Platinum Orthometalated Liquid Crystals Compared with Their Palladium Analogues. First Optical Storage Effect in an Organometallic Liquid Crystal

Di-μ-chlorobis(η 3 -2-methylallylplatinum) reacts with imines HL n = p- C n H 2 n +1 O−C 6 H 4 −CH N−C 6 H 4 −OC n H 2 n +1 - p ( n = 6, 1a; n = 2, 1b ) to yield the C,N-cyclometalated platinum(II) compounds [Pt 2 (μ-Cl) 2 (L n ) 2 ] ( 2a, 2b ). From 2, other types of dinuclear complexes [Pt 2 (μ-X) 2 (L n ) 2 ] with X = OAc, ( R )-2-chloropropionato, SC n H 2 n +1 ), mixed bridged complexes [Pt 2 (μ-X)(μ-Y)(L n ) 2 ] (X = Cl, OAc, ( R )-2-chloropropionato; Y = SC n H 2 n +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 (μ-X)(μ-Y)(L n ) 2 ] (X = ( R )-2-chloropropionato; Y = SC 16 H 33 ), 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.