Platinum orthometalated liquid crystals compared with their palladium analogues. First optical storage effect in an organometallic liquid crystal

Di-mu-chlorobis(eta(3)-2-methylallylplatinium) reacts with imines HL(n) = p-CnH2n+1O-C6H4CH=N-C6H4-OCnH2n+1-p (n = 6, 1a; n = 2, 1b) to yield the C,N-cyclometalated platinum(II) compounds [Pt-2(mu-Cl)(2)(L(n))(2)] (2a, 2b). From 2, other types of dinuclear complexes [Pt-2(mu-X)(2)(L(n))(2)] with X = OAc, (R)-2-chloropropionato, SCnH2n+1), mixed bridged complexes [Pt-2(mu-X)(mu-Y)(L(n))(2)] (X = Cl, OAc, (R)-2-chloropropionato; Y = SCnH2n+1), and mononuclear complexes [Pt(acac)(L(n))] have been prepared, and their mesogenic properties are compared with those of their palladium analogues reported previously. The Pt compounds exhibit higher temperature transitions, unless a different composition hides this effect when the material is a mixture of isomers. One of the compounds, cis-[Pt-2(mu-X)(mu-Y)(L(n))(2)] (X = (R)-2-chloropropionato; Y = SC16H33), forms a glasslike state on cooling from the cholesteric phase and shows absorption of light in the visible wavelength range. As a consequence, it is suitable for optooptical storage effects, which have been realized on the complex without the addition of dye.