Quantum Chemical Investigations on Acetylenic Carbon Rich Compounds as Molecular Construction Kit

Abstract

Ground and excited state behaviors of Radialenes, Expanded Radialenes and TEE monomer and dimer derivatives, which are carbon rich compounds were investigated by using quantum chemical calculations. Most of these advanced materials have non-linear optical properties and they can be used as molecular electronics. AM1 and DFT/B3LYP with 3-21G and 6-31G* basis sets methods were used for the ground state calculations of radialenes, expanded radialenes and TEE monomers and dimers. TDDFT/3-21G, TDDFT/6-31G* level of calculations were carried out for the excited state behaviors on AM1, DFT/3-21G* and DFT/6-31G* ground state structures. All the methods that we have used gave similar results with a very small discrepansies. Radialenes and expanded radialenes have planar ground state structures except the one with size 6; the three dimensional chair like geometry is slightly stable than the planar one. There is no effect of the size of radialenes on the the geometrical parameters. The introduction of ethynyls instead of hydrogens causes a red-shift about 100-150 nm. The maximum absorption wavelength usually increases with the size of radialenes with some exceptions for the planar structures. The effect of various acceptors such that p-NO2-benzene- , p-CH3-benzene-, p-CHO-benzene- and their locations which are mainly CIS, TRANS and GEMINAL with respect to donor positions to the TICT state on push-pull TEE derivatives were investigated by using excited state calculations. The probable donor units on the TEE derivates were considered as dimethyl amine and dimethyl aniline units. TICT property for the rotation of dimethylaniline group is observed for many of isomers. TICT state appeared both for cis and trans conformer of the donor substituted TEE dimer.