Dielectric-Driven Modulation of Electronic Structure, Optical Absorption, and Vibrational Force Constants in 2A3M5NP: A DFT and TD-DFT Investigation

Zainab Kalfah Mansi

doi:10.71229/r0sjc822

Authors

Zainab Kalfah Mansi Water Resources Management Engineering Department, College of Engineering, Al-Qasim Green University, Babylon 51013, Iraq https://orcid.org/0009-0008-3410-7435

DOI:

https://doi.org/10.71229/r0sjc822

Keywords:

Theoretical Physics, Density Functional Theory (DFT), Solvent Effects

Abstract

The given work offers a computational study of the effects of dielectric environment on the electronic structure, optical response, and the vibrational behavior of the push pull chromophore 2-amino-3-methyl-5-nitropyridine (2A3M5NP). As part of the IEFPCM method, DFT and TD-DFT calculations at the B3LYP/cc-pVTZ level were used to investigate solvent-dependent variations on the molecular potential energy surface. The frontier orbital distribution is a clear indication of intramolecular charge transfer (ICT) from the amino donor group to the nitro acceptor group with an increase in the solvent polarity increases the Homo-Lumo gap progressively narrows by nearly 6%. This decrease is coupled with a shift in the absorption peak of circa 5 percent in the red direction indicating reflecting stronger stabilization of the excited electronic state in the polar media. It is worth noting that the strong linear correlation that exists between the energy gap and the lambda max also confirms the electronic reorganization of the solvent. The response of the vibrational response also follows the same trend. The N–H stretching mode shows a slight yet measurable of a decrease in the force constant by approximately one-half a percent, leading to a redshift consistent with Hooke's model. Simultaneously, infrared intensity increases due to enhanced dipole moment derivatives on the normal coordinate. When collected, this provides an indication that the electronic and mechanical properties of 2A3M5NP are dielectrically sensitive, which is a physically coherent description of the solvent-selective molecular tuning.

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