First-Order Hyperpolarizability of Triphenylamine Derivatives Containing Cyanopyridine: Molecular Branching Effect

Abstract

In the present work, we report the multibranching effect on the dynamic first-order hyperpolarizability (β(−2ω; ω, ω)) of triphenylamine derivatives containing cyanopyridine onebranch (dipolar structure), two-branch (V-shaped structure), and three-branch (octupolar structure) structures. For this study, we used the hyper-Rayleigh scattering (HRS) technique involving picosecond pulse trains at 1064 nm. Our results show that β HRS increases from 2.02 × 10 −28 to 9.24 × 10 −28 cm 5 /esu when an extra branch is added to the molecule, configuring a change from a dipolar to a V-shaped (quadrupolar) molecular structure. When a third branch is added, leading to an octupolar structure, a decrease to 3.21 × 10 −28 cm 5 /esu is observed. Such a significant decrease in β HRS is attributed to a negative contribution presented in the β HRS description by using a three-level energy approach due to their electronic structure and considering a specific combination of the angle between the dipole moments. On the other hand, the enhancement of β HRS found for the quadrupolar structure is associated with the cooperative enhancement due to the electronic coupling between the branches that increases considerably the transition dipole moment and permanent dipole moment change. To explain the β HRS results obtained for different molecules, we employed the HRS figure of merit, FOM HRS = β HRS /N eff 3/2 , in which N eff is the effective number of π-conjugated bonds, and the few-energy level approach for β HRS within the Frenkel exciton model. To shed more light on the experimental results interpretation, we performed time-dependent density functional theory calculations combined with a polarizable continuum model to confirm the energy and oscillator strength of the electronic transitions assumed in the Frenkel exciton model employed here.

Structural parameter-modulated nonlinear optical amplitude of acceptor–π–D–π–donor-configured pyrene derivatives: a DFT approach

“…35 It also helps us to deduce the reactive sites in any p-electron systems. 17,36,37 The FMOs energy gap (E gap ¼ E LUMO À E HOMO ) elucidates the electron transference properties, reactivity, hardness and soness of the molecule. 38 The higher value of E gap for molecules indicates more stability, less chemical affinity and greater hardness value, which means that they may cause a change in the electronic arrangement.…”

“…The pyrene structure has a solid p-electron delocalization and uorescent property because of its planar aromatic features. Its solid structure is based upon the two-dimensional geometry having a strong tendency toward p assembly, and the great variation in functional groups onto graphite, fullerenes 15,16 and graphene 17,18 make it attractive towards NLO applications. 19 We have designed an appropriate donor-p-spacer-acceptor of pyrene-based molecules containing an acceptor (cyano vinyl ester) allied to pyrene centered by thienyl or phenyl conjugating linkers.…”

First principles study of electronic and nonlinear optical properties of A–D–π–A and D–A–D–π–A configured compounds containing novel quinoline–carbazole derivatives

“…[6][7][8] Therefore, different attempts are being made to model various materials which show NLO properties, such as natural and fabricated nanomaterials, organic and inorganic semiconductors, polymer frameworks and molecular dyes. [9][10][11][12][13] Organic NLO materials can offer low production costs, low dielectric constants, high photoelectric coefficients and design exibility. Usually, macroscopic NLO material properties originate from the hyperpolarizability of the NLO chromophore.…”

Photophysical and Protonation Time Resolved Studies of Donor–Acceptor Branched Systems With Pyridine Acceptors

“…The branched molecules either of quadrupolar or octupolar geometry bear an electron donating or accepting core such as triphenylamine (TPA), 4,5,6,[16][17][18][19][20][21] triazine, 5,9,22,23 truxene [24][25][26][27] etc. Especially,…”