Dication Salts Research Articles

Reactivities, Conformational Properties, and Molecular Structures of σ-Bonded Cyclic Selenurane Dications

Abstruct: The synthesis of σ-selenurane dication salts via transannular interactions and the reactivities of these dication salts are described. The X-ray crystallographic analyses of the dication salts show that the dications have selenium atoms in a trigonal-bipyramidal bonding environment. Ab initio calculations carried out for the dication revealed that the selenium atoms exclusively carry the positive charge. The interesting conformational properties of these dications are also described.

A Novel Synthetic Route to Sapphyrins

New methodology has been developed for the synthesis of so-called sapphyrins, pentapyrrolic “expanded porphyrins”. An efficient approach involving acid-catalyzed condensation of 1,19-diunsubstituted a,c-biladienes and 3,4-dialkylpyrrole-2-carbaldehydes eliminates the preparation of bipyrrolic intermediates and allows the synthesis of sapphyrins with an unsymmetrical array of peripheral substituents. The β-substitution pattern of 2,3,13,17-tetraethyl-7,8,12,18,22,23-hexamethylsapphyrin has been unambiguously confirmed by single crystal X-ray crystallography. 1H NMR spectra of the dication salts of sapphyrins are strongly dependent upon the counterions, and the pattern of resonances observed in solution is related to the stacking interactions between the macrocycles.

Novel Bis (1,3-Dithiole) Electron Donors by Oxidative Intramolecular Cyclization of 2,2′-Bis(1,4-Dithiafulven-6-yl)-3,3′-Bithienyls

2,2′-Bis(1,4-dithiafulven-6-yl)-3,3′-bithienyls 6 were prepared by using either a Wittig or a Wittig-Homer reaction. The cyclic voltammograms of 6 revealed that they undergo an intramolecular cyclization by electrochemical oxidation. Chemical oxidation of 6 with tris(4-bromophenyl)aminium hexachloroantimonate gave intramolecular cyclization products 16 as dication salts. The hexachloroantimonate ion was found to act as an oxidizing agent in the reaction. Chemical reduction of the dication salts with zinc afforded the corresponding neutral bis (1,3-dithiole) donors 7 in high yields. The cyclic voltammograms of 7 showed reversible one-stage two-electron oxidation waves, and the potentials are fairly low. A conductive TCNQ complex was formed from one of them. X-ray analyses of the neutral and dication states of the donor show that there is a large conformational change between them.

First molecular and electronic structure determination of the dicationic salt of 1,11-(methanoselenomethano)-5H,7H-dibenzo[b,g] [1.5]diselenocin by X-ray crystallographic analysis and ab initio calculation

T. Nakahodo, O. Takahashi, E. Horn and N. Furukawa, Chem. Commun., 1997, 1767 DOI: 10.1039/A704431C

Highly-Oxidized States of Organic Donor Bis(ethylenedioxy)tetrathiafulvalene (BEDO-TTF)

Abstract The monocation and dication salts of bis(ethylenedioxy)-tetrathiafulvalene (BEDO-TTF) were newly obtained by chemical oxidation by iodine. Their structural and physical properties are discussed.

Transannular Te−S Interaction in a New Tellurium Heterocycle, 5H,7H-Dibenzo[b,g][1,5]tellurathiocin

A new heterocycle containing tellurium and sulfur atoms, 5H,7H-dibenzo[b,g][1,5]tellurathiocin (1), has been synthesized. The chair and the boat forms of 1 can be characterized by 1H, 13C, and 125Te NMR spectroscopy. A transannular bond between the tellurium and sulfur atoms was found in the reaction product of 1 with concentrated H2SO4 by 1H, 13C, and 125Te NMR spectroscopy. Two-electron oxidation of 1 with 2 equiv of NOPF6 gave the tellurathia dication salt (3) (Te+−S+, 2PF6-), which acts as an oxidizing agent. The reaction of 12-oxo-5H,7H-dibenzo[b, g][1,5]tellurathiocin (8) with acetic anhydride afforded a 12,12-diacetoxy-substituted tellurane (16). Heating of a benzene solution of 16 gave a remote α-acetoxylated sulfide 18 and the parent 5H,7H-dibenzo[b, g][1,5]tellurathiocin (1). Reaction of tellurathiocin 1 with t-BuOCl gave exclusively its telluroxide 8. Tellurathiocin 1 was reacted with Br2 to give a 12,12-dibromo-substituted tellurane (25). Reaction of the tellurane 25 with aqueous NaOH gave the...

Preparation and crystal structure of a new tetracoordinated cyclic selenurane with two unsymmetrical apical ligands of oxygen and selenium: transannular hypercoordination between oxy- and diseleno-groups

The reaction of a selenoxide 2 of 1,11-(methanoxomethano)-5H,7H-dibenzo[b,g][1,5]-diselenocine 1 with triflic anhydride gives a new selenurane dication salt 3 with two unsymmetrical apical oxy- and seleno-ligands, i.e. the chair form of 2 is changed to the boat form of 3 by the three centre transannular interaction between the oxygen and the two selenium atoms.

Dication salts of BEDT-TTF

Abstract Dication salts of the organic donor bis (ethylenedithio)tetrathiofulvalene (BEDT-TTF), BEDT-TTF(ClO 4 ) 2 and BEDT-TTF(BF 4 ) 2 , have been prepared by electrocrystallization from an oxidizing solvent medium. The crystal structures of the isostructural salts are described and bondlengths in the dication are discussed.

Spectroscopic study of solid BDNT and its monocation and dication salts

The polarized reflection spectra of BDNT, BDNT-PF6 and BDNT-(PF6)2 have been measured on several crystal faces of the single crystals and compared with the solution spectra of BDNT, BDNT+ and BDNT2+. The spectra of the BDNT crystals have been successfully interpreted in terms of the theory of directional dispersion. Based on this interpretation, the electronic spectra of BDNT, BDNT+ and BDNT2+ have been reasonably assigned to the electronic transitions expected from the molecular orbital calculations. We found a disproportionation reaction in the acetonitrile solution of m-BDNT-PF6, which means that the dication state is close to the monocation state. This is in accord with the low excitation energy (3.5 × 103 cm–1) of the charge-transfer band in m-BDNT-PF6. The vibrational bands of BDNT, m-BDNT-PF6 and BDNT-(PF6)2 are presented and discussed.

Electro-oxidation of substituted conjugated sexithienyls

A new series of conjugated α-sexithienyls derivatized by alkyl and oxyalkyl groups has been synthesized. Although of comparable electronic inductive effects, these substituents produce important differences in the electrochemical behavior of the π-conjugated system. Long alkyl or oxyalkyl chains lead to an enhancement of electrochemical reversibility and a stabilization of the cation radical state. The electrodeposition of these oligomers has been achieved by means of recurrent potential scans. Analysis of the electrodeposition process and of the electrochemical behavior of the resulting materials suggests that, whereas in polar solvents radical coupling occurs and leads to extensively conjugated polymers, in methylene chloride electrodeposition seems to proceed via the di-cation state and to produce essentially the corresponding di-cation salt.

Crystal structure and physical properties of dication radical salts of cyclophane-shaped twin donor

Radical dication salts ( 2·(ClO 4) 2) was obtained by using twin donor ( 2). Conformation of the oxidized donor is a cyclophane-type with significant electronic interaction. Observation of a charge-transfer band (0.97 eV) in the absorption spectrum and detection of a thermally populated triplet signal ( ΔE ST = 0.27 eV) by ESR spectroscopy enables to estimate electronic parameters of U and t to be 0.70 eV and 0.26 eV, respectively.

Preparation and reactivity of dichalcogenide (S, Se) dication salts from medium-sized cyclic bis-sulfide and bis-selenides

The disulfide dication salt, 1,5-dithioniabicyclo[3.3.0]octane bis(trifluoromethanesulfonate) ( 3), was isolated from the reaction of 1,5-dithiacyclooctane 1-oxide with trifluoromethanesulfonic anhydride. Two-electron oxidation of 1,5-diselenacyclooctane with two equivalents of NOPF 6 or NOBF 4 gave the first diselenide dication salt, 1,5-diselenoniabicyclo-[3.3.0]octane bis(hexafluorophosphate) or bis(tetrafluoroborate ( 5). The disulfide and diselenide dication salts ( 3 and 5) act as an oxidant or as an electrophile depending on the added reagents.

The dication of 1,4,5,8-tetrakis(dimethylamino)naphthalene: properties, crystal structure and a comparison with the dication of 1,4-bis(dimethylamino)benzene

The dication salt 4·(I3–)2 of 1,4,5,8-tetrakis(dimethylamino)naphthalene 3 is isolated and its molecular structure established by X-ray crystallographic analysis; spectral data of 4 are compared with those of the dication 2 of 1,4-bis(dimethylamino)benzene, determined in the presence of an oxidant, i.e. Br2, Ag+.

Formation of Unusual Valent Organic Sulfur and Selenium Compounds via Transannular Interaction

Abstract 1,5-Dithia- and diselenacyclooctane [1,5-DTCO and 1,5-DSeCO] were prepared and converted to the dication salts using NOPF6 or conc. H2SO4. The structures of the salts were determined by the x-ray crystallographic analysis revealing that σ-bond is formed between the two sulfur or selenium atoms. Several other sterically congested dications derived from dibenzothiocin, 1,9-disubstituted dibenzothiophenes and the corresponding selenium compounds were synthesized and their structures were estimated on the basis of their 1H-, 13C- and 77Se nmr spectroscopy. The dications of trissullde, 1,11-(methanothiomethano)-5H,7H-dibenzo[b,g][1,5]-dithiocin and the selenium analog were generated. Inspection of their nmr spectra revealed that the central sulfur or selenium atom in these salts should have a hypervalent bonding structure, 10-S-4(C2S2), or 10-Se-4(C2Se2) which was further confirmed by the 77Se-nmr coupling constants.

Distorted Molecules: Perturbation Design, Preparation and Structures

AbstractThe structure of a molecule can change considerably as its energy and thus its electron distribution within the time‐domain of dynamic relaxation varies. Based on comparison of approriate measured data of related compounds and supported by quantum chemical calculations, therefore, charge‐perturbed and/or sterically overcrowded molecules can be designed. Their preparation, handling, and structural characterization, frequently under extreme and especially largely aprotic conditions, provides some surprises. New structural principles become evident and old‐fashioned ones are confirmed. Thus the contact‐ion aggregates that form on ultrasonically supported reduction of unsaturated hydrocarbons with sodium metal partly contain dibenzene sodium sandwiches. Vicinal dimethylamino substituents or isoelectronic isopropyl groups cause steric overcrowding and facilitate oxidation to molecular cations by energetically favorable delocalization of the generated positive charge. Molecules and molecular ions in which an even number of π electrons are distributed over a σ skeleton containing an odd number of centers preferentially form cyanine subunits. This is demonstrated by the novel ethene dication and dianion salts with central CC single bonds and molecular halves twisted relative to each other. Altogether in two years well over 50 structures have been determined. Much has been learned from them, especially about electron transfer and contact ion‐pair formation in aprotic solvents. Nevertheless, we had to realize that answers to many questions, above all “what crystallizes, how, and why”, are still out of reach.

σ-Bonded Dications from Medium-Sized Selenium and Tellurium Heterocycles

Abstract The two-electron oxidation of 1,5-diselenacyclooctane (1) or 1,5-ditelluracyclooctane (3) with 2 equiv of NOBF4 gave the diselenide dication salt, 1,5-diselenoniabicyclo[3.3.0]octane bis(tetrafluoroborate) (2), or the ditelluride dication salt 4. The structures of the dications were characterized by 77Se and 125Te NMR spectroscopy and X-ray crystallographic analysis. The diselenide dication salt 6 having aromatic ring was formed in the reaction of 5H,7H-dibenzo[b,g][1,5]diselenocin 6-oxide (5) with 2 equiv of silylating reagent, CF3SO3SiMe3. These dications react either as an oxidant or as an electrophile depending on the added reagent.

Formation of Dication and Hypervalent Bond from 5H,7H-Dibenzo[b,g][1,5]Selenazocine

Abstract The reaction of the selenoxide 2 of N-methyl-5H,7H-dibenzo-[b,g][1,5]selenazocine (1) with (CF3SO2)2O gave the selenaza dication salt 3 which acts as an oxidizing agent. A novel σ-selenurane 4 was prepared by either the reaction of selenide 1 with t-BuOCl or the reaction of selenoxide 2 with SOCl2; the crystal structure of 4 shows the chloroammonioselenurane with a distorted trigonal-bipyramidal geometry around the selenium atom.

Synthesis of a New Tellurium Heterocycle, 5H,7H-Dibenzo[b,g][1,5]tellurathiocin, and Isolation and Reactivity of Its Tellurathia Dication Salt

Abstract A new heterocycle containing tellurium and sulfur atoms, 5H,7H-dibenzo[b,g][1,5]tellurathiocin (1), has been synthesized. The transannular bond formation between tellurium and sulfur atoms was found in the reaction of 1 with coned H2SO4 by 1H, 13C, and 125Te NMR spectroscopy. Two-electron oxidation of 1 with 2 equiv. of NOPF6 gave the tellurathia dication salt 3 ( > Te+–S+ < 2PF6−) which acts as an oxidizing agent.

Magnetic Properties in Charge-Transfer Complexes of High-Symmetry Organic Acceptors

ABSTRACTTris(l, 2-benzodithio)- and tris(l, 2-ethylenedithio)-trimethylenemethane dication salts were synthesized for the purpose of using as an acceptor in the formation of charge-transfer (CT) complexes with some dianionic donors. In the CT complexes of these dications with hexacyanotrimethylenecyclopropane and tetrafluorotetracyanoquinodimethane dianions, in which the CT degree is albeit small, the spin-spin interaction between the cation radical and the anion radical was antiferro magnetic in the temperature range of 60–293 K, but changed to a ferromagnetic one in the lower temperature range till 15 K, the lowest temperature used in this experiment. This provides the first demonstration of ferromagnetic spin-spin interaction in purely organic/molecular CT complexes. It is conceivable that the ferromagnetic spin-spin interaction is caused by a“spin polarization”mechanism rather than a“CT configurational mixing”mechanism.

Metal Complexes with Tetrapyrrole Ligands, LXI. Structure and Products of Electrochemical Oxidation of Zirconium(IV) and Hafnium(IV) Bisporphyrinate Double‐Deckers

The electrochemical oxidation of zirconium and hafnium double‐deckers M(P)2 (M=Zr, Hf; P=OEP, TPP) (Scheme 1)2) leads to mono‐ and dications which show near infrared absorption bands which are of ≈ 2000 cm‐1 higher energy than those of the corresponding cerium double‐decker cations. [Zr(OEP)2]X, [Zr(OEP)2]X2, and [Zr(TPP)2]X (X=ClO4− and PF6−) are isolated after electrochemical oxidation and are characterized by IR and NMR spectroscopy. Magnetic susceptibility measurements (2 K < T < 300 K) of the solids confirm the strong coupling of the electron spins in the diamagnetic dication salt [Zr(OEP)2][ClO4]2. The molecular structure of Zr(OEP)2 is elucidated by an X‐ray structural analysis.