Non-bonded interactions in cyclobutane-thiones

Using UVPES and electronic spectral data the presence of an interaction between thd 1,3-thiocarbonyl groups in $\text{2}$ has been identified. EHT calculations also predict such an interaction. Presence of weak interaction between 1,3-carbonyl and thiocarbonyl groups in $\text{3}$ has been inferred from electronic absorption and emission spectra.