Charge transfer complexes of 4-isopropyl-2-benzyl-1,2,5-thiadiazolidin-3-one1,1-dioxide with DDQ and TCNE: experimental and DFT studies

Abstract

The charge transfer complexes of the donor 4-isopropyl-2-benzyl-1,2,5-thiadiazolidin-3-one1,1-dioxide (SF) with π acceptors 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and tetracyanoethylene (TCNE) have been studied spectrophotometrically in chloroform and methanol at room temperature. The results indicated the formation of CT-complexes with a molar ratio of 1 : 1 between donor and each acceptor. The physical parameters of the CT-complexes were evaluated using the Benesi–Hildebrand equation. The data were analyzed in terms of their stability constant (K), molar extinction coefficient (ε_CT), thermodynamic standard reaction quantities (ΔG⁰, ΔH⁰, ΔS⁰), oscillator strength (f), transition dipole moment (μ_EN) and ionization potential (I_D). The experimental studies were complemented by quantum chemical calculations by the time-dependent density functional theory (TD-DFT) at the B3LYP level. The theoretical UV visible and FT-IR spectra were compared with those obtained experimentally. The first order hyperpolarizability (β₀) and related properties (α₀ and Δα) are calculated using the B3LYP method on the finite-field approach. The Mulliken charges, MEP calculations, the electronic properties, HOMO and LUMO energies and NBO analysis were performed on an optimized charge transfer complex of SF-DDQ.