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. 2023 Sep 28;127(38):7928-7936.
doi: 10.1021/acs.jpca.3c04288. Epub 2023 Sep 18.

Chromophore Planarity, -BH Bridge Effect, and Two-Photon Activity: Bi- and Ter-Phenyl Derivatives as a Case Study

Swati Singh Rajput  1 , Robert Zaleśny  2 , Md Mehboob Alam  1
Affiliations

Chromophore Planarity, -BH Bridge Effect, and Two-Photon Activity: Bi- and Ter-Phenyl Derivatives as a Case Study

Swati Singh Rajput et al. J Phys Chem A. .

Abstract

In this work, we have employed electronic structure theories to explore the effect of the planarity of the chromophore on the two-photon absorption properties of bi- and ter-phenyl systems. To that end, we have considered 11 bi- and 7 ter-phenyl-based chromophores presenting a donor-π-acceptor architecture. In some cases, the planarity has been enforced by bridging the rings at ortho-positions by -CH2 and/or -BH, -O, -S, and -NH moieties. The results presented herein demonstrate that in bi- and ter-phenyl systems, the planarity achieved via a -CH2 bridge increases the 2PA activity. However, the introduction of a bridge with the -BH moiety perturbs the electronic structure to a large extent, thus diminishing the two-photon transition strength to the lowest electronic excited state. As far as two-photon absorption activity is concerned, this work hints toward avoiding -BH bridge(s) to enforce planarity in bi- and ter-phenyl systems; however, one may use -CH2 bridge(s) to achieve the enhancement of the property in question. All of these conclusions have been supported by in-depth analyses based on generalized few-state models.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Molecules considered in this work.
Figure 2
Figure 2
Graphical representation of density difference between S1 and S0 states: turquoise implies electron-access zone and blue represents electron-deficient zone; dCT (numerical values given in Å unit) and R+/R– (represented by yellow and red dots, respectively). All these are computed at MN15/6-311+G(d,p) level. For the density difference plot isocontour value of 0.0004 au is taken.
Figure 3
Figure 3
Two-photon transition strength, calculated at response theory (response 2PA), two-state model (2SM) with first excited state respectively as an intermediate state.
Figure 4
Figure 4
Values of different δ0fjk terms involved in 2SM for all of the BP systems.
Figure 5
Figure 5
Values of different δ0fjk terms involved in 2SM for T5RO, T5RC-X, and T5RC-BH-X systems.
See this image and copyright information in PMC

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