Keto-enol tautomerism and nonlinear optical properties in β-diketones containing [2.2]paracyclophane

Nonlinear optical properties of [2.2]paracyclophane (pCp) derived β-diketones containing functional groups with different donor-acceptor properties, bounded to the dicarbonyl fragment, have been studied. Two polymorphic modifications, one of which is characterized by the polar space group Pca21 while the other one is centrosymmetric (space group Pbca) were obtained for β-diketone substituted by thiophene group depending on the crystal growth procedure. All molecules studied exhibit second harmonic generation ability, the efficiency of which was measured by the powder technique at 1064 nm fundamental wavelength. The NLO susceptibility for the compounds studied is analyzed taking into account the structural peculiarities and theoretical calculations.