Contribution of the transition moments, form of the absorption band, exciton, and the correlation effects in the linear and nonlinear optical properties of conjugated polymers

Linear and Nonlinear Optical Properties of Functional Groups for Conjugated Polymers. Analysis of the Acceptor–Donor Pair Substituents of Benzene: The Case of meta-Nitroaniline

“…We have also simulated the refraction index for five experimental data as seen in Table S-1 and Figure S-10 and the error was less than 3% and we consider that this result supports the hypothesis of weighing by the normalized oscillator strengths of the 1 B and ICT electronic transitions for χ (1) , β z , and χ (3) . On the other hand, we analyzed the shift of the derivative of the linear susceptibility χ (1) in the Brillouin zone as was done in ref . We found that both the real and imaginary parts of χ (1) for the 1 B transition change in a constant way throughout the Brillouin zone as seen in Figure for the left-rotatory current L1C5.…”

“…A larger difference of the intraband moments Ω 11 and Ω 55 produces a higher increment of χ (3) in the Brillouin zone. On the contrary, polyenes and polyenynes have equal intraband transitions moments and then the terms s 2 (interband) and s 4 (intraband) do not contribute to the generation of the NLO properties in those compounds.…”

“…It was necessary to iterate the value of Γ (damping of the optical transition) in order to obtain the correct values of ε. Then, it was possible to determine the value of the relaxation time τ R (computed from the phononic factor, η) of these transitions, normalizing with the experimental UV spectra as in ref . Thus, the values of η were 0.011 (231 nm) and 0.0105 (373 nm).…”

“…This increase of the conjugation produces a decrease of the band gap and then an enhancement of the values of the linear and NLO properties. In this way, it is convenient to analyze the spectroscopic properties of benzene, particularly the effect of the disubstituents on its optical properties with the methodology of Hückel–Agrawal’s approximation applied to a linear conjugated closed chain. − In principle, a special feature of benzene is the presence of ring currents, , that is, circular currents in the benzene, which induce a shift in the signal of NMR when a magnetic field is applied. Thus, the Brillouin zone extends from 0 to π in the reciprocal space because the electrons make a higher frequency circular movement around the ring.…”

“…Hückel–Agrawal’s approximation allowed us to obtain the energies, resonance energies β, and wavefunction coefficients. ,, The aim was to gain a physicochemical insight of the background of the NLO properties of m -NA, which is a question not answered directly, for instance, by ab initio methods . On the other hand, NAs have resonance zwitterionic structures with charge separation and, hence, an exciton arises and also correlation effects must be considered . In principle, it is known that the ICT effect is not present in m -NA via resonance as in o -NA and p -NA because the zwitterionic structures of the amine and nitro functionalities are not correlated in m -NA as seen in Schemes S-1 and S-2 of the Supporting Information.…”