Evgeniya I. Yudanova

New molecular complexes of fullerenes C60 and C70 with tetraphenylporphyrins [M(tpp)], in which M=H2, Mn, Co, Cu, Zn, and FeCl.

New molecular complexes of fullerenes C60 and C70 with tetraphenylporphyrins [M(tpp)] in which M-H2, MnII, CoII, CuII, ZnII and Fe(III)Cl, have been synthesised. Crystal structures of two C60 complexes with H2TPP, which differ only in the number of benzene solvated molecules, and C60 and C70 complexes with [Cu(tpp)] have been studied. The fullerene molecules form a honeycomb motif in H2TPP.2C60. 3C6H6, puckered graphite-like layers in H2TPP.2C60.4C6H6, zigzag chains in [Cu(tpp)].C70.1.5C7H8.0.5C2HCl3 and columns in [Cu(tpp)]2.C60. H2TPP has van der Waals contacts with C60 through nitrogen atoms and phenyl groups. Copper atoms of the [Cu(tpp)] molecules are weakly coordinated with C70, but form no shortened contacts with C60. The formation of molecular complexes with fullerenes affects the ESR spectra of [M(tpp)] (M = Mn, Co and Cu). [Mn(tpp)] in the complex with C70 lowers its spin state from S = 5/2 to S = 1/2, whereas [Co(tpp)] and [Cu(tpp)] change the constants of hyperfine interaction. ESR, IR, UV-visible and X-ray photoelectron spectroscopic data show no noticeable charge transfer from the porphyrinate to the fullerene molecules.

Experimental observation of C60 LUMO splitting in the C602− dianions due to the Jahn–Teller effect. Comparison with the C60˙− radical anions

New fullerene salts (TMP(+))2·(C60(2-))·(C6H4Cl2)2 (1), {DB-18-crown-6·[Na(+)]·(C6H5CN)2}2·(C60(2-))·C6H5CN·C6H4Cl2 (2), {cryptand[2,2,2]·(Na(+))}2·(C60(2-)) (3) and (PPN(+))2·(C60(2-))·(C6H4Cl2)2 (4) were obtained as single crystals. Their crystal structures were solved and their optical and magnetic properties were analyzed. The spectra of the salts in the IR and UV-visible-NIR ranges indicate the formation of C60(2-) dianions in 1-4. These salts show similar behavior in EPR measurements, explained by the diamagnetic ground state of the C60(2-) dianions and the thermal population of the excited triplet state, which is separated by an energy gap of 487-540 cm(-1). The magnetic susceptibility of 4 also increased above 130 K due to the population of the excited triplet state. The observed splitting of the C60 LUMO is attributed to the Jahn-Teller (JT) effect. We analyzed the splitting by an extended Hückel method using the single-crystal structural data for the compounds containing neutral, mono- and dianions of C60. The splitting of the initially triply degenerated C60 LUMO produces three molecular orbitals. The gap between the lowest and highest orbitals is very small in neutral C60 (128-140 cm(-1)), it increases in C60(˙-) (500-710 cm(-1)) and increases further in C60(2-) (1080-1670 cm(-1)). It was found that the splitting of the C60 LUMO is realized in different ways for the mono- and dianions. The ground and first excited state are separated in C60(˙-) by a small gap of 55-180 cm(-1) only. This gap is noticeably larger in the C60(2-) dianions and falls into the 760-1390 cm(-1) range.

New complexes of fullerences C60 and C70 with CoII and MnII tetraphenylporphyrinates and their ESR study

Complexes of fullerenes C60 and C70 with cobalt(II) and manganese(II) tetraphenylporphyrinates of compositions Mn(TPP)·(C60)2(CS2)1.5 (1), Mn(TPP)·C70(CS2)x, wherex<=1.25 (2), Co(TPP)·C60(CS2)0.5 (3), and Co(TPP)·C70(CS2)x, wherex<0.25 (4), were synthesized and studied by ESR spectroscopy. At 77 K, complexes1 and2 have singlet ESR spectra characteristic of the low-spin (S=1/2) state of MnII, withg=2.002 and linewidths of 250 G and 300 G, respectively, and differing significantly from that of the initial MnII(TPP) (g1=5.9 andg=2.0,S=5/2). The spectra of complexes1 and2 exposed to oxygen exhibit hyperfine structure due to interaction with55Mn and14N nuclei. The ESR spectra of complexes3 and4 are asymmetric (=2.4, ΔHpp=(500–600) G), which is due to the overlap of parallel and perpendicular spectral components. The absence of ESR signals from C60.− and C70.− radical anions makes it possible to conclude that the formation of complexes1–4 is not accompanied by electron transfer from Co(TPP) and Mn(TPP) to fullerences C60 and C70.

Iodine doping of c60 charge transfer complexes

Abstract Iodine doping of C 60 complexes with organic donors were carried out. The solvent was gradually substituted by the iodine with the formation of TPDP(C 60 ) 2 I 10 , (TMDTDM-TTF) 2 C 60 I 7.5 , and DBTTFC 60 I 9 compounds. The doping results in strong changes in the donor electron state but only indirectly affects the C 60 electron system.

Crystal structure, ESR and conductivity studies of bis(ethylenedithio)tetrathiafulvalene (ET) organic conductor (H8-ET)2[Hg(SCN)2Br] and its deuterated analogue (D8-ET)2[Hg(SCN)2Br]

Abstract Protonated (I) and deuterated (II) crystals of (ET) 2 [Hg(SCN) 2 Br] (ET = bis(ethylenedithio)tetrathiafulvalene) are isostructural with B 2/ b space group and Z = 4. Crystal structure consists of (ET) 2 + dimers forming a κ-type motif and arranged in layers parallel to the bc -plane which are separated by anionic sheets of polymeric anions. A two-positional disorder exists in ethylene groups of deuterated ET molecules, while such disorder appears only in one of the ethylene groups in the hydrogenated salt. The crystals exhibit semimetallic behaviour at high temperatures with a transition to non-metallic state at 100 K for salt I and 60 K for salt II as is shown from d.c. conductivity measurements. Electron spin resonance (ESR) g factor and linewidth and their temperature behaviour are extensively discussed on the basis of existing theories and experimental data for low-dimensional organic conductors. The linewidth is determined by spin-phonon scattering driven relaxation processes which are mediated by Peierls fluctuations in the conducting phase and by spin-lattice relaxation processes below the critical temperature. The first-order phase transition in hydrogenated salt at 100 K is associated with a localization of electrons on ET dimers, whereas the transition of semiconductor-semiconductor type with possible magnetic ordering is suggested for deuterated salt. A considerable isotope effect in (ET) 2 [Hg(SCN) 2 Br] is considered to be related to a weak hydrogen bond between the terminal ethylene group of ET dot;+ and the bromine atom of the anion in hydrogenated salt. A discussion of the nature of the phase transitions is given.

The formation of diamagnetic singly bonded (C70−)2 dimers in ionic complexes of fullerene C70 with tetrakis(dimethylaminoethylene)

Two complexes containing C70 anions and tetrakis(dimethylamino)ethylene radical cations (TDAE˙+)·(C70−)·(C6H4Cl2)·(C6H14)0.5 (1) and (TDAE˙+)·(C70−)·(C6H4Cl2) (2) were obtained as single crystals. Both complexes contain singly bonded (C70−)2 dimers and have close composition. However, their crystal structures are different. Complex 1 has a layered structure in which layers from the (C70−)2 dimers alternate with the TDAE˙+-C6H4Cl2 layers. Ionic fullerene layers contain large hexagonal vacancies which are occupied by completely ordered hexane molecules. Complex 2 has a three-dimensional packing of the (C70−)2 dimers with large vacancies passing along the c axis and containing TDAE˙+ and C6H4Cl2 moieties. IR spectra of the (C70−)2 dimers in both complexes show similar features with more than 40 absorption bands additionally to the absorption bands of parent C70. According to the IR spectra the (C70−)2 dimers are stable in 1 and 2 up to room temperature. Both complexes show narrow EPR signals characteristic of TDAE˙+ (g = 2.0032, the linewidth of 0.3–0.4 mT at 77 K).

Selective reduction of fullerene C60 by metals in neutral and alkaline media. Interaction of C60 with KOH

The reduction of fullerene C60 by Zn and Mg in DMF was studied both in the presence and absence of KOH. Fullerene C60 was reduced in these systems to form the C60n– (n = 1, 2, and 3) anions. The anions were detected by optical and ESR spectroscopies. It was found that Mg reduced C60 to the monoanion, Mg/KOH and Zn reduced C60 to the dianion, and Zn/KOH reduced C60 to the trianion. Like KCN, potassium hydroxide adds to fullerene upon interaction with C60 in DMF. The reaction of C60 with KOH in benzonitrile was accompanied by the generation of the fullerene monoanion. A possible mechanism of the formation of fullerene monoanions in the presence of KOH is discussed. The degradation of the C60n– anions in air was studied.

The new salt κ-ET2[Hg(SCN)2I] : crystal structure and physical properties

Abstract The structure, resistivity and ESR of a new organic conductor κ-ET 2 [Hg(SCN) 2 I](ET=bis(ethylenedithio) tetrathiafulvalene) are studied. Its main crystallographic parameters are found to be: M -1213.2, a -38.03(1), b = 11.80(1), c = 8.329(9) A; γ=98.1(2)°; V -3700(2) A 3 ; space group P 2 1 Ib ; Z = 4. It is shown that the radical cations are packed according to the κ-type in the organic sheets, and the anions form polymerized chains. Two different radical cation layers with different amounts of shortened S···S contacts and distinct interaction between anionic and cationic sheets are found. ESR linewidth is found to be 9-11G (300 K), which is substantially narrower than a typical linewidth for ET-based radical cation salts of the κ-type. Based on temperature dependences of the resistance anisotropy and ESR parameters, we suggest that a structure rearrangement with electron localization may take place around 50 K. The comparison of crystal structure and properties of the title compound with other salts of the family ET 2 [Hg(SCN) 3 − n X n ], where X=Cl, Br, and n = 1.2, is camed out.

The first complex of C60 fullerene with bis(ethylenedithio)tetrathiafulvalene radical cation: C60·(BEDT-TTF·I3)

The complex of C60 fullerene containing the radical cation of the organic donor,viz., C60·(BEDT-TTF·I3), where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, was synthesized for the first time. Single crystals of the complex were grown in benzonitrile. The crystals of this compound belong to the monoclinic system with a base-centered lattice. The unit cell parameters are as follows:a=17.419(6),b=9.997(4),c=13.499(1) Å, β=99.00 (1)o. The IR and electronic spectra of single crystals of the complex have absorption bands characteristic of the BEDT-TTF.+ radical cation and neutral C60. The ESR spectrum has a signal withg=2.0074 and δHpp=23 G belonging to BEDT-TTF.+. The position of the 13d5/2 peak in the X-ray photoelectron spectrum confirms the formation of the I3− anion.

New organic conductor (EDOEDT)4Hg3Br8 comprising cation layers of α″- and κ(4×4)-types

Abstract The (EDOEDT) 4 Hg 3 Br 8 radical cation salt of 4,5-ethylenedioxy-4′,5′-ethylendithiotetrathiafulvalene has been synthesized as a mixture of two crystalline phases. Phase 1 is characterized by a semiconducting type of conductivity and the ESR peak-to-peak linewidth equal to 70–95 G. Phase 2 exhibits metal-like conductivity down to 105 K and the ESR peak-to-peak linewidth of 35–54 G. The X-ray crystal structure analysis of phase 1 reveals three crystallographically distinct donor molecule layers in the asymmetric part of the unit cell, one of them being composed of the stacks and the two others are built of mutually perpendicular tetramers. The polarized reflectance spectra of phase 1 are discussed.