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

Abstract

Di-μ-chlorobis(η3-2-methylallylplatinum) reacts with imines HLn = p-CnH2n+1O−C6H4−CHN−C6H4−OCnH2n+1-p (n = 6, 1a; n = 2, 1b) to yield the C,N-cyclometalated platinum(II) compounds [Pt2(μ-Cl)2(Ln)2] (2a, 2b). From 2, other types of dinuclear complexes [Pt2(μ-X)2(Ln)2] with X = OAc, (R)-2-chloropropionato, SCnH2n+1), mixed bridged complexes [Pt2(μ-X)(μ-Y)(Ln)2] (X = Cl, OAc, (R)-2-chloropropionato; Y = SCnH2n+1), and mononuclear complexes [Pt(acac)(Ln)] 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-[Pt2(μ-X)(μ-Y)(Ln)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.