Synthesis, Characterization, and Studies of Coordination-Polymeres With Isomeric Pyridylcyanoximes: Route to Metal Ribbons With Very Short Tl···Tl Separations

Abstract

Two isomeric pyridylcyanoximes, H(3PCO) and H(4PCO), containing nitrogen atoms of the heterocycle at 3-and 4-positions, respectively, were synthesized and thoroughly characterized using IR (including 15 N labeling), UV−visible, 1 H, 13 C one-and two-dimensional NMR spectroscopy, and X-ray analysis. The H(3PCO) exists as a mixture of syn-and anti-isomers in solutions, contrary to H(4PCO) which is present only as an antiisomer. Both compounds have planar geometry in the solid state and form elegant zigzag chains via H-bonding between the oxime group and the N-atom of the heterocycle. The H(3PCO) and H(4PCO) upon addition of a base form colored conjugated and solvatochromic anions in solutions. The reaction of the hot aqueous solution of Tl 2 CO 3 with solid isomeric pyridylcyanoximes leads to TlL, which were characterized by elemental analyses, IR spectroscopy, and X-ray analysis. Both complexes represent three-dimensional coordination polymers of different complexities where cyanoxime anions act as bridging ligands. Thallium(I) atoms in Tl(3PCO) and Tl(4PCO) form infinite, planar "metal ribbons" with unusually short intermetallic distances: 3.705 Å in Tl(3PCO) and 3.635 Å in Tl(4PCO) respectively, which are close to that in metallic thallium (3.465 Å). The latter compound has the second shortest Tl•••Tl thallophillic interaction reported in the literature thus far. Both yellow Tl(3PCO) and orange Tl(4PCO) are insulators at ambient conditions: R ∼ 1 × 10 11 Ohm.

New Route to Polynuclear Ni(II) and Cu(II) Complexes with Bridging Oxime Groups That Are Inaccessible by Conventional Preparations

“…It is reflected in the rising of the ν­(N–O) frequency and lowering of the ν­(CN) frequency, since the fragment attained more nitroso- character, as opposed to the oxime group (Table ). Similar changes have previously been observed in complexes of other cyanoximes. ,,− …”

1D Polymeric Platinum Cyanoximate: A Strategy toward Luminescence in the Near-Infrared Region beyond 1000 nm

“…Among ambidentate ligands, oximes used in this work take a special place because of their strong affinity for nickel triad metals that favor square-planar geometry. − On the basis of our previous studies, − we selected cyanoximes ,− as ligands for binding Pt II centers. Cyanoximes are particularly flexible mixed-donor ligands that allow modular design and are the platform of choice for developing metal complexes with controlled self-assembly in solutions and the solid state. − …”

The first bis-cyanoxime: synthesis and properties of a new versatile and accessible polydentate bifunctional building block for coordination and supramolecular chemistry

“…However, the presence of a heavy atom such as Tl (Z = 81), that is ∼13 times heavier than carbon (Z = 6), increases an order of magnitude residual electron density close to the metal. For example, values of residual electron density were observed to be 1.59 e Å −3 in Tl(I) nitrosodicyanomethanide, 41 2.66 e Å −3 in Tl(I) 3-pyridyl-cyanoxime, 42 3.62 e Å −3 in Tl(I) 4-pyridyl-cyanoxime, 42 and 3.95 e Å −3 in Tl(I) 2-benzthiazolylcyanxome. 24 Prior to the description of the crystal structure of the obtained Tl(I) complex 4, it is important to mention some reference distances 43 between the metal ion and N, O donor atoms of the ligands should be compared to the sum of ionic radii for Tl-O = 2.85 Å and Tl-N = 2.96 Å.…”