The compound [CoCu(opba)(DMSO) 3 ] (1) [opba = orthophenylenebis(oxamato)] has been synthesized and characterized. Its crystal structure has been analyzed by X-ray diffraction techniques at 100 and 298 K. A structural phase-transition has been detected at around 150 K. An orthorhombic crystalline system is found at both temperatures, with very similar unit-cell dimensions. At room temperature 1 crystallizes in the Pnam space group (α-1 phase), with a = 7.6712(2), b = 14.8003(3), c = 21.0028(5) Å, and Z = 4, whereas at low temperature it crystallizes in the Pna2 1 space group (β-1 phase), with a = 7.3530(2), b = 14.5928(4), c = 21.0510(7) Å, and Z = 4. Both crystalline phases consist of linearly ordered bimetallic chains with the [Cu(opba)] 2-units tied by Co II ions to form a one-dimensional system. The DMSO molecules in α-1, which are coordinated to either Cu II or Co II , are disor-

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A new optical element that displays singular polarization eigenstates is proposed. It consists of a planar stratified structure composed of alternate gyrotropic and birefringent layers. The orthogonality of the polarization eigenstates is lost because of anisotropic reflections at the interfaces, which are enhanced by the special condition chosen for the multiple-beam interference. First we show that the anisotropic reflection at the interface between the layers with linear and circular symmetries does produce strong enough dichroism to break the orthogonality of polarization eigenstates. Second, we investigate the behavior of these eigenstates with respect to their linearity and orthogonality as a function of the width of the layers. Our results concretely demonstrate that it is possible to control the effective optical parameters of such stratified structures by adjusting the thickness of each anisotropic layer. Finally, we obtain the necessary conditions for designing a double-layer system with singular eigenstates of linear polarization.

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