Jost Ulrich von Schütz

First detection of the (nonphosphorescent) triplet state in single crystals of β-carotene

Abstract Time resolved ESR on the photoexcited triplet state of β-carotene single crystals have allowed the first correlation of the fine structure tensor with the molecular axes system. Both roughly coincides within 20°. The fine structure parameters are D = 0.0331 cm−1 and E = 0.0040 cm−1.

2,5‐Disubstituted N,N′‐Dicyanobenzoquinonediimines (DCNQIs): Charge‐Transfer Complexes and Radical‐Anion Salts and Copper Salts with Ligand Alloys: Syntheses, Structures and Conductivities

The new members of the series of 2,5-disubstituted DCNQIs, 1d (Cl/OMe), 1e (Br/OMe), 1j (Cl/I), 1k (Br/I), 1l (I/I), form conducting charge-transfer complexes with TTF (tetrathiofulvalene) which are comparable to known DCNQI/TTFs. From these DCNQIs highly conducting radical-anion salts [2-X, 5-Y-DCNQI]2M (M = Li, Na, K, NH4, Tl, Rb, Ag, Cu) can also be prepared either from the DCNQIs and MI (not AgI), on a metal wire (Ag, Cu), or by electrocrystallization (M = Tl, Ag,Cu). For better crystals a method using periodical switching between reduction and partial oxidation has been developed. With CF3 (large, strongly electron-attracting) as the substituent in DCNQIs 1m (OMe/CF3) and 1n (Me/CF3), conducting TTF complexes remain whereas only 1n yields an insulating copper salt. DCNQI–Cu salts with high conductivities are obtained with alloys containing two or three different DCNQIs. The temperature-dependent conductivities of DCNQI–M salts (other than copper) are similar to those of metal-like semiconductors. All new DCNQI–Cu salts are metallic [M] down to low temperatures, except [1d (Cl/OMe)]2Cu which undergoes a sharp phase transition to an insulating state[M I]. By variation of the ligands or their ratios in conducting alloys of DCNQI–Cu salts temperature-dependent conductivities can be tuned from M I to M. In addition, alloying three ligands produced for the first time a radical salt with temperature-independent conductivity from 5 to 300 K. Most remarkably, alloys of the type [(2,5-Me2DCNQI)m] Cu/[{2,5-(CD3)2-DCNQI}n]2Cu which exhibit a sharp M I phase transition on further cooling reenter the conducting state by an I M transition, with changes of ca. 108 Scm−1 both ways. For the first time in the field of organic metals crystal structures of DCNQI–copper salts have been determined by X-ray powder diffraction methods and refined by Rietveld analysis. Unit cell data, coordination angles and distances of the π planes are in excellent agreement with the single-crystal X-ray data. However, bond lengths and angles of the ligands are to be less accurate. This powder method proves to be most valuable if only microcrystalline material is available.

25th Congress Ampere on Magnetic Resonance and Related Phenomena

This volume contains extended abstracts of the 10 plenary lectures, 27 invited symposium lectures and ap- proximately 300 contributed papers that were presented at the 25th Congress Ampere. The contributions cover the full range of magnetic resonance and radiospectroscopy and their applications in physics, chemical physics, medicine and biology. Advanced NMR and ESR techniques are treated, as are their applications to novel materials.

Mott–Peierls phase in deuterated copper-DCNQI systems: a comprehensive study of longitudinal and transverse conductivity and ageing effects

Transport and low-frequency optical reflection measurements (180– 380 GHz) are reported for the quasi-three-dimensional conducting alloy Cu[(2,5(CH3)2–DCNQI)0.70(2,5(CD3)2–DCNQI)0.30]2 between room temperature and 35 K. The optical properties of the system are strongly anisotropic. It is metallic down to 60 K where a Mott–Peierls phase transition occurs. While the transverse conductivity remains practically unchanged, the longitudinal conductivity abruptly drops at the phase transition. Comparing our latest results with previous dc data and measurements of the microwave conductivity also reported here, we find indications of an ageing effect in these samples.