Structural characterization of several cadmium halides with N-donor ligands

Crystal structures of the complexes containing macrocyclic cations [M(cyclam)]2+ (M = Ni, Zn) and tetra-iodido-cadmate(2-) anion

The asymmetric units of the isostructural compounds (1,4,8,11-tetra-aza-cyclo-tetra-decane-κ4 N)nickel(II) tetra-iodido-cadmate(II), [Ni(C10H24N4)][CdI4] (I), and tri-iodido-1κ3 I-μ-iodido-(1,4,8,11-tetra-aza-cyclo-tetra-decane-2κ4 N)cad-mium(II)zinc(II), [CdZnI4(C10H24N4)] (II) (C10H24N4 = 1,4,8,11-tetra-aza-cyclo-tetra-decane, cyclam, L), consist of the centrosymmetric macrocyclic cation [M(L)]2+ [M = NiII or ZnII] with the metal ion lying on a twofold screw axis, and the tetra-iodo-cadmate anion [CdI4]2- located on the mirror plane. In I, the anion acts as an uncoordinated counter-ion while in II it is bound to the ZnII atom via one of the iodide atoms, thus forming an electroneutral heterobimetallic complex [Zn(L)(CdI4)]. The NiII and ZnII ions are coordinated in a square-planar manner by the four secondary N atoms of the macrocyclic ligand L, which adopts the most energetically stable trans-III conformation. The [CdI4]2- anions in I and II are structurally very similar and represent slightly deformed tetra-hedrons with average Cd-I bond lengths and I-Cd-I angles of ca 2.79 Å and 109.6°, respectively. The supra-molecular organization of the complexes under consideration in the crystals is very similar and is determined by the hydrogen-bonding inter-actions between the secondary amino groups of the ligand L in the [M(L)]2+ cations and iodide atoms of the [CdI4]2- anion. In particular, the alternating cations and anions form chains running along the b-axis direction that are arranged into di-periodic sheets oriented parallel to the (101) and (01) planes. Because both kinds of sheets are built from the same cations and anions, this feature provides the three-dimensional coherence of the crystals of I and II.

One Luminescent Cadmium Iodide with Free Bifunctional Azole Sites as a Triple Sensor for Cu2+, Fe3+, and Cr2O72- Ions

The exploration of an excellent triple sensor for monitoring Cu²⁺, Fe³⁺, and Cr₂O₇^2- ions is of exceeding significance because of their serious effects on the human body. Herein, optically active 1H-3,5-bis(pyrazinyl)-1,2,4-triazole (Hbpt) with triazolyl and pyrazinyl groups was applied for the construction of a new type of organic hybrid cadmium iodide [Cd₆I₈(bpt)₄(H₂O)₄]·2H₂O (1) incorporating a hitherto-unknown [Cd₃I₄(H₂O)₂]²⁺ trimeric-cationic unit, which shows an orange light emission at 589 nm with a large Stokes shift of 246 nm. In virtue of the existence of free bifunctional azole sites as the receptors, 1 exhibits a highly selective and sensitive sensing property toward Cu²⁺, Fe³⁺, and Cr₂O₇^2- ions in aqueous solution with lower detection limits of 0.70∼4.46 ppm, which offers the sole example of cadmium iodide as an excellent triple sensor for detecting Cu²⁺, Fe³⁺, and Cr₂O₇^2- ions. Moreover, temperature-dependent luminescent determinations also reveal that 1 can be used as the potential luminescent molecular thermometer.

Coordination Affinity of Cu(II)-Based Silsesquioxanes toward N,N-Ligands and Associated Skeletal Rearrangements: Cage and Ionic Products Exhibiting a High Catalytic Activity in Oxidation Reactions

An unusual skeletal rearrangement of piperazine into ethylenediamine has been observed for the first time as a result of an attempt to synthesize a piperazine-linked metal-organic framework (MOF) using cage Cu(II),Na-phenylsilsequixane as a potential building block. Instead of the expected "metallasilsesquioxane-based MOF", a Cu₆ complex 1 coordinated both by silsesquioxane and ethylenediamine ligands was isolated. An effort to reproduce this result via direct interaction of Cu-phenylsilsequioxane and ethylenediamine surprisingly afforded two other types of complexes, copper-sodium 2 and copper 3 ionic products. Cationic components in both products 2 and 3 are represented by (i) copper and sodium ions (in the case of 2) or (ii) copper ions exclusively (in the case of 3) coordinated by ethylenediamine ligands. Both complexes 2 and 3 include Si₆-based condensed silsesquioxane fragments serving as anionic components of the products. Symptomatically, the types of the Si₆-frameworks in 2 and 3 are drastically different. More specifically, the Si₆ unit in 2 is an unprecedented distorted silsesquioxane skeleton consisting of two condensed tetramembered rings. Structural features of compounds 1-3 were established by single crystal X-ray diffraction. Compound 2 was found to catalyze the oxidation of cyclohexane to cyclohexanol and cyclohexanone with H₂O₂ (a mixture of these products was obtained after adding PPh₃ to the reaction solution) as well as the transformation of cyclohexanol to cyclohexanone under the action of tert-butyl hydroperoxide.

Bis[N-(2-hy-droxy-eth-yl)-N-iso-propyl-dithio-carbamato-κ(2) S,S'](piperazine-κN)cadmium: crystal structure and Hirshfeld surface analysis

The title compound, [Cd(C6H12NOS2)2(C4H10N2)], features a distorted square-pyramidal coordination geometry about the central Cd(II) atom. The di-thio-carbamate ligands are chelating, forming similar Cd-S bond lengths and define the approximate basal plane. One of the N atoms of the piperazine mol-ecule, which adopts a chair conformation, occupies the apical site. In the crystal, supra-molecular layers propagating in the ac plane are formed via hy-droxy-O-H⋯O(hy-droxy), hy-droxy-O-H⋯N(terminal-piperazine) and coordinated-piperazine-N-H⋯O(hy-droxy) hydrogen bonds; the layers also feature methine-C-H⋯S inter-actions and S⋯S [3.3714 (10) Å] short contacts. The layers stack along the b-axis direction with very weak terminal-piperazine-N-H⋯O(hy-droxy) inter-actions between them. An evaluation of the Hirshfeld surfaces confirms the importance of inter-molecular inter-actions involving oxygen and sulfur atoms.

catena-Poly[[(5,5'-dimethyl-2,2'-bi-pyridine-κN,N')cadmium(II)]-di-μ-iodido]

In the title coordination polymer, [CdI₂(C₁₂H₁₂N₂)]_n, the Cd²⁺ ion lies on a twofold rotation axis: it is six-coordinated in a distorted cis-CdN₂I₄ octa­hedral geometry by two N atoms from a chelating 5,5′-dimethyl-2,2′-bipyridine ligands and four bridging iodide anions. The bridging function of the iodide ions leads to a chain structure propagating in [001].