Photoinduced processes of tetrahexylammonium tetrachlorocuprate [(C₆H₁₃)₄N]₂Cu^IICl₄ in chloro-organic solvents were investigated by steady state photolysis and femtosecond transient absorption spectroscopy, as well as TD-DFT calculations of excited terms.

The product composition and the principles of photochemical transformations of tetrahexylammonium tetrachlorocuprate [(RH)₄N⁺]₂[Cu^IICl₄]²⁻ (RH = C₆H₁₃) in 2-chlorobutane at 77 K have been found out by ESR spectroscopy. It has been shown that the photolysis of [(RH)₄N⁺]₂ [Cu^IICl₄]²⁻ results in the formation of alkyl radicals (R^⊙), presumably, anions [Cu^ICl₃]²⁻ and organic copper(II) compounds {Cu^IIR}. A reduction in the quantum yield of primary photolysis products during the reaction, nonequivalence of the quantum yield of the buildup of paramagnetic photolysis products to that of [Cu^IICl₄]²⁻ consumption, and a decrease in the total number of paramagnetic particles in the system during the photolysis have been revealed. A photolysis mechanism involving both photochemical and thermal processes is proposed.

Coil to globule transition in poly(N-isopropylacrylamide) aqueous solutions was studied using spin probe continuous-wave electronic paramagnetic resonance (CW EPR) spectroscopy with an amphiphilic TEMPO radical as a guest molecule. Using Cu(II) ions as the “quencher” for fast-moving radicals in the liquid phase allowed obtaining the individual spectra of TEMPO radicals in polymer globule and observing inhomogeneities in solutions before globule collapsing. EPR spectra simulations confirm the formation of molten globules at the first step with further collapsing and water molecules coming out of the globule, making it denser.

Coil-to-globule transition and dynamics of inhomogeneities in aqueous solutions of graft copolymers of NIPAM with different content of oligolactide groups were studied using spin probe continuous wave EPR spectroscopy. The technique of the suppressing of TEMPO as spin probe by spin exchange with Cu²⁺ ions was applied. This approach allowed us to detect individual EPR spectra of the probe in collapsed globules and estimate its magnetic and dynamic parameters reliably. The formation of inhomogeneities at temperatures lower than the volume phase transition temperature measured via transmission, and differential scanning calorimetry was fixed. An increase in oligolactide content in copolymers leads to the formation of looser globules, allowing for the exchange of the probe molecules between the globules and the external solution.

Electron paramagnetic resonance spectroscopy in the framework of the spin probe technique is applied to estimate the effect of the structure of molecules as an example of nitroxyl radicals on their localization in aqueous solutions of thermoresponsive poly-N-isopropylacrylamide during the coil-to-globule phase transition. It is shown that the small hydrophobic 4-hydroxybenzoate-TEMPO probe is almost completely localized in the globule formed during the phase transition, while the large probe containing a long alkyl tail (methyl 5-doxyl stearate) does not enter the compact polymer globule.