NONLINEAR AND POTENTIAL NONLINEAR-OPTICAL MATERIALS CONTAINING MOLYBDENUM OR TUNGSTEN MONONITROSYL REDOX CENTERS - STILBENE DERIVATIVES CONTAINING FERROCENYL, METHOXY OR DIMETHYLAMINO DONOR GROUPS

The compounds [M(NO){HB(dmpz)3}X(n){EC6H4(CH=CHC6H3-R,R')-4}2-n] (dmpz = 3,5-dimethylpyrazolyl,n = 1, E = NH, R = [(eta5-C5H4)Fe(eta5-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[CH=CHC6H4(NMe2-4)]-4}] shows that, although the compound crystallises in a polar space group, the lattice contains pseudo-centrosymmetrically 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.