Photochemistry of Dithiocarbamate Cu(S₂CNEt₂)₂ Complex in CHCl₃. Transient Species and TD-DFT Calculations

Nanosecond laser flash photolysis was used to study the mechanism of photochemical transformations of the diethyldithiocarbamate Cu­(II) complex (Cu­(dtc)₂, where dtc^– ≡ ^–S₂CNEt₂ anion) in chloroform solutions. The electron transfer from the excited Cu­(dtc)₂ complex to a solvent molecule leads to the appearance of the primary intermediate, the [ClCu­(dtc)­(dtcCHCl₂)] complex, where a dtcCHCl₂ molecule is coordinated with a copper ion via one sulfur atom. In the fast reaction (<i>k</i> = 2.1 × 10⁹ M^–1 s^–1) with Cu­(dtc)₂, this complex forms a long-lived dimer [ClCu­(dtc)­(dtcCHCl₂)­Cu­(dtc)₂]. This intermediate decays during several seconds (<i>k</i> = 5.6 × 10^–2 s^–1) into the final product, i.e., a diamagnetic dimer [ClCu­(dtc)­Cu­(dtc)₂]. To determine the structure of intermediate complexes the quantum chemical calculations were carried out using DFT, TD-DFT, and PCM (Polarizable Continuum Model) methods