Nonlinear Optical Response Properties of Aryl - Substituted Boron -Dipyrromethene Dyes: Unidirectional Charge Transfer coupled with Structural Tuning

TL;DR

This study uses quantum chemical methods to analyze the nonlinear optical properties of aryl-substituted BODIPY dyes, revealing how structural modifications influence their charge transfer and NLO response for potential technological uses.

Contribution

It provides a detailed quantum chemical analysis of NLO properties in aryl-substituted BODIPY dyes, highlighting the effects of structural tuning on charge transfer and hyperpolarizability.

Findings

Charge transfer is predominantly unidirectional in these dyes.

Structural modifications affect the NLO response significantly.

Hyperpolarizability aligns with the charge transfer direction.

Abstract

Controlling the nonlinear optical (NLO) response properties at the molecular level is a key to develop strong NLO active materials for technological applications. In this paper, we report quantum chemical investigation of NLO response properties of select aryl-substituted Boron-Dipyrromethene (BODIPY) dyes, a class of intramolecular charge transfer (ICT) probes. Density functional theory (DFT) with long-range corrected CAM-B3LYP functional and cc-pVTZ, 6-31G(d,p) and 6-31+G(d,p) basis sets are employed to compute the electronic structures and NLO response of the aforesaid molecules. Calculations at the second order M{\o}ller-Plesset perturbation (MP2) level of theory are performed for comparison. The results suggest that the charge transfer process in these molecules is mostly unidirectional and the total first hyperpolarizability (\b{eta}total) values of these molecules are dominantly dictated by the response in the direction of charge transfer. Alteration of conjugation strength through donor/acceptor substitution as well as twisting of the phenyl ring obtained through incorporation of methyl groups affect the NLO response of thesemolecules. The vector components of first hyperpolarizability (\b{eta}vec) of the probe molecules are also studied to analyze the angle between the vector components of \b{eta}vec and the dipole moment vector. The results presented here are expected to shed light on the origin of NLO response of several aryl-substituted BODIPY dyes and provide means to optimizing it for future technological applications.