Three 5,5′-azotetrazolate-based cadmium(II) and zinc(II) complexes: syntheses, structures and photochromic and cell imaging properties

Abstract

Three 5,5′-azotetrazolate(AT)-based complexes, [Cd(pn)2(trans-AT)] (pn = 1,3-diaminopropane) (1), [Cd(en)2(trans-AT)]·4H2O (en = ethylenediamine) (2), and {[Zn(en)2(trans-AT)0.5](trans-AT)0.5} (3), have been synthesized and characterized by single-crystal X-ray diffraction analysis. Complexes 1–3 show three different supramolecular structures, in which the trans-AT2− have three different bridging modes. Complex 1 shows a 1-D zigzag chain structure formed by each μ 2-trans-AT2− bridging two Cd2+ ions. In 2, the trans-AT2− anions are μ 2 bridging, linking Cd2+ ions to give another 1-D zigzag chain, which forms a 2-D supramolecular network by intermolecular hydrogen bonds. In 3, [Zn(en)2(trans-AT)0.5]+ forms a 2-D network structure with each μ 4 bridging trans-AT2− linking four different Zn2+ ions. The [Zn(en)2(trans-AT)0.5]+ and uncoordinated trans-AT2− are further connected through face-to-face π–π stacking and electrostatic interactions, rendering a 3-D supramolecular network. The photochromism of aqueous solutions of 1–3 and [Na2(trans-AT)(H2O)5] (L) and the photoluminescence in solid samples of 2 and 3 as well as onion cell imaging with 2–3 and L as labels have been studied and reported.