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The electronic structure of crystalline needles of the 2,5-Dimethyl substituted (DCNQI)2M (M = Cu, Rb, Cs) radical-anion salts, prepared in situ, is determined by photoelectrons spectroscopy using synchrotron radiation. The electronic structure at the top of the valence bands is determined to arise mainly from contributions of C2p and N2p states. In particular, the Cu3d atomic levels do not contribute significantly to the density of states next to the Fermi energy. This comparison of salts with different central atoms gives the first experimental evidence of a truely organic metal with the uppermost (conducting) band originating from C2p and N2p derived states.

4,5;4′,5′-Bis(1,4-oxathiane-2,3-diyldithio)tetrathiafulval ene7 (TOET) is synthesised in four steps from 1,4-oxathiane. Compound 7 shows two reversible redox couples at 0.56 and 0.90 V vs. SCE. Analysis of NMR spectra combined with energy minimisation calculations indicated that at least three isomers of TOET should be present in solution. TOET forms a charge-transfer complex with TCNQ which shows a conductivity of 3×10-3 S cm-1 .

The unit cell of (QP)4(SbF6)3 shows triads of QP in an arene stack and one QP in the anion sheet. The sum formula is therefore (QP)3QP(SbF6)3. Electron-electron repulsion force le-/site resulting in a semi-conducting state. This is in agreement with an activated conductivity of max 10-1 Scm-1 at 300 K.Magnitude and activation energy of the paramagnetic susceptibility do not coincide with those of the conductivity; spins and charges are localized and decoupled due to the strong alternation of distances within the cation stack. Spin diffusion along the stacks governs, at least above 180 K, the magnetic properties: narrow ESR-lines and proton spin relaxation via hyperfine interaction with the relaxation dispersion T-11H α ω-1/2 above 200 K.A lower value for the intrachain exchange rate τ1-1> 8.1011 sec-1 and a lower limit of 103 for the anisotropy can be evaluated.Keywords: quaterphenylene, molecular crystal, radical cation salt, low dimensionality, magnetic resonance

N,N'-Dicyanoquinonediimines (DCNQIs) with various substituents can favourably replace TCNQ. They act as acceptors in CT-complexes with TTF which have high conductivity and as anion radicals in salts with Cu+, Ag+ and Li+ which have very high conductivity.

Conducting radicalcation salts (res) containing pyrene exhibit a pronounced polymorphism in crystal-structure and composition due to the high symmetry of the hydrocarbon. On this basis we associate the doublet structure of the ESR-signal in Pyrene-12 (SbF6) 7 with microclusters, alternating in the pyrene stack, which are turned to each other by exactly 90° around the stacking direction.

ESR- and DC-conductivity measurements on (Naphthalene)2 AsF6 show in metallic properties above 240 K with the narrowest ESR-line (ΔBpp = 2,5 mG) found so far in solids. Below 240 K we have a semiconductor and at about 110 K a structural phase transition which leads to an enhancement of the ESR-linewidth by one order of magnitude.

In (fluoranthenyl)2+ XF 6- salts (X = P, As, Sb) the temperature dependent proton relaxation rates are due to three processes, namely the interaction with (i) mobile paramagnetic species (above 160 K), with (ii) fluorine nuclei linked to the anions (between 160 and 40 K) and with (iii) fixed paramagnetic centers (below 40 K). Inserting As or Sb for P, the center atom of the anion, leaves the high temperature properties of the crystals unchanged but results in higher hindering potentials for the reorientational motion of the anions and in a shift of the phase transitions to lower temperatures.

Esr and zero-field Odmr measurements were performed for charge-transfer single crystals of hexamethylbenzene (HMB) with tetracyanobenzene (TCNB) and of HMB with tetrachlorophthalic anhydride (TCPA). Both systems exhibit very high ionic (charge-transfer) character of the triplet excitation as deduced from the small S1,-T1 separation and small fine structure parameters of |D| = |0.0285.|E| = 0.0066 cm I (HMB-TCNB) and |D| = 0.01525, |E| = 0.00342 cm-1 (HMB-TCPA). By comparison with the respective parameters of the neutrally excited acceptors a charge-transfer character is determined as e2CT = 90% and 100%, respectively. Delocalized states (triplet excitons) are detected in HMB-TCNB in a narrow temperature range (∼ 140 K).

Mobile triplet excitons in A/TCPA have been detected from 1.2 to 300 K via ESR and zero-field ODMR. Their features such as linewidth and zero-field-splitting (zfs) parameters are discussed in terms of the temperature-dependent crystal structure. Between 1.2 and 4.2 K the excitons are caged by barriers. When raising the temperature a thermally activated hopping takes place between two triplet bands separated by 40 cm−1, having different zfs parameters | DA| = 2126.5, |EA| = 241.0, | DB| = 2112.5, | EB| = 238.0 MHz and different zfs tensor orientations. Above 100 K an increase of the librations of the anthracene molecules broadens the homogeneous excitonic lines. The homogeneous linewidth is measured by the free induction decay. The CT character of the triplet state is estimated as c2CT<̳4%.

New acceptors of the DCNQI-type were synthesized, in which two acceptor units are connected by a tethering chain of different length. From these dimers both conducting radical anion salts (cation Cu+) and charge-transfer complexes (donor TTF) were obtained, which are compared with their monomeric counterparts, especially with respect to stochiometry and conductivity.

A method is described for the direct measurement of spin-lattice relaxation rates between the triplet spin sublevels of phosphorescent molecules. The method also yields the correct values (in the presence of spin-lattice relaxation) for the total sublevel decay rates and can be used in conjunction with standard optically detected magnetic resonance experiments to find correct values for relative populating rate constants, radiative rate constants and steady state populations of the triplet sublevels. The technique is applied herein to the study of indole and tryptophan molecules in several environments.

Multi-component conductivity changes in metallic radical ion salt films are induced by optical excitation. First experiments on polycrystalline films of the 2, 5-dimethyl-dicyanoquinonediimine copper salt, (DMe-DCNQI)2Cu and the corresponding low-dimensional chloro-methyl and bromo-methyl salts, (ClMe-DCNQI)2Cu and (BrMe-DCNQI)2Cu, respectively, are presented. The time response of the conductivity consists of three components. These are interpreted a) by a possible contribution of higher conduction bands which might explain the fast response (τ<5 ns), b) by detrapping of charge carriers (τ>40 ns), and c) by a temperature effect (τ≈1 ms). In single crystals, the fast response is also detected, while the other contributions are less pronounced.

The three step synthesis of 2,3,6,7-Tetrakis(methylthio)naphthalene (TMTN) 1is described. The title donor gives a 1:1 salt with hexafluoroarsenate anion. The crystal structure consists of a dimerized donor stack, with alternate stacking. The conductivity is activated, room temperature conductivity; ≈10−3·10−4Scm−1. The susceptibility is quite low, χ(300K) = 7·10−7emu/mol, and the ESR linewidth is ΔBpp(300K)≈5 G.

The longitudinal proton relaxation time T1in methyl naphthalene crystals, differing in the arrangement and number of the substituted CH3groups, was measured as a function of the temperature above 77 °K and the magnetic field between 0.9 and 20 kOe. The results can be described by hindered rotation of the methyl groups with the jumping times and activation energies strongly dependent on the group arrangement. In the β-position the rotational barrier of 0.8 kcal/mol is predominantly determined by the infermolecular interaction, whereas in the case of the a-position and for adjacent CH3’s the hindering potential of 2.4 kcal/mol arises largely from the intramolecular term.