Synthesis and Characterization of N,N',N'',N'''-Tetrasalicylidene-3,3'-diaminobenzidine Schiff-Base Coordination Polyelectrolytes of Yttrium(III), Lanthanum(III), Gadolinium(III), and Ytterbium(III)

Abstract

A series of linear coordination polyelectrolytes formed by lanthanide(III) ions (Ln{sup 3+} = La{sup 3+}, Gd{sup 3+}, Y{sup 3+}, or Yb{sup 3+}) with the anion of the Schiff-base N,N{prime},N{double_prime}{prime}-tetrasalicylidene-3,3{prime}-diaminobenzidine (H{sub 4}tsdb) have been synthesized. This new series has the formula [MLn(tsdb)]{sub n} (M{sup +} = an alkali metal ion). Some can dissolve in polar organic solvents with high dielectric constants, such as DMSO, NMP, and DMF, and they exhibit the typical properties of polyelectrolytes, i.e., an apparent increase in inherent viscosity for dilutes solutions; the formation of colloidal precipitates when water is added to the solutions; smaller solution conductivity relative to simple electrolytes; high thermal stability (>773 K); and high glass transition temperature. Molecular weights of [NaY(tsdb)]{sub n} have been estimated by NMR end-group analysis to be as high as 18,500. The Mark-Houwink constants for [NaY(tsdb)]{sub n} are a = 0.510 and K = 8.12 {times} 10{sup {minus}2} cm{sup 3}/g. The molecular weights of the other polyelectrolytes have been estimated from their intrinsic viscosities. The solubilities of the polyelectrolytes are strongly affected by the counterions. Only the sodium salts of the polyelectrolytes are soluble in polar organic solvents, except for La(III), for which the lithium salt also has some solubility.more » The La(III) compounds give a behavior somewhat different from that of the other polyelectrolytes.« less