Syntheses, crystal structures, and optical properties of metal complexes with 4',5'-diaza-9'-(4′,5′-disubstituted-1,3-dithiol-2-ylidene)fluorene ligands

Four complexes with 4',5'-diaza-9'-[4,5-bis(methylthio)-1,3-dithiol-2-ylidene]fluorene (L-1) or 4',5'-diaza-9'-[4,5-bis(ethylthio)-1,3-dithiol-2-ylidene]fluorene (L 2) were synthesized. The complexes [Co(L-1)(2)Cl-2]center dot 2CH(3)OH (1), [Cu(L-2)(2)Cl-2]center dot CH3OH center dot 0.5CH(2)Cl(2) (3), and [Cu(L-2)(2)Br-2]center dot CH3OH (4) adopt a trans configuration and the compound [Cd(L-1)(2)(NO3)(2)] (2) is a cis structure. Short S center dot center dot center dot S, C center dot center dot center dot C, and C center dot center dot center dot S contacts were found to be important in the molecular packing. Both the solution and solid-state electronic spectra show a redshift in the intramolecular CT bands when forming metal complexes. This intramolecular charge transition in the solid state is enhanced relative to that in solution. Their third-order non-linear optical properties of compounds 1-4 were studied, and the results reveal that these complexes exhibit negative gamma values (about 10(-30)) and are self-defocusing samples. These gamma values are comparable to those of the known cluster compounds. The trans coordination of the two ligands to the metal center would. be beneficial to the NLO properties. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).