Second-harmonic generation properties of some co-ordination compounds based on pentanedionato ligands

Abstract

The synthesis and non-linear optical properties of pentanedionato ligands and their complexes with BF₂⁺, rhodium(I) and palladium(II) are described. 4-Nitrobenzoylacetone 1, 3-(2,4-dinitrophenyl)pentane-2,4-dione 3, and the BF₂⁺ adduct difluoro(4-methoxybenzoylacetonato)boron 2, were used to synthesize a range of palladium(II) and rhodium(I) complexes. The single-crystal X-ray structures of bis(triphenylphosphine)(4-nitrobenzoylacetona-to)palladium(II) tetrafluoroborate 4, and bis(triphenylphosphine)[3-(2,4-dinitrophenyl)-pentane-2,4-dionato]palladium(II) tetrafluoroborate 5, were determined. 4 and 5 crystallize in the triclinic space group P, with two molecular units per unit cell with dimensions of a= 10.995(1)Å, b= 13.692(3)Å, c= 14.964(4)Å, α= 102.933(20)°, β= 92.286(16)°, γ= 98.466(14)° for 4, and a= 12.066(2)Å, b= 12.112(2)Å, c= 15.681(2)Å, α= 103.840(12)°, β= 91.227(12)°, γ= 99.596(14)° for 5. Both 4 and 5 have the pentanedionato oxygens directly bonded to the square planar Pd^II atom, with Pd—O bond lengths of 2.034(5) and 2.046(5)Å for 4 and 2.019(2) and 2.033(2)Å for 5. The phenyl ring in 4 is planar with the pentanedionato ring, but in 5 the phenyl group is perpendicular to the pentanedionato ring. The second-harmonic generation (SHG) properties of the compounds were measured and compared with those for urea.