Double-stranded metal-organic networks for one-dimensional mixed valence coordination polymers


The design of new types of metal-organic networks and the search for unusual crystal architecture represents an important task for modern inorganic and materials chemistry research. A group of new monosubstituted phenylcyanoximes, containing F, Cl, and Br atoms at the 2, 3, or 4 positions, were synthesized using the high yield nitrosation reaction with CH 3-ONO and were spectroscopically (1H NMR, 13C NMR, UV-visible, IR, mass spectrometry) and structurally characterized. Results of X-ray analysis revealed nonplanar trans-anti geometry for 2-chlorophenyl(oximino)acetonitrile, H(2Cl-PhCO); a nonplanar anti configuration for 4-chlorophenyl(oximino)-acetonitrile, H(4Cl-PhCO); and planar cis-syn geometry for 3-fluorophenyl(oximino)acetonitrile, H(3F-PhCO). All arylcyanoximes undergo deprotonation in solutions with the formation of colored anions exhibiting pronounced negative solvatochromism in a series of polar protic and aprotic solvents. Nine thallium(I) cyanoximates were obtained using the reaction between hot (∼95°C) aqueous solutions of TI2CO3 and solid powdery monohalogenated arylcyanoximes HL. Crystal structures of two TI(I) cyanoximates [TI(2Cl-PhCO) and TI(4Br-PhCO)] contained centrosymmetric dimeric units (TIL)2 that are connected to a coordination polymer by means of an oxygen atom of the oxime group of the neighboring molecule. Cyanoxime anions act as bridging ligands in both structures where the polymeric motif consists of double-stranded TI-O chains interconnected with the formation of zigzagging TI2O2 planar rhombes. Thallium atoms form infinite linear arrays with close intermetallic separations. The nearest TI(I)⋯ TI(I) distances are 3.838 and 4.058 Å in the TI(2Cl-PhCO) and TI(4Br-PhCO) structures, respectively, close to that in metallic thallium (3.456 Å). Monosubstituted phenyl groups are well aligned in π-stacking columns that are perpendicular to the array of TI(I) atoms and stabilize formed structures. Coordination polyhedrons of thallium(I) in these complexes represent distorted trigonal pyramids with stereoactive lone pair.


Chemistry and Biochemistry

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Inorganic Chemistry