Triphenylamine-Based Fluorescent Styryl Dyes: DFT, TD-DFT and Non-Linear Optical Property Study

Abstract

The electronic structures and spectroscopic properties of triphenylamine-based monostyryl and bis(styryl) dyes were studied using quantum chemical methods. The ground-state geometries of these dyes were optimized using the density functional theory (DFT) method. The lowest singlet excited state was optimized using time-dependent density functional theory (TD-DFT). The absorption was also calculated using the ground-state geometries. All the calculations were carried out in the gas phase and in solvent. The results indicate that the absorption maxima calculated using the TD-DFT are in good agreement with those obtained experimentally. These dyes possess a large second-order non-linear property and this is mainly due to the strong donor-π-acceptor conjugation which is attributed to the excited state intramolecular charge transfer (ICT). There is a relationship between the hardness and first hyperpolarizability and second hyperpolarizability of mono- and bis(styryl) dyes. The efficiency of the intersystem crossing process can be improved by reducing the energy gap between the singlet and triplet excited states.

The Effect of TCNE and TCNQ Acceptor Units on Triphenylamine‐Naphthalenediimide Push‐Pull Chromophore Properties

“…The UV‐vis absorption spectra are depicted in Figure 2 and the respective data are tabulated in Table 1. The UV‐vis absorption spectra of TCBD bridged NDI‐TPA‐2 and NDI‐TPA‐3 exhibits a strong intramolecular charge transfer (ICT) absorption band at 388 nm (66100 M −1 cm −1 ), 486 nm (36700 M −1 cm −1 ) and 390 (50300 M −1 cm −1 ), 484 nm (57600 M −1 cm −1 ), which can be ascribed to the strong donor‐acceptor interaction resulting from the incorporation of the TCBD as an electron acceptor unit, which was also demonstrated in DFT calculations (Figure 1 and Figure S37, S38, S39) [31,32] . Interestingly, by increasing TCBD moiety from NDI‐TPA‐2 388 nm (66100 M −1 cm −1 ) to NDI‐TPA‐3 390 (50300 M −1 cm −1 ), the redshift of 2 nm was observed as compared to mono‐substituted compound.…”

Theoretical Investigation of Optical and Nonlinear Optical (NLO) Properties of 3‐Azabenzanthrone Analogues : DFT and TD‐DFT Approach.

“…Moreover, the NLO parameters of 1–12 were compared with that of urea (μ urea = 4.24 Debye, α urea = 6.23 X10 −24 e.s.u., β urea =0.371X10 −30 e.s.u., γ urea = 4.46 3X10 −36 e.s.u. ) which was found to be larger than that of urea, suggesting the high nonlinear optical properties in dyes 1–12 . Anisotropy of molecules 1–12 using GHs and RSHs functionals is given in Table S16‐S17 .…”

“…Higher the ICT, greater will be the values of NLO parameters. ICT depends on the simulated orientation of D and A cores, different substituents, and length of π‐electron delocalization …”

“…We have evaluated the performance of GH and RSH functionals with different basis sets, in calculating the NLO properties of 3‐Azabenzanthrone mediated D‐π‐A dyes. The previous reports from the literature suggest poor results of conventional global hybrid DFT functionals compared to range separated hybrid (RSH) functionals in the calculations of NLO properties . Various forms of exchange approximations vary with the interelectronic separation and improve the asymptotic behavior, are mixed in RSH functionals.…”

Exploration of Nonlinear Optical Enhancement and Interesting Optical Behavior with Pyrene Moiety as the Conjugated Donor and Efficient Modification in Acceptor Moieties

“…A smaller energy gap leads to promising NLO response. Thus, the FMO band gap can be used for qualitative estimation of the NLO behavior of the molecules [45]. The FMO band gap of reference HPPCR and designed compounds HPPC1-HPPC8 are tabulated in the Table 1.…”