Syntheses, crystal structures and coordination compounds of some 2-hetarylcyanoximes

2-hetarylcyanoximes which have the general formula HO–NC(CN)–R, where R is a heterocyclic group such as 2-pyridyl, 2-quinolyl, 2-benzthiazolyl etc., have been found to be good multidentate ligands for coordination chemistry. They form intensely colored complexes with iron(II) and bis-compounds with copper(I), which are used in analytical chemistry. Stability constants for anionic Fe2+ tris-cyanoximates were determined. The detailed syntheses and crystal structures of 2-pyridilcyanoxime (HPCO), 2-quinolylcyanoxime (HQCO) and 2-thiazolylcyanoxime (HTLCO) are reported. Molecules of HPCO in the crystal state adopt a non-planar cis–anti conformation. HQCO crystallizes as a monohydrate and this cyanoxime has a trans–anti non-planar conformation in the solid state. Molecules of HTLCO showed a trans–syn planar conformation in the solid state. Crystal structures of other known cyanoxime ligands are reviewed, as well as syntheses and the coordination modes for 2-hetarylcyanoximes in various complexes with s-, p- and d-metals

Efficient hexane isomers separation in isoreticular bipyrazolate metal-organic frameworks: The role of pore functionalization

Hydrocarbons separation in petrochemical industries is a key, energy-consuming stage in the manufacture of high-quality added-value products\u2014hence the need for more efficient materials and environmentally friendly methodologies to improve this process. In this context, we have studied the effect of metal-organic frameworks (MOFs) pore functionalization in hexane isomers separation, isolating the robust isoreticular zinc(II) bipyrazolates Zn(BPZ), showing no pore decoration, Zn(Me2BPZ), the pores of which are decorated with apolar methyl groups, and Zn(BPZ(NH2)2), the spacers of which possess polar Lewis-basic functions (H2BPZ = 1H,1\u2032H-4,4\u2032-bipyrazole; H2Me2BPZ = 3,3\u2032-dimethyl-1H,1\u2032H-4,4\u2032-bipyrazole; H2BPZ(NH2)2 = 3,5-diamino-1\u2032H,1\u2032H-4,4\u2032-bipyrazole; DMF = dimethylformamide). After characterizing Zn(BPZ(NH2)2) as per its crystal structure and thermal behaviour, and all the three MOFs as per their textural properties, we investigated, from the experimental and computational points of view, the impact of the square one-dimensional channels decoration on the separation of the hexane isomers, demonstrating the relevance of pore constrictions in the resolution of the title alkanes mixture.[Figure not available: see fulltext.]

Coordination polymers of d- and f-elements with (1,4-phenylene)dithiazole dicarboxylic acid

The new ditopic ligand [2,2\u2032-(1,4-phenylene)bithiazole]-5,5\u2032-dicarboxylic acid (H2TzPhTz) was synthesized in 3c 70% yield through a classical Hantzsch synthesis. Isolation of the dimethyl ester intermediate Me2TzPhTz as the trifluoroacetic acid adduct Me2TzPhTz\ub72CF3CO2H allowed its crystal structure determination, revealing that the constituting molecules are interconnected through an extended hydrogen-bond network. Reaction of H2TzPhTz with suitable ZnII and UVI salts yielded the 1-D coordination polymers [Zn(TzPhTz)(H2O)2] (Zn_TzPhTz) and [UO2(TzPhTz)(DMF)]\ub7DMF (U_TzPhTz). The former is characterized by zig-zag chains with cis-{Zn(OCOO)4(OH2O)2} nodes and \u3bc-\u3b72:\u3b72-TzPhTz2- spacers, while in the latter TzPhTz-bridged {UO2(TzPhTz)(DMF)}2 dimeric units form polymeric strands. In the solid state, both H2TzPhTz and Zn_TzPhTz emit in the blue-green visible region (\u3bbem = 474 and 477 nm, respectively). The two coordination polymers witness the versatility of H2TzPhTz as a linker toward d and f metal ions, and they should be considered as the preliminary step toward the preparation of TzPhTz-based metal\u2013organic frameworks for practical applications in the field of luminescence sensing