Electronically Excited States in Poly(p‑phenylenevinylene): Vertical Excitations and Torsional Potentials from High-Level Ab Initio Calculations

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2013-03, Vol.117 (10), p.2181-2189
• Main Authors: Panda, Aditya N, Plasser, Felix, Aquino, Adelia J. A, Burghardt, Irene, Lischka, Hans
• Format: Article
• Language: English
• Subjects: Ab initio calculations; Applied sciences; Atomic and molecular physics; Calculations and mathematical techniques in atomic and molecular physics (excluding electron correlation calculations); Chains; Density; Dynamical systems; Dynamics; Electrical, magnetic and optical properties; Electronic structure of atoms, molecules and their ions: theory; Exact sciences and technology; Excitation; Mathematical analysis; Oligomers; Organic polymers; Phenyls; Physicochemistry of polymers; Physics; Properties and characterization
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp400372t

Ab initio second-order algebraic diagrammatic construction (ADC(2)) calculations using the resolution of the identity (RI) method have been performed on poly-(p-phenylenevinylene) (PPV) oligomers with chain lengths up to eight phenyl rings. Vertical excitation energies for the four lowest π–π* excitations and geometry relaxation effects for the lowest excited state (S1) are reported. Extrapolation to infinite chain length shows good agreement with analogous data derived from experiment. Analysis of the bond length alternation (BLA) based on the optimized S1 geometry provides conclusive evidence for the localization of the defect in the center of the oligomer chain. Torsional potentials have been computed for the four excited states investigated and the transition densities divided into fragment contributions have been used to identify excitonic interactions. The present investigation provides benchmark results, which can be used (i) as reference for lower level methods and (ii) give the possibility to parametrize an effective Frenkel exciton Hamiltonian for quantum dynamical simulations of ultrafast exciton transfer dynamics in PPV type systems.