Luminescent and magnetic bifunctional coordination complex based on a chiral tartaric acid derivative and europium.

A new mononuclear europium complex incorporating the (+)-di-p-toluoyl-D-tartaric acid (D-HDTTA) ligand, namely, catena-poly[tris{μ-3-carboxy-2,3-bis[(4-methylphenyl)carbonyloxy]propanoato}tris(methanol)europium(III)], [Eu(CHO)(CHOH)], (I), has been synthesized and characterized by IR spectroscopy, elemental analysis, powder X-ray diffraction and single-crystal X-ray diffraction analysis. The structure analysis indicates that complex (I) crystallizes in the trigonal space group R3 and exhibits an infinite one-dimensional chain structure, in which the Eu ion is surrounded by six O atoms from six D-HDTTA ligands and three O atoms from three coordinated methanol molecules, thus forming a tricapped trigonal prism geometry. The D-HDTTA ligand is partially deprotonated and adopts a μ-coordination mode via two carboxylate groups to link adjacent Eu ions, affording an infinite one-dimensional propeller-shaped coordination polymer chain along the c axis, with an Eu...Eu distance of 7.622 (1) Å. Moreover, C-H...π interactions lead to the formation of helical chains running along the c axis and the whole structure displays a snowflake pattern in the ab plane. The circular dichroism spectrum confirms the chirality of complex (I). The solid-state photoluminescence properties were also investigated at room temperature and (I) exhibits characteristic red emission bands derived from the Eu ion (CIE 0.63, 0.32), with a reasonably long lifetime of 0.394 ms, indicating effective energy transfer from the ligand to the metal centre. In addition, a magnetic investigation reveals single-ion magnetic behaviour. The spin-orbit coupling parameter (λ) between the ground and excited states is fitted to be 360 (2) cm through Zeeman perturbation. Therefore, complex (I) may be regarded as a chiral optical-magneto bifunctional material.