Non-linear and potential non-linear optical materials containing molybdenum or tungsten mononitrosyl redox centres. Stilbene derivatives containing ferrocenyl, methoxy or dimethylamino donor groups

Abstract

The compounds [M(NO){HB(dmpz)₃}X_n{EC₆H₄(CHCHC₆H₃–R,R′)-4}_2–n](dmpz = 3,5-dimethylpyrazolyl, n= 1, E = NH, R =[(η⁵-C₅H₄)Fe(η⁵-C₅H₅)]-4, R′= H; E = O, R = R′= H; E = O or NH, R = 4-OMe, R′= H; R = 4-NMe₂, R′= H; E = NH, R = 2-OMe, R′= 4-OMe; R = 3-OMe, R′= 4-OMe; R = 2-OMe, R′= 5-OMe; M = Mo, X = Cl or I; M = W, X = Cl; n= 2; E = O, R = R′= H; E = O or NH, R = 4-OMe or -NMe₂, R′= H; E = NH, R = 2-OMe, R′= 4-OMe; R = 3-OMe, R′= 4-OMe, R = 2-OMe, R′= 5-OMe; M = Mo) have been synthesised and tested for second-order non-linear optical properties using the Kurtz powder test for second harmonic generation (SHG). The ferrocenyl derivatives have been found to exhibit SHG on irradiation at 1907 nm, whereas all of the derivatives containing NMe₂ or OMe groups are SHG inactive. The crystal structure of [Mo(NO){HB(dmpz)₃}Cl{OC₆H₄[CHCHC₆H₄(NMe₂-4)]-4}] shows that, although the compound crystallises in a polar space group, the lattice contains pseudocentrosymmetrically aligned pairs of molecules within each asymmetric unit. This indicates that the differences in second-order non-linear optical properties between the ferrocenyl and other derivatives may be attributed to structural rather than electronic effects.