Synthesis and crystal structure of a triple-decker Cu^II₃Tl^I₂ complex: first example of a thallium(I) system in the imino-phenolate Schiff base ligand family

<div><p>This report deals with the synthesis, characterization, and crystal structure of a heteropentanuclear Cu^II₃Tl^I₂ compound [(Cu^IIL)₃Tl^I₂](NO₃)₂ (<b>1</b>), where H₂L=<i>N</i>,<i>N</i>′-ethylenebis(3-ethoxysalicylaldimine). This compound crystallizes in the monoclinic crystal system within space group <i>C2</i>/<i>c</i>. Each of the two symmetry related thallium(I) centers is located between a terminal and a common, central [Cu^IIL] by forming bonds with four phenoxo and three ethoxy oxygens. The three [Cu^IIL] moieties are parallel and hence <b>1</b> is a triple-decker system. Neighboring triple-decker moieties are interlinked by π⋯π stacking interaction and weak hydrogen bonds to generate 3-D self-assembly in <b>1</b>. Salient features in the composition and structure of the title compound are discussed; the title compound is the first example of a thallium(I) system in imino-phenolate Schiff base family.</p></div

A Series of M^IICu^II₃ Stars (M = Mn, Ni, Cu, Zn) Exhibiting Unusual Magnetic Properties

The work in this report describes the syntheses, electrospray ionization mass spectromtery, structures, and experimental and density functional theoretical (DFT) magnetic properties of four tetrametallic stars of composition [M^II(Cu^IIL)₃]­(ClO₄)₂ (<b>1</b>, M = Mn; <b>2</b>, M = Ni; <b>3</b>, M = Cu; <b>4</b>, M = Zn) derived from a single-compartment Schiff base ligand, <i>N</i>,<i>N</i>′-bis­(salicylidene)-1,4-butanediamine (H₂L), which is the [2 + 1] condensation product of salicylaldehyde and 1,4-diaminobutane. The central metal ion (Mn^II, Ni^II, Cu^II, or Zn^II) is linked with two μ₂-phenoxo bridges of each of the three [Cu^IIL] moieties, and thus the central metal ion is encapsulated in between three [Cu^IIL] units. The title compounds are rare or sole examples of stars having these metal-ion combinations. In the cases of <b>1</b>, <b>3</b>, and <b>4</b>, the four metal ions form a centered isosceles triangle, while the four metal ions in <b>2</b> form a centered equilateral triangle. Both the variable-temperature magnetic susceptibility and variable-field magnetization (at 2–10 K) of <b>1</b>–<b>3</b> have been measured and simulated contemporaneously. While the Mn^IICu^II₃ compound <b>1</b> exhibits ferromagnetic interaction with <i>J</i> = 1.02 cm^–1, the Ni^IICu^II₃ compound <b>2</b> and Cu^IICu^II₃ compound <b>3</b> exhibit antiferromagnetic interaction with <i>J</i> = −3.53 and −35.5 cm^–1, respectively. Variable-temperature magnetic susceptibility data of the Zn^IICu^II₃ compound <b>4</b> indicate very weak antiferromagnetic interaction of −1.4 cm^–1, as expected. On the basis of known correlations, the magnetic properties of <b>1</b>–<b>3</b> are unusual; it seems that ferromagnetic interaction in <b>1</b> and weak/moderate antiferromagnetic interaction in <b>2</b> and <b>3</b> are possibly related to the distorted coordination environment of the peripheral copper­(II) centers (intermediate between square-planar and tetrahedral). DFT calculations have been done to elucidate the magnetic properties. The DFT-computed <i>J</i> values are quantitatively (for <b>1</b>) or qualitatively (for <b>2</b> and <b>3</b>) matched well with the experimental values. Spin densities and magnetic orbitals (natural bond orbitals) correspond well with the trend of observed/computed magnetic exchange interactions