A combined experimental and theoretical investigation of the excited-state dynamics of 2,4,6-trinitrotoluene (TNT) in DMSO solvent

Abstract

In the present contribution we carried out a TDDFT and femtosecond transient absorption study of the excited state dynamics of TNT in DMSO solvent. Vertical excitation and excited state relaxation were calculated at the SMD/M06-2X/TZVP level of theory. The electron absorption spectrum for the DMSO solvated TNT was calculated and compared with the experimental results. The results of the electronic excitation energies and the spin–orbital constants imply an intersystem crossing for the S₁–T₂ transition. The femtosecond time-resolved transient absorption measurements of the TNT in DMSO show the presence of two absorption signals around 650 nm and 540 nm, which are assigned to the population in the lowest singlet and triplet excited states, S₁ and T₁, respectively. The fast decay of the S₁ state population is assigned to an efficient S₁–T₂ intersystem crossing, which soon internally converts to the T₁ state. The slow decay of the T₁ population is attributed to the nonradiative transition to the S₀ state. The combined theoretical and experimental results present a mechanistic view of the photophysical dynamics of TNT in DMSO solution.