Ivan S. Neretin

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.

Symmetry of van der Waals molecular shape and melting points of organic compounds

Long-known empirical regularities in melting points (mp) among molecular crystals of organic compounds with a closely related stoichiometry are dictated by a short-range molecular van der Waals term in their crystal field. This term, which acts as a symmetry-breaking perturbation on the averaged intermolecular interactions, is determined by the “contact” potential in the vicinity of molecules, i.e. by the shape of their van der Waals surface. To reflect the topology of the crystal field, an approximate van der Waals group Ğ of the average local field acting on a molecule and asymmetryas of the molecular surface composed of atomic van der Waals spheres, as its total misfit to Ğ, were introduced. The scheme was applied to organic compounds whose molecules have a mirror symmetry plane; the shape of two-dimensional sections of their van der Waals surfaces by this plane was analysed. Calculated values of molecular asymmetry parallel as yet uninterpreted trends in melting point data such as oscillations between “even” and “odd” n-alkanes CnH2n+2, reduced melting temperatures of monosubstituted derivatives with highly-symmetric molecular cores (e.g. toluene), and non-trivial mp orders among the isomers of disubstituted ethylenes C2H2X2rntttt(“gem-<cis-<trans-”), substituted benzenes C6H4X2rntttt(“meta-<ortho-<para-”), C6H3X3rntttt(“1,2,4-<1,2,3-<1,3,5-”), C6H2X4rntttt(“1,2,3,5-<1,2,3,4-<1,2,4,5-”), and disubstituted naphthalenes. The observed mp trends do not display any notable correlation with molecular moments of mass and charge distribution, thus being dictated mostly by van der Waals forces.

Ionic multi-component complexes containing TDAE˙+ and C60˙− radical ions and neutral D1 molecules: D1·TDAE·C60

New ionic complexes containing TDAE˙+ and C60˙− radical ions and neutral molecules: (TBPDA)2·TDAE·C60 n(1); CTV·TDAE·C60 n(2); and CoIITPP·TDAE·C60 n(3) n(TDAE: tetrakis(dimethylamino)ethylene; TBPDA: N,N,N′,N′-tetrabenzyl-p-phenylenediamine; CTV: cyclotriveratrylene and CoIITPP: tetraphenylporphyrinate cobalt (II)) were obtained as single crystals. The presence of TDAE˙+, C60˙− and neutral donors in 1–3 was proved by optical absorption spectra in the IR and UV-vis-NIR ranges. In the crystal structure of 1 studied by single crystal X-ray diffraction, TDAE˙+ and C60˙− are spatially separated by bulky TBPDA molecules. Magnetic susceptibilities of 1 and 2 follow the Curie–Weiss law with the negative Weiss temperatures (−2.3 and −2.0 K) and their magnetic moments decrease below 60 and 15 K, respectively. The EPR signals from 1 and 2 at the same temperatures are split into two components, which shift in the opposite directions to lower and higher fields with the temperature decrease. This phenomenon is explained by the formation of field-induced short-range magnetically ordered clusters. CoIITPP and C60˙− form diamagnetic σ-bonded (CoIITPP·C60−) anions in 3 in the 1.9–190 K range. This allows one to observe the EPR signal from the isolated TDAE˙+ radical cations (g = 2.0031 and halfwidth = nΔH n= 3.22 mT at 4 K). Above 190 K the magnetic moment of 3 increases and the EPR signal is essentially broadened and shifted to a lager g-factor (g = 2.0194, ΔH n= 24.2 mT at 290 K). This is attributed to the dissociation of the σ-bonded diamagnetic (CoIITPP·C60−) anions to non-bonded paramagnetic CoIITPP and C60˙− components.

Synthesis and crystal structures of new C60 complexes with asymmetric tetrathiafulvalenes

Abstract New charge transfer complexes of fullerene C 60 with two types of tetrathiafulvalenes: bis(4,5-dihydronaphtho[1,2- d ])-tetrathiafulvalene (BDHN-TTF(C 60 ) 2 C 7 H 8 , 1 ) and three bis(alkylthio)ethylenedithio-tetrathiafulvalenes (C n TET-TTF(C 60 ) x , where x =2, n =2 ( 2 ); x =1.5, n =4 ( 3 ); x =3, n =7 ( 4 )) were obtained. Compounds 1 and 2 were studied by single crystal X-ray diffraction. In both crystal structures, the three-dimensional (3D) packing of fullerene molecules formed by waved dense hexagonal layers was revealed. The donor molecules arranged in the fullerene framework attain bent conformation to fit to the spherical fullerene surface. Intermolecular contacts have typical van der Waals lengths. According to optical data, the complexes obtained have a neutral ground state with the charge transfer bands at 11×10 3 xa0cm −1 .

Transition metal dicarbollide complexes: synthesis, molecular, crystal and electronic structures of [M(C2B9H11)(NMe2)3] (M = Nb or Ta) and their insertion reactions with CO2 and CS2†

The homoleptic amides [M(NMe2)5] (Mxa0=xa0Nb 1 or Ta 2; the latter is characterised by a structural study) reacted with the carborane nido-C2B9H13 to eliminate two equivalents of HNMe2 and generate the dicarbollide half-sandwich tris(dimethylamide) complexes [M(C2B9H11)(NMe2)3] (Mxa0=xa0Nb 3 or Ta 4). The crystal structures of isomorphous 3 and 4 have been determined and reveal two NMe2 ligands in a vertical orientation and the third one in a horizontal orientation with respect to the η5-co-ordinated face of the C2B9H11 ligand. The electronic factors responsible for the amide ligand orientations in these complexes are explored using qualitative MO arguments. Complexes 3 and 4 reacted with CO2 and CS2 to yield the tris(carbamate) [M(C2B9H11)(O2CNMe2)3] (Mxa0=xa0Nb 5 or Ta 7) and tris(dithiocarbamate) [M(C2B9H11)(S2CNMe2)3] (Mxa0=xa0Nb 6 or Ta 8) complexes, respectively. The crystal structures of 6 and 7 show two (dithio)carbamate ligands in horizontal and one in vertical orientation, demonstrating the similarity between the σ,π-donor frontier orbitals of the ligands NMe2 and X2CNMe2 in 4 and 6 or 7 respectively.