Organometallic complexes for nonlinear optics Part 21. Syntheses and quadratic hyperpolarizabilities of alkynyl complexes containing optically active1,2-bis(methylphenylphosphino)benzene ligands

The preparation of the chloro complex trans-[FeCl2{(R,R)-diph}(2)] (1) and the alkynyl complexes trans-[M(4-C=CC6H4R)Cl{(R,R)-diph}(2)] [M=Fe, R=NO2 ( 2); M=Ru, R=H (4) NO, (5), (E)-CH=CH-4-C6H4NO2 (6); M=Os, R=NO2 (7)], incor porating the optically active diphosphine 1,2-bis(methylphenylphosphino)ben zene (diph), are described. Oxidation potentials, as determined by cyclic v oltammetry, increase as 2 < 7 < 5. Molecular quadratic nonlinearities by hy per-Rayleigh scattering at 1064 nm increase upon introduction of an accepto r group (4 < 5), chain-lengthening of bridging group (5 < 6), and proceedin g from 3d to 4d and 5d metal (2 less than or equal to 5 less than or equal to 7). Two-level-corrected nonlinearities reproduce the first two trends, b ut metal variation follows the sequence 2 < 7 < 5. The experimental and two -level-corrected nonlinearities for 6 (2795 x 10(-30) and 406 x 10(-30) esu , respectively), are amongst the largest observed thus far for organometall ic complexes. Crystals of complexes 2 and 7 exhibit second-harmonic generat ion (assessed using the Kurtz powder technique), with an efficiency for the former of twice that of urea. (C) 2000 Elsevier Science S.A. All rights re served.