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 CH3−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 Tl2CO3 and solid powdery monohalogenated
arylcyanoximes HL. Crystal structures of two Tl(I) cyanoximates [Tl(2Cl−PhCO) and Tl(4Br−PhCO)] contained
centrosymmetric dimeric units (TlL)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 Tl−O chains interconnected with the formation of zigzagging Tl2O2
planar rhombes. Thallium atoms form infinite linear arrays with close intermetallic separations. The nearest Tl(I)···Tl(I) distances are 3.838 and 4.058 Å in the Tl(2Cl−PhCO) and Tl(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 Tl(I) atoms and stabilize formed structures. Coordination polyhedrons of thallium(I) in
these complexes represent distorted trigonal pyramids with stereoactive lone pair.