Halogen dipole moment effect of phenolic ring on formation of stair like polymers or polymers with tetranuclear cubic cage units; new precursors for preparation of TlCl and Tl2O3 nanostructures

Abstract

Structural determination of compounds [Tl₄(μ₃-2,4-dcp)₄] (1), [Tl₄(μ₃-3,4-dcp)₄] (2), [Tl(μ₃-2,5-dcp)] (3), [Tl(μ₃-2,4,6-tcp)] (4), [Tl₄(μ₃-2,4-bcp)₄] (5), [Tl₄(μ₃-2,4-cfp)₄] (6), [Tl₄(μ₃-4-cp)₄] (7), [Tl₄(μ₃-4-ip)₄] (8) and [Tl(μ₃-4-fp)] (9) (2,4-Hdcp = 2,4-dichlorophenol, 3,4-Hdcp = 3,4-dichlorophenol, 2,5-Hdcp = 2,5-dichlorophenol, 2,4,6-Htcp = trichlorophenol, 2,4-Hbcp = 2-bromo-4-chlorophenol, 2,4-Hcfp = 2-chloro-4-fluorophenol, 4-Hcp = 4-chlorophenol, 4-Hip = 4-iodophenol and 4-Hfp = 4-fluorophenol) by X-ray crystallography showed that we could divide these compounds to three groups upon the three types of primary structural units. These are group (I) with a distorted tetranuclear cubic cage unit, which could be observed in compounds 1, 2, 5, 6, 7 and 8, group (II) with a dimeric unit, which could be observed in compounds 3 and 4 and group (III) with a butterfly dimeric unit, which could be observed in compound 9. Replacement of other halo groups with a fluoro group on the phenolic ring results in completely different crystal packing of the attributed compound. This difference could be related to the unpredictable behavior of F. Comparison between the structure of compound [Tl(μ₃-4-fp)] (9) from group III and other compounds from groups of I and II indicates that the structure of compound 9 is intermediate of that observed in group I and group II compounds. In fact, the settlement of two butterfly dimeric units by the side of each other in a perpendicular form results in the formation of a distorted tetranuclear cubic cage unit. Structural comparisons of group II compounds with group I compounds shows that if the sum of the halogen substituent dipole moments on the phenolic ring eliminate each other to zero, a one-dimensional stair like coordination polymer will be formed and if these dipole moments do not eliminate each other to zero, a tetranuclear cubic cage unit will be formed. The thermal stability of these compounds was studied by thermogravimetric (TG) and differential thermal analyses (DTA). Nanostructures of thallium(I) chloride and thallium(III) oxide were prepared from a calcination process of the related compounds. These nanostructures were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM).