# Structure–Property Correlations in Disubstituted 1,2,3-Triazoles: DFT Insights and Photophysical Analysis

## TL;DR

This paper explores how the structure of disubstituted 1,2,3-triazoles affects their electronic and photophysical properties using experiments and computational methods.

## Contribution

The study provides new insights into the structure–property relationships of disubstituted 1,2,3-triazoles through combined experimental and computational analysis.

## Key findings

- 1,2,3-triazoles show solvatochromic behavior in medium-polarity solvents.
- Photophysical properties of triazoles are modulated by pH via protonation/deprotonation.
- DFT and TD-DFT calculations confirm charge-transfer characteristics and electron density distribution.

## Abstract

The inherent structural
rigidity and modifiable electronic features
of disubstituted 1,2,3-triazoles are driving their recognition as
adaptable frameworks in photophysical and supramolecular chemistry.
The combination of structural integrity and tunable electronic characteristics
makes 1,2,3-triazoles highly functional for a wide range of applications,
from fluorescence-based sensors and drug design to organic electronics.
Owing to the versatile applications of triazoles in multiple domains,
this study integrates experimental and computational analysis of a
series of 1,4- and 1,5-disubstituted 1,2,3-triazole derivatives. To
elucidate the electronic architecture, photophysical characteristics,
and structure–property correlations, 1,2,3-triazoles with and
without a hydroxyaromatic framework have been investigated. Emphasis
has been given to the molecules’ solvatochromic behavior in
medium-polarity solvents. The photophysical behavior of the studied
1,2,3-triazole molecules is also modulated by pH, reflecting changes
via a protonation/deprotonation pathway specific to the individual
molecules. Systematic spectroscopic investigations revealed differential
absorption and emission responses across acidic to basic environments,
highlighting the sensitivity of triazole chromophores to proton-coupled
electronic interactions. Density Functional Theory (DFT) and Time-Dependent
DFT (TD-DFT) calculations at the B3LYP/6-311G­(d,p) level were employed
to investigate the frontier molecular orbitals (FMOs), electron density
distributions, and polarity of the studied molecules, with outcomes
corroborated by UV–vis and fluorescence spectroscopic measurements.
Additionally, Natural Bond Orbital (NBO) analysis is performed for
2-(4-phenyl-1-H-1,2,3-triazol-1-yl) phenol (PTP) and 5-anilino-4-phenyl-1H-1,2,3-triazole
(APT), representing hydroxyaromatic and nonhydroxyaromatic triazoles,
respectively. This analysis primarily focuses on establishing the
photophysical characteristics of the molecules as being of a charge-transfer
nature and their inherent electron density distribution. A comparative
analysis of experimental and computational data revealed a consistent
and complementary trend, reinforcing the reliability of the interpretations
drawn from both approaches.