Charge transfer complexes and cation radical salts of azino-diselenadiazafulvalene

The synthesis and the redox behaviour of electroactive donor molecules incorporating an azino spacer group between a benzoselenazole core and another heterocyclic moiety, either a benzoselenazole one or a thiazole one, are reported. Neutral complexes were obtained with TCNQ and, for the first time with dithiadiazafulvalene or diselenadiazafulvalene derivatives, cation radical salts by electrocrystallization. Crystal structures data of these complexes are presented and their geometries compared with those deduced from theoretical calculations.     

Magnetic interaction of tri- and di-oxytriphenylamine radical cation FeCl4 salts

The tetrachloroferrates of the 2,2':6',2':6',6-trioxytriphenylamine (TOT.+.FeCl4-) and 2,2':6',2'-dioxytriphenylamine (DOT.+.FeCl4-) radical cations were prepared, and their structures, magnetic properties, and the relationship between them were investigated. The TOT.+ moiety had a highly planar structure and packed as a dimer surrounded by tetrachroferrates, which also formed a dimer structure. The magnetic properties of TOT.+.FeCl4- were characterized by strong (2J/kB=approximately -1.3x10(3) K, H=-2JS1/2.S1/2) and weak (2J/kB=-1.76 K, H=-2JS5/2.S5/2) antiferromagnetic interactions due to the (TOT.+)2 and (FeCl4-)2 structures, respectively. DOT.+ had a twisted form and no dimer formation was observed between the DOT.+'s and FeCl4-'s. Instead, short contacts between the DOT.+ and chlorine atoms and between the DOT.+'s producing a DOT.+ chain were observed. The magnetic properties of DOT.+.FeCl4- were characterized by a 3D magnetic phase transition to an antiferromagnet with TN=approximately 8 K.     

Synthesis of annulated dioxins as electron-rich donors for cation radical salts

The synthesis of a series of new alkoxylated linearly annulated dioxins is described together with their cyclic voltammetric behavior and some preliminary result on their ability to form cation radical salts. Of these dioxins, seven (8, 12, 19, 21, 27, 33, 34) are the first representatives of entirely new heterocyclic systems. Dioxins 8, 21, 22 and 27 gave good quality cation radical salts upon electrocrystallization.     

Preparation and study of a lithium phthalocyanine radical: optical and magnetic properties

A metallophthalocyanine radical, PcLi, was prepared by electrochemical oxidation of the corresponding dianion. The redox properties in solution show that PcLi is both easily reduced and easily oxidized (ΔE = E^red_1/2-E_1/2^ox = 0.83 V). This property is of the utmost importance for obtaining intrinsic molecular semiconductors. The optical properties are similar to those for oxidized phthalocyanines and involve two low-lying π-π transitions at 430 and 810 nm. Despite the tendency to aggregation, the ESR spectrum of the isolated PcLi molecule has been obtained. It is consistent with an unpaired electron delocalized over the whole phthalocyanine ring.     

Electron spin relaxation of new organic conductors: fluroranthenyl radical cation salts

Crystals of conducting fluoranthenyl (FA) radical cation salts (FA₂)⁺X^? with X^? = PF^?₆, AsF^?₆ show ESR linewidths (ΔH_pp) of ≈15 mOe at T = 293 K at microwave(9.5 GHz) and radio frequencies (230-60 MHz). ΔH_pp is independent of orientation. We analysed longitudinal and transverse relaxation and their dependence on temperature. These salts are suitable as magnetic field probes.     

Intrinsic acidity and redox properties of the adenine radical cation

The intrinsic chemical properties of the gaseous adenine radical cation were examined by using dual cell Fourier transform ion cyclotron resonance mass spectrometry. The adiabatic recombination energy of the radical cation (ionization energy of neutral adenine) was found by bracketing experiments to be 8.55 ± 0.1 eV (at 298 K; earlier literature values range from 8.3 to 8.9 eV). Based on this value, the heat of formation (ΔH_f²⁹⁸) of the adenine radical cation is estimated to be 246 ± 3 kcal/mol. The acidity (ΔH_acid²⁹⁸) of the adenine radical cation was bracketed to be 221 ± 2 kcal/mol. These thermochemical values suggest that the adenine radical cation reacts with neutral guanine by electron abstraction or proton transfer, with neutral cytosine by proton transfer, and via neither pathway with neutral thymine, molecular water or a sugar moiety of DNA (modeled by tetrahydrofuran). Experimental examination of the gas-phase reactivity of the adenine radical cation revealed a slow deuterium atom abstraction from perdeuterated tetrahydrofuran. Hence, in the absence of a nearby guanine or cytosine, the adenine radical cation may be able to abstract a hydrogen atom from a sugar moiety of DNA.     

Electron molecular vibration coupling in vibrational spectra of BEDT-TTF based radical cation salts

The i.r. and Raman spectra of monovalent bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) based charge transfer salts were investigated. The assignment of the fundamental vibrations of the BEDT-TTF radical cation, the identification of the frequency shifts following the ionization of the molecule, and an interpretation of the vibronic bands revealed in the i.r. spectra of these compounds are reported. A normal coordinate analysis together with a semiempirical MNDO calculation of the radical cation electronic structure were used to obtain the electron-molecular vibration coupling constants. The calculated values are in good agreement with the experimental data.     

Mono- and bisadducts from the addition of thianthrene cation radical salts to cycloalkenes and alkenes

Thianthrene cation radical salts, Th(*)(+) X(-)(X(-) = a, ClO(4)(-); b, PF(6)(-); c, SbF(6)(-)), add to cycloalkenes (C(5)-C(8)) in acetonitrile (MeCN) to form 1,2-bis(5-thianthreniumyl)cycloalkane salts and 1,2-(5,10-thianthreniumdiyl)cycloalkane salts, most of which have now been isolated and characterized. These are called bis- (3, 6, 9, 12) and monoadducts (4, 7, 10, 13). The proportional amount of the monoadduct obtained in the initial stage of the reaction varied with the cycloalkene in the order C(6) < C(5) < C(7) < C(8). Thus, the ratio bis:mono for C(5) and C(7) was, respectively, about 80/20 and 50/50. In contrast, only about 5% of the C(6) monoadduct (7a) and none of 7b,c was obtained, while for C(8) none of the bisadducts 12a-c was found. Bisadducts 3 and 9 lost thianthrene (Th) slowly in MeCN solution and changed into monoadducts 4 and 10. A comparable change from 6a into 7a was not observed. The monoadducts, themselves, lost a proton slowly in dry MeCN and opened into 1-(5-thianthreniumyl)cycloalkenes (5, 8, 11, 14). With 3 and 9, particularly, it was possible to follow with NMR spectroscopy the succession of changes, for example, 3 to 4 to 5. The opening of a monoadduct was made faster by adding a small amount of water to the solution. The bisadducts of 4-methylcyclohexene (15a) and 1,5-cyclooctadiene (17a) were isolated and characterized. Although a small amount of monodduct (16a) of 4-methylcyclohexene was found with NMR spectroscopy, it could not be isolated. Bis- and monoadducts were obtained also in additions of Th(*)(+) ClO(4)(-) to acyclic alkenes, in relative amounts that, again, varied with the alkene. From cis-2-butene the dominant product was the bisadduct (18), while the monoaduct (19) was characterized with NMR spectroscopy but could not be isolated. In contrast, trans-3-hexene gave mainly the monoadduct (21), while the bis adduct (20) could not be isolated. With 4-methyl-cis-2-pentene, both bis- (22) and monoadduct (23) were isolated, the former being dominant. The conversion of 18 into 19 was characterized with NMR spectroscopy. In all cycloalkene bisadducts, the configurational relationship of the two thianthrenium groups was trans, while in the monoadducts, the bonds to the single thianthrene dication were (necessarily) cis. In both bis- and monoadducts of acyclic alkenes, the configuration of the alkene was retained. The mechanisms of addition with retention of configuration, of conversion of a bis- into a monoadduct, and of opening of a monoadduct are discussed. Products were identified with a combination of NMR spectroscopy, X-ray crystallography, elemental analysis, and (for cycloalkene adducts) reaction with thiophenoxide ion.     

Physicochemical properties of alkali metal cation-TCNQ anion radical salts

Simple alkali metal cation-TCNQ anion radical salts are classified in two groups from the differences in their physicochemical properties and crystal structures. Li-, Na-, K-, and Rb(I)-TCNQ are comprised in Group A. Li-TCNQ exhibits distinct behavior from other salts in Group A. Rb(II)- and Cs-TCNQ belong to Group B. Phase transitions, electrical conductivities, and absorption spectra in these simple salts are closely related to their crystal structures.     

吩噻嗪衍生物自由基正离子六氯酸锑盐单晶的制备和分子结构

以2,2,6,6-四甲基-4-乙酰氧基哌啶氧铵六氯锑酸盐为单电子氧化剂制备了N-甲基N-乙基, N-正丁基, N-苯基和N-对-硝基苯基等五种吩噻嗪自由基正离子六氯锑酸盐单晶(3a-3e)并对3a和3b作了X射线结构分析, 发现它们的分子构型与其母体中性分子有明显的差别, 说明在自由基正离子中存在着很强的共轭效应和超共轭效应。     

Preparation and properties of some salts of perfluorooctanoic acid

The sodium, potassium, lithium, caesium, barium, calcium, silver, lead and ammonium salts of perfluorooctanoic acid were prepared. Their thermal stabilities, and some spectroscopic data are reported. An attempt is made to correlate some of these measurements with the properties of the metal ions or metals concerned.     

Preparation and magnetic properties of manganite

A new hydrothermal synthesis of manganite is described, and the magnetic and electron paramagnetic resonance (EPR) behavior of the product is reported. The magnetic susceptibility is nearly independent of temperature above 90°K and increases dramatically on cooling to 30°K. The EPR lineshape, linewidth, and g-factor at 296°K are Lorentzian (in the central region), 280 ± 10 G, and 1.997 ± 0.006, respectively. The EPR spectrum is interpreted in terms of nearly one-dimensional interactions between identical Mn moments. The results of this study support the view that all Mn ions are trivalent and that the magnetic interactions between these ions are nearly one dimensional.     

Physicochemical properties of an N-decylpyridinium tetrachloroferrate ionic liquid

A low-temperature ionic liquid N-decylpyridinium tetrachloroferrate was synthesized. The temperature dependences of density and viscosity of the synthesized ionic liquid, as well as its thermal stability and magnetic properties were studied. The response of N-decylpyridinium tetrachloroferrate to magnetic field was visualized, and its structure was calculated at the DFT/B3LYB/6-31G(d,p) level of theory.     

Study of the fluorescence of perylene cation radical salts with a near field optical setup

A perylene-acetonitrile solution with TBAP (tetra-n-butylammonium perchlorate) electrocrystallizes on the electrode surface, under opportune conditions. It forms particular needle-like micro-crystals that have been studied recently for their peculiar electrical and optical properties and for the fundamental processes involved in the electron transfer responsible for the electrocrystallization. These intriguing structures present various fractal-like morphological organizations and diverse crystal shapes on the same deposition process. Up to now these formations have been studied optically by conventional standard microscopy. We introduce here a novel methodology to collect information on the actual orientation and crystal structure by a near field optical setup with originally fabricated probes. We performed, for the first time on these samples, near field fluorescence imaging showing evidence that the perylene aggregations actually have a distinct optical orientation.     

Reaction of triphenylphosphine radical cation with cycloalkenes: electrochemical one-step preparation of 1-cycloalkenyltriphenylphosphonium salts

Constant current electrolysis of triphenylphosphine in dichloromethane at a graphite anode in the presence of cycloalkenes gave the corresponding 1-cycloalkenylphosphonium salts in reasonable yields.     

An Isolation and liquid phase EPR spectra of the cation radical salts of N-methyl and N-ethylphenothiazinium perchlorate

N-Methyl and N-ethylphenothiazines were oxidized with bromine and sodium perchlorate to give stable cation radical salts. Their well-resolved epr spectra were obtained in nitromethane solution. In order to assign the hfs constants, the cation radicals of N-deuteriomethyl and N-deuterioethylphenothiazines were prepared with lead tetraacetate and trifluoroacetic acid in solutions.