Solid-state properties of TCNQ, perchlorate, and bromide salts of a phenothiazine derivative

Abstract

Three different salts, perchlorate, bromide, and TCNQ simple salts of the phenothiazine derivative, were prepared. Magnetic susceptibility, diffuse reflectance, and EPR were used to study the electronic properties of these compounds in the solid state. The most paramagnetic is the perchlorate, and bromide is less paramagnetic; this is attributed to the minor steric effect produced by the Br − within a column formed by stacked radicals of promazine +. CT bands of the ClO − 4 are those of a CT between ion radicals stacked flat upon each other where the unpaired π electrons form an overlap which produces a more than pairwise interaction. The stronger interaction among Br − radicals is made evident mainly by a splitting of the CT band. From the ir spectra it can be concluded that the TCNQ-promazine salt is mainly ionic: TCNQ ⨪ Pro ⨥ is diamagnetic as expected in compounds where an almost complete electron transfer is produced as shown by the EPR. TCNQ-promazine shows an absorption spectrum in the solid state with at least three maxima, which can be attributed to three transitions: 1. (a) the lowest-energy transition to TCNQ ⨪: promazine ⨥, 2. (b) the highest-energy transition to a CT among the cation radicals Pr ⨥ : Pr- ⨥, and 3. (c) the intermediate energy band to a CT between the anion radicals TCNQ ⨪ : TCNQ ⨪.