17557-11-8Relevant articles and documents
Photoelectron spectra and molecular properties. CXXXVIII. 1,4-Dibenzene: synthesis, structural analogy, photoelectron spectrum and ESR/ENDOR cheracterization of its radical anion
Bock, Hans,Meuret, Jochen,Baur, Ruediger,Ruppert, Klaus
, p. 113 - 122 (1993)
1,4-Dibenzene 3SiC6H4Si3, which contains eight silicon centers, has been synthesized and some of its molecular properties determined.For a single crystal structure determination, its isovalence-electronic and sterically more crowded carbon analogue, 3CC6H4C3, was selected.It shows van der Waals interactions due ro close lattice packing.Despite its shorther SiC bonds, however, no severe skeletal distortions due to overcrowding are observed; the contraction of the benzene ipso angles to 114 deg is due to the donor effect of the tris(trimethylsilyl)methyl substituents.The first vertical ionization energy of the title molecule, IEv1 = 7.37 eV, is the lowest of all of these recorded up to now for 1,4-dialkyl or 1,4-disilyl substituted benzene derivatives; for the monosubstituted tris(trimethylsilyl)silyl derivative 3SiC6H5 the value is 8.04 eV.Cyclovoltammetric experiments in aprotic solution reveal a velocity-dependent irreversible oxidation above + 1.28 eV and no electron insertion within the measurement range to -2.9 eV.The reduction to the radical anion, however, can be achieved in THF solution containing cryptand at a potassium metal mirror.According to the spin populations deduced from 1H and 29Si ENDOR signal patterns, more than half of the spin is located in the two 3Si groups.Results of molecular orbital (MO) calculations and comparison with equivalent molecular states of chemically related compounds allow rationalization of the effects of the 3Si substituent, which acts as a strong electron doenor in radical cations and as a strong electron acceptor in radical anions.
