Synthesis, characterization, DFT, and TD-DFT studies of (E)-5-((4,6-dichloro-1,3,5-triazin-2-yl)amino)-4-hydroxy-3-(phenyldiazenyl)naphthalene-2,7-diylbis(hydrogen sulfite)

In this study, (E)-5-((4,6-dichloro-1,3,5-triazin-2-yl)amino)-4-hydroxy-3-(phenyldiazenyl)naphthalene-2,7-diylbis(hydrogen sulfite), a cyanurated H-acid (CHA) azo dye, was synthesized and characterized using FT-IR spectrophotometer and GC-MS spectroscopy. A density functional theory (DFT) based B3LYP and CAM-B3LYP method with 6-311 + G (d,p) basis set analysis was computed for HOMO-LUMO, natural bonding orbitals (NBO), UV-Vis absorptions and excitation interactions, in order to understand its molecular orbital excitation properties. A low Energy gap (Eg) of 2.947 eV was obtained from the molecular orbital analysis, which showed that HOMO to LUMO transition is highly feasible; hence CHA is adequate for diverse electronic and optic applications. Studies of the first five excitations (S-0 -> S-1/S-2/S-3/S-4/S-5) of CHA revealed that S-0 -> S-1 and S-0 -> S-3 are pi -> pi* type local excitations distributed around the -N=N- group; S-0 -> S-2, a Rydberg type local excitation; S-0 -> S-4, a highly localized pi -> pi* excitation; while S-0 -> S-5 is an n -> pi* charge transfer from a benzene ring to -N=N- group. From NBO analysis, we obtained the various donor-acceptor orbital interactions contributing to the stabilization of the studied compound. Most significantly, some strong hyper-conjugations (n -> n*) within fragments, and non-bondingand anti-bonding intermolecular (n -> n*/pi* and pi -> n*/pi*) interactions were observed to contribute appreciable energies. This study is valuable for understanding the molecular properties of the azo dyes compounds and for synthesizing new ones in the future.

Automated summary

In this study, a cyanurated H-acid (CHA) azo dye was synthesized and characterized, and its molecular orbital excitation properties were investigated using density functional theory and spectroscopic analysis. The low energy gap obtained from molecular orbital analysis indicates the feasibility of HOMO-LUMO transitions, making CHA suitable for electronic and optic applications. The study of excitations revealed different types of local and charge transfer interactions, contributing to the stabilization of the compound. This study is valuable for understanding the molecular properties of azo dyes and for the synthesis of new compounds in the future.