DFT study on mono-chloroazulenes

The active layer in organic photovoltaic bulk heterojunction devices is composed of a blend of π-conjugated, electron-donor polymers and electron-acceptor molecules [1].Whereas the optoelectronic properties of the electron-donor polymer are primarily determined by the choice of the conjugated backbone, the solubility is predominantlydetermined by the position, length and makeup of the alkyl side chains. Both the polymer backbone and the alkyl side chains inchlence device efficiency and molecular packing structure, especially in donor–acceptor copolymers, which contain an ordered sequence of different subunits [2]. The objective of the present research is to study the electrical and structural properties of all mono-chloroazulenes. All of the possible of mono-chloroazulenes studied in this work are presented in Fig. 1.Structures of representative mono-chloroazulenes were optimized using B3LYP/6- 311+G* levels of theory with the GAUSSIAN 09 package of programs implemented on a Pentium–PC computer with a 7300 MHz processor. The vibrational analysis showed that all structures correspond to local minima in potential energy surface. Values of dipole moment has been calculated and analyzed. The analysis of these data showed that the 2-chloroazulene has the highest value of the dipole moment (with 2.9837 Debye), and it can be suggested that this molecule has high solubility in polar solvents. The electrochemical stability of 2-chloroazulene is greater than other compounds and also the zero-point energy for this molecule is greater than other molecules. The analysis of data showed that the double bonds in 4-chloroazulene is more delocalized; accordingly, this monomer is the best candidate monomer among all mono-chloroazulenes for the synthesis of corresponding conductive polymers with modified characteristics