Theoretical Study of Optical and Electronic Properties of Unsymmetrical Dendritic Molecules with Different Bridge Moieties

Abstract

Molecules bearing polyphenylphenyl dendrons show great potential for applications in organic light-emitting diodes. In this paper, quantum-chemical calculations have been applied to investigate the structural and electronic properties of typical molecules bearing polyphenylphenyl dendrons, 2-(2′,3′,4′,5′-tetraphenyl)phenyl-5-(p-N,N-dimethyl)phenyl pyridine (A), 1-(2′,3′,4′,5′-tetraphenyl)phenyl-4-(p-N,N-dimethyl)phenyl benzene (B), 2-(2′,3′,4′,5′-tetraphenyl)phenyl-5-(p-N,N-dimethyl)phenyl thiophene (C), 1-(2′,3′,4′,5′-tetraphenyl)phenyl-2,5-dimethoxy-4-(p-N,N-dimethyl)phenyl benzene (D), and 2-(2′,3′,4′,5′-tetraphenyl)phenyl-5-(p-N,N-dimethyl)phenyl furan (E). The geometrical and electronic structures in the ground state and lowest singlet excited states have been optimized by B3LYP/6-31G(d) and TD-B3LYP/6-31G(d) methods, respectively. The important parameters, including ionization potential (IP), electron affinity, the reorganization energies (λ), hole extraction potential, and electron extraction potential, first lowest singlet excitation energies, maximum absorption and emission wavelengths are also systematically investigated. The result implied that the HOMO, energy gaps, and IP are affected by the central aromatic ring in the order of phenylene>pyrryl> 2,5-dimethoxyphenylene>thienyl>furyl. The solvent effects on absorption and emission spectra were further examined using the polarizable continuum model.