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The 1:1 phenanthrene-tetrachlorophthalic anhydride (P/TCPA) charge-transfer complex crystalizes with monoclinic symmetry, space group P21, with two magnetically inequivalent stacks in the unit cell. The noncentrosymmetric space group is very unusual for CT-complexes. The optical emission spectra at low temperature are characterized by a strong CT phosphorescence and a weak CT fluorescence and delayed fluorescence.

Fluorescence detected ODMR measurements in zero field on the triplet states of light harvest­ing (LH) pigments in chromatophores from Rhodopseudomonas sphaeroides R 26.1 and Rhodo­pseudom onas capsulata A1a+are reported. In both cases at least two distinct triplet states in the antenna system with zfs values of D between 209 and 217 and E between 56 and 67 x 10-4cm-1are observed.

Fluorescence detected ODMR measurements in zero field on the triplet state of the reaction center in whole cells of Rhodopseudomonas viridis, in reaction center solution and in reaction center crystals are reported. In solution and in the crystal a sign reversal of the F-ODMR signals is observed by variation of the wavelength of detection. The signs of the signals are interpreted with the Vredenberg-Duysens relation.

By ODMR in zero-field the porphyrins of the BChl-biosynthesis in whole cells of Rhodopseudomonas sphaeroides R-26 are investigated. In the optical emission spectrum 11 pigments could be identified using ODM R in combination with emission and excitation spectroscopy. The properties of these pigments were analyzed in respect to their interactions with the surrounding molecules. An energy transfer from the triplet state of Zn-protoporphyrin to the antenna pigm ent singlet system was proved by DE-ODMR. The wavelength dependence of the zfs param eters within the individual emission band is explained by a model of selective spin-orbit-coupling. In the case of the precursors chlorophyllide a and pheophorbide a, for example, we could show that the pigments are bound to proteins via a hydrogen bond to the ketocarbonylgroup of ring V and that porphyrins with a central Mg-atom have an additional bond via a Fifth ligand of the Mg

The high temperature behavior of the longitudinal proton spin relaxation time T1of several methyl naphthalene crystals, differing in the arrangement and number of the substituted CH3-groups, was investigated in a large magnetic field range. It could be prooved - for the first time via proton spin relaxation - that in solids the fast reorientation of CH3-groups with low hindering barriers can lead to remarkable contributions to the total relaxation rate by spin-rotational interaction, in addition to the well known dipolar interaction discussed in preceeding works.

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.

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.

Zusammenfassung: Die Erhebung von 29 vitalit�tsrelevanten Merkmalen—teils terrestrisch, teils an Probe�sten—an 51 Wei�tannen (Abies alba Mill.) in Baumh�lzern des Lehrwaldes der ETH Z�rich diente als Grundlage f�r die Ausarbeitung eines einfachen, objektiven Vitalit�tskriteriums (VIT). Mit Hilfe von verschiedenen statistischen Untersuchungen, namentlich einer Hauptkomponenten-analyse, konnte die Zahl der f�r eine ausreichend genaue Bestimmung der Vitalit�t erforderlichen Variablen schrittweise auf sieben und schlie�lich auf drei reduziert werden. Es sind dies die folgenden drei, an der Varianz etwa mit gleichem Gewicht beteiligten Merkmale: Die Anzahl der benadelten Jahrg�nge, der Abflachungswinkel der Krone und die Durchl�ssigkeit der Krone. Sie wurden im Vitalit�tsmodell (VIT 1) additiv verkn�pft. Die Untersuchung der Zusammenh�nge von ertragskundlichen und waldbaulichen Gr��en mit der Vitalit�t haben einen signifikanten negativen Einflu� sowohl des Alters wie auch der Bonit�t auf die Vitalit�t ergeben. Die Kronenl�nge beeinflu�t die Vitalit�t hochsignifikant in positiver Richtung; sie scheint besser als alle momentanen konkurrenzmerkmale den waldbaulichen Werdegang der B�ume und ihre Reaktion auf rechtzeitig, das hei�t in der Jugend erfolgte Pfleggeeingriffe wiederzugeben. Au�erdem scheint sich eine vertikale Strufturierung der Best�nde g�nstig auf die Vitalit�t auszuwirken. Bei �berschreitung bestimmter Reizschwellen f�r die Belastbarkeit der Tanne (etwa durch Immissionen) ver�ndert sich jedoch die Ausgangslage m�glicherweise derart grundlegend, da� die Vitalit�t mit waldbaulichen Ma�nahmen nicht mehr gef�rdert werden kann. Aus den Untersuchungen zum Nadelern�hrungszustand schlie�lich ergaben sich ein positiver Einflu� von K und ein negativer von Ca auf die Vitalit�t, w�hrend die Gehalte an Mg und S keine signifikante Beziehung zeigten.

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%.

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.

Conductivity (dc and ac), ESR-properties and proton relaxation rates of the charge transfer complex Tetrathiafulvalene N,N′-dicyanonaphthoquinonediimine in the temperature range be­ tween 300 K and 3.8 K are reported. This salt belongs to the unusual group of organic conductors, in which segregated donor and acceptor stacks are associated in a pairwise manner. The physical properties, which are compared with TTF-TCNQ, give evidence of non-stoichiometric charge transfer (ρ ≠ 1). A metal like state can be identified for T> 70 K, as is seen from the weak temper­ ature dependence of the conductivity (σrt≈ 30 Scm-1) and the susceptibility (Xrt≈ 7.5 ⋅ 10-4emu/ mole) and from the Korringa like temperature dependence of the proton relaxation rates. The drop of the susceptibility at Tc≈ 70 K and the activated temperature dependence of the conductivity for T < 70 K are explained by a metal-to-semiconductor transition.

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.

In continuation of earlier works (temperature range 400 - 77 K) the temperature and frequency dependencies of the longitudinal relaxation time T1in different methyl naphthalene crystals were measured down to 4,2 K at 22 and 56 MHz. The observation of two minima in some cases below 50 K could be attributed quantitatively to the weakly hindered β-CH3groups (EA<0,8 kcal/mole) by comparison of the results of similar methyl naphthalenes. The low relaxation rate in the minima is due to tunneling effects of the methyl groups. The splitting of the lowest torsional niveau could be roughly determined.