1,9-Dithiophenalenyl system

Abstract

The 1,9-dithiophenalenylium cation has been prepared as a stable hexafluorophosphate salt, by reaction of 9-ethoxyphenalenone with phosphorus pentasulfide. The compound has been fully characterized and a M I N D 0 / 3 SCF MO calculation of the ground-state structure is reported. The compound is shown to undergo three one-electron reduction steps (without decomposition) the first two of which are reversible. Moderately highly conducting charge transfer salts are obtained with TCNQ derivatives. The 1,9-dithiophenalenyl radical has been prepared in solution by electrochemical and chemical reduction of 1,9-dithiophenalenylium hexafluorophosphate. The compound has been subjected to ESR, mass, and electronic spectral examination. The radical is found to be monomeric in solution in the temperature range between 18 and -95 OC. The observed ESR hyperfine splittings are consistent with the removal of spin density from the phenalenyl nucleus by disulfide substitution.Odd alternant hydrocarbons are unique in their ability to form stable cations, radicals, and anions' which are of very similar molecular geometry.2 They may therefore be of interest in the development of organic metals, where such characteristics have been suggested to be i m p~r t a n t .~-~ The chief obstacle to their utilization in this respect is the propensity of the neutrals radicals for dimerization-in fact we are not aware of any planar carbon-based radical which is wholly monomeric in solution and/or the solid state. The phenalenyl (PLY) (lb) Ib radical, while particularly stable, is known to dimerize at low temperatures in solution.5s6 W e therefore sought to stabilize the triad of oxidation states and particularly the radical in a way which would not seriously perturb the desirable electronic properties of the P L Y nucleus or inhibit intermolecular interactions in the solid state.The 1,2-dithiolyl system also provides a number of accessible oxidation states.j Thus the 3,5-diphenyl-l,2-dithiolylium cation (2a) has been shown to undergo three reduction steps;j again the neutral radical (2b) is found to be in equilibrium with 2b, R , = R, = P h ; R, = H f , R , = R, = P h ; R, = H 3 the dimer.' W e therefore sought to combine these two components (1 and 2) in the 1,9-dithiophenalenyl system (DTPLY) (4). W e felt that this species might be interesting in its own ' W ' s-s 4b right, as well as providing some insight into the effectiveness of incorporating sulfur into the PLY nucleus.t City University of New York Results and DiscussionSynthesis and Characterization of the 1,9-Dithiophenalenylium Cation (4a) and 1,9-DithiophenalenyI (4b). Our initial efforts to obtain 4a began with 9-hydroxyphenalenone (5),*-1° to which we applied the standard reagents for conversion of a @hydroxy ketone into a 1,2-dithiolylium salt.11%12 Presumably as a result of the very strong hydrogen bonding in this compound,1° the material was found to be inert to the usual procedures, except under particularly forcing conditions from which no characterizable products could be recove...

Recent Advances in the Chemistry of Phenalenyl

“…Although the chemical reactivity 4,7 10 and physical properties 3,5,11,12 of phenalenyl radical (1) have been extensively studied since its rst generation about 60 years ago, its solid state properties were not reported before we isolated phenalenyl radical in the crystalline state. Because kinetic stabilization is very effective for making radicals persistent, tert butyl groups were introduced to suppress the σ bond formation in the solid state.…”

“…4 Later, Agranat proposed reactive intermediates, E and Z biphenalenylidene (E, Z 10) and dihydroperopyrene (11), for the decomposition pathway from 2 to 3 (Scheme 4). 39 However, these intermediates have not been experimentally determined because of the rapid decomposition into 3.…”

Electronically Stabilized Nonplanar Phenalenyl Radical and Its Planar Isomer

“…These spin densities correlate with the hyperfine coupling constants, allowing spectra which match with the experimental spectra to be simulated (see Figure 6 including Figure S3 & S4 in the Supporting Information). It is noteworthy that the spin densities at the α-position of the phenalenyl skeleton are below the corresponding spin densities of 1,9-dithiophenalenyl 3 (0.51 mT & 0.54 mT) 28,29 indicative of a higher stabilization of 8 and 9 compared with 3. Using the bond lengths obtained from the X-ray data, Harmonic Oscillating Model of Aromaticity (HOMA) 43 indices were calculated using the HOMA model formula.…”

“…33,34 Pioneering work in this field has been performed by Haddon et al leading to the synthesis of 1,9-dithiophenalenyl 3 stabilized via a disulfide bridge. 28,29 Meanwhile, our groups previously reported the first example of electronic stabilization by an oxygen atom in the phenalenyl species naphtho [2,1,8-mna]xanthenyl (4), which was generated by reduction of the parent cation. 35 Further planar stable open-shell species have 2 been prepared by Kubo et al which are stabilised through delocalization in a large polyaromatic framework.…”

Synthesis, Structure and Solid State Properties of Cyclohexanemethylamine Substituted Phenalenyl Based Molecular Conductor

“…Since then synthetic efforts have led to the crystallization and characterization of several types of PLY derivatives by chemical modification [16][17][18][19][20][21][22][23]. Heteroatom functionalization of neutral radicals such as thio-substituted PLY [24][25][26], azaphenalenyls [12,27,28], and bisphenalenyl boron complexes [29,30] have played a crucial role in the recent progress in phenalenyl chemistry and the important developments in heterocyclic radicals [31][32][33][34][35].…”