Design of New Stable Radicals for Molecular Magnetic Materials

Theoretical Analysis of Heteroaromatic Thioaminyl Radicals. Part 2: A Comparison of Ab Initio and Density Functional Methods in the Description of Redox Processes

“…Our interest in liquid crystal radicals − prompted us to develop reliable computational protocols for predicting properties of new open-shell π-conjugated heterocycles suitable for construction of liquid crystalline materials, and hence rational design of new materials with desired bulk magnetic and electrical behavior. Among the key parameters in the design is the redox behavior of the mesogenic radicals.…”

Theoretical Analysis of Heteroaromatic Thioaminyl Radicals. Part 1: A Comparison of Ab Initio and Density Functional Methods in Calculations of Molecular Geometry and Isotropic Hyperfine Coupling Constants

“…Over the past decade, heterocyclic radicals containing the thioaminyl fragment −N−S− have become attractive building blocks for molecular conductors − and magnetic materials. − Extensive studies of these neutral π radicals resulted in several dozen well-characterized structures − (e.g., 1 − 11 in Figure ), which are typically high-melting solids but some derivatives form paramagnetic liquids. , Structural versatility of the −N−S− fragment and the generally observed relatively high chemical and thermal stability of the heterocycles provides opportunities for further investigation of new radicals and materials. In this context, we began study of these radicals as potential structural elements for a new class of liquid crystals. −

1 Selected resonance structures for radicals 1 − 11 .

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“…Calculations of molecular and electronic structures of cyclic thioaminyl radicals have been performed using semiempirical methods ,,,− and more recently with the Hartree−Fock (HF), MP2, and DFT methods. ,− There have been, however, no systematic and comprehensive computational studies for these radicals. The semiempirical methods yield a qualitative understanding of the electronic structures, and only the inclusion of correlation treatment such as CASSCF and MP(n) gives reasonably good agreement with the experimental data. , While the CI and Møller−Plesset methods are prohibitively expensive for large molecular systems, density functional methods (DFT) provide an attractive, low-cost alternative.…”

Preparation of a discotic 2,4,7,9‐tetraaryl‐6H‐dibenzo[c,e][1,2]thiazine and generation of a persistent Radical

“…Several years ago, we demonstrated that dibenzo [c,e][1,2]thiazinyl (1a) and also cinnolino [5,4,3][c,-d,e] [1,2]benzothiazinyl can be generated in solution, and have moderate stability sufficient for use as structural elements in paramagnetic discotic liquid crystals [7]. Our investigations of the closely related series of benzo[c]-cinnolines [8] and carbazoles [9] indicated that substitution of 1a with four 3,4-dioctyloxyphenyl groups should induce discotic behaviour in 1b.…”

“…One manifestation of these interactions is anisotropic electric conduction along the stacks [3]. We have been interested in exploiting this intermolecular electronic communication to engineer spin-spin interactions of open-shell molecules [4] and to study their magnetic properties in discotic phases. In this context, we designed a new class of conventional discotic materials containing an electrically neutral spin delocalized in the p system of the central heteroaromatic core [5,6].…”