Computational Insights into Functionalized Calcein Derivatives (D1–D5) for Enhanced Nonlinear Optical Response: A DFT-Based Study

Abstract

Optimization of organic chromophores with higher nonlinear optical (NLO) properties is at the heart of recent optoelectronics, photonics, and data storage. Calcein, being a xanthene-derived fluorescent dye, presents a robust platform for structural tuning towards increased Nonlinear optical response. In the present research, we computationally investigate a series of hypothetical Calcein functional derivatives (D1–D5), with electron-donating and electron-withdrawing substituents. The Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) models were used to geometrical optimize, determine frontier orbital distributions, calculate dipole moments, predict UV-Vis absorption spectra, and estimate first-order hyperpolarizability (β). Results show that the functionalization has substantial impacts on intramolecular charge transfer (ICT), resulting in increased NLO responses over parent Calcein. Amongst the derivatives, Amino-Calcein (D1) and Nitro-Calcein (D2) registered the maximum β values, indicating their strong potential as future-generation NLO chromophores. In this work, Calcein derivatives have been brought into focus as lead contenders for experimental synthesis and future use in cutting-edge photonic materials.