文摘
The second-order non-linear (NLO) properties of the set of compounds iron (III)[N,N′-ethylenebis(salicylaldiminato) (pyridyl) (X), [Fe(SALEN)(pyridyl)X], where X = F−, Cl−, Br−, I, N−3, NCS− were examined. Complexes where X is a halide or thiocyanate exhibited weak SHG intensities (0.05-0.2 × urea). Considerable enhancement of SHG intensity was demonstrated by the azide complex (X = N−3), which has a powder SHG efficiency twice that of urea. Complexes of the form Fe(SALEN)(N3)(B), where B = 4-aminopyridine and 4-dimethylaminopyridine, did not demonstrate any second-order NLO properties. The X-ray crystal structure of 1 shows it crystallizes in the hexagonal space group P65 with a = 17.480(2), c = 12.513(3) Å and Z = 6. The iron is octahedrally coordinated with the SALEN ligand binding to the four equatorial sites. One of the axial sites is occupied by a nitrogen atom of the azide and the other site is coordinated to the pyridyl nitrogen. The non-linearity in this material originates from charge-transfer transitions in both the SALEN ligand and the pyridyl-Fe π-system.