D.V. Konarev

New complexes of fullerenes C60 and C70 with organic donor DBTTF: synthesis, some properties and crystal structure of DBTTF . C60 . C6H6 (DBTTF = dibenzotetrathiafulvalene)

Abstract New complexes of fullerenes C 60 and C 70 with dibenzotetrathiafulvalene (DBTTF), DBTTF·C 60 ·C 6 H 6 , DBTTF·C 60 ·Py and DBTTF·C 70 ·C 6 H 6 , were obtained. The crystal structure of DBTTF·C 60 ·C 6 H 6 was determined. The arrangement of fullerene molecules is approximately simple cubic packing where each C 60 molecule is located in slightly distorted octahedral surrounding. DBTTF molecules have a concave conformation. X-ray photoelectron spectroscopy (XPS) and IR spectroscopy show only weak charge transfer in these compounds. A weak charge transfer band near 900 nm was found in the UV-Vis-NIR absorption spectrum of DBTTF·C 60 ·C 6 H 6 single crystals. DBTTF molecules are coordinated on C 60 ones by π-π and n-π interactions. It was shown that the steric discrepancy between DBTTF and C 60 molecules does not provide favourable conditions for charge transfer in the DBTTF·C 60 ·C 6 H 6 complex.

Ionic fullerene compounds containing negatively charged dimers and coordinatively bound anions

The review summarizes the results of investigations of ionic fullerene compounds containing negatively charged dimers and fullerene anions coordinated to metalloporphyrins. Fullerene radical anions were found to form diamagnetic singly bonded (C60−)2 and (C70−)2 dimers. Dimerization is reversible and leads to paramagnetic—diamagnetic phase transitions or a decrease in the magnetic moment of the complexes. The temperature, at which dissociation of the (C60−)2 dimers begins, varies from 140 to 320 K; the corresponding temperature for the (C70−)2 dimers varies from 260 to 360 K and higher. We prepared the first doubly bonded (C60−)2 dimer. At 300 K, this dimer exists as a biradical. The fullerene radical anions form Co—C coordination bonds with cobalt(II) porphyrinates. The resulting anions are diamagnetic. In some cases, Co—C coordination bonds undergo reversible dissociation, resulting in magnetic transitions from the diamagnetic to the paramagnetic state.

Steric conditions for donor–acceptor interactions in C60 complexes with planar organic donors

Abstract Charge transfer complexes of fullerene C 60 with planar donors of tetrathiafulvalene, dithiadiazafulvalene and pyranylidene family were investigated by IR- and UV-VIS-NIR spectroscopy. The analysis of IR and X-ray data shows that the charge transfer complexes of fullerene with the planar donors are involved in polarization interactions of van der Waals type. Charge transfer is very weak in these compounds and is hindered by unfavourable steric factors. As a result, the CT rate does not correlate with the ionization potential of the donor; the charge transfer absorption bands are very weak too.

C60complexes with dianthracene and triptycene: synthesis and crystal structures

Abstract New molecular complexes of fullerene C 60 with aromatic hydrocarbons TPC·C 60 and DAN·C 60 (C 6 H 6 ) 3 , were obtained. For the first time a three-dimensional packing of fullerene molecules is observed in TPC·C 60 . The DAN·C 60 (C 6 H 6 ) 3 complex has a layered structure with alternating sheets of C 60 and donor molecules. Complexes with strong van der Waals interaction were formed due to the shape concordance between the TPC, DAN and spherical C 60 molecules. XPS spectroscopy of the complexes showed the suppression of π-π * transitions in TPC and DAN phenyl rings in the complexes due to the donor- C 60 interaction.

Synthesis, crystal structure and some properties of charge transfer complex of C60 with asymmetric donor TMDTDM-TTF

Abstract The reaction of C 60 with asymmetric donor tetramethylenedithiodimethyl-tetrathiafulvalene (TMDTDM-TTF) in CS 2 yields the (TMDTDM-TTF) 2 C 60 (CS 2 ) 3 ( I ) molecular complex. The study of the crystal structure of I reveals that it has a layered structure with alternating sheets of C 60 and donor dimers. X-ray photoelectron spectroscopy (XPS) and IR spectroscopy show a weak charge transfer in this compound.

Electronic absorption spectra of the C60 complexes with some organic donors

Abstract Electronic absorption spectroscopy was used to study the electron processes in the complexes of fullerene with organic donors (9,9′-bis- trans -(telluraxanthenyl), tetranitride tetrasulfur, 2,2′,6,6′-tetraphenyldipyranilydene, tetramethylenedithiodimethyl-tetrathiafulvalene and 2,2′-ethanediylidene bis(4,5-ethylenedithio-1,3-dithiole)). Changes in the electronic absorption spectrum of the fullerene have been investigated and discussed for C 60 complexes with organic donors of various molecular structure and electron-donor properties. The charge transfer between electron donor and C 60 has been observed only for the donor molecules having relatively low first oxidation potentials, thus capable of cation-radical formation. The spectral changes were correlated with the donor properties of the organic molecules forming the complexes with the fullerene.

Photoinduced electron transfer in solid C60 donor/acceptor complexes

Light-induced ESR spectroscopy was used to study photoinduced electron transfer (PIET) in the crystals of the C 60 donor/acceptor complexes: TMPD.C 60 (1), LCV.C 60 .C 6 H 5 Cl (2), and (BA) 2 C 60 (3). LESR signals from C 60 with g=1.9984-1.9992 and ΔH=3-6G (100K) for 1-3 as well as the LESR signal from TMPD + for 1 were observed. The LESR signals have two components: a long-lived persistent component and a prompt one, which disappears immediately after light is off. All PIET processes are temperature activated with E a =23, 43 and 49 meV for 2, 3, and 1, respectively. The temperature dependence of spin susceptibility in 1 can be described by the Bonner-Fisher model, while in 2 it corresponds to a paramagnetic behavior of isolated spins.

Optical spectroscopy of C60 complexes

Abstract Complexes of fullerene C 60 with different organic donors have been studied by optical absorption spectroscopy in solutions and in solid state. Charge transfer bands were found for C 60 complexes with tetrathiafulvalenes, pyranylidene and xantenyl in the 600–1300 nm range. It is shown that the energies corresponding to the maxima of charge transfer bands ( hv ct ) for C 60 complexes in solution are almost independent of solvent polarity. The hv CT values for the complexes in solid state are ~0.15–0.20 eV less than in solution. The dependence of the hv CT values on donor ionization potentials (Ip) for C 60 complexes with tetrathiafulvalenes in solid state was found to be hv CT = 0.82 i p –3.93 eV. The lowering of the intensity was observed for the C 60 transitions at 420–540 nm in absorptoin spectra of single crystals of some C 60 complexes obviously due to isolation of C 60 molecules.

Synthesis and some properties of charge transfer complexes of C60 with asymmetric donors of tetrathiafulvalene family

Abstract New charge transfer complexes: (TMDTDM-TTF) 2 C 60 (CS 2 ) 3 , TMDTDM-TTF · C 60 · C 6 H 6 , (EDTTTF) 2 C 60 CS 2 were synthesized by the reaction of C 60 with asymmetric donors in CS 2 and benzene. XPS- and IR-spectroscopy show a weak charge transfer in these compounds. The influence of the solvents during the formation of the complexes was disscussed. The (TMDTDM-TTF) 2 C 60 (CS 2 ) 3 crystal structure reveals that it has a layered structure with alternating sheets of C 60 and donor dimers.

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.