originally from an expectation of increasing CO 2 uptake because of the fluorinated methyl groups which have good affinity with CO 2 molecules by electrostatic forces. 48 Based on the amorphous cell module, a cell containing 30 ionic liquid molecules was built.…”

“…Considering the superiority of solid-state ionic liquids and avoidance of water influence, a hydrophobic and solid-state ionic liquid, [N 4 4 4 4 ]­[NTf 2 ] (MW = 522.61 g mol –1 ) with a symmetric cation (see Figure ), was used to trap CO 2 and CH 4 in a small scale. It is reported that [N 4 4 4 4 ]­[NTf 2 ] has a melting point of 365–369 K, , determining its crystallized nature at room temperature, possibly due to the predominant Coulombic force between cation and anion . [NTf 2 ] − anion was selected originally from an expectation of increasing CO 2 uptake because of the fluorinated methyl groups which have good affinity with CO 2 molecules by electrostatic forces .…”