Optical limiting properties, structure and simplified TD-DFT calculations of scandium tetra-15-crown-5 phthalocyaninates

The optical limiting properties of crown-ether-substituted scandium(III) phthalocyaninate complexes, bis-tetra-15-crown-5-phthalocyaninates Sc[(15C5)(4)Pc](2)(center dot 0) (I) and Sc[(15C5)(4)Pc](2)(- )(Ia), together with monophthalocyaninate [(15C5)(4)Pc]Sc(OAc) (II) were measured by using the Z-scan technique (532 nm laser and pulse rate of 10 ns). It was revealed that expansion of the pi-system on moving from the monomeric Sc complex II to sandwich compound I and changing the electronic state of the sandwich compound from the anionic Ia species to the neutral radical I improves the optical limiting properties. The Im[chi((3))] values obtained lie in the 10(-12)-10(-10) esu range that is consistent with those reported previously for other organic chromophores. The crystal structure of sandwich Sc(III) complex I was elucidated by means of single-crystal X-ray diffraction analysis and was used to guide a series of theoretical calculations. It was demonstrated that the application of simplified time-dependent density functional theory (sTD-DFT) calculations can provide reasonably accurate predictions for compounds of this type when the geometries of the complexes are clearly defined.